In-situ Catalytic Cracking Of Tar From Municipal Solid Waste Gasification Over Biochar-based Catalyst

Gasification technology provides broad prospects for the harmless and resourceful treatment of domestic waste,but it limits the extensive use of this technology due to the harmfulness of by-product tar.Therefore,selecting the appropriate tar removal method is the key to the efficient utilization of domestic waste.As one of the products of pyrolysis and gasification of biomass waste,biochar is a promising catalyst because of its low price,abundant pore structure and good catalytic performance.In this paper,the three-stage horizontal gasifier was used to carry out the in-situ catalytic cracking of tar from municipal solid waste gasification by carbon-based catalyst.The effects of equipment operating parameters and the type and concentration of carbon-supported catalyst on the cracking performance of the tar were investigated.In order to study the influence of operating parameters on the cracking of gasification tar,the in-situ non-catalytic cracking of tar from municipal solid waste gasification was studied.As one of the main factors affecting tar cracking,the reaction temperature is particularly prominent in the distribution of tar three-phase cracking products.As the reaction temperature increases,the proportion of carbon black solids in tar cracking products increases;carbon black acts as The useless by-products will stick to the inner wall of the equipment and it will be extremely difficult to remove,which will lead to equipment failure and potential risks.The introduction of water vapor solves this problem well.It is found that with the increase of water vapor injection concentration,tar The carbon black component in the cracked product is significantly reduced,and the proportion of the combustible gas component is increased.When the injected water vapor concentration is 6 vol.%in N₂,the tar cracking rate is optimal,at this time,it is 76.92%,further increasing the water vapor concentration,the tar cracking rate is slightly decreased;when the injected water vapor concentration is 12 vol.%in N₂,the yield of tar cracking gas was the highest at60.32 mol/kg.As the carrier of carbon-based catalyst,the activation performance of biochar determines the level of pyrolysis ability of carbon-based catalysts.As one of the important factors affecting the activity of biochar,carbon charcoal obtained at 500°C carbonization temperature is the most abundant and the specific surface area is the largest;with the further increase of temperature,the micropores decrease and the pores become larger.At 800?,small pores melt and merge into large pores.In order to further improve the activity of biochar,CO₂ gasification experiment was carried out.It was found by SEM image that the pore passage of biochar was more transparent after CO₂ gasification,and the organic matter originally blocked with micropores was removed by CO₂ gasification reaction.Further increasing the micropore specific surface area of biochar enriches the pore structure,while more alkaline earth metal?AAEM?migrates to the surface of biochar by CO₂ gasification.In addition,it was found that the FTIR detection showed that the diffraction peak of the oxygen-containing functional group on the surface of the biochar after CO₂gasification became stronger,that is,the concentration of the oxygen-containing functional group increased,and the surface of the carbon in the biochar tar catalytic cracking reaction The cleavage of polycyclic aromatic hydrocarbons?PAHs?,an important substance in oxy-functional tars,plays a pivotal role.The carbon-based catalyst supporting different loading concentrations of the same metal and supporting different metal elements was prepared by impregnation method with the best active biochar as carrier.Metal loading may reduce the pore structure and total specific surface area of the biochar surface,but at the same time magnify and increase the active site of the carbon surface.In the cleavage reaction of the carbon-based catalyst tar,the active site is used as the active site.Adsorption of the tar precursor?polyaromatic ring?acts to reduce the activation energy required for tar cracking.At the same time,it was found that Ni-Biochar tar cracking showed excellent performance,but the carbon deposition rate was as high as 28.9%,which was easily deactivated in the tar cracking reaction;the Fe element was loaded without reducing the catalytic performance of Ni-Biochar.Next,the carbon deposition resistance of the Ni-supporting carbon-based catalyst is improved.