Important Chlorination Hydrometallurgical Process - Clear Process

    Ferric chloride leaching is easy to control, more extensive study, the formation of many processes. More representative is the Clear ( CLEAR ) process developed by Duval ^{[1 ]} . CLEAR is the abbreviation of " copper leaching electrolysis and regeneration " which reflects the main unit of the process. The leaching of chalcopyrite concentrate is divided into two sections, as shown in the figure below.

    The first section is immersed in the air , and the leachate obtained by the second stage is introduced into the reaction with the new chalcopyrite . The leachate contains FeCl ₃ , NaC1 and CuC1 ₂ . This process actually reduces the high iron and copper ions in the leachate, producing ferrous and cuprous ions:

CuFeS ₂ + 2CuC1 ₂ + FeCl ₃ ==== 3CuCl + 2FeC1 ₂ + 2S

in 107 ° C The reaction was carried out for 4 hours , and about half of the chalcopyrite reacted. The second stage of leaching is the reaction of a section of slag with an electrolyte anodized by the electrolysis cell, and continuously venting air to supplement the oxidant to oxidize and hydrolyze the iron.
The rate of oxidative leaching is highly dependent on the mineral particle size and reaction temperature. Tests have shown that the mineral size is less than 325 mesh, 107 °C Under 100 kPa air pressure, oxidation takes 12 h . With pure oxygen, it only takes 6 hours . If the temperature rises above the melting point of sulfur 130 ° C , complete reaction with oxygen for 0.5h . The industrial test uses an oxygen partial pressure of 0.28 MPa . 140 ° C The lower air was leached, and the reaction was completed in about 1 hour while partially oxidizing and precipitating iron. The filtered leachate is then reacted with blister copper to reduce copper ( II ) in the leachate to copper ( I ). The cuprous solution is sent directly to the electrowinning without purification. A special electrolytic cell with a diaphragm in between is used, and the diaphragm is a semipermeable membrane. The cuprous ions in the cathode region are reduced to form electrolytic copper powder, and the anode region is cuprous oxide and ferrous ions. Therefore, the power consumption of the electrowinned copper is much lower than that of the copper sulfate solution.
From 1976 to 1982 , Clear method carried out an industrial test of 91t/d , which proved that the process is feasible. However, due to the low quality of copper products, the need for refining, and the recovery of associated silver have yet to be resolved. process.
References :
1. Kyuchoukov G, Mihaylov Y, Hydrometallurgy, 1991, 27, 361