Study On The Paration Of Oil-in-water Emulsion Via Coagulation And Ultrafiltration

At present,exploitation of oilfields in china has primarily entered its post stage characterized by high water cut;more specifically,the crude oil contains about 30%?80%water,and some water content even reaches up to 90%.In reality,the annual production of produced water is huge,and its composition and properties is very complex.Consequently,the traditional methods of produced water management cannot meet the requirements for reinjection,discharge,and reuse.Therefore,a joint process of using coagulation and ultrafiltration membranes is proposed to treat produced water in this study.Here we intend to investigate the effects on emulsified oil of produced water treated by the joint process via using coagulation and ultrafiltration membranes.Firstly,a uniform,small and stable emulsion was prepared by ultrasonic method,and then three different coagulants consisting of Al2(SO4)3,FeCl3,AlCl3 was used for preprocessing.The coagulant exhibiting the best performance was selected by varying dosage of coagulants and the properties of feed solution.Additionally,the influence of operating conditions on membrane performance and the fouling behavior of membranes were also investigated.Our experimental result confirms that FeCl3 exhibits the best adaptability to the feed solution with a wide range of variations in pH,temperature.And it also demonstrates the best performance on improving the quality of feed water in terms of turbidity and TOC(total organic carbon).Specifically,the removal rate can reach 96%,whereas the ultimate concentration of TOC is entirely above 23 mg/L.By inspecting on the membrane flux?TOC and turbidity along with SEM and EDS assistance of analyzing membrane surface fouling before and after the experiment,we find that the coupled processes not only reduce the final content of TOC to be of<13 mg/L,reached the required water quality standard for rejection,but also mitigate membrane fouling remarkably and maintain the stability of permeate flux within a long period.During the filtration period,it was found that on-line periodic backwash can effectively remove reversible fouling layer and mitigate membrane fouling.In this study,the optimization of operational condition was considered as 20-min filtration and 60-sec backwashing.The result shows that on-line periodic backwash can reduce the rate of water flux decrease,and maintain the stability of membrane flux within a long period.