REDUCTION OF NOX EMISSIONS FROM A DRY PRECESS PREHEATER KILN THROUGH THE USE OF THE NOXOUT PROCESS

The post combustion reduction of NOx using urea has proven to be an ef fective method in controlling NOx from various combustion, sources. Su ch a reduction process with the trade name NOxOUT has been successfull y demonstrated in a week-long test at Ash Grove's dry process cement k iln system located in Seattle, USA. This system is equipped with plane tary coolers, a 5-stage preheater and an air-through-the-kiln calciner . Testing was done under ten different kiln/calciner operating conditi o ns. Using th? ee to four injectors, NOx was efficiently reduced from 160 to 270 kg/h to less than 45 kg/h. This calculates to a NOx reduct ion, of greater than 80 % for most cases. Chemical utilization was gre ater than 50 %. A high degree of mixing and a long residence time at a n appropriate temperature present in the preheater tower contributed t o these excellent results. An average ammonia slip was 4, 0 ppm above a baseline level at a normalized stoichiometric ratio of 1, 0. This de monstration confirms expectations that dry process cement kilns with f our preheater stages are an ideal application. for the selective non-c atalytic reduction of NOx with urea. NOx was efficiently and effective ly reduced with minimal byproduct emissions and virtually no effect on plant operations.