An advanced gas—solid flow engineering model for a fluidized bed reactor system

Abstract

A literature survey shows that there are two approaches to mathematically describe gas-solid two-phase flow and reaction in the fluidized bed reactors. One approach is a very simplistic engineering reactor model, and the other approach is based on a rigorous Computational Fluid Dynamic (CFD) model. Despite significant progress on numerical methods, CPU capacity and performance, and theories describing gas-solid flow, CFD based reacting flow modeling is far from being a routine tool for designing new reactors. Thus, simpler reactor models are still the main method for providing guidance for fluidized bed reactor design and optimization. However, traditional reactor models have considered too many simplifying assumptions that create inconsistencies in the governing equations of the boundary conditions such that it can result in erroneous prediction. In the current paper, an advanced gas-solid two-phase engineering reactor model has been developed for flow, heat transfer and reaction in the riser reactor of a circulating fluidized bed system. In contrast to CFD, this model can use as input parameters the hydrodynamic information obtained from published literature or experimental measurement such as axial and radial profiles for solid volume fraction, gas velocity and gas dispersion coefficient. While the hydrodynamics can be as accurate as measured, this advanced engineering reactor model is also coupled with either simple power law or the most rigorous kinetic models that involve elementary reactions. In this way, we can extract heterogeneous reaction kinetics from pilot plant or production reactor data directly. Model validation with pilot plant data and tracer data for a riser reactor will be presented and the short falls of traditional treatment of engineering fluidized bed reactor models will also be discussed.