31 Numerical Simulation of the Flow inside the Entrained Flow Gasifier

Gasification is making a strong comeback as a sustainable energy source in clean energy systems such as IGCC, and as a renewable source utilizing millions of tons of waste dumped in the landfill, and avoiding risking our ecological system as a result of ground water leaching, and CO₂ & CH₄ emissions. In this paper, reviews of the physical characteristics and conditions of the feedstock, gasification technologies, such as fixed bed, bubbling bed, the high-temperature entrained flow gasifier is first performed. Systematic gasification analyses for different feedstocks, including coal, biomass-coal blend, and industrial waste are presented. Species concentration and product∕feedstock ratios that define the gasifier metrics including cold gas efficiency, conversion rate, and steam and Oxygen requirements are computed. A baseline gasifier geometry is selected and discretized to carry out detailed CFD analyses. Mesh resolution study of the incompressible, turbulent flow is carried out. Two-phase flow representing the continuous and the discrete (particle) feedstock is analyzed while maintaining two-way coupling. The velocity field is compared with that of a single phase and results on the effect of the particle size and injection velocity is presented. A coupled thermochemical analysis is then carried out while incorporating the species transport for both the homogeneous (gas∕gas phase) and heterogeneous (gas∕solid phase) interaction. Species distributions, including, CO, H₂, CO₂, H₂O, and O₂ and other flow variables including temperature and velocity are computed and presented.