Visual Simulation Study On The Treatment Process Of Copper Smelting Waste Acid

The components of copper smelting waste acid are complex,containing heavy metals,fluorine,chlorine and other impurities.It will have a serious impact on the ecological environment and human health,if the waste acid is not treated before discharging.Sulfide precipitation,as a common treatment method,has outstanding advantages in reducing the amount of hazardous waste residue and improving metal removal efficiency.Nevertheless,the phenomenon of supersaturation can be generated due to the low solubility products of the sulfide precipitates.It can cause explosive homogeneous nucleation and produce considerable tiny particles,reducing the reaction efficiency and subsequent separation efficiency.The problems seriously restrict the efficient application of the sulfide precipitation.Furthermore,traditional treatment can hardly remove the fluorine and chlorine in the waste acid.Therefore,a treatment process of copper smelting waste acid was proposed,that is gas-liquid sulfide precipitation to precipitate heavy metals,field flow fractionation to separate heavy metals from each other,and finally hot air blowing to remove fluorine and chlorine.Numerical simulation was used to analyze visually each stage,aiming to provide intuitive,scientific and reliable reference and guidance for the resource treatment smelting waste acid.The main research results are as follows:（1）A CFD model of gas-liquid sulfide precipitation reactor was built to clarify the distribution adjustment mechanism of supersaturation in the reactor.Through introducing H₂S gas,the rapid flow field distribution and efficient gas-liquid mass transfer in the reactor were realized,and low and even-distributed supersaturation was achieved.It created a favorable environment for the process of sulfide reaction and the growth of sulfide particles.Furthermore,the influence of different gas phase control parameters on the sulfide reaction process was explored.It was found that the increase of H₂S（g）flow rate and the reduction of H₂S（g）bubble size were both beneficial to reduce the supersaturation of the solution and improve the efficiency of the gas-liquid sulfide reaction.It is worth mentioning that the effect of H₂S（g）bubble size on the gas-liquid sulfide reaction is more obvious.What’s more,experiments showed that the gas-liquid sulfide reactor has good feasibility,which provided an effective reference and guidance for the control and optimization of supersaturation during the gas-liquid sulfide reaction.（2）The field flow fractionation technology was introduced to realize the separation and recovery of different metal sulfide precipitates.Experimental results implied that the sulfide precipitate particles of the three heavy metals（Cu（II）,Zn（II）,As（III））could achieve different particle size distributions via adjusting reaction conditions.It laid the foundation for the field flow fractionation to achieve further solid-solid separation.Three-dimensional model of the field flow fractionation tank was established.It was found that the greater the inflow velocity,the smaller the size range of particles that could be separated.The designed cylindrical field flow fractionation tank has poor separation effect for particles below15μm.The flat field flow fractionation tanks with two structures were further designed for the separation of sulfide precipitate particles obtained in the previous experiments.Through comparative analysis,it was found that the overall flow field was more stable and the velocity distribution was more uniform in the flat field flow fractionation tank with slopes at both ends of the settlement trough.Particles with different particle sizes can be separated well from each other in this fractionation tank,achieving effective separation among particles below 10μm.（3）The flow field distribution and dynamic analysis of the process of stripping fluorine and chlorine by hot air were studied,which provided a visual reference for optimizing the stripping process of fluorine and chlorine.Blowing hot air into the tower stripping fluorine and chlorine produced a strong eddy current effect,which accelerated the processes of mass transfer and phase transformation.Studies showed that the increase of hot air temperature was conducive to the volatilization of HF and HCl.However,increasing wind temperature promoted the ionization of HF and HCl,reducing the removal efficiency of F^-and Cl^-.99%F^-and Cl^-could be quickly removed at the wind temperature of 80-100℃.Further research found that the increase of the hot air blowing rate enhanced the fluid flow and mass transfer process,resulting in an increase in the removal of F^-and Cl^-.In addition,the removal efficiency more than 99%for F^-and 94%for Cl^-could be achieved at various flow rates.