Study On Urea With Different Additives To Improve Simultaneous Desulfurization And Denitrification Efficiency

In recent years, air pollution problem is becoming more and more serious, SO₂ and NO_x emissions from fossil fuel combustion is a major pollutant, and therefore the requirements of SO₂ and NO_x emissions become more stringent. Wet flue gas desulfurization and denitrification is a promising method for desulfurization and denitrification, which has simple process, the low investment costs, no secondary pollution, simultaneous removal of SO₂ and NO_x and many other advantages.In this paper, a glass absorber column of 78 mm diameter and 1m height is used to do experimental studies. The absorber is full of corrugated structured packing. First, the feasibility of urea absorption reaction thermodynamics is calculated. The results showed that: SO₂ and NO removal ratio is near 100% at ambient temperature and pressure Theoretically. By adding different types of additives in the urea solution to test SO₂ and NO removal ratio, and eventually LAO-30 is selected as additive for further experimental studies. Eventually, the performance of single denitrification and simultaneous desulfurization and denitrification is investigated in urea/LAO-30 solution. The process parameter, such as gas velocity、absorbing liquid temperature、pH value、liquid-gas ratio、urea concentration、LAO-30 concentration,on the removal efficiencies of SO₂ and NO were studied. The SO₂ removal efficiency can always reach above 98.5%,different process parameter has different effects on removal efficiency of NO. The optimal conditions were: gas velocity is 0.1m/s, the liquid-gas ratio is 10L/m3, pH value is 7, the absorption liquid temperature is 20℃ the urea content is 3%, the LAO-30 is 0.04%. Under the optimal condition, SO₂ removal efficiency can reach 99.3%, NO removal efficiency can reach 76.8%.Analyze urea concentration and ion concentration of the reaction product. The results showed that ammonium, nitrate and sulfate are the main reaction products. The urea consumption rate curve and the ammonium ion formation rate curve showed a linear characteristic, indicating that urea / LAO-30 simultaneous desulfurization and denitrification reaction is zero order reaction. Adding LAO-30 to solution can accelerate the rate of urea consumption and ammonium ions formation to some extent.