Separation Process Simulation Of Waste Oil Emulsion Strengthened By Coupling Electric And Swirling Fields Based On Population Balance Theory

The recycling of industrial waste oil has great significance in ecological protection,energy resources,etc.It is an important guarantee for the sustainable development of industrial economy.In the process of recycling industrial waste oil,the key link is demulsification and dewatering.At present,it is difficult to meet the requirements of high-efficiency and low-cost purification treatment by single method or operation unit.In view of this,the reasonable integration of two or more operating units or process methods was considered to achieve efficient dewatering and purification.A double-field coupling separation system strengthened by a high-voltage electric field and a swirling centrifuge unit was proposed.For this system,a numerical model based on the population balance theory was established in this paper.The flow field distributions in the coupling system and its separation performance were investigated to provide necessary support for design and development of an efficient industrial waste oil demulsification and dewatering device.Firstly,the application scope and necessity of the basic theory of the population balance model was discussed.The coalescence and breakup mechanism of emulsified droplets under the action of electric and swirling fields was summarized,the coalescence and breakup rate equations in the coupling field were deduced,and the coalescence kernel function under coupling fields was obtained.Secondly,on the basis of considering droplet coalescence and breakup,the flow field and electric field governing equations,and population balance equation were combined to establish the simulation model of the separation system strengthened bycoupling double fields.The user-defined function was utilized to compile droplet coalescence and breakup kernel function codes.And then the effects of operating parameters(voltage amplitude,inlet flow velocity and split ratio)and structural parameters(overflow pipe insertion length,overflow pipe diameter and swirling chamber diameter)on flow field distribution and separation performance were investigated.Thirdly,the response surface method was used to optimize the structural parameters and operating parameters.The Box-Behnken method was used to design the experiments,and the corresponding numerical experiments were performed.According to the results,the response models of separation efficiency under different structural and operating parameters were established to obtain the optimum parameters.Finally,a separation device strengthened by coupling double fields was set up,and the demulsification and dewatering experiments were conducted to investigate the effects of operating parameters on the droplet size distribution and separation efficiency in the coupling system.The results show that the numerical results are basically consistent with the experimental data.The numerical model of the coupling separation system established in this paper can accurately predict and analyze the oil-water separation process in the coupling system.