Investigation on Co-Combustion Characteristic of Paper Mill Waste and Coal in Circulating Fluidized Bed

Abstract

Experimental research on co-combustion of paper mill waste and coal was conducted in a pilot circulating fluidized bed combustor with a cross section of 0.23×0.23m2. Mixed waste of paper mill sludge and process residue from a paper company and bituminous coal were used in the experiments. The temperature distribution in the combustor was measured. The bottom ash and fly ash were sampled and analyzed. Six gas components were analyzed with a gas analyzer. The effects of some parameters, such as waste variety, fluidization velocity, secondary air rate, excess air, on the combustion characteristics and the emission of SO2 and NOx were clarified. The experimental results indicate that the incinerator temperature decreases with increase in secondary air rate and waste/coal mass ratio for the waste/coal mass ratios tested. When the excess air ratio increases, the dense bed temperature increases, but the temperature in the dilute phase region first increases, and then it decreases with further increase in the excess air ratio. The combustion efficiency increases with increase in the secondary air rate and decrease in the waste/coal mass ratio. With increase in the excess air ratio, the combustion efficiency first increases, then it reaches a peak and finally decreases. For the waste/coal mass ratio of 1.0, the highest combustion efficiency corresponds to the excess air ratio of 1.25. Higher desulfurization efficiency can be obtained with higher excess air, proper incinerator temperature and lower secondary air rate. The NO emission increases with increase in excess air ratio and decrease in the secondary air rate. Higher temperature, stronger staged air injection and lower excess air ratio are beneficial to suppressing N2O emission from incineration. The emission can be reduced by decreasing excess air ratio, increasing incinerator temperature and secondary air rate.