Study On Demulsification And Dewatering Technology Of Tank-Cleared Oil

The tank-cleared oil,which is produced in the mechanical cleaning process of the oil storage tank,is composed of three phases of oil,water and mud,and has the characteristics of large quantity and difficult treatment.In this paper,the research purpose is the recovery and compliance treatment of oil components in clear tank oil.Firstly,the basic composition and characteristics of the clearing oil are analyzed.Moreover,the method for measuring the economical and high-efficiency oil content is constructed for the clearing oil.Finally,the experimental research on the development of processing technology is carried out.The research in this paper shows that:(1)The composition of the clearing pot oil is:oil content is 73～78%,solid content is 1.3～3%,and water content is 22%～25%.The oil quality is high and has good reuse value.The volume average particle diameter of the solid phase of the clear pot oil is 74μm.The solid matter in the clear pot oil is mainly composed of clay and sand,and the clay content is 55.4%,which is easy to emulsify with asphalt and water.The results of the four-component analysis were:24.5%for gum,13.5%for asphaltene,39.6%for saturation,and 22.4%for aromatics.(2)The method for determining the oil content in the clear pot oil is constructed as:ultrasonic demulsification+infrared spectrophotometry.When the ultrasonic time of ultrasonic demulsification is 10 min,the ultrasonic frequency is at 28 k Hz,and the ultrasonic temperature is at 60°C,the oil content of the infrared spectrophotometry oil content is 72.4%,which is close to 74.5%of the gravimetric method with a long measurement period,far higher than the 64.07%of the single infrared method with large error.(3)The main process idea of clearing tank oil treatment is“demulsifier+ultrasonic treatment+centrifugal separation”.The choice of demulsifier formulation is AE-9901and TA-1031 demulsifier in a ratio of 2:1,dosage is 150 mg/L,sonication is at 1 W/cm~2,ultrasonic frequency is at 28 k Hz.The ultrasonic time is 8 min,the ultrasonic temperature is 65°C,the centrifugal separation speed is 5000 r/min,and the centrifugation time is 7min.Under this process condition,the oil recovery rate of the clear pot oil is above 94.2%,and the dewatering rate of the clearing pot oil is above 94.7%.Orthogonal experimental analysis of the influencing factors shows:the dosage of the agent>temperature effect>ultrasound assisted>centrifugation rate.(4)The optimum parameters of the precipitated water after centrifugation are:flocculation temperature is at 30°C;flocculant type is hydrolyzed polyacrylamide(HPAM)+polyaluminium chloride(PAC);Flocculant dosage:50 mg/L for PAC and 10mg/L for HPAM.The dissolved COD decreases by 90.4%and the residual oil content decreases by 83.9%.Among them,in the"Integrated Wastewater Discharge Standard"(GB8978-1996),suspended soilds and petroleum have reached the first-class standard.