Study On Treatment Technology Of Oily Sludge From Sewage Treatment Plant In Refinery

Oily sludge has become one of the difficult problems in petroleum and petrochemical enterprises because of its wide source,complex composition,great harm to the environment and difficult resource utilization.There are different limitations in treating oily sludge directly by traditional physical,chemical and biological methods.As an environment-friendly treatment technology,electrochemistry has become a hot topic in recent years because of its high oxidation efficiency and no secondary pollution.Firstly,the purpose of recovery of oil phase and reduction of oil content of the sample were achieved by pretreatment experiment in the thesis,which takes oily sludge of a refinery as the research object.Then,the further advanced treatment of oily sludge in refinery was studied by electrochemical oxidation technique.The main research contents include:(1)The characteristics of oily sludge are analyzed to determine its physical and chemical properties and composition structure.(2)To explore the removal of oil content by p H value adjustment,hot water washing and ultrasonic pretreatment,and to determine the optimal pretreatment scheme by orthogonal test.(3)The pretreatment of oily sludge which is carried out by electrochemical oxidation,and the removal effect investigated under different experimental conditions.(4)Comparison and analysis of the changes of oily sludge properties before and after treatment,including organic matter,inorganic matter and dissolved pollutants in aqueous phase.The results show that:(1)The oil content of oily sludge is 1.69%,the solid content is 5.74%,the moisture content is 92.57%,the viscosity is 43.60 m Pa·s,p H value is 8.53,the oil content of lower sludge is 28.75%,the oil content of lower sludge is 92.57%and10 kinds of PAHs.The relative contents of organic element carbon,hydrogen,oxygen,nitrogen and sulfur respectively are 86.49%,11.44%,1.01%,0.21%and 0.85%,respectively.Iron,silicon,sulfur,aluminum,sodium,calcium sodium,calcium and heavy metal elements zinc is higher.The oil phase consists mainly of saturated and aromatic hydrocarbons with relative contents of 50%and 42%respectively,and contains a small amount of organic acids.The solid phase is composed of porous and coarse particles with an average particle size of 228?m,which are distributed between5-400?m.For water phase,oil content is 24.87 mg/L,chloride concentration is 743.80mg/L,COD is 410 mg/L,TOC is 152 mg/L,TN is 73.85,ammonia nitrogen is 52.37mg/L,sulfide is 0.23 mg/L and conductivity is 5.98.(2)The optimum pretreatment experiment scheme is that three kinds of processes combined at the same time.When the p H value is 10,the washing temperature is 75?,the ultrasonic power is 100%and the processing time is 15 min,the optimum pretreatment effect,16.56%oil content of sludge,will be obtained.(3)When the anode material is Ti/Ru O₂-Ir O₂,the muddy water ratio is 1:2,the pole plate spacing is 2 cm,the current is 4 A,the chloride concentration is 10000 mg/L and the electrolytic time is 5 h,the best treatment effect will be that the sludge oil content is 1.75%.(4)The oil content of the oily sludge samples is reduced to0.08%,the viscosity is reduced to 16.40 m Pa·s,p H value is reduced to 7.48 and the PAHs are reduced to two kinds(phenanthrene and flexion).Most of the high-content elements and heavy metal elements in excess of the standard have greatly decreased.For oil phase,only the relative content of saturated hydrocarbons increases,and the content of saturated hydrocarbons and aromatic compounds of macromolecules has decreased.For aqueous phase,the oil content is reduced to 12.95 mg/L,while the chloride ion concentration,COD,TOC,TN,ammonia nitrogen,sulfide,conductivity and so on are all slightly increased due to the added electrolyte.