Study On Flocculation Technology Of Oily Wastewater Produced From Polymer Flooding

At present, polymer flooding technology has been implemented in many major oilfields in our country. Polymer flooding not only enhance oil recovery, but also make the residual polymer and viscosity of the produced fluid increase, the speed of oil-water separation reduce and the treatment capability decline. The object of this thesis is to study the flocculation technology of different flocculants on wastewater of polymer flooding, develop new type of flocculant, save the dosage of flocculant and break the conventional ways of treating, treating the wastewater economically and effectively.Firstly, based on the wastewater quality of polymer flooding, treatment law was studied by the method of chemical flocculation using common flocculants, then according to the molecular structure, advantages and disadvantages of flocculants, the light transmission of the supernatant liquid was enhanced with the combined and compound flocculants. After that, the flocculation performance was evaluated, the main index that was evaluated was the concentration of residual partially-hydrolyzed polyacrylamide, oily content, chemical oxygen demand, relative viscosity of the supernatant liquid and floc speciation, in which the concentration of residual partially-hydrolyzed polyacrylamide was the key target. The experimental results proved that under the optimal dosage and temperature, by the use of the appropriate inorganic and organic flocculants, the content of the former four indexes were all reduce, the flocculation performance improved.According to the different flocculation performance, the relationship between the floc speciation and the molecular structure of the flocculant, a type of inorganic compound polymer flocculant poly-aluminum-ferric-silicate-chloride (PAFSC) was synthesized, the optimal synthetic condition was: when preparing poly silicic acid, the concentration of silicon dioxide was 2.5%, pH value was 5.0. When preparing PAFSC, the molar ratio of aluminum and ferric was 2:1, the molar ratio of metal elements and silicon was 1:1, the temperature of the reaction was room temperature. Combinating PAFSC and poly dimethyldiallyl ammonium chloride (PDADMAC), when the mass ratio of metal elements and PDADMAC was 40:1, the dosage was 150 mg/L, the flocculation temperature was 37℃, the light transmission of the supernatant liquid can achieve 98.5%.Finally, in order to save the dosage and the cost of the flocculant, protect the environment, electrolytic flocculation was studied based on the chemical flocculation, and the joint research was carried on. The optimal experimental condition of electrolytic flocculation was determined by orthogonal test: the space between electrodes was 9 mm, the electrolytic time was 16min, the current density was 1000A/m2. After treating the wastewater of polymer flooding by electrolytic flocculation and PAC, the dosage of PAC can save nearly 700 mg/L, and the light transmission of the supernatant liquid was 99%. After treating the wastewater of polymer flooding by electrolytic flocculation and CPAM, the dosage of CPAM can save nearly 200 mg/L, and the light transmission of the supernatant liquid was 98.6%.