Simulation of the co-gasification of Kentucky coal and biomass in an entrained flow Gasifier

Gasification gives the solid hydrocarbon waste a better chance to be used efficiently through the combined cycle and at a much less harmful emission. Co-gasification of municipal solid waste, and biomass or industrial waste that hold a large fraction of hydrocarbon is emerging as a common practice to reduce their environmental impact. However, the gasifier conditions and design need to be adjusted according to the composition of the feedstock, and that needs to be tuned and optimized. This work assesses the gasification conditions of three different Kentucky coal and biomass mixtures (10% biomass, 25% biomass and 50% biomass) in an entrained flow gasifier. It is presented numerically in an attempt to obtain a comparative analysis between the optimum operation conditions for the three feedstocks. The numerical model uses an Eulerian-Lagrangian approach, with discrete-phase model of feedstock in a continuous model of oxidant. This model also takes into account the turbulent flow (SST k-ω model), gas phase gasification (Species Transport), particles devolatilization (Kobayashi Two-Competing Rate model), heterogeneous char reaction (Multiple Surface reaction), particle dispersion by turbulent flow (Stochastic Discrete Random Walk model), radiation (P1 model) and solid particle distribution (Rosin Rammler model). The temperature distribution and product distribution of the developed model is captured. There was an increasing trend, from 10% biomass to 50% biomass, of the gas composition of CO2 and H2O in the gasifier. However, there was a decreasing trend, from 10% biomass to 50% biomass, of the gas composition of CO and H2. The role of particle size showed that larger sizes (534nm) gives less syngas yield as compared to smaller sizes (134nm).