In-Situ Catalytic Cracking Of Volatiles From Pyrolysis Of Coal By Modified Sewage Sludge Ash

Under the background of increasingly severe environmental problems and the introduction of a series of environmental protection policies,regulations and measures in my country,the clean and efficient utilization of coal has become a key issue to be developed urgently.Coal pyrolysis is one of the technological methods for efficient and clean utilization of coal resources.However,the tar produced by coal pyrolysis usually has a high content of heavy components,which will affect the quality of the tar and the added value of the product.Therefore,it is necessary to carry out catalytic cracking and upgrading of coal tar,so as to lighten it and generate more valuable gas.At the same time,the amount of urban sludge in my country is large,and the utilization rate of the residue after incineration treatment is low.Making it into a catalyst to achieve the purpose of waste recycling can not only reduce the cost of the catalyst,but also avoid its harm to the environment.In this paper,the catalyst was prepared by modifying the sludge by three methods:pickling,directly loading nickel oxide and loading nickel oxide after pickling.The catalytic cracking effect of the catalyst on the volatiles of Yulin coal tar was investigated in a fixed bed reactor.The research work can provide theoretical basis and technical support for the catalytic cracking of coal tar and the reuse of municipal sludge ash.In this paper,the effects of reaction temperature,weight hourly space velocity and catalyst calcination temperature on the catalytic cracking process of coal pyrolysis volatiles were first discussed,and the optimal process parameters were obtained.The results show that when the reaction temperature is 600°C,the mass space velocity is 1.5 h^-1 and the catalyst calcination temperature is 600°C,the catalytic cracking effect is better.The effect of catalyst modification with different acid solutions on the catalytic cracking effect of pyrolysis volatiles was further studied,and it was found that the specific surface area and acidity of the catalyst after pickling increased.Compared with the use of the original catalyst,the catalytic cracking process using1 mol/L acid-modified catalyst reduces the yield of tar and water,increases the content of light components in the tar,and increases the gas yield,among which the increase in H₂ yield is more obvious.This shows that the catalytic cracking effect of the catalyst is improved.When using5 mol/L hydrochloric acid to modify the catalyst,although the comparative area of the catalyst increases,the content of active components in the catalyst decreases,resulting in a decrease in the content of light tar components,and the catalytic cracking effect becomes poor.The effect of NiO loading on the distribution of pyrolysis volatiles catalytic cracking products was mainly investigated,and the performance of modified catalysts in coal pyrolysis volatiles catalytic cracking was analyzed by TG,XRD,NH₃-TPD,N₂ adsorption/desorption and other characterization methods.mechanism of action in the process.Compared with no catalyst,the tar yield decreased from 15.6 wt.%to 10.0 wt.%,but the light tar content increased from 58.0 wt.%to 87.5 wt.%,the gas volume increased from 86 ml/g to 323 ml/g.The performance of the catalyst was evaluated and analyzed,and it was found that the catalyst used for the first time had the best cracking effect;the tar yield in the second use was 12.3 wt.%,the light tar content was 76.0 wt.%,and the gas yield was Compared with the non-used catalyst,the tar yield was increased by 180%,and it still had good activity;the tar yield of the fourth use was 15.1 wt.%,the light tar content was 70.5 wt.%,and the gas yield was 15.1 wt.%compared with the non-used catalyst.an increase of 78%.The catalytic effect of the catalyst gradually decreased with the increase of the number of uses,which was mainly due to the decrease of the activity of the catalyst due to the accumulation of carbon on the surface of the catalyst.The used catalyst was calcined at 600°C for 3 h for regeneration,and the results showed that the product yield and distribution of the regenerated catalyst were close to those of the fresh catalyst,indicating that the regeneration performance of the catalyst was good.