Two-dimensional model simulation of fixed bed catalytic reactors

A model system was developed for the prediction of concentration and temperature profiles in the radial and longitudinal directions in a fixed bed catalytic reactor. A cell model approach was utilized which resulted in an implicit set of nonlinear coupled algebraic equations representing component mass and energy balances. The Newton-Raphson iterative technique in conjunction with a banded coefficient matrix Gaussian elimination algorithm was used to solve the model equations. Experimental verification of the model consisted of three applications: (1) dehydrogenation of ethylbenzene to styrene, (2) oxidation of sulfur dioxide to sulfur trioxide, and (3) reaction of acetic acid and acetylene to form vinyl acetate. The styrene and sulfur trioxide data were obtained from the literature and the vinyl acetate data from a cooperative effort with an industrial plant. The systems chosen offered a variety of reaction situations, including endothermic and exothermic reactions and multiple reaction schemes. Experimental operating variables were varied over broad ranges and in multiple combinations. Model options tested included alternate kinetics, alternate forms of mass and heat transport terms and variable cell sizes. One-dimensional model comparisons are presented for all three applications. A comparison of experimental and calculated results for the systems studied indicate the simulation model developed offers an accurate approach. It is relatively simple in concept but quite general and flexible with regard to choice of alternate model options. Solution times were generally small, e.g., less than ten seconds on an IBM 360/65 computer