Study On Collaborative Treatment Of Sintering Flue Gas Pollutants With Activated Semi-cokes

With the increase of crude steel output in China,the air pollution in steel industry becomes more and more serious.Sintering flue gas is the main source of air pollutant emissions of iron and steel enterprises,accounting for more than 50%of the total emissions of the entire iron and steel enterprises.The composition of sintering flue gas is complex,and the main components are SO2 and NOx?of which NO accounts for 90%?.If it is discharged into the atmosphere without treatment,it will easily cause irreversible damage to plants,animals,human body and the natural environment.Therefore,the control of the emissions of SO2 and NO in sintering flue gas has become the key work of the control of pollution in iron and steel enterprises.In numerous flue gas desulfurization and denitration technology,activated semi-cokes?ASC?is an excellent adsorbent and carrier material,which can simultaneously remove SO2 and NO and other pollutants in flue gas,and the resources can be recycled,high impact and abrasion resistance,no secondary pollution and low cost,accord with the requirement of economical society and circular economy,become the development trend of flue gas purification technology.Based on this,modified ASC to improve its desulfurization and denitration activity,it can turn waste into treasure,expand its new approach to resource utilization,and meet the conservation-oriented society and circular economy,which is of practical significance for energy saving and emission reduction.In this paper,the preparation,loading,characterization of ASC and its synergistic desulfurization and denitration performance as a catalyst were studied.The raw semi-cokes were activated by nitric acid,and its composition,specific surface area and microstructure were discussed.In order to improve the desulfurization and denitration performance of ASC,the ASC was used as the carrier to prepare ZnO/ASC desulfurizer by electrochemical deposition method,Fe2O3/ASC desulfurization and denitration catalyst by hydrothermal method and TiO2/ASC denitration catalyst by solvothermal method,respectively.The samples were characterized by BET,SEM-EDS,XRD,TEM,FT-IR and XPS.The desulfurization and denitration properties of ASC after loading the oxides were evaluated in a self-made fixed bed reactor.The mechanism of desulfurization and denitration of the supported ASC was discussed and the intrinsic kinetic equation was established.The results showed that after nitric acid activation,the ash content of semi-coke decreased and the specific surface area increased.With the increase of nitric acid concentration,the change was more and more obvious.When the concentration of nitric acid is 55%,the ash content was reduced to 4.99%,the deashing rate was 53.1%,and the specific surface area was up to 297.728 m²·g^-1,which is 5.5 times of the raw material.This provides good conditions for the next step of loading metal oxides on the ASC.The metal oxide supported on the surface of ASC has high crystallinity and no other phase is formed.The morphology and loading of metal oxides are affected by the preparation conditions,which will affect the desulfurization and denitration performance.By changing the experimental conditions,the optimal preparation conditions of each supported ASC were determined,and the active components were highly dispersed on the ASC carrier,so as to improve the activity of desulfurizer and denitrifier and obtain the ideal surface structure.The desulfurization and denitration properties of ASC after loading the oxide were evaluated in a self-made fixed bed reactor.The results show that when the electrolysis time was 30 min,the temperature was 65?,and the voltage was-3 V,ZnO was uniformly dispersed on the ASC surface in the shape of a flower.The diameter of the flower was about2³?m,which was composed of a number of ZnO single crystal rods with a diameter of about 300 nm.At this time,the desulfurization performance was the best,and the penetration time was 120 min.When the loading was 2%,the hydrothermal temperature was 180?,and the urea addition amount was R=5,Fe2O3 was a circular particle with a diameter of about100 nm uniformly supported on the surface of the ASC.Under this condition,Fe2O3/ASC had the best desulfurization and denitration performance,the breakthrough time of SO2 was140 min,and the breakthrough time of NO was 210 min.When the loading was 36%,the calcination temperature was 600?,and the urea addition amount was R=0.4,TiO₂ was a circular particle with a particle size of about 100 nm.At this time,the denitration performance was the best,and the breakthrough time was 345 min.Fe2O3/ASC had the best desulfurization performance and TiO2/ASC had the best desulfurization performance.The formation mechanism of the supported ASC and the mechanism of desulfurization and denitration of the supported ASC were discussed.The effects of O2 content,H2O content and reaction temperature on the performance of the supported ASC desulfurization and denitration were investigated.The intrinsic kinetic equation of desulfurization and denitration of the ASC was established,and the limiting link of the kinetics was revealed.In the simultaneous desulfurization and denitration experiments,combining the characteristics of each supported ASC,the fractional reaction was used to reduce the inhibition of NO adsorption by SO2 when SO2 and NO coexist,and the denitration activity during simultaneous desulfurization and denitration was improved.Considering the process flow and operating cost as well as the desulfurization efficiency,Fe2O3/ASC combined desulfurization and denitration is the best choice.