Effects of co-processing sewage sludge in cement kiln on NOx, NH3 and PAHs emissions.

Abstract The effects of co-processing sewage sludge in cement kiln on NO x , NH 3 and PAHs emissions were systematically investigated in a cement production line in Beijing. The results show that co-processing the sewage sludge was helpful to reduce NO x emission, which primarily depends on the NH 3 amount released from the sewage sludge. Meanwhile, NO x and NH 3 concentrations in the flue gas have a negative correlation, and the contribution of feeding the sewage sludge to NO x removal decreased with the increase of injection amount of ammonia water in the SNCR system. Therefore, it is suggested that the injection amount of ammonia water in SNCR system may reduce to cut down the operating costs during co-processing the sewage sludge in cement kiln. In addition, the emission of total PAHs seems to increase with the increased amount of the sewage sludge feeding to the cement kiln. However, the distributions of PAHs were barely changed, and lower molecular weight PAHs were mainly distributed in gaseous phase, accounted for the major portion of PAHs when co-processing sewage sludge in cement kiln.