Copper processing can be divided into two main process stages namely: conventional Copper concentrate process and conventional Electro refining Process.
Conventional Copper concentrates process
In the beginning of conventional Copper concentrate process , The copper ore contains about 31% Copper, Iron 23%, Sulphur 31%, Silica 6%, Calcium Oxide 0,4%, Zinc 0,3%, Pb 0,04%, Gold 30 g/T and Silver 45 g/ T. After the process the Copper Cathode will have a purity of 99.99% Cu; the Copper Anode will contain 99,4% Cu, 0,004% S, 0,004% Zn, 0,08% Pb, 96 g/T Au and 144 g/T Ag. (P.L.Couterier,1997)
Copper ore blended with coal and in-plant recycled materials of which moisture is 710%, is dried to 0,5% using a rotary kiln / flash dryer. Dried concentrate is transported to feeding tank system by conveyors. Fluxes are discharged to the same conveyors from the respective bins and charging rate is controlled according to the concentrate feed rate to the S furnace and concentrate composition based on metallurgical calculation.
A flux-reverts-concentrates mixture is transported by pneumatic conveying air into a 2 inch inner pipe which is encircled by a larger 4 inch diameter lance pipe. Oxygen enriched air is introduced into the annular region between pipes. The inner pipe ends at a short distance above the furnace roof and the final high velocity air-oxygen concentrate mixture is introduced into the furnace through a rotating lance and impinges on the molten bath. The S furnace is refractory lined and circular in shape (10.0 mX inside). A tap hole for matte and slag mixture overflowing and uptake is installed on the side wall and roof respectively. Refractory of upper part of side wall and roof are equipped with water cooled copper jacket. 9 lances are installed on the roof. Feed materials are smelted and from matte of 65% Cu and slag. Slag and matte mixture overflows from the furnace and flows via a natural gas heated launder to the CL furnace. The 3,600 KVA CL furnace is elliptical in cross and is heated by two sets of delta (A) type electrode allocation, 16 inch + graphite electrodes. Matte and slag are separated by difference of specific gravity. Slag overflows from CL furnace and is water granulated. Molten matte is constantly siphoned out to the C furnace.
The C furnace is circular in shape (9 mX inside) and 10 lances are equipped, which feed a Limestone-coolant-oxygen enriched air mixture to the furnace bath. Anode scraps from refinery are fed to the C furnace. Matte is oxidized and blister copper is produced. Blister copper is siphoned out from the C furnace continuously and led to the anode furnace through launders. Formed C slag, overflows from the furnace and is water-granulated. Granulated C slag returned to the S furnace after drying and some amount of C slag is fed to C furnace as coolant. Schematic Flow sheet is shown in Fig 4.1 and Major Operation Parameters are shown in Table 4.1. (Valenzuela, A,2003);(P.L.Couterier,1997).
Figure 4.1 Schematic Flow sheet of the conventional copper concentrate process
Table 4.1 Major Operation Parameters
Conventional Electro Refining Process
Electro refining of copper consists of electrolytically dissolving copper from impure anodes of about 99.7% copper, and selectively plating the dissolved copper in pure form onto the copper cathode. This reaction takes place in a cell containing an electrolyte which is basically copper sulphate and sulphuric acid. Metallic impurities more noble (electro positive) than copper do not tend to enter the electrolyte at the current densities employed, but settle in the bottom of the cell as anode slime.
Metals which do enter the electrolyte with copper are either precipitated as insoluble compounds, or, being less noble than copper remaining in the solution and do not deposit electrolytically at the cathode.
Electrolytic refining is carried out in a multiple system of cells in series to form practical sections. The electrodes, anode copper and cathodes are connected in parallel in the cells.
The conventional electro refining practice is to use starter sheets of higher purity copper, as the cathode substrate upon which the copper is electro deposited. These starter sheets are produced in special electrolytic cells by a 24 hour electro deposition of copper, onto either hard rolled copper or titanium blanks. Preparation of the starter sheet included washing, straightening and stiffening of the sheet. The sheets are then suspended from rolled copper hanger bars by attached loops of copper strips.
The electrolytic cells are loaded with anodes and starting sheet prior to the electric current being connected. The starter sheets are generally plated with copper for 12 – 14 days before they are removed and a second starter sheet inserted between the anodes. The anode cycle is generally between 24 – 28 days. At the end of the cathode cycle the anode scrap is removed, washed and returned to the casting facility for melting and recasting into anodes. The cells are drained of electrolyte and the anodes slimes containing the precious metal is washed from the bottom of the cells, collected and further processed. Conventional Electro refining Process is shown in Figure 4.2(Wayne, 1999); (Valenzuela, A,2003);(P.L.Couterier,1997).
Figure 4.2 Conventional Electro refining Process
Last update: February 21, 2012
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