Leaching-extraction-electrowinning process example

Extraction method to master the main rare metal used for extraction. Due to the high price of the extractant, the application of the copper extraction process is limited. Since the 1970s, the rapid development of the organic chemistry and petrochemical industries has provided conditions for the manufacture and use of new and inexpensive, effective extractants, making it possible to use extraction methods in the industrial production of copper. The remarkable characteristics of solvent extraction are high production efficiency, continuous workability, suitable for industrial scale production, good separation effect, high extraction rate, easy operation, and less “three wastes” during production. Therefore, in recent years, the industrial production of copper extracted by extraction in foreign countries has increased year by year. In 1968, the Lanwu Mine of Arizona's Rancho Exploration and Development Company first built the world's first copper extraction-electrotome plant. There are more than a dozen solvent extractions of copper in the world (Table 1). The extractants used in these plants are almost all Lix-64N.

Table 1 Foreign Copper Leaching-Extraction-Electrical Power Plant

Due to the strict requirements of environmental protection and the widespread exploitation of oxidized ore in foreign countries, the solvent extraction of copper has received extensive attention and attention. The leaching-extraction-electrowinning method is easy to handle low-grade oxidized ore and mixed ore. As the demand for copper increases, it will lead to the exploitation of low-grade ore. In addition, in order to control the environmental pollution of sulphur dioxide, it will provide more for the extraction method. Wide application prospects.

Zambian Enchangjia United Copper Co., Ltd., an acid leaching-extraction-electrochemical plant with an annual output of 90,000 tons of copper in Jingola, mainly dealing with low-grade copper oxide ore and flotation tailings, using three-stage extraction and two The stage back-extraction process, the extraction ratio is 1:1, about 60~70% of the extract residue is returned to the acid leaching system, and the copper loss is small. The extractant Lix-64N is an aromatic oxindole 12-hydroxy-5-dodecyl-benzophene ruthenium, a Lix extractant, which is a chelating extractant containing oxindole (USA) developed by General Minerals Co., Ltd. It has good extraction properties for copper and nickel .

In addition to the isolation-flotation process, the copper oxide ore in China basically adopts the flotation flotation process. At present, the acid leaching-extraction-electrowinning method is in the industrial test stage in large and medium-sized plants, and some local small factories have Used in production.

I. Shuangfeng Copper Concentrator (USA)

(1) Overview

The Twin Buttes copper mine is located approximately 32 kilometers south of Tucson, Arizona, USA. Anaconda started construction of the mine in 1965. In November 1969, it built a sulphuric ore dressing plant with a daily processing capacity of 30,000 tons. In 1970, the molybdenum plant was put into operation. After the formation of the Annamax Mining Company in 1973, the company expanded its double peak and built a new water and metallurgical plant to treat oxidized ore, with an annual output of 36,000 tons of electrolytic copper. The fourth series of expansion of the sulfide ore system will produce 126,000 tons of copper per year after the completion of all the projects. Among them, the sulphide ore dressing plant produces 90,000 tons, and the oxidized ore plant produces 36,000 tons.

(2) Mineral deposits and ore properties

Bimodal copper ore mainly native, mainly chalcopyrite, and bornite and other secondary sulfides, and a large number of associated pyrite. The surrounding rocks are mainly limestone , strontium limestone, contact metamorphic carbonate and quartz monzonite, and the oxidation depth is generally above 30~60 meters. The ore body is buried deep, the upper part is covered with hard gravel of 8~15 meters thick, and the upper part is the fourth magic surface soil of 120~180 meters thick.

(3) Acid leaching-extraction-electrowinning process

Crushing the oxide ores, after grinding, leaching with sulfuric acid leaching solution with an organic phase (extractant is typically a mixture of coal and oil Lix64N) extraction of copper, so that very low concentrations of copper into the organic phase, the anti-extraction with sulfuric acid The copper-containing organic phase is sent to the electrolysis workshop for electrolysis to obtain a cathode copper of 50 g/liter of the stripping solution. The process is shown in Figure 1.

Figure 1 US bimodal copper oxide leaching - extraction - electrowinning plant process

The Shuangfeng plant has two parts: one is a 36,000-tonne sulfide ore dressing plant for processing raw ore; the other is a copper oxide ore processing plant, which was put into operation in 1975 and is the world's largest leaching-extraction-electrochemical plant. According to the design, it treats 10,000 tons of oxidized ore per day, with an average of 1.35% copper, containing 1.02% acid-soluble copper, 100 tons of cathode copper per day, and 30,000 tons of cathode copper (purity of 99.995%) in 1976, processing ore 290. Ten thousand tons, with an average copper content of 1.3%, reached a design capacity of 36,000 tons of copper in 1977.

The original mine was loaded with 2.67 m ³ electric shovel from the mine to the 50 or 100 ton ore truck, and the ore was transported to the crushing plant, using a jaw crusher of 1.22×1.52 m, crushed to less than 200 mm, and then used. A 2100 mm standard cone crusher was broken and the product entered a closed circuit consisting of two 2100 mm short head crushers and two 2.44 x 6.09 m double screens. The final crushed product has a particle size of 13 mm and the powder mine has an effective volume of 15,000 tons.

There are two parallel series of grinding. Each series consists of a ф3.5×5.64 m rod mill and a 3.81×6.14 m ball mill . The open-mill grinding product has a particle size of -48 mesh and 95%. The pulp concentration is 60%. The reason for using open-circuit grinding is that it can obtain higher leaching ore concentration than closed-circuit grinding operations. The grinding capacity is 440 tons / hour.

Acid leaching

The ground product has a solids concentration of 60% and is divided into two streams by a distribution tank, one for leaching and the other for pH adjustment.

The leaching was carried out in five mechanically agitated dip tanks arranged in series, rubber-lined, 9.14 m in diameter and 9.45 m high. The concentration of 93.2% sulfuric acid was added from the acid storage tank to the first leaching tank. There are four storage tanks with sulfuric acid, the total volume is 21,000 tons, the sulfuric acid consumption is 113 kg/ton (concentration is 93-98% sulfuric acid), the ore leaching time is five hours, and the leaching pH is 1.5.

After the leaching, the slurry concentration was 50%, and it was sent to four concentrators with a diameter of 122 meters, and the waste liquid from the extraction plant was returned for countercurrent washing. The solids flow from the No. 1 concentrator to the No. 4 concentrator and finally to the tailings dam. The waste liquid of the extraction plant is reversed, flowing from the No. 4 concentrator to the No. 1 concentrator, and overflowing as a mother liquid to the pH adjustment tank. To adapt to the solvent extraction, the mother liquor is overflowed to the No. 1 concentrator, and the unreacted grinding slurry is added. , adjust the pH from 1.5 to 2.5. The residence time of the slurry in three mechanically agitated pH adjustment tanks was 45 minutes.

The concentration of the slurry from the pH adjustment tank is about 10% solid. It is purified by the second-stage concentrator. According to the design, the overflow of the first 122-meter-diameter purification concentrator contains 30~80ppm of solid. The sink of these two concentrators The sand is returned to the agitation leaching tank, and the liquid overflowing from the second purification concentrator is called a copper-containing mother liquor. After clarification, the tank is adjusted, steamed to 20 ° C, and then passed to a filter press.

Solvent extraction

After filtration, the mother liquor contained 2.5 g/L of copper and the total flow rate was 26.6 ^m3 /min. The extraction was carried out in parallel in two rows with four extractions per system. The organic extractant Lix64N was dissolved in kerosene at a volume percentage of 12%. After the extraction, the residual aqueous phase contained about 0.08 g/liter of copper, and returned to the leaching operation. The copper-loaded organic phase contained about 25 g/liter of Cu. The two parallel systems were subjected to two-stage back extraction with sulfuric acid, and the copper backed extract contained 50 g/L of copper.

Electrowinning

The copper stripping extract contains 50 g/L of copper and is sent to electrolysis to obtain a cathode copper having a purity of about 99.995%.

In general, 25 grams of copper can be extracted per liter of extractive mixture, and the extraction rate is over 95%.

Second, Pu Dahuier Copper Mine Plant (Chile)

(1) Overview

Pudahuel Minerals is located 30 kilometers west of Santiago, Chile, with the Santiago-Valparaiso highway passing through mines and mining areas. The mine has a maximum temperature of only 35 ° C, a minimum of -4 ° C and an annual rainfall of 300 mm. Valparaiso, 100 km northwest, is the main port of Chile.

At the end of 1980, Puda Wheeler Minerals Co., Ltd. (SMP) had a new project for the injection of $70 million in copper, including an open pit mine, thin layer leaching (TL), solvent extraction (SX) and electrolysis (EW). ).

After SMP obtained the ownership of the copper mine, McGee was hired to conduct a feasibility study in 1970, which considered that it could obtain high benefits. Later, Hazen Research Company revised the original process and developed a new metallurgical solution. The use of leaching, solvent extraction and electrolysis is a satisfactory and very economical process. SMP, Holles and Narfer reached an agreement to sign contracts for design, operation, construction management and commissioning. The daily processing capacity is 2,500 tons.

In the middle of 1979, the preliminary design was completed, civil engineering began in February 1979, and the stripping of the mine was underway. The mine needs to initially strip 2 million tons of topsoil, and the stripping ratio will remain around 3.26:1 within 12 years of production. The ore is transported by road, about 15 kilometers away, and the road slope is up to 8%.

(2) Mineral deposits and ore properties

The Roaguyray mine is irregular in shape and is about 600 meters long, 200 meters wide and 150 meters thick. The ore outcrop is in the south. The upper part of the ore body is oxidized, mainly fine-grained malachite. Deep is a sulfide zone, mainly copper and copper, copper blue, a small amount of pyrite and chalcopyrite. The middle zone is a mixed copper oxide ore and copper sulfide ore. The mineral structure is dense and hard.

The final size of the crushed ore is 6 mm and then sent to hydrometallurgy. The process is shown in Figure 2.

Figure 2 Puda Whale copper leaching-extraction-electrowinning process

(3) Thin layer leaching

The "TL" leaching process is suitable for the treatment of certain copper deposits, especially small and medium sized oxidized ores. Leaching is the mixing of finely divided ore with concentrated sulfuric acid and then sent to an acidified reactor where it is acidified into a thin layer and leached with water or weak acid.

The stages of the process are: 1 crushing the ore to 6 mm; 2 ore and acid agitation; 3 ore after acidification for a few hours and then stacking the ore into a 2 m high layer; 4 spraying with SX raffinate ; 5 natural discharge of mineral rich liquid; 6 stacking and processing tailings; 7 using SX-EW operation to enrich and recover copper.

The semi-industrial tests conducted for the Roaguyray project show that the copper recovery in oxidized ore is 90-95%, and the copper recovery in sulphide ore is 40-60%.

In the Roaguylei deposit, there are malachite and chrysocolla in the oxidized ore, and chalcopyrite and porphyrite in the sulphide ore. The dissolution of the sulfide minerals is slow in each operation. After the copper ore is freed from 50% of its copper content, it is first converted into copper blue, and then the copper blue is decomposed by the solution. The copper ore is converted to a chalcopyrite, followed by a chalcopyrite. The chalcopyrite is virtually unchanged, and the chalcopyrite continues to dissolve as 40% of the copper in the bauxite is released.

The treated ore is transported to 4 acidified reactors for 24 hours, during which time the oxide is intermittently converted to crystalline copper sulfate by acid. In this operation, about 60 to 70% of the oxides are converted.

Each leaching station processes about 1,700 tons of ore, and the leaching period is 12 days. The leached residue is transported to the tailings pile by belt.

The length of the leaching cycle is related to the amount of sulfide in the ore and the consumption of sulfuric acid in the electrochemical reaction (1.5 kg of acid per kilogram of precipitate). As a result of the acidification, the copper oxide is quickly extracted within a few hours, and the dissolution of a solution containing a total amount of total iron (about 30 g/liter) and iron trioxide (7-8 g/liter) is the key to decomposing the sulfide. During the leaching process, the resulting rich liquid has a pH of about 2.

(4) Extraction process

For the Roaguyray ore, secondary extraction and secondary stripping will be used. The extractant is Lix-64N (Henkel patented pharmaceutical), which has been used in several factories around the world for many years.

The leaching-extraction-electrowinning (TL-SX-EW) process has a low acid consumption of about 2 kg of acid per kg of copper. Due to acid recycling, the acid consumption of the electrolytic cell is low.

The extract of the leachate was diluted with kerosene using a selective hydrazine (Lix type).

The plant itself has five mixing-precipitation tanks, three for extraction and two for stripping. The equipment is made of stainless steel-coated concrete with a length of 29 meters, a width of 12 meters and a height of 1.2 meters. The shape of the mixing groove is elongated, replacing the conventional cylindrical or cubic shape.

The storage tank, feed pump and connecting pipe are made of stainless steel, and the mixing-sinking tank has a complete automatic system. The leachate or raffinate (10.5 g/l copper and 3 g/l acid) was sent to the electrolysis plant.

(5) Electrolysis

The plant has 64 electrolyzers, each with 64 lead -calcium alloy anodes. The cell has a current density of 240 amps/ ^m2 and an energy consumption of 1.95 to 1.99 kWh/kg of precipitated copper. There are three 2,500 kW rectifiers that supply the electricity needed for electrolysis, and the other ancillary facilities are 5 ton cranes. The planned production capacity of the electrolysis plant is 47.5 tons of cathode copper per day, with a total annual output of 17,000 tons.

(6) Working system

The mine works 6 days a week, 2 shifts a day, 8 hours per shift, and slightly more than 3,000 tons per day (reserved 250,000 tons). The leaching factory operates three shifts, working seven days a week, with a production capacity of 2,500 tons / day.