Reduction of NOx Emissions from Cement Kiln/Calciner through the Use of the NOxOUT Process

Post-combustion urea injection has proven to be an effective method in controlling NOx from various combustion sources. This process, a selective non-catalytic reduction process known as NOxOUT, has been successfully demonstrated in a cement kiln/calciner operated by Ash Grove Cement. Testing was done under ten different kiln/calciner operating conditions. Using three to four injectors, NOx was efficiently reduced f rom 350 to 600 pounds per hour (3.5 to 6.0 lb / ton of clinker) to less than 100 pounds per hour (1.0 lb / ton of clinker). This calculates to a NOx reduction of >80% for most cases. Chemical utilization was greater than 50%. A high degree of mixing and a long residence time at an appropriate temperature present in the preheater tower contributed to these excellent results. An average ammonia slip was four ppm above a baseline level at normalized stoichiometric ratio of 1. Based on this demonstration, cement kiln/calciners have been identified as an ideal application for the NOxOUT Process. NOx was efficiently and effectively reduced with minimal by-product emissions and virtually no effect on plant operations.