Experimental Study And Process Validation Of Low Temperature Flue Gas Denitrification Oxidation Inhibitor

The proportion of NOx emissions from industrial kilns in the non-electric industry is increasing and has become an important source of air pollution.In view of the characteristics of low temperature,complex components and large NOx emissions from industrial kilns,the traditional denitrification methods are no longer applicable to the increasingly stringent environmental standards.In this study,based on the existing wet flue gas denitrification technology,the screening of different sulfite absorbers and oxidation inhibitors and the optimization of process parameters were carried out,and the feasibility was verified by building a pilot plant to provide theoretical support and technical basis for the practical application of the wet denitrification process.The main conclusions are as follows:Firstly,the performance of wet denitrification was studied with NO₂as the main component of NOx,and the denitrification effect of different kinds of sulfite was compared,and the influence law of different process parameters such as Na₂SO₃concentration,initial p H of solution,SO₂component and oxygen content on denitrification efficiency was investigated.The results showed that Na₂SO₃had the best denitrification efficiency and absorption capacity;when the concentration of Na₂SO₃was in the range of 0.002～0.008 mol/L,the denitrification efficiency increased from 50.71%to 91.46%with obvious changes,and the effect of continuing to increase the concentration on denitrification efficiency was not significant;when the p H value was in the range of 3～8,the denitrification efficiency increased from 45.82%to 90.02%The alkaline conditions were more favorable to the absorption of NO₂by Na₂SO₃;the introduction of SO₂and NO components had less effect on denitrification efficiency;when 3.5%O₂was introduced,the denitrification efficiency decayed rapidly from 93.84%to about 40%from the 5th minute,and the larger the oxygen content,the faster the decay,and the denitrification products NO₂^-/NO₃^-showed a decreasing trend.Secondly,the oxidation inhibitors such as Na₂S₂O₃,TEA,HQ and VC-Na were selected to study the promotion effect of denitrification,and the influence law of different process parameters on the denitrification of Na₂SO₃/VC-Na absorption solution and the mechanism of VC-Na oxidation inhibition were investigated,and the optimal process conditions were obtained by using RSM method.The results show that:VC-Na has the best oxidation inhibition performance,the efficient absorption time is extended from 18min to 70 min,and the total nitrogen-containing ion concentration rises from 65.52 mg/L to 126.079 mg/L;the average absorption efficiency is stabilized at 71%when the oxygen content is greater than 6.5%;VC-Na has stronger oxidation inhibition activity under alkaline conditions;the accumulation of NO₂^-ions will be detrimental to denitrification The denitrification efficiency decreased to 77.5%when 3.2 mol/L NO₂^-was added;VC-Na can compete with SO₃^2-to consume dissolved oxygen,thus protecting SO₃^2-from oxidation,and VC-Na can also react directly with NO₂;the best process conditions were obtained by RSM method:initial p H was 8.478,oxygen content was 0%,VC-Na concentration was 0.85 mmol/L,the actual denitrification efficiency is 94.58%,and the error rate with the predicted value is only 0.583%.Finally,a pilot plant for wet denitrification was built based on an industrial kiln of a chemical company,and the results showed that:the increase of O₃/NO molar ratio and spray volume as well as the addition of oxidation inhibitor could improve the denitrification performance of Na₂SO₃,and under the process parameters of O₃/NO molar ratio of 2.28 and spray volume of 12.8 m³/h,the denitrification efficiency could be higher than 90%.The denitrification efficiency was higher than 90%.