Chemcad Reactor Design Tutorial

March 22, 2018 | Author: Erich Escobar | Category: Chemical Reactor, Stoichiometry, Distillation, Ammonia, Chemistry


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Description

CHEMCAD reactor design tutorialConsider a hydrogen/nitrogen feed stream with the following properties Temperature 500 K Pressure 100 atm Composition 20 mole% N2, 80 mole% H2 Flow rate 1000 kgmol/hr In this sequence of CHEMCAD design examples, we examine several different approaches to designing a reactor to carry out ammonia production by the Haber process: N2 + 3H2 <==> 2 NH3 The reactor specifications are as follows Adiabatic reactor Pressure 100 atm Pressure drop 1 atm Molar conversion of N2 0.5 Stoichiometric/Equilibrium reactor design procedure 1. Start the CHEMCAD application; choose menu item File -> New Job and save as a folder on your computer's desktop. 2. Select the arrow from the top-left corner of the main palette, then click on Stoichiometric or Equilibrium reactor. Click add main symbol and place the reactor. 3. Then place, by selecting from the main palette, the input arrow (red arrow) and output arrow (purple arrow). Place the arrows accordingly near the reactor. 4. Next use the stream button (second row, and second column of the main palette) to connect the input arrow to the top of the reactor, and the bottom of the reactor to the output arrow; blue dots represent equipment feed streams and red dots represent equipment outlet streams. 5. Change the pull down menu on the toolbar from flowsheet to simulation. o Set pressure and pressure drop. set fractional conversion to 0. . for more reactions. o Specify the following stoichiometric coefficients: hydrogen: -2. hydrogen (1) and ammonia (63). ammonia: 2.6. Gibbs reactor design procedure 1. ammonia: 2. nitrogen: -1. component flows should be mole fractions. 12. Also. For the Stoichiometric reactor specify the following: o Specify thermal mode to adiabatic. change pressure to atmospheres. o Specify thermal mode to adiabatic. 2. set fractional conversion to 0. From the solution report obtained from Output -> Report click on the Calculate and Give Results button. Next. After making these choices. 11. o Set reactor pressure to 100 atm. 8. The stoichiometric reactor can only specify one reaction. Click add main symbol and place the reactor. Enter the feed properties listed above. then click on Gibbs reactor. Double-click on the square input stream box to specify input stream properties. 10. Select the arrow from the top-left corner of the main palette. then [OK] o Select nitrogen as the key component. For the Equilibrium reactor specify the following: o Specify the number of reactions as 1. o Specify the reaction to take place in the vapor phase. Note that reaction information in the Equilibrium reactor is similar in form to that used for reactive distillation in the SCDS (distillation) column module. if any. double-click on the reactor. correct errors. Select Thermophysical -> Component List and add nitrogen (46). choose menu item File -> New Job and save as a folder on your computer's desktop. 7. select Run -> Run All.5. nitrogen: -1. o Choose reaction conversion. From the main menu. Start the CHEMCAD application. o Specify the following stoichiometric coefficients: hydrogen: -2. Choose menu item Format -> Engineering Units to select SI units for this problem. Click OK until you are through all the menus that come up. click OK. 9. one must use the equilibrium reactor module.5. o Select nitrogen as the key component. choose menu item File -> New Job and save as a folder on your computer's desktop. Next use the stream button (second row. Set the reaction phase to [1 Vapor or mixed phase] and press OK and OK at the Component Element Matrix. and second column of the main palette) to connect the input arrow to the top of the reactor. 2.PFR with zeroeth order reaction 1. correct errors. 10. Kinetic reactor design procedure . Also. by selecting from the main palette. 11. Then place. Place the arrows accordingly near the reactor. 8.3. 5. and the bottom of the reactor to the output arrow. the input arrow (red arrow) and output arrow (purple arrow). Double-click on the square input stream box to specify input stream properties. 4. Click OK until you are through all the menus that come up. Choose menu item Format -> Engineering Units to select SI units for this problem. Select Thermophysical -> Component List and add nitrogen (46). Then place. Change the pull down menu on the toolbar from flowsheet to simulation. From the main menu. if any. Specify the thermal mode to adiabatic. double-click on the Gibbs reactor. 4. change pressure to atmospheres. Place the arrows accordingly near the reactor. Select the arrow from the top-left corner of the main palette. 6. blue dots represent equipment feed streams and red dots represent equipment outlet streams. blue dots represent equipment feed streams and red dots represent equipment outlet streams. 5. From the solution report obtained from Output -> Report click on the Calculate and Give Results button. Change the pull down menu on the toolbar from flowsheet to simulation. then click on Kinetic reactor. hydrogen (1) and ammonia (63). After making these choices. by selecting from the main palette. the input arrow (red arrow) and output arrow (purple arrow). 3. component flows should be mole fractions. click OK. Start the CHEMCAD application. Next use the stream button (second row. and second column of the main palette) to connect the input arrow to the top of the reactor. Next. 7. Click add main symbol and place the reactor. . select Run -> Run All. Enter the feed properties listed above. and the bottom of the reactor to the output arrow. 9. and 2 for ammonia. double-click on the Kinetic reactor and specify the following: o On page 1 of the specifications set the number of reactions to 1. set the respective Exponential coefficient to 1e-20 (again. 10. o On page 3 (More specifications) set the reaction units to: Concentration flag to moles/vol. From the solution report obtained from Output -> Report click on the Calculate and Give Results button. 11. hydrogen (1) and ammonia (63). pressure drop to 1 atm. Select Thermophysical -> Component List and add nitrogen (46). pressure to 100 atm. Click OK until you are through all the menus that come up. o On page 2 set the Frequency factor to 5 and Activation energy to 1e-20 (CHEMCAD will treat these essentially as zero). 9. time to hrs. -1 for nitrogen. volume to m3. Also. and mass flow to kg. From the main menu. and select Standard kinetic expression. for these components. o Set the switch to Specify volume. . component flows should be mole fractions. Activation energy to K Joules. 7. click OK. Next.6. Choose menu item Format -> Engineering Units to select SI units for this problem. if any. Calculate conversion and set the reactor volume to 10 m3. molar flow to K moles. adiabatic operation. Double-click on the square input stream box to specify input stream properties. After making these choices. select Run -> Run All. leave all other reaction parameters blank except the stoichiometry coefficients which should be set to -3 for hydrogen. change pressure to atmospheres. correct errors. to force the values to zero). Enter the feed properties listed above. 8. o Specify the reactor as a PFR with vapor phase reaction only.
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