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UBC Theses and Dissertations

Co-gasification of biosolids with biomass in a bubbling fluidized bed Yu, Ming Ming


This thesis project studied the feasibility of co-gasification of biosolids with biomass as a means of disposal with energy recovery. The kinetics and gasification performance of biosolids and biomass mixtures were studied with a thermogravimetric analyzer and a pilot scale bubbling fluidized bed, respectively. From the kinetics study, it was found that biomass, such as switchgrass, could catalyze the gasification reactions because the ash of switchgrass contained a high proportion of potassium, which is considered as an excellent catalyst for gasification processes. However, it was found that biosolids could also inhibit gasification. When biosolids were mixed with biomass, the inhibition effect overwhelmed the catalytic effect. For the study of gasification performance, the impacts of biosolids proportion in the fuel, bed temperature, and steam/fuel ratio on gasification performance were investigated. As the biosolids proportion increased from 0 to 100%, syngas yield decreased from 1.38 to 0.47 m³/kg, char conversion decreased from 81.7% to 35.5%, tar content increased from 10.3 to 200 g/m³, and ammonia concentration increased from 1660 to 19200 ppmv. A synergistic effect occurred at 25% biosolids. With increasing biosolids proportion in the fuel, H₂ and CH₄ increased, CO decreased, and CO₂ remained nearly constant in the syngas. As the steam/fuel ratio increased, the concentrations of H₂ and CO₂ increased, while that of CO decreased in the syngas. Decreasing the bed temperature from 825 to 728℃ did not affect syngas composition, but decreased the syngas yield from 0.99 to 0.29 m³/kg

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