基于氧化度调控的尿素还原脱除高浓度NO_x

Removal of High Concentration NO_x by Absorption with Urea and Adjustment of the Oxidization Degree

针对催化剂生产行业广泛存在的高浓度(100 000 mg/m3以上)NOx烟气,设计了利用O2氧化部分NO得到NO2来调节氧化度(NO2与NOx的体积比),再以尿素溶液为吸收液还原吸收NOx的脱硝工艺。通过控制O2和NOx在3级氧化罐中的停留时间,调节氧化罐中的氧化度,再将氧化罐中的NOx分级通入吸收塔,以调节吸收塔内NOx的氧化度;确定了NO氧化反应温度,考察了停留时间、尿素含量、尿素溶液与烟气的用量比(液气比)等因素对脱硝效果的影响。实验结果表明,在烟气量24 m3/h、氧化反应温度20℃、烟气在第一级氧化罐内的停留时间150 s及在第二、三级氧化罐内的停留时间均为240 s、以10%(w)的尿素溶液为吸收液、液气比为3.5 L/m3的条件下,脱硝效效率果最佳,NOx的总脱硝效率可达99.89%。

Aimed at high concentration NOx fume（more than 100 000 mg/m^3） in the catalyst industry, a denitration technology was developed, in which NO was oxidized into NO2 to adjust the oxidation degree（volume ratio of NO2 to NOx） of the fume and then the fume was denitrated by reduction absorption with urea. The oxidation degrees of NOx in three oxidizing tanks were adjusted by controlling the residence time of O2 and NOx mixed gas, and then the oxidation degree of NOx in absorption column was adjusted by introducing the fume from the oxidizing tanks into different sections of the absorption column respectively. The oxidation temperature was determined. The influences of the residence time, urea concentration and ratio of urea solution to fume （liquid-gas ratio） on the denitration were investigated. The experiment results showed that, the NOx removal efficiency reached 99.89% under the optimal conditions of fume flowrate 24 m^3/h, oxidizing temperature 20 ℃, residence time of fume in the first stage oxidizing tank 150 s, residence time of fume in the second and third stage oxidizing tanks 240 s, liquid-gas ratio 3.5 L/m^3 and urea solution concentration 10%（w）.