Dual-Bed Gasification of Petcoke: Model Development and Validation

Abstract

In this work, the problem of modeling a previously proposed dual-bed gasification scheme [Sudiro et al., Energy Fuels 2008, 22, 3894−3901] is addressed. The process consists of a combustor and a gasifier, which are thermally coupled by the circulation of an inert solid, to use air instead of pure oxygen in the combustor. The coal gasification reactor is modeled, taking into account both chemical kinetics and mass transfer between gas phase and char particles. First, the model is developed and validated with reference literature and experimental data for conventional coal gasification using oxygen in both entrained-flow and fluid-bed gasifiers. A series of sensitivity analyses is performed with regard to a conventional gasifier fed by petcoke, and the effects of residence time and oxygen/carbon mass ratio in the feed are investigated over three process variables: char conversion at the gasifier exit, temperature at the gasifier exit, and amount of useful syngas (H2 and CO) produced, in terms of N m3 per ton of petcoke. Finally, the model is extended for application to the dual-bed process. Results from this simulation are compared to those obtained under equilibrium conditions, with an energetically equivalent syngas throughput.