Study On Metabolic Activity Enhancement And Sulfur Production Of SRB In Flue Gas Biochemical Desulfurization

The emission of sulfur dioxide will do harm to the ecological environment and human health,and a large amount of sulfur-containing flue gas will be produced in the process of coal-fired power generation and metallurgical manufacturing.The traditional calcium desulfurization leads to the problem of a large number of desulfurization gypsum stacking,and the ammonia desulfurization has some problems such as high operating cost and ammonia escape.Sulfur is an important raw material needed in industrial and agricultural production,and a large amount of sulfur in China depends on imports;Solving the conflict between sulfur emission and sulfur import is an effective measure to build a resource-saving society.The biochemical treatment of sulfur-containing flue gas based on Sulfate Reducing Bacteria（SRB）can achieve normal temperature and pressure,no secondary pollution,and sulfur can be recovered,which has great potential in sulfur-containing flue gas treatment.This study aims at the problems of low SRB metabolic activity and low sulfur yield in biochemical flue gas desulfurization.In the process of biochemical flue gas desulfurization,the accumulation of S ₂O₃^2-will occur.This study explored the influence of electron donors on the metabolic activity of SRB.The effects of carbon-sulfur ratio,metabolic substrate concentration,influent p H and carrier materials forming biofilm on the metabolic activity of SRB were investigated.Sulfur,the pro duct of neutralization reaction,is the key step to realize the treatment of sulfur-containing flue gas and the recovery of sulfur as a resource.The regulation of neutralization reaction and the utilization of reaction product components are further studi ed.The main conclusions of this study are as follows:（1）Using sodium formate as electron donor can improve the metabolic activity of SRB.The mixed and pure strains of SRB were inoculated,and sucrose,glucose,sodium lactate,sodium acetate,sodium for mate and sodium bicarbonate were used as electron donors to explore the activity of S ₂O₃^2-metabolism.Pure strains have high metabolic rate when using sodium formate as electron donor,but mixed strains have strong tolerance;When sodium formate is used as an electron donor,the relative abundance of Vibrio desulfurization in microbial community is 7.8%,but its metabolic rate can reach 95.79%and sulfur conversion rate can reach 66.41%.Sodium formate as an electron donor can effectively improve the metab olic activity and sulfur conversion rate of SRB.When sodium lactate was used as an electron donor,the relative abundance of Vibrio desulphuriscus increased significantly,reaching 25.13%,which could be used as a good electron donor for SRB growth.When sodium acetate is used as an electron donor,the relative abundance of Vibrio desulphuriscus in microbial community is 4.5%,and its metabolic effect is poor.Sodium acetate will inhibit the growth and metabolism of SRB.The rate-limiting step in the process of using electron donors in SRB is the utilization and decomposition of sodium acetate.Choosing a suitable electron donor（such as sodium formate）to avoid the production of sodium acetate can effectively improve the metabolic activity of SRB and the utilization rate of electron donors.（2）When sodium formate is used as an electron donor to metabolize S ₂O₃^2-,when the carbon-sulfur ratio is 1,it can completely provide the electron donor needed in the process of SRB metabolism,and SRB has good metabol ic activity,which can maintain a high metabolic rate and sulfur conversion rate and obtain more suitable economic conditions;The higher the concentration of influent S₂O₃^2-,the higher the metabolic rate can be obtained,but the inhibitory effect on SRB activity is gradually enhanced with the increase of influent S₂O₃^2-concentration.PH has a great influence on SRB activity.When influent p H=4,SRB activity is completely inhibited,which leads to the failure of SRB metabolism and the collapse of the reac tion system.When influent p H=5,SRB activity is inhibited,but it can still undergo metabolic reaction and produce alkalinity to slowly increase p H.When p H is close to7,SRB activity is the highest.The biological matrix carrier has good biological affinity,good microbial diversity and high metabolic activity,and the polymer organic carrier has high mechanical strength,and the formed biofilm has strong specificity and high sulfur conversion rate.（3）Reducing the p H value of S^2-solution can significantly improve the sulfur yield and purity.Using liquid Claus method,S^2-reacts with SO₃^2-,and the main product is S0,and the by-product is S₂O₃^2-.XRD analysis shows that the solid phase product is S8 cyclic molecule and orthorhombic elemental sulfur.When the p H=5 value of S^2-solution is 5,the effect of sulfur production by neutralization reaction is better,and when the molar mass ratio of S^2-to SO₃^2-is 1.44,the yield of elemental sulfur is the highest,which is87.89%,and the particle size of sulfur is larger and the purity is higher.With the addition of S^2-solution to the flue gas washing water,sulfur neutralization and disproportionation reaction cause the generation and consumption of sulfur.The generation of elemental sulfur is m ainly contributed by the redox neutralization reaction of S^2-and SO₃^2-,while the consumption of elemental sulfur is mainly caused by disproportionation reaction.It is necessary to reduce the disproportionation of elemental sulfur during the reaction to obtain higher sulfur yield.The conclusion of this study can provide guidance for the selection of electron donors in the practical application of SRB desulfurization,and on this basis,choose appropriate electron donors to achieve the purpose of treating waste with waste;It can improve the yield and purity of sulfur and lay a theoretical foundation for the industrial application of sulfur resource in flue gas biochemical treatment.