Euler simulation of hydrocyclone pre-separation before oily wastewater membrane treatment based on Population balance model

Membrane technology is considered an effective technique for separating and purifying oily wastewater, and membrane fouling caused by surfactant adsorption or oil droplet blockage of pore channels. Therefore, before membrane treatment of oilfield wastewater, it is necessary to carry out pretreatment to reduce the oil content of oilfield wastewater and lay the foundation for improving membrane treatment efficiency. This article mainly uses the finite volume method to discretize the control equations, and uses the pressure velocity coupling method to analyze the primary hydrocyclone separation efficiency of oilfield produced fluids with oil content ranging from 10 to 30%. It explores the hydrocyclone flow field and particle trajectory of mixed fluids in hydrocyclones under different oil content states. The results indicate that the distribution of oil phase volume fraction in the hydrocyclone is comprehensively controlled by inlet flow velocity, oil content, and structural parameters such as cone angle and overflow pipe depth. At low to medium flow velocities (5.0 ~ 15.0 m/s), the centrifugal force field dominates the enrichment of oil towards the axis, and the coalescence effect is enhanced. At high inlet flow rates, the oil phase outflow channel changes from a dual channel of overflow and bottom flow to mainly overflow. When the inlet flow rate reaches 20 m/s, the shear force increases, causing the oil droplets to break and the radial migration path to deviate from the design. The flow velocity distribution becomes more complex, resulting in the distribution characteristics of the oil volume fraction in the mixed liquid becoming more complex, and small-sized oil droplets are discharged from the bottom flow. The increase in oil content enhances the probability of coalescence by increasing viscosity, but also increases Stokes resistance, resulting in prolonged droplet retention time, increased risk of shear failure, and intensified fluctuations in oil phase volume fraction at the overflow port.