Unformatted text preview: Homework 1 Problem 4 Aspen HYSYS™ CSTR Esterification 20 points possible due Friday September 2, 2011 Grader: Israel Problem Statement: Liquid acetic acid and ethanol are fed into a continuously stirred tank reactor at 150°C and 700 kPa, and 100°C and 700 kPa, respectivly. The following balanced reversible reaction is carried out in the CSTR. acid catalyst
C 2 H 4 O2 C 2 H 6 O C 4 H 8 O2 H 2 O Both forward and reverse reactions are elementary. Each component has a molar flow of 450 lbmole/hr. The estimated kinetics data is listed in the table below. Experimental Value Pre‐exponential factor Forward Reaction 499 Reverse Reaction 85 Activation Energy (Btu/lbmol) 2600 2600 The adiabatic CSTR runs at constant pressure and 75% liquid capacity. It has a volume of 1 m3. Determine the forward reaction conversion. Method of Solution: Use the Continuously Stirred Tank Reactor unit in HYSYS to simulate the process and calculate the conversion. Solution: 1) Open the HYSYSTM program by selecting All Programs → AspenTech → Process Modeling V7.2 → Aspen HYSYS → Aspen HYSYS. 2) Once the program opens, select File → New → Case from the toolbar or click the button to start a new case. 3) Click on the Fluid Pkgs tab and then click the Add... button in the Current Fluid Packages box. Page 1 of 11 4) The Fluid Package: Basis window will open; select the UNIQUAC fluid property package. Uniquac is a very detailed activity model that is most suitable for mixtures containing water, alcohols, amines, nitriles, esters, ketones, aldehydes, and hydrocarbons operating at low pressures. 5) Use the drop down menu to change the vapor phase model from Ideal to Virial. Acetic acid forms vapor phase dimers, which will be accounted for using this vapor model. Page 2 of 11 6) Click View to open the Component List View window, and then input the process components. 7) After all process components have been added to the list, close the Component List View and Fluid Package windows. Page 3 of 11 8) Click on the Reactions tab of the Simulation Basis Manager window. Click Add Rxn... 9) Select Kinetic from the Reactions pop‐up window and click Add Reaction. A Kinetic Reaction window will open. 10) Add each component by selecting it from the drop down menu in the corresponding field. Enter a negative stoichiometric coefficient for reactants and a positive stoichiometric coefficient for products. The reaction orders should be 1 or zero depending on the direction of the reaction. Page 4 of 11 11) Click on the Basis tab. Check that the basis is molar concentration, the basis units are lbmole/ft3, the rate units are lbmole/ft3‐hr, and that the reaction phase is set to liquid.+ 12) Click on the Parameters tab. Enter the given estimated kinetic data (be sure that the units are correct). The status bar should turn green and state ‘ready’ when done so. 13) Close the Kinetic Reaction and Reactions windows. Page 5 of 11 14) Under Reaction Sets on the Reactions tab of the Simulation Basis Manager window, click Add to FP. This must be done for the reaction to be available to the PFD. Click Add Set to Fluid Package in the Add ‘Global Rxn Set’ pop‐up window. 15) Click Enter Simulation Environment. 16) Click on the Continuously Stirred Tank Reactor icon in the Object Palette, and click again in the PDF window to place the CSTR in the workspace. 17) Double‐click on the CSTR to specify the design parameters that are known from the problem statement. Type “Acetic Acid” and “Ethanol” as Inlets, “Vapor Product” as the Vapour Outlet, “Liquid Product” as the Liquid Outlet and leave the Energy field blank. Page 6 of 11 18) Click on the Reactions tab. Select Global Rxn Set from the Reaction Set drop‐down menu. 19) Click on the Rating tab. Enter a Volume of 1 m3. HYSYSTM will automatically define the reactor dimensions based on the given information. Page 7 of 11 20) Click on the Design tab and then click Parameters on the left‐hand side of the window. Enter a Delta P of 0 and a Liquid Level of 75 %. Notice that the Volume can also be specified here. 21) Select the Worksheet tab. Enter the molar flow rates of the Acetic Acid and Ethanol streams, as given in the problem statement. Also, specify the stream temperatures and pressures. Page 8 of 11 22) Click Compositions on the left‐hand side of the window, and input the composition of the two feed streams. 23) The CSTR should converge. The status bar at the bottom of the CSTR window should turn green, and display “OK”. The completed process flow diagram should look similar to the one below. 24) Now that the PFD has converged, the conversion can be found. Open the CSTR input window by double‐clicking on the icon in the PFD. Click on Page 9 of 11 the Reactions tab. Next, click on Results on the left‐hand side of the tab view. Both, the conversion and extent of reaction are solved for and displayed on this page. 25) Right‐click anywhere in the workspace, and select Add Workbook Table from the menu options. Highlight the “Material Streams” option and click Select. A table displaying the process stream conditions appears in the workspace. You
can move the tables to an orientation where everything is clearly displayed in the
PFD. Workbook tables are very useful for displaying results in HYSYSTM. 26) Also add a Composition workbook to the PFD.
27) Add a text box to the PFD by selecting the
icon located on the PFD toolbar
and click in an open space of the PFD. A text box will appear type in your name
Homework #1 Problem #3. Click OK. The text box can be resized by clicking the
size mode button,
, on the PFD toolbar. Then stretch the text box by moving
the sizing squares that appear on the text box. 28) The final PFD should look similar to the figure below: Page 10 of 11 Page 11 of 11 ...
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