Na_2S_2O_8溶液脱硝的热力学计算与试验研究

Thermodynamic analysis and experimental investigation about denitration by Na_2S_2O_8 solution

液相氧化脱硝技术被认为是最有前景的脱硝技术之一。在小型鼓泡反应器中,进行了Na_2S_2O_8溶液脱硝试验。热力学计算表明:无论酸性或碱性条件下,300~380 K时,脱硝反应均为放热反应,且反应的△G均远小于-40 k J·mol^(-1),反应平衡系数均非常大;同一温度时,碱性条件下反应平衡系数较酸性条件下大。选取吸收时间、Na_2S_2O_8浓度、初始p H值、反应温度、烟气流量和NO含量为过程参数,脱硝率为响应,进行了单因素试验。结果表明:脱硝率随Na_2S_2O_8浓度、温度的增加而升高,随吸收时间、烟气流量或NO含量的增加而降低,p H值在2~3和9~12,体系获得较好的脱硝效果。Na_2S_2O_8摩尔浓度为0.15 mol/L,初始p H值为10,温度为70℃,烟气流量为0.5 L/min的条件下,处理NO体积分数为0.03%~0.08%的烟气,20 min内体系脱硝率均在80%以上。

Liquid-phase oxidation denitrification technology is one of the most perspective technologies. This work carried out the denitrification experiments by Na_2S_2O_8 solution in minitype bubbling reactor. Thermodynamic analysis showed that no matter on the acidic or alkaline condition,at 300-380 K,the denitrification reaction is exothermic reaction,the Gibbs free energy change is far less than-40 k J·mol^(-1),the equilibrium coefficient are all very big,and it's bigger on the alkaline condition than the acidicones. Reaction time,Na_2S_2O_8 concentration,initial p H value,temperature and gas flux were selected as the process parameters,denitrification rate as the response,carried out the single-factor experiments. Experimental results demonstrated that denitrification rate rose while the Na_2S_2O_8 concentration or temperature increased,and decreased while the reaction time,gas flux or NO concentration increased,during the p H value 2-3 and 9-12,better effect was achieved. On the condition of Na_2S_2O_8 concentration 0. 15 mol/L,initial p H value 10,temperature 70 ℃ and gas flux 0. 5 L/min,disposed the gas of which NO concentration is between 0. 03% and 0. 08%,within 20 min the denitrification rate were all above 80%.