Experimental Research On Treatment Of Oil Sludge Based On Solidification-pyrolysis Technology

Oily sludge is a kind of hazardous solid waste produced in the process of petroleum exploitation,transportation,processing and utilization.It contains rich oil resources and various toxic and harmful substances such as anthracene,phenanthrene,and pyrene.It has been included in the?National Hazardous Waste List?by the State Environmental Protection Administration.If it is not treated,it will not only cause a waste of oil resources,but also cause serious harm to the ecosystem,animals,plants,and humans.Therefore,rational treatment of oily sludge is of great significance.Pyrolysis technology has been widely studied because it can efficiently recover oil products without causing secondary pollution.However,the current pyrolysis process tends to cause the sludge to form solid masses when processing viscous sludge,then causing equipment blockage and affecting the equipment operation cycle.In view of the characteristics of oily sludge and the shortcomings of the current pyrolysis process,the author's laboratory designed a set of full-circulation fixed-size moving bed pyrolysis sludge equipment by referring to the mature oil shale fixed-bed dry distillation process.On this basis,this article proposed a solidification-pyrolysis combined process route to treat sludge,which provided theoretical data for the application of new equipment.At the same time,it solved the problems of sticky sludge clogging equipment and incomplete treatment.The oil was recovered while removing harmful substances,so as to truly realized the harmless and resourceful treatment of oily sludge.This paper firstly determined the basic properties of oily sludge,and the results showed that oily sludge contained 29.67%oil and 64.10%solid minerals(mainly involved iron and iron oxide minerals),which had potential utilization value.The results of thermogravimetric analysis showed that the pyrolysis process of oily sludge could be divided into three stages:drying and desorption,volatilization of light oil and cracking of heavy oil,and oxidation-reduction reaction between iron oxides and coke.Secondly,this paper prepared oily sludge solidified block with oily sludge as raw materials,cement and oil shale semi-coke as curing agents,combined with the laboratory's self-made liquid binder.Through the establishment of orthogonal experiments and single-factor analysis experiments,the effects of composite curing agent content,composite curing agent ratio,hydraulic binder content,and curing age on the compressive strength of oily sludge solidified blocks were investigated.The results showed that when cement:oil shale was 3:2,composite curing agent:oily sludge was 3:2,and the liquid binder content was 15%,the strength of the cured block with a curing age of 7 d reached the best.Under the optimal process conditions,the cold strength of the solidified block was2.38 MPa,the thermal strength was 2.41 MPa,the drop strength was98.78%,and the thermal stability(TS₊₁₃)was 97.15%.The main pyrolysis stages of the oil sludge and solidified block were studied by Coat-Redfern variant.The results showed that the pyrolysis process of the oily sludge and the solidified block followed the three-dimensional diffusion model,and the average activation energy was67.79 k J/mol and 71.35 k J/mol respectively in the volatilization stage of light oil;and in the cracking stage of heavy oil,the pyrolysis processes were in line with the three-level chemical sequential reaction model,and the average activation energy was 123.73 k J/mol and 131.86 k J/mol,respectively.The pyrolysis process of solidified blocks of oily sludge was studied on the aluminum retort dry distillation device,the best dry distillation conditions were determined,and the resources and harmlessness of dry distillation products(oil,non-condensable gas,semi-coke)were evaluated.The results showed that when the heating rate was 10?C/min,the final pyrolysis temperature was 530?C,and the holding time was 30 min,the oil yield was the highest,and the oil can be used as fuel after desulfurization and viscosity reduction.The main components of non-condensable gas were H₂,CO,CO₂ and hydrocarbon gas.The content of methane,ethane,ethylene and other components in the hydrocarbon gas was high,and the heating value was high,so it can be used as fuel gas.Dry distillation semi-coke can be used as garden and pasture soil.Because the mineral oil content was less than 3000 mg/kg,the polycyclic aromatic hydrocarbons(PAHs)content was less than 6 mg/kg,and the heavy metal content and other indicators all met the?Agricultural Sludge Pollutant Control Standards?.