Mathematical modelling of fixed bed adsorption of aromatics and sulphur compounds in kerosene deodorisation

Abstract

A mathematical model that adequately predicts the effluent concentration and breakthrough profiles of aromatic and sulphur compounds in kerosene deodorisation has been developed. The contributions of radial transport (pore and surface diffusion) were incorporated in the mathematical formulations. Thus, the final model took into account the overall effect of both the solid and liquid phase mass transfer resistances. The resulting model expressions were coupled partial differential equations which were resolved into first order ordinary differential equations using the orthogonal collocation technique. The roots of the Jacobi orthogonal polynomials ( P N α, β ) with N=8 and α= β=0 were taken as the interior collocation points while the exterior points were ζ=1, z=0 and z=1. The fourth-order Runge Kutta method was then used to integrate the 4 N differential equations and the resulting functions were solved simultaneously to obtain the effluent and breakthrough profiles. Theoretical predictions from the model were compared with column adsorption data to ascertain the authenticity of the model. The agreement was good for both cases of aromatics and sulphur breakthroughs. The experimental breakthrough time of 8 h was predicted by the model. The breakthrough profiles also confirmed the formation of multiple adsorption layers.