Regression Exercise, Day 1 Name __Juan Sebastian Snchez Velandia__Mentor: Professor LiraIn this exercise you will evaluate parameters relative to experimental data and learn how to regress experimental data.Note that Aspen can get sluggish if you have a lot of tabs open. Close some tabs if you notice this behavior. You can close all the extra tabs by right clicking on a tab.1. Open Aspen Plus Desktop User Interface. Start a new case from the Chemicals with Metric Units template. This will default to the NRTL model. 2. In the Components>Specifications window, select the Enterprise Database tab. 3. Select the NISTV86 NIST-TRC database and the APV86 EOS-LIT database and move them to the right.

4. Enter chloroform, benzene, methanol, and cyclohexane as components. You may edit the ID to make them easier to identify.5. Browse to Properties>Parameters>Binary Interaction. Observe the NRTL parameters. Which binary system does NOT have parameters? _Cloroformo-Ciclohexano_6. Note that the parameter folder turns blue as soon as you observe the parameters; Aspen assumes you approve the parameters or absence of parameters as soon as you view the page.a. Use the dropdown arrows in the parameter windows line for Source (click the parameter source cell to activate the dropdown), and observe that multiple parameter sets are available for NRTL.b. Are parameters available fitted for the Hayden-OConnell (HOC) vapor phase predictions for the five binaries with parameters? _____Si______c. In the NRTL folder, leave the parameters selected for Aspen VLE IG. 7. Select Binary analysis from the ribbon . Set the Analysis Type to Pxy. Set the system to chloroform + cyclohexane. Select chloroform for the x-axis. Set the temperature to 39.99oC (the reason for this unusual temperature will become apparent later) and click Run Analysisto generate a Pxy diagram. What is the shape of the bubble line?Es una lnea rectaReview the lecture handout to understand what this shape means. What is your conclusion about the NRTL predictions for a system without parameter values?

What is your conclusion about checking parameter value before performing distillation calculations?The system can be distillated without any problems at the given temperature because the is not an azeotrope in the equilibrium diagram, the distillation can be achieved between 0,24 bar and 0,48 bar.8. Return to the NRTL parameter page. Check the box at the bottom to estimate parameters with UNIFAC. Click the NEXT button until the dialog box pops up and select Run Property Analysis/Setup.

9. Now Return to the NRTL parameter page. What do you see for the source of the parameters for chloroform + cyclohexane? (PCES is the parameter prediction).Record the values for the parameters:i: Chloroform j: Cyclohexane Bij: 247,309 Bji: -61,3363 Cij: 0,3

10. Now revisit the chloroform + cyclohexane Pxy if you still have it in the tabs. Generate it again if you closed it earlier. What do you notice about the bubble line? Are the predictions for this system positive deviations from Raoults law, or negative?

PositivosEvaulation of parameters with data11. Click the NIST TDE button in the menu ribbon . Select to retrieve binary data. Set the components to chloroform + cyclohexane.

12. Click in the LEFT pane (Note: Clicking in the RIGHT panel can cause Aspen to crash!) to view Binary VLE 006 and Binary VLE 004. Let us save both those sets. Click Save Data at the bottom of the screen, select both sets. Note that Aspen has place you in the Data folder of the property browser. For BVLE004 click the Data tab.

Vle 006

Vle 004

13. Note these data are only P-x. Use the plot tools to create a P-x diagram.

14. If it is still open, delete the tab for BINRY-1 (Binary) P-xy-Plot. We need to recreate it with K temperature units. Browse to Analysis>BINRY-1>Results. Be sure the chloroform is the first listed component because that must be the x-axis. If not, regenerate the table. Use the dropdown menus to change the temperature to K, and the pressure to Pa. We will create a plot to merge with the experimental data, but the units MUST agree to get a good plot. The units from calculated results must always be converted to match the experimental units. Click the P-xy plot button. Double-check that the pressure is in Pa.

15. Now, let us merge the plots. Find the plot BLE004 (MIXTURE)-P-xy-Plot. Click (Design Tab)Merge Plot. If you have done these steps properly you will finish with ONE plot with two y axes. If you made an error, there is no undo, you will have to start over with the plot. Aspen keeps the original plot, so the number of tabs can get large. 16. Right click on the merged plot and select Y Axis Map, and click Single Y-Axis, and OK.

17. The model was created by fitting NRTL to UNIFAC predictions. What is your conclusion about the predictions for this system? Unifac se ajusta bien a los datos experimentalesRegressing Data

18. From the Home tab, click Regression. Create a new regression case named as you choose.

19. Configure a regression for NRTL using BVLE004 as shown in the figure on the lower left. 20. Note the binary parameters for this system in step 9. We will leave Cij the same and regress only Bij and Bji. Aspen will read the active parameters from the parameter window and parameters that are not regressed will maintain the values from the table.21. Return to the Regression input, and configure the initial guess for the NRTL parameter 2 for each species as shown on the below left. (The Initial Value may be prepopulated depending on the order of clicks above.) On the Algorithm tab, note that the Maximum Likelihood method is selected. Because the data are only P-x, we will change the method. Use Barkers Method. 22. Then click the Next button and run the regression (as in the figure in the above right.) You will be prompted to overwrite parameters, say Yes to all. 23. Observe the fitted parameters now appear in the Binary Parameter folder with the name of your regression (mine was named DR-1.) Note that the original parameters are still available in the dropdown parameter selector.Record the values for the parameters:i: Cloroformo j: Ciclohexano Bij: 289,128 Bji: -193,807 Cij: 0,3Depending on time, you can perform another analysis and plot the results, but these will create a curve very close to the parameters obtained from the UNIFAC prediction. (UNIFAC is not always so close).

24. Not all data are useful. Using the data for BVLE006, superimpose them on a plot evaluated from T-xy calculations at 95 kPa. Which component was probably not pure when the data were collected?

El cloroformo porque no se ajusta bien a la grfica entonces presenta impurezas

Challenging systems25. Close all the windows except the Control Panel by right-clicking the tab for Control Panel.26. Systems with VLLE are challenging to model, and you should be aware that Aspen may not predict these very well, even when fitted. Use the NIST database to obtain for the methanol + cyclohexane system BVLE003, 005, 010, 018, 023 AND BLLE052, 055. 27. Create a merged T-xy plot with all the VLE data and T-xx LLE data for the system. Do this carefully because you will want to keep the plot. Keep track of the name of the plot you are merging on to. Delete the extra plots after each merge to keep organized. After you have merged them, map to a single Y-axis. You should see an LLE dome and an minimum boiling azeotrope separated by several degrees.28. Using the parameters APV86 VLE-IG, generate a T-xy at 1.013 bar, and be sure to specify methanol as the x-axis. As before, to merge, delete the figure, then change the temperature units to K and replot. Then merge FROM the composite data plot onto the calculate curve. Do NOT delete the composite data plot. While the plot looks pretty good, the results are misleading. There is an incorrect LLE region on the predicted on the cyclohexane side of the diagram. To see this, let us generate the LLE from these parameters.29. Aspen does not provide a utility to generate LLE as a function of temperature. To do this, move to the Simulation section of Aspen Plus, create a flowsheet with Separator (Flash3). Create a feed that is 30 mol% methanol + 70 mol% cyclohexane at 2 bar and 275K. Add a vapor exit exit streams. Set the separator pressure to 2 bar and the temperature to 275K. On the Flash Options tab, set the Maximum iterations = 100 because LLE converges very slowly.30. Create a sensitivity analysis by browsing to Model Analysis Tools>Sensitivity. Specify to vary the separator temperature by 5K from 275 K to 330 K as shown on the lower left. 31. Measure the x for methanol in the two liquid phases (I called mine XALPHA and XBETA) as shown in the upper right. Be sure to specify the liquid phases, which may be different stream values that I have specified above.32. On the Tabulate sheet, click Fill Variables. Before you run, change the units to MET under Setup>Specifications. (This will make temperature in K). Then run the case.33. We want to create a plot in the Properties section. To do this, we will create a Data set to plot. (There may be a quicker way please tell me if you know of a better way.) View the sensitivity results, select the columns for Vary, XALPHA, XBETA and copy.

34. Open excel and paste the data. Now return to the Properties section of Aspen Plus. Create a new data set (I called mine ASPEN). Set the Data type to Txx. Paste the temperature and methanol compositions.35. Create a plot, merge with the composite T-xy. Print the resulting diagram. What do you notice about the LLE?

36. Aspen also provides LLE parameters. If those are used, the LLE will look good, but the VLE will not. Practitioners currently must make a choice as which property to represent.

Equilibrium Reactions in Reactive Distillation: Production of 1,1-dimethoxyethane (DME)July 13, 2015

DME is an important intermediate in the flavor and fragrance industry, and has been proposed as a fuel oxygenate to replace methyl t-butyl ether in gasoline. DME is formed by the reaction of methanol and acetaldehyde

2 CH3OH + CH3CHO = C4H10O2 + H2O Methanol Acetaldehyde DME (bp = 58oC) (bp = 21oC) (bp=64.3oC)

For the purpose of this exercise, the reaction may be assumed to take place rapidly in the presence of a solid acid catalyst such that it reaches equilibrium on every stage of the distillation column. The mole-fraction-based equilibrium constant for the reaction is given by the following expression:

Kx = xDME xH2O / xMeOH2 xAcH

ln(Kx) = -83.4 + 5190/T + 12.1 ln(T)

where xi is the mole fraction of the species in the liquid phase and T is in Kelvin.

Problem Statement: You are to configure a reactive distillation column to produce DME from the methanol and acetaldehyde streams defined below. The objectives of the exercise are 1) to achieve the highest possible conversion of acetaldehyde for the given feed streams; 2) produce a bottoms stream of >99 mol% water; 3) produce a distillate stream containing no water.

Preliminary design: It is always a good idea to sketch out the basic configuration of the reactive distillation column before beginning simulations. Using the information given, identify on the diagram below the relative feed stream locations, the general direction of flow of the species in the column, and the product stream compositions and flow rates that would be achieved in an ideal column. Consider where reactive trays might be relative to the feed streams. Reactive distillationcolumn

Simulation methods:

Column: RADFRAC in AspenPlusProperties method: Wilson equation with unknown parameters estimated by UNIFAC (defined by Aspen Properties Backup File to be imported into simulation see instructions below).

Feed streams:

Pure Acetaldehyde: P = 1.0 atm, T = 293 K, 100 kmol/hrPure Methanol:P = 1.0 atm, T = 335 K, 200 kmol/hr

Reactive distillation column specifications:

Partial kettle reboiler, total condenserOperating pressure: 1.0 atmNumber of stages in column: 25 (may be varied once column converges)Reflux ratio: 2.7 (may be varied once column converges)Bottoms flow rate: Determined by stoichiometry and conversion

Column parameters that may be varied in optimization:

Distillate and bottoms ratesFeed locations Number and position of reactive stagesReflux ratio (after initial simulation converged)Number of stages (after initial simulation converged) Instructions for Column Simulation:

1. Open a Blank AspenPlus V8.6 simulation and click on File, Import to import the Aspen Properties Backup File for the DME example. Choose to keep existing databases when prompted. This will load all components and the properties method. Define a process flowsheet with the RADFRAC column block, two inlet streams (both connect to the sole feed arrow on the RADFRAC block), and two product streams. 2. Enter the equilibrium reaction in the Reactions Folder as described in lecture. Remember to specify reaction as REAC-DIST as the reaction type. Do not enter values for Exponent these values represent the order of reaction with respect to each component and are not used for equilibrium reactions. 3. In RADFRAC Specifications-Setup/Configuration tab, it is recommended that you specify reflux ratio and bottoms flow rate as Operating Specifications. You must estimate an initial value of bottoms flow rate, and it will change as conversion of acetaldehyde and the purity of the bottoms stream change. Also, open the Specifications folder for your RADFRAC block, then find and open the Reactions tab to specify the reaction and the stages in the column that it will take place upon.4. Once all information has been input, run the simulation. Once it converges, save the simulation and then look at Stream Summary in the Data Browser and at Profiles under the RADFRAC block to check if stream purities are met and to understand how to improve your simulation.

Optimization Once you have a converged column simulation, you can vary the column parameters above to obtain the best possible acetaldehyde conversion (and thus yield of DME) and to obtain >99 mol% water in the bottoms with essentially no water exiting in the distillate stream from the column. You may also change reflux ratio, feed locations, number and location of reactive stages, and total number of stages as part of your optimization.

You can use the Sensitivity Analysis that was discussed earlier in the lecture. The Sensitivity Analysis can carry out multiple cases rapidly and observe the trend in column performance as one or more variables are changed. Results are found under Model Analysis Tools in the Sensitivity Analysis that you specified.Additional Optional ExercisePrepare a residue curve map (Home Distillation Synthesis) for the system DME-MeOH-Acetaldehyde that defines azeotropes and distillation boundaries of the ternary distillate stream. How does this map help define opportunities and limits to recovering nearly pure DME from the process? Propose a process concept (no simulation) that would allow you to obtain a pure DME product stream. Report For this exercise, submit a short report containing 1) a table with all parameters that define your distillation column, and 2) a stream table showing the feed and outlet streams and compositions.

Exercise, Day 2Name __________________________Adjusting Heat of Reaction to Match Experiment Mentor, Dr. LiraThe purpose of this lesson is to explore the importance of evaluating heat of reaction relative to heat of vaporization for a reactive distillation column. If the heat of reaction is wrong it will affect the energy balance on the stages, the vapor flow will be wrong, and also the separation.The reaction of interest isCyclohexene+Acetic AcidCyclohexyl Acetate CYCENE ACETICAC CYCESTER 1. Access http://webbook.nist.gov. For each compound, look up the Thermodynamic Data (check the boxes for Gas Phase and Condensed Phase). Record the heat of formation of each.Gas phase CYCENE __-4.32 0.98__ ACETICAC __-433. 3._ CYCESTER __-507.2 3.0_Liq phase CYCENE __-37.8 8.2__ ACETICAC -483.52 0.36 CYCESTER _-558.9 3.0_2. Calculate the heat of reaction expected from the NIST data, showing your calculations:

Results: Gas __-69.18___ Liquid __-37.58___Note the heats of reaction depend on the phase. The column will use a liquid phase reaction.3. Start a BLANK simulation (no template) in Aspen Plus. Import the provided .aprbkp Aspen Properties backup file. When prompted, keep the old databases.4. The NIST calculation is based on an ideal solution approximation. Browse to Properties>Methods and observe that the NRTL-HOC method is used. We will revisit this setting later.5. Create a stoichiometric reactor (RStoic) block with one feed stream and one product stream.6. Set the inlet flow to 25 C and 1 bar. Set the flow to 2 mol/sec using feed equimolar in acetic acid and cyclohexene. The units are important to convert the heat duty to the heat of reaction! 7. Set the reactor to be 25C and 1 bar.8. On the block reactions tab, set the reaction stoichiometry and the fractional conversion = 1 for one of the reactants.9. On the heat of reaction tab, click the radio button to Calculate the heat of reaction. Choose either reactant as the Reference Component, and set the T and P to match the reactor conditions and specify the liquid phase.10. Run. Access the results for the Reactor Block. Report the Heat Duty -31,02334170_kJ/s. From the Reactions tab, report the heat of reaction _-31023,3__kJ/kmol. Both should be in agreement. This value has been adjusted to match the heat of reaction calculated from the temperature dependence (vant Hoff eq) using MSU reaction equilibrium constant data.11. This step explores the heat of vaporization for acetic acid and cyclohexene and how they compare with the heat of reaction. Use Properties>Home>Analysis(Pure). Heat of vaporization is a Thermodynamic property DHVL, with units kJ/kmol. Generate 16 points from 25C to 100C. Report the values at the endpoints:Acetic acid 25C _23420,4_kJ/kmol 100C _23814,9__ kJ/kmol(Acetic acid is unusual because of dimerization, and the heat of vaporization increases slightly in this temperature range).Repeat the analysis for cyclohexene.Cyclohexene 25C _33406,6__kJ/kmol 100C __29444,4__ kJ/kmol12. Is the heat of reaction significant compared to the heat of vaporization? (Compare the heat of reaction with the heat of vaporization for one mole.)El calor de reaccin si es significativo en comparacin a una mol porque su valor es bastante grande13. What is the % error that would result for the heat of reaction if the NIST value was used compared to the experimental value?

El error sera del 17,44%

14. Suppose three moles of cyclohexene were mixed with one mole of acetic acid under isothermal conditions at 25C. Assuming complete reaction at 25C, how much of the excess cyclohexene would be evaporated using the values from step 10?

How much of the excess cyclohexene would be boiled using the heat of reaction from NIST?

15. The heat of formation for cyclohexyl acetate has been adjusted to make the heat of reaction match the temperature dependence of our experimental reaction equilibrium constant. Use the data browser to find the special setting using Properties>Methods>Parameters>Pure Component>USRHF. Record the value of the parameter DHFORM. _-4,99e+08_ J/kmol. 16. Explore the effect on the heat of reaction if the default heat of reaction from Aspen is used. To do this, right-click USRHF parameter group in the data browser, and select Delete.17. Run the Aspen file. What heat of reaction results? _-35023,3_kJ/mol. Comment on the significance of this difference in relation to the heat of vaporization of feed.La significancia de la diferencia entre los valores de calor de reaccin obtenidos antes y despus no es importante en la relacin al calor de vaporizacin de la alimentacin18. Now, recreate the special override property group: In the data browser select Properties>Methods>Parameters>Pure Component. Click New. Set the property to Scalar and before you press OK, set the name to USRHF. Restore the DHFORM value recorded in step 15. Run the case to assure that the heat of reaction was restored as in step 10. The method used here could be used to override any of Aspens default parameters.19. View all the scalar properties used in the simulation using Properties>Home>Retrieve Parameter Results. This includes any parameters that are overridden with user parameters. These tables are very important to help you trace the actual parameters used in the simulation for all the possible folders in the properties browser. Record the HFORM for cyclohexyl acetate _-499000_kJ/kmol from the pure component Results.20. Now explore the effect of the HOC on the behavior: Under Block Options for the reactor, set the Property Method to Ideal. Run the case again. Report the Heat Duty _-55,2501_kJ/s. From the Reactions tab, report the heat of reaction _55250,1873__kJ/kmol.

Explain, using molecular descriptions of acetic acid behavior, why the error is now so large. Remember the HOC is representing vapor phase deviations from ideality. It may be helpful to review the lecture handouts from Day 1.

El aumento del error se debe porque en el modelo no se toma en cuenta la dimerizacin del cido actico a diferencia del modelo de HOC

Explain the reason for the direction of the change of error (why is it more endothermic or more exothermic).

La reaccin es ms exotrmica en el modelo ideal porque el calor que no se tiene en cuenta de la dimerizacin del cido actico se va para la reaccin hacindola ms exotrmica.

21. If you would like to save your case, be sure to turn back on HOC for the block. Do not overwrite the original property backup file, because it will be used for the Professor Millers exercise.

Simulation of Cyclohexyl Acetate Formation in a Pilot Scale RD ColumnJuly 14, 2015

The formation of cyclohexyl acetate from acetic acid and cyclohexene is a reaction system with features compatible with reactive distillation.

Cyclohexene + Acetic Acid = Cyclohexyl Acetate (b.p. 82oC)(b.p. 118oC) (b.p. 172oC) (MW = 82)(MW = 60) (MW = 142)

The reaction is reversible and takes place over strong acid ion exchange resin. However, unlike esterification involving free acids and alcohols, this liquid phase reaction is moderately exothermic. (Hr = -30 kJ/mol).

In addition to simulating commercial-scale industrial processes, AspenPlus can help describe and validate results obtained from small pilot-scale operations. In this exercise, you will simulate the formation of cyclohexyl acetate from cyclohexene and acetic acid in the pilot-scale reactive distillation facility at Michigan State University. To start the simulation, you have been given an Aspen Properties Backup file with components entered and properties methods detailed.

The goal of the simulation is to use kinetic reaction data in RADFRAC to simulate reactive distillation with kinetically controlled reactions. Once you have a working simulation, additional goals are 2) to learn about accounting for energy losses in distillation systems and 3) to learn how energy (heat) integration can affect the performance of a reactive distillation system.

Activity-based (mol-gamma) kinetics to describe liquid phase reactions: For reversible reactions that are kinetically controlled (as opposed to being at equilibrium), AspenPlus requires that kinetics of forward and reverse reactions be entered separately into simulations. Kinetics for the forward and reverse reactions for cyclohexyl acetate formation in the liquid phase are given below. Note that the values of k1 and k2 are given in units from a laboratory batch reactor, and that rate depends on activity (ai = xii). You must convert the rate constants to the proper units for the AspenPlus RADFRAC simulation using the physical properties information provided in this handout. Remember, you must develop the reaction set for RADFRAC using REAC-DIST as the type of reaction for reactive distillation. In the Stoichiometry tab, the exponents are the order of reaction with respect to each component.

1. Cyclohexene + Acetic Acid = Cyclohexyl acetate (r1 = k1aCYCaAA)

k1 = 5.55 x 1010 exp (-88100/RT) (kmol kgsol / kgcat / m3 / sec); R in (J/mol/K)

2. Cyclohexyl acetate = Cyclohexene + Acetic Acid (r2 = k2aCYAc)

k2 = 4.06 x 1014 exp (-118410/RT) (kmol kgsol / kgcat / m3 / sec); R in (J/mol/K)

EXERCISES:

1. Modeling experimental pilot-scale column behavior: Open a Blank simulation in AspenPlus 8.6 and then import the Aspen Properties Backup File given in the course folder for todays exercises. Choose to keep existing databases when prompted. Run the Properties Analysis Setup and then switch to the Simulation mode. Define a RADFRAC block and all of the information below describing the pilot-scale reactive distillation column. Run the simulation and compare the distillate and bottoms stream compositions to those obtained experimentally.

Experimental feed streams:Cyclohexene: 28.3 g/min, 31oC, 1 atm on Stage 12Acetic acid: 25.58 g/min, 31oC, 1 atm on Stage 4

Experimental Product Streams:DistillateBottomsIdealized values (adjusted for mass balance closure of 100%) are given in parentheses

Cyclohexene (mol/min)0.082 (0.0957)0.078 (0.0884)Acetic Acid (mol/min)0.032 (0.0265)0.273 (0.239)Cyclohexyl acetate (mol/min)00.161 (0.161)

Column parameters:Number of stages:14 equilibrium stagesCondenser:Total; 30oC of subcooling (=30 DELTAC)Reboiler:KettleValid phases: Vapor-liquidLiquid phase density:870 kg/m3Convergence: Custom (see below)Distillate Rate: 8.7 g/minReboiler duty: 430 WPressure: 1 atmReactive Stages: 4 to 11Holdup: Mass 0.075 kg catalyst (as liquid) /stage Packing (Pack Rating): Kerapak Standard, Stages 2 13 Column diameter:0.052 m HETP:0.5 m

Column convergence scheme: Basic: Nonideal algorithm, 200 iterationsInitialization method: Azeotropic; Damping: Severe; Liquid-liquid split: Hybrid

Los valores de destilado obtenidos concuerdan con los que se obtuvieron experimentalmente, sin embargo los fondos pueden variar con los obtenidos experimentalmente.

2. Column Heat Loss: An energy balance conducted on the pilot-scale distillation column during operation showed a heat loss from the column of approximately 140 W at steady state. The experimental temperature profile in the column at these conditions is shown below. To model the heat loss from the column, go to the Heat Loss page in the Heater/Cooler folder of your RADFRAC column block to insert a heat loss term into the simulation. Simulate the heat loss cases below to determine which gives a simulated temperature profile closest to the experimental profile shown. It is best to make the comparison by transferring the profiles obtained to Excel and graphing them, along with the experimental profile given below.

a) heat loss of 140W total across all stages in column

b) heat loss of 140 W entirely at Stage 13 of column

c) another distribution of your choice of 140 W heat loss in the column

The answer may be surprising, but it is reasonable given how the insulation is actually arranged on the pilot-scale column. It also provides insight into how the column might be better insulated for future operation.

3. Heat integration: The experimental column temperature profile shown above is different from that in conventional distillation in that temperature decreases as one goes down the column. This arises from feeding acetic acid near the top of the column and cyclohexene near the bottom. It also lends itself to consideration of heat integration. Since distillation columns are essentially heat exchangers that add heat at a high temperature at the bottom and remove it at a lower temperature at the top of the column, being able to effectively move heat from the top of the column toward the bottom should reduce overall energy consumption or aid in column performance.

In this exercise, explore internal heat integration in the pilot-scale distillation with heat loss for the simulation that most closely approximates the experimental temperature profile above (140W heat loss on Stage 13). Add terms in the Heat Loss tab in the Heater/Cooler folder in your column block to remove heat from one stage near the top of the column (Stages 4 6) and add it back to one stage of the lower section (Stages 10-13). (Give a negative value of heat loss to simulate heat addition). Start with 20 W of heat integration and increase from there. Determine the improvement in column performance (conversion of cyclohexene), if any, as a function of the amount of heat transferred by heat integration. Examine the temperature profile in the column as you increase the extent of heat exchange between column sections how does the temperature profile change? What is the limit on the amount of heat that can be exchanged; in other words what must be true of the stage temperatures for which heat integration is taking place?

ReportPrepare a report that includes 1) a stream table showing results of initial converged simulation and comparison with experimental outlet flow rates; 2) a graph showing the column temperature profiles for the heat loss cases and the experimental profile; 3) a table describing the outlet column flow rates for the heat integration cases you examined. In each case comment on the effect of heat loss or heat integration on the separation achieved in the column. Reactive Distillation Exercise Understand Saddle Pinch Name__________________________The goal of this exercise is to understand pinch points, understand how to integrate Excel with Aspen properties, and also to learn distillation line methods. Part I Understanding Saddle Pinch1. Start new case, use template Chemicals with Metric Units.2. Set T units to C by selecting the correct preconfigured unit option. Add components Butane, Pentane, Hexane. Set property model to ideal3. Simulation>Setup>Report Options>Stream to include mole fractions in stream reports. Place a Column>ConSep conceptual design column block on the flowsheet. Add streams Feed, Distil, Bott to the column. 4. Set Feed to 10C and 1 bar, 1 kgmol/min, with composition (mole fr), xbutane = 0.3, xpentane =0.4, xhexane =0.3, respectively.5. Open the ConSep block from the flowsheet. Setup components in this order clockwise from top: 1 Butane; 2 Hexane; 3 Pentane. The order of components is important for the instructions that follow.6. For Specification, set the Block conditions to: Distillate recoveries 0.99999 butane, 0.95 pentane, Bottoms to 0.9999 recovery hexane. (Note these are NOT mole fractions.) Set r = 1, P = 1 bar. Set the calculation options to Distillation curve. Click Interactive Design button.7. Is the separation feasible at these conditions? _yes_

8. What color is the stripping section line? _Purple_ What color is the rectifying section line?_Blue__9. How many stages are required? ________16___________10. Each point on the lines represents a stage. Is the separation more difficult in the rectifying or stripping section? _Rectifying_11. Click the +( button and then click the diagram to add a two residue curves in the stripping region.12. When a separation requires many stages without much separation, the separation is said to be pinched. The pinch in this case is called a saddle pinch because it is near the saddle point of the residue curves.13. Change reflux to 100. Click calculate. Click +( and add a residue curve through the stripping section line near the saddle point. Note how the distillation line and residue lines approach each other at high reflux.

14. Remove the saddle pinch by changing the spec to: Distillate recoveries 0.999 butane, 0.95 pentane, Bottoms to 0.99 recovery hexane. Set r = 0.9. Calculate. Is the separation feasible? __No___

15. Explore to find the minimum reflux for feasible separation (to two digits) ___0,89____

16. A pinch just above the feed, or just below the feed is called a feed pinch. Is the system near a feed pinch? _Yes_ Above or below the feed? _Below__How many stage required? ___16__ Feed stage ______14_____Part II Column Design and Relation of x-y to Residue Curve17. This is a non-reactive system of chloroform(1) + acetone(2) + benzene(3). Pure boiling points are (in oC), (61.2, 56.3,80.1), respectively. Add the components in Aspen. Set the method to NRTL-HOC. Approve the parameters.18. Set the feed to x1 = .11, x2 = .17, x3 = 0.72. Set the components in conceptual design (clockwise from top, Acetone, Chloroform, Benzene). For the distillate, set x2 = 0.986, for the bottoms, set x1 = 0.132, x3 = 0.86635. Set r = 4.896.19. Run the calculation. You will find a distillation boundary has been identified in the figure. Note: Double check that the feed is correct. Note that the reset button toggles the display between wt fractions and mole fractions. Be sure you are using mole fractions for the remainder of the exercise.20. Add residue curves by clicking on +(I, and add a curve through mole fractions {0.58, 0.28, 0.14}, and another through mole fractions {0.66, 0.3 0.04}.21. From the residue curves, you should be able to see that (1)+(2) forms and azeotropes. Identify the following points in each region as origin, saddle, terminus.Upper left region:Pure (2) ____Origin______Pure (3) ___Terminus____(1) + (2) azeotrope ___Saddle___Lower right region:Pure(1) ___Origin____Pure (3) __Terminus____(1) + (2) azeotrope ___Saddle____

22. Will it be easy or difficult to obtain pure (3) from the upper left region? Why?It will be easy because there is a stable node so you can obtain de pure benzene23. Draw the bow tie region of accessible compositions if a feed is xF = (0.2, 0.4, 0.4). Would the specifications from Part II, item 2 be consistent with this bow tie?

24. Now let us look more closely at the results for the feed x1 = .11, x2 = .17, x3 = 0.72. Record the size of the column and purity at the top below. Some values can be found from the Results folder, Design tab.:Distillate (x1, x2, x3): x1 0,0034 x20,986 x3 0,0105__

Bottoms: _ x1 0,132 x20,00144 x3 0,86656__

Stripping stages: _18,4597_ Rectifying Stages: _32,9708_ Feed Stage: _33,9708_

Distill Flow_____; Bottoms Flow: _________Boilup:_1,45697 Reflux:_4.896_

25. Now let us understand the relation between the residue curves and the stage compositions. Close the conceptual design. Look in the data browser and find the Profile Plots for the conceptual design. The feed stage is where the slope of the temperature profile changes. Count five stages above the feed (rectifying section, think about whether the temperature should be higher or lower than the feed stage), and record the stage number: ___18____

26. From the Liquid Composition tab, hover over profile and record the compositions. (In principle, you should be able to see the composition from the Results folder, but mine does not show the stage of interest). x (all three) x1 0,525 x20,384 x3 0,0907 y (all three) x1 0,612 x20,317 x3 0,0717 27. Regenerate the conceptual design. Add grid lines. Now, using the liquid composition above, use +(I to generate a residue curve through that stage. Add grid lines. 28. Use the +( tool to add some residue curves in the lower right section of the diagram.29. Now add a marker with the vapor composition. Print the figure, or copy (use the clipboard icon)/paste in to Word.

30. How does the tangent of the residue curve compare with the relation between x and y? What is the slope of the tangent line on Cartesian coordinates (approximate)? ________________31. How does the column number of stripping stages, Ns, and number of rectifying stages, Nr change if r is increased by 10% at the same outlet conditions?

32. Now, return to the flowsheet. Right-click on the ConSep block and Convert To a RadFrac block. Select the Input folder and note how the conceptual design has been converted to RadFrac specifications. The ConSep is only an estimate for the actual design because the ConSep does not include energy balances.

Distillation with Heterogeneous Azeotrope: Esterification of Organic Acids with ButanolJuly 15, 2014

This week we have looked at methods for simulating reactive distillation systems and for modeling the non-ideal phase equilibria of many organic molecules. Today we will illustrate how we can take advantage of non-ideal thermodynamic behavior to design an efficient process for making esters of organic acids. The process concept we will examine has application to heavier alcohols (C4+) that form azeotropes with water and are only partially miscible with water. As an example, the reaction for esterification of butyric acid with n-butanol is C4H9OH + (C3H7)-COOH = (C3H7)-COOC4H9 + H2O Speciesn-ButanolButyric acidButyl butyrateWater

b.p. (oC)118163.5165100

Density(kg/m3)8109608701000

Mol. Wt.748814418

Hv (kJ/kg)5953884562257

The T-x-y diagram for water and 1-butanol at 1.0 atm total pressure is given below. n-Butanol and water form a heterogeneous azeotrope at 366 K (93oC) and a composition of 75 mol% water, 25 mol% n-butanol. When condensed, the azeotropic vapor forms two liquid phases, one with 43 mol% water in butanol (butanol-rich) and the other with 2.0 mol% butanol in water (water-rich). These compositions are seen at the ends of the horizontal line at 366 K, indicative of three phases in equilibrium (vapor + two liquids) at this temperature for this binary system.The key concept in taking advantage of this heterogeneous azeotrope for esterification reactions is that water formed in esterification can be easily separated from the alcohol by simple decanting. The alcohol-rich phase can be recycled back to the reaction vessel to drive the reaction to completion. In a reactive distillation column, this means producing the butanol-water azeotrope at the top of the distillation column, condensing the vapor and separating the two condensed phases in a decanter, recycling the butanol-rich phase, and taking the water-rich phase as the distillate product. This same concept can be done at the laboratory scale in simple distillation, where the condensed phase is split and water is recovered in what is known as a Dean-Stark trap.

Problem Statement: You are to simulate a reactive distillation column to make the n-butyl ester of n-butyric acid. A set of initial column specifications is provided below; the goal of the simulation is to achieve 98% conversion of butyric acid to butyl butyrate using as little butanol as possible. Initial calculations: Before starting the simulation, it is important to carry out a hand calculation to obtain desired values of flow rates of distillate and bottoms streams. For this hand calculation, assume the butyric acid feed flow rate is 100 kmol/hr, the n-butanol feed flow rate is 120 kmol/hr, and that conversion of butyric acid is 98%. Assume that all water produced in esterification is removed at the top of the column, and that butyric acid and butyl butyrate exit only from the bottom of the column. Butanol can be removed from both the top and bottom of the column. The vapor from the top of the column enters a decanter (see diagram); the butanol-rich (light) phase from the decanter is recycled, and the water-rich (heavy) phase is withdrawn as distillate. Given these specifications and the T-x-y diagram describing phase behavior, the composition and flow rate of the distillate stream is thus fixed, and the inverse lever rule can be used to determine the flow rates of the butanol-rich reflux stream and the vapor stream out the top of the column. Once the distillate stream and feed streams are fixed, the bottoms stream flow rate and composition is also defined. DecanterCondenserDistillateReactive distillation columnBottomsFeed 2Feed 1

Complete your calculations to find flow rate and composition for distillate and bottoms streams from the column, and for the stream leaving the decanter that returns to the column as shown in the diagram.Aspen Simulation: Open Aspen 8.6 to a blank simulation. Import the properties backup file for this exercise into the blank simulation. Keep existing databases. Make sure that UNIQUAC is specified as the Base property method, and that Estimate Missing Parameters by UNIFAC is checked under the Properties-Parameters-Binary Interaction-UNIQ-1 sheet. Under Setup Specification, choose MET for input units.Complete the process flowsheet by inserting a RADFRAC column block, add two feed streams to the column, and connect distillate and bottoms exiting streams.Specify the two feed streams as follows:Stream 1: 100 kmol/hr n-butyric acid, T=363 K, P = 1.0 atmStream 2: 120 kmol/hr n-butanol, T=363 K, P = 1.0 atmSpecify a reaction set for butyric acid esterification under Reactions in the Data menu:(Name the set, type is REAC-DIST, Equilibrium, Ke=3.0)Specify the following for your RADFRAC column block as a starting point:Type of calculation: EquilibriumNumber of stages: 14Condenser:TotalReboiler:KettleValid phases: Vapor-Liquid-LiquidConvergence:StandardOperating specification*: Reboiler duty = 2000 kJ/secFeed stream locations:Butyric acid stream on Stage 5Butanol stream on Stage 10Pressure at top stage:1.0 atm3-Phase:Check at all stagesKey components for 2nd phase:Water and butanol

Under the Reactions folder in RADFRAC: Specify Reactive stages = 6 (start) to 9 (end)

Under the Decanters folder in RADRAC:Click New, and then enter 1 for Decanter Stage Number(NOTE: The less dense liquid stream is denoted as the 1st liquid stream exiting the decanter.)Fraction of 1st liquid returned:1.0Fraction of 2nd liquid returned:0Degrees Subcooled:5 DELTACUnder the Options tab: Specify all of Stream 1 is returned to Stage 2

*The presence of a heterogeneous azeotrope that splits into two liquid phases reduces the number of degrees of freedom in designing a distillation column. With specified feed streams, defining a desired fractional conversion defines all stream flows out of the distillation column. This reduces the number of specifications we have to make for the column.

Running the simulation and optimizing the column: When running the simulation, choose No to All when given the opportunity to replace parameters with those from PECS.If you properly enter all information given, the column should converge to give partial conversion of butyric acid to butyl butyrate. Save this converged version as a base case. To optimize column operation, use your understanding of separation principles to change column parameters (feed locations, number of stages, number of reactive stages, reboiler duty, butanol feed rate) to achieve the desired 98% butyric acid conversion with as little butanol fed as possible. It is wise to change parameters incrementally, not by large steps. Column diameter: After you have finished defining and optimizing your column, determine the column diameter and height required as shown below.Under the Pack Sizing folder in RADFRAC:Choose New, and then either name or accept 1 as the first column sectionIn Specifications, it is possible to define different sections of the column defined by feed locations. For this example, use one section for the entire column, so define the Starting stage = 2 and the ending stage = N-1, where N is the number of stages in your column. (NOTE: The condenser is Stage 1 and the reboiler is Stage N in Aspen column simulations.) Use KERAPAK as the packing type, with HETP = 0.5 m. Following the simulation, the column diameter is given under Results in Pack Sizing.Prepare a report of your final column configuration (height, diameter, number of stages, reflux ratio, etc) and a stream table of the feeds and products from your simulation.

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