Thesis (M.Eng.)--Chulalongkorn University, 2007

Circulating fluidized bed combustion has been received wide research attention due to its high combustion efficiency, high economic and environmental performances for burning low-grade coals, biomass and organic wastes. A circulating fluidized bed combustor can burn coal and limestone that capture sulfur dioxide in the combustion. The combustion takes place at moderate temperature resulting in reduction of NOx generated. In this paper, biomass from agricultural wastes including bagasse, bark and rice husk co-fired with lignite coal in circulating fluidized bed combustor is investigated. Commercial software with customized reaction model and kinetic subroutines is used to perform a simulation. We analyze the effects of various different operating parameters including combustion temperature, air flow rate, ratio of biomass in mixed fuel and type of biomass on the environmental performances and carbon combustion efficiency. Moreover, the effect of Ca/S molar ratio on sulfur retention is also studied. The presence of biomass in the feed significantly improves carbon combustion efficiency, and at the same time reduces amount of carbon dioxide, carbon monoxide and sulfur dioxide released.