二氧化硫在氯化钙盐吸法应用中的反应特性

为探索氯化钙盐吸条件下SO2可能的转化反应以及该类反应对氯化钙盐吸法测量烟气中SO3的影响特性, 采用一维立卧管式炉实验装置及控制变量法研究了水蒸气、氧气氛、温度、反应物浓度对SO2与CaCl2化学反应的影响, 并理论分析了SO2与CaCl2可能的化学反应过程及对SO3测量的影响.结果表明：在无CaCl2样品条件下, SO2并不能发生均相反应; 在典型氯化钙盐吸法条件下, 只有当H2O及O2同时存在时, SO2可与CaCl2发生明显化学反应; 升高立卧管式炉温度及增加反应物浓度, SO2的转化率相应升高, 转化率约在2 %~8 %; 理论分析表明，该反应在200 ℃及典型取样气氛下属于慢化学反应, 在高浓度硫酸蒸汽存在下被严重抑制, 减小了对SO3测量的干扰, 一定程度上证明了氯化钙盐吸法测量SO3的可行性.
The main objectives are to explore the possible SO2 conversion reactions under the condition of calcium chloride absorption method (CCAM) and the effects of these reactions on SO3 measurement by the CCAM. The vertical-horizontal tube furnace and variable-controlling approach were used to study the influences of water vapor, oxygen atmosphere, temperature, reactant concentration on the chemical reaction between SO2 and CaCl2. On this basis, the possible chemical reaction mechanisms of SO2 and CaCl2 and the effects on SO3 measurement were analyzed theoretically. The results showed that SO2 could not undergo the homogeneous reactions in the absence of CaCl2. Under typical conditions of CCAM, only when H2O and O2 existed simultaneously, an obvious chemical reaction between SO2and CaCl2could occur. The conversion rate of SO2 can be improved with the increase of temperature and reactant concentration and the conversion rate is 2% to 8% approximately. Finally, the theoretical analysis demonstrated that the heterogeneous reaction was extremely week at 200 ℃and under typical sampling atmosphere, and this reaction was severely inhibited in the presence of high concentration of gaseous H2SO4. Therefore, the effect of SO2 interference on SO3 measurement could be ignored, which proved the feasibility of the CCAM to some extent.