| This paper firstly resumed the characteristics and treatment status of polymer flooding produced water that generated in the process of enhanced oilfield recovery. The characteristics of this kind water are high concentration of partially hydrolyzed polyacrylamide(HPAM), large viscosity and poor flocculation effect, therefore, enhanced micro-electrolysis technology was proposed to treat polymer flooding produced water, especially treat the characteristic pollutants-HP AM in it.The traditional micro-electrolysis packing is easy to hardening and passivation, and need to change frequently. In view of those disadvantages, structured micro-electrolysis packing was prepared as micro-electrolysis packing in this paper. Firstly, the type of binder of iron-carbon micro-electrolysis packing was investigated. Because of the particularity of produced water, packing made with the traditional clay binders had strong adsorbability (typically, adsorption effect of packing, made with calcium bentonite as binder, on COD and HP AM removal rate reached67.4%and64.5%respectively). In this paper, alkaline silica sol with smaller adsorbability was selected as binder of packing; the effects of packing ratio, calcination temperature and time and types of additives on the packing’s properties were studied. The XRD results of packing indicated that packing would be gradually oxidized as tempretures rise, and oxide transformed from Fe2O3to Fe3O4. Increasing calcination time only increased oxide content and did not change the type of oxide. The BET results of packing with different additives indicated that the specific surface area of packing adding ammonium oxalate was the largest, reached3.017m2/g, and treatment effect of this kind of packing on polymer plooding produced water was better than that adding ammonium bicarbonate or ammonium chloride. Ultimately, the basic preparation conditions of packing was determined: Fe:C=5:1, ammonium oxalate dosage was0.5%, calcination temperature was650℃, calcination time was2hours.Adding copper in packing could increase the hardness and specific surface area, and adding aluminum in packing could maximize specific surface area, while the packing’s hardness reduced. Both of the packings could achieve a good treatment effect to polymer flooding produced water under acidic, neutral and alkaline conditions. However, during treatment process Fe/Al/C packing was confronted with seriously mass loss (average mass loss rate of each time was up to4.9%). This paper finally chose iron-copper-carbon packing for micro-electrolysis process with optimal Fe/Cu/C radio of20:1:3.Micro-electrolysis technologies coupled with aeration, H2O2and ultrasound were adopted respectively, and the optimum reaction conditions were studied at the same time. The results indicated that micro-electrolysis coupled with aeration could improve removal rate of HPAM and COD for12%and10.2%respectively, micro-electrolysis coupled with H2O2could improve removal rate of HPAM and COD for14.7%and11.5%respectively, and micro-electrolysis coupled with ultrasound could improve removal rate of HPAM and COD for27.2%and25.2%respectively. The decomposition states of HPAM treated by different methods were analysised through infrared characterization of model wastewater containing HPAM. The results showed that the micro-electrolysis coupled with ultrasound technology could obtain effluent with the least kinds of organic functional groups, a large number of HPAM came to degrade due to their molecular chain scission, and its reaction time was also the shortest. After reacting for1h, the concentrations of COD and HPAM were98.6mg/L and33.1mg/L respectively, and COD value could meet the first level requirement of GB8978-1996, Therefore, micro-electrolysis coupled with ultrasound technology was most favorable for treatment of polymer flooding produced wastewater. |
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