Numerical Simulation On Multiphase Flow In The Both Side-blown Oxygen-enriched Copper Smelting Furnace

Both side-blown copper smelting process is an efficient,energy-saving,environment-friendly new copper smelting technology,which uses the oxygen-enriched air blown into the slag to stir slag and it can strengthen mass and heat transfer of the melt,reduce the dissolution of matte in the slag,and improve dynamics of the reaction in the melt.But now,there are some problems of this technology,such as:unclear cognition of emulsified layer,undefined flow conditipn in melt and the variation of oxygen lance operating parameters.In order to understand the emulsified layer phenomenon and flow regularity and select oxygen lance operating parameters,the commercial software Ansys/Fluent13.0 was used to simulate the multiphase flow in the bath.The flow field,velocity field,turbulent kinetic energy,gas holdup and wall sheer stress were studied in the gas-liquid two phase flow under the different oxygen lance operating conditions,including gas flow rate,nozzle angle,nozzle arrangement and nozzle diameter and proper oxygen lance operating parameters were obtained.Furthermore,the material entrainment and the thickness of emulsified layer were simulated by using the industrial physical parameters under the different gas flow rates and nozzle angle.The results are as follows:(1)A mathematical model of the multiphase flow in the both side-blown copper smelting bath was established,where Eulerian model was used to simulate the flow process and standard ?-? model was used to simulate the turbulence.The accuracy of the model is verified by comparing the flow fields obtained by PIV technology and numerical simulation and the mixing time.(2)With the increase of gas flow rate,he superficial gas velocity increased,which resulted in the increase of stirring strength and contributed to the heat and mass transfer in the bath.However,the excessive gas flow rate caused the gas stir the V copper matte layer and the loss of copper matte increased.Moreover,the distribution of gas holdup was more uneven.Therefore,in the premise of the stability of the copper matte zone,the appropriate increasing of gas flow rate contributed to enhance the smelting process and the optimal gas flow rate was 20m3/h?23m3/h.(3)With the increase of nozzle angle,the longitudinal gas velocity increased and the transverse penetration depth decreased,which caused the decrease of stirring strength in the center of the bath.When the nozzle angle was small,the increase of angle was conductive to the uniform distribution of gas and the increase of gas holdup.However,when the nozzle angle was too big,the residence time was shorter,which caused the decrease of the gas holdup.The optimal nozzle angle was 7°.(4)Adjacent nozzle arrangement enhanced the stirring effect of gas,which increased the velocity and turbulent kinetic energy,but the fluctuation of copper matte layer became also intensified.Besides,the increase of local gas holdup caused the uneven distribution of gas and the increase of wall sheer stress near the oxygen lacer.Hence too compact nozzle arrangement was inappropriate.However,if the nozzle arrangement was too sparse,the stirring strength would decrease.Thus the optimal nozzle arrangement was local compactness and global sparse,namely 1#nozzle arrangement.(5)With the decrease of nozzle diameter,the pressure of nozzle outlet increased,as the gas flow rates were the same,which caused the increase of superficial velocity.Thus the stirring effect was enhanced but the fluctuation of copper matte layer was also intensified.When the nozzle diameter was too big,the dead zone in the bath became larger and the smelting intensity decreased.Therefore,the optimal nozzle diameter was 3.7mm.(6)Material entrainment process was concluded as follows.The interface of material was first fluctuant and the material was mixed with the melt,which caused the material layer thicker.Then with the strong stirring,the material diffused into the melt gradually and was finally mixed with the melt uniformly.With the increase of gas flow rate,the stirring effect was enhanced and the turbulent kinetic energy and the flow velocity of the melt were increased,which made material distribute into the melt faster and more uniformly.With the increase of nozzle angle,the stirring intensity of the lower part in the bath was enhanced.Hence the gas distribution was more uniform and the turbulent kinetic energy was increased,which contributed to the uniform distribution of material.(7)In the process of smelting,the strong stirring caused the interdiffusion between slag and copper matte,where the emulsified layer consisted of copper matte,slag and gas was formed and the thickness of emulsified layer became constant.In addition,the thickness of emulsified layer increased with the increase of gas flow rate and nozzle angle.Therefore,the nozzle angle and the gas flow rate should be decreased to reduce the loss of copper matte.The numerical simulation results provides theoretical foundation for further studying on the flow field and the mass,heat transfer in both side-blown copper smelting process.