Introduction Model of the Haber-Weiss process for the synthesis of ammonia from nitrogen and Hydrogen according to: N 2 + 3H 2 → 2NH 3 The reaction rate is a nonlinear function of the reactant and catalyst concentrations, temperature, and pressure In addition to the active reaction participants, argon (Ar) and methane (CH 4 ) make up the balance of the reactant and product streams 2
Introduction This example shows how to: –Import thermodynamic data into COMSOL, –Create complex, non-linear functions for activities, reaction rates, and the equilibrium constant –Create useful interpolations to determine the efficiency of the catalyst –Set up the simulation of a cooled plug flow reactor (PFR) 3
Model Description 4
6 P/atmb0b0 b1b1 b2b2 b3b3 b4b4 b5b5 b6b · · · · · · Rase, H. F: Chemical Reactor Design for Process Plants, Volume 2: Case Studies and Design Data, 1977
Model Description 7
Results and Discussion The concentration profile for hydrogen, nitrogen and ammonia are shown in figure 1 The seemingly low final concentration of ammonia in the reactor is in fact due to the exothermic nature of the reaction and the subsequent influence on the behavior of the equilibrium constant The exothermic behavior can be seen in figure 2 The results thus obtained satisfactorily match the cited source in Ref. 1 9
Results and Discussion 10 Figure 1: Mole fractions for hydrogen (green), nitrogen (blue), and ammonia (red) as a function of reactor extent.
Results and Discussion 11 Figure 2: Temperature profile within the ammonia conversion reactor.