Structure Optimization Of Two-stage Cyclone Flotation Device For Oily Water Treatment

The process of cyclone flotation oily water treatment has the advantages of compact structure,large capacity and good treatment effect.Based on the extensive research on the technology and equipment of cyclone flotation in oily wastewater treatment,the two-stage cyclone flotation device for oily water treatment was designed.Based on the reasonable selection of numerical simulation method,the key structural parameters of cyclone flotation device are simulated and optimized.Based on the optimized prototype of cyclone flotation device,Oil removal performance was studied.The design criteria of cyclone flotation device in oily water treatment have been set up.The main contents and conclusions of this paper are as follows.The force and movement law of dispersed phase particles in the cyclone flotation system are analyzed,and the mechanism of the swirl field promoting floatation is clarified.The idea of two-stage cyclone floatation is put forward:the flow field of the cyclone floatation device is divided into two parts by the internal components,including a swirling separation area with a large swirling intensity,and a weakly swirling flotation area with stable flow field.Based on the idea of two-stage cyclone floatation,the structural design of two stage cyclone flotation device for oily water treatment was carried out.Numerical simulation and optimization are carried out for the key structural elements,such as the height ratio,diameter and height of the inner cylinder,the inclination angle and width of the guide plate,the angle and width of the baffle,the diameter of the cone and the inlet pipe diameter.The flow field characteristics and bubble flotation efficiency under different models are described by the tangential velocity distribution and the gas volume fraction in overflow outlet,and finally the optimal structure size of the cyclone flotation device is determined.A set of cyclone flotation oily water treatment experiment system was designed.Based on the experiment system,the performance of the wastewater treatment was tested.The experimental results showed that:In the range of 0.6².2 m³ h^-1,when Q=1.0 m³·h^-1 the oil removal efficiency of the cyclone flotation device is the highest.For the oily water with certain oil content,there is the optimal gas content when the oil removal efficiency is highest,and the optimal gas content increases with the growth of the oil content.In the range of flow ratio?0⁰.15?,the oil removal efficiency increases with the growth of the flow ratio,but the growth rate decreases.With the growth of the oil droplet diameter,the oil removal efficiency increases,but the rate decreases.When the gas content is certain,there is the optimal oil content to make the oil removal efficiency is highest,and the optimal oil content increases with the growth of the gas content.The design criteria of cyclone floatation device size is determined:when the capacity demand of a single device is Q,the diameter of the cyclone floatation device can be calculated by ???,the inlet diameter can be calculated by d_in=0.0296Q^0.5×D^-0.25,and other size can be calculated by the dimensionless size determined by simulation and the value of D.The calculation criteria of stages of cyclone floatation device is determined:When the oil content in treated water requirement is less than 30 mg·L^-1,and the handling capacity is 1.0m³·h^-1,if the oil content in oily water is less than 150 mg·L^-1,Single stage equipment can meet the requirement;if the oil content in oily water is between 150 mg·L^-1and 405 mg·L^-1,two stages can meet the requirement;if the oil content in oily water is more than 405 mg·L^-1,three stages can meet the requirement.