Influence Factors And Technical Boundaries Of Settlement Separation In PFPW Treatment With Dissolved-Air Flotation Process

Along with the exploitation of the oil fields entering middle and high water cut period,and the development methods has changed from water drive to chemical drive,the produced water not only becomes more complex in water quality,but also increases significantly in scale.For example,polymer-flooding produced water(PFPW)shows the qualities such as amount of reducing substances and emulsified oil,the increases of water viscosity,and the decreases of oil particle size.So a series of problems such as the worse ability of containing the pollutants,the longer gravity sedimentation time,the shorter backwashing cycle during the treatment.The high efficiency,environmental protection and standard treatment process for PFPW is facing many challenges.Therefore,this paper study on the sedimentation unit of the treatment process.First,test and analysis of water quality characteristics should be done,the influence of the reflux ratio,throughput,pressure,and polymer concentration in PFPW on the flow field and dissolved-air flotation and sedimentation effect was investigated in the study by the mixture model of numerical simulation.According to test and analysis of water quality characteristics and numerical simulation results,make sure the dissolved-air flotation and sedimentation process line for PFPD,and provide basis for process methods and structural optimal improvement.In order to provide effective support for realizing the improvement of PFPW treating or structuring improvement of sedimentation tank,we decide to optimize air distribution system.The results of numerical simulation show that low polymer concentration,low throughput,or increase pressure and reflux ratio properly is beneficial to the formation of stable flow field,get ordered particle trajectories and give full play to flotation effect.The concentration of polymer has the most significant effect on dissolved air flotation and sedimentation process,according to the numerical simulation results,it can be concluded that 60%to 65%oil removal rate and 30%to 35%suspended solids removal rate can be achieved by the process under the conditions of polymer concentration of 300 mg/L to 450 mg/L,treatment flow of 100 m3/h,reflux ratio of 25%,and pressure of 0.3 MPa to 0.6 MPa.The distance between gas release heads is 0.856 m,the number of gas release heads is 22.The gas distribution ring adopts a double ring structure,and its height is controlled within 10.6 m to 9.7 m of the settlement tank.We can keep the oil removal rate above 65%and the suspended solids removal rate above 35%when the concentration of polymer reaches 500 mg/L by optimizing the structure of air distribution system.