| Chinese cement industry is growing rapidly and has become the second mainsource preceded by coal power on NOxemission. Controlling the emission of NOxincement industry is under huge pressure. Oxy-fuel combustion technique is a new type oftechnique with high efficiency and low pollution. Applying this new technique, theconcentration of CO2in the burned exhausted gas can be higher than70percent.Meanwhile, it can reduce the emission of gas like SO2, NOxand so on, which would cutdown the harm of coal-firing to the environment. This research mainly focuses on theemission features of NOxfrom coal-firing in cement industry with oxy-fuel combustiontechnique.First, with thermo gravimetric analyzer, non-isothermal firing test of two differentindustrial coals were carried out under the condition of O2/N2and O2/CO2,and thefeature parameter and property index of coal-firing were calculated. The results showedthat with the oxygen concentration at21%, the ignition temperature of coal powder Ti,highest burning rate temperature Tmaxand burned temperature Thwere found laggedwith N2replaced by CO2.The ignitable index and the burning featured parameter of coalpowder were worse. With the increase of oxygen concentration, the burning features ofcoal powder were improved under the condition of O2/CO2.Second, on the testing platform of the rotary furnace, the influence of O2/N2andO2/CO2and oxygen concentration on the emission of NO was investigated with theaddition of limestone and CaO under the condition of enriched oxygen. The resultsshowed that the amount of NO emitted from coal powder burning under the condition ofO2/CO2was relatively less than that of O2/N2.The increase of oxygen concentration could promote NO emission from coal powder burning under the condition of O2/CO2.CaCO3could enhance the emission of NO from coal powder burning under thecondition of low temperature and low oxygen concentration; CaO could enhance theemission of NO from coal powder burning under the condition of high temperature andlow oxygen concentration; The effect of CaCO3and CaO on the emission of NO fromcoal powder firing weakened with the increase of Oxygen concentration under thecondition of O2/CO2, and CaO was found more effective than limestone.At last, by using pilot testing platform, NO emissions from coal powder burningwere compared between under air condition (with the participation of raw material) andunder condition of the O2/N2with high concentrated oxygen. The results showed thatunder the air condition (with raw material), the average NO concentration at the outletof calciner was17.82%higher than that of air coal burning condition. Under thecondition of enriched oxygen, the average NO concentration of calciner outlet gas was53.48%higher than that of air coal burning condition. |
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