Reducing NOx from existing cement kiln lines

In cement kiln lines, significant amounts of NOx emissions can be formed both in the rotary kiln and in the precalciner. To reduce NOx formation, low NOx techniques can be applied to the burner and to the combustion systems used in the rotary kilns and precalciners, respectively. These low NOx techniques have the dual advantage of (i) low CAPEX cost and (ii) no additional operating cost. When, and if, these combustion techniques cannot adequately reduce the NOx emissions to the levels mandated by increasingly stringent Local Pollution Control Boards, SNCR systems can be implemented to meet the most stringent NOx emissions, however, it is always best to first lower the 'baseline NOx levels' using low NOx combustion techniques since such techniques are able to be implemented at a fraction of the operating costs compared to the high costs of chemical reagents (aqueous ammonia or urea) for SNCR systems. This article deals with Low NOx combustion burners, low NOx techniques for precalciners, and the SNCR systems that suppliers can provide for NOx reduction in cement lines, with some examples and case studies.