PFR and CSTR comparison

This problem uses ASPEN simulations to compare the performances of a Plug Flow Reactor (PFR) and Continuously-Stirred Tank Reactor (CSTR) in terms of required volume to reach a particular conversion of a reaction under the same conditions for both reactors. The reaction system to be compared is shown below:

1. Butane (C4H10) is to be isomerized to isobutane in a plug-flow reactor. This liquid-phase elementary reaction is done adiabatically at a high pressure (25 atm). A feed stream of 0.9 mole fraction regular n-butane and 0.1 mole fraction i-pentane (an inert molecule also known as 2-methyl-butane) is introduced to the reactor at 330 K, 25 atm and at a rate of 160 kmol/hr. The kinetic data for the forward and reverse reactions are as follows:

   • Forward: k=0.008639; E=6.57e+07 J/kmol; To=360 K

   • Reverse: k=0.003442; E=7.26e+07 J/kmol; To=360 K

The images below show the corresponding tables, plots, and handwritten work used to reach the conclusion of this problem. The first image shows a sensitivity analysis that plots product stream composition vs PFR length, the second image is a sensitivity analysis that plots reactant mole fraction (butane) vs CSTR volume, and the third image shows a table that displays the same values as the second image. The last image takes advantage of the information shown in the plots and tables, along with some mathematics as well, in order to compare required volumes for each reactor to reach 70% conversion of the reaction. It is shown that the PFR requires a lower volume to run this reaction as opposed to the CSTR, which would indicate that the PFR is the better-performing reactor.