Study On Preparation And Performance Of Pyrolysis Catalyst For Oily Sludge

Oily sludge is an oily soild waste generated during the process of oil extraction,transportation,refining and oily sewage treatment,and is one of the main pollutants in the petrochemical industry.Oily sludge contains oil,a small amount of mechanical impurities,solid particles of sand,chemicals,as well as a certain amount of benzenes,phenols and heavy metals.It has a complex composition and high stability.Because of the complex component and high stability,oily sludge was listed in the catalogue of national hazardous waste.The efficient treatment for oily sludge can recover crude oil,minimize impacts to environment and human health,and achieve the reduction,harmless and resources oily sludge treatment mainly includes thermal washing,extraction,biological treatment,pyrolysis treatment,etc.Among them,pyrolysis is one of the mainstream technologies for large-scale applications at present and improvement of oil recovery and reduction energy consumption are the keys of this technology.In this paper,oil-bearing sludge from an oil field in northern Shaanxi was the target.The weight loss process of sludge was investigated by thermogravimetric analysis.The TiO₂/bentonite-supported catalyst and activated clay modified catalyst was prepared.By analysing the effects of different conditions on the catalytic pyrolysis of oily sludge,determineing the composition of pyrolysis products and the technological parameters of catalytic pyrolysis treatment of oily sludge,technical support for the low temperature pyrolysis and catalytic treatment of oily sludge was provided.Through this research,mainly achieved the following results.The oily sludge weight loss process mainly involves three phase:the evaporation of water,the volatile precipitation of light components and the decomposition of heavy oil.Oil-containing sludge was pyrolyzed at 450?for 4 h without catalyst addition,nitrogen flow rate of 100 mL/min,and heating rate of 10?/min,and the maximum oil recovery was76.16%.The TiO₂/bentonite-supported catalyst and activated clay modified catalyst were prepared by sol-gel method and hydrochloric acid modification,respectively.The catalysts were characterized by SEM,EDS,FT-IR,XRD,and N₂-physical adsorption.The influence of catalyst on the pyrolysis process of oily sludge was discussed,and the effect was compared with that without catalyst.When the addition amount of TiO₂/bentonite-supported catalyst is1%,the pyrolysis time can be shortened by 1 hour,the pyrolysis temperature can be reduced by 30?,and the oil recovery rate can be increased by 9 percentage points to 85.65%compared with that without catalyst.When the amount of active catalyst is 1%,the pyrolysis time can be shortened by 0.5 h,the pyrolysis temperature can be reduced by 20?,and the oil recovery rate can reach 85.80%.Compared with conventional pyrolysis residues,the catalytic pyrolysis residue has a well-developed pore structure,which lays the foundation for the further preparation of catalysts and adsorbents;the oil content of the residues has dropped from 2.20%of conventional pyrolysis to about 1%,and the heating value has been decreased from 3176.55kJ/kg to 2134.67 kJ/kg;the content of recovered oil C₁₆^C₂₀0 increased from 30.31%to 36.40%by conventional pyrolysis,among which the content of colloid and asphaltene decreased from1.95%,9.73%to 1.04%and 0.05%,respectively.The content of saturated hydrocarbons increased by 12 percentage points.At the same time,the content of CH₄ produced by pyrolysis gradually decreased,while the content of CO₂ increased over time.