Technological Study And Environmental Risk Assessment Of Brick Making From Residue Of Oily Sludge Treatment

Oily sludge includes three types:ground sludge produced in the process of exploitation,dirty oil settled in the bottom of tank during transportation and storage,and sludge in the process of refinery sewage treatment.Its main ingredients are sandstone,limestone,clay,mineral oil and soluble salts,There are also have some malodorous gases such as sulphide,benzene,phenols and harmful heavy metals.At present,the biological treatment technology of oily sludge has not yet refined and the chemical treatment technology has low efficiency and high cost,so incineration is the best way to dispose of the sludge.But this method is too expensive for the enterprises,so there are hundreds of millions of tons of the oil sludge stacked at the refinery.It will do a very bad effect on the environment.Base on those problems,recovery of oily sludge is a hot topic in the petrochemical industry.After treated by"chemico-heating wash"process,the residue of oily sludge was identified as general industrial solid waste.This topic through analyzing the physicochemical characteristics of oily sludge residue,the oil content of the residue was less than 2%,the moisture content was 17.2²2.7%,the calorific value of organic matter was 364⁷85kJ/kg,and the content of Cu,Pb,Cr,Ni,Zn and Cd in the residue is far lower than the limit of"Sludge for sludge treatment and brick making in urban sewage treatment plant",the indicators have reached the national standard,which supply theory foundation for its feasibility as a brick admixture.In this paper,sludge residue and Q₃ loess were used as the main materials,and fly ash,coal powder and sintered brick additives were used as auxiliary materials.The sintered bricks were obtained by stirring,aging,pressing,drying and firing.From the performance parameter test results it is known that when the sludge residue content is>40%,a slight frost phenomenon will occur.When the sludge residue content is?60%,the brick blank is cracked,the dimensional deviation is within-2.0,the compressive strength of the brick body is<MU10,the average water absorption rate is>20%,and the quality of the sintered brick is obviously decreased.The orthogonal analysis method was designed to compare the effects of sludge residue content,molding pressure and firing temperature on the two main indexes of brick compressive strength and water absorption.It was found that the sludge residue content has mechanical properties on the sintered brick.The impact is significantly more significant than the other two factors.When the sludge residue ratio is S30,the mechanical properties of the brick body are qualified,which can be used for the laying of well sites and pedestrian roads.By analyzing the influence of different sintering process parameters on the mechanical properties of the brick found that under the same ratio,when the molding pressure increases,the compressive strength of the brick is strengthened,the water absorption rate is reduced,and the bulk density is not affected;when the firing temperature is increased,the water absorption rate decreases,the brick density increases,and the compressive strength tends to rise first and then decrease.Under the same firing conditions,the compressive strength and density of the brick body decrease with the increase of the amount of sludge residue,and the water absorption rate increases.Under the premise of ensuring that the compressive strength and water absorption of the brick body meet the standard,in order to follow the principle of sludge residue reduction treatment,the optimal process parameters are finally determined to be sludge residue content 30%,firing temperature 1050?,molding pressure 20MPa.The finished product has a compressive strength of 11.45 MPa and a water absorption of 17.71%.Under the premise that the performance index of the sintered brick is qualified,the adobe before the sintering and the two adobe samples after the sintering are subjected to the leaching test.Six kinds of leaching concentrations of Cu,Pb,Cr,Ni,Zn and Cd were measured after continuous leaching for 64 days in the extracting agent with pH=4.5.It was found that high temperature roasting has a good stable curing effect on heavy metals in oily sludge residue,which effectively reduce the amount of heavy metals released.It will not cause secondary pollution of the environment during use.The research results show that the residue treated with oily sludge can be used for the preparation of sintered bricks,which can not only process at low cost,but also eliminate sludge residue accumulated in the plant area,reducing the environmental burden of oil companies.During the sintering process,harmful substances such as heavy metals are fixed in the brick body,which effectively realizes the reduction,harmlessness and resource utilization of the sludge,and has good economic,environmental and social benefits.