Process Simulation and Control Using Aspen - Ebook download as PDF File .pdf ), Text File .txt) or read book online. Process Simulation and Control Using. Process Simulation and Control Using Aspen - Ebook download as PDF File .pdf ), Text File .txt) or read book online. About The Book Process Simulation And Control Using Aspen To overcome these challenges, various process flow sheet simulators are used. Tags: Process Simulation And Control Using Aspen™ by Jana Amiya K. Chemical Engineering Biochemical Engineering Chemical Engineering.
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Download Process Simulation and Control Using Aspen. Process Simulation and Control Using Aspen. a .. unit operations, we are able to develop aprocess flow diagram (PFD) for a complete plant. Process Simulation and Control Using Aspen by Amiya K. Jana, , available at Book Depository with free delivery worldwide.
When was the Company Founded?. REquil model solves stoichiometric chemical and phase equilibrium equations. The user can define the reaction kinetics in Fortran subroutine or in excel worksheet. RGibbs solves its model by minimizing Gibbs free energy.
Apart from these solved examples. One of the most important things to remember when using a computer simulation program. The yield reactor. The stoichiometric reactor. Eor these three reactor models. RPlug and RBatch. They are RStoic.
On the other hand. For this reason. For single-phase chemical equilibrium or simultaneous phase and chemical equilibrium calculations. RPlug and RBatch handle rate. Choose Template option and then click OK. Using the Peng-Robinson thermodynamic method. Simulation approach As we start Aspen Plus from the Start menu or by double-clicking the Aspen Plus icon on our desktop. The reactor operates at oC and 1. Copyrighted materia. Here we consider an irreversible reaction given as: We can use the fractional conversion of ethylbenzene equals 0.
Select the Reactors tab from f f blank Process Flowsheet Window. Connect to Engine Server type: Working directory: Note that this step is specific to the installation. In order to connect the feed and efluent streams f. I [5'. Addmg the outlet stream to the reactort tJXwa WW. S -O-M-i o - a Ri astt. Remember that red a f ' arr0WS are re luired blue arrows are optional ports. Click once on the starting point.
BM Bi. Select the components from the lists and then Add them. A detailed procedure is presented in Chapter 1. Now ill out the table for three components.
If Aspen Plus does not recognize the components by their IDs as defined by the user. Entering the values for state variables temperature. Specifying operating conditions for the reactor model. We can also run the simulation by selecting the Run button in the toolbar this is the button with a block arrow pointing to the right. If the simulation has converged it should state.
If we click on Stream Table knob just above the results table. It implies that all required input information have been inserted by the user. There are a few ways to.. We could select either the Next button in the toolbar which will tell us that all of the required inputs are complete and ask if we would like to run the simulation.
After the simulation is run and converged we notice that the Results Summary tab on the Data Browser window has a blue checkmark Clicking on that tab. Pressing Next button and then OK. Rucloi Chsnga. MO tnut iulmtiu imi. Proqr-5R Pi les'AspenTech. Aspen Plus CM Thu jul 5. Mone Flow basis for Input: Kole Stream report cooposltlon: Fllep e Ci '. AppMtaMocal Terep -ape TABLE 2. The reaction is irst-order in aniline and hydrogen. Simulate the CSTR model and compute the component mole fractions in both the liquid as well as vapour product.
When the Connect to Engine dialog appears. The reaction rate constant is defined with respect to aniline. Click OK in the above screen. Creating flowsheet Adding inlet and product streams and renaming look like Figure 2. None Bow oss crinpiif 'tee Strtom eaai cwrpcttEfi: Propetty I lhod. I Beetle. Mf RGte. For the sample reactor model. They are aniline. Defining all these species in the component input form.
For Stream A pure aniline and Stream H pure hydrogen. Ittieiwj nH-clalsKM! Providing required information for the CSTR block. Ifflll I r-M- r T 71 ' I. I M Hi Setup Solsd. Vttyfcw Hdp MHl r. In this form. The exponents represent the order of the reaction with respect to each. As we click on New. Note that there are two types of reactions [kinetic rate-controlled reactions and equilibrium] permitted under Power law reaction ID.
In Figure 2. In the subsequent step see Figure 2. As we ill up the form. Aspen Plus takes a default value of zero. Reaction type: Notice that when the Arrhenius formula is used know. Here we use the Arrhenius law to represent the reaction rate constant. It is. If To is ignored. T the temperature m degree K Tn the datum temperature in degree K. K the reaction rate constant kinetic factor in Aspen Plus terminology. In the window shown in Figure 2 S t fSTI.
The vaporized benzene pure with a low rate of The data for the Arrhenius law are given below Forward reaction: Reverse reaction: The elementary reversible vapour-phase reaction occurs in a plug low reactor PER. It operates at inlet temperature. When the Aspen Plus window pops up. Copyrighted material.
HCSTB f lfy q.. Expanding the RPlug icon. Configuring settings message directs us to provide the input information. Hitting Next knob and clicking on OK, we obtain a form for setup specifications. First we input the Title of the present nroject Simulation of the RPlug Model , followed by the accounting information.
From the Data Browser, select Specifications under the Components folder. As we provide the chemical formula of the components in the Component ID column, the other columns of the table are automatically filled up see Figure 2.
Open the Configuration sheet and enter the reactor dimensions in the next form see Figure 2. T the subsequent step, we define a reaction set for the simulation. The default name R-l. Hitting Afof button and clicking on New we have the following forms see Figures 2. Since the reaction rate constants are defined with respect to benzene we convert the stoichiometric coefficient of benzene ,. As mentioned previously, when we do not specify the exponent for a component Aspen Plus uses a default value of zero.
As the message on the screen, shown in Figure 2. Subsequently provide the stoichiometric coeficients along with ex ponents, shown in Figure 2 If fo is not specified. To apply the Arrhenius law. For the prescribed reactions. Click on Solver Settings knob.
Click on Next icon and get a variety of plots see Figure 2 F z Utt Sutra. Hji H i. Qg RGtfc. Figure 2. Hitting Finish knob. Choose Template option and press OK. The sample adiabatic PFR is 3 m in length and 0. The kinetic data for the Aspen Plus simulation are given below. Take a very large negative value for coeficient A. From the Model Library toolbar we have selected RPlug reactor and developed the process low diagram as displayed in Figure 2.
For the present problem. VAmtow 3ip o a! IGEN M. Pfcu 8. I etod. Inputting the values for temperature. I jn Uia. Specify the reactor as an adiabatic one.
HUM fW Ki rtsi muc s r. Similarly under Products.. Under Reactants. Similarly for products set ketene and methane exponents to 0 Also enter zero for all four driving force constants as mentioned in the.
The LHHW rate expression is represented by: N the number of components a the concentration exponent. The kinetic factor reaction rate constant has the following form: Providing required data we have the illed kinetic sheet shown in Figure 2. Click on Driving Force to obtain a blank form as shown in Figure 2. The driving force is expressed by: B'Mt 'CM Wto. SbMM F. Subsequently run the simulation and obtain the status report as displayed in Figure 2 The reactor operates at 70oC and 1 atm.
Forward reaction: Probably the most useful kinetic models. A number of problems are given in the exercise for extensive practice. For these liquid-phase reactions.
Both the reactions are first-order with respect to each of the reactants i. The following elementary irreversible vapour-phase reaction is performed isothermally with no pressure drop. If require. The irreversible elementary vapour-phase reaction is given as: The reactor operates at 10 atm and 50oC. The reactor operates at 80oC and 1 atm. Using the NRTL property method.
The reactor is operated isothermally at inlet temperature. Use the SYSOP0 property method and assume the following component-wise low rates in the feed and product streams see Table 2. Scott New Delhi H. Prentice-Hall of India.
Elements of Chemical Reaction Engineering. The reactor with a volume of 1. PA the partial pressure of A. MultiFrac is usually employed for any number of fractionating columns and any number of connections between the columns or within the columns. Note that Extract model is used for liquidliquid extraction. It also calculates the optimal feed tray and reboiler as well as condenser duty. Distl and SCFrac represent the shortcut distillation and the rest of the distillation models perform igorous calculations.
Remember that this model assumes constant molar overflow and relative volatilities. We need to specify a number of stages. RateFrac and BatchFrac. Distl model includes a single feed and two products.
It has a wide variety of appUcations. It estimates minimum number of stages using Winn method and minimum reflux ratio using Underwood method.
It uses Edmister approach to calculate product composition. RadFrac is a rigorous fractionating column model that can handle any number of feeds as well as side draws. Among the built-in column models. DSTWU model uses Winn-Underwood-Gilliland method for a single-feed two-product fractionating column having either a partial or total condenser. In the Aspen terminology.
Under these categories. It has the ability to simulate the distillation columns integrated with flash towers. It simulates a distillation. Simulation approach From the desktop select Start button and then click on Programs. BatchFrac is a rigorous model used for simulating the batch distillation columns. It also includes the reactions occurred in any stage of the separator. It is worthy to mention that for detailed information regarding any built-in Aspen Plus model. BatchFrac model does not consider column hydraulics.
The sample process operates at psia with zero tray-to-tray pressure drop The pressure. RateFrac is a rate-based nonequilibrium column model employed to simulate all types of vapour-liquid separation operations. In addition to the steady state simulation the process optimization will. It is used to model refinery columns. SCFrac is a shortcut column model.
This rigorous model simulates the refinery columns. In this chapter. It simulates single and interlinked columns with tray type as well as packed type arrangement. This rigorous column model can be used as an alternative of PetroFrac.
Hit OK knob and move on to develop the process low diagram f. Here we choose T. Aspen Plus. User Info Node name: By default. As we know.. AM ru. As we move the cursor a crosshair onto the process lowsheet. To add a single feed stream and two product outlets distillate and bottom. In the similar fashion. When inished. Once we have selected the icon. This happens because of improper flowsheet connectivity.. H-t MiBl alal lei 1 ni-rlftl Nkl H li! Stream 2 to D.
Although optional. Configuring settings Recall that within the Aspen simulation software. Project ID: Aspen Plus may spontaneously ill up the Type Component name and. Rahjiac BalchFrae r: The otherT three columns have been automatically filled out. For fluid processing of organic chemicals. A Component ID is essentially an alias for a component It is sufficient to use the. Component name and Formula. He Ed! Specifying block information i t under Blocks folder.
As a result.. It is fairly true that we can alternatively specify the reflux ratio when the number of stages is asked to compute. Entering all these information. As mentioned in the problem statement. Note that ethylene is the light key and naturally ethane is the heavy key.
Simply press Next button and receive a message regarding th present status see Figure 3. Viewing input summary f f f If we wish to have the input information. In the following Figure 3. We can name the ile whatever we like. ETWlENt 0 4. Aspenrechvworklng working foIi FoldersVupen plus Directory c: JULY F PSI.
TEMP F Simulation of a RadFrac Model Problem statement We will continue the above problem with few modifications. Consider the RK-Soave property method. If yes. The distillation process that has total 68 theoretical stages including condenser and reboiler and a total condenser operates at psia with zero pressure drop throughout. The distillate rate. In the comparative study for part b. A hydrocarbon stream. Connecting feed. When the Connect to Engine dialog pops up.
These two windows. Mote ' P Moio. Mftl yJ nWkfoKM 1 til. Using the component names. Soave base method to compute the physical properties see Figure 3 Inserting the given values for the feed stream.
Fill up. Figure 3. Aspen simulator assumes that the column operates isobarically if no additional pressure information is provided see Figure 3. Save the work in a folder as a ile. From Tables 3. Another possibility is the round-off error associated in the reflux ratio and feed tray position. Copyrighled malarial. TABLE 3. Mie'-io-un 10 t cavit 'i-. Apply the Peng-Robinson correlation and consider psia pressure throughout the column.
A hydrocarbon feed mixture enters above tray 10 of the RadFrac column. Problem statement A multicomponent distillation column. Now the process lowsheet is complete.
In Figures 3. Then hit OK see Figure 3. Creating flowsheet At present. Remember that this step is specific to the installation. The Status bar in the bottom ight of the screen. Copynghied material. Filling out the Component ID column. This equation of state model is chosen for thermodynamic property predictions. In the problem statement. Entering the values of all state variables and component mole fractions.
SalcbFiK Aspen Phis. J'j gaafwe i. If we wish to see the tabulated results with the process low diagram in a single sheet. SI ' 20 t T. Nola Strcan report cowposlclon: Btu hr. The tower has two pumparound circuits. A steam stream. The condenser f f runs at Then the user can easily modify the title. There are another three steam streams. The tower pressure drop is equal to 4 psi. The outlet stream of the furnace goes to the tower on Stage I-h HI I. Select a model icon and press Fl to know more about that.
L - EJ J-J. As we expand the PetroFrac block icon. The next screen presents a blank process lowsheet. Creating flowsheet Select the Columns tab from the Model Library toolbar. Adding all incoming and outgoing streams and renaming the streams as well as block. Then place it in the flowsheet window. In the Title field. Open the Accounting sheet keeping untouched the other global defaults set by Aspen Plus.
I'M MI i l"! Filling out the component input form.. Figure In the list on the left shown " Figure 3. After illing out.
Minodi j. Bwct fiac. Rwftw c. SD 3fl. P fix. HMik '. ManpUstco Soldi j liieiModd! BrfrK E-trwt. As given in the problem statement enter 0. Jfl STBI nw i. Himdl ' in I-Wav. O ii Slriivm SI. Click on New as the object manager appears. M Mar cou-t. By the same way. The Control Panel window is presented in Figure Save the work done. When Aspen Plus window pops up.
The column operates at 75 psia with no pressure drop and it has four equilibrium stages. Apply the Peng-Robinson equation of state compositions. The absorber is specified in Figure 3. Connecting the inlet and we have Figure d. NC10Overall rangeLower: This screen isused by Aspen to set up tables. Insert T under Column No.
Then right click on theadjacent cell under Tabulated variable or expression. Select Variable List and drag anddrop the variable name C3 into the cell. We may also directly type '03' in the cell. Then run the simulation and get the screen, shown in Figure 3. By the similarway. J-T I-1 l- iv i-g I i Mfc. Then enter 'CS' as a variable name and press OK. Inthe next step see Figure 3. Design specificationdata are noted below: NC10Manipulated variable limitsLower: The maximum C3 mole fraction of 0.
Several separating columns, including a petroleum refining columnand an absorber,have been simulated using Aspen Plus. The process optimization hasalso been discussed with an example.
The present study covers both the binary as wellas multicomponent systems. Interested readers may try to simulate the models givenin the exercise. The columnoperates at 1 atm with no pressure drop throughout. In the simulation, considerthe reflux ratio of 1. Applying the Wilson property method,simulate the column and find out the minimum number of stages, actual numberof stages, and feed position.
This separatorruns at psia with no tray-to-tray pressure drop. The pressure in the reboileras well as condenser is also psia. The feed enters the model at 6th stage andthe column has total 15 theoretical stages including condenser and reboiler and a total condenser. If the reflux ratio is 7 and the distillate to feed ratio is0. The column consists of total 24 equilibrium stages includingcondenser and reboiler with a stage pressure drop of 2 kPa. Consider thecondenser total pressure of kPa and the top stage Stage no.
A side product vapour is withdrawn from 14th stage. It has total 6 stages including condenser and reboiler and no condenser. Dj OSj cC. The schematic diagram of the process with feed specifications is givenin Figure 3. The process unit, having toted five stages, is operated adiabatically. The column operates at 1 atm throughoutand it has four stages.
Using the UNIFAC thermodynamic model, a simulate theRadFrac absorber ABSBR2 and determine the exiting ammonia concentration inthe gas product, b Perform the sensitivity analysis by examining the effect ofabsorbent flow rate on the exiting ammonia concentration in the top product.
The tower includes one pumparoundcircuit, a partial condenser and one side stripper. The outlet stream of the furnace enters the tower on stage The column has total 20 stages. There is another steamstream, STEM1, used in the side stripper. The condenser runs at 15 psia with apressure drop of 5 psi. The tower pressure drop is equal to 5 psi. A hydrocarbon mixture with the given component-wise flow rates Table 3.
TABLE 3. Here, by a 'chemical plant' we mean a chemical processintegrated with several single process units. The chemical process industries usuallyinclude flash chamber, mixer, splitter, heat exchanger, pump, compressor, reactor,fractionator, filter and so on. It is easy to simulate even a large chemical plant by theuse of Aspen software package.
In the present chapter, the simulation of two chemical process flowsheets isdiscussed. They are a distillation train and a vinyl chloride monomer VCM manufacturing unit. After thoroughly reading this chapter and simulating the solvedexamples in hand, we will be able to use Aspen Plus flowsheet simulator for solving awide variety of chemical plants. To improve the flowsheet simulation skills, it isrecommended to solve the problems given in the exercise.
The pump Pi discharges thefeed F at 10 atm.
In Table 4. TABLE 4. For the light key LK and heavy key HK , we expect Using the Peng-Robinson property method, simulate the distillation train and report the compositionsof all distillation products.
Based on theunits used in the problem statement,we select General with Metric Uliits,. Actually, this step is specific to our installation see Figure 4. User name;Password;Working directory: Add a pump by selecting thePressure Changers tab from the Model Library toolbar. Moreover, in the library, selectthe Columns tab and then choose DSTWU model to include five such columnsconsecutively on the flowsheet.
Notice that to incorporate a block,click on theappropriate icon and then place the block on the process flowsheet by clicking with thecross hairs somewhere on the flowsheet background.
Right click to de-select the block. Now we need to interconnect the blocks and add the inlet as well as outlet streams. In the next, as wemove the cursor to the process flowsheet window,several red and blue arrows appeararound the blocks. The red arrows indicate required streams and the blue arrows areoptional. In the previous chapters, we have learned how to connect the feed and productstreams with a single block. Let us observe Figure 4. Here, first we wish to interconnect the pump PI with the column Cl using the feedstream F.
Right-click with highlighting feed block,select Reconnect Destination andthen move the cursor to click on an arrow that is fed to the column Cl. Renaming all blocks as well asincoming and outgoing streams, finally we have the screen shown in Figure 4. Torename a particular stream or block , first select it, then right-click, next select RenameStream or Rename Block and finally enter the appropriate name.
Remember that in the Data Browser, we need to enter information using data inputforms at locations where there are red semicircles. As we finish a section, a bluecheckmark appears. In the Tattle field, enter 'Simulation of a Distillation Train'. Aspen software provides an option tochoose different property methods for different processes. To do so, select Block Options! Properties under a particular model of Blocks folder in the list on the left and thenchoose the suitable property method.
Entering the given data for stream H, we obtain the sheet as shown in Figure 4. The deethanizer column is specifiedwith the given data as shown in Figure 4. Running the simulationAs we approve the simulation run, the Control Panel, displayed in Figure 4. Jt mu tjxll huz - jjtkt: The mixer outlet Fl then goes to thereactor B2 run at K and 1. The outlet stream F3 is then condensed fully to liquidphase in block B4 at K before being pumped to an evaporator. The pump B5 hasdischarged the liquid at 26 atm.
The evaporator B6 performs the phase change operationand then the vapour temperature is increased in the same unit to K. In thesubsequent step, stream F6 is introduced in the reactor B7 RStoic in which thefollowing pyrolysis reaction occurs: To reduce carbon deposition in the heat exchanger,the hot vapour stream leaving the reactor is quenched in block B8 yielding a saturatedvapour stream at K.
The first column mainlyseparates HC1 from other components, while the second column purifies VCM from therests. Both the distillation columns have 10 theoretical stages including condenserand reboiler and a total condenser along with the specifications,shown in Table 4.
A purge stream is introduced to prevent accumulationof unreacted components. In the next, selectPolymers with Metric Units see Figure 4. I -i-. Creating flowsheetWe can develop the process flow diagram see Figure 4. The status message directs us to provide the input information required to run thecomplete Aspen Plus simulation program.
In the subsequent sections, we will fill upseveral input forms one by one. In the following,the first screen,shown in Figure 4. EO Option.
Jjpntttn djiso P dTotal How Ma;-. I gj rj -claKI -t. Ccfcint0rmStream Bu! O tf to 1 -Jlr. Sincethe data entry is fully complete, the simulator seeks user permission to run the program.
It usually shows errors, warnings, convergence status, etc. Save the work positively at this moment. In the present chapter, several chemicalprocesses have been assembled to develop the chemical plants and those plants havebeen simulated subsequently.
The solved examples include a distillation train and a vinylchloride monomer unit. In the second example, the loop is closed by a recycle stream,whether in the first unit, there is no such complicacy.
However, the straightforwardapproach to simulate a flowsheet is that after developing the process flow diagram in theflowsheet window of Aspen Plus, we can simply use Next button for data entry. As wereceive the message of Required Input Completey we can move on to run the simulation.
In the next two chapters, we will study the process dynamics and closed-loop control offlow-driven as well as pressure-driven processes using Aspen Dynamics package. The compressor has discharged thevapour stream at 3 atm. The flash drum Flash2 runs at F and 2. The stripper STRIP2 has total 6 stages including condenser and reboiler and bottoms tofeed ratio mole basis is 0. The feed stream to the stripper is introduced abovethe top stage and the pressure throughout the column is 2 atm.
TABU 4. The top stage pressure of the stripper is psiawith a stage pressure drop of 0. Stream Dl enters below th stage. In the simulation,consider condenser pressure of psia with a pressure drop of 5 psi and astage pressure drop of 0. For the liquid-phase reaction, the inlet streams have thespecifications, shown in Table 4. Data for the Arrhenius law are given as: The reaction is first-order in aniline and hydrogen.
The reaction rate constant is defined with respectto aniline. Simulate the process and compute the component mole fractions inthe liquid product and the vent stream.
The overhead vapour iscondensed and then separated in the decanter into two liquid phases: A feed stream, namely FEED, enters above 15th stage of the azeotropic distillationcolumn at oF and 90 psia in addition to the flow rates, shown in Table 4. The azeotropic column RadFrac has the following specifications: Number of stages including condenser and reboiler: The pump has discharged theliquid feed F at 5 atm.
The component-wise flow rates are shown in Table 4. The specifications, shown in Tables 4. Stream H has component-wise flow rates,shown m Table 4. B 'm-! PVil i. Filling out the table with the components acetic acid, ethanol, ethyl acetate andwateri involved in the present reaction system, the screen looks like Figure 5.
IMM -. As shown in Figure 5. Specifying the FEED stream by its temperature, pressure, flow rate andcomposition, we have this window, shown in Figure 5. It is filled with the given data as shown in Figure 5. Vessel sheet under Blocksfolder and enter the reactor geometry data.
J l-i I IT. Running steady state simulationAs we click on Next button to continue the simulation, the Required Input Completedialog box appears. Hitting OK on the message, we are displayed the Control Panelwhere the simulation messages during the run are recorded see Figure 5.
Loop 1Controller: LCIType of controller: TC2Type of Controller: On the other hand, as the input signal to the controlstructure increases, the output signal from the controller must decrease for the case ofreverse acting control strategy. In Aspen terminology, the process variable or controlled variable is denoted by PV,the set point is represented by SP and the controller output or control variable ormanipulated variable is abbreviated by OP. For the example CSTR system, level and temperature controllers are automaticallyimplemented when the Aspen Dynamics simulation is created.
To achieve better closed-loop process response, the Aspen-generated control structures can be modified or evenreplaced by the suitable control schemes available in the control library of Aspensoftware. In addition, the default values for controller tuning parameters, such as gain,integral time,derivative time,and so on, can also be changed. Most of the control strategies are easily tuned by simply using heuristics.
Assuggested by Luyben ,all liquid levels should use P-only controllers with a gainof 2. All flow controllers should use a gain of 0.
The author also mentioned thatthe default values in Aspen Dynamics for most pressure controllers seem to workreasonably well.
But temperature controllers often need some adjustments. Viewing default values of variablesIn Aspen Dynamics, the steady state values of process variable and controller outputar displayed in a table. To show the results table ofloop I, highlight the controller block LCI, press the right mouse button, go to Formsand then select Results. But as a difference, the units are not mentioned herewith the values of SP.
PV and OP To doso for the level controller, highlight the controller block LCI, press the right mousebutton, point to Forms and then select Configure see Figure 5. J weie elmir. The reactor liquid level is the PV for loop 1 and reactor temperature forloop 2. From the results tables shown earlier, it is obvious that the error is zero for both loops. Therefore, Aspen Dynamics has set the value of OP as the bias value.
However, as mentionedpreviously, the proportional-only controller with a gain of 2 is sufficient to effectivelycontrol the liquid level. Remember that to make the integral action inactive, we canuse a very large value, for example minutes even the default value of 6 x minutes may also be accepted , for the integral term.
For loop 1, the controller actionshould be 'Direct' as set by default see Figure 5. Wggg [ ' Adotoc Vrote P. It may be practical to consider thefollowing constraints. Process variableRange minimum: In the next, the controllerperformance will be examined in terms of set point tracking servo and disturbancerejection regulatory.
Before running the program, we must be accustomed withsome frequently used items of the toolbar as described in Figure 5. Then select Pause at time, type 5 in the field or whatever we want andclick on OK see Figure 5. O -jj j ' fnci cil C-S i. In thenext, press on Configure and Plot symbols in the faceplate. Alternatively, to open thefaceplate. Configure dialog box and ResultsPlot dialog box, first select LCI block, thenchoose Forms and subsequently press one-by-one on faceplate, Configure and ResultsPlot,respectively.
Judiciously arrange all three items within the Aspen Dynamics window see Figure 5. Eiaagi ' 'i Baaaa wpw-!. In order to execute the dynamic closed-loop simulation, click on Run button inthe toolbar. During the simulation run, give a step change in the set point value ofreactor liquid level from 0.
Typing the new setpoint value in the faceplate, press Enter button on the keyboard so that the Operatorset point value in the Configure dialog box also changes automatically to 1.
Thus we can say that loop 1 affects loop 2. In Figure 5. Before starting the simulation run, carefully check all entries in thefaceplate as well as Configure dialog box. In the next, choose Initialization run mode inthe toolbar and then run the program once. After completion, go back to Dynamicmode from Initialization mode see Figure 5. As stated, if the performanceof any controller is not satisfactory, we have the option to tune the parameters simplyby trial-and-error method. If we introduce a set point change in the reactor temperature, the TC2 controllertakes necessary action with adjusting the heat duty to compensate for the changes.
But interestingly, the liquid level remains undisturbed. Figure 5. At this point we can conclude that loop 1 affects loop 2, but loop 2 does not affect loop 1. Actually here the interaction is in a single direction.
To perform theregulatory study, we need to introduce at least a single change in the inputdisturbance. However, here we consider two subsequent step changes in thefeed temperature.
To change the feed temperature twice as prescribed above, first we need to openthe feed data sheet by double-clicking on the FEED block in the process flowsheet see Figure 5.
As it isfinished, go back to Dynamic mode. Then, open the plot sheets for both the controllers. The regulatory behaviour is illustrated in Figure 5. For brevity, the faceplate and configure dialog boxincluded in the Aspen Dynamics window, shown in Figure 5. On the other hand, the reactortemperature is disturbed. However, the TC2 controller provides satisfactory disturbancerejection performance under this situation. So far we have studied mainly the closed-loop behaviour of a reactor system coupledwith Aspen-generated control schemes.
We did not include any additional controller withthe CSTR model. In Section 5. In Table 5. It is fair to use an aspect ratio length to diameter ratio of2 Luyben, TABLE 5.
Use default values for other tray hydraulic parameters e. Consider log-mean temperature difference LMTD assumptions for the total condenser. Actually,theLMTD is calculated using the temperatures of process fluid and coolant. In the simulation. Keeping the default level and pressure control algorithms unaltered, inspectthe servo as well as regulatory performance of a proportional integral PI1controller that is required to insert to control the benzene composition in thedistillate by manipulating the reflux flow rate.
Devising an another PI control scheme to maintain the benzene composition inthe bottom product with the adjustment of heat input to the reboiler, observethe interaction effect between the top and bottom composition loops. To open the process flowsheet window, clickOK when the Aspen Plus engine window appears. Creating flowsheetFrom the Model Library toolbar, select the Columns tab. Place the RadFrac model onthe flowsheet window and add the feed as well as two product streams.
Renaming allthe streams along with distillation block, we have Figure 5. The diHtillation problem Is tilled oh: We can fill up theAccounting sheet with any name, number and ID. Specifying stream Information," next,.
Vessd geomstiyHeadlypei Lengtlk: DiwneteiIniialspdcificabon5 fl z25 ft z. We already have inserted the necessary information for stages 1 and Now, we need to inform the simulator the tray geometry specifications for stages2 through Note that the tray holdups are computed using these geometry data see Figure 5. Finally, the result. At this time, we should save the work.
Then close the Aspen Pluswindow. As we drag it onto the flowsheet window, many blue an-owappear around the process diagram. Interestingly, when we f l I Z S. To select the dastillate compos.
Obviously, the CCT controller is partiallyconfigured. To complete the top composition loop, the controller output should beconnected with the manipulated variable to pass on the signal. B V Ovn. So,double-click on the CCT block andthen hit Configure symbol in the faceplate to open the Configure dialog box see Figure 5. For example, the operator set point value of process variable benzene composition indistillate should not be greater than L Secondly, the CCT controller action must be'Reverse'.
In addition, the value of control variable reflux flow rate at steady state isusually used as bias value. We have two options in our hand to correct the default values. Either manuallywe can do it or Aspen Dynamics can automatically initialize the values of set point,process variable, control variable, bias and ranges. Note that the controller action ischanged only manually. It is wise to initialize the values by the help of Aspen Dynamics.
For this, press Initialize Values button in the Configure dialog box and use 'Reverse'controller action. It is obvious in the window, shown in Figure 5. Ifthis approach fails to initialize the simulation of controller model with the steady statedata, check and replace, if necessary, the values of PV and OP with their steady statevalues by double clicking on signal transmission lines input to the controller and outputfrom the controller. We have now completed all required control specifications for the top compositionloop In the ongoing study, we prefer to conduct the simulation experiment to observethe designed controller performance continuously for 5 hours.
In the next, we will inspect the CCT controller performance first dealing with theservo problem followed by the regulatory problem. Then open the Configure as well as ResultsPlot dialog box. The second one isbasically a blank graph sheet that presents the variations of process variable, set pointand controller output with respect to time.
Before running the program, make sure that all the items in the Configure dialog boxand faceplate are correct. In the next,hit Run button to start the dynamic simulation. Theplots, shown in Figure 5 70, illustrate the servo behaviour of the PI control algorithm witha step increase 0. These values have been chosen basedon a pulse input test in the distillate composition of benzene and using the trial-and-error approach It should be kept in mind that the objective at this point is not to comeup with the best control structure or the optimum controller tuning.
We only need acontrol scheme and tunings that provide a reasonably good tracking performance todrive the simulation to a new steady state. Remember that to edit the plots, shown in Figure 5 70, double-click on differentelements of the plots and modify them as we like.
The PI controller tuning set provides gooddisturbance rejection performance see Figure 5. TIM mmm liatl A I.. EkMIMi "1. The simulation result isdepicted in Figure 5. It is observed from Figure 5. Similarly, when any setpoint change is introduced in the top composition loop, the bottom product compositionwill also be affected.
To observ e the controller performance in terms of set pointtracking and disturbance rejection, a CSTR in addition to a distillation column havebeen illustrated The default control strategies have been tested for the reactor example,whereas the two additional composition control loops have been included along withthe default control laws for the distillation example.
Several simulation experimentshave been executed for both the processes under flow-driven dynamic simulation.
Notethat Chapter 6 presents the dynamic simulation and control of more rigorous pressure-driven dynamic process. Theseparator operates at 1. For dynamic simulation, required feedspecifications are provided in Figure 5. The superheated steam is used as a heating medium. Complete specifications required for closed-loop dynamic simulation are shown inFigure 5.
In the closed-loop simulation experiment, assume that thetemperature sensor takes 1 minute time dead time to measure the controlledvariable.
Report the used tuning properties. The output of the ratio element is sent to a ratio controller PI thatcompares the calculated ratio Rm to the desired ratio Rd set point and adjuststhe manipulated flow rate accordingly.
Double-click on Input 1 transmission line and fill up Tables 5. It has total 6 stages including condenserand reboiler and no condenser. The diameter of the stripper Stages 1 to5 is 6. The reboiler heat duty is assumed constant, although it changes atdynamic state. The sump has elliptical head with a height of 5 ft and diameterof 2. For the closed-loop simulation, use the following data: Use the givenclosed-loop data and execute the dynamic simulations to test the developedcomposition controller performance.
Theirreversible elementary vapour-phase reaction is given as. Considering themeasurement lag of 1 minute, inspect the servo as well as regulatory controlperformance. Report the tuning properties used to achieve a satisfactoryclosed-loop performance.
Therefore, phenol is used as an extractant and introduced abovetray number 7 of the column. The two input streams have the followingspecifications,shown in Table 5. The distillate rate and reflux ratio are given as The pressure profile is defined with Stage 1pressure of 1 bar and Stage 22 pressure of 1. Thereflux drum and sump are specified in Table 5. Seborg, D. Edgar and D. Mellichamp, , Process Dynamics and Control,2nd ed. It is well-recognized that Aspen Dynamics is such an efficientflowsheet simulator used for dynamic process simulation.
As we have seen in Chapter 5,Aspen Dynamics simulator can be employed to design a process as well as its associatedcontrol strategies. Aspen Dynamics extends an Aspen Plus steady-state model into a dynamic processmodel. If the steady state Aspen Plus simulation is exported to Aspen Dynamics, thereis a necessity to choose either flow-driven dynamic simulation or pressure-drivendynamic simulation.
In a rigorous pressure-driven simulation, pumps and compressorsare inserted,where needed, to provide the required pressure drop for material flow. Control valves are installed,where needed, and their pressure drops selected.
For goodcontrol, the pressure drop across a control valve should be greater than 0. Thefluid that flows through a valve should normally be liquid-only or vapour-only becausethe two-phase flow through a control valve is unusual.
It should be pointed out that for a pressure-driven case, we must not insert a valvein the suction of a pump or at the discharge of a compressor compressor speed or itsequivalent compressor work is manipulated. The control valves are positioned on thefluid streams such that the controllers can manipulate the valve positions. The simple flow-driven dynamic simulations have been discussed in detail in theprevious chapter. Therefore,here we are intended to study the pressure-drivensimulation.
A reactive or catalytic distillation column is exampled for the rigorouspressure-driven Aspen Dynamics simulation as well as control. The RD column RadFrac consists of 17 theoretical stages, including a total condenserand a partial reboiler. Reactive stages are located in the middle of the column, Stage 4down to and including Stage A Component ID is essentially an alias for a component It is sufficient to use the. The otherT three columns have been automatically filled out.
Pr0Perty input f0rm er hit Next icon or choos. Here, we have to provide the values for all state variables temperature, pressure and total flow and composition component mole fractions. Filling out the form, shown in Figure 3. Under Column specifications option, here we enter the number of stages that is It is fairly true that we can alternatively specify the reflux ratio when the number of stages is asked to compute. Note that ethylene is the light key and naturally ethane is the heavy key.
In addition, the pressure of the total condenser and reboiler is given as psia. Entering all these information, one obtains the result, shown in Figure 3. The Status message includes Required Input Complete indicating that we are in a positio to run the simulation. Simply press Next button and receive a message regarding th present status see Figure 3.
Click OK on the above message and obtain the Control Panel window that shows the progress of the simulation see Figure 3 In the following Figure 3.
We can name the ile whatever we like. Viewing input summary f. Creating report file To create a detailed report on the complete work we have done including input ,. Then save the work as a report file e.
Ill, ii FAR F PSI. TEMP F A hydrocarbon stream. In the comparative study for part b. The distillate rate. Simulation of a RadFrac Model Problem statement We will continue the above problem with few modifications. If yes. Consider the RK-Soave property method. The distillation process that has total 68 theoretical stages including condenser and reboiler and a total condenser operates at psia with zero pressure drop throughout. When the Connect to Engine dialog pops up. Connecting feed.
These two windows. Mftl yJ nWkfoKM 1 til. Mote ' P Moio. Using the component names. Soave base method to compute the physical properties see Figure 3 Inserting the given values for the feed stream.
Figure 3. Fill up the Configuration sheet as shown in Figure 3 Aspen simulator assumes that the column operates isobarically if no additional pressure information is provided see Figure 3. Save the work in a folder as a ile. TABLE 3. From Tables 3. Another possibility is the round-off error associated in the reflux ratio and feed tray position. Copyrighled malarial. Mie'-io-un 10 t cavit 'i-. A hydrocarbon feed mixture enters above tray 10 of the RadFrac column.
Apply the Peng-Robinson correlation and consider psia pressure throughout the column. Problem statement A multicomponent distillation column. The Status bar in the bottom ight of the screen. Then hit OK see Figure 3. Remember that this step is specific to the installation. Now the process lowsheet is complete. In Figures 3.
Creating flowsheet At present. Filling out the Component ID column. Copynghied material. This equation of state model is chosen for thermodynamic property predictions. Entering the values of all state variables and component mole fractions. In the problem statement. SalcbFiK Aspen Phis. J'j gaafwe i. If we wish to see the tabulated results with the process low diagram in a single sheet. SI ' 20 T. Btu hr. Nola Strcan report cowposlclon: Select the plot type under the heading of Temp and press Finish button to obtain a plot of Temperature 0F vs.
Recall that the above plot window can be edited by ight clicking on that window and selecting Properties. Then the user can easily modify the title, axis scale, font and colour of the plot. An artificial petroleum refining column PRC , shown in Figure 3. The tower has two pumparound circuits, a partial condenser and three side strippers. The furnace single stage lash type operates at f.
The outlet stream of the furnace goes to the tower on Stage A steam stream, STEAM, is introduced at the bottom of the ractionator 26th stage with on-stage convention. The condenser f f. The tower pressure drop is equal to 4 psi. A hydrocarbon mixture with the following component-wise low rates enters the furnace at F and In Table 3.
Simulation approach. Select Aspen Plus User Interface. Click OK when the Connect to Engine dialog appears. The next screen presents a blank process flowsheet.
Creating flowsheet. Select the Columns tab from the Model Library toolbar. As we expand the PetroFrac block icon, a variety of models is displayed as shown in Figure 3. Select a model icon and press Fl to know more about that. Then place it in the flowsheet window. Adding all. Configuring settings Click Next to continue the simulation see Figure 3.
Open the Accounting sheet keeping untouched the other global defaults set by Aspen Plus. In the form, shown in Figure 3. Filling out the component input form, we have Figure 3. In the list on the left shown " Figure 3. Bwct fiac. After filling out.. Minodi j. SD 3fl. Rwftw c. ManpUstco Soldi j liieiModd! HMn 1' j. As given in the problem statement enter 0. P fix. HMik '. Jfl STBI nw i. BrfrK E-trwt.. Himdl ' in I-Wav.
O ii Slriivm SI. M Mar cou-t. Click on New as the object manager appears. By the same way.. Sffll 1 -. The Control Panel window is presented in Figure 3.
Save the work done. The absorber is specified in Figure 3. Apply the Peng-Robinson equation of state compositions. When Aspen Plus window pops up. The column operates at 75 psia with no pressure drop and it has four equilibrium stages.
Connecting the inlet and we have Figure d. Specifying property method In the list on the left. Copyrighted malarial.
In the input form. Enter the feed information for both the gas stream and absorbent in two forms as shown in Figures 3. Aspen software assumes that the column operates isobarically if no additional information is provided. Under Convention. Therefore the absorbent is fed above Stage 1 and the gas feed is introduced above Stage 5 see Figure 3.
Up Mai -I. In the present problem. On-Stage and Above-Stage. SCF P ff-t. The Control Panel window is Figure 3. SSffigB r-j. Enter 'C3' as ID. As the Object manager is displayed. Ow I M-MO.
Enter C3' and press OK. Then we are prompted to enter a variable name. Aspen prompts us for an ID. On the next window shown in Figure 3. This screen is used by Aspen to set up tables. Insert T under Column No. Mole-Frac Stream: C3 Hit Next and select the Vary tab see Figure 3. Then right click on the adjacent cell under Tabulated variable or expression. We may also directly type 03' in the cell. Mole-Flow Stream: MIXED data: NC10 Overall range Lower: Select Variable List and drag and drop the variable name C3 into the cell.
I'ICI I !? By the similar way. In the next step see Figure 3. We need to provide this design spec a name in the same manner that we did for the sensitivity analysis.
Then enter 'CS' as a variable name and press OK. Press New. Design specification data are noted below: C3 Target: It is well known that Aspen Plus is capable to optimize a function Here.
NC10 Manipulated variable limits Lower: This answer we can also obtain from the sensitivity plot. In the present study. Simulation approach First solve part a of the previous absorption problem It means.
Entenng variable name 'CS'. Under Variable number. T-Birry m. We can also simply type C3 in the field. Then select Variable List and drag and drop the variable name C3 into the cell see Figure 3 The maximum C3 mole fraction of 0. The present study covers both the binary as well as multicomponent systems Interested readers may try to simulate the models given.
The process optimization has. The pressure in the reboiler as well as condenser is also psia. This separator runs at psia with no tray-to-tray pressure drop. The column operates at 1 atm with no pressure drop throughout. If the reflux ratio is 7 and the distillate to feed ratio is compute the mole fraction of ethane in both the product streams with applying the RK-Soave equation of state model. The column consists of total 24 equilibrium stages including condenser and reboiler with a stage pressure drop of 2 kPa.
In the simulation. It has total 6 stages including condenser and reboiler and no condenser. A side product vapour is withdrawn from 14th stage.
Using the PengRobinson thermodynamic method. Consider the. Applying the Wilson property method. The feed enters the model at 6th stage and the column has total 15 theoretical stages including condenser and reboiler and a total condenser. The process unit. A flowsheet of a stripping column.
The schematic diagram of the process with feed specifications is given in Figure 3. The column operates at 1 atm throughout and it has four stages. A steam stream. The tower includes one pumparound circuit. The column has total 20 stages. A hydrocarbon mixture with the given component-wise flow rates Table 3. The condenser runs at 15 psia with a pressure drop of 5 psi. The liquid product.
There is another steam stream. The outlet stream of the furnace enters the tower on stage The tower pressure drop is equal to 5 psi. To improve the flowsheet simulation skills. The chemical process industries usually include flash chamber. The pump Pi discharges the feed F at 10 atm. It is easy to simulate even a large chemical plant by the use of Aspen software package. After thoroughly reading this chapter and simulating the solved examples in hand. In the present chapter.
They are a distillation train and a vinyl chloride monomer VCM manufacturing unit. Aspen Plus Simulation of Chemical Plants 4 1. C4 and C5 is shown in Figure 4. In Table 4. TABLE 4. For the light key LK and heavy key HK. Using the PengRobinson property method. Simulation approach From the desktop. Based on the units used in the problem statement we select General with Metric Uliits.
Now we need to interconnect the blocks and add the inlet as well as outlet streams. User name. Notice that to incorporate a block click on the appropriate icon and then place the block on the process flowsheet by clicking with the. In the previous chapters. Let us observe Figure 4.
Add a pump by selecting the Pressure Changers tab from the Model Library toolbar. Right click to de-select the block. Right-click with highlighting feed block select Reconnect Destination and. The red arrows indicate required streams and the blue arrows are. Renaming all blocks as well as incoming and outgoing streams. To rename a particular stream or block. The status indicator in the bottom right of the window.
As we inish a section. In the Tattle field. Remember that in the Data Browser. It is shown in Chapter 1 how to define components in the component input form. For the example. A property method includes the models and methods to calculate the physical properties.
Entering the given data for stream H. The deethanizer column is specified with the given data as shown in Figure 4. To do so select Block Options! Properties under a particular model of Blocks folder in the list on the left and then choose the suitable property method. Aspen software provides an option to choose different property methods for different processes. Click on Afert and specify the pump PI outlet by providing the discharge pressure.
OsHjw ] flaihOphor. But there is no such restriction that we cannot specify the process with more input information. Running the simulation As we approve the simulation run. Viewing input summary If we wish to have the systematic input information..
Jt mu tjxll huz.
Note that if we click on Stream Table. UK us - Tifi. Hm The flowsheet has been developed based on the VCM production technology reported in a book by Seider et al In this stoichiometric reactor RStoic. The pump B5 has discharged the liquid at 26 atm. To reduce carbon deposition in the heat exchanger. Both the distillation columns have 10 theoretical stages including condenser and reboiler and a total condenser along with the specifications shown in Table 4.
The first column mainly separates HC1 from other components. A purge stream is introduced to prevent accumulation of unreacted components. The mixer outlet Fl then goes to the. The evaporator B6 performs the phase change operation and then the vapour temperature is increased in the same unit to K. Light key LK The outlet stream F3 is then condensed fully to liquid phase in block B4 at K before being pumped to an evaporator.
Creating flowsheet We can develop the process flow diagram see Figure 4. The status message directs us to provide the input information required to run the complete Aspen Plus simulation program. In the following the first screen shown in Figure 4.
In the subsequent sections. C2H4 and CL2 which are fed to the mixer block Bl. Defining all species in the Selection sheet. In order to get a blank component input form. Figures 4. Selection] Pelidftum Noraiorivenliona!
Specifying stream information From the Data Browser. M -1 ""1 10 Ci. In the simulation of the reactor model coefficients should be negative for. The windows. FocHeto orevin C: MarjpOaioii Sold.
As stated earlier the flowsheet of the VCM plant consists of two mixers. For subcooled liquid and superheated vapour. To simulate a mixer model. Although discussed during the Aspen Plus simulation of different single process units in the preceding chapters. F3 Total IST tt. I l"l! OacW I. PorHato-MiFl Heat. Reactws j Pie-jyjie Char eis ] Mawpife! J[ Aspen Plus. Fus '. Aspen Plus displays a message as shown in Figure 4.
It usually shows errors warnings. Since the data entry is fully complete. BiO MT. The stripper STRIP2 has total 6 stages including condenser and reboiler and bottoms to feed ratio mole basis is 0. The feed stream to the stripper is introduced above f the top stage and the pressure throughout the column is 2 atm. The compressor has discharged the vapour stream at 3 atm.
CopyHghlod material. The solved examples include a distillation train and a vinyl chloride monomer unit. As we receive the message of Required Inpu t Completey we can move on to run the simulation. In the second example. The lash drum Flash2 runs at F and 2. The top stage pressure of the stripper is psia with a stage pressure drop of 0.
Stream Dl enters below th stage. TABU 4. Data for the Arrhenius law are given as: Simulate the process and compute the component mole fractions in the liquid product and the vent stream.
The reaction is irstorder in aniline and hydrogen. For the liquid-phase reaction.. The technique involves separating close boiling components acetic acid and water by adding a third component vinyl acetate. VA vinyl acetate. The azeotropic column RadFrac has the following specifications: Number of stages including condenser and reboiler: The overhead vapour is condensed and then separated in the decanter into two liquid phases: A feed stream. The component-wise low rates are shown in Table 4.
The pump has discharged the liquid feed F at 5 atm. The specifications. Stream H has component-wise flow rates. Process Design Principles: Lewin Wiley Interscience. Stream F6 enters the splitter FSplit B7 and 0. New Jersey. Before introducing into the reactor. Introduction to Chemical Engineering Computing. Seider and D. New York. Note that the reactor RGibbs B4 runs at oF and psia.
To convert a steady state simulation into a dynamic simulation there are several items that should be taken care of For example the size of all equipments must be specified and the control structures must be devised For steady state simulation using Aspen Plus the size of the equipment is not needed. When the steady state Aspen Plus simulation is exported into Aspen Dynamics. On the other behaviour Aspen Dynamics. This powerful simulator can automatically initialize the dynamic simulation using the steady state results of the Aspen Plus simulation Interestingly.
The reactor geometry data are reported below. The reactor. For this intention. Vessel type: Let s select the option with Template and then click OK see Figure 5. Creating flowsheet The process low diagram.
Simulation approach a To open the Aspen Plus Startup dialog box. Local PC User name: MCTtcB W. The window looks like Figure 5. PVil i.
As shown in Figure