O_2/CO_2燃烧条件下NO_2还原特性的实验研究

Experimental Investigation on the NO_2 Reduction Property under O_2/CO_2 Combustion Condition

为探究O_2/CO_2燃烧条件下NO_2的还原特性,利用固定床反应实验系统,研究了温度、矿物质、灰分以及反应气氛变化对NO_2还原行为的影响规律与作用机理。实验结果表明:NO_2的还原率随反应温度升高而增大,当反应温度大于873K时,NO_2还原反应显著加快;反应温度为1 073K时,NO_2还原率达到90%以上。煤灰中主要的矿物质成分对NO_2还原过程表现出催化促进作用,相应矿物质催化NO_2还原的活性顺序为Fe2O3>MgO>CaO>Al2O3>Na2CO3>K2CO3>SiO_2。准东煤灰中活性矿物质成分含量较高,煤灰对NO_2还原的催化活性顺序为五彩湾煤灰>天池煤灰>灵新煤灰。此外,O_2/CO_2燃烧气氛中CO体积分数的增加会促进NO_2的还原,高体积分数的CO_2对NO_2的还原有明显的促进作用,而O_2体积分数的增加会在一定程度上抑制NO_2的还原。动力学分析结果表明,O_2/CO_2燃烧中局部高体积分数CO降低了NO_2还原的表观活化能,从而能够促进NO_2的还原。

The influences of reaction temperature, ash, minerals and reaction atmosphere on the NO2 reduction behavior were investigated in a fixed bed reaction system to explore the mechanism of NO2 reduction under O2/CO2 combustion condition. Experimental results indicate that NO2 reduction rate increases with reaction temperature. When the reaction temperature is above 873 K, NO2 decomposition is significantly accelerated, and the NO2 reduction rate reaches 90% at 1 073 K. The main minerals in coal ash have catalytic effects on NO2 reduction, and their catalytic activities on NO2 reduction are as follows： Fe2O3〉MgO〉CaO〉Al2O3〉Na2CO3〉 K2CO3〉 SiO2. Due to the high active mineral contents in Zhundong coal ash, the catalytic activities of the ashes are as follows： WCW ash〉TC ash〉LX ash. In addition, the increase of CO concentration in the reaction atmosphere can promote NO2 reduction, and high concentration of CO2 also has obvious catalysis on NO2 reduction. While the increase of O2 concentration shows an inhibition effect on NO2 reduction to a certain extent. Dynamic analysis indicates that CO can reduce the apparent activation energy of NO2 reduction and hence promote NO2 reduction.