An efficient chemistry-enhanced CFD model for the investigation of the rate-limiting mechanisms in industrial Chemical Vapor Deposition reactors

Abstract

An efficient CFD model for the deposition of alumina from a gas mixture consisting of AlCl3, CO2, HCl, H2 and H2S in an industrial CVD reactor with multiple disks and a rotating feeding tube, is proposed. The goal is twofold: (i) to predict the thickness of the deposited material, (ii) to investigate whether the process rate is determined by the reaction rate or by diffusion. A reaction model that consists of a gas-phase homogeneous reaction and a heterogeneous reaction is implemented, with a proposed kinetics rate that includes the effect of the H2S concentration. The latter has a catalytic effect, but the mechanism is not entirely understood. The entire reactor geometry (consisting of 40–50 perforated disks) is divided into appropriately chosen 7-disk sections. The 2D, time-dependent CFD model is validated using production data for the deposition thickness. The proposed computational tool delivers accurate predictions (average relative error 5%) for different geometries corresponding to real reactor set-ups. Extending the functionality beyond prediction, a computational experiment is performed to illuminate the interplay between species diffusion and chemical reaction rates, which determines the rate-limiting mechanism. The results indicate that species diffusion is fast enough and therefore reaction kinetics determine the overall deposition rate.