TITLE: Numerical strategies in solving gas-liquid reactor models.

AUTHOR: J. Romanainen.

INST.  AUTHOR: Abo Akademi, Turku (Finland). Lab. of Industrial Chemistry.


PUB.  TYPE: Thesis

PUB.  COUNTRY: Finland

SOURCE: Department of Energy [DEE],  1994,  199p.  ISBN: 951-650-379-9



Gas-liquid reactions are frequently used in industry to carry out e.g. various oxidation, hydrogenation and chlorination processesor absorption, where reacting components are used to enhance absorption. The modeling of the two phenomena present in gas-liquid reactors - the reaction enhanced mass transfer through the phase interface and the bulk phase reactions - leads into specified mathematical problems depending on the reactor type.  This study provides some insight on the numerical strategies and methods available for solving the mathematical problems arising from gas-liquid reactor modeling. The numerical aspects of various solution strategies and discretization methods are considered for both steady state and dynamic reactor models. The modeling and the numerical solution of isothermal tank reactors and bubble column reactors was studied with various reaction kinetics including a single first order irreversible reaction, some autocatalytic reactions and two competitive-consecutive second order reactions. Conclusions and recommendations are given on the applicability of various strategies and discretization methods. Simultaneous and sequential strategies were tested together with discretization methods based both on finite difference and orthogonal collocation. A novel outlet boundary condition for the axial dispersion model was introduced. Also a simple grid refinement scheme for the finite difference discretization was presented. Some important gas-liquid reactions are by absorption in alkaline liquids