Research On The Mercury Removal Performance And Regeneration Performance Of Multimetal Oxides

Mercury emission during coal utilization is one of the main sources of mercury pollution in the environment.During the process of coal pyrolysis and gasification,the mercury in the coal will be released and volatilized in the form of gas or compound,and will eventually exist in the high-temperature gasification gas.Under high temperature and strong reducing gas components,the catalytic oxidation process of mercury becomes difficult,while the use of mercury removal adsorbents has problems such as low efficiency,narrow temperature window,narrow application range,and poor regeneration performance.Considering that multimetal oxides,especially transition metal oxides,have the characteristics of environmental friendliness,low cost,and high oxygen carrying capacity,they are suitable for preparing renewable high-temperature and high-efficiency mercury removal adsorbents.In this topic,CeO_x with strong oxygen storage capacity,FeO_x with high Claus reaction activity,CoO_x and MnO_x with high oxidation capacity are selected as the research objects,combined with TiO₂ with developed pore structure as the basic carrier material,FeMnCe/TiO₂ is prepared by impregnation,CoMnCe/TiO₂,FeCoMnCe/TiO₂multimetal oxide adsorbent materials.Through the fixed bed mercury removal adsorption and regeneration desorption reaction experimental system,the analysis and study of the mercury removal performance and regeneration performance of the multimetal oxide adsorbent were carried out,and the mercury removal mechanism was discussed in combination with the characterization methods of BET,XRD and XPS.The mercury removal experiment with pure N₂ in a fixed bed reactor showed that when the loading rate of Fe atoms in FeMnCe/TiO₂ was 2%,the loading rate of Co and Mn atoms in CoMnCe/TiO₂ was 5%,and the loading rate of Fe atoms in FeCoMnCe/TiO₂ was 1%,the physical and chemical properties and surface morphology of the adsorbent reached the best state,and the best mercury removal efficiency of 93.2%,86.4%,and 85.4%could be achieved respectively.Meanwhile,the mercury removal experiments of three gas components of pure N₂,N₂+H₂S and coal gas have verified that the mercury removal efficiency of FeMnCe/TiO₂,CoMnCe/TiO_2,FeCoMnCe/TiO₂ multimetal oxides under the pure N₂ component has little difference with temperature.And the average mercury removal efficiency can be kept above 70%in the range of 80-200?.Under the N₂+H₂S composition,the mercury removal efficiency of CoMnCe/TiO₂ and FeCoMnCe/TiO₂ in the high temperature range is significantly better than that of FeMnCe/TiO₂,indicating that the sulfur resistance of the multimetal oxide adsorbent material in the high temperature range is significantly improved after the addition of CoO_x.Under the gas composition,FeCoMnCe/TiO₂ can reach 85.7%mercury removal efficiency at 160?,which is better than other tested materials and can exert the best synergy.The average mercury removal efficiency of FeMnCe/TiO₂,CoMnCe/TiO₂,FeCoMnCe/TiO₂ multimetal oxide mercury removal adsorbent material under N₂ component within 8 hours is 87.5%,76.4%and 86.8%respectively.It can be used for a long time and has better performance with high mercury removal ability.Through 5 regeneration cycle mercury removal performance test experiments,the average mercury removal efficiency of FeMnCe/TiO₂measured in pure N₂,N₂+H₂S can reach 76.2%and 81.5%,respectively,and FeCoMnCe/TiO₂ is measured in gas composition.The average mercury removal efficiency can reach 79%.The main reason for the reduction of mercury removal efficiency after adsorbent regeneration is the loss of some active components and the formation of sulfate and sulfite which block the pore structure.After multiple regeneration cycles,FeMnCe/TiO₂,CoMnCe/TiO₂,FeCoMnCe/TiO₂,as the number of regeneration cycles increases,the mercury removal efficiency is gradually stable and tends to be flat.The results show that the studied multi-metal oxide adsorbent has good mercury removal performance after multiple regeneration cycles,and has excellent thermal regeneration performance,which lays a solid foundation for engineering applications.