Novel utilization of conditioner CaO for gas pollutants control during co-combustion of sludge and coal

CaO is a traditional desulfurizer used in coal combustion, and it is also a widely applied chemical conditioner in sewage sludge dewatering. In this study, the feasibility of co-combustion of CaO-conditioned sludge (Sc-CaO) and coal was discussed, including combustion characteristics and gas pollutants emission. The results show that adding 30% Sc-CaO into co-combustion strengthened the procedure of devolatilization and volatiles combustion (220-380 degrees C). But the main combustion performance (430-600 degrees C) was still similar to that of coal. Conditioner CaO could capture almost all the SO2 during sludge mono-combustion and 15.8-48.4% of SO2 during co-combustion. Meanwhile, conditioner CaO also contributed to N2O catalytic reduction and mitigated the NO increase caused by the co-effect of raw sludge and coal at 900 degrees C. Compared with physical additive CaO, conditioner CaO distributed evenly in sludge matrix and partially bonded to carbon, which was benefit to SO2 adsorption and N2O reduction. At the same time, the increase of NO was more mild than that caused by physical additive CaO. This study shows that co-combustion of Sc-CaO and coal is a suitable and promising technology for clean disposal of sewage sludge. (C) 2017 Elsevier Ltd. All rights reserved.