1. Development status of domestic and foreign copper hydrometallurgy technology
Since 1968, about 50 leaching-solvent extraction-electrowinning plants have been designed, constructed and operated in the world, including 16 in the United States. In 2000, copper output reached 557,500 tons, accounting for 28% of its refined copper output. The largest MOrenci plant in Arizona currently has an annual output of 258,300 tons. In 1980, Chile produced only 15,000 tons of copper by solvent extraction-electrowinning. In 2000, it has developed into the world’s largest copper producer. There are 21 production plants with an annual output of 1,347,300 tons of copper, accounting for the total amount of copper refined. 51%. The wet copper leaching technology in Zambia, Peru, Australia, etc. has also developed rapidly in recent years.
Now the solvent extraction-electrowinning process has been considered by the industry as a mature, low-cost, low-risk technology. The copper output produced by this process reached 2.4 million tons in 2000, accounting for more than 20% of the world's copper output. By 2003 The output of wet copper has accounted for 1/4 of the world's copper output.
Since the production and application of this process in the 1960s, some research units in my country have carried out research on leaching (acid leaching, ammonia leaching, bacterial leaching, or biometallurgy), extraction technology, and extractant. After the 1980s, a relatively complete leaching-extraction-electrowinning process was formed and was initially applied in production. Since the 1990s, with the rapid development of international copper hydrometallurgical technology research and application, coupled with the domestic copper production and market being increasingly severely impacted by foreign countries, the research on new copper hydrometallurgical processes has been included in the national 'Ninth Five-Year Plan'. 'The key scientific and technological research plan has strongly promoted and accelerated the research and promotion of my country's copper hydrometallurgical technology. At present, there is a large-scale developmental production of Dexing Copper Mine waste rock (average copper content of 0.09%) bacterial leaching-extraction-electrowinning pilot plant (annual copper production 2000 tons). Zijin Mining Company's copper sulfide ore bacterial leaching-extraction-electrowinning test plant (annual copper production 1000t). Zhongtiaoshan Copper Mine Yu in-situ acid leaching-extraction-electrowinning test plant (annual copper output 500 tons). Although the hydrometallurgical technology has developed greatly in recent years, there is still a big gap compared with foreign countries, mainly due to the gap in the basic theory of leaching and industrialization technology, and the established industrial production plants are small in scale and low in output.
2. Copper hydrometallurgy principle, process and suitability of ore
(1) my country's copper resources and production profile
my country's copper mineral resources are relatively scarce, with low grades and poor quality; there are few large-scale mines, but many medium- and small-scale mines; many lean mines but few rich mines; many complex polymetallic mines but few single mines; many underground mines but few open-pit mines. These characteristics make mining and beneficiation more difficult, especially for beneficiation. Due to the low grade of the original ore and the complex mineral composition, the cost of beneficiation is high, and the grade of the concentrate is generally low, which makes subsequent smelting difficult. As far as pyrometallurgy is concerned, although the process and equipment have been greatly improved, the production cost is generally higher than that of foreign countries, and there is still serious environmental pollution.
The advantages of copper hydrometallurgy are low investment and low production cost. According to reports, the investment per ton of copper produced by the fire method is about 65,000 yuan, while the investment per ton of copper for the leaching-extraction-electrowinning process is about 15,000 yuan. In fact, from the actual situation in my country, the production cost per ton of copper in Dexing Experimental Plant is RMB 10,450.23, Zhongtiaoshan is RMB 8,000, and Zijin Copper Mine is RMB 10,000. If the scale of production is further expanded, production costs will fall.
(2) Principles of Copper Hydrometallurgy
1. The leaching principle of copper oxide ore
Common copper oxide minerals are mainly malachite, chrysocolla, cuprite, and natural copper. Under the action of leaching agents H2SO4 and Fe2(SO4)3, as long as the content of high alkaline gangue in the ore is not high, generally better leaching results can be obtained. The chemical reaction in the leaching process is:
2. The leaching principle of copper sulfide ore
For copper sulfide ore, biological oxidation copper leaching is currently one of the most studied, fastest-growing, and best-prospective technologies.
The main microorganisms currently used for bioleaching are Thiobacillus ferrooxidans and Thiobacillus thiooxidans. They can survive in extreme environments with high acid and heavy metal concentrations below 35°C. There are generally two mechanisms of bacterial oxidative leaching: bacteria adsorb to the surface of minerals and directly interact with minerals to dissolve minerals. The direct mechanism of action: Fe2+ released from mineral dissolution is oxidized by bacteria into Fe3+ in solution, and Fe3+ acts as an oxidizer to oxidize sulfide ore. The indirect or chemical mechanism of action.
(1) Bacterial leaching of chalcocite
Chalcocite can be oxidized to FeSO4 and S in the presence of acid and Fe3+. The reaction is as follows:
The produced FeSO4 and S are then oxidized by bacteria to Fe2(SO4)3 and H2SO4 so that the reaction cycle proceeds.
On the other hand, under the action of bacteria, chalcocite is oxidized and dissolved by oxygen
The leaching of chalcocite is believed to be dominated by indirect oxidation of Fe3+, and bacteria are the indirect oxidants of the leaching reaction.
(2) Bacterial leaching of copper blue
Since there are no Fe3+ and other oxidants in the leaching environment, the leaching can only be caused by bacteria. During the leaching, the acid consumption is equal to zero. The reaction is:
Bacterial leaching has occurred in the entire mineral, and the chemical composition indicated by the mineral has not changed after leaching, indicating that there is no intermediate process of conversion to other sulfides during leaching, and no element S is produced.
(3) Bacterial leaching reaction of sulphur-arsenic copper ore
In the presence of H2O and O2, under the action of Thiobacillus ferrooxidans, Thiobacillus thiooxidans and composite bacteria, direct leaching reaction of sulphur-arsenic copper ore occurs:
(4) Bacterial leaching reaction of chalcopyrite and bornite
Directly with Fe2(SO)3 in the presence of bacteria. The following reaction occurs
2Cu5FeS2+2 Fe2(SO4)2+17O2-10 CuSO2+4 FeSO4+2 FeO
Among them, FeSO4 and FeO are converted into Fe2(SO4)3 under the action of acid and bacteria for cyclic reaction.
(3) Types of copper ore suitable for hydrometallurgical processing
For copper oxide ore, as long as the ore particle size is well controlled, a satisfactory leaching effect can generally be obtained. However, the leaching effect of copper sulfide ore varies greatly according to its mineral type. At present, the copper ore treated by biological oxidation process in foreign countries is basically secondary copper sulfide ore (chalcocite, azurite, copper blue, etc.), while pyrotechnic technology is still used for primary copper sulfide ore. deal with.
In addition, in terms of ore types, the current leaching-extraction-electrowinning technology is mainly used in porphyry copper ore. This is mainly because the porphyry copper ore is large in scale and contains less alkaline gangue, which is the most ideal raw material for sulfuric acid leaching. Such as the domestic Dexing Copper Mine, Zijinshan Copper Mine, Zhongtiaoshan Copper Mine Yu Mine, and Dabaoshan Copper Mine. my country’s copper resources are characterized by a large number of skarn-type copper mines, accounting for more than 50%, and reserves accounting for 29% of the total reserves, while Western countries only account for 3%. Such deposits are generally small in scale, scattered and ore bodies. The storage conditions are more complicated, most of which are suitable for underground mining, and the mining costs are relatively high. In addition, it contains more alkaline gangue, which is not conducive to leaching with sulfuric acid.
3. Application of hydrometallurgical process in domestic copper mines
Domestic production test plants that adopt hydrometallurgical processes mainly include Dexing Copper Mine, Zijinshan Copper Mine, Zhongtiaoshan Copper Mine Yu Mine, etc. Now we will give a brief introduction to their experimental production conditions, processes, and technical indicators.
(1) Copper (waste stone) recovery process and indicators in Dexing Copper Mine
Dexing Copper Mine Heap Leaching Test Plant uses waste rock (containing 0.1% to 25% Cu) stripped from open-pit mining as raw materials. Calculated based on the critical grade of 0.25%, the total amount of waste rock is 890 million tons, of which the copper content reaches 951,500 tons. It is difficult to economically recover copper with traditional beneficiation and smelting processes. With the approval of the State Planning Commission and the Ministry of Science and Technology, a pilot plant with an annual output of 2,000 tons of copper was built in May 1994, and was listed as a national scientific research project during the Ninth Five-Year Plan. Because the ore grade is low and most (over 85%) are primary sulfide ore, it is the most difficult to leach ore, which is typical in my country's copper industry. The problems encountered and the characteristics of the process flow are also representative.
The pilot plant produces 1,000 to 2,000 tons of copper per year, with a grade of raw ore copper of 0.121%, a leaching rate of 16.59%, and a product quality of Grade A. The cost of a ton of copper is 10450 yuan. The mine is the only domestic manufacturer that uses the bacterial leaching process to process primary copper sulfide ore. Through the heap leaching-extraction-electrowinning process, not only part of the copper is recovered from the stripped waste rock, but also certain benefits are created and resource waste is reduced. , And the acidic mine water produced in the mining process is no longer discharged outside, reducing environmental pollution. Since it was put into production in October 1997, the process has been basically stable. The main problem is that the copper leaching rate of the entire ore pile is not high, and the Cu2+ mass concentration in the leaching solution needs to be more than 1 g/L, but until now, the Cu2+ needle concentration in the leaching solution has been lower than 0.6 g/L during the entire production process. L.
(2) Copper recovery technology and indicators of Zijin Mining Company
The Zijinshan Mine is a large-scale proven gold-bearing copper mine, characterized by upper gold and lower copper, with large reserves and low grades. The industrial reserves of copper metal are 1.2564 million tons. The average ore grades are Cu 0.68%, S 2.58%, and As 0.035%. The main target minerals are blue chalcocite and copper blue, followed by chalcocite, massive sulphur arsenic and sulfur Arsenic. Due to the low grade of raw ore and high arsenic content, the traditional flotation-fire smelting process is adopted, which requires large investment, high cost and heavy pollution. Zijinshan copper ore is dominated by secondary copper sulfide, which has relatively mature biological leaching technology. Using this process to treat Zijin copper ore has good economic benefits.
The original ore is crushed to -30mm, and the automatic unloading method is adopted for the post-moving stacking method, and the pile height is 8-10m. The artificial enriched domesticated bacteria liquid is introduced in the initial stage of leaching, and then the acidic mine water of the mining flat is used to mix the appropriate amount of industrial sulfuric acid, The leaching agent adjusted to pH 2 is sprayed and leached. At present, it is generally not necessary to supplement the bacteria liquid separately, just adjust and maintain the pH at about 2. When the Cu2+ mass concentration in the leachate is greater than 1.5 g/L, it is sent to the extraction electrolysis section to produce cathode copper.
At present, a 1000 t/a heap leaching test production plant has been built, the leaching cycle is 210-240d, the leaching rate is 70%-75%, the quality of electrical copper reaches the l# copper standard, and the production cost per ton of copper is 10729 yuan. The company plans to expand a bio-metallurgical plant with a capacity of 10,000 tons of electric copper and build the largest biological copper extraction base in China.
(3) Copper recovery process and technical indicators of Zhongtiaoshan Tongkuangyu Copper Mine
Tongkuangyu Copper Mine contains a large number of difficult-to-mine and difficult-to-select low-grade copper oxide ore, with proven reserves of more than 18 million tons, ore grade of 0.65%, and oxidation rate greater than 50%. In 1997, Zhongtiaoshan Nonferrous Metals Corporation, Beijing General Research Institute of Mining and Metallurgy and Changsha Mine Research Institute jointly carried out the 'difficult to mine and difficult to select low-grade copper oxide ore underground leaching industrial test'. After nearly 4 years of systematic and comprehensive The experimental research work has formed a complete production technology suitable for in-situ crushing, leaching and recovery of copper in underground mines.
There are currently two leaching plants in production and construction, namely, the industrialized experimental leaching plant in the eastern part of the 5# ore body and the in-situ leaching plant in the subsidence area.
5# Orebody in-situ crushing test solution leaching plant
The test ore block has a horizontal elevation of 930-968m, an average dip angle of 400, a length of 62m, and an average thickness of 14m. The amount of geological minerals is 33,200 tons, with a grade of 0.975%. The main ore-bearing lithology is meta-quartz crystal-clastic tuff and meta-quartz porphyry. The main copper-bearing minerals in the ore are malachite, chrysocolla, chalcocite, and copper blue, and the main gangue minerals are quartz and sericite. First, the ore is crushed to less than 200mm (>80%) by the method of millisecond squeeze blasting, and then the dilute sulfuric acid with a concentration of 1.5% to 2% is pumped to the test stope 958, 968 horizontal liquid distribution roadway, and then through the diverter valve, 4m downward fan-shaped liquid distribution holes to evenly distribute liquid on the entire stope plane. The dilute sulfuric acid entering the stope penetrates through the ore at a certain speed from top to bottom by gravity, and The Cu2+ in the ore reacts to produce copper sulfate solution, which is collected in the sump at the bottom of the stope, and then pumped to the extraction electrolysis workshop to produce cathode copper. The extraction electrolysis process is the same as other production plants.
In 2 years of production, it has produced 1,000 tons of high-quality electrowinning copper, with a sales income of more than 16 million yuan, a profit and tax of more than 7 million yuan, a unit product cost (excluding tax) 9,000 yuan/t, a comprehensive recovery rate of 71%, and good economic benefits.
4. Test of bio-oxidation process on prospecting ore
The biological oxidation leaching process has developed rapidly abroad in recent years, and the technology is still in the stage of experimental research and trial production in China. In principle, this technology can be applied to gold, copper, nickel, lead, zinc, cobalt and other minerals, but at present, it is mainly applied to the leaching of gold and copper at home and abroad. At present, the Yantai gold bio-oxidation leaching factory (50t/d), the Shaanxi Geological and Mineral Bureau's bio-oxidation leaching test plant (10t/d) and the Laizhou bio-oxidation leaching factory (100 t/d) have been built to deal with the difficult problems of arsenic and sulfur. Dip gold concentrate powder. There are Dexing Copper Mine and Zijinshan Copper Mine in the copper hydrometallurgical test plants that adopt biological oxidation and form a certain production scale. The Northwest Nonferrous Geological Exploration Bureau has also carried out exploratory experiments in this area for some mine prospecting ore, but the results are not satisfactory, mainly due to the influence of the nature of the ore. The ore contains high acid-consuming minerals such as calcium and magnesium, and wet leaching is carried out under acidic conditions of pH<2. In 1999, the Biological Research Center of Shaanxi Provincial Institute of Geology and Mineral Research conducted a bacterial oxidative gold leaching experiment on the Jianchaling flotation gold concentrate. The Jinchaling flotation gold concentrate belongs to the low-arsenic and low-sulfur refractory gold concentrate. The gold is present in the sulfide minerals and gangue minerals in the form of fine particles. The sulfide-coated gold accounts for 44.76% of the silicate-coated gold. 9.26%, carbonate coated gold accounts for 5.79%, and w(S)=6.22%, W(As)=0.82%. The gold concentrate is directly cyanided, and the gold leaching rate is only 35.3%; after 120 h of bacterial pre-oxidation, the gold leaching rate is 92.72%. However, due to the high content of alkaline components CaO and MgO in the concentrate, up to 26%, the acid consumption in the oxidation process is high, up to 20%, that is, the acid consumption per ton of concentrate is 200 kg, and the processing cost per ton of concentrate is 240 yuan. In 2002, the Xi'an Jushi Bioleaching Research Center conducted a biological oxidation leaching test on the primary copper ore in Mujiazhuang, Shaanxi. Also, because the gangue mineral in the ore is mainly iron dolomite, the acid consumption is relatively high, and the acid consumption per ton of ore is 205 kg , The following bacterial oxidation test was not carried out. According to relevant information, acid leaching or biological oxidation will be difficult when the alkaline gangue content in the ore is greater than 5%. Not only does the acid consumption is large, but also the sulfuric acid reacts with calcium oxide to form gypsum, which is covered on the surface of the ore and affects the leaching. The Tangdan Mine of the Dongchuan Mining Bureau of Yunnan takes the high alkaline gangue concentrate obtained from flotation as the object, and uses the rotary kiln roasting-pressurized ammonia leaching-extraction-electrowinning process to prepare copper cathode, which has achieved good results , But the research on raw ore has not made a bigger breakthrough.
It is undeniable that the hydrometallurgical process is one of the effective methods for large-scale processing of low-grade non-ferrous metals and precious metal ore in the future, and it is also one of the key directions of research and development in many countries in the world. With the continuous emergence of new achievements and the continuous improvement of technology, many ores that cannot be processed by existing methods may be fully utilized in the near future.