臭氧氧化烟气脱硝制硝酸的试验研究

将含NO的模拟烟气用臭氧氧化后进行洗气,在脱硝过程中制得硝酸.在100～160℃模拟烟气温度范围内,O3与NO3浓度是影响气液反应HNO3生成的重要因素.臭氧与NO的物质的量比(O3/NO)在1.5以上为宜.高的O3/NO物质的量比和低的模拟烟气温度,利于反应生成NO3和提供较高体积分数的O3进行气液反应,促进HNO3的生成,抑制亚硝酸的生成.试验中在模拟烟气温度120℃下,O3/NO物质的量比为1.5和2时,硝酸产率分别为70.5%和88%.随着在气相反应器中停留时间的延长,O3与NO3的浓度降低,HNO3产率下降,HNO2生成上升.吸收液的酸度对HNO3生成的影响并不明显,在pH值1.5～2.5时,硝酸的产率比pH值等于7时降低3%～4%.

Experimental Research on Production of Nitric Acid Using Ozone Denitration Flue Gas

Production of nitric acid during denitration was investigated after simulated flue gas containing NO underwent ozone treatment and scrubbing. Within the simulated flue gas temperature range of 100-160℃, O_3 and NO_3 are two major factors influencing the formation of nitric acid in a wet scrubber. Molar ratio of ozone to NO (O_3/NO) is recommended to be above 1.5. High O_3/NO and low simulated flue gas temperature will facilitate the formation of NO_3 and provide high volume fraction O_3 which can increase the yield of nitric acid and suppress the formation of nitrous acid in gas-liquid reaction. In this experiment, when O_3/NO is 1.5 and 2 and the simulated flue gas temperature is 120℃,the maximum yield of nitric acid is 70.5% and 88%, respectively. As retention time in the gas reactor gets longer, O_3 and NO_3 concentrations get lower, so does the yield of nitric acid, but the formation of nitrous acid is promoted. Acidity of wash solution doesn't affect the yield of nitric acid significantly. At pH 1.5-2.5, the yield of nitric acid is only 3%-4% lower than that at pH 7.