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DynaChem Pressure Vessel Use of the

1. 6 88 e Chapter 8 TIME SPECIFICATION TMIN V Pipe minimum temperature Time Increment Primary Keyword TIME TINC V Time increment Unit Equilibrium Computation Primary Keyword UNIT A Guide to Using DynaChem NOEQ Do not compute equilibrium after specified time conserve mass and energy estimate temperature pH etc NOVAP Do not allow vapor after specified time 7 Output Primary Keyword PRINT NOTERM No output to Terminal OUTPUT v Output file DOU frequency SUMMARY v Summary file SUM frequency TERM Output to Terminal TRACE v Trace file OUE frequency 8 Output to Restart File Primary Keyword SAVE FREQUENCY v Frequency of saving Restart ROU file A Guide to Using DynaChem Chapter 8 TIME SPECIFICATION e 89 Chapter 9 PRINT SPECIFICATION The PRINT Keyword is used to specify the frequency of printing Output Summary and Trace files to the Disk Frequency is in terms of number of time increments The standard Terminal output TRACE is very brief merely printing the current accumulated time If however that is to be suppressed as well NOTERM may be used The Interactive capabilities of DynaChem are invoked using the INTERACTIVE Specification This automatically suppresses all normal terminal output and shifts the User into the screen driven Interactive process Virtually all operating and Specification parameters may be changed dynamically while in the Interactive mode PRINT Specifications Opt
2. i VALV2 XH q UNIT2 TANK Stage 2 UNITI TANK Stage 1 The two inputs to the Multicascade Controller will be factored as follows Time 0 to 0 1 hour CLOO1 Output Factor 8 CLOO 2 Output Factor 2 Time 0 1 to end CLOO1 Output Factor 5 CLOO2 Output Factor 5 Thus initially the upstream stage UNIT1 will dominate the control in Stage 2 This will reduce startup fluctuations seen in Stage 2 by predicting them After the initial startup period of 0 1 hour each controller will contribute half of the Valve Stem Movement in Stage 2 In this case the factors add to unity which is not necessary CLOO1 VID 1 CLID 3 SPUNIT L SPID PH SPVAL 3 KC 0 01 TAUI 0 5 CFACTOR 0 8 CFACTOR 0 5 TIME 0 1 CLOO2 CLID 3 SPUNrr 2 SPID PH SPVAL 9 CFACTOR 0 2 CFACTOR 0 5 TIME 0 1 CLOO3 VID 2 MULTICASCADE VALV1 DNODE 2 CV 20 VALV2 DNODE 4 CV 30 A Guide to Using DynaChem Chapter 5 CONTROL LOOP SPECIFICATION e 69 TRIM ALGORITHM The Trim algorithm revises the Setpoint value s of another controller based upon the Stem Position of the valve The Trim Controller 1 Is supplied to the Stem Position of a valve by the Controller which controls the valve 2 Compares the Stem Position to the specified Trim limits 3 Computes a Factor based upon the comparison made in step 2 4 Applies the computed Factor to the Setpoint value s of a specified Control Loop Schematic Measured Trim Variable Con
3. 1 0 CLOO2 VID 10 VELO SPUN 3 SPID PRES SPVA 3 0 TIME 0 TAUI 1 0 KC 0 2 TIME 0 The Control loop will adjust the Stem position on VALVIO to result in a pressure of 3 atm in the TANK A Guide to Using DynaChem Chapter 12 DynaChem Pressure Vessel e 99 Example of a Single DynaChem Pressure Vessel The above Pressure Vessel was initiated with 135 m of H2O with a small amount of dissolved CO 0 1 molar A stream is fed to the vessel at a rate of 120 m hr The composition of the feed in molar percent is H50 98 4 molar HNO3 1 24 H280 0 18 NANO 0 018 NA2CO3 0 007 CO 0 18 The result is a relatively slow evolution of vapor which is predominately CO and H2O With the downstream pressure of 1 0 atm and the Stem position permanently set to 1 0 the vessel builds up pressure from Time 0 0 until it reaches the downstream pressure at Time 0 48 hour At that time the pressure continues to increase above the downstream pressure and vapor begins to flow 2 6 2 4 2 2 Pressure Vessel Vessel Pressure No Control N Pressure atm o Time hr The pressure in the vessel begins to level off and come to steady state when the pressure in the vessel is sufficient to result in equilibration of the flow out through the valve and the vapor evolved from the solution in the tank In this case the steady state pressure is 2 57 atm and has essentially reached that point after 6 hours Thus with
4. 2 The Control Loop containing the Trim Controller Control Loop j CLOOj CLID k TRIM s1 s2 KC v 3 The Control Loop whose Setpoint is to be adjusted Control Loop k CLOOk SPVAL v The Stem Position of Valve n is used as the Measured Variable in the Trim Controller CLOO The ERROR is computed based upon the Trim Limits s1 s2 If Stem Position lt s1 then ERROR Stem s1 If s1 lt Stem Position lt s2 then ERROR 0 If s2 lt Stem Position then ERROR Stem s2 The computed Factor is Factor 1 0 ERROR KC The Factor is then multiplied times the Setpoint Value s of the Control Loop to be adjusted CLOOk Furthermore the Factor is applied to the following values as well 1 Both low and high Setpoints for Deadband Control 2 Both Open and Close values for Switch 3 Ratio value for Ratio Control Notice that when Stem lt s1 the ERROR is negative and when Stem gt s2 the ERROR is positive The sign of the Gain KC should be chosen appropriately For example suppose you want to decrease the setpoint of CLOOk when Valve n is closed and therefore less than sl The functional representation of STEM versus Factor is shown below In order to achieve this result KC should be positive A Guide to Using DynaChem Chapter 5 CONTROL LOOP SPECIFICATION e 71 Factor Slope Gain 1 0 sl s2 Stem Position Application 1 In the Two Stage Neutralization shown below it is desired to decrease the Setpoint in Sta
5. 727881 1225 17 059 120 0 128 0 135 4 139 7 141 1 FraChem DynaChem 45198 41175 7506 727886 1225 17 048 120 0 128 0 135 4 139 7 141 1 Case 1A Five Stage Ammonia Stripper Control Bottoms Composition Column Description Same as Example Case 1 except for Control Loop Control Loop Description Control Loop 1 A Guide to Using DynaChem Control Valve 13 Algorithm VELO Setpoint Value2 00E 03 Value Type COMP Setpoint Unit ID 1 Chapter 13 CASE STUDIIES e 111 Controller Gain 400 Integral Time 0 5 Species NH3 Units MOLF N4ole Fraction Phase LIQ Case 2 Two Stage Neutralization Operating Conditions Continuous Feed Temperature 30 C Pressure 1 atm Total Flow 25 m hr H20 55 51 relative NANO3 0 01 H2S04 0 1 HNO3 0 7 NA2CO 30 004 Intermittent Feed Begin Time 0 5 hr Duration 0 25 Begin Time 1 0 hr Duration 0 75 Begin Time 2 25 hr Duration 0 5 Temperature 270 C Pressure 1 atm Total Flow 40 m hr H20 55 51 relative H2S04 1 25 HNO3 0 15 NA2S04 0 009 Buildup Feed Begin Time 0 1 hr Ramp Time 0 35 hr Duration Continuous Temperature 260 C 112 e Chapter 13 CASE STUDIIES A Guide to Using DynaChem Pressure 1 atm Total Flow 10 m hr H20 55 51 relative NANO3 0 014 HNO3 0 002 NA2CO3 0 502 Caustic Feed 20 wt Temperature 250 C Pressure 1 atm Total Flow 10 m hr H20 0 8988 NAOH 0 1012 Caustic Feed 1 w
6. A Guide to Using DynaChem Chapter 10 SAVE SPECIFICATION e 93 UNIT LOGNODE n2 DNODE m2 The values nl n2 are not actually Node ID Numbers in this execution therefore they may be used elsewhere as Node Numbers For example it is legal but not necessary for ml n1 m2 n2 which makes translation from the first to the second execution easier The LOGNODE capability allows the user to separate the process into sections Each section may then be isolated and analyzed saving significant execution time For example the feed streams of a neutralization process may be analyzed and the level control loop tuned resulting in a single feed stream to the first Neutralization Stage The first Stage may then be isolated and tuned without recalculating the feed section or computing the second Neutralization Stage The resulting output stream from the first Stage may then be used as a simple feed stream to the second Stage eliminating the need to recompute the Feed and first Stage repetitively while tuning the second Stage 94 e Chapter 10 SAVE SPECIFICATION A Guide to Using DynaChem Chapter 11 RESTART SPECIFICATION RESTART has no associated Specification Keywords When RESTART is invoked the stored values for the Keywords TRME NODE UNIT VALVE and CLOOP are retrieved from the Restart Input RIN file along with the final conditions of all Units and Nodes at the last time stored Therefore entries for these Keywords are unnecessary
7. CLOSE the controller output is set to 0 0 When Measured Value Open Value then Controller Output 1 When Measured Value Close Value then Controller Output 0 When the output destination is a Valve VID the output is applied as a Valve Stem Position When the output destination is a Pump PID the output is applied as the Pump Speed Override Fraction of Maximum Pump Speed Application A Supply Tank exit is being used to meter fluid into another process unit in a continuous mode The Supply Tank is refilled by the Supply Stream whenever necessary to maintain a minimum level of 0 5 meter The Switch algorithm may be used in a feedback controller to fill the Supply Tank as needed For simplicity the upstream Supply Stream source an ENTRY or a TANK and the downstream destination of the metered fluid a TANK will be omitted 64 e Chapter 5 CONTROL LOOP SPECIFICATION A Guide to Using DynaChem Supply Stream VALV2 The Supply Tank UNIT1 will be replenished by the Supply Stream Node 1 when the level reaches 0 5 m The Supply Tank will be refilled to a level of 4 m and the Supply Stream valve VALV1 will be closed until the level reaches 0 5 m again Assuming the Supply Tank is empty initially the Supply Stream must be started manually VOPEN 1 The exit line will be closed initially until sufficient fluid has been supplied to the tank The DynaChem Input is as follows VALV2 DNODE 2 CV 10 VALVI DNODE 1 CV 100 VOPEN 1 C
8. Loop producing the Output Multicascade Algorithm Definition Stem Movement at time j Stem Stem Fraction Open at time j Stem Fraction Open at time j 1 Note Stem may not result in a Stem Position less than 0 or greater than 1 Stem Factor 1 Stem 1 Factor 2 Stem 2 Factor 3 Stem 3 Factor 4 Stem 4 Factor 5 Stem 5 where Stem Stem Movement at time j from Multicascade Controller Stem 1 Stem Movement at time j from Control Loop i Factor 1 Output Factor from Control Loop I Application 1 A two stage neutralization process will use a Multicascade Controller to provide the 2nd stage with feedforward assistance from Stage 1 A pH Control Loop CLOO1 will measure the pH in Stage 1 UNITI and control the pH in that stage at 3 using Valve 1 The Output from that Loop will also be sent to the Multicascade Control Loop CLOO3 The other input to the Multicascade Control Loop will be from a pH Control Loop CLOO2 on Stage 2 UNIT with a pH setpoint of 9 This pH Control Loop however will send output to the Multicascade Control Loop only The valve controlling the reagent flow to Stage 2 VALV2 will be controlled not by the pH Control Loop but by the Multicascade Controller CLOO3 Thus as an upset requires additional reagent in Stage 1 this information will feed forward to Stage 2 in anticipation of the upset 68 e Chapter 5 CONTROL LOOP SPECIFICATION A Guide to Using DynaChem VALVI VW q
9. STATE 20 1 20 1 UNIT3 TANK UNODE 2 5 DNODE 6 LEXIT 4 NEUTRALIZATION TANK CSA 3 14 MAXLEVEL 4 STATE 20 1 5 5 1 UNIT4 ENTRY DNODE 5 REAGENT FEED 14 e Chapter 2 Building a DynaChem Case A Guide to Using DynaChem STATE 20 1 5 0 8988 0 0 0 1012 UNIT 4 ENTRY Reagent UNIT 1 ENTRY Process Feed ENTRY Neutralization Tank Valve and Control Loop Definition Now valves and control loops should be added to achieve the desired process operation For simplicity the valves and control loops will be described in the same order as the Units were described The exit from Unit 1 Node 1 does not need a valve This is a Process Feed which must flow to the Surge Tank The exits from Unit 2 Nodes 2 and 3 must be controlled however with the following objectives 1 Maintain the Surge Tank level within acceptable limits 2 Dampen the flow and composition fluctuations to the Neutralization Tank resulting from the intermittent Process Feed Stream The fluctuations in this example are not as significant as they are in many neutralization cases in which many streams of different total flow and chemical makeup flow into the Surge Tank On the lower exit Node 2 at a level of 0 25 m a valve and deadband level controller will be used to achieve both of these objectives but primarily objective 2 A valve and level controller on the higher exit Node 3 will be used as an emergency overflow to complete objective 1 First
10. 23 Entry Applications argo ione e iii eo a a 24 TANK UN ria a a ed LARIO ae 29 Application Ti ilo ia 31 Application 2 ini lee aaa 32 Application Saasen eci LE LIL Lana 33 Application A ani oi eli labii ana 34 IAN BJ eI TEIS a Eo E inonda 35 PERE WIND DESE E EE E E E E E Gttenebaieness 36 Application IT aane anran ele io ea Ea E r 40 Apphcation 2ji o ila r a r rari inno 42 Application 3 salino N E r E ER A aa A a E R Ea rE N 44 Application Aani a E aa a aar a aa Maha musteteeen Se 45 Applcatlon9 a siinr lie i E R Ea es 45 Chapter 4 VALVE SPECIFICATION 47 Chapter 5 CONTROL LOOP SPECIFICATION 49 A Guide to Using DynaChem Contents e i ii e Contents VELOCITY ALGORTHM ic green iaia SI Velocity Algorithm Definition i 54 Applicaton lisi ibi ei anioni 54 Application 2a init DSi 56 Application 33 fio EE i Rial eee wate 57 POSIFIONAL Algorith iti s pati SCENE al ali alia lola 57 Positional Algorithm Definition ii 59 Application lata aliena liano ine 60 Application 2 sspsssnsogio lana e alain lan 61 SWITCH ALGORITHM prenen iona Ea E ola ela gsnaasnion te 62 Switch Algorithm Definition ui 64 Application Deis usata attira ARA 64 Application Zeini annn ea a Ee EEE E A tamination ao anna 66 MULTICASCA DE ALGORITHM eerta a aara RAEE E E AE E ones 66 Multicascade Algorithm Definition i 68 Applicationi i iaina ala Hale Legione lalla ola 68 TRIM A
11. 5 REAGENT FEED STATE 10 1 5 0 8988 0 0 0 1012 VALVI DNODE 2 CV 40 VALV2 DNODE 3 CV 50 VALV3 DNODE 5 CV 10 CLOO1 VID 1 POSITIONAL SPUNIT 2 SPID LEVEL SPVAL 1 3 KC 0 2 VCONSTANT 0 35 CLOO2 VID 2 SPUNIT 2 SPID LEVEL SPVAL 4 5 KC 0 5 CLOO3 VID 3 SPUNIT 3 SPID PH SPVAL 9 KC 0 01 TAUI 1 Time and Node Order Definition To complete the basic definition of the model the Time Parameters and Node Order must be specified The simulation will be for 1 hour TEND l at time increments of 0 01 hour TINC 0 01 TIME TEND 1 TINC 0 01 The objective of DynaChem is to represent an analog process with a digital and therefore discrete model The time increment is the means of placing the discrete characteristics The smaller the time increment the closer the discrete model approaches the analog process The smaller the time increment however the greater the computer time necessary to simulate a given time period Thus a compromise between minimizing the departure from analog characteristics and realistic computer execution time is necessary In this case the time increment was selected by trial and error The time increment was decreased until no significant difference was observed in the System response Specification of Node Order determines the order in which all computations are completed Specification of a Node results in the computation of the following 1 The Unit directly upstream from the Node i e the Unit for which the N
12. 8 is an Energy Node ENODE Energy Nodes are also discussed in the Pipe Unit Section Application 3 A distillation column tray may also be modeled with a Tank Unit Consider a tray 1 m in diameter cross section area 0 785 m with an overflow baffle which is 0 15 m Two streams one liquid and one vapor enter the tray and two streams one liquid and one vapor exit the tray Liquid Vapor Inlet Outlet Stream Stream 0 15 m Liquid Outlet Stream Vapor Inlet Stream The Liquid Outlet Stream Node 10 will be placed at a level of 0 15 m with no valve All fluid above that level will exit i e overflow The Vapor Outlet Stream Node 2 may be placed at any level greater than or equal to 0 15 m to assure the departure of the vapor Thus once the tray fills it will remain filled just enough fluid leaving each time increment to maintain the fluid level at 0 15 m Meanwhile all of the vapor evolved exits A Guide to Using DynaChem Chapter 3 Unit Specification e 33 The tray is described as Unit 3 with the following DynaChem Input UNIT3 TANK UNODE 1 9 DNODE 10 2 LEXIT 0 15 2 CSA 0 785 MAXLEVEL 2 The maximum level has been set at 0 2 m As long as the maximum level is above the overflow exit level its only purpose is to assure a vapor exit since the level can never go above the overflow exit level of 0 15 m A distillation column may then be modeled by including several of these in series In most cases the inl
13. CLOO2 VID 2 SPUNIT 2 SPID LEVEL SPVAL 4 5 KC 0 5 The first line SAVE LOGNODE 2 results in a Node Output file in which all state information describing Node 2 is saved for all time steps At the conclusion of the execution the Node Output file should be transferred to the Node Input file for the next execution In most DynaChem versions this may be done when exiting the Execution Procedure Once the Node Input file is acquired from execution of the first part above the second part may be executed with the following TIME TEND 1 0 TINC 0 01 NODE ORDER 2 6 5 PRINT OUTPUT 10 SUMMARY 1 UNIT2 ENIRY DNODE 2 LOGNODE 2 A Guide to Using DynaChem Chapter 3 Unit Specification e 27 UNIT3 TANK UNODE 2 5 DNODE 6 LEXIT 4 NEUTRALIZATION TANK CSA 3 14 MAXLEVEL 4 STATE 20 1 5 5 1 UNIT4 ENTRY DNODE 5 REAGENT FEED STATE 20 1 5 8988 0 0 1012 VALV3 DNODE 5 CV 10 CLOO3 VID 3 SPUNIT 3 SPID PH SPVAL 9 KC 0 01 TAUI 1 This second part must have all of the required Keywords e g TIME since only Node information has been stored In the 4th line of this Input file UNIT2 is an ENTRY with the temperature pressure total flow and composition specified by LOGNODE 2 The LOGNODE references the Node Number from the previous run the Node Number that was stored In the second part UNIT2 has a DNODE 2 but the LOGNODE and DNODE need not be the same Thus as this second part is executed the same mass and energy appears at Node 2 in this run
14. CLOO4 VID 4 POSI SPUN 3 SPID LEVEL SPVA 2 7 TIME 0 KC 2 TIME 0 VCON 35 TIME 0 NODE ORDER 1 9 3 4 106 e Chapter 12 DynaChem Pressure Vessel A Guide to Using DynaChem CASE Consecutive DynaChem Pressure Vessels TITLE TWO CONSECUTIVE PRESSURE VESSELS WITH CONTROL PRINT OUTPUT 1 SUMMARY 1 INTERA TIME TEND 20 TINC 01 TIME 0 UNITI ENTRY DNODE 1 CONTINUOUS FEED COND TEMP 30 0 PRES 2 0 TOTA 120 0 H20 55 51 HNO3 0 7 H2S04 0 1 NANO3 0 01 NA2CO3 0 004 CO20 1 UNIT3 TANK PV TOP 10 UNODE 1 DNODE 3 10 SURGE TANK 1 CSA 19 635 MAXL 10 LEXI 25 10 COND TEMP 20 0 PRES 1 TOTA 135 H20 1 0 CO2 0 001 UNIT4 ENTRY DNODE 9 CONTINUOUS FEED 2 COND TEMP 30 0 PRES 2 0 TOTA 120 0 H20 55 51 HNO3 0 7 H2S04 0 1 NANO3 0 01 NA2CO3 0 004 CO20 1 UNITS TANK PV TOP 10 UNODE 9 10 DNODE 4 12 SURGE TANK 2 CSA 19 635 MAXL 10 LEXI 25 10 COND TEMP 20 0 PRES 1 5 TOTA 135 H20 1 0 CO2 0 001 VALV1 DNODE 1 CV 100 VOPE 1 TIME 0 VALV2 DNODE 9 CV 100 VOPE 1 TIME 0 VALV3 DNODE 3 CV 100 VALV4 DNODE 4 CV 100 VALV10 DNODE 10 CV 10 VOPE 1 0 PFCN 3 VALV12 DNODE 12 CV 10 VOPE 1 0 PFCN 3 PDOWN 1 0 CLOO1 VID 3 POSI SPUN 3 SPID LEVEL SPVA 2 7 TIME 0 KC 2 TIME 0 VCON 35 TIME 0 CLOO4 VID 4 POSI SPUN 3 SPID LEVEL SPVA 2 7 TIME 0 KC 2 TIME 0 VCON 35 TIME 0 CLOO2 VID 10 VELO SPUN 3 SPID PRES SPVA 3 2 TIME 0 TAUI 1 0 KC 2 TIME 0 CLOO3 VID 12 VELO SPUN 5 SPID PRES SPVA 2 8 TIME 0 TAUI 1 0 KC 2 TIME 0 A Guide to Using DynaChem Ch
15. Increment 0 01 hour Dead Time 0 015 hour Initial Valve Stem Position 0 Velocity Algorithm Kc 0 1 Taul 0 TauD 0 Delta Stem 0 1 Err n Err n 1 Columns 1 2 3 and 4 on the following page Time pH Error and Output are all computed t he same regardless of Dead Time When Dead Time 0 default the Input to the valve is identical to the Controller Output at the time increment In this case however the Dead Time 0 015 hour causes the Output to be delayed by 1 5 time increments before it is applied as Input to the valve Column 5 shows the reference time for the Output reaching the valve as Input Time Dead Time Column 6 shows the valve Input and Column 7 the resulting Stem Position 76 e Chapter 5 CONTROL LOOP SPECIFICATION A Guide to Using DynaChem When Dead Time is not an integral of the time increment the Input to the valve Output is a composite of controller Output from two time increments The Output from the controller begins at the specified time computation time and remains in effect until the next time increment begins 1 2 3 4 5 6 7 Measured Output Ref Time Input Valve Time pH Error Stem Time Stem Stem Movt Dead Movt 00 7 1 1 9 0 0 0 01 7 1 1 9 0 0 0 02 5 2 3 8 0 19 0 005 0 0 03 4 0 5 0 0 12 0 015 0 095 0 095 04 d 2 5 8 0 08 0 025 0 155 0 250 05 2 9 6 1 0 03 0 035 0 100 0 350 06 3 1 5 9 0 02 0 045 0 055 0 405 07 5 5 3 5 0 24 0 055 0 005 0 410 08 7 6 1 4 0 21 0 065 0 1
16. Stream varies from 15 C to 50 C as shown in the first plot The resulting temperature at the Heater exit Node 2 is as shown in the second plot 44 e Chapter 3 Unit Specification A Guide to Using DynaChem Temperature at Node 1 Feed Stream Temperature at Node 2 60 Heater Exit 45 MS i Deg C Deg C 30 15 Time hr Time hr As the exothermic reaction proceeds the Reactor temperature increases and the exit temperature Node 3 increases from 35 C to 90 C This increase is shown in the first plot below The Cooler exit Node 4 is maintained at a maximum of 60 C shown in the second plot Temperature at Node 3 Reactor Exit Temperature at Node 4 90 Cooler Exit Deg C Time hr Time hr Application 4 By partitioning a tubular reactor into sections each one represented by a Pipe Unit plug flow characteristics reactor backmixing can be accurately modeled Coupled with ProChem s Reaction Kinetics capability DynaChem can be used in this manner to model a complex Plug Flow Reactor Application 5 A Guide to Using DynaChem Chapter 3 Unit Specification e 45 2 UNIT2 o PIPE A filter is to be modeled in which the liquid leaving the unit is to be placed at Node 4 and the solid leaving the unit is to be placed at Node 6 There will however be some solid suspended in the liquid 0 005 gram of solid per grain of liquid and some liquid dissolved in the solid 0 001 gram of liquid per gram o
17. and will begin in an Open position VOPEN 1 0 The downstream pressure will be 1 atm PDOWN 1 0 4 The pressure in the Void Volume is computed after the TANK equilibrium computation The equilibrium condition in the TANK is determined using an estimated pressure Prank With the equilibrium results including the vapor compressibility z temperature Tx and the moles of vapor VaApormoles the pressure in the void space is determined Pvoid atm z Vapormoies R Tx Void Volume M Based upon the Pvoiq and Ppownstream the TANK pressure Prank is determined When Pvoid Ppownstream then Prank is set equal to Ppownstream and the equilibrium is recomputed Under these conditions no flow may occur and the effective TANK pressure is the downstream pressure Thus Prank Ppownstream and the pressure difference across the valve is zero When Pvoid gt Ppownstream then Prank is set equal to Pyoig and the equilibrium is recomputed This computation is done iteratively until the pressure used for the computation Prank is the same as the resulting computed Void Volume pressure Pvoia Under these conditions flow may occur depending upon the VALV computation 5 Instep 3 above VALV10 is specified with a downstream pressure of 1 atm Another necessary specification is the type of pressure function to be used in computing the flow through the valve The Keyword used is PFCN as shown below VALV10 DNODE 10 CV 10 VOPEN 1 0 PDOWN 1 0 PFC
18. as appeared at Node 2 in the first execution Since the first part was executed with TEND 1 0 TINC 0 01 values for Node 2 will be available for time 0 0 01 0 02 0 03 1 0 The second part could be executed with different time parameters with the following restrictions 1 Node values are available only to time 1 0 If the second part were run past that point Node 2 would produce zero flow 2 The time increment TINC for the second part must be less than or equal to the time increment for the first part Application 8 A rate limited reaction is to occur in aqueous solution in a stirred reactor However one of the reactants inflow species number 4 is to be metered into the reactor in its pure component form i e non aqueous It is known that at the temperature and pressure of the Entry stream 25 C and 1 atm the fluid is liquid The maximum flow will be 5 m hr of the pure liquid The DynaChem input for the Entry Unit should contain STATE 25 1 5 0 0 0 1 NONSTANDARD LIQ All of the other Keywords apply the same as if the stream were aqueous and an equilibrium computation was to be made Furthermore the stream may be multicomponent The stream may contain any combination of the inflow species as long as each species which is specified in the STATE line does exist in the phase 28 e Chapter 3 Unit Specification A Guide to Using DynaChem designated For example if NaCl is specified in the STATE then NONSTANDARD SO
19. e 15 for every additional movement of I m of level 1 Error unit above Setpoint and will close 0 15 for every additional movement of I m below the setpoint In this case the units of Kc are Fractional Change of Stem Position Level Change in Meters Kc is possible since the Control Loop is to be Direct Acting That is as the Error increases level moves above Setpoint the Valve Stem Position must increase increase tank exit flow In the pH Control Loop the Setpoint will be 9 The controller Gain will be 0 1 In this case the Gain is negative since the Control Loop is to be Reverse Acting That is as the Error increases pH moves above Setpoint the Valve Stem Position must decrease reduce NaOH flow The level Control Loop will also have an Integral time of 2 minutes and the pH Control Loop will have an Integral time of 1 minute Since the Velocity algorithm is a derivative type function the Integral action becomes a reflection of the most recent Error see Velocity Algorithm Definition above A Guide to Using DynaChem Chapter 5 CONTROL LOOP SPECIFICATION e 55 Because of the mixing characteristics of the tank Dead Time of 0 025 hour will be included in the pH Control Loop In addition both of these loops will have implicit Dead Time implications See Dead Time CLOO1 VID 6 SPUNIT 1 SPID LEVIEL SPVAL 3 KC 0 15 TAUI 2 CLOO2 VID 7 CLID 3 SPUNIT L SPID PH SPVAL 9 KC 0 1 TAUI 1 DEAD TIME 0 025 VALV6 DNODE 4 CV 30 VAL
20. entry for all combined Pump Curves in the entire model may not exceed 500 Specifications Optional PSWITCH V Pump speed override Fraction of pump maximum speed default 1 Pump Algorithm Definition The following values are supplied to the Pump computation SPEED Pump speed rpm Maximum Pump Speed Pump Speed Override FLOW Total fluid through pump m hr Sum of flows placed at all Downstream Nodes associated with the Pump PSUCT Suction Pressure m H20 Upstream Unit Pressure Fluid Height PELEV Pump elevation with respect to Unit zero level m Pump Curves Developed Head meter H20 Flow m hr 80 e Chapter 6 PUMP SPECIFICATION A Guide to Using DynaChem A series of coordinates is entered using the Keyword PCURV to define each Pump Curve Up to 20 Curves may be entered for a Pump The values entered for Pump Curve i are Speed i Flow 1 1 Head i 1 Flow L2 Head 1 2 The Pump discharge pressure is computed as follows 1 2 3 Compute the Developed Head Determine Pump Curve i having Speed i lt SPEED and Pump Curve j win have Speed j gt SPEED Thus the Pump Speed SPEED lies between curves i and j Sfactor SPEED Speed i Speed j Speed i If the Pump Speed is less than the lowest Speed 1 then the lowest Speed Curve is used and SFactor 0 If the Pump Speed is greater than the highest Speed i then the highest Speed Curve is used and SFactor 0 For
21. flow at time 0 25 hour reaching its maximum at time 0 40 hour ramp time 0 15 hour and stop at time 0 7 hour duration 0 45 hour Start again at time 0 85 hour reaching maximum flow immediately step change ramp time 0 and stop again at time 0 95 hour duration 0 1 hour This series of flows will repeat hourly A Guide to Using DynaChem Chapter 3 Unit Specification e 25 Max FLOW TIME DynaChem Input INITIATE 0 25 0 85 DURATION 0 45 0 1 TRAMP 0 15 REPEAT 1 2 3 4 The REPEAT Keyword causes the INITIATE DURANON TRAMP series to be repeated starting at each of the specified times Notice that the series begins at time 0 Therefore even though the flow does not begin until time 0 25 hour the specified Repeat times must coincide with time 0 Thus after the initial series flow actually begins at time 1 25 hour 2 25 hour etc Application 5 Suppose there is a valve in the exit line for the flow described in 2 above Furthermore suppose either the valve capacity C or the valve stem reduces the maximum flow to one half of the maximum flow specified in the STATE specification Old Oo ee eeeeeececccececceseeescesem Max FLOW New Max til til tr1 til td1 TIME The maximum flow is reduced to the maximum allowable by the valve The rate at which the flow increases from zero to the STATE maximum does not change That is the slope of the Ramp does not change Therefore the effective ramp ti
22. is accomplished in much the same manner as building a steady state process simulation case First the process should be sketched with the appropriate inflows process units and connecting streams Conversion to dynamic units should not be attempted until the basic layout is complete For example a simple neutralization process may be represented as shown below Reagent Feed s Process Feed Neutralization Exit Stream s Surge Feed s Neutralization Stream s Tank s Vessel s Process control valves pumps and auxiliary units may be added after the basic units have been specified Unit Definition The Process Feed Stream should be defined first Since there are no upstream units to define the now at this point a DynaChem ENTRY Unit must be used Before describing the DynaChem Input however a note about nomenclature is in order In the following discussion Units will be designated with a box UNIT 1 Type Unit Name and Nodes will be designated with a line terminated with an arrowhead and termination point noted with a circle containing the Node Number A Guide to Using DynaChem Chapter 2 Building a DynaChem Case e 9 In the case of the Process Feed Stream the Unit will be Unit 1 and the resulting feed stream will accumulate at Node 1 UNITI ENTRY Process Feed The identifying numbers for Units and Nodes are arbitrary and may be any integer from 1 to 50 In this case the Node Number is
23. is computed from the suction pressure and the Head developed by the pump The Head is determined from a pump curve entered by the User as a function of flow and pump speed Control Loop Specification In general a Control Loop 1 measures a process variable temperature pressure pH level flow or composition from a specified Unit or Node i e stream 2 compares that value to a specified Setpoint and as a result 3 makes adjustments to a Valve Stem Position a Pump Speed or another Control Loop Setpoint Various controller algorithms are available including Velocity Positional Switch Multicascade Ratio and Trim For PID controllers the Gain Integral time and Derivative time are selected by the User but may be changed during execution for tuning purposes Dead Time Controller output limits and Controller output factors may be specified Time Print and Save Specifications The Time Increment and End Time must be specified for all executions The PRINT specification is used to set the frequency of printing to computer files of output summary and trace information The PRINT specification is also used to set the mode to Interactive if desired The SAVE specification is used to set the frequency of saving the Restart file It is also used to save Node information for the LOGNODE capability A Guide to Using DynaChem Chapter 1 Introduction e 7 Chapter 2 Building a DynaChem Case Building a DynaChem Case
24. necessary length If however the User intends to interrupt an Interactive run it should be remembered that the SAVE capability default is to write a Restart file at the end of the run only Therefore when entering a high value for End Time with the intention of interrupting before reaching the Time the SAVE Keyword should be used to save the Restart file at a reasonable frequency The objective of DynaChem is to represent an analog process with a digital and therefore discrete model The time increment is the means of translating the discrete characteristics into analog characteristics The smaller the time increment the closer the discrete model approaches the analog process The smaller the time increment however the greater the computer time necessary to simulate a given time period Thus a compromise between minimizing the departure from analog characteristics and realistic computer execution time is necessary SCHEDULED PARAMETER ADJUSTMEENT TIME V The capability to schedule a change in one or more parameters at a specified time greatly increases the flexibility of batch DynaChem executions Reference Table 2 shows the Specification Keywords for which this capability applies Unit and Node State may not be adjusted using TIME v and in general equipment changes are not allowed Me following briefly summarize the types of parameters for which TIME v is NOT allowed 1 Unit Geometry CSA Volume Height Length Exit Lev
25. of a Node in the computation order results in the execution of the Unit computation for which that Node is a Downstream Node Node 1 gt re Node 6 e UNIT 1 UNIT 5 Node 9 Node 8 e Node Order 6 9 In the above diagram since the User has specified Node 6 as first in the Node Order Unit 5 will be computed first employing as inflows the packets placed at Nodes I and 9 during the previous time increment Outflow packets will be placed at Nodes 6 and 8 Unit 1 will be computed next since Node 9 is second in the Node Order Packets of mass energy will be placed at Nodes 1 and 9 4 e Chapter 1 Introduction A Guide to Using DynaChem Notice that it is unnecessary although not prohibited to include Nodes 8 and 1 in the Node Order They will necessarily be computed when Unit 5 and Unit 1 respectively are computed The sequence defined by this Node Order may or may not be the best computation order for the process Nodes 1 and 9 may be considered to be one time step out of phase There are conditions e g recycle in which this sequence will be appropriate It behooves the User of DynaChem to understand the dynamics of the process before establishing the Unit definition and Node computation order Implicit dead time may be introduced by manipulation of the Node Order For example in the following process illustrated in the diagram below the packet placed at Node 4 will depend upon the state of Unit 6 because of the control loop Th
26. pini PID n Controller Controller Setpoint Measured or nt ii COL CLID n A Guide to Using DynaChem Chapter 5 CONTROL LOOP SPECIFICATION e 49 The Primary Keyword in abbreviated form is CLOOi where i represents a unique identification number from 1 to 50 The maximum flow is set by the Valve Capacity and the actual flow is determined by the Valve Stem Position fraction open The Stem Position may be set by the User manual or by a Control Loop automatic The valve override VOPEN should be used to set the initial Stem Position whether the Valve is to be manual or automatic If however the Valve is initially closed it is unnecessary since the default is closed WOPEN can also be used to change the Stem Position at specified times during an execution using TIME v specification For example suppose Valve 1 is to be 10 open initially but after 0 25 hour the stem Position is to be changed to 50 open VALVI DNODE 1 VOPEN 0 1 VOPEN 0 5 TIME 0 25 The TIME 0 following VOPEN 0 1 is omitted because it is the default The flow through a Valve is computed as follows Flow Port C Pfac where Flow Flow through valve m hr Port Valve port opening fraction open Cy Valve capacity m hr Pfac Pressure factor dimensionless 1 The Valve may be specified as a Linear Valve default or an Equal Percentage Valve The type of Valve and the Rangeability R are used to convert the Valve Stem Position Stem to the Va
27. positive and Valve closes Taul Integral time min TauD Derivative time min Application 1 Two common applications of the Velocity algorithm are level control and pH control Consider a Neutralization Tank with the need to maintain level and pH closely to specific setpoints In this case level is controlled by 1 measuring the level in the Neutralization Tank UNIT1 2 the Control Loop CLOO1 compares it to the Setpoint and 3 sends a Stem Position change to the valve VALV6 Similarly pH is controlled by 1 measuring the pH in the Neutralization Tank UNIT1 2 the Control Loop CLOO2 compares it to the Setpoint and 3 sends a Stem Position change to the valve VALV7 The output from the pH Control Loop CLOO2 will also be sent to a Multicascade Control Loop CLOO3 54 e Chapter 5 CONTROL LOOP SPECIFICATION A Guide to Using DynaChem Reagent Stream To Multicascade Control Loop CLOO3 VALV7 Ll q EN gt i CL002 Neutralization Tank The Tank level Setpoint SPVAL will be set at 3 m The Error is defined as Error Measured Level Setpoint The controller Gain KC will be 0 15 For a Velocity controller with Proportional only i e Kc only without Taul or TauD Stem Position Change Kc Error j Error j 1 where Error j is the Error for the current time increment and Error j 1 is the Error for the previous time increment Thus the Stem will open an additional 0 15 i
28. the maximum level of 4 m Thus all fluid above that level will exit The tank will be Unit 3 and the exit will be to Node 6 The initial contents will be 5 5 m of pure water at 200 The DynaChem Input for the Neutralization Tank UNIT3 TANK UNODE 2 5 DNODE 6 LEXIT 4 NEUTRALIZATION TANK CSA 3 14 MAXLEVEL 4 STATE 20 1 5 5 1 A Guide to Using DynaChem Chapter 2 Building a DynaChem Case e 13 The final unit in the Neutralization Process is the Reagent Feed This may be represented as a tank with specified contents or merely as an ENTRY feed stream For this case the latter approach will be used The Reagent flow will be 20 weight NAOH NAOHN is the 4th Inflow at 20 with a maximum flow of 5 m hour The flow will be metered with a valve and control loop to be added later The State of the stream is Temperature Pressure 20 C 1 atm Maximum Flow Rate 5 m hr Composition in the order of the Generate Output H20 0 8988 gmole NANO3 0 0 HN03 0 0 NAOH 0 1012 NA2C03 0 0 The Unit will be Number 4 and the flow at Node 5 and the DynaChem Input for the Reagent Feed is as follows UNIT4 ENTRY DNODE 5 REAGENT FEED STATE 20 1 5 0 8988 0 0 0 1012 Unit Summary In summary the four DynaChem Units are defined as follows The DynaChem Input UNITI ENTRY DNODE 1 TRAMP 0 05 PROCESS FEED STATE 25 1 10 55 51 0 01 0 75 0 0 04 UNIT2TANK UNODE L DNODE 2 3 LEXIT 0 25 3 5 SURGE TANK CSA 7 07 MAXLEVEL 6
29. the same as the Unit Number for convenience only The Downstream Node Number need not be the same as the Unit Number The Unit and Downstream Node have been identified Now the Unit should be defined beginning with the State of the stream This includes temperature pressure flow and composition Since this is an ENTRY Unit and is used to define flow the one extensive property flow is time dependent m hr and we refer to the State of the stream The TANK and PIPE Units define physical Units which accumulate mass In these Units the extensive property is the volume of fluid contained in the Unit m and we refer to the State of the contents In either case State defines the thermochemical conditions of the fluid being defined by the Unit Entry Unit Definition In defining the ENTRY the flow may be continuous intermittent or scheduled It is necessary to know the time at which the flow begins the time over which it builds to maximum flow and the duration of the flow Later a valve may be added to adjust the maximum flow In this case we will initiate the flow at the beginning of the simulation allow 0 05 hours to reach fun flow Ramp time 0 05 hour and allow the flow to continue indefinitely continuous flow The State of the Process Feed Stream will be as follows Temperature Pressure 250 C 1 atm Maximum Flow Rate 40 m hr Composition in the order of the Chemistry Model Generation Generate Output H20 55 51
30. the valve Figure 2 the Measured Value is acquired at the beginning of the Unit computation and is therefore the final value from the previous time step A Guide to Using DynaChem Chapter 7 NODE SPECIFICATION e 85 UNIT UNIT Figure 1 Figure 2 As a result there is Implicit Dead Time equivalent to one system time increment This phenomenon does not apply to the intensive properties of temperature pressure and pH The Measured Value for these properties are determined at the end of the unit computation and therefore no Implicit Dead Time is included Figure 3 When two Units are involved in a Control Loop Figure 3 Implicit Dead Time results if the Unit with the associated Valve Unit A is computed before the Unit with the Measured Variable Unit B This phenomenon is accomplished through the NODE ORDER list No Implicit Dead Time NODE ORDER N2 N1 Implicit Dead Time equivalent to One System Increment NODE ORDER N1 N2 86 e Chapter 7 NODE SPECIFICATION A Guide to Using DynaChem Chapter 8 TIME SPECIFICATION The TIME Keyword is used to set the length of the simulation and the time increment time step size TIME TEND t1 TINC t2 Specifications Required TEND t1 End time hr default 0 only the initial conditions are computed TINC t2 Time increment hr Since Interactive cases may be terminated whenever desired the End Time should be made suitably high to allow the simulation to run for the
31. the valve on Node 2 will be identified as Valve 1 VALV1 and the control loop will be identified as Control Loop 1 CLO01 Both VALV and CLOO are Primary Keywords See A Guide to Using DynaChem Chapter 2 Building a DynaChem Case e 15 Reference Table 1 abbreviated to four letters and will begin DynaChem Input lines Specification Keywords See Reference Tables 2 and 3 will be used to specify valve and control parameters Valve 1 will have a capacity Cy of 40 m hr and will be closed initially VOPEN 0 The DynaChem Input for Valve 1 is as follows VALVI DNODE 2 CV 40 VOPEN 0 The default for the initial valve stem position is closed Therefore VOPEN 0 may be omitted To dampen the fluctuations in flow the controller will use deadband control on the measured Surge Tank level Unit 2 Deadband control establishes limits between which the measured value level is assumed to be equal to the setpoint and thus the controller error is zero When the error is zero the controller output does not change and in this case the valve stem position on the exit to Node 2 does not change Thus when the tank level is within the deadband limits in this case 1 m to 3 m the flow to the Neutralization Tank is constant facilitating pH Control If however the level does go below the lower limit the valve is closed under PID Control Kc 0 2 and if the level goes above the upper limit the valve is opened under the same PID Control Thus the ta
32. used to simplify the intermittent characteristics of the Input Independent of the flow times and durations the maximum flow may be adjusted by placing a valve in the exit line A Guide to Using DynaChem Chapter 3 Unit Specification e 23 Entry Applications Application 1 Begin flow at time 0 with a step change and continue indefinitely Max FLOW TIME DynaChem Input None Required Requires no Input because all three entries INITIATE DURANON and TRAMP are defaults Application 2 Begin flow at time til and reach maximum flow trl hours later i e ramp time tr1 Continue flow for tdl1 hours Max FLOW 0 til til tr1 til td1 TIME DynaChem Input INITIATE til DURATION td1 TRAMP tr1 24 e Chapter 3 Unit Specification A Guide to Using DynaChem Application 3 Produce Intermittent slugs of flow lasting 6 minutes 0 1 hour each occurring every 30 minutes 0 5 hour the first occurring at time 0 All will be step changes Max FLOW 0 5 1 0 1 5 2 0 2 5 TIME DynaChem Input INITIATE 0 0 5 1 0 2 0 2 5 DURATION 0 1 0 1 0 1 0 1 0 1 Since all are step changes TRAMP 0 0 TRAMP may be omitted The Input can be simplified however with the REPEAT Keyword as follows DynaChem Input INITIATE 0 DURATION 0 1 REPEAT 0 5 1 0 1 5 2 0 2 5 Furthermore since all INITIATE entries are zero the Keyword itself may be omitted DynaChem Input DURATION 0 1 REPEAT 0 5 1 0 1 5 2 0 2 5 Application 4 Begin a
33. will contain 0 001 gram of entrained liquid per gram of vapor ENTL 0 001 34 e Chapter 3 Unit Specification A Guide to Using DynaChem 5 After the liquid is dissolved in the solid and entrained in the vapor the remaining liquid containing the suspended solids and dissolved vapor may flow out the lower exit if the height of the fluid is 2 meters or greater Assuming the tank is initially empty the DynaChem Input for this Unit is as follows UNITI TANK UNODE 1 DNODE 3 2 LEXLT 2 10 CSA 7 MAXL 10 SUSP 0 0002 DISL 0 005 DISV 0 0005 ENTL 0 001 Application 5 A CSTR is to be used in a process with other units The rate limited reaction kinetics in the reactor is a relatively fast reaction and requires a small time step 0 001 hour to accurately model the reaction The overall time constant for the process however is larger 0 01 hour and TINC 0 001 would result in excessive computation time In this case the time increment may be set at 0 01 hour and the reaction time step set at 0 001 hour with the following DynaChem Input TINC 0 01 UNITI TANK UNODE 1 DNODE 2 CSA 5 MAXL 5 STATE 25 1 10 1 1 RXSTEPS 10 The reaction time step in the tank is computed as Time Step TINC RXSTEPS Since the default valve for RXSTEPS is 1 the default valve for the reaction time step would be TINC In this case the reaction time step will be 1 10 of TINC 0 001 hour Furthermore since the unreacted inflows are added to the tank at the begin
34. 0 or gt 1 CFACTOR V Controller Output Factor When Output is to be sent to another Controller as specified in CLID the Input to that Controller is the Output from this Controller multiplied times the Controller Output Factor default 1 Specification Note The most common use of CFACTOR is when the output of the Control Loop is to be the input to a Multicascade Controller In that case the output from this Control Loop may be weighted at some value between 0 and 1 along with the output from other Control Loops providing input to the Multicascade Controller A Guide to Using DynaChem Chapter 5 CONTROL LOOP SPECIFICATION e 53 Velocity Algorithm Definition Stem Movement at time j AStem Stem Fraction Open at time j Stem Fraction Open at time j 1 Note Stem may not result in a Stem Position less than 0 or greater than 1 ERROR j ERROR j 1 ion kda BAUD SS j ERROR j 1 ERROR j 1 ERROR j 2 60 TIME j TIME j 1 TIME j 1 TIME j 2 60 Tau ERROR j TIME j TIME j 1 where ERROR j Measured Value Setpoint Value at time j Gain Change in Stem Position Unit Error When Gain gt 0 Direct Action Control When ERROR is Positive Stem gt 1 0 Open Valve For example Level Control When Gain lt 0 Reverse Action Control When ERROR is Positive Step gt 0 0 Closed Valve For Example pH Control of acid waste with NaOH as pH increases above Setpoint ERROR is
35. 1 0 5 1 PIPE UNODE 8 DNODE 9 MAXVOL 0 4 STATE 20 1 0 4 1 PIPE COOLER PROCESS UNODE 9 15 DNODE 10 MAXVOL 0 7 STATE 20 1 0 7 1 PIPE UNODE 10 DNODE 11 MAXVOL 0 4 STATE 20 1 0 4 1 ENTRY COOL WATER DNODE 12 STATE 10 1 10 1 PIPE COOLER UTILITY TDISCHARGE 25 UNODE 12 DNODE 14 ENODE 15 MAXVOL 0 75 STATE 10 1 0 75 1 A Guide to Using DynaChem Chapter 3 Unit Specification e 43 VALVI DNODE 2 CV 50 VALV2 DNODE 3 CV 20 VALV3 DNODE 12 CV 10 NODE ORDER 1 2 8 9 12 14 10 11 If desired a temperature control loop may be used to measure the discharge temperature of the process stream Node 10 and adjust the cooling water flow with the valve VALV3 on the exit of Unit 10 Node 12 Application 3 Suppose a Reactor requires a heater on the inlet and a cooler on the outlet I Reactor eS You may not however be interested in the utility side of the exchangers You assume that the utilities and exchangers will be adequate to achieve the specified temperatures In this case the Reactor inlet temperature must be 30 C or greater TMIN 30 and the fluid leaving the process must be 60 C or less TMAX 60 3 UNIT3 4 UNITI UNIT2 PIPE PIPE TANK Heater Reactor Cooler UNITI PIPE UNODE 1 DNODE 2 HEATER TMIN 30 MAXVOL 0 5 UNIT2 TANK UNODE 2 DNODE 3 REACTOR CSA 78 MAXLEVEL 10 UNIT3 PIPE UNODE 3 DNODE 4 COOLER TMAX 60 MAXVOL 0 5 NODE ORDER 1 2 3 4 Suppose the temperature at Node 1 Feed
36. 12 57 m The maximum level will be 8 m The bottom of the tank will contain a spherical section with a volume of 3 2 m That volume is below the zero level of the tank The maximum volume of the tank will be 103 7 m 100 5 m in the straight side portion and 3 2 m in the spherical section below There will be two feed streams Nodes 1 and 2 and three exit streams Nodes 3 4 and 5 from bottom to top The streams will exit at levels of 0 25 m 4 m and 8 m respectively Oa UNITI pe TANK 4 OI 0 25 m 4m sm Fluid liquid solid may flow through an exit only if the fluid is at or above the level at which the exit is placed The lowest exit in this tank is at 0 25 m Thus for fluid to exit the tank the level must exceed 0 25 m which means the volume of fluid must exceed 6 3 m 3 2 m in the spherical section 0 25 m 12 57 m in the straight side section Once the fluid exceeds that level it will begin to flow through the exit The amount of flow may be limited by two factors 1 The volume of liquid which may flow during the time increment is the volume of fluid above the exit level 2 The volume of fluid in any exit is limited by the valve capacity and stem position if there is a valve If there is no valve in the line the flow is limited only by the available i e fluid level Once the fluid level exceeds 4 m the level of the second exit the fluid may flow through both exits The same two limitat
37. 15 2 8 15 5 12 7 7 5 9 2 5 10 0 PCURV 750 0 33 75 4 2 33 75 6 31 8 6 25 11 17 5 12 9 10 15 0 PCURV 1000 0 60 5 6 60 9 55 12 47 5 15 37 5 17 4 25 19 13 20 0 A Guide to Using DynaChem Chapter 6 PUMP SPECIFICATION e 83 Chapter 7 NODE SPECIFICATION The NODE Keyword is used to specify the order in which Nodes and hence all other computations are completed NODE ORDER nl n2 Specifications Required NODE nl n2 Order in which Nodes are to be computed each time increment Specification of Node Order determines the order in which all computations are completed Specification of a Node results in the computation of the following 1 The Unit directly upstream from the Node i e the Unit for which the Node is a DNODE entry 2 All Nodes in the DNODE list for that Unit 3 All Valves associated with all Nodes in 2 4 All Pumps associated with the Valves in 3 5 All Control Loops associated with the Valves in 3 6 All Control Loops associated with Control Loops in 5 Thus specification of a Node in the Node Order results in the computation of all associated Units Valves Pumps and Control Loops The selection of Node Order may result in Implicit Dead Time in the model and should be considered when defining Order See Implicit Dead Time IMPLICIT DEAD TIME When a Controller s Measured Value is the Level of the same Unit to which the valve is attached Figure 1 or the Flow at the Node associated with
38. 2 default No limits except may not result in stem position lt 0 or gt 1 CFACTOR v Controller Output Factor When Output is to be sent to another Controller as specified in CLID the Input to that controller is the Output from this Controller multiplied times the Controller Output Factor default 1 Ratio Algorithm Definition If Control Loop i employs the Ratio algorithm and Control Loop j is the destination Setpoint of Control Loop j Measured Variable of Control Loop i Ratio Value of Control Loop i Application 1 The combustion airflow to a propane burner is to be controlled with a Ratio Controller Propane C3Hs Combustion Air 21 Oxygen The Combustion reaction is carried to completion C3H8 5 02 gt 3 CO2 4 H2O The combustion air should contain 20 excess molar basis Air of course is 21 oxygen molar basis Thus Air gmole Sgmole CO2 x 12 1 gmole Air 286 C3H8 gmole 1 gmole C3H8 0 21 gmole 02 Since both gas streams are at the same temperature and pressure and the delivery pressure is low the Ideal Gas Law shows that the molar ratio is also the volumetric ratio Therefore the ratio of the volumetric flow of the Air stream to the Propane stream is 28 6 A Guide to Using DynaChem Chapter 5 CONTROL LOOP SPECIFICATION e 75 The Ratio Control Loop CLOO1 measures the flow of the Combustion gas Node 2 multiplies it times 28 6 RATIO and uses the result as the Setpoint in the Air S
39. 30 0 280 09 10 2 1 2 0 26 0 075 0 225 0 055 10 12 1 3 1 0 19 0 085 0 235 0 11 11 8 2 8 0 03 0 095 0 225 0 AZ 11 5 2 5 0 03 0 105 0 015 0 015 13 11 0 2 0 0 05 0 115 0 030 0 045 For example in the case above at time 0 04 the reference time 0 025 The valve Input for time 0 04 to 0 05 will be the Controller Output from 0 025 to 0 035 At time 0 02 the Controller Output is computed as 0 19 and remains that value until time 0 03 when it becomes 0 12 Therefore from time 0 025 to 0 035 the Controller Output was 0 19 for 0 005 hour and 0 12 for 0 005 hour These Output are applied as Input to the valve in order and weighted according to the time in effect The Input to the valve will be in two steps Initial Valve Stem Position at time 0 03 0 095 Valve Input 1 0 19 0 030 0 0251 0 095 0 030 0 020 Resulting Valve Stem Position 0 095 0 095 0 190 Valve Input 2 0 12 0 035 0 030 0 060 0 040 0 030 Resulting Valve Stem Position 0 190 0 060 0 250 From time 0 04 to 0 05 the Total Input to the valve is 0 155 Valve Input 1 Valve Input 2 For this time increment the resulting Input is the weighted average of the Output during the Reference time This is not however always the case At time 0 12 the Reference time is 0 105 The Output from time 0 105 to 0 11 is 0 19 and from time 0 11 to 0 115 the Output is 0 03 Thus Initial Valve Stem Position at time 0 11 0 0 A Guide to Usi
40. A Guide to Using DynaChem Version 17 0 ESP version 9 0 OLI Systems Inc Please note that the example problems in this manual were run under DynaChem Version 17 0 Therefore due to the ongoing refinement of the underlying OLI Databank the results produced by your current DynaChem may show modest differences from those shown in this manual Contents PREFACE 1 Chapter 1 Introduction 3 Philosophy clan libia lai eli cine nadia 3 S MUCUS ai atte Rik Heltah Se Bi Sits Lia Bank dla ua 4 Unit Specificatlon s cs sorio iaia een 6 Valve Specifcations i coniche ab AULA RL aaa ALe 6 Purnp Specificationi sori head ia RA O aa aL 6 Control Loop Specifications cicca lia fab ALLA cutis bata des anid aa i 7 Time Print and Save Specifications irnn i ea a i nat i ar s 7 Chapter 2 Building a DynaChem Case 9 Unit Definitions esir LELE E E E EN 9 Entry Unit De nitons spieren ei eesi DEAR ie aria 10 Defininis Tank Umts alal E riso 12 Defining the Surge Tank scsi caiano 12 Defining the Neutralization Tank ii 13 Unt SUMMA y e oust tise ili eine darla 14 Valve and Control Loop Definition i 15 Time and Node Order Definition i 19 Summa xi NI 20 Chapter 3 Unit Specification 21 Entry Uitni sad Al EEA LOLA ie i a ALA 21 Entry Specifications Graie nia ee iaia Lita 22 Noti Standard Phase ciiuiirsi iaia dale alora 22 Specification Notes initu fiala ai ani
41. ANK 2 The cooler will be a shell and tube exchanger with a holdup of 0 7 m on the process recycle side Also there will be 0 4 m of pipe volume on each end of the cooler The cooling water side will consist of 10 m hr of pure water at 10 C It will be assumed that sufficient heat transfer occurs to result in a cooling water temperature increase of 15 C TDISCHARGE 25 Unless the specified discharge temperature is indeed the adiabatic equilibrium temperature which it is not in this case there will be a net gain or loss of energy by the Unit If an Energy Node ENODE is included with the Unit that energy flow caused by the temperature change is placed at that Node No mass is placed at the Energy Node 42 e Chapter 3 Unit Specification A Guide to Using DynaChem In this case the energy will be transferred from Unit 11 with Node 15 ENODE 15 The Receiving Unit for the energy transfer will be Unit 8 UNODE 15 The energy transferred from Unit 11 to Unit 8 will be negative energy in that the flow of energy will actually be from Unit 8 to Unit 11 That is the enthalpy of the contents of Unit 11 will increase and the enthalpy of the contents of Unit 8 will decrease UNITI UNIT2 UNIT3 UNIT UNIT8 UNIT9 UNIT10 UNIT11 UNIT10 UNITS PIPE Cooler Process ENTRY DNODE 1 STATE 80 1 5 1 0 0 2 0 001 0 05 TANK UNODE 1 1 DNODE 2 TANK I CSA 28 MAXLEVEL 8 PIPE UNODE 2 DNODE 3 8 MAXVOL 0 5 STATE 20
42. Curve i determine the FlowG 1 lt FLOW and Flow I 2 gt FLOW Thus the Flow FLOW lies between points Flow i 1 and Flow i 2 The Developed Head associated with each of those flows are Head i 1 and Head i 2 respectively FFactor i FLOW Flow 1 1 Flow i 2 Flow 1 1 Head i Head 1 1 FFactor 1 Head i 2 Head Head 1 1 For Curve j compute the same FFactor j FLOW Flow 1 1 Flow j 2 Flow j 1 Head j Head j 1 FFactor j Head j 2 Head 1 Head i and Head j are the interpolated values for the Developed Head for Speed 1 and Speed j respectively at a fluid flow of FLOW Interpolation for Speed is computed as HEAD Developed Head m H20 Head i SFactor Head j Head i Compute the Suction Pressure Drop PSDROP Suction Pressure Drop m H20 A FLOW 2 B FLOW C Compute Pump Discharge Pressure Pump Discharge Pressure m H20 PSUCT PELEV PSDROP HEAD Pump Discharge Pressure atm PDIS 10 34 A Guide to Using DynaChem Chapter 6 PUMP SPECIFICATION e 81 Application 1 A tank recycle line will be used to maintain constant pressure on a pump discharge from a tank exit A Pump PUMPI will be placed on the exit line of a Tank UNIT2 Two lines Exit Line and Recycle Line will branch at the Pump Discharge The tank level will be controlled at 1 meter by a control loop CLOO2 adjusting the flow through a valve VALV2 on the Exit Line The dis
43. L is acceptable NONSTANDARD VAP however would not be appropriate TANK UNIT The TANK Unit may be used to represent any vessel or collection of mass and energy which may change in quantity and or volume Often this will be merely a tank but the Tank Unit may also represent such diverse physical entities as the shell side of a boiler a tray in a distillation column or a continuous stirred tank reactor CSTR The TANK is defined physically by 1 cross sectional area 2 maximum level 3 maximum volume 4 bottom volume and 5 level of exits Assuming the tank is initially empty the DynaChem Input for this Unit is as follows UNITI TANK UNODE 1 DNODE 3 2 LEXLT 2 10 CSA 7 MAXL 10 SUSP 0 0002 DISL 0 005 DISV 0 0005 ENTL 0 001 UNITi TANK Specifications Required UNODE n1 n2 Upstream Node Number s maximum for Tank Unit is 20 no minimum May include Nodes entered as Energy Nodes ENODE in other Units DNODE m1 m2 Downstream Node Number s minimum for Tank Unit is 1 and maximum is 10 STATE T P Contents xl x2 Defines initial state of fluid Not required if tank is initially empty Order of entry Temperature C Pressure atm Contents m or Alternate Units Alternate Contents Units To enter alternate units the numeric entry should be followed by GRAM for grams or GMOL for A Guide to Using DynaChem Chapter 3 Unit Specification e 29 CSA v MAXLEVEL v MAXVOL v Specification Note gm
44. LGORITHM ina ea ape E RON A R 70 Application 7 naar aaa 72 RATIO Alporithit ironici nia isa ian liana 73 Ratio Algorithm Definition ii 75 Application T snene oane i Lane 75 DEAD TIME eea a E N ER E R E AR ina T eie 76 Chapter 6 PUMP SPECIFICATION 79 Pump Algorithm Definition i 80 Applicationi iaia eni LL TE E T E EES 82 Chapter 7 NODE SPECIFICATION 85 IMPLICTT DEAD MME ranni a a E E TE 85 Chapter 8 TIME SPECIFICATION 87 SCHEDULED PARAMETER ADJUSTMEENT TIME V i 87 Chapter 9 PRINT SPECIFICATION 91 Chapter 10 SAVE SPECIFICATION 93 LEOGNODE CAPABILTEY cile alare bizona AA LR 93 Chapter 11 RESTART SPECIFICATION 95 Chapter 12 DynaChem Pressure Vessel 97 Use of the DynaChem Pressure Vessel ii 97 Example of a Single DynaChem Pressure Vessel ie 100 Example of Consecutive DynaChem Pressure Vessels ie 103 Setpoint 2 S A cassis ar i rail 103 DynaChem Input Filesi spennir e r a A E EE A E EE EE EES 106 CASE Single DynaChem Pressure Vessel e 106 CASE Consecutive DynaChem Pressure Vessels ine 107 Chapter 13 CASE STUDIIES 109 Case 1 Five Stage Ammonia Stripper Control Overhead Vapor Rate 109 A Guide to Using DynaChem Case 1A Five Stage Ammonia Stripper Control Bottoms Composition 111 Case 2 TWO Stage Neutralizat
45. LOO1 VID 1 SWITCH SPUNIT 1 SPID LEVEL OPEN 0 5 CLOSE 4 Plots of the resulting tank level and Valve Stem Position fraction open will have the following form Tank Level m eters Time hours Valve Stem Position VALV1 Time hours A Guide to Using DynaChem Chapter 5 CONTROL LOOP SPECIFICATION e 65 Application 2 A Waste Tank will accept sporadic deliveries of fluid When sufficient fluid has accumulated a batch will be removed for processing O Waste CLOOS Stream UNIT10 Sporadic TANK Waste Tank 12 VALV8 The Waste Tank will have a diameter of 3 m CSA 7 07 m and a Maximum Level of 6 m It will be desirable to maintain a minimum fluid level of 1 m in the tank The minimum batch size to be sent to processing will be 20 m If 1 m of fluid is to remain in the tank there will be sufficient fluid for a batch to be withdrawn when the level reaches 3 83 m 20 mi 7 07 m 1 m Thus the valve should open when the level reaches 3 83 m and close again when the level reaches 1 m UNIT10 TANK WASTE TANK UNODE 11 DNODE 12 CSA 7 07 MAXLEVEL 6 VALV8 DNODE 12 CV 50 CLOOS VID 8 SWITCH SPUNIT 10 SPID LEVEL OPEN 3 83 CLOSE 1 MULTICASCADE ALGORITHM The Multicascade algorithm 1 acquires the output from 1 to 5 other controllers 2 applies the Output Factors specified for those controllers 3 sums the factored outputs and 4 applies the resulting output as a Valve Stem Position chan
46. LOO1 VIID 1 POSITIONAL SPUNIT 2 SPID LEVEL SPVAL 1 3 KC 0 2 VCONSTANT 0 35 In neutralization processes large unexpected Feed Steams can occur causing significant upsets in the process The deadband controller protects the Neutralization Tank from upsets To guard against a Surge Tank overflow however the upper exit Node 3 at a level of 3 5 m is used as a backup exit with the level cannot be effectively maintained by Control Loop 1 The Setpoint of the Controller will be at 4 5 m to prevent the level reaching the maximum of 6 m The valve will be identified as Valve 2 VALV2 and the level control loop will be identified as Control Loop 2 CLOO2 The Valve will have a capacity of 50 m hr and will be closed initially which is the default VALV2 DNODE 3 CV 50 The control loop will be a Direct Acting PID Controller with the following characteristics Valve to be controlled Valve 2 Setpoint Unit Origin of Measured Variable Unit 2 Level Setpoint 4 5 m PID Control Gain Kc 0 5 Velocity Algorithm default The DynaChem Input for Control Loop 2 is as follows CLOO2 VID 2 SPUNIT 2 SPID LEVEL SPVAL 4 5 KC 0 5 The final control loop will be designed to maintain a constant pH of 9 in the Neutralization Tank A valve VALV3 will be placed on the Reagent Feed Node 5 to adjust the flow of NaOH solution into the Neutralization Tank The valve will have a capacity of 10 m hr and will be closed initially VALV3 DNODE 5 CV 10 The s
47. N 3 The Pressure Function has four alternative forms The form to be used is determined by the value entered for PFCN The forms are as follows When PFCN 0 default then Pfactor 1 0 When PFCN 1 then Pfactor bags Pbowntream ie When PFCN 2 then 1 2 Pfactor Presse Pupstream Froowntreami PUpstream Ppowntream 2 where P Average When PFCN 3 then When Pbownstream Pupstream lt 0 53 subcritical flow Pfactor Pupstream 0 599625 98 e Chapter 12 DynaChem Pressure Vessel A Guide to Using DynaChem When Ppownstream Pupstream gt 0 53 critical flow 2 PDownstream PuUpstream 2 1 2 Pfactor PUpstream 6 The flow through the valve is then computed Flow m hr Port Cy Pfac 7 ThePort Valve Port opening Stem position may be set manually or by a Control Loop In VALV10 above the Stem position is set at 1 0 VOPEN 1 0 and will not change until another manual setting such as VALV10 DNODE 10 CV 10 VOPEN 1 0 TIME 0 0 VOPEN 0 5 TIME 0 5 PDOWN 1 0 PFCN 3 where the Stem position is 1 0 from Time 0 0 hour until Time 0 5 hour at which time the Stem position is changed to 0 5 The Stem position may also be changed by a Control Loop The following Control Loop controls VALVIO VID 10 The Setpoint is the pressure SPID PRES in UNIT3 SPUN 3 The Setpoint value is 3 atm SPVA 3 0 The PID control parameters include the Gain KC 0 2 and the Integral time TAUI
48. V7 DNODE 5 CV 20 It is important to remember that the Control Loop sets the Valve Stem Position which ranges from 0 to 1 The Valve Stem Position is then converted to the Valve Port Opening See VALVE SPECIFICATIONS which also ranges from 0 to 1 The Port is then applied along with the Valve Pressure Factor to the Valve Capacity C to determine the actual flow The Valve Capacity not only sets the maximum flow but for a given Stem Position change its magnitude sets the rate of change of the flow Application 2 Although the Positional algorithm is often used for flow control the Velocity algorithm is effective in many cases In this case the flow at Node 4 will be controlled with a valve VALV1 immediately preceding it The Setpoint will be 5 m hr The Gain KC will be 0 075 Reverse Acting CLOO1 VID 1 SPNODE 4 SPID FLOW SPV AL 5 KC 0 075 VALVI DNODE 4 CV 10 56 e Chapter 5 CONTROL LOOP SPECIFICATION A Guide to Using DynaChem Application 3 NH3 in the bottoms stream of an Ammonia Stripper is to be controlled by adjusting the steam rate to the stripper with an inlet valve VALV3 UNITS TANK Ammonia Stripper Bottom Stage Steam Stripper Flow Bottoms The bottoms stream is equivalent in composition to the liquid on the bottom stage UNITS The measured variable COMP will be the mole fraction MOLF of NH3 in the liquid phase LIQ The Setpoint for the NH3 mole fraction will be 0 002 0 2 mole A
49. Values of Control Loops must have a source Thus each Control Loop with Velocity algorithm must have a SPID and either a SPUNIT of SPNODE Specifications Optional SPCOMP Name Units Phase Setpoint Composition Specifications Required when SPID COMP Name Species Inflow or Base Name When Species is used must be AQ or ION and Phase must be Liquid when Base Name is used such as CO2 refers to same as inflow such as CO2IN Units Composition units WTER for weight fraction MOLF for mole fraction MOLA for molality species only GMOL for gmoles GRAM for grains Phase Composition phase when Name Species Liquid only z TOT for total all phases combined not available with Species LIQ for liquid VAP for vapor not available with Species SOL for solid not available with Species TAUI v Integral time min default 0 TAUD v Derivative time min default 0 DEADTIME v Dead Time from process measurement to Output or Stem action hr default 0 KCPOLY A B C D Variable Gain coefficients Polynomial form default 0 for all coefficients Kc A B MV C MV 2 D MV MV Value of Measured Process Variable KCEXP A B C D Variable Gain coefficients Exponential form default 0 for all coefficients Kc A B C exp D MV MV Value of Measured Process Variable OLIMIT v1 v2 Controller Output limits low limit v1 and high limit v2 default No limits except Stem may not result in stem position lt
50. WINDUP No windup in Controller default Windup allowed SPCOMP Name Units Phase Setpoint Composition Specifications Required when SPID COMP Name Species Inflow or Base Name when Base Name is used such as CO2 refers to same as inflow such as CO2IN Units Composition units WTER for weight fractions MOLF for mole fraction MOLA for molality GMOL for gmoles GRAM for grams Composition phase TOT for total all phases combined LIQ for liquid VAP for vapor SOL for solid TAUI v Integral time min default 0 TAUD v Derivative time min default 0 KCPOLY A B C D Variable Gain coefficients Polynomial form default 0 for all coefficients Kc A B MV C MV 2 D MV MV Value of Measured Process Variable KCEXP A B C D Variable Gain coefficients Exponential form default 0 for all coefficients Kc A B C exp D MV MV Value of Measured Process Variable Phase DEADTIME v Dead Time from process measurement to Output or Stem action hr default 0 OLIMIT v1 v2 Controller Output limits low limit v1 and high limit v2 default no limits except may not result in stem position lt 0 or gt 1 CFACTOR v Controller Output Factor When Output is to be sent to another Controller as specified in CLID the Input to that Controller is the Output from this Controller multiplied times the Controller Output Factor default 1 Specification Note The most common use of CFACTOR is when the output of the Con
51. apter 12 DynaChem Pressure Vessel e 107 NODE ORDER 1 9 3 4 108 e Chapter 12 DynaChem Pressure Vessel A Guide to Using DynaChem Chapter 13 CASE STUDIIES The following cases are examples of the application of DynaChem to common engineering problems The first Example Case is a Five Stage Ammonia Stripper which begins with pure water at 25 C on all stages Liquid containing water ammonia and carbon dioxide is fed to the top of the column and steam is fed to the bottom Two control schemes are tested First Case 1 the overhead vapor flow rate is controlled by adjusting the steam feed flow rate Second Case 1A the bottoms ammonia composition is controlled by adjusting the steam feed flow rate In both cases the column reaches steady state operation in 0 20 hour The second Example Case is a Two Stage Neutralization of an aqueous stream containing sulfuric and nitric acids The neutralization is being achieved with 20 NAOH in Stage 1 and 1 NAOH in Stage 2 Both NAOH flows are controlled by pH PID controllers with setpoints of 3 for the first stage and 9 for the second stage One hour after startup the control stabilizes The third example is a tank with the initial contents at 90 C and a continuous 95 C feed A cooling coil and recycle line are used to lower the temperature to 60 C and maintain it at that level The control scheme achieves the setpoint and stabilizes after 2 5 hours Case 1 Five Stage Ammonia Stripper Cont
52. ar Required when Equal percentage Hysteresis Deadband Fraction of Stem Movement default 0 Valve Stick Slip Fraction of Stem Movement default 0 Chapter 4 VALVE SPECIFICATION e 47 PFCN v Pressure function default 0 0 f p 1 0 1 f p Pu Pd 5 2 f p Pavg Pu Pd 5 48 e Chapter 4 VALVE SPECIFICATION A Guide to Using DynaChem Chapter 5 CONTROL LOOP SPECIFICATION In general a Control Loop 1 measures a process variable temperature pressure pH level flow or composition from a specified Unit or Node 2 compares that value to a specified Setpoint and as a result 3 makes adjustments to a Valve Stem Position a Pump Speed or another Control Loop Setpoint Control Loops may also acquire information form another Control Loop rather than a Unit or Node Various controller algorithms are available including 1 Velocity 2 Positional including Deadband 3 Switch 4 Multicascade 5 Ratio and 6 Trim Each of these algorithms is described in one of the following sections For PID controllers the Gain Integral time and Derivative time are selected by the User but may be changed during execution for tuning purposes Dead Time Controller Output Limits and Controller Output Factors may be specified Each of these is described in detail in the Algorithm Section in which it applies Schematic Controller A Measured utput i no reni D i i Controller Output easure Variable gt i 3
53. be revised Measured Variable Unit ID used with SPID TEMP PRES PH LEVEL or COMP Measured Variable Node ID used with SPID TEMP PRES PH FLOW or COMP Measured Variable Value ID SPID TEMP for Temperature C SPID PRES for Pressure atm SPID PH for pH SPID LEVEL for Level m May not be used with SPNODE SPID FLOW for Flow m Hr May not be used with SPUNIT SPID CONT for Composition SPCOMP also required Inputs i e Measured Value of Control Loops must have a source Thus each Ratio Control Loop must have a SPID and either a SPUNIT or SPNODE For a Ratio Controller SPUNIT SPNODE and SPID are the same as a SPVAL case except they refer to the Measured Variable not actually to a Setpoint Specifications Optional SPCOMP Name Units Phase Setpoint Composition Specifications Required when SPID COMP Name Species inflow or base Name when Base Name is used such as CO2 refers to same as inflow such as CO2IN Units Composition units WTER for weight fraction MOLF for mole fraction MOLA for molality GMOL for gmoles GRAM for grams Phase Composition phase TOT for total all phases combined LIQ for liquid VAP for vapor SOL for solid 74 e Chapter 5 CONTROL LOOP SPECIFICATION A Guide to Using DynaChem DEADTIME v Dead Time from processed measurement to Output or Stem action hr default 0 OLIMIT v1 v2 Controller output limits low limit v1 and high limit v
54. charge pressure will be controlled at 2 atm by a control loop CLOO3 adjusting the flow through a valve in the Recycle Line VALV3 The discharge pressure will be measured at Node 2 Recycle Line Three Pump Curves will be entered Speed 500 rpm Speed 750 rpm Speed 1000 rpm Flow Head Flow Head Flow Head m hr m H20 m hr m H20 m hr m H20 0 15 0 33 7 0 60 2 8 15 4 2 33 75 5 6 60 5 12 5 31 9 55 7 7 5 8 6 25 12 47 5 9 2 5 11 17 5 15 37 5 10 0 12 9 10 17 4 25 15 0 19 13 20 0 The Pump suction line will exit the Tank at the zero level and drop 0 1 meter to the Pump PELEV The discharge from the Pump splits to form the Exit and Recycle Lines Both lines are entered as having an exit level of zero LEXIT 0 0 which is the default and need not be entered The maximum Pump Speed PSPEED will be 1000 RPM and the Pump Speed Override PSWITCH will be set at 0 8 so that the effective pump speed will be 800 RPM The Suction Pressure Drop coefficient PSDROP will be 0 02 i e Pressure Drop 0 02 Flow 2 The DynaChem Input File is as follows 82 e Chapter 6 PUMP SPECIFICATION A Guide to Using DynaChem NODE ORDER 1 2 UNIT VALV2 VALV3 CLOO2 CLOO3 PUMPI TANK UNODE 1 3 DNODE 2 3 CSA 5 MAXVOL 15 STATE 90 1 DNODE 2 CV 40 DNODE 3 CV 20 VID 2 SPUNIT 2 SPID LEVEL SPVAL 1 KC 0 15 TAUI 1 VID 3 SPNODE 3 SPID PRES SPVAL 2 KC 0 04 TAUI 0 5 DNODE 2 3 PELEV 0 1 SPSEED 1000 PSWTICH 0 8 PSDROP 0 02 PCURV 500 0
55. control That could become an issue if the feed flow is substantially increased Level settings on the liquid level Deadband control may not be achievable if the flow increases The liquid valve may need to be increased in size or another control scheme devised All of these and many other scenarios can be tested with the DynaChem model A Guide to Using DynaChem Chapter 12 DynaChem Pressure Vessel e 105 DynaChem Input Files CASE Single DynaChem Pressure Vessel TITLE TWO CONSECUTIVE PRESSURE VESSELS WITHOUT CONTROL PRINT OUTPUT 1 SUMMARY 1 INTERA TIME TEND 20 TINC 01 TIME 0 TITLE TWO STAGE NEUTRALIZATION UNITI ENTRY DNODE 1 CONTINUOUS FEED COND TEMP 30 0 PRES 2 0 TOTA 120 0 H20 55 51 HNO30 7 H2S04 0 1 NANO3 0 01 NA2C030 004 C020 1 UNIT3 TANK PV TOP 10 UNODE 1 DNODE 3 10 SURGE TANK 1 CSA 19 635 MAXL 10 LEXI 25 10 COND TEMP 20 0 PRES 1 TOTA 135 H20 1 0 CO2 0 001 UNIT4 ENTRY DNODE 9 CONTINUOUS FEED 2 COND TEMP 30 0 PRES 2 0 TOTA 120 0 H20 55 51 HNO30 7 H2S04 0 1 NANO3 0 01 NA2CO30 004 C020 1 UNIT5 TANK PV TOP 10 UNODE 9 10 DNODE 4 12 SURGE TANK 2 CSA 19 635 MAXL 10 LEXI 25 10 COND TEMP 20 0 PRES 1 5 TOTA 135 H20 1 0 CO2 0 001 VALV1 DNODE 1 CV 100 VOPE 1 TIME 0 VALV2 DNODE 9 CV 100 VOPE 1 TIME 0 VALV3 DNODE 3 CV 100 VALV4 DNODE 4 CV 100 VALV10 DNODE 10 CV 10 VOPE 1 0 PFCN 3 VALV12 DNODE 12 CV 10 VOPE 1 0 PFCN 3 PDOWN 1 0 CLOO1 VID 3 POSI SPUN 3 SPID LEVEL SPVA 2 7 TIME 0 KC 2 TIME 0 VCON 35 TIME 0
56. control loop is the value from the previous time increment The time between measurement of the pH and its use in the control algorithm is one time increment Therefore the Implicit Dead Time is equivalent to one time increment Since no dead time is desired in this case Node 6 will be computed before Node 5 NODE ORDER 1 2 6 5 Summary This example was not intended to be exhaustive in describing the capabilities or use of DynaChem Rather Building a DynaChem Model is meant as an example of the procedure which should be used in defining a DynaChem model Many other applications of the Units Valves Pumps and Control Loops are possible and should be investigated in the appropriate Sections of this Handbook For details on each of the areas described in the example you should also refer to the appropriate Sections of Handbook 20 e Chapter 2 Building a DynaChem Case A Guide to Using DynaChem Chapter 3 Unit Specification A Unit is any portion of a process which can be isolated based upon homogeneity and equilibrium The Primary Keyword is UNITI where i represents a unique identification number from 1 to 50 There are three types of Units available in DynaChem 1 ENTRY Unit introduction of mass and energy into the process 2 TANK Unit any vessel of collection of mass and energy which may change in quantity and or volume 3 PIPE Unit any process unit which maintains constant volume Entry Unit The ENTRY Unit provi
57. ction of Pipe contents from previous time increment which remains in the Pipe MaxVol Maximum pipe volume Volume MPipe t2 Volume occupied by the Mass in Pipe at time t2 Specific Volume Mass in Pipe The known values in these equations are MInflow t2 defined by upstream Nodes MPipe tl computed in previous time increment The unknown values in these equations are MPipe t2 Volume Mpipe t2 is a direct function of the State of the Pipe contents MNode t2 FRAC The equations are solved simultaneously for the three unknowns It should be noted that Inflows force material out of the Pipe The inflows and previous contents ARE NOT MIXED before the material is forced out This preserves the plug flow nature of the Pipe The following flow conditions can occur 1 When the volume of the Inflows is less than the Maximum Pipe volume FRAC is greater than 0 and less than or equal to 1 A Guide to Using DynaChem Chapter 3 Unit Specification e 39 1 When the combined Inflows MInflow t and previous pipe contents MPipe t1 result in a volume GREATER THAN the Maximum Pipe Volume Max Vol then the value of FRAC is greater than 0 and LESS THAN 1 As FRAC increases from 0 to 1 the degree of Backmixing decreases and the mixing phenomenon proceeds from CSTR FRAC 0 to Plug Flow FRAC 1 2 When the combined Inflows MInflow t2 and previous pipe contents Mpipe t1 result in a volume LESS THAN the Maximum Pipe Volume MaxVol th
58. cutive DynaChem Pressure Vessels The downstream pressure of the first vessel Unit 3 is the pressure of the second vessel Unit 5 The downstream pressure of the second vessel Unit 5 is set by the valve on its vapor exit Ppownstream Both vessels are initiated with the same contents as in the above single vessel case and both were fed with the same stream as above single vessel case The vessel geometries i e CSA Maximum Level Exit Levels and Control Loop parameters are also the same as in the single vessel case TOP volume 10 m MAXLEVEL 10 777777 De Pbowstream Setpoint 3 2 MAXLEVEL 10 f gt Pressure Vessel TOP volume 10 m Pressure Vessel 196 35 m 10 m 196 35 m 10 m The control loops were set to control the pressure of the upstream vessel Unit 3 at 3 2 atm and the downstream vessel Unit 5 at 2 8 atm The value for Ppowstream Was set at 1 atm As in the single vessel case the result is a relatively slow evolution of vapor in both vessels which is predominately CO and HO The pressure begins to increase in each vessel with the vapor outlet valves closed and vapor accumulating in each vessel When the downstream vessel Unit 5 approaches its setpoint 2 8 atm the valve opens and begins releasing vapor to equilibrate the pressure at the setpoint Meanwhile the vapor outlet valve on the upstream vessel Unit 3 remains closed until its pr
59. des a means of introducing mass and energy into the process by 1 Continuous flow 2 Intermittent flow 3 Scheduled flow see LOGNODE Capability The flow may 1 begin as a step change or 2 be ramped from zero to a maximum flow over a specified time period The maximum flow may be adjusted with a valve which may be controlled by a control loop Aqueous or non aqueous streams may be introduced into the process Schematic A Guide to Using DynaChem Chapter 3 Unit Specification e 21 Entry Specifications Specifications Required DNODE n Downstream Node Number minimum and maximum for Entry Unit is 1 STATE T P Flow x1 x2 State of Entry Stream fluid Not required when using LOGNODE Order of entry Temperature C Pressure atm Maximum flow m hr or Alternate Units Alternate Flow Units To enter alternate units the numeric entry should be followed by GRAM for grams hr or GMOL for gmoles hr Molar fraction Inlet Comp 1 Molar fraction Inlet Comp 2 Molar fraction Inlet Comp N Specifications Optional INITIATE til t12 Time at which Entry flow begins hr default 0 DURATION tdl td2 Duration over which Entry flow continues hr zero implies continuous flow default 0 TRAMP trl tr2 Time during which Entry flow ramps from zero flow to maximum flow hr zero implies step change default 0 REPEAT v Time s at which entire series of INITIATE DURATION entri
60. e Node Order of 6 4 will result in no dead time since the state of Unit 6 will be determined for the time increment before the control loop linked to Unit 4 is computed The Node Order of 4 6 will result in dead time equal to one time increment because Unit 4 will be computed first using the state of Unit 6 at completion of the previous time increment Node 1 e UNIT 6 Node 6 e The Unit and Node structure and Node Order defined by the user provides flexibility but must be carefully examined to achieve the desired results A Guide to Using DynaChem Chapter 1 Introduction e 5 Unit Specification There are three types of Units available in DynaChem They are named 1 ENTRY 2 TANK and 3 PIPE The ENTRY Unit provides a means of introducing mass energy into the process by continuous flow intermittent flow or scheduled flow The mass energy flow may be defined by direct input or based upon values saved from a previous DynaChem execution The TANK Unit may be used for any vessel or collection of mass energy which may change in quantity and or volume as well as state In many cases this will be a tank but also may be the shell side of a boiler a tray of a distillation column or a continuous stirred tank reactor CSTR The TANK is defined physically by cross sectional area maximum level maximum volume and exit level The liquid level is computed and updated every time increment The PIPE Unit may be used for any proce
61. e above description of flow refers to fluid Fluid in this case includes the liquid and solid phases perfectly mixed Vapor however is assumed to separate completely 1 The vapor will exit preferentially from the top exit down to the bottom exit In this case the 8 m exit will receive vapor flow first if any vapor exists 2 The vapor will not exit through a line which is below the fluid liquid solid level In this case if the fluid level is 4 4 m the vapor may exit only through the top 8 m exit 3 In the same manner as fluids the volume of vapor in any exit is limited by the valve capacity and stem position is there is a valve Application 2 All inlet and outlet streams in Application 1 have included both mass and energy There are cases however when only energy is being transferred from one unit to another For example in the tank above a cooling coil may be added By including a Pipe Unit UNIT2 with an inlet temperature of 20 C Node 6 and a discharge temperature TDIS of 40 C Node 7 the energy required to increase the temperature 20 C will be taken cooling from the tank at Node 8 Energy being taken at Node 8 is equivalent to Negative Energy being added at Node 8 32 e Chapter 3 Unit Specification A Guide to Using DynaChem The above DynaChem Input becomes UNITI TANK UNODE 1 2 8 DNODE 3 4 5 LEXIT 0 25 4 8 CSA 12 57 MAXLEVEL 8 BOTTOM 3 2 UNIT2 PIPE UNODE 6 DNODE 7 ENODE 8 TDIS 40 Node
62. e meters 12 Chapter 2 Building a DynaChem Case A Guide to Using DynaChem This defines the physical characteristics of the tank itself The outlet lines will terminate with Node 2 0 25m and Node 3 3 5 m The initial State of the fluid contained in the tank will be defined as 20 m of pure water at 20 C Temperature Pressure 20 C 1 atm Initial Liquid 20 m Composition H20 1 0 The previously defined Feed Stream Unit 1 provides the Upstream Node The DynaChem diagram becomes UNIT 1 ENTRY Process Feed The DynaChem Input for the Surge Tank UNIT2 TANK UNODE 1 DNODE 2 3 LEXIT 0 25 3 5 SURGE TANK CSA 7 07 MAXLEVEL 6 STATE 20 1 20 1 Defining the Neutralization Tank It should be noted that to this point we have described only the physical characteristics of the Surge Tank its exits and the initial contents of the tank The flow through the exit lines will be further determined by the valves in those lines capacity and fraction open and the fluid pressure determined by liquid height and pump flow and speed These parameters may in turn be determined by Control Loops All of these will be described later The next Unit is the Neutralization Tank the Unit in which the neutralization takes place The Neutralization Tank is defined similarly to the Surge Tank It has a CSA of 3 14 m radius 1 m and a maximum level of 4 m The fluid will exit the Neutralization Tank flowing over the overflow baffle at
63. e remainder are equally divided Do not allow a vapor phase to be considered default vapor allowed if present in Chemistry Model Definition Do Not Compute Equilibrium after time zero Mass and energy is conserved but temperature pH etc are estimated This may be used for tanks that have no inflows such as reagent storage tanks default compute equilibrium at each time increment Unit name solids gms liquid In computing the mass and energy at the downstream Nodes first the mass and energy in the inflow streams are combined with the contents remaining in the tank from the previous time increment the equilibrium condition is then computed From the equilibrium computation the total volume of the combined mass is determined From that volume the tank level is determined Mass and energy is placed at each downstream Node based 30 e Chapter 3 Unit Specification A Guide to Using DynaChem upon 1 exit level and 2 valve capacity and stem position Vapor is separated from the fluid liquid solid and is treated differently Fluid liquid solid is placed at downstream Nodes from the lowest exit to the highest Vapor is placed at downstream Nodes from the highest exit to the lowest A common use of the Tank Unit is a vessel in which several streams enter are mixed with the existing contents and exit through multiple exits Application 1 Consider a tank with a diameter of 4 m and therefore a cross sectional area of
64. el 2 Controller algorithm and capabilities NOWINDUP 3 Valve type capacity Rangeability Pressure function 4 Pump curves elevation suction pressure drop A Guide to Using DynaChem Chapter 8 TIME SPECIFICATION e 87 Many of these including most equipment changes may be altered in the Interactive Mode of DynaChem See INTERACTIVE Capability For example in Interactive Mode a Tank size exit level and valve capacity may be altered by Interrupting Execution and making the changes using the supplied Screens The parameters which may be adjusted with Scheduled Parameter Adjustment TIME v are summarized as follows 1 Controller Settings Primary Keyword CLOOP CFACTOR v Controller output factor CLOSE v Switch algorithm Close setpoint DEADTIME v Dead Time KC v Gain OLIMIT vl v2 Controller output limits OPEN v Switch algorithm Open setpoint RATIO v Ratio Controller ratio value see note SPVAL vl v2 Setpoint value s TAUD v Integral time TAUI v Derivative time TRIM v v2 Trim controller limits see notes VCONSTANT v Valve constant Bias Note RATIO and TRIM may be used to adjust the associated numerical values only if the algorithm in effect already i e at TIME 0 2 Valve Position Primary Keyword VALVE VOPEN V Valve override 3 Pump Switch Primary Keyword PUMP PSWITCH V Pump speed override 4 Pipe temperature Primary Keyword UNM TDISCHARGE V Pipe discharge temperature TMAX V Pipe maximum temperature 5
65. el database does not contain adequate enthalpy data Enthalpy cal gmole A B TK C TK 2 D TK TK Temperature Kelvin NOVAP Do not allow a vapor phase to be considered default vapor allowed if vapor phase was present in Chemistry Model Definition aaaa Unit name Specification Notes INITIATE DURATION TRAMP entries should be matched That is Til tdl trl represent the first flow interval ti2 td2 tr2 represent the second and so on Trailing zeros do not need to be entered Furthermore if all entries for any one of the Keywords INITIATE DURATION or TRAMP are zero then the Keyword itself may be omitted For example if all flows are to be step changes then the Keyword need not be used for the Unit Multiple sets of INITIATE DURATION TRANP entries must not overlap in time That is the first set enters from til to til tdl The second set enters from ti2 to ti2 td2 Therefore ti2 must be greater than or equal to til tdl The maximum number of INITIATE DURATION TRAMP sets allowed for ALL ENTRY Units combined is 200 200 may be entered for a single ENTRY Unit or they may be distributed among the maximum 50 ENTRY Units INITIATE DURATION and TRAMP are not applicable when using LOGNODE Various flow patterns can be produced with the INITIATE DURATION and TRAMP Keywords Continuous flow requires a minimum of Input while Intermittent flow requires a little more specification However the REPEAT Keyword may be
66. en the value of FRAC in the above equation becomes GREATER THAN 1 which is physically impossible In this case FRAC is set equal to 1 and therefore MNode t2 0 2 When the volume of the Inflows is exactly equal to the Maximum Pipe Volume FRAC is equal to 0 In this case no material is mixed i e No Backmixing and the extreme of pure Plug Flow is achieved 3 When the volume of the Inflows is greater than Maximum Pipe Volume FRAC is less than 0 This condition of course is illegal and an ALARM results The fluid in the pipe is totally mixed If any vapor or solid phases exist at equilibrium they will be mixed with the liquid phase Consequently since vapor has a significantly greater specific volume than the liquid and solid phases the presence of vapor could have a significant impact on the fluid leaving the pipe In particular the sudden occurrence of vapor could cause a flash effect in which a slug of fluid is forced out of the pipe Once the total displaced volume is determined it is placed at the downstream Nodes in the following order 1 For all downstream Nodes with a valve the allowable volumetric flow through the valve is computed and that volume of mixed fluid is placed at the Node If the Node is designated with LNODE VNODE or SNODE only the appropriate phase with modifications by SUSPEND etc is placed at the Node This procedure proceeds through the DNODE list in order for all exits with valves until t
67. es are to be repeated The series to be repeated starts at time 0 and extends through the last INITIATE DURAT ION LOGNODE nl n2 The Entry flow is to be Scheduled by acquiring the Node flows from the Node Input file which was the result of a previous run with SAVE LOGN n n2 Non Standard Phase Nonstandard stream phase designation When this designation is used the Entry stream may be composed of any inflow species in the Chemistry Model The stream does not need to contain water Equilibrium condition is not computed it is defined by the Phase Designation The enthalpy is computed to make it consistent with any aqueous fluid to which it is added Density is computed to define flow rate Phase LIQ for liquid default VAP for vapor SOL for solid 22 e Chapter 3 Unit Specification A Guide to Using DynaChem Note When using Nonstandard the designated phase does NOT need to be present in the Chemistry Model For example to inject stream NONS VAP may be used even if H20V AP is not in the model However in these cases the DENS and ENTH keywords must be used to specify density an enthalpy DENSITY A B C D Density Coefficients used to compute density of Nonstandard Streams when the chemistry model database does not contain adequate density data Density gmole liter A B TK C TK 2 D TK TK Temperature Kelvin ENTHALPY Enthalpy Coefficients used to compute enthalpy of Nonstandard Streams when the chemistry mod
68. essure reaches its setpoint 3 2 atm After that the controllers on the vapor outlet valves on each vessel adjust the valve stem position to achieve the desired setpoint pressure A Guide to Using DynaChem Chapter 12 DynaChem Pressure Vessel e 103 3 5 Unit 3 Setpoint 3 2 atm E Unit 5 Setpoint 2 8 atm 25 2 D H 2 Pressure Vessels Vessel Pressure 1 5 PID Control 1 0 5 10 15 20 Time hr 1 Valve 12 0 9 from Unit 5 0 8 0 7 0 6 Pressure Vessels Stem Position Fraction Open da Stem Positions 0 4 PID Control 0 3 0 2 0 1 Valve 10 from Unit 3 0 0 5 10 15 20 Time hr 104 e Chapter 12 DynaChem Pressure Vessel A Guide to Using DynaChem 20 18 16 14 12 10 Node 12 from Unit 5 Pressure Vessels Vent Flow Node Flow m hr 6 PID Control 4 2 Node 10 from Unit 3 0 0 5 10 15 20 Time hr From the dampening of the oscillations in the flow through the two vapor outlet valves it is apparent that both vessels are approaching steady state after 20 hours There are perhaps better combinations of Valve Capacity Cy PID Gain Kc PID Integral time Taul or other process parameters which would achieve a faster approach to steady state Another valuable exercise would be to perturb the process with increased feed flow different feed composition different pressure setpoints etc to determine the response So far nothing has been said about the liquid level
69. et streams will be the outlet streams from the other Tank Units trays Application 4 A tank is generating solids and vapor under conditions in which 1 a portion of the solids is suspended in solution and the remainder settles and 2 the vapor velocity causes liquid to be entrained In addition liquid is dissolved in the settled solid and vapor is dissolved in the liquid All of these phenomena may be modeled with the Tank Unit The vapor containing entrained liquid will exit from the top of the tank Node 2 at a level of 10 m A lower exit Node 3 will be located at 2 m The liquid solution containing suspended solids and dissolved vapor will exit this line The default condition in both tanks and pipes is 1 100 mixing of solids in the liquid solution SUSP infinite 2 liquid entertainment ENTL 0 3 no liquid dissolved in the solid DISL 0 and 4 no vapor dissolved in the liquid DISV 0 In this tank after the equilibrium condition has been determined the phases will be separated as follows 1 All solids will settle to the bottom of the tank except 0 0002 gram of solid will be suspended in the liquid per gram of liquid SUSP 0 0002 2 In the settled solid 0 005 gram of liquid will be dissolved per grain of solid DISL 0 005 3 All of the vapor will move to the top of the tank and exit the highest exit except 0 0005 grain of vapor will be dissolved per gram of liquid DIS V 0 0005 4 The vapor exiting
70. eters 3 m the Valve will open under PID Control and if the level goes below 0 5 m the A Guide to Using DynaChem Chapter 5 CONTROL LOOP SPECIFICATION e 61 Valve will close under PID Control In this case the Deadband range is 0 5 to 3 m SPVAL and the Deadband Valve Position is 0 30 WCONSTANT The PID Control above and below the Deadband region will utilize a Gain of 0 2 KC The Positional algorithm is used with the following qualifications 1 Below the Deadband region the Error is computed using the lower Deadband limit as the Setpoint 2 In the Deadband region the Error is set to zero 3 Above the Deadband region the Error is computed using the upper Deadband limit as the Setpoint The result is as follows For Level lt 0 5 m Valve Stem Position 0 2 Level 0 5 0 3 For 0 5 lt Level lt 3 m Valve Stem Position 0 3 For Level gt 3 m Valve Stem Position 0 2 Level 3 0 0 3 The DynaChem Input is as follows CLOO1 VID 2 POSITIONAL SPUNIT 4 SPID LEVEL SPVAL 0 5 3 VCONSTANT 0 3 KC 0 2 Note that the Deadband range is entered as two Setpoint values the lower first SWITCH ALGORITHM The Switch algorithm is used to fully open a valve at one Setpoint and fully close the valve at another Setpoint The algorithm may also be used to activate and deactivate a pump in the same manner Dead Time is optional CLOOi SWITCH where 1 represents a unique identification number from to 100 Specifications Req
71. f solid The filter may be described by the following DynaChem input UNIT2 PIPE UNODE 2 DNODE 4 5 LNODE 4 SNODE 6 STATE 50 1 14 1 CSA 0 5 MAXV 14 SUSP 0 005 DISL 0 001 Note that although LNODE and SNODE are used for Nodes 4 and 5 they still must be included in the DNODE list 46 e Chapter 3 Unit Specification A Guide to Using DynaChem Chapter 4 VALVE SPECIFICATION A VALVE is used to restrict the flow of mass and energy and therefore the amount of mass and energy which may be placed at a Node during a time increment A Valve may be used preceding any Node but only one Valve may be used before any Node The Primary Keyword in abbreviated form is VALVI where i represents a unique identification number from 1 to 50 Schematic _ LS Each Valve must be associated with a downstream Node and a maximum capacity must be specified VALVI Specifications Required DNODE n CV v Specifications Optional VOPEN v LINEAR EQUAL RANGEABILITY v HYSTERESIS v STICK v A Guide to Using DynaChem DNODE n CV v Downstream Node Number minimum and maximum number of DNODE s for a Valve is 1 Valve capacity m hr Valve override Stem position until changed by Control Loop intervention default 0 closed Linear valve default Linear Equal percentage valve default Linear Rangeability 1 Rangeability valve opening with fully closed stem position default Infinitely large when Line
72. fied point in time The Specification itself designates how often the entire process is to be saved The resulting saved file may be used in a RESTART to initialize and restart the process at the time it was saved LOGNODE allows the User to save across the entire simulation time dimension time a specified point in the process a Node The Specification designates the Node s to be saved The resulting saved file may be used in an ENTRY Unit to enter the mass and energy at that Node as a scheduled inflow to the subsequent model See LOGNODE capability SAVE Specifications Optional FREQUENCY v Frequency of saving entire process to Restart File hr default at TEND only LOGNODEz nl n2 Nodes to be saved in the Node Output file for all time increments to be used as input in an ENTRY Unit in a subsequent ran LOGNODE CAPABILITY The LOGNODE capability allows the user to save for all time steps the State temperature pressure flow and composition of up to 10 Nodes A subsequent execution may then use the saved information in an ENTRY Unit as a Feed stream In the first execution save the information at Nodes n1 n2 SAVE LOGNODE ni n2 A complete description of the Nodes at all times computed are stored in the Node Output file That Output file becomes the Node Input file for the second execution In that execution the Nodes stored in the above procedures may now be used as follows UNITi LOGNODE n1 DNODE m1
73. ge Thus the output of a Multicascade Controller is applied as a Velocity Controller is applied as a AStem Dead Time and Output Limits are optional 66 e Chapter 5 CONTROL LOOP SPECIFICATION A Guide to Using DynaChem Schematic Controller doreerereocoreoceceseoce0 Ubi f ussessesosssssesoosoesosoen cele a a Multicascade on Controller sescrosececereceeseeceseo AD eesseseeseeseeseseeseesesea CLOOi MULTICASCADE where i represents a unique identification number from 1 to 100 Specifications Required MULTICASCADE Multicascade algorithm Controller Output Sum of up to 5 Factored Stem movements determined by other Control Loops VID n Valve ID to which Control Loop output is to be sent Specification note Inputs of Control Loops must have a source Multicascade inputs come from Control Loops having a CLID entry specifying the Multicascade Control Loop as its destination Specifications Optional DEADTIME v Dead Time from process measurement to Output or Stem action hr default 0 OLIMIT v1 v2 Controller Output limits low limit v1 and high limit v2 default No limits except may not result in stem position lt 0 or gt 0 Specification Note A Guide to Using DynaChem Chapter 5 CONTROL LOOP SPECIFICATION e 67 The Output Limits shown here are for the Multicascade Output If Output Limits are to be placed on the Inputs to the Multicascade Control Loop they should be entered with the Control
74. ge 1 CLOO1 when the valve on the Reagent Flow VALV6 is closed That is the valve being closed is interpreted as meaning that too much neutralization is being accomplished in Stage 1 resulting in no action required by Stage 2 Thus the Setpoint in Stage 1 is made more acidic requiring less neutralization Similarly if the valve is open too much it means the Setpoint in Stage 1 is too low and should be raised to result in more neutralization before reaching Stage 2 VALVS XH UNIT2 TANK Stage 2 The Valve Stem Position of the reagent stream to the 2nd Stage Neutralization tank VALV6 Controlled by CLOO3 is compared to Trim Limits of 0 15 and 0 4 specified in CLOO2 The Factor is then computed with Limits of 0 75 and 1 2 OLIMIT 0 75 1 2 which means that the Factor itself cannot be less than 0 75 or greater than 1 2 OLIMIT applies only to the Factor not to the resulting Setpoint value s 72 Chapter 5 CONTROL LOOP SPECIFICATION A Guide to Using DynaChem In computing the Factor 1 2 3 4 When the Valve Stem VALV6 is open less than 15 the feed to Stage 2 is judged to be too alkaline for good control Therefore the pH Setpoint for the Ist stage is lowered to reduce the neutralization carried out in Stage 1 When the Valve Stem VALV6 is open greater than 4 the feed is judged to be too acidic and the pH Setpoint in Stage 1 is increased If the Step Position VALV6 is between 15 and 4 it i
75. gmole NANO3 0 01 HN03 0 75 NAOH 0 0 NA2C03 0 04 The composition of 55 51 gmoles of H20 0 01 gmole of NaNO3 etc are relative quantities Values of 1 0 0 00018 etc are equivalent since the relative molar quantities are the same The total mass is determined by the Flow Rate Composition determines only the relative molar quantities 10 e Chapter 2 Building a DynaChem Case A Guide to Using DynaChem The DynaChem Input for this Unit may now be assembled All DynaChem input must begin with a Primary Keyword See Reference Table 1 In this case the Primary Keyword is UNIT Primary Keywords are followed by Specification Keywords See Reference Tables 2 and 3 which apply to the Primary Keyword in effect until another Primary Keyword is employed The flow characteristics are translated into DynaChem Input using Specification Keywords as follows STATE Temperature C Pressure atm Maximum Flow Rate m hr Composition in order of the Inflow List as specified in the Generate Output The composition may be in any units as long as they are entered in relative molar amounts INITIATE Initiation time hr TRAMP Ramp time hr DURATION Duration hr Name Unit Name The Primary and Specification Keywords are then assembled to create the definition of Unit 1 UNITI ENTRY DNODE L INITIATE 0 TRAMP 0 05 DURATION 0 PROCESS FEED STATE 25 1 40 55 51 0 01 0 75 0 0 4 The series of Specification Key
76. he Setpoint will be 5 m hr The Gain KC will be 0 075 Reverse Acting The Valve Constant Bias will be 0 4 which is the Valve Stem Position when the Error is zero CLOO1 VID 1 POSITIONAL SPNODE 4 SPID FLOW SPVAL 5 KC 0 075 VCONSTANT 0 4 VALVI DNODE 4 CV 10 Application 2 An effective means of dampening the fluctuations of feed streams is by using a Surge Tank with Deadband Control on the exit Deadband Control is utilized with the Positional algorithm Consider a Surge Tank with several input streams having varying flows and compositions These inflows will have variable effects on the tank level The one output stream exits to a process unit in which controllability is important and difficult That controllability can be enhanced by minimizing the upsets caused by changes in flow exiting the Surge Tank If the flow is controlled directly by the tank level the variable nature of the inflows will be transferred to the exit flow If however a range of acceptable levels Deadband is defined in which the exit flow will remain constant and the level will be allowed to float the fluctuations in exit flow will be eliminated as long as the level is within the deadband limits Suppose the Surge Tank is to have a maximum level of 5 m When the level is between 0 5 m and 3 m the Valve Stem Position on the exit flow will remain at 0 30 30 open If the level goes above Valve Position 0 5 5 1 1 5 2 2 5 3 3 5 4 4 5 5 Level m
77. he entire displaced volume has been distributed 2 If any displaced volume remains after all downstream Nodes with valves have been computed all of the remaining flow is placed at the first downstream Node in the DNODE list without a valve If that Node is designated with LNODE VNODE or SNODE then the appropriate phase is placed at the Node and the remaining flow is placed at the next downstream Node without a valve Care should be taken to provide sufficient capacity in the exit lines Since the total volume leaving the pipe is a function of the volume displaced by the inflows as compared to the TANK in which the volume leaving the tank is a function of the exit lines if all downstream Nodes have valves it is possible to exceed the capacity of the exit lines Therefore either one exit should remain without a valve or one valve should have a very large capacity Application 1 The simplest use of the Pipe Unit is as a section of pipe This application results in process dead time and reduces backmixing A series of pipes will 1 delay the impact of a wave front e g 40 e Chapter 3 Unit Specification A Guide to Using DynaChem temperature pH composition one time increment for each Pipe Unit employed and 2 increase the amplitude of the wave front compared to one large pipe or a tank by reducing the dilution effect As an example consider a tank with a recycle line lt Recycle Line sE TANK 1 la TANK 2 To accura
78. i represents a unique identification number from 1 to 100 Specifications Required VELOCITY Velocity algorithm PID Control Controller Output Stem Movement distance VID n Valve ID to which Control Loop output is to be sent CLID n Control Loop ID to which Control Loop output is to be sent PID n Pump ID to which Control Loop output is to be sent SPUNIT n Setpoint Unit ID used with SPID TENT PRES pH LEVEL or COMP SPNODE n Setpoint Node ID used with SPID TEMP PRES pH FLOW or COMP SPID a Setpoint Value ID SPID TEMP for Temperature C SPID PRES for Pressure atm SPID pH for pH SPID LEVEL for Level m may not be used with SPNODE SPID FLOW for Flow m Hr may not be used with SPUNIT SPID COMP for Composition SPCOMP also required SPVAL Setpoint value default 0 KC v Gain default 0 See Also TAUI and TAUD Gain gt 0 for Direct Action Gain lt 0 for Reverse Action See Algorithm definition below Specification Notes Since VELOCITY is the default algorithm it is not necessary for it to appear as a Specification 52 e Chapter 5 CONTROL LOOP SPECIFICATION A Guide to Using DynaChem The output of each Control Loop must have a destination Thus each Control Loop must have either a VID CLID or PID In some cases the Control Loop may have two destinations e g when the output is to be sent to a Valve and to a Multicascade Controller both VID and CLID would be used Inputs i e Measured
79. id plus suspended solid and dissolved vapor only A Solid Node allows solid plus dissolved liquid only A 2nd Liquid Node allows organic liquid plus dissolved aqueous suspended solid and dissolved vapor only When LNODE VNODE and or SNODE are specified the total quantity of mass to be placed at the downstream Node s is determined first using the same phase proportions as exist in the Unit at the end of the previous time step That total displaced quantity is then placed at the downstream Node s in DNODE order but with the LNODE VNODE SNODE restriction enforced on any designated Node Furthermore SUSPEND DISVAPOR ENTLIQUID and DISLIQUID may be used to modify what otherwise would be single phase Nodes SUSPEND v DISVAPOR v ENTLIQUID v DISLIQUID v DISORGANIC v DISAQUEOUS v RXSTEPS n RXTINC t1 t2 NOVAP NOEQ aaaaa 38 e Chapter 3 Unit Specification Solids suspended in the solution default infinite liquid gms solid gms liquid Vapor dissolved in the liquid solution gms vapor gms liquid default 0 Liquid entrained in the vapor gms liquid gms vapor default 0 Liquid dissolved in the solid gms liquid gms solid default 0 Organic liquid dissolved in aqueous liquid gms organic liquid gms aqueous liquid default infinite Aqueous liquid dissolved in organic liquid gms aqueous liquid gms organic liquid default 0 Number of Reaction Kinetics Steps per overall time step i e reac
80. ion sensos erii alia 112 A Guide to Using DynaChem Contents e iii PREFACE DynaChem is the primary dynamic simulation component of the ProChem Program for Chemical Simulation System Specifically DynaChem allows for description of one or more process units which are physically tied together by processing streams and where applicable process control The entire system is solved on an unsteady state time dependent basis DynaChem is supported by a thermodynamic framework and associated databank which allows a User to call upon a broad spectrum of reactive chemistry and reactive phenomena The architecture of the program is such that the User need know only the names of the chemicals involved and not the detailed chemical reactions A Guide to Using DynaChem PREFACE e 1 Chapter 1 Introduction Philosophy The philosophy of DynaChem is based upon discrete modular computation of process units The term process is a general term in this case referring to any chemical system This can range from a traditional chemical process to a geological system being altered by the environment The concept of isolating a process unit as a discrete computation allows for the assumption of homogeneity and chemical and thermodynamic equilibrium However limits to homogeneity and equilibrium may be established by allowing for imperfect mixing and an approach to equilibrium Once a process has been identified as a series of discrete units a two tier s
81. ional OUTPUT n Output File DOU Frequency in Number of Time Increments default 10 For example OUTPUT 0 for no output to DOU file OUTPUT 1 for output to DOU file each time increment OUTPUT 10 for output to DOU file on 1st 10th 20th time increment SUMMARY n Summary File SUM Frequency in Number of Time Increments default 1 TRACE n Trace Fide SUM Frequency in Number of Time Increments default 0 NOTERM No output to Terminal default Output to Terminal except when INTERACTIVE entered TERM Output to Terminal default Output to Terminal except when INTERACTIVE entered INTERACTIVE Interactive Mode and no output to the Terminal default Output to Terminal The Output DOU File begins with an echo of the Input The OUTPUT specification designates the frequency with which the following information for a time increment is written For each Unit and Node the composition enthalpy density and volume for each phase liquid solid and vapor temperature pressure and liquid phase pH To the Summary SUM File is written at the specified frequency a one line summary for each Unit Node and Valve Control Loop A Guide to Using DynaChem Chapter 9 PRINT SPECIFICATION e 91 Chapter 10 SAVE SPECIFICATION The SAVE Keyword allows the User to save DynaChem information across two dimensions space and time The Specification Keyword FREQUENCY allows the User to save the entire process dimension space at a speci
82. ions volume above the exit and valve capacity apply to the higher exit as well A Guide to Using DynaChem Chapter 3 Unit Specification e 31 When two or more exits qualify for fluid flow fluid will flow preferentially from the lowest exit to highest exit For example if the level reaches 4 4 m there is 5 0 m of fluid above the 4 m exit and 52 2 m of fluid above the 0 25 m exit If there is no valve in either line 52 2 m of fluid will flow through the 0 25 m exit and no fluid will exit through the 4 m exit If there is a valve in the lower line but 5 0 m of fluid still exits through the lower line then again no fluid exits through the 4 m exit If however due to a valve in the 0 25 m line only 2 m of fluid exits then the remaining 3 0 m may exit through the 4 m line assuming that there is no valve or the valve has a large enough capacity The tank is described as Unit 1 with the following DynaChem Input UNITI TANK UNODE 1 2 DNODE 3 4 5 LEXIT 0 25 4 8 CSA 12 57 MAXLEVEL 8 BOTTOM 3 2 It should be noted that in the above discussion the term flow is often used The actual quantity that is being described is the amount of mass being placed at a Node during the time increment seat is if the entire volume above an exit level flows through the exit the reality is that the volume which is above that exit level is placed at the Node The volumetric flow is indeed that volume divided by the time increment TINC Th
83. level The maximum volume is thus implied as Maximum Volume Maximum Level CSA The Surge Tank will have a CSA of 7 07 m radius 1 5 m with a maximum level of 6 m The maximum volume is therefore 42 4 m Likewise the level of the fluid liquid solid is defined as Level of Fluid Volume of Fluid CSA Defining the Surge Tank The stream or streams exiting the tank will be defined by the level at which it exits and its termination Node The Surge Tank will be Unit 2 and two lines will exit at levels 0 25 m and 3 5 m The lower exit will be the primary process flow and the higher level will provide overflow capability Fluid may flow through an exit only if the fluid is at or above the level at which the exit is placed Furthermore the fluid liquid solid flows preferentially from the lowest exit to the highest exit If during a time period the level reaches a height above the higher exit but sufficient fluid exits the lower exit to reduce the level below the upper exit then no fluid exits the higher exit If however the fluid removed from the lower exit does not lower the level below the upper exit then fluid flows out both exits Vapor exits preferentially from the highest exit to the lowest exit However vapor may not flow through an exit which is below the fluid liquid solid level A diagram of the Surge Tank is as follows Maximum Level Surge 6 meters Tank 3 5 meters 4 0 25 meters CSA 7 07 squar
84. lve Port Opening Port Linear Valve Port 1 R 1 1 R Equal Percentage Valve Port R Stem 1 2 The Valve Pressure Factor Pfac is determined based upon the Pressure Function PFCN specified by the User For PFCN 1 Pfac 1 0 For PFCN 2 Pfac Pup Pdown 5 For PFCN 3 Pfac Pavg Pup Pdown 5 where Pup Upstream pressure atm Pdown Downstream pressure atm 50 e Chapter 5 CONTROL LOOP SPECIFICATION A Guide to Using DynaChem Pavg Average pressure atm Typically PFCN 2 is used for liquid streams and PFCN 3 is used for gas and vapor Specifications Required VID n Valve ID to which Control Loop output is to be sent CLID Control Loop ID to which Control Loop output is to be sent PID m Pump ID to which Control Loop output is to be sent Specification Note The output of each Control Loop must have a destination Thus each Control Loop must have either a VID CLID or PID In some cases the Control Loop may have two destinations e g when the output is to be sent to a Valve and to a Multicascade Controller both VID and CLID would be used Specifications Optional VELOCITY Velocity algorithm PID Control Controller Output Stem Movement Distance POSITIONAL Positional algorithm PID Control includes Deadband Controller Output Stem Position SWITCH Switch algorithm Controller Output Stem fully open or fully closed MULTICASCADE Miulticascade algorithm Contr
85. m must have a SPID and either a SPUNIT or SPNODE Specifications Optional SPCOMP Name Units Phase Setpoint Composition Specifications Required when SPID COMP Name Species Inflow or Base Name when Base Name is used such as CO2 refers to same as inflow such as CO2IN Units Composition units WTFR for weight fraction A Guide to Using DynaChem Chapter 5 CONTROL LOOP SPECIFICATION e 63 MOLF for mole fraction GMOL for gmoles GRAM for grams Phase Composition phase TOT for total all phases combined LIQ for liquid VAP for vapor SOL for solid DEADTIME v Dead Time for process measurement to Output or Stem action hr default 0 CFACTOR v Controller Output Factor When Output is to be sent to another Controller as specified in CLID the Input to that Controller is the Output from this Controller multiplied times the Controller Output Factor default 1 Specification Note The most common use of CFACTOR is when the output of the Control Loop is to be the input to a Multicascade Controller In that case the output from this Control Loop may be weighted at some value between 0 and 1 along with output from other Control Loops providing input to the Multicascade Controller Switch Algorithm Definition At the Setpoint defined by SPUNIT SPNODE SPID SPCOMP becomes equal to the specified Open Value OPEN the controller output is set to 1 As the Setpoint value becomes equal to the specified Close Value
86. me or the time at which the flow levels off is reduced Application 6 An ENTRY stream with a valve may be used for metering fluid from an apparent infinite supply For example the flow of Neutralization Reagent described in Building a DynaChem Model is from an Entry Unit The maximum flow is set by the minimum of two values 1 the STATE flow 26 e Chapter 3 Unit Specification A Guide to Using DynaChem and 2 the valve capacity C The flow is then regulated by adjusting the value stem as determined by the pH control loop Application 7 Scheduled flow is accomplished by using the flows as they occurred at a Node during a previous execution For example suppose you wished to analyze in two parts the Neutralization process described in Building a DynaChem Model The first part would end with Nodes 2 and 3 and the second part would begin with Node 2 Node 3 is not an Upstream Node for any other Unit The DynaChem Input for the first part would be as follows refer to Building a DynaChem Model for the Input file as a single run SAVE LOGNODE 2 TIME TEND 1 0 TINC 0 01 NODE ORDER 1 2 PRINT OUTPUT 10 SUMMARY 1 UNITI ENTRY DNODE 1 TRAMP 0 05 PROCESS FEED STATE 25 1 40 55 51 0 01 0 75 0 0 04 UNIT2 TANK UNODE 1 DNODE 2 3 LEXIT 0 25 3 5 SURGE TANK CSA 7 07 MAXLEVEL 6 STATE 20 1 20 1 VALVI DNODE 2 CV 40 VALV2 DNODE 3 CV 50 CLOOI VID 1 POSITIONAL SPUNIT 2 SPID LEVEL SPVAL 1 3 KC 0 2 VCONSTANT 0 35
87. ng DynaChem Chapter 5 CONTROL LOOP SPECIFICATION e 77 Chapter 6 PUMP SPECIFICATION A Pump is used to increase fluid liquid suspended solid pressure The flow pump speed and User specified Pump Curves are used to determine the Developed Head The Developed Head is used with the suction head suction pressure drop and pump elevation to compute the pump discharge pressure One Pump may be associated with up to 10 Downstream Nodes all of which must be DNODE a PUMPj entries of the same Unit Valves are optional PUMP j where j represents a unique identification number from 1 to 50 Specifications Required DNODE n Downstream Node Number s minimum for Pump is 1 and maximum is 10 PELEV v Pump elevation with reference to tank zero level can be negative Default 0 PSPEED v Pump maximum speed rpm PSDROP A B C Pump suction pressure drop coefficients Pres Drop m H20 A Guide to Using DynaChem Chapter 6 PUMP SPECIFICATION e 79 A Flow 2 B Flow C Flow in m hr default A 0 B 0 C 0 PCURV S F1 H1 F2 H2 Pump Curve for speed S rpm Fl Ist Flow m hr Hl Ist Head m H20 F2 2nd Flow m hr H2 2nd Head m H20 Specification Notes For PCURV Keyword may be used multiple times in a PUMP once for each Speed The maximum number of curves per pump is 20 There is no limit to the number of points in any single Pump Curve The total number of entries including S F1 Hl each as 1
88. ning of the time increment the reaction rate is usually higher at the beginning of the overall time increment than at the end Thus it is typically more accurate to start with a lower reaction time step at the beginning of each time increment and decrease it through the increment This is done with the RXTINC Keyword Set the reaction time steps as follows Ist step 0 00002 hour 2nd step 0 0001 hour 3rd step 0 0005 hour 4th through 10th steps equally divided A Guide to Using DynaChem Chapter 3 Unit Specification e 35 The DynaChem partial Input will be TINC 0 01 UNITI TANK UNODE 1 DNODE 2 CSA MAXL 5 STATE 25 1 10 1 1 RXSTEPS 10 RXTINC 0 00002 0 0001 0 0005 By entering only the first three time steps the 4th through 10th steps are assumed to be equal to TINC The above will result in the total time increment for steps 4 through 10 being 0 00938 hour 0 01 0 00002 0 0001 0 0005 equally divided among the 7 reaction steps results in a reaction time step of 0 00134 hour for steps 4 through 10 PIPE UNIT The PIPE UNIT is used to represent a process unit which maintains constant volume This could be simply a section of pipe or it could be a tank heating cooling coil a shell and tube heat exchanger a plug flow reactor or a filter The PIPE is defined physically by 1 cross sectional area 2 length and 3 maximum volume The total mass energy at the downstream Node s is determined by the volume of material dis
89. nk level is maintained A positive value was chosen for the Gain Kc because the controller is to be Direct Acting That is when the Error is positive Error Measured Variable Setpoint then the valve should increase its opening To increase its opening the Valve Step Position must increase Stem Position change Kc Error Thus for a positive Error to increase the Step Position Kc must be positive In this case when the level increases above the Setpoint the Error becomes positive greater flow is desired increased Stem Position to lower the tank level When the Error is negative level lower than the Setpoint the Stem Position decreases decreasing the flow and causing the level to rise Deadband control should be used with the Positional Algorithm only and a Valve Constant valve stem position when Error 0 also referred to as Bias must be specified In this case a Valve Constant of 0 35 will be specified VCONSTANT 0O 35 That is when the Surge Tank level is between 1 and 3 m the valve stem will always be 35 open Thus the control loop which will control Valve 1 will have the following characteristics Valve to be controlled Valve 1 Setpoint Unit Origin of Measured Variable Unit 2 Level Deadband Control Limits 1 m to 3 m PID Control Gain Kc 0 2 16 e Chapter 2 Building a DynaChem Case A Guide to Using DynaChem Positional Algorithm Bias 0 35 The DynaChem Input for Control Loop 1 is as follows C
90. o which Control Loop output is to be sent SPUNIT n Setpoint Unit ID used with SPID TEMP PRES PH LEVEL or COMP SPNODE n Setpoint Node ID used with SPID TEMP PRES PH FLOW or COMP SPID a Setpoint Value ID SPID TEMP for Temperature C SPID PRES for Pressure atm SPID PH for pH SPID LEVEL for Level m may not be used with SPNODE SPID FLOW for Flow m Hr may not be used with SPUNIT SPID COMP for Composition SPCOMP also required SPVAL vl v2 Setpoint value s defaults 0 0 KC v Gain default 0 See Also TAUI TAUD Gain gt 0 for Direct Action Gain lt 0 for Reverse Action See Algorithm definition below VCONSTANT v Valve Constant Bias Fraction open when Error 0 or KC 0 default 0 Specification Notes The output of each Control Loop must have a destination Thus each Control Loop must have either a VID CLID or PID In some cases the Control Loop may have two destinations e g when the output is to be sent to a Valve and to a Multicascade Controller both VID and CLID would be used Inputs i e Measured Values of Control Loops must have a source Thus each Control Loop with Positional algorithm must have a SPID and either a SPUNIT or SPNODE 58 e Chapter 5 CONTROL LOOP SPECIFICATION A Guide to Using DynaChem The second value in SPVAL vl v2 is entered only for a Deadband Controller In that case the two values constitute the limits of the dead band Specifications Optional NO
91. ode is a DNODE entry 2 All Nodes in the DNODE list for that Unit A Guide to Using DynaChem Chapter 2 Building a DynaChem Case e 19 3 All Valves associated with all Nodes in 2 4 All Pumps associated with the Valves in 3 5 All Control Loops associated with the Valves in 3 6 All Control Loops associated with Control Loops in 5 Thus specification of a Node in the Node Order results in the computation of all associated Units Valves Pumps and Control Loops The Node Order is relatively straightforward in this model Node 1 will be computed first resulting in computation of Unit 1 Node 2 will be specified as the second Node This results in Unit 2 being computed and therefore Node 3 as well Thus Node 3 need not appear in the Node Order Node 2 also causes Valves 1 and 2 and Control Loops 1 and 2 to be computed Because of Control Loop 3 the order of computation of Nodes 5 and 6 could result in Implicit Dead Time If Node 6 and therefore Unit 3 is computed first then when Node 5 is computed the pH of Unit 3 for the current time increment will be available to Control Loop 3 In this case there is no Implicit Dead Time in the control loop since the measured variable is known for the current time and is applied in the control algorithm If however Node 5 is computed first then the Control Loop 3 is computed before Unit 3 has been computed for the cur rent time increment Therefore the measured variable accessed by the
92. oles Molar fraction Inlet Comp 1 Molar fraction Inlet Comp 2 Molar fraction Inlet Comp N Tank cross sectional area m2 Maximum tank level m Maximum tank volume m Any two of the three size specifications CSA MAXLEVEL MAXVOL are required The third is computed by DynaChem Specifications Optional LEXIT vl v2 BOTI OM v SUSPEND v DISVAPOR v ENTLIQUID v DISLIQUID v DISORGANIC v DISAQUEOUS v RXSTEPS n RXTINC tl t2 NOVAP NOEQ aaaaa Exit level of outlet line s from tank m in DNODE list order defaults Tank volume below tank zero level m default 0 Solids suspended in the liquid solution gms default infinite Vapor dissolved in the liquid solution gms vapor gms liquid default 0 Liquid entrained in the vapor gms liquid gms vapor default 0 Liquid dissolved in the solid gms liquid gms solid default 0 Organic liquid dissolved in aqueous liquid gms organic liquid gms aqueous liquid default infinite Aqueous liquid dissolved in organic liquid gms aqueous liquid gms organic liquid default 0 Number of Reaction Kinetics Steps overall time step i e reaction time step TINC RXSTEPS default 1 To deactivate kinetics set RXSTEPS 0 Reaction Kinetics time steps hr Up to four times may be specified Default TINC TXSTEPS The sum of the RXSTEPS time steps must be TINC Thus a maximum of RXSTEPS 1 entries may be made For less than RXSTEPS 1 entries th
93. oller Output sum of up to 5 Stem movements determined by other Control Loops RATIO V Ratio Control algorithm with a ratio value of v Controller Output Ratio measured Value TRIM vl v2 Trim Controller algorithm with limits of v1 to v2 Controller Output 1 when the referenced valve stem position is within limits Controller Output gt 1 or lt 1 when referenced valve stem position is outside limits Specification Notes Each of the above Specification Keywords designates a different control algorithm Only one algorithm may be specified for each Control Loop The default algorithm is Velocity Each algorithm is described in detail in an individual section The Specification Keywords required for each of algorithms are also described in those sections Reference Table 4 provides a summary of Required and Optional Specification Keywords for each algorithm VELOCITY ALGORTHM The Velocity algorithm is a PID Controller producing an output in Stem Movement distance A Guide to Using DynaChem Chapter 5 CONTROL LOOP SPECIFICATION e 51 Since the Output is a derivative type function AStem a Valve Constant Bias is not required and Windup does not occur Both of these are factors in the Positional algorithm Setpoint Specification is required and PID parameters are necessary Dead Time and Output Limits are optional Controller Measured anita ee Ki nt Stem VID n or CLID n PID n Schematic CLOOi VELOCITY where
94. placed by the inflows The displaced mass energy is at equilibrium and is homogeneous i e all phases are mixed and flow as a single fluid The state of the displaced material is identical to the state of the contents of the Pipe at the conclusion of the preceding time increment Downstream Nodes may be specified as liquid vapor or solid allowing the displaced material to be separated by phase Warning The Time Increment TINC must be small enough such that during no time increment shall Inflow volume be greater than the Maximum Pipe Volume MAXVOL TINC lt Maximum Pipe Volume Peak Volumetric Flow Schematic 36 e Chapter 3 Unit Specification A Guide to Using DynaChem UNITI PIPE Specifications Required UNODE nl n2 DNODE ml m2 STAT E T P Contents x1 x2 CSA v LENGTH v MAXVOL v Specification Note Upstream Node Number s maximum for Pipe Unit is 20 no minimum May include Nodes entered as Energy Nodes ENODE in other Units Downstream Node Number s minimum for Pipe Unit is 1 and Maximum is 10 Should not include any Node entered as an Energy Node ENODE in this Unit Defines initial state of fluid Not Required if pipe is initially empty Order of entry Temperature C Pressure atm Contents m or Alternate Units Alternate Contents Units To enter alternate units the numeric entry should be followed by GRAM for grams or GMOL for gmoles Molar fraction Inlet Comp 1 Molar f
95. raction Inlet Comp 1 Molar fraction Inlet Comp 2 Molar fraction Inlet Comp N Pipe cross section area m Pipe length m Maximum pipe volume m Either CSA and LENGTH must be entered or MAXVOL must be entered Specifications Optional ENODE n TDISCHARGE v TMAX v A Guide to Using DynaChem An Energy Node which transports energy only no Mass When TDISCHARGE TMAX or TMIN are used any energy lost or gained can be transported to another Unit the Receiving Unit via this Energy Node It should not be included as a DNODE for this Unit but should be included as a UNODE for the Receiving Unit Discharge temperature C Regardless of energy accumulated the outlet temperature of the pipe is set to this temperature and the resulting energy is computed Maximum temperature C The outlet temperature is determined by an adiabatic flash If the resulting temperature is less than TMAX then it is used If it is greater the outlet is set at this temperature and the resulting energy is computed e g a cooling exchanger Chapter 3 Unit Specification e 37 TMIN v LNODE n SNODE n L2NODE n Specification Note Minimum temperature C The outlet temperature is determined by an adiabatic flash If the resulting temperature is greater than TMIN then it is used If it is less the outlet is set at this temperature and the resulting energy is computed e g a heating exchanger A liquid Node allows liqu
96. rol Overhead Vapor Rate Column Description Five Stages with Stream Upflow through Liquid and Liquid Overflow Stage Description Max Liq Level0 0883m CSA 0 318 m Stage Capacity 0 028 m Valve Description Feed Stream Valve 12 m LINE Valve Override 1 Fixed Steam Valve 1900 m LINE Valve Override 1 Trim Steam Valve 100 m LINE Valve Override 0 A Guide to Using DynaChem Chapter 13 CASE STUDIIES e 109 Initial Conditions Liquid on Stages All Stages Pure H20 ue 25 C Operating Conditions Liquid Feed Begins at Time 0 Temperature 43 333 C Pressure 3 7415 atm Total Flow 11 203 m hr H2O 0 91856 mole frac NH3 0 06917 CO2 0 01227 Fixed Steam Begins at Time 0 015 hour 0 9 min Temperature 143 C Pressure 3 7415 atm Total Flow 1 84713E 03 m hr H20 1 0 mole frac Trim Steam Valve Initially Closed Temperature 143 C Pressure 3 7415 atm Total Flow 100 m hr H20 1 0 mole frac Control Loop Description Control Loop 1 Control Valve 13 Algorithm VELO Setpoint Value792 719 Value Type FLOW Setpoint Node ID 6 Controller Gain 1 0E 04 Integral Tune 0 02 110 e Chapter 13 CASE STUDIIES A Guide to Using DynaChem Calculation Order NODE ORDER 1 7 13 8 9 10 11 12 2 3 4 5 6 Approach to Equilibrium After 30 Minutes Vapor Overhead gmole hr H20 NH3 CO2 Bottoms Liquid gmole hr H20 NH3 CO2 Temperature C Stage 5 Stage 4 Stage 3 Stage 2 Stage I 45199 41176 7506
97. s judged that the feed to Stage 1 is within the range of the 2nd Stage s controllability and the pH Setpoint is left unchanged Factor 1 The Factor is applied to the Setpoint Value pH of the Control Loop controlling reagent flow to the Ist Stage CLOO1 Since the Factor is multiplied times the current Setpoint Value an initial value must be included SPVAL 2 The DynaChem Input is as follows CLOO3 VID 6 CLID 2 SPUNIT 5 SPID PH SPVAL 9 KC 0 11 TAUI 1 CLOO2 CLID 1 TRIM 0 15 0 4 KC 0 05 OLIMIT 0 75 1 2 CLOO1 VID 5 SPUNIT 4 SPID PH SPVAL 2 KC 0 01 TAUI 0 5 RATIO Algorithm The Ratio algorithm acquires the value of a specified measured variable multiplies that value times a specified factor Ratio and uses the result to replace the Setpoint of another control Loop Thus the second Control Loop becomes ratioed to the first Control Loop Schematic Ratio PID Controller Controller Measured Variable 777 gt i LA AE Q E i ote ees A Setpoint S Measured Variable CLOOi RATIO v A Guide to Using DynaChem Chapter 5 CONTROL LOOP SPECIFICATION e 73 where i represents a unique identification number from 1 to 100 Specifications Required RATIO v CLID j SPUNIT n SPNODE n SPID a Specification Notes Ratio Control algorithm with a ratio value of v Controller output Ratio Measured Value Control Loop ID to which Control Loop output is to be sent Control Loop containing Setpoint value to
98. s the NH3 mole fraction increases the steam rate must increase Therefore the Controller will be Direct Acting A Gain of 400 will be used Since the Gain is defined as Kc Fractional Change of Stem Position Error In this case a fractional change in the Stem Position of 0 1 10 corresponds to a change of 0 00025 in the NH3 mole fraction i e 400 0 1 00025 An Integral time TAUI of 0 5 minute is also included CLOO1 VID 3 SPUNIT 5 SPID COMP SPCOMP NH3 MOLF LIQ SPVAL 0 002 KC 400 TAUI 0 5 VALV3 DNODE 1 CV 1000 POSITIONAL Algorithm The Positional algorithm is a PID Controller producing an Output in absolute Stem Position Fraction Open This Algorithm may also be used for Deadband Control A Guide to Using DynaChem Chapter 5 CONTROL LOOP SPECIFICATION e 57 Setpoint Specification is required and PID parameters are necessary A Valve Constant Bias is required and Windup can occur is Integral time TAUI is used unless NOWINDUP is specified Dead Time and Output Limits are optional Controller Measured ne Arena Stem Position VID n or CLID n PID n CLOOi POSITIONAL where i represents a unique identification number from 1 to 100 Specifications Required POSITIONAL Positional algorithm PID Control includes Deadband Controller Output Stem Position VID n Valve ID to which Control Loop output is to be sent CLID n Control Loop ID to which Control Loop output is to be sent PID n Pump ID t
99. ss unit which maintains constant volume This may be no more than a section of pipe but may also be the tube side of a heat exchanger a heating or cooling coil or a plug flow reactor PFR The PIPE is physically defined by cross sectional area length and maximum volume Level is not applicable to PIPE Units No mass may exit a PIPE until the volume is fun Mass enters the PIPE and sufficient mass exits to maintain the full volume of the PIPE Many dynamic systems may be modeled with DynaChem using nothing more than Units and Nodes For such systems no further description of Valves Pumps and Control Loops is necessary Most processes however require some use of these attributes to model the precise operation of the process components Valve Specifications A VALVE is used to restrict the flow of mass energy and therefore the amount of mass energy which may be placed at a Node during a time increment The placement of a VALVE is defined by its downstream Node DNODE The maximum flow is set by the Valve capacity and the actual flow is determined by the Valve Stem Position fraction open The Step Position may be set by the User manual or by a Control Loop automatic Alternate VALVE types are available Pump Specification A PUMP is used to increase the fluid pressure The placement of a PUMP is defined by the downstream Node DNODE 6 e Chapter 1 Introduction A Guide to Using DynaChem The discharge pressure of a pump
100. t Temperature 25 C Pressure 1 atm Total Flow 60 m hr H20 0 9955 NAOH4 52902E 03 Tank Description Surge Tank CSA 19 635 Max Level 10m CSA 10 Stage 1 Stage 2CSA 10 Valve Description Valve Downstream Node 1 1 aUa A U N 2 3 5 7 8 Control Loop Description A Guide to Using DynaChem Liquid Exit 0 25 m Liquid Exit 3 m Liquid Exit 0 1 5 m Max Level 3 m Max Level 5m Capacity m hr Type Valve Override 100 LINE 1 100 LINE 1 100 LINE 100 LINE 20 LINE 30 LINE Chapter 13 CASE STUDIIES e 113 Loop Valve Unit Algorithm Type Setpoint Gain Integral Time 1 3 3 POSI Level 2 4 0 2 Valve Constant 0 35 2 5 4 VELO pH 3 0 1 1 3 6 5 VELO pH 9 0 02 1 4 4 5 VELO Level 4 0 15 2 Initial Conditions All Tanks 20 C 1 Atm Pure H2O Surge Tank 35 3 m Stage 127 0 m Stage 249 0 m NODE ORDER 1 2 9 10 3 7 4 8 5 6 114 Chapter 13 CASE STUDIIES A Guide to Using DynaChem
101. tely represent the dead time in the recycle line and the line connecting the tanks the following DynaChem model may be used UNIT6 PIPE Recycle UNITI ENTRY VALVI represents the valve on the exit line from Tank 1 Unit 3 includes the pipe volume from the exit of Tank 1 to the point at which the recycle lines splits 0 5 m Unit 4 is the pipe volume between the split and Tank 2 0 75 m Unit 6 is the recycle line volume 1 5 m Each of these sections will initially be filled with water at 20 C The tanks are initially empty UNITI ENTRY DNODE 1 STATE 80 1 5 1 0 0 2 0 001 0 05 UNIT2 TANK UNODE 1 7 DNODE 2 TANK 1 CSA 28 MAXLEVEL 8 UNIT3 PIPE UNODE 2 DNODE 3 6 MAXVOL 0 5 STATE 20 1 0 5 1 UNIT4 PIPE UNODE 3 DNODE 4 MAXVOL 0 75 STATE 20 1 0 75 1 UNITS TANK UNODE 4 DNODE 5 TANK 2 CSA 78 MAXLEVEL 10 UNITO PIPE UNODE 6 DNODE 7 MAXVOL 1 5 RECYCLE STATE 20 1 1 5 1 A Guide to Using DynaChem Chapter 3 Unit Specification e 41 VALVI DNODE 2 CV 50 VALV2 DNODE 3 CV 20 NODE ORDER 1 2 3 4 5 7 Note that Node 6 does not need to be included in the Node Order since inclusion of Node 3 will result in Unit 3 and all of its downstream Nodes being computed Application 2 An important attribute of the Pipe Unit is the combination of temperature specification TDISCHARGE TMAX and TMIN and the Energy Node ENODE Suppose the Recycle line in Application 1 contains an inline cooler Recycle Cooler T
102. tem position of Valve 3 will be controlled by Control Loop 3 CLO03 which measures the pH in the Neutralization Tank Unit 3 comparing it to the Setpoint of 9 0 The control loop will be a Reverse Acting PID Controller with a Gain of 0 01 and Integral Time of 1 minute This controller is Reverse Acting because as the pH increases above the Setpoint of 9 the Error becomes positive it is necessary to decrease the flow of NaOH solution decrease the Stem Position The control loop will have the following characteristics A Guide to Using DynaChem Chapter 2 Building a DynaChem Case e 17 Valve to be controlled Valve 3 Setpoint Unit Origin of Measured Variable Unit 3 pH Setpoint pH 9 PM Control Gain Kc 0 01 Integral Time Taul 1 min Velocity Algorithm default The DynaChem Input for Control Loop 3 is as follows CLOO3 VID 3 SPUNIT 3 SPID PH SPVAL 9 KC 0 01 TAUI 1 With the three Control Loops the Neutralization Process is defined as follows UNIT 4 ENTRY Reagent UNIT 1 ENTRY Process Feed Neutralization The DynaChem Input UNITI ENTRY DNODE 1 TRAMP 0 05 PROCESS FEED STATE 25 1 40 55 51 0 01 0 75 0 0 04 UNIT2 TANK UNODE 1 DNODE 2 3 LEXIT 0 25 3 5 SURGE TANK CSA 7 07 MAXLEVEL 6 STATE 20 1 20 1 18 e Chapter 2 Building a DynaChem Case A Guide to Using DynaChem UNIT3 TANK UNODE 2 5 DNODE 6 LEXIT 4 NEUTRALIZANON TANK CSA 3 14 MAXLEVEL 4 STATE 20 1 5 5 1 UNIT4 ENTRY DNODE
103. tepping technique is employed to simulate the dynamic nature of the process The first tier inner tier steps through the units in a predefined order for specified time increment The order typically begins with mass energy flow into the process and ends with mass energy flow out of the process The ordering however is flexible and may be altered to achieve special process conditions such as recycle In the stepping from one unit to the next unit in order packets of mass energy are introduced into the unit mixed and the resulting equilibrium condition is determined At this point limits to mixing homogeneity and equilibrium may be introduced by such principles as mixing dynamics and reaction kinetics The outgoing packets are then determined by specified parameters such as tank level valve opening and fluid pressure The outgoing packets of mass energy are then passed to the next unit in order and the procedure is repeated for that unit This first tier of computation should be conceptualized as the movement of mass energy through a process during a small but finite increment of time The second tier outer tier uses the final state of the process as defined by the inner tier as the beginning state for the next time increment The outer tier steps through time with each step resulting in a complete pass through the inner tier The discrete nature of the computation allows for a high level of flexibility in adding computation defini
104. the valve 100 open the pressure equilibrates to 2 57 atm If however one wishes to control the pressure to 3 atm there is a Stem position between 0 and 100 that should result in the increase pressure 100 e Chapter 12 DynaChem Pressure Vessel A Guide to Using DynaChem The Control Loop described in step 7 above results in the following response 3 5 Setpoint 3 atm 3 625 Pressure Vessel a n Vessel Pressure D PID Control Q 6 8 10 Time hr Magnification of the Time after 4 hours is as follows 3 1 3 05 E 3 Setpoint 3 atm amp cb 5 2 95 9 Pressure Vessel cb 2 9 Vessel Pressure PID Control 2 85 2 8 0 5 10 15 20 Time hr A Guide to Using DynaChem Chapter 12 DynaChem Pressure Vessel e 101 The Stem movement resulting in the above response is as follows 1 Pressure Vessel 0 8 Valve Stem PID Control 2 gt P Valve Stem Fraction Open 2 N 0 5 10 15 20 Time hr Note that the valve remains closed until a little past 5 hours at which time the Void space has accumulated enough vapor to result in a Void volume pressure of 3 atm It is then that the PID controller begins adjusting the Stem position based upon the Control Setpoint and Measured value 102 e Chapter 12 DynaChem Pressure Vessel A Guide to Using DynaChem Example of Consecutive DynaChem Pressure Vessels The following describes two conse
105. tion before the simulation is performed and altering of system parameters during simulation A Guide to Using DynaChem Chapter 1 Introduction e 3 Structure The structure of DynaChem is based upon Units and Nodes As described in the DynaChem Philosophy a Unit is any portion of a process which can be isolated based upon homogeneity and equilibrium This may include entities such as a tank or a section of pipe but also may be a schedule of inflows to a process which may be defined as mass energy flow as a function of time During a defined increment of time packets of mass energy are introduced into a Unit The mass energy is combined with the mass energy already present in the Unit and the equilibrium condition is determined Based upon defined Unit parameters packets of outgoing mass energy are determined and placed at collecting points called Nodes Upstream Node Downstream Node e UNIT Upstream Node Downstream Node re Thus the transmission of mass energy from one Unit to another Unit during a discrete increment of time is by accepting packets of mass energy from Upstream Nodes and depositing packets of mass energy at Downstream Nodes This structure of Units and Nodes is established by the User in DynaChem Input Units and Nodes are numbered and subsequently identified by Unit Number and Node Number The computation order of the inner tier described in Philosophy is defined by Node Order Specification
106. tion time step TINC RXSTEPS default 1 To deactivate kinetics set RXSTEPS 0 Reaction Kinetics time steps hr Up to four time steps may be specified Default TINC RXSTEPS The sum of the RXSTEPS time steps must be in TINC Thus a maximum of RXSTEPS 1 entries may be made For less than RXSTEPS 1 entries the remainder are equally divided Do not allow a vapor phase to be considered default vapor allowed if present in Chemistry Model Definition Do Not Compute Equilibrium after time zero Mass and energy is conserved but temperature pH etc are estimated This may be used for pipes that are used only for process dead time default compute equilibrium at each time increment Unit name A Guide to Using DynaChem The quantity of mass energy at the downstream Node s is the amount of material which must be removed from the pipe such that when 1 the inflows are mixed with the material remaining and 2 the equilibrium condition computed then 3 the resulting volume is equivalent to the Maximum Pipe Volume That is MPipe t2 FRAC MPipe t1 MInflow t2 MNode t2 1 FRAC MPipe t1 MaxVol Volume MPipe t2 where t2 t1 One time increment MPipe t2 Mass in Pipe at time t2 MInflow t2 Mass Inflow to Pipe during time increment t1 to t2 MPipe t1 Mass in Pipe at time t2 i e contents of pipe at end of previous time increment MNode t2 Mass placed at Nodes during time increment t1 to t2 FRAC Fra
107. tream Flow Control Loop CLOO2 The Air Stream Flow Control is simply a Velocity algorithm Reverse Acting PID Controller It differs from other such controllers only in that its Setpoint is being set dynamically by the Ratio Controller Notice that a Setpoint of 2 1 was used to initiate Control Loop 2 The DynaChem Input is as follows CLOO1 CLID 2 RATIO 28 6 SPNODE 2 SPID FLOW CLOO2 VID 4 SPNODE 3 SPID FLOW SPVAL 2 1 KC 0 1 TAUI 1 DEAD TIME Dead Time is the time period between 1 computation of the Controller Output based upon the current parameters e g Setpoint Measured Variable value Gain and 2 application of the Output to the appropriate Valve or Control Loop Dead Time may be applied to any Control Loop CLOOi DEADTIME v The Dead Time v is in hours The maximum allowable value is 10 times the system time increment TINC The default value is zero in which case the output is applied immediately There is however Implicit Dead Time inherent in some process configurations See Implicit Dead Time The procedure for applying Dead Time is as follows The Controller computes Error and Output at each time step The Output is saved and applied to the Valve or another Controller e g Multicascade Controller v hours later In the case of a Ratio Controller the revised Setpoint is also set v hours later The following is a hypothetical case to describe the application of Dead Time Setpoint ID pH Setpoint Value 9 Time
108. trol Loop is to be the input to a Multicascade Controller In that case the output from this Control Loop may be weighted at some value between 0 and 1 along with the output from other Control Loops providing input to the Multicascade Controller Positional Algorithm Definition Stem Position Fraction Open at time j Stem A Guide to Using DynaChem Chapter 5 CONTROL LOOP SPECIFICATION e 59 ERROR j TauD ERROR j ERROR j 1 60 TIME j TIME j 1 Stem Kc VConst Y ERROR k ATIME Taul where ERROR j Measured Value Setpoint Value at time j Kc Gain Change in Stem Position Unit Error When Gain gt 0 Direct Action Control When ERROR is Positive Stem gt 1 0 Open Valve For Example Level Control When Gain lt 0 Reverse Action Control When ERROR is Positive Stem gt 0 0 Closed Valve For Example pH Control of acid waste with NaOH as pH increases above Setpoint ERROR is positive and Valve closes Taul Integral time min For NOWINDUP when Stem Position 1 0 or 0 0 then no addition made to ERROR k TIME TauD Derivative time min VConst Valve Constant Bias Application 1 A common use of the Positional algorithm is flow control This case is the same as Velocity algorithm Application 2 Flow at Node 4 will be controlled with a valve VALV1 immediately preceding it 60 e Chapter 5 CONTROL LOOP SPECIFICATION A Guide to Using DynaChem T
109. troller i Valve or Controller i Position i Setpoint s Revised Valve n CLOOj TRIM s1 s2 where j represents a unique identification number from to 100 Specifications Required TRIM s1 s2 Trim Controller algorithm with Emits of s1 to s2 CLIID k Control Loop BD to which Control Loop output is to be sent Control Loop containing Setpoint value s to be revised KC v Gain default 0 Specifications Optional KCPOLY A B C D Variable Gain coefficients Polynomial form default 0 for all coefficients Kc A B MV C MV 2 D MV MV Value of Measured Process Variable KCEXP A B C D Variable Gain coefficients Exponential form default 0 for all coefficients Kc A B C exp D MV MV Value of Measured Process Variable 70 e Chapter 5 CONTROL LOOP SPECIFICATION A Guide to Using DynaChem DEADTIME v Dead Time from process measurement to Output or Stem action hr default 0 OLIMIT v1 v2 Controller Output limits low limit v1 and high limit v2 default No limits except may not result in stem position lt 0 or gt 1 CFACTOR v Controller Output Factor When Output is to be sent to another controller as specified in CLID the Input to that controller is the Output from this Controller multiplied times the Controller Output Factor default 1 A Trim Control Loop requires three controllers see diagram above 1 The Control Loop which supplies the Valve Stem Position Control Loop i CLOOi CLID j VID n
110. uired SWITCH Switch algorithm Controller Output Stem fully open or fully closed VID n Valve ID to which Control Loop output is to be sent CLID n Control Loop ID to which Control Loop output is to be sent PID n PUMP ID to which Control Loop output is to be sent SPUNIT n Setpoint Unit ID used with SPID TENT PRES PH LEVEL or COMP SPNODE n Setpoint Node ID used with SPID TEMP PRES PH FLOW or COMP 62 e Chapter 5 CONTROL LOOP SPECIFICATION A Guide to Using DynaChem SPID a Setpoint Value ID SPID TEMP for Temperature C SPID PRES for Pressure atm SPID PH for pH SPID LEVEL for Level m may not be used with SPNODE SPID FLOW for Flow m Hr may not be used with SPUNIT SPID CONT for Composition SPCOMP also required OPEN v Setpoint at which Stem is opened fully CLOSE v Setpoint at which Stem is closed fully Controller M d utput i Losereresesecceneceneoo Be Stem Position S Open or Closed VID n or CLID n PID n Controller Output Measured O curi Bn RIO i On or Off PID n Specification Notes The output of each Control Loop must have a destination Thus each Control Loop must have either a VID CLID or PID In some cases the Control Loop must have two destinations e g when the output is to be sent to a Valve and a Multicascade Controller both VID and CLID would be used Inputs i e Measured Values of Control Loops must have a source Thus each Control Loop with Switch algorith
111. unless they are entered with TIME v where v is a time greater than the time at which the information was stored The execution begins at the last time stored New entries for TIME PRINT and SAVE must be entered for the RESTART execution if required See SAVE SPECIFICATION RESTART Specifications None A Guide to Using DynaChem Chapter 11 RESTART SPECIFICATION e 95 Chapter 12 DynaChem Pressure Vessel TOP volume Pupstream Prank MAXLEVEL gt 727270000777 Pbowstream Pressure Vessel Vapor Entrained Liquid Liquid Solid Dissolved Vapor Use of the DynaChem Pressure Vessel 1 The Pressure Vessel is a TANK Unit with the Keyword PV included UNIT3 TANK PV UNODE 1 DNODE 3 10 SURGE TANK CSA 19 635 MAXL 10 LEXI 0 25 10 COND TEMP 20 0 PRES 1 5T0TA 135 H2O 1 0 CO2 0 001 2 The Void volume in the TANK is computed as the volume above the liquid level including the TOP volume Void Volume m MAXLEVEL Liquid Level m CSA m TOP Volume m 3 When the TANK has been specified as a Pressure Vessel the top Exit must have a valve with a downstream pressure The downstream pressure is specified in the VALV section with the Keyword PDOWN A Guide to Using DynaChem Chapter 12 DynaChem Pressure Vessel e 97 VALV10 DNODE 10 CV 10 VOPEN 1 0 PDOWN 1 0 In this case Downstream Node 10 from the above TANK UNIT3 will have a valve with Cy 10 m hr
112. words must be initiated with a Primary Keyword In the case of UNIT its Identification Number must also be included The Specification Keywords should be 1 in any order 2 separated from each other by at least one space 3 placed on multiple lines if desired 4 continued on a subsequent line with a in column 1 This applies to continuation of the entries pertaining to a single Specification Keyword Starting a subsequent line with a Specification Keyword is not considered a continuation In many cases there are default values for Specification Keywords See Reference Table 3 in which case the entry may be omitted For example the default for the initiation of an ENTRY flow is zero INITIATE 0 and the default for duration is continuous DURATTON 0 Therefore the above Input may be amended to UNITI ENTRY DNODE L TRANP 0 05 PROCESS FEED STATE 25 1 40 55 51 0 01 0 75 0 0 04 A Guide to Using DynaChem Chapter 2 Building a DynaChem Case e 11 Defining Tank Units The Process Feed Stream is now defined The next Unit in the Process is the Surge Tank the destination of the Process Feed The Surge Tank is characterized by a TANK with varying volume and state conditions First the physical characteristics of the tank must be defined This is accomplished by defining two of the three following parameters 1 Cross section area CSA 2 Maximum level 3 Maximum volume In our case we will define the CSA and maximum

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