Improvement in Reactivity and Pollutant Emission by Cofiring of Coal and Pretreated Biomass

A fuel pretreatment technique is one of the most effective ways of using biomass fuel to solve problems including disadvantages of low calorific value, slagging, and fouling. Biomass fuel can gain a high calorific value and lower ash content by torrefaction and ash removal technology, respectively. In this study, a thermogravimetric analysis for deriving combustion parameters and the combustion characteristic factor (S) and an evolved gas analysis for investigating emission characteristics were studied by using a thermogravimetric Fourier transform infrared (TG-FTIR) system with coal, biomass, pretreated biomass, and their blends (10, 20, and 30%) to evaluate the combustibility and environmental performance. In the thermogravimetric analysis, coal and ashless biomass blends showed the greatest combustion performance and were confirmed to have a higher S index. Gas emissions (CO2, CO, NO, and SO2) were also investigated during the combustion process (O-2, 21%; N-2, 79%) to compare coal and biomass blends with coal and pretreated biomass blends. These results, including the emission peak and integral value, generally decreased as the biomass blending ratio increased except for the NO emission. The SO2 emission decreased only with an increase in the ashless biomass owing to the lower sulfur content in ashless biomass. Overall, this study indicated that blending pretreated biomass, especially ashless biomass, is more effective toward better cocombustion and environmental behavior as the biomass blending ratio increases.