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Optimization of an advanced coal-fired integrated gasification combined cycle system requires an accurate numerical prediction of gasifier performance. While the Lagrangian discrete phase formulation has been widely used in comprehensive computational fluid dynamic (CFD) gasifier models, the accuracy of submodels requires further improvement. Built upon a previously developed CFD model for entrained-flow gasification, the advanced physical and chemical submodels presented in this paper include a moisture vaporization model with consideration of high mass transfer rate, a coal devolatilization model with more species to represent coal volatiles and heating rate effect on volatile yield, and careful selection of global gas-phase reaction kinetics. The enhanced CFD model is applied to simulate two typical oxygen-blown entrained-flow configurations including a single-stage down-fired gasifier and a two-stage up-fired gasifier. The CFD results are reasonable in terms of predicted carbon conversion, syngas exit temperature, and syngas exit composition. The predicted profiles of velocity, temperature, and species mole fractions inside the entrained-flow gasifier models show trends similar to those observed in a diffusion-type flame. The predicted distributions of mole fractions of major species inside both gasifiers can be explained by the heterogeneous combustion and gasification reactions and the homogeneous gas-phase reactions. It was also found that the syngas compositions at the CFD model exits are not in chemical equilibrium, indicating that the kinetics for both heterogeneous and gas-phase homogeneous reactions are important. Overall, the results achieved here indicate that the gasifier models reported in this paper are reliable and accurate enough to be incorporated into process/CFD cosimulations of IGCC power plants for system-wide design and optimization.

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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.