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This work deals with the development of mathematical techniques for incorporating existing sulfation models into a CFD code for simulation of the flow and heat and mass transfer in multi-phase reacting flow; i.e. in the combustion of pulverized coal with the dry type sulfur absorption process. By compromising the ability to maintain some features of the sulfation, as suggested in literatures with computation time, the model was successfully embedded into FAFNIR, a CFD code by Lockwood et al. and has been used for prediction of SO2 absorption in pulverized coal combustion to compare with experimental data at various conditions. This paper focuses on mathematical representation of the sulfation process by including the effects of temperature on the reaction rate at zero sulfation and during increased sulfate loading or accumulation of product layers. The model is relatively simple and is applicable over a wide range of temperatures, particle sizes and SO2 concentrations. Validation was performed and it was found that the model satisfactorily represents the amount of accumulated sulfate within the entire domain of calculation.

Co-combustion of high moisture municipal solid waste (MSW) and high sulfur Thai lignite in a laboratory scale bubbling fluidized bed has been investigated. This paper presents the effects of the mass fraction of a model MSW in the fuel mixture, as against 100% lignite, on the combustion characteristics that may be inferred from temperature distributions, carbon combustion efficiency and CO and CO 2 concentrations and on the emissions of major gaseous pollutants, including CO, SO 2 , NO and N 2 O. The influence of excess air and secondary air on those characteristics are also discussed. The results show that within the 40% MSW fraction tested, co-combustion is characterized by enhanced combustion of volatiles in the freeboard, a lower bed temperature and a combustion efficiency drop of up to 8%. Co-combustion either increases or reduces CO emission depending on the percentage of excess air. Reduction of up to 7–18% of SO 2 is observed at the 40% MSW fraction for the range of excess air and secondary air tested. Both NO and N 2 O increase slightly with increasing fraction of MSW. Within the range of experimental conditions tested, the optimum condition for co-combustion in view of combustion efficiency and CO, NO and N 2 O emissions is: 20% MSW, 40% excess air and 0.2 secondary to total ratio, although the reduction of SO 2 is slightly smaller than at other conditions.