Homework 4 Problem 2 Aspen HYSYS Multiple Reaction Conversion

Homework 4 Problem 2 Aspen HYSYS Multiple Reaction Conversion

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Unformatted text preview: Homework 4 Problem 2 Aspen HYSYS™ Multiple Reaction Conversion 20 points possible due Tuesday September 27, 2011 Grader: Alan Problem Statement: Methane is oxidized with air to produce formaldehyde in a continuous reactor, according to the following reaction: CH4 + O2 CH2O + H2O [Eq. 1] A competing reaction is the combustion of methane to form CO2, as shown in the balanced reaction below: CH4 + 2O2 CO2 + 2H2O [Eq. 2] Conversion of methane to formaldehyde is 30% and conversion to CO2 is 10%. The reactor is fed two streams: pure methane and air. The two feeds are fed such that there are equal molar amounts of methane and oxygen entering the reactor. If the methane enters the reactor at 25 oC and the air enters at 100 oC, how much heat (kJ/hr) must be withdrawn for the product stream to leave at 150 oC? Method of Solution: The system will be solved using the Conversion Reactor unit in HYSYSTM. Solution: 1) Open the HYSYSTM program and start a new case. 2) Click on the Fluid Pkgs tab of the Simulation Basis Manager. Click Add. Select the UNIQUAC model. This problem is based on Felder and Rousseau’s Elementary Principles of Chemical Processes 3rd Edition Example 9.5‐2 3) Click View to open the Component List View window. Add the six process components: CH4, CH2O, CO2, H2O, O2, and N2. 4) After all components have been added, close the Component List View and Fluid Package windows. 5) Open the Reactions tab of the Simulation Basis Manager. Then open the Reaction Set configuration. A default reaction set, “Global Rxn Set” appears in the Reaction Sets section. Click View Set. This problem is based on Felder and Rousseau’s Elementary Principles of Chemical Processes 3rd Edition Example 9.5‐2 6) Type “Methane Oxidation” in the Name field. Then, close the window. 7) Open the Reactions configuration and click the Add Rxn… button. 8) Since we know conversion information about the methane oxidation reaction, select “Conversion” and then click Add Reaction. This problem is based on Felder and Rousseau’s Elementary Principles of Chemical Processes 3rd Edition Example 9.5‐2 9) Enter the reactants and products of the methane oxidation reaction [Eq. 1] with the appropriate stoichiometric coefficients. Note: reactants are input with negative stoichiometric coefficients and products are input with positive stoichiometric coefficients. 10) Click on the Basis tab. Select “Methane” as the Basis. Since the reaction has a conversion of 30%, enter “30” into the Co field. The status bar should turn green and display “Ready”, indicating that the reaction is fully specified. This problem is based on Felder and Rousseau’s Elementary Principles of Chemical Processes 3rd Edition Example 9.5‐2 11) Add the competing side reaction [Eq. 2] by using steps 9‐12, outlined earlier. 12) We have successfully added the two reactions to a reaction set. Now, we need to associate the reaction set with the fluid package. Return to the Reaction Set and click Add to FP. This problem is based on Felder and Rousseau’s Elementary Principles of Chemical Processes 3rd Edition Example 9.5‐2 13) Select the appropriate fluid package. Click Add Set to Fluid Package. Be sure that the fluid package listing looks like this. NC (number of components) should display 6 and the PP (property package) should show the UNIQUAC-Ideal package that we originally selected. 14) Click Enter Simulation Environment. The PFD workspace will open. 15) Since the information in the problem statement is given to us in SI units, it might be a good idea to check to see that your user preferences are set to the same. [Tools/Preferences/Variables/ “SI”] 16) Click on the General Reactors icon on the Object Palette. A smaller palette box will appear with different types of reactors. Select the Conversion Reactor. Then, click in the PFD workspace to place the conversion reactor. 17) Double‐click on the conversion reactor in the PFD. Rename the reactor. Input “Methane” and “Air” as Inlets, “Products” as the Vapour Outlet, and “L” as the Liquid Outlet. Input “Q” for the Energy stream. This problem is based on Felder and Rousseau’s Elementary Principles of Chemical Processes 3rd Edition Example 9.5‐2 18) Click on the Reactions tab. Select “Methane Oxidation” for the Reaction Set to attach the two specified reactions to the reactor. Notice that the information entered in the Simulation Basis Manager appears. 19) Click on the Worksheet tab. Specify the following stream parameters: a) Methane: (1) Temperature = 25 oC (2) Pressure = 101 kPa (3) Molar Flow = 1 kgmole/hr (4) Composition = 100 mole % methane b) Air: (1) Temperature = 100 oC This problem is based on Felder and Rousseau’s Elementary Principles of Chemical Processes 3rd Edition Example 9.5‐2 (2) Pressure = 101 kPa (3) Let’s assume that air is 79 mole% nitrogen and 21 mole% oxygen. To input the composition, open the Air stream input window by double clicking the stream, click the Basis… button, change the composition basis to Mole Flow, and close the window. Enter O2 as 1 kgmole/hr and N2 as 3.76 kgmole/hr. Normalize so all other flows are zero. Click OK to save the changes and close the window. Close the stream window. c) Open the Products stream and enter the final temperature of 150°C. 20) The system should converge. Add Material Streams, Compositions, and an Energy workbook table to the PFD. Notice that the value for the Heat Flow of “Q” is the magnitude of heat removal required. The final Worksheet information should look similar to the figures below: This problem is based on Felder and Rousseau’s Elementary Principles of Chemical Processes 3rd Edition Example 9.5‐2 21) Notice that although a second outlet stream was required, there is no flow in “L”. When there isn’t any flow to a material stream, it is often convenient to hide the stream keeping the PFD more orderly. Right‐click on the “L” stream. Select Hide. The “L” stream disappears from the PFD. [Anytime you would like to reveal hidden objects, right‐click anywhere in the PFD workspace and select Reveal Hidden Objects.] This problem is based on Felder and Rousseau’s Elementary Principles of Chemical Processes 3rd Edition Example 9.5‐2 Results/Considerations: According to the simulation results, 1.53 x 105 kJ/h needs to be removed from the reactor to maintain a product stream temperature of 150 oC. The Felder and Rousseau hand calculations procured similar results. This problem is based on Felder and Rousseau’s Elementary Principles of Chemical Processes 3rd Edition Example 9.5‐2 ...
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This note was uploaded on 11/14/2011 for the course CHEN 4520 at Colorado.

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