Study On Desulfurization And Denitrification By Ozone Oxidation Combined With Alkali Absorption

In order to achieve efficient desulfurization and denitrification of industrial flue gas,this paper adopts an ozone oxidation-alkali absorption process,and uses chemical simulation software Aspen Plus to simulate and analyze the process.Firstly,it has been known from previous studies that the ozone oxidation process is suitable for lower temperature.The conclusion is verified by the chemical reaction equilibrium theory in this paper.The results show that the ozone oxidation process is suitable for lower temperatures below 150℃.Secondly,for the O₃ oxidation-Na OH absorption process,the effects of factors such as flue gas temperature,residence time,O₃/NO molar ratio,and initial concentration of NO on the oxidation process were studied,by using the plug flow reactor and the exponential function as the oxidation model.It is found that O₃ has a high selectivity for NO.The temperature has little effect on oxidation rate of NO.The residence time and the initial concentration of NO have certain effects,and the O₃/NO molar ratio has the biggest impact.Meanwhile,the effect of factors such as the temperature,the NO concentration,the NO₂/NO molar ratio of flue gas at the inlet of the absorption tower and the amount of absorption liquid on the absorption rate of SO₂ and NO_x were studied.The results show that SO_x can be fully absorbed and the above factors have little effect on the absorption rate of SO₂,and the flue gas temperature has certain effect on the NO_x absorption rate,but the NO concentration,NO₂/NO molar ratio and the amount of absorption liquid has a significant effect on the NO_x absorption rate.Thirdly,for the Na OH-Na₂S₂O₃ absorption process,the effects of Na₂S₂O₃concentration,SO₂ concentration and p H on SO₂ and NO_x absorption rates were discussed.It was found that the increase of the above three factors can promote the absorption of NO_x,because in an alkaline solution,S₂O₃^2-can exist stably and have reducibility,so that it can jointly reduce NO₂ combined with the reducibility of SO₃^2-.Under the conditions of Na₂S₂O₃ mass fraction of 10%,SO₂ concentration of 300 mg/m³ and p H of 10,the NO_xabsorption rate can reach 83.32%.Finally,three different sulfate additives were added to the Ca SO₃ desulfurization process respectively.The promoting effects of different additives on NO₂ absorption at different concentrations were compared.The mechanism of the additive action was discussed,and the specific path of the SO₄^2-action was analyzed.Reducing additives such as Fe SO₄ are not suitable for removing NO_x,because its ferrous iron will consume NO₃^-,which will lead to disproportionation reaction of NO₂ and produce more NO.When the additive concentration is 0.35 mol/L,the NO_x absorption rate of Ca SO₃ desulfurization process with（NH₄）₂SO₄,Mg SO₄ and Fe SO₄ as additives can reach 68.38%,70.35%and65.98%.It can be seen that the ozone oxidation-alkali solution absorption process can realize high-efficiency oxidation of NO,and can achieve the removal of NO_x while efficiently removing SO_x.