Study On Purification Efficiency Of SO₂/NO_x/CO₂ In Flue Gas By Biological Spray Tower

With the rapid development of my country's economy,air pollution has become an environmental issue that our country attaches great importance to.SO₂,NO_x,CO₂ will cause a series of air problems such as smog,acid rain,greenhouse effect,etc.Therefore,the development of more economical and effective flue gas purification technology is imminent.The chemical absorption-biological reduction method has been widely concerned because of its advantages of high economy,good purification effect and less secondary pollution.In this project,a biological spray tower for laboratory was designed independently.The flue gas will be transferred from the gas phase to the liquid phase through contact with the biological liquid membrane,and then converted into harmless substances such as N2 and S0 through the enzymatic reaction of the biological membrane.In the first part of the experiment,the effects of the gas velocity of the empty tower,the p H of the spray liquid,the reflux ratio,and the liquid spray density on the flue gas purification efficiency were investigated and the optimal process operating parameters were determined.When enhancing the purification efficiency of CO₂ and NO,the feasibility of flue gas recirculation,the effect of SO₂/S2-on NO,and the promoting effect of the concentration of the Fe???EDTA on both were studied in the experiment.The type and concentration of liquid phase ions were monitored in the experiment.High-throughput sequencing of sludge samples at various stages was conducted to investigate the microbial flora composition and succession.The research results are as follows:the higher the gas velocity of the empty tower,the worse the purification efficiency of CO₂ and NO and the conversion rate of SO42-,S2-and NO₂-in the solution,and it has no effect on the purification efficiency of SO₂ and NO₂ within the test range.In the p H optimization test of spray liquid,the efficiency of flue gas purification and ions conversion is the best when the p H is set to 9.The higher the reflux ratio of the absorption liquid,the higher the ion conversion efficiency in the liquid phase,and the worse the purification efficiency of CO₂ and NO.In general,it is more appropriate to choose 1:4.The higher the liquid spray density,the better the flue gas purification efficiency and the higher the ion conversion efficiency,but the greater the impact on the biofilm.When the liquid spray density is 0.88 m3/?m2·h?,high purification efficiency can be obtained without biofilm falling off.In the research on NO enhancement,it is concluded that the flue gas reflux can effectively improve the purification efficiency of NO and CO₂ by more than 20%.The presence of SO₂ and S2-will have a negative impact on the purification of NO.When Fe???EDTA was added to the spray solution,the flue gas load and treatment efficiency were significantly improved.After adding up to 5mmol/L Fe???EDTA,the maximum treatment load reaches 3.8 L/min,and the purification efficiency can reach more than 95%.Fe???EDTA is gradually lost during the reaction,and the concentration of Fe2+ increases first and then decreases,indicating the presence of Fe3+ reduction.Illumina high-throughput sequencing of biofilm samples at different stages was performed.The samples were the original sludge N0,the domesticated sample S0,the optimized condition sample S1,At the end of the test with the addition of complexing agent,the upper?S2?and lower?S3?samples of the spray tower.The results show that with the addition of Fe???EDTA as the cut-off point,the richness and diversity of N0,S0,and S1 are better than those of S2 and S3.Comparing S2 and S3,it is found that the microbial diversity and richness of the upper layer of the spray tower are excellent on the lower level.The dominant categories in the five samples are Proteobacteria and Chloroflexl.After analyzing the genus composition,it was found that the main functional bacteria are desulfurizing bacteria: Sulfurovum,Desulfobulbus,Desulfococcus.Denitrifying bacteria: Sulfurovum,Thauera.COD degrading bacteria: Anaerovorax,Longilinea,Cloacibacillus,and iron reducing bacteria: Thermomovirga,Clostridium?sensu?stricto?1.After the addition of Fe???EDTA,Sulfurovum,Acidaminobacter,Clostridium?sensu?stricto?1 with iron reduction function,Thermovirga with anti-toxic and harmful substances such as antibiotics,dyes,heavy metals and other functions have increased significantly.The Longilinea is able to degrade complex organic matter but its abundance decreases after adding Fe???EDTA.In general,although the abundance and diversity of the bacterial community have decreased after the addition of Fe???EDTA,the abundance of dominant species has increased.It shows that iron ions have played a positive role in the system,promoted the growth of related functional bacteria,and eliminated the microorganisms with weak adaptability.