| In the process of oil exploration,mining,storage,transportation and refining,a large amount of oily sludge will inevitably be produced.Because of its complex composition,oily sludge also contains a large number of toxic and hazardous substances.It has been included in the list of hazardous wastes by many countries.Disposal has become a major problem that plagues the development of the petrochemical industry.In addition,large amounts of sludge have high oil content,and recovering crude oil resources is the most ideal environmental choice.Based on the previous research,this paper aimed at the poor performance of the chemical quenchingmechanical centrifugation method,and then screened high-efficiency demulsifiers,and at the same time used heating and other auxiliary methods to demulsify the oily sludge,and characterized the physical and chemical characteristics of the separated crude oil.Finally,the possible demulsification mechanism was proposed.In addition,in view of the fast and efficient microwave demulsification,the combination of microwave and chemical quenching and mechanical centrifugation was studied to further improve the separation effect of oily sludge.First,the physical and chemical properties of three typical high oily sludges were studied.The results show that all three sludges use crude oil as a continuous phase,and emulsified water droplets and solid impurities are dispersed in it.Microscopic images also show that the sludge exists as a water-in-oil(W/O)emulsion;There is a big difference with the four components of the oil phase.Among them,the oil content of ZS sludge is as high as 85.57%,and the resource value is extremely high.Asphaltenes and other macromolecules in crude oil associate with each other to produce precipitates and enrich them at the bottom of the container.The medium asphaltene content is significantly higher than that of ordinary crude oil.In addition,the solid residue of oil sludge is mainly derived from the carried reservoir minerals and impurities mixed in the production and processing processes,and the components are mainly silicon dioxide,calcium magnesium salts,and iron salts.By screening demulsifiers and increasing the temperature at the same time,the dehydration effect of the chemical quenching-mechanical centrifugation method was improved,and the physical and chemical properties of the recovered crude oil were also characterized.First of all,it is found that the content of heavy metals in oil sludge samples varies greatly,and the differences between different heavy metal elements are more obvious.In addition,the content of heavy metals in the three sludges is significantly lower than the content of the slag after separation,indicating that most of the heavy metals are concentrated in solid residues.in.All three sludges have a shear thinning phenomenon,showing obvious non-Newtonian fluid characteristics.As the temperature increases and the shear rate further increases,the viscosity of ZS and XZ sludges basically does not change with the shear rate,and the flow characteristics gradually Transition to Newtonian fluid.Secondly,at 50 °C,the viscosity reduction coefficients of XZ and BS sludge are significantly lower than ZS sludge,indicating that the higher the oil content,the more sensitive it is to temperature,and the better the viscosity reduction effect.After a single factor analysis,the centrifugation speed was 4000 rpm,the concentration of demulsifier P9935 was 0.2%,the amount was 5%,and the dehydration rates of ZS,XZ,and BS three sludges were 70.84%,69.44%,and 75.24 at a demulsification temperature of 50°C.%,Crude oil recovery rates were 94.23%,95.73%,and 89.14%.In addition,the moisture content of the recovered crude oil corresponding to the three sludges of ZS,XZ and BS is 1.13%,2.60% and 1.78%,respectively,and the slag content is 0.045%,0.75% and 1.20% respectively.The microscopic images show that there are still some very fine emulsified water droplets and smaller slag,and the large particle slag is basically removed after centrifugation.Microwave technology was used in the demulsification experiment of oily sludge,and the effect of microwave heating on the particle size of emulsified water droplets in sludge was analyzed by DSC.Finally,microwave heating and chemical demulsification were combined to further improve the dehydration rate of sludge.It was found that the crystallization peaks of the emulsified water droplets in the original sludge were disordered,indicating that the particle sizes of the water droplets were different;after centrifugation,only a part of the emulsified water droplets with a larger particle diameter could be separated;and after the microwave treatment,it was found that the intensity of the crystalline peaks of the emulsified water droplets was significantly increased,and The direction of particle size increase indicates that the microwave heating can promote the emulsified water droplets to coalesce into water droplets with larger particle sizes.In addition,the effects of different heating methods on dehydration of sludge were compared.The results showed that the dehydration rate of XZS sludge was only about 50% after centrifugation after heating at 90°C for 60 minutes in a conventional water bath.Under high-temperature 700 W microwave heating,only 2min was heated.,The dehydration rate increased significantly,and finally maintained at about 60%;finally,by combining microwave heating and chemical demulsification,the dehydration effect of XZS sludge was significantly increased,and the dehydration rate was as high as 90.74%.When only the demulsifier was added,the dehydration rate was 66.4%;after microwave combined with chemical demulsification separation,the water content of the recovered crude oil was 0.71%,which was already as low as less than 1.0%,indicating that microwave heating assisted demulsification can further improve the dehydration rate of sludge. |
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