Modeling De-NOx by Injection Ammonia in High Temperature Zone of Cement Precalciner

The quantity of NOx emission from cement production is second only to thermal power generation and vehicle exhaust. In this paper, a phenomenon found by Taniguchi is used to achieve NOx reduction in the cement precalciner. Based on his results, it is proposed to reduce NOx that ammonia is injected in the high-temperature and lean-oxygen zone (HT-DeNO(x)) during pulverized coal combustion. For a large cement precalciner (3200 t/d), numerical simulation is used to evaluate the technology of HT-DeNO(x) combined with the traditional selective non-catalytic reduction (SNCR) method. The results indicate that NH3 and HCN in HT-DeNO(x) can reduce NO during the reaction process. With very little ammonia injection (normalized stoichiometric ratio NSR=0.1, the normalized stoichiometric ratio), the efficiency of NO reduction by HT-DeNO(x) is 27.72%. Combining SNCR (NSR=1.1) and HT-DeNO(x) (NSR=0.1), the reduction efficiency will be improved to 60.05%, compared with 50.83% efficiency when using only SNCR at NSR=1.2.