As a special functional material, nickel has been widely used in the national economy. The plurality of magnetic material as a main component; a battery industry for a nickel - hydrogen batteries, are widely used as catalysts in the chemical industry; in rocket technology, ultra-pure nickel or a nickel alloy for high temperature structural materials. It is particularly worth noting that pure nickel is also used in modern new technologies such as radar, television, atomic industry, and remote control. However, China's nickel resources are actually in a state of shortage. To maintain a fast, healthy, and sustainable development of the national economy, it is necessary to keep the growth rate of nickel in line with the growth rate of the economy. Therefore, exploring potential from various aspects, making full use of nickel materials (such as metallurgical beneficiation waste residue, increasing nickel recovery rate, etc.) will play a certain role in alleviating the shortage of nickel resources in China.
In recent years, the discussion on hydrometallurgical technology instead of pyrometallurgy has become more and more intense. As a mature technology, hydrometallurgy has received more and more attention from peers, especially the extraction of precious metals from low-grade mineral resources. Get a high recovery rate. At present, about 90% of the world's nickel is still produced by fire, and it cannot be replaced for a long time. The wet technology is widely used to produce high-grade metals. The reason is mainly due to the large investment in wet smelting technology, high cost, large impact by ore, etc. It is difficult to achieve large-scale promotion and application in a short period of time. Therefore, economical, efficient and green hydrometallurgical technology has become the focus of research by researchers. It aims to solve the existing deficiencies, achieve widespread industrial production, and contribute to the green and economic saving advocated by the state.
1. Method for wet smelting of nickel ore
(1) Ammonia leaching method (RRAL method)
Ammonia leaching - i.e. nickel after drying and calcination multistage pressure reducing ammonia leaching, by Professor Caron invention Rral process, also known as Caron process, suitable for handling higher-containing magnesium (MgO> 10%), nickel About 1% of silicate type laterite ore, the basic process is reduction roasting - ammonia leaching. The purpose of the reduction calcination is to maximize the reduction of nickel silicate and nickel oxide to a metal while controlling the reduction conditions to reduce Fe to Fe 3 O 4 . The nickel and cobalt in the calcination are leached by the ammonia solution, and the iron in the leaching residue can be recovered by magnetic separation. Its representative factory is the Cuban Nigro nickel plant built in the United States. The nickel ore is treated by ammonia leaching, and the product may be a nickel salt.
Ammonia leaching treatment process is not suitable for treatment of copper-containing and cobalt-containing high nickel and sintered nickel garnierite, a nickel powder, a nickel block like. The nickel mine in New Caledonia is only suitable for the treatment of the laterite clay, which greatly limits the development of the ammonia leaching process. In addition, the recovery rate of nickel and cobalt in the ammonia leaching process is low, the recovery rate of nickel in the whole process is only 75% to 80%, and the cobalt is about 40% to 50%. So far, only four factories in the world have used ammonia leaching to treat nickel oxide ore, and they were built before the 1970s. For more than 30 years, no new plant has used ammonia leaching. This method has some disadvantages: (1) it can not economically process nickel ore with high copper content; (2) some precious metals dissolved in the process cannot be recovered; (3) hydrogen is a relatively expensive reducing agent in the reaction process. Can not be fully utilized; (4) The reaction speed is slow, the concentration of metal ions in the solution is low, and the equipment is huge.
(2) Acid leaching method (HPA method)
Acid leaching method: under the high temperature and high pressure conditions of 250 ° C to 270 ° C and 4 to 5 MPa, the valuable metals such as nickel and cobalt are dissolved together with iron and aluminum minerals with dilute sulfuric acid, and in the subsequent reaction, the control is controlled. Under the conditions of pH and the like, impurities such as iron, aluminum and silicon are hydrolyzed into the slag, and nickel and cobalt are selectively introduced into the solution, and are recovered from the solution by solvent extraction, sulfide precipitation and the like. The industrial production of nickel ore by the acid leaching process began in the 1950s, when the representative factory was the Cuban Ma'ao nickel smelter, which was also designed and built by the United States. The acid leaching process is suitable for treating nickel ore with low magnesium content. If the magnesium content in the ore is too high, the acid consumption will be increased, the operating cost will be increased, and the process will also be affected. If the cobalt content in the ore is high, it is more suitable to use the acid leaching process. Not only is the leaching rate of cobalt higher than that of the ammonia leaching process, but since the value of cobalt is higher than that of nickel, the unit production cost of the acid leaching process is greatly reduced. Although the high-pressure acid leaching nickel leaching rate can reach more than 90%, the acid leaching process is also restricted by the ore conditions. At present, there are only three factories in the world that use acid leaching to treat nickel oxide ore, and the equipment is processed due to high temperature and high pressure. Demanding and running are not very normal. Overall, the development of the acid leaching process is not yet mature.
(3) Oxygen pressure leaching method
The process used is a pyrite concentrate containing 2% nickel, pressurized leaching with 80% oxygen-enriched air, and then precipitated nickel and cobalt by sulfide precipitation, and selected by flotation method. Nickel concentrate and elemental sulfur, nickel concentrate is treated by fire.
(4) Chlorination leaching method
Chlorination leaching is a process in which nickel, cobalt, copper, or the like in a nickel ore is formed into a chloride form by chlorination. Since the chemical activity of chlorine and chloride is extremely high, the generated chloride has a large solubility, so at normal temperature, chlorination leaching can reach the technical index that must be heated and pressurized in other media. According to the type of leaching agent, high nickel comb leaching is divided into hydrochloric acid leaching and chlorine gas leaching. Yingqiao Company was the first factory to use chlorination leaching for high nickel bismuth treatment. In the 1960s, the company developed a new process for leaching high nickel flow from hydrochloric acid, and built an industry with an annual output of 6,800 tons of nickel in Kristiansund, Norway. The pilot plant was put into production in 1968. In 1977, Yingqiao Company successfully developed a process for chlorine gas leaching high nickel flow, which has been applied in industry. The French nickel metallurgical company Leaf N. Nickel Refinery, which was put into operation in 1978, adopted a similar process. The research unit of our country also conducted a certain scale of experimental research on the chlorination leaching process.
Second, the status quo of foreign nickel ore hydrometallurgy development
For the treatment of nickel ore, nickel and copper separation and refining have always been key issues in the nickel smelting process. In the early stages of the development of nickel metallurgy, nickel ore is usually treated by layered smelting and preferential diffusion.
Slow cold beneficiation separation of high nickel flow and nickel sulfide anodic electrolysis is a major advance in nickel smelting technology in the 1960s. There are many factories in the world that use this technology, mainly Thompson Plant of Canada International Nickel Corporation, Nickel Refinery of Korborn Port, and Zhicun and Zizi of Japan. Compared with traditional nickel electrorefining, this process has the advantages of simple process and low capital investment.
From the 1970s to the present, the wet extraction process of high nickel, nickel, nickel and copper separation abroad has made great progress, namely selective leaching. Secondly, the carbonylation process of gasification and metallurgy has also been successful. Manufacturers using selective leaching processes, the most famous ones are the selective leaching method of sulfuric acid used by the Finnish Outokumpu Hajjavarta plant; the chlorination leaching method adopted by Canadian Eagle Bridge and the Canadian Shelter Galton Company Pressurized ammonia leaching method. Among these methods, the selective leaching method of sulfuric acid has developed rapidly, and many nickel refineries have applied the process for industrial production, such as the Slim Nickel Refinery in Inpac, South Africa, the Bindura Smelter in Zimbabwe, and the Amax Nickel Refining in the United States. The company's nickel port refinery and Zimbabwe Gatoma smelter.
Third, the status quo of domestic nickel ore hydrometallurgical development
In ancient China, a large number of copper-nickel alloys (white copper) and zinc -nickel gold (zinc white copper) have been produced. In 1953, the Shanghai Smelter successfully produced nickel sulfate from the copper electrolysis waste liquid by direct fire evaporation, and then carried out the test for extracting metallic nickel from crude nickel sulfate. In 1954, 75 kilograms of nickel was produced, which opened the curtain for China's nickel hydrometallurgy. In 1959, the Shanghai smelter began to produce electrolytic nickel from nickel oxide imported from Cuba. The initial scale was 400 tons of nickel per year. In 1973, it reached an annual production capacity of 2,500 tons of nickel. With the successive mining of Sichuan Huili nickel mine, Jinchuan nickel mine, Jilin meteorite nickel mine in the 1950s and 1960s, and the Kalatongke nickel-copper mine in Xinjiang in the 1980s, the wet smelting of nickel has flourished. A number of enterprises such as Chengdu Electric Metallurgical Plant, Chongqing Smelting Plant, Jinchuan Nonferrous Metals Company and Ji Kang Smelting Plant have been built, and the output has also increased substantially. The total annual production capacity of electro-nickel has exceeded 50,000 tons.
China's nickel industry production, the main wet treatment processes currently used are: nickel sulfide anode membrane electrolysis, metal nickel anode electrolysis and sulfuric acid selective leaching, electrowinning process. Nickel sulfide anode membrane electrolysis process is still the most important electrolytic nickel production process in China. The electrolytic nickel produced by this method accounts for about 90% of the total nickel production in the country. The main manufacturers include Jinchuan Nonferrous Metals Co., Ltd., Chengdu Electrometallurgical Plant and Chongqing Smelter. The electrolysis production processes of these plants are basically the same, generally including the two processes of diaphragm electrolysis and solution purification, and each factory has only slightly different in these two processes. For example, several manufacturers use an electrolyte of a sulfuric acid monochloride mixture system to purify the solution by a three-stage chemical precipitation method. However, Jinchuan Company began to use high current density and high pH electrolysis process since the early 1980s. The process of solution purification and copper removal adopts the replacement method of adding nickel concentrate and anode mud, and also studies the new process of removing active copper by active NiS; Chengdu The current intensity of the electro-metallurgical plant is controlled at about 5,500 amps, using the H 2 S copper removal process. Shanghai smelter used metal nickel anode electrolysis process to produce electrolytic nickel, and used imported nickel, imported nickel oxide, nickel phosphorus iron to produce crude nickel anode plates. Among them, the process of producing electrolytic nickel by using imported nickel oxide is relatively mature. The anode is formed by casting nickel nickel with petroleum coke as a reducing agent in an electric arc furnace. The cathode process is exactly the same as the nickel sulfide electrolysis. The electrolyte used is also a sulfate chloride mixed electrolyte. The specific process flow and process conditions adopted by each plant are different. This aspect is related to the different raw material composition and product form requirements of each plant. On the other hand, it also indicates that the hydrometallurgical process of nickel needs further research and development.
Fourth, the outlook
From the perspective of environmental protection, the hydrometallurgical process does not cause the emission of sulfur-containing gases. From an economic point of view, the use of hydrometallurgical processes in the treatment of some complex mines, such as platinum- nickel ore, nickel ore, the loss of the mine is small and the energy consumption in the smelting process is also small. From a process perspective, the wet process is more cost effective in dealing with low grade complex mines. The use of a wet process allows selective leaching of valuable metals to achieve efficient separation from impurity elements, which facilitates further recovery of valuable elements from the solution. It is believed that with the development of science and technology, the hydrometallurgical technology of nickel ore will be more developed and applied.
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