KINETIC MODELING OF NITRIC AND SULFUREOUS SPECIES CONVERSION IN CH4 FLAMES UNDER HIGH-CONCENTRATION CO2 ATMOSPHERE

摘要

During oxy-fuel combustion, the release of S, N from coal as well as its transformation in flue gas are different from that in conventional combustion. The behavior of different sulfur, nitrogen components such as HCN,NH3,NO and H2S have been investigated in CH4 flames under high -concentration CO2 atmosphere by means of chemical kinetic modeling, moreover, the effects of temperature, equivalence ratio, CO2 concentration, etc. on the formation of NO and SO2 have been well discussed. Results indicate that under fuel-rich condition, comparing with O2/N2 atmosphere, the conversion of NH3 and HCN is accelerated while the reduction of NO is inhibited in O2/CO2 atmosphere; when the initial CO2 concentration increases, both the oxidation (forming NO) and reduction (forming N2) of NH3 and HCN are improved, but the reduction rate of NO decreases, furthermore, the content of total N (NH3+HCN+NO) decreases continuously. Under fuel-lean condition, comparing with O2/N2 atmosphere, the oxidation of NH3 and HCN to NO is inhibited in O2/CO2 atmosphere; simultaneously the reduction of NO is promoted; when the initial CO2 concentration increases, the conversion rates of NH3, HCN, NO to N2 grow gradually. When the temperature increases, the reduction rate of NO increases firstly and then decreases under the fuel-rich condition, while the change of the rate is reversed under the fuel-lean condition, the reduction of NO is more favorable in high-concentration CO2 atmosphere at high temperature. Under fuel-lean condition, the formation of SO2 is suppressed in CO2 atmosphere, but the final SO2 concentration is almost the same as that in O2/N2 atmosphere; under fuel-rich condition, the formation of SO2 is promoted by high concentration of CO2.