| Yellow phosphorus industry is one of the pillar industries in Yunnan Province,and can produce a lot of yellow phosphorous tail gas per year.The off-gas of yellow phosphorus contains a large portion of CO(85%-95%).CO is a high quality material gas for Cl(one carbon)chemical industry.And off-gas of yellow phosphorus have a lot of impurities,includes H2S(800?1100 mg/Nm3),COS(700-1000 mg/Nm3)and CS2(20-80 mg/Nm3).They will not only pollute the environment,but also poison catalyst with Cl chemical industry,so in order to resource utilization of yellow phosphorus exhaust,the H2S,COS,CS2 must be removed.In recent years,biochar-supported catalysts have attracted wide attention.Biochar supports have many advantages,such as wide sources of raw materials,low production cost and large area extension.Meanwhile,as a catalyst carrier,biochar supports have large specific surface area,rich microporous pores and rich surface functional groups.Yunnan province is rich in tobacco stem biomass resources.The cheap tobacco stem can be used as the raw material to prepare the biochar carrier,so that the disposal problem of the tobacco stem can be solved,and the tobacco stem waste can be reused.Compared with the incineration and composting of tobacco stem,the preparation of biochar supported catalyst has higher resource recovery value.In this paper,the removal of H2S,COS and CS2 was studied based on the characteristics of yellow phosphorus tail gas.The effects of carbonization temperature,activator kind,activator content and activation temperature of chemical and physical activation methods on the removal of H2S,COS and CS2 were studied.The effects of metal species,metal loading,bimetallic loading,bimetallic loading,calcination temperatures and KOH contents on the removal of H2S,COS and CS2 were also investigated.Meanwhile,the effects of reaction temperatures,relative humidity,oxygen contents,space velocity and other factors on the simultaneous removal of H2S,COS,CS2 were researched,and the optimum process conditions were obtained.The main research results are as follow:(1)Screening and optimization of the preparation conditions of tobacco stem based biochar supported catalysts:The biochar supported catalysts were prepared with tobacco stem.The effects of carbonization temperatures,chemical activation methods and physical activation methods were investigated.It was found that the carbonization temperature of 700? was beneficial to the simultaneous removal of sulfur-containing gases.The low or too high carbonization temperature was not conducive to the formation of pore structure.The effects of activator,activator contents and activation temperatures of chemical activation method were investigated.The experimental results showed that when the activation temperature was 700?,mass ratio of KOH/biochar was 2,the catalysts had the best simultaneous removal effect.The research of physical activation method inclued the effects of activator.CO2 flow rate and activation temperatures.The experimental results showed that the biochar catalysts prepared with 40ml/(min g)of CO2 and 800? of activation temperature had higher removal efficiency of H2S,COS and CS2.CO2 could make the catalyst form more abundant oxygen-containing functional groups and more microporous structures;too low or too high CO2 flow was not conducive to the formation of microporous structures.too high CO2 flow will lead to microporous destruction.With the increase of activation temperature,more pores could be formed in the biochar,but it is not conducive to the formation of oxygen-containing functional groups.(2)Preparation condition optimization of tobacco stem-based biochar carrier catalysts:The catalyst support was tobacco stem-based biochar prepared by physical activation method.The effects of the first metal kind and contents,the second metal kind and contents,the calcination temperatures,KOH contents on the catalytic activity.The experimental results showed that the catalyst prepared with 10%CuO2 n(Cu):n(Fe)= 10:1 and impregnated with 5%KOH solution at 400? for 3 h had the best simultaneous removal efficiency of H2S,COS and CS2.CuO loading is not easy to produce sulfate on the catalyst surface because of its low metal activity,when the loading content was too low.the catalytic capacity was poor,and the high load would lead to CuO agglomeration and blocking the pores of biochar.Metal oxide Fe2O3 can played a role in the promotion of catalytic activity;lower calcination temperature would form oxygen radicals on the catalyst surface,and the oxygen radicals could react with H2S to lead to catalyst deactivation,but when the calcination temperature was too high,the pore structures of catalyst were destroyed.(3)Optimization of process conditions:The effect of process conditions on the catalytic activity of Cu-Fe/TSAC catalyst was investigated experimentally.The experimental results showed that the reaction temperature was 60?,the space velocity was 10000h-1,0.5%O2,the relative humidity is 49%,and the effect of H2S.COS and CS2 was the best.It was found that too high or too lower reaction temperatures are not conducive to the removal of the reaction.The lower reaction temperature is not conducive to the occurrence of the reaction,and the high reaction temperature will lead to the formation of sulfate on the catalyst surface,resulting in catalyst deactivation.(4)Experimental study on catalyst regeneration:The effects of calcination temperature and impregnated KOH content on the activity of regenerated catalyst were investigated experimentally.The experimental results showed that the catalyst regenerated with 5%KOH solution at 400? for 2 h had the best simultaneous removal efficiency of H2S;COS and CS2.The results showed that the calcination temperature is 300?,which is not conducive to the decomposition of sulfate on the catalyst.When the calcination temperature is 500?,the pore structure of the catalyst will be destroyed.Reactivation of KOH could restore the catalytic activity of the catalyst,less KOH could not achieve the purpose of recovering the catalyst activity,but too much KOH will occupy the active site of the catalyst. |
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