Cement kiln NO/sub x/ control

Cement kilns represent an important source of NO/sub x/ emissions. The results of a critical analysis of the state-of-the-art in cement kiln NO/sub x/ control are presented. A survey of current and anticipated cement kiln NO/sub x/ regulations, NO/sub x/ formation mechanisms and common NO/sub x/ control technologies (as applied to boilers) is presented. Cement kiln features relating to NO/sub x/ control, such as combustion characteristics and temperature and residence time profiles, are outlined. A comparison is made of NO/sub x/ control technologies applicable to cement kilns. These include combustion, modifications, low NO/sub x/ burners, staged combustion, selective noncatalytic reduction, and selective catalytic reduction. The criteria for comparing these NO/sub x/ control technologies include the principle of operation, technical feasibility, potential NO/sub x/ reduction, relative cost, and the potential effects on clinker quality. Conclusions and future directions in cement kiln NO/sub x/ control are discussed.>