Staged Combustion + SNCR Process In Dry Cement Kilns Denitration Project Examples Use

Emissions of nitrogen oxides of cement industry has become China’s third largest emitter, only after the emission of thermal energy and automobile exhaust. On August6th,2012, the State Council issued the "twelfth five-year" plan on "energy conservation and emissions reduction", and the cement industry is put forward for the key industry of NOx emission reduction. In the mean time," The cement industry air pollutants emission standards "(GB4915-2004) provides that NOx emission concentrations of the cement plant can not be exceed800mg/Nm3. Local emission standards in Hunan province even specified the concentration of NOx not more than400mg/Nm3.With the ascension of technology level, emissions standards will be gradually improved.This paper studies the existing technology--"low nitrogen combustion" and "SNCR" denitration, which the cement plant commonly used, however, was found that the denitration efficiency is difficult to reach60%in general, also, the concentration of NOx can not be stably around400mg/Nm3.Moreover,"low nitrogen combustion "didn’t play the biggest benefit in low nitrogen combustion control. In addition, for the SNCR technology, injection point and the control of injection quantity of reductant such as ammonia or urea are still need optimization. Further more, the denitration cost is not low.This paper integrates technology---"2500t/d NSP cement kiln denitration project of J Company", which is studied by H Research Institute. By adopting "staged combustion+selective non catalytic reduction" process, many content is studied. For example, how to reduce nitrogen oxides generated in staged combustion; how to control the production of nitric oxide in the whole process and improve the efficiency of emissions; in addition, how to control ammonia decomposing furnace spray position and spray ammonia, ammonia slip in SNCR, etc. By adjusting the reaction temperature, residence time, the stoichiometric ratio, the reducing agent and the mixture of flue gas to control such factors in order to affect denitrification efficiency. The final solution is to overcome the technical difficulties of cement kiln denitration efficiency, additionally, eventually to make the concentration of NOx steadily less than300mg/Nm3.