| The composition of polymer-flooding wastewater was complicate and stable while the contents of oil and suspended substance were high. Furthermore, hydrolyzed polyacrylamide (HPAM) present in wastewater made it more difficult to treat with. The oily substances (OSs) in polymer flooding produced water had been seperated into 6 subfractions by several kinds of solvents. Each subfraction obtained had been characterized by elemental and IR spectral analyses, acid value, alkaline amine content determinations, the interfacial tension between benzene / heptane solution of subfractions and distilled water and the stability of their emulsions formed were investigated in our previous work. The analysis results revealed significant differences in composition, structure, interfacial tension and emulsification among these subfractions. On ths basis of such studies, the effects of different kinds of flocculants on various synthetic emulsions stabilized by several subfractions were studied through the factor-superposition approach. The influence of HPAM which was degraded and that remained in oily water on the process of demulsification was investigated respectively. The reasons that it was difficult to treat of the polymer flooding produced water were analyzed, while the treatment countermeasures were proposed.A series of PAMAM (Polyamidoamine) were synthesized by reaction of EDA (ethylenediamine) and MA (methacrylate) through dispersion method. The degree of modified reaction was determined by potentiometric titration method, while the factors affecting the reaction, such as reaction time, reaction temperature and molar ratio of PAMAM 1.0G and DAC were discussed. Preferred synthetic conditions were as follows: reaction temperature 25℃, reaction time 11 h and molar ratio 1:3.On the basis of study on the stability of polymer flooding produced water, effects of different flocculants on emulsions stabilized by emulsion-activity subfraction or sevaral subfractions were studied. Furthermore, the factors affecting flocculation of emulsions were discussed, such as HPAM content, pH, temperature, salinity and so on. It was shown that flocculating agent with lower molecular weight and higher cationic degree had a favorable impact on the demulsification of emulsions in the absence of polymer, while flocculant with a certain cationic degree and higher molecular weight, like CPAM, played an important role in the demulsification process of emulsions with polymer and salt at the same time. In addition, CPAM and HPAM solution performed strong synergistic flocculation in the range of certain mass concentration.According to the effects of flocculants on demulsification of emulsions, formula to treat with polymer flooding wastewater was selected. To GuDao2# polymer flooding produced water with chained HPAM, CPAM performed better than other flocculants. When the wastewater was treated by the flocculants of PAC and CPAM at the ratio of 1:3, with the total dosage of 40 mg·L-1, oil content of the sewage dropped from 2350 mg·L-1 to 150mg·L-1. To GuDao5# polymer flooding produced water with crosslinking HPAM, PAC performed better than other flocculants. When the wastewater was treated by the flocculants of PAC and CPAM at the ratio of 3:1, with the total dosage of 100 mg·L-1, oil content of the wastewater dropped from 2560 mg·L-1 to 195 mg·L-1. Through test of oil-water separation , it was found that CPAM performed better than any other flocculants and factors, such as mixed efficiency between produced liquid and flocculants, floating oil and treating temperature, produced strong impact on treatment with polymer-flooding fluid. The mechanism of interaction between CPAM and HPAM was obtained through the study on effects of flocculants on viscosity of HPAM solution and Zeta potential of emulsions respectively, and IR spctrum of flocs. |
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