Co-combustion of coal with rice husk and bamboo in power generation

In many Asian countries Coal is frequently used a major fuel in power plants. Burning coal creates quite a lot of environmental problems when compared to other cleaner fuels such as natural gas. Experimental study of co-combustion of coal and biomass was conducted in a laboratory scale combustion facility to evaluate the combustion and pollutant emission performance under different operation parameters. Rice husk and bamboo were used as the biomass fuels in this study. This paper reported the influence of the biomass blending ratio in the fuel mixture and the excess air ratio on the combustion behavior. It was noted that the combustion temperature and the energy output from the co-firing process were reduced compared to coal combustion alone owing to the fact that biomass has lower heating value compared to coal. However, the high volatile matter (VM) content of biomass improved the combustion time scale so that the carbon monoxide (CO) emissions were reduced substantially. In addition, the fuel nitrogen and sulfur content in biomass were lower than that of coal and hence suppressed the formation of nitrogen oxides (NO_x) and sulfur dioxide (SO₂) during the cocombustion process. The increase of excess air ratio also affected most of the pollutant emissions. The pollutant emission per unit energy output at different excess air ratios and biomass blending ratios were studied in detail in this paper. Attention should be paid to the high potential of slagging and fouling in the boiler when co-firing coal with biomass.