Study On Purification Of Copper Electrolyte With De-coppering And Impurities Removal By Cyclone Electrowinning Technology

Copper is an important resource for the development of national economy. Copper electrorefining is the main process for copper production. In copper electrorefining, the impurities including As, Sb, Bi and so on gradually accumulate in the electrolyte, which results in excess impurities in cathode copper. Therefore, it is necessary to quantitatively purify the copper electrolyte regularly. At present, the electrowinning is the main method for the electrolyte purification. However, it is required that the copper electrolyte is of high copper ion concentration and low impurities concentration during the conventional electrowinning process. Moreover, concentration polarization is serious during de-coppering and removal of impurities process, which caused a lot of copper loss, low copper recovery, high electrical energy consumption, as well as the release of acid mist and poisonous AsH3gas, severely harmful to the environment and human health.This thesis develop a new cyclone electrowinning technical route to deal with the problems of great copper loss, low removal rate of impurities, and high electrical energy consumption, and poor production environment of "Daye" Nonferrous Metals Company. To ensure the quality of the cathode copper and the high rate of impurities removal, a new technical route which consists of three-steps de-coppering process and one-step removal of As, Sb and Bi was designed in accordance with the Cu2+concentration. Through the laboratory test and pilot plant test, the effects of current densities, cycling flow rate and temperature on current efficiency, cell voltage, the quality of cathode copper and the rate of impurities removal were investigated. The optimum conditions and technical parameters were obtained.The laboratory test results show that, in the first step of de-coppering, the quality of cathode copper can meet the criterion of GBT467-1997high-purity cathode copper (Cu-CATH-1), and the current efficiency reaches to96.5%when the conditions are determined as follows:>20g/L of Cu2+concentration,300A/m2of current density and600L/h of flow rate; in the second step, the quality of the cathode copper can meet the standard of the cathode copper (Cu-CATH-2), and the current efficiency reaches to92.8%when the conditions are determined as follows:>8g/L of Cu2+concentration,400A/m2of current density and700L/h of flow rate; in the third step, the cathode copper with99.67%purity is obtained and the current efficiency reaches to90.1%when the conditions are determined as follows:>3g/L of Cu2+concentration,300A/m2of current density and900L/h of flow rate; In the fouth step, the concentration of Cu2+in final copper electrolyte is0.009g/L and the rate of removal are90.6%,98.9%and99.9%for As, Sb and Bi respectively when the conditions are determined as follows:<3g/L of Cu2+concentration,500A/m2of current density and250L/h of flow rate.Through the field industrial test, verify the optimum conditions and technical parameters and evaluation of technical and economic index of the process. The results show that, in the first step of de-coppering, the quality of cathode copper can meet the high-purity cathode copper, and the current efficiency reaches to99.08%when the conditions are determined as follows:>20g/L of Cu2+concentration,500A/m2of current density and9m3/h of flow rate; in the second step, the quality of the cathode copper can meet the standard of the cathode copper, and the current efficiency reaches to93.56%when the conditions are determined as follows:>8g/L of Cu2+concentration,400A/m2of current density and8.5m3/h of flow rate; in the third step, the cathode copper with99.93%purity is obtained and the current efficiency reaches to89.66%when the conditions are determined as follows:>3g/L of Cu2+concentration,300A/m2of current density and9m3/h of flow rate. In the fouth step, the concentration of Cu2+in final copper electrolyte is0.004g/L and the rate of removal are89.3%,80.0%and99.9%for As, Sb and Bi respectively when the conditions are determined as follows:<3g/L of Cu2+concentration,800A/m2of current density and6m3/h of flow rate. During the whole de-coppering process, the copper recovery rate reaches to93%and the average current efficiency of94.42%. The relative current efficiency of arsenic is41.4%during removal impurities stage, above3 times higher than that of inducing removal of arsenic technology. Meanwhile, the remained black copper sludge after electro-winning can be further used to extract As, Sb and Bi because of copper to arsenic ratio in product reaches0.3039:1. On the other hand, compared to the two stage remove impurities technique of Daye company, cyclone electrowinning technology possess de-coppering power consumption decreased by about25%, and arsenic removal power consumption decreased by about50%.In this paper, a new cyclone electrowinning technology for the purification of copper electrolyte with de-coppering and removal of impurities was developed and designed, provides a feasible way for the industrial production and has opened up the high efficient and selectivity of a copper electrolytic purification, clean environmentally friendly way.