Cement Kiln Selective Non Catalytic Reduction (SNCR) Research And Staged Combustion

Nitrogen oxides (NOx) is one of the major sources of air pollution caused by the maincomponents including NO, NO2, N2O3,N2O4, N2O5, etc. Since NO, NO2and N2O3easilydissolved in the rain, forming acid rain, polluting the environment. Cement as the largestamount of building materials, in2013, the production reached2.4billion tons. And the clinkerproduction reached1.6billion tons. However, the cement manufacturing processes not onlyrequire large amounts of energy and resource, but also discharge a lot of emissions, includingCO2and nitrogen oxides. As the combustion air in the oxidation of molecular nitrogen andnitrogen in the fuel, which reacts with oxygen to produce NO, NO2and N2O3, etc.(referred toas NOx). NOxis directly discharged to the atmosphere would have a serious environmentalpollution. Therefore, how to reduce or eliminate the production of NOx emissions in cementkilns industrial is an important topic of cement production technology and environmentalprotection.In this study, the systematic analysis which including the selective non-catalytic reduction(SNCR),multilevel combustion of gas and fuel that to decrease NOx were carried out. Thepractice has proved that the advanced equipment, optimized system designing andindispensable technical measures can reduce more than50%NOx emissions of pre-calcinerkiln compared to the existing kiln system.Precalciner cement kilns could use selective non-catalytic reduction (SNCR) whichutilize amine compounds reduction of fuel combustion flue gas NOx at high temperatures of800~1100℃. Tests showed that at the temperature about900℃, injected into25%aqueous ammonia to a cement kiln can control NOx emissions <140mg/m3or less.And moreimportantly, the technology is simple process of cement kiln system and the transformation issmall, also,the effect is significant.Multilevel combustion of gas and fuel technique, namely the decomposition furnace byadjusting the fuel and combustion air three times and match the order of the relationship, sothat part of the calciner combustion zone is weakly reducing combustion environment throughreduction reaction occurs at high temperature to reduce the NO decomposition furnace fuel formation and reduction of thermal NO already formed part of the kiln. The results showedthat, NOx reductions of30to50%can be achieved. Due to the need to transform thedecomposing furnace, so the process is relatively high initial investment, but also the capacityto calciner at least more than1200m3.Through comparing selective non-catalytic reduction (SNCR) with two stagedcombustion technique.The SNCR reduce the economic effect of nitrogen applied in cementkilns analysis. But the cost of the late greatly increase and produce secondary pollution.So it isnot a long-term development of enterprises;Meanwhile the two staged combustion can usesludge as part of the fuel, not only can reduce the consumption of coal, but also be able tohandle large amounts of sludge community, has great social value.