Numerical Simulation Of Flow Mechanics And Mixing Characteristics In Wemco Flotation Cell

The distribution of the flow field in the flotation cell and the performance of the flotation cell significantly affect the flotation efficiency.Many scholars have carried out a detailed study on the flow characteristics in the flotation cell by using CFD.Howerver,self-aerated machines have been studied.And the fluid dynamics of the self-aerated machines have not been fully characterized.There are still some problems of the large-scale self-aerated machines in the structre design and optimization.The single-phase flow field is simulated in the Wemco flotation cell.The mixing characteristics and the residence thime distribution are also analyzed.It provides some references for the theoretical basis and optimization design of self-aerated machines.The main results as follows:1)The single-phase flow field have been studied by using standard k-e turbulence model.And the effects of rotational speed and structure parameters on the fluid characteristics,pressure and flotation process performance were investigated.The results show that there two vortices observed-one vortex below the impeller and another above the impeller.Both the axial velocity,turbulent kinetic energy,pressure and the ciculation volume,power consumption increase with the rotation speed rises.When the angle of the cone is 45 degrees,the complete circulation flow field is formed in the flotation machine,and the thickness of the circulating flow is large.When the angle of the impeller blade is 0 degrees,the axial velocity of the rotor region is 4.01m/s^-1;The greater the depth of the subimmersing the wake tube,the axial velocity and the center of the turbulent kinetic region move to the wake tube,and the greater the circulation and power of the impeller,the minimum power consumption for the rotor stator spacing of 280mm is 7.10×10³W.2)Based on the steady flow field study,Mixing time has benn studied.And the influence of impeller speed and structural parameters was investigated.The results show that the mixing time is shorter with the rotation speed rises.The mixing time decreases and then increases with the increase of the angle of the cone,and the mixing time is 5.36s when the angle angle is 45degrees.The mixing time in the flotation machine is the shortest when the angle of the impeller blade is 0 and the depth of the rotor immersed in the wake tube.With the increase of the rotor stator spacing,the mixing time decreases first and then increases.3)The RTD of the flotation cell was simulation.And the influence of impeller speed,inlet velocity and structure parameters was investigated.The results show that the average residence time decreases slightly with the increase of speed,and the residence time is not change after the speed reaches 273rpm.The average residence time decrease with the rotation speed rises.The structure parameters of hood angle,mipeller blade angle,the depth of rotor and rotor-stator space is not affected the average residence time.