二氧化硫在氯化钙盐吸法应用中的反应特性

Reactive characteristics of sulfur dioxide in the application of calcium chloride absorption method

摘要:

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.

Abstract:

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.