| Flotation purification as an efficient, rapid and solid-liquid separation technology has been widely used to remove grease and suspended solid in petrochemical wastewater treatment. The traditional dissolved air flotation process exposed many problems in engineering applications. For example, dissolved gas cylinders are bulky, filling layer is easy to plug, reaction system covers a large area and dissolved gas release devices are easy to plug. To improve its treatment efficiency of oily wastewater, this paper researched and developed some key technologies such as dissolving air, releasing and mixing reaction.This experiment was divided into two phases. In the first phase, main affecting factors were studied with laboratory experiment devices and key parameters associated with technology application were determined. In the second phase, a pilot-scale test was carried out in an oil field using an integrated flotation device and the operation stability of the system was examined.The test raw water was re-emulsified by using air flotation scum in an oil field, the oil content and SS were about 60 mg/L respectively. The experimental results showed that when the flux of raw water was 0.5 m3/s, the best operating parameters included:saturation pressure was 0.60 MPa, reflux ration was 20%, GWP was 13%, the rate of flocculating was 0.8 m/s, retention time was 45 s, the adding quantity of PAC was 60 mg/L and SS and oil content in effluent were less than 5 mg/L and 2 mg/L respectively. It was helpful for copolymerization with air-flotation when aerated water was added in the middle of conversionzone of tubular reactor, the removal rates of oil and SS were obviously improved. A simple mathematical model of tubular-reactor was built at last, which could be used for engineering.Laboratory experimental raw water was obtained by using an oil flotation scum preparation, oil content, and SS contents were in stable condition at the 50mg / L or so. The results show that in the original water flow 0.5 m3/h under the premise of optimum operation parameters are: dissolved gas pressure of 0.60 MPa, reflux ratio 20%, gas-water ratio 13%, tube-type reactor flocculation rate 0.80 m/s, residence time 45 s, PAC dosage of 60 mg / L, this time, water quality: the effluent SS concentration≤5 mg/L, oil content≤2 mg/L. In the tubular reactor the reaction by adding dissolved air and water in central segment is conducive to copolymerization flotation, the removal of oil and SS has improved significantly. Finally set up a simple tubular reactor mathematical model can be used to guide project.A small integrated unit (design flow 0.5m3/ h) was used in an oil field sewage treatment plant for a pilot-scale test to mainly examine the oily wastewater treatment effect and the operation stability of the floatation device. The flotation device ran for 45 days continuously and the results showed that: when the SS and the oil content of the influent were both lower than 100 mg/L, the effluent SS≤15 mg/L, oil content≤2 mg/L, and the removal rate of those were 85% and 96% respectively. The removal effect was good. When the SS and the oil content of the influent were both higher than 100 mg/L occasionally, the effluent quality was normal and the flotation device ran stablly.In short, efficient dissolved air system, non-blocking release unit, tubular reactor etc. have good treatment effect and stable operation in oily wastewater treatment and will have broad application prospects in the petroleum, chemical, steel and other industrial oily wastewater treatment.
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