A review of copper-cobalt ore smelting process with magnesium oxide from Congo (gold)

The pyro-and hydrometallurgical processes commonly used by several representative copper and cobalt smelting enterprises in Katanga Province are introduced and reviewed. Of these, state-owned enterprises produce end products such as electrical copper and cobalt, while chinese-owned enterprises in the country generally produce intermediate or semi-finished products. Due to the lack of copper and cobalt smelting chemical reagents and raw materials, the import of magnesium oxide and other related reagents and materials raises the enterprise production costs.

Congo is extremely rich in minerals and water resources, Non-ferrous metal and rare metals, and mining is an important pillar of its economy. High-grade copper and cobalt deposits are buried in the country, which is the world’s largest producer of the metal. Local enterprises usually use pyrotechnics and hydrometallurgy to treat copper and cobalt ore. Several representative copper and cobalt ore smelting enterprises in Katanga Province have been investigated. The provincial city of Likasi in the south-east of Congo (Democratic Republic of the Congo) , near Zambia. The local copper-cobalt ore resources are very rich, there are copper-cobalt ore and copper-cobalt sulphide ore, because the copper-cobalt sulphide ore smelting process has not been investigated, this article only introduces the copper-cobalt ore smelting process. However, according to the data introduced, copper and cobalt sulphide ore smelting using fluidized oxidation roasting process, roasting flue gas acid, slag copper and cobalt ore smelting process line.

Congo (DRC) except a few large and medium-sized enterprises have mines, most of the small and medium-sized smelters do not have mines, copper and cobalt ore raw materials from the company set up acquisition station. The copper oxide ore acquired (copper high and cobalt low, copper priced, cobalt not priced) ranges in copper grade from 8% to 40% and 6% to 45% , respectively, cobalt oxide ore (cobalt high, cobalt price, copper price is not) cobalt grade range is 2% ~ 20% .

1 introduction of smelting process

1.1

Company A is a state-owned enterprise (containing mines) in the Democratic Republic of the Congo (DRC) , which began production of copper in 1929 and cobalt in 1940. At present, the raw copper and cobalt ore (containing 2.5% copper and 0.1% ~ 1% cobalt) and concentrate (containing 20% ~ 25% copper and 2% ~ 2.5% cobalt) are treated by WET process. Electro-copper production process: raw copper and cobalt oxide ore and concentrate are mixed in proportion, the mixed concentrate is ground by sulfuric acid reduction step-by-step leaching of copper and cobalt, the leaching temperature is 60-80 ° C, the leaching time is 2H, the leaching time is 6h; A reductant is added to the sodium metabisulfite to reduce the trivalent cobalt to the bivalent cobalt. The leaching solution is filtered several times (mainly by sand filtration) followed by the addition of copper particles to precipitate selenium. The copper is sent to the copper electrowinning workshop to produce electric copper. Electrocobalt production process: after the copper electrowinning solution using sulfide, neutralization, hydrolysis to remove copper, iron, nickel and other impurities, clarification process widely used flocculant, de-impurity solution sent to the Cobalt Workshop to produce electrocobalt, electrocobalt is melted and water quenched to obtain cobalt particles.

The total recovery of copper and cobalt is 80% and 60% respectively. Copper smelting consumes 3.5 t/t copper sulphate, cobalt smelting consumes 8.5 t/T Cobalt sulphate and 10 t/T cobalt lime. The annual output of copper is about 10kt and cobalt is about 500t. All the reagents used are imported from South Africa except sulfuric acid (sulphuric acid from sulphur, the same below) and lime milk.

1.2

B enterprise is a chinese-funded enterprise, there are two production systems using pyrotechnic process and wet process from around the acquisition of copper and cobalt ore, copper grade less than 15% of copper oxide into the wet system, cobalt oxide ore firing system with cobalt grade less than 1% .

The pyrotechnic process produces crude copper and copper-cobalt alloy by reduction smelting in electric furnace. The copper and cobalt ore is mixed with the flux limestone and the reducing agent coke and added into the electric furnace. When the melting temperature is 1200 ° C, the coarse copper containing more than 92% copper is produced and cast into the coarse copper block The copper-cobalt alloy is produced by the reduction smelting of the molten slag with coke in another electric furnace at a melting temperature of 1400 ° C (copper + cobalt ≥40%) . The metallurgical principle is to control the amount of reducing agent coke and melting temperature to achieve step reduction, first in the first electric furnace reduction of copper, and then in the second electric furnace reduction of copper and cobalt. The annual production of crude copper and copper-cobalt alloy is about 10kt and 2KT respectively, and the products are exported to China.

Wet Process: copper and cobalt ore ball mill to 100 mesh, the use of sulfuric acid and Iron(II) sulfide step leaching of copper and cobalt, leaching solution combined with extraction electrowinning to produce electric copper, regular extraction of residual liquid, after neutralization and preliminary impurity removal, crude cobalt(II) hydroxide is prepared. The copper is sold locally and the crude cobalt(II) hydroxide is sold in China. The factory produces its own sulphuric acid, except lime, the other chemical reagents are purchased from China.

1.3, C Enterprise

C enterprise is a chinese-funded enterprise, with electric furnace reduction smelting copper and cobalt ore, copper and cobalt alloy production. About 100 tons of copper-cobalt ore and 11-13 tons of copper-cobalt alloy are produced per day. In this process, limestone is used to make slag, and pulverized coal is used to reduce the slag. The alloy temperature is 1250 ° C, and the slag temperature is 1500 ~ 1600 ° C. In rainy season, the concentrate has high moisture content and needs to be dried in an internal heating rotary kiln. The concentrate, limestone and coal are lifted from the grab bucket to the hopper and unloaded to the belts, which are respectively conveyed to the 4 hoppers on the top of the furnace Buried scraper in the material and then into the top of the furnace 2 buried scraper, each buried scraper has a number of feeding mouth. The furnace top has the material level bar to measure the slag level and the alloy level. Slag and copper-cobalt alloy are discharged by water quenching. Copper-cobalt alloy sold to China, slag discarded.

C enterprise procurement of local copper and cobalt ore, the general requirements of cobalt > 4% , slag cobalt, slag copper average 0.2% ~ 0.4% , cu-co alloy contains 30% ~ 40% Cu + CO, 3% ~ 7% Ni, 30% ~ 40% Fe and 5% ~ 10% sio.

1.4, D Enterprise

D enterprise is a chinese-funded enterprise, which adopts wet process to treat copper and cobalt ore (containing 5% ~ 10% copper and 2% ~ 5% cobalt) . The ore is ball-milled to a 100-mesh leaching tank, heated, iron(2+) sulfate (anhydrous) with sulfuric acid and a reducing agent (made on-site by adding sulfuric acid and iron powder to the residual solution) and leached, the copper and cobalt sulfate slurry was concentrated and separated by calcium carbonate slurry after neutralization and acid adjustment to obtain bottom flow and clear liquor. After the solid-liquid separation, the leached residue is produced and washed out, and the filtrate is clarified and secondary extraction is carried out. Under the condition of heating, the clear liquid is neutralized and precipitated once and twice by the neutralizer magnesium oxide, and then precipitated once by the neutralizer magnesium oxide, the crude cobalt(II) hydroxide is produced as the final product, which is discharged or partially reused after neutralization and treatment. The design of the electrowinning workshop is simple and simple. The plastic balls are placed in the electrowinning tank to separate the acid fog, and the loading tank is lifted out by a simple crane on the ground. The electrowinning copper is soaked in the 90 ° C Bath and then removed by manual stripping. The company produces its own sulfuric acid and produces about 10kt of copper per year. The total recovery of copper and cobalt is 95% and 88% respectively.

1.5

E Company is a chinese-funded enterprise, the copper and cobalt ore treated by the high copper (> 10%) , low cobalt. First the ore ball mill to 100 mesh, with sulfuric acid leaching of copper and cobalt, leaching solution directly to electrowinning product copper, electrowinning solution back

Copper and cobalt ore is leached back, and the rich copper liquid obtained by leaching residue washing water extraction and stripping is sent to electrowinning bath to produce electric copper. No reducing agent was added and no heating was applied in the leaching process. The concentration of cobalt in the leaching process was low, and finally cobalt carbonate was obtained by neutralization of cobalt in the effluent. The annual output of the company is about 3KT electrodeposited copper and a small amount of cobalt carbonate.

Review of smelting process

1) the process of copper and cobalt smelting in Enterprise A is mainly leaching + impurity removal + electrowinning, while the impurity removal of leaching solution is mostly neutralization and sulfidation, and the filtration of solid-liquid separation is basically sand filtration. The recovery of copper and cobalt smelting is low and the consumption of reagents such as sulfuric acid is high due to the lengthy process and obsolete equipment. At present, the copper and cobalt leachate in copper and cobalt smelting enterprises is basically purified and enriched by the extraction and back extraction process with high efficiency. The cobalt in the residual solution can also be purified and enriched by the extraction and back extraction process.

2) Enterprise B adopts pyrotechnic process to treat copper and cobalt ore with high copper and low cobalt content, cheap hydropower in Congo supports electric furnace smelting, and adopts wet process to treat copper and cobalt ore with low copper and high cobalt content.

3) the copper-cobalt ore in C enterprise has low copper-cobalt content and is treated by pyrotechnic process.

4) the copper and cobalt content in copper and cobalt ore of D Enterprise is lower, which is treated by wet process, and the process is long, complete and classical. The first step is to pre-leach copper, and then to leach cobalt with a self-made iron(2+) sulfate (anhydrous) , and the leached copper and cobalt slurry is heated when calcium carbonate slurry is added, the second extraction is carried out: the Copper-rich liquid from the first extraction and stripping is electrodeposited to produce copper, and the second extraction is carried out on the first extraction residual liquid and the bottom flow of leaching after stirring and washing, and the cobalt is enriched in the second extraction residual liquid, and the second extraction residual liquid is added with magnesium oxide to neutralize the cobalt cobalt(II) hydroxide. Magnesium oxide is expensive, but the addition of magnesium oxide is characterized by its high neutralization and consumption of acid equivalent, the absence of magnesium precipitation when cobalt is deposited, the reduction of impurities in the cobalt(II) hydroxide and the convenience of subsequent purification processes for the crude cobalt(II) hydroxide, the use of calcium carbonate (limestone) as the neutralizer in the slurry, and the return of washing water and slurry mostly to the pre-processing process, etc. .

5) e enterprise is a chinese-funded enterprise, because the copper and cobalt ore treated has high copper content and low cobalt content, so wet process is adopted to treat the copper and cobalt ore. By controlling a certain liquid-solid ratio, the leaching solution with higher copper sulfate concentration can be obtained, and the copper can be directly electrodeposited to produce electric copper with 99.9% copper content. Because of the low cobalt content in copper and cobalt ore, the main process only considers the recovery of copper, and adopts a simple design, instead of reducing and heating leaching, it adopts normal temperature stirring leaching, thus saving the extraction process and reducing the production cost.

3 conclusion

1) there are two kinds of copper-cobalt ore smelting processes, namely pyrotechnic process and wet process. The pyrotechnic process is electric furnace reduction smelting to produce crude copper and copper-cobalt alloy, or only copper-cobalt alloy. Copper-cobalt ores with high copper content and low cobalt content produce crude copper and copper-cobalt alloys, and if copper and cobalt are not high, copper-cobalt alloys are produced directly. The wet process is the reduction leaching of copper and cobalt from copper-cobalt ore, and the leaching process depends on the concentration of copper

If the concentration of copper is high, the leaching solution is directly sent to the electrowinning workshop to produce electrowinning copper. After electrowinning, the leaching solution oxidizes and neutralizes the precipitated iron and sodium carbonate to precipitate copper to produce malachite, and sodium carbonate neutralizes the precipitated cobalt to produce cobalt carbonate If the concentration of copper is low, the leaching solution is sent to the extraction shop to enrich the copper and then to the electrowinning shop to produce the electric copper. The cobalt is not extracted and is neutralized in the extraction residue to recover the cobalt in the form of crude cobalt(II) hydroxide or cobalt carbonate.

2) state-owned enterprises in the Democratic Republic of the Congo produce final products such as electrical copper and cobalt, while chinese-owned enterprises generally produce intermediate or semi-finished products to minimize investment and production costs.

3) the chemical reagents and raw materials needed for smelting copper and cobalt ore in Congo (gold) are lacking, and the enterprises generally produce sulfuric acid, magnesium oxide, extractant and sodium carbonate all have to be imported from abroad, which raises the production cost.

High reactive magnesium oxide
High reactive magnesium oxide

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