Study On Treatment Technology Of Oily Wastewater By Combination Of Electric Field Demulsification And Dynamic Ceremic Membrane

With the popularization and application of tertiary enhanced oil recovery technologies such as polymer flooding and ASP flooding,the particle size of oil droplets in oilfield produced water becomes smaller and the degree of emulsification is serious.the series combination of conventional unit treatment technologies such as air floatation and deep media filtration is difficult to meet the reinjection standard.Inorganic ceramic membrane is driven by transmembrane pressure difference and filtered and separated by membrane sieving.it has the advantages of high temperature resistance,corrosion resistance,high mechanical strength,good effluent quality and so on.However,due to the problems of easy fouling and high cost of operation and maintenance of conventional ceramic membrane,there are very few engineering application cases in the field of oily sewage treatment.There is an urgent need to carry out systematic and in-depth theoretical and experimental research on the pretreatment of strong emulsified oily wastewater,the use of new ceramic membrane modules and the design of corresponding main equipment.Firstly,the paper summarizes the development history of advanced treatment technology of oily wastewater,points out the bottleneck problems existing in the treatment of oily wastewater with high emulsification at present,and proposes to use electric field demulsification as the pretreatment technology of ceramic membrane separation,and then based on theoretical analysis,it is pointed out that the technical feasibility of series combination of electric field demulsification and dynamic ceramic membrane to treat high emulsified oily wastewater.Secondly,the experimental study on the treatment of oily wastewater with high emulsification by DC pulsed electric field is carried out to verify that DC pulsed electric field demulsification can effectively promote the growth of oil droplet size.Under the best electric field operation parameters of current density 5m A/cm2,frequency 500 Hz and duty cycle 0.5,the size of oil droplets in oily wastewater increased by 196.7% after 10 min treatment by electric field.Then,through computational fluid dynamics(CFD)numerical simulation,three ceramic membrane filtration methods such as dead-end filtration,dynamic rotating blade combined fixed membrane cross-flow filtration and dynamic rotating membrane cross-flow filtration were compared,and the membrane surface average pressure,basic membrane flux,membrane surface shear rate,oil removal efficiency and energy consumption were comprehensively compared,and dynamic rotating ceramic membrane cross-flow filtration was selected finally.On this basis,based on the dynamic rotating ceramic membrane cross-flow filter,the experimental study on the treatment of high concentration O/W oil-water emulsion and high emulsification oily wastewater was carried out.The results show that transmembrane pressure 0.1MPa and motor speed1400 rpm are the best filtration operation conditions for treating high concentration O / W oil-water emulsion,under these conditions,the antifouling ability of diaphragm is the best,and the oil removal rate is 99.88%when separating oil-containing volume fraction 10%O/ W oil-water emulsion;transmembrane pressure 0.1MPa and motor speed 900 rpm are the best filtration operation conditions for treating oily sewage.In order to make the indoor experimental research closer to the engineering practice,the paper also carried out the experimental study on the treatment of high emulsification oily wastewater,alcohol oily wastewater and high emulsification polymer flooding oily water by dynamic rotating ceramic membrane cross flow filter.the results show that the presence of solid suspended solids and polymers can accelerate the fouling on the surface of the diaphragm and reduce the membrane flux,but alcohols have no significant effect on the separation efficiency of ceramic membrane.Specifically,the oil removal rate of high emulsification containing suspended oily water and alcohol oily sewage can reach more than 98.5%.Although the oil removal rate in the treatment of high emulsification polymer flooding oily wastewater decreased to 95.75%,after the microfiltration membrane was replaced by ultrafiltration membrane,the oil removal rate could be increased to 99.3%.Based on the performance test and evaluation of oily wastewater treatment by "electric field demulsification-dynamic ceramic membrane series combination process",the experimental results show that under the conditions of optimum electric field parameters and ceramic membrane process parameters,microfiltration membrane is used to treat suspended oily wastewater with high emulsification concentration of 50mg/L,polyacrylamide concentration of 200mg/L and oil content of 2000mg/L,and the oil removal rate can reach more than 99.4%.And the membrane flux was maintained above 10L/(min ·m 2)for a long time.Finally,with the application of mechanical design and other knowledge,the structural design of dynamic ceramic membrane engineering prototype is carried out.The research work of this paper not only enriches the research connotation of ceramic membrane separation technology,but also provides a useful reference and feasible solution for the treatment of highly emulsified produced water in oil field.