Application of Particle Population Model To Determine the Contribution to Slag, Flyash, and Syngas in Entrained Flow Gasification from Particle Size Distribution

During entrained coal gasification any inefficiency in the slagging process leads to overall process inefficiencies and fouling of downstream equipment. A coal particle population model was developed to evaluate the conversion and partitioning of diverse heterogeneous coal particles into slag and flyash. A Pittsburgh No. 8 coal sample was separated into four gravity fractions by float sink separation. Each density cut was further separated into seven size fractions. These fractions were individually characterized to evaluate the resulting conversion and partitioning into slag and flyash. The sticking probability varied among the four specific gravity fractions as a function of temperature while little or negligible variance among the size fractions was observed for conventional viscosity models. However, this was not the case, when using the contact angle to account for the influence of carbon. By expressing the contact angle as a function of carbon content and the temperature of critical viscosity, the behavior of reacting coal particles striking the gasifier wall could be evaluated. Capture efficiencies were predicted to be higher for particles from smaller size and lower specific gravity fractions. A sensitivity analysis indicated that decreasing the amount of the larger size fractions reduces the formation of flyash since it increases mineral capture in slag, with a slight increase in syngas production due to the larger carbon conversion in smaller size fractions versus larger size fractions.