From a global perspective, the nickel resources mined are sulfide ore and laterite nickel ore. Currently, about 70% of nickel is extracted from nickel sulfide ore. However, with the depletion of nickel ore mineral resources in the world, the development and comprehensive utilization of low-grade laterite nickel ore has gradually become a research hotspot.
Nickel laterite nickel sulfide ore resources rock weathering, surface weathering crust deposits formed after deposition and leaching, natural type of ore to limonite and saprolite ore type type-based, industrial type nickel silicate ores, the nickel element The cable is mainly stored in the form of silicate minerals. Therefore, it is difficult to recover the nickel resources in the laterite nickel ore by the traditional beneficiation process, which seriously restricts the effective utilization of laterite nickel ore.
The laterite nickel ore deposit consists of three layers: the upper layer contains higher iron, and the nickel and limonite coexist, which is called limonite type laterite nickel ore; the lower layer of silicate mineral is relatively enriched, nickel and silicate minerals. symbiosis, a silicon magnesium nickel ore, garnierite type called nickel laterites; between the portion called limonite and transition garnierite nickel laterite. Since nickel laterite component complex, very different and varied nature of the ore, the present study shows that pyrometallurgical process metallurgical processing nickel laterite ferronickel product preparation method is the most effective, but the phase change transition in metallurgical processes affecting pyrometallurgical Enrichment and recovery of ferronickel products.
At present, there are two kinds of processes, such as high pressure acid leaching (HPAL, PAL) and reduction roasting ammonia leaching (CARON process), which are widely used in industrial applications, but both processes have certain problems. The CARON process has a low leaching rate and high energy consumption, which greatly limits the development and application of this method. HPAL Process for low-grade nickel, aluminum, high magnesium content and a high clay content lateritic nickel ore, the sulfuric acid consumption of the process is relatively large, it is not economical process; infrastructure investment, autoclaving harsh conditions, the engineered There are some problems, such as autoclave scaling, which affects the continuous production of pressurized leaching requiring high salinity water, while high salinity water is more serious to equipment, pipelines and valves.
In view of the shortcomings of the traditional roasting process, scholars have mainly done the following research in the following years: (1) Activated roasting, pretreatment of ore by activated roasting, changing the crystal form of some ore phases, resulting in the collapse of the original structure of the mineral, resulting in The specific surface area and pores increase, which is conducive to the subsequent leaching process; (2) salt roasting, alkali metal salt or ammonium chloride distorts the lattice lattice of the metal oxide, and causes the reduction product to generate micropores and accelerate the reducing gas Internal diffusion, so that the nickel present in the iron oxide in the form of isomorphism is exposed; (3) direct reduction roasting, adding a certain amount of reducing agent, flux and other additives to the laterite nickel ore The carbonaceous pellets of the laterite nickel ore are produced by direct reduction to effectively remove the sulfur contained in the granular iron.
In terms of leaching, the main research progress is as follows: (1) In terms of acid leaching, in addition to using traditional sulfuric acid as the leaching agent, hydrochloric acid leaching and using ascorbic acid as a reducing agent, the leaching rate of nickel is as high as 95% or more; (2) alkali leaching In this respect, the leaching two washing process and the high concentration alkali leaching laterite nickel ore silicon extraction process were explored; (3) in the high pressure leaching, the alkali pretreatment acid leaching material and sodium dodecyl benzene sulfonate descaling were explored. Nitric acid high-pressure leaching and other processes; (4) Other aspects, mainly studied the method of adding a composite energy field of high-energy physics, microwave hydrothermal method and heating method.
1 Development of roasting process
In the roasting of nickel ore, the researchers have made a deep discussion on the mechanism of the effects of reducing agents and additives on the roasting of nickel ore during the process of nickel ore roasting. In the roasting process, new processes such as calcination, activated calcination and direct reduction roasting with different additives are proposed.
A adding additive roasting process
Different additives will have different effects on the roasting. The researchers have a clear explanation of the influence mechanism of the additives through the analysis of thermodynamics and kinetics. Sun Chang body using stone coal and smokeless coal comparative experiments found stone coal as a reducing agent resulting in ferronickel ore nickel, nickel-iron grade higher than the same amount of the obtained anthracite, iron grade, but nickel, iron The recovery rate is lower than the same amount of anthracite. Shi Jianfeng studied silica-magnesium and limonite-type laterite nickel ore and used sulfation roasting-water immersion process to study the mechanism of sodium sulfate in the sulphation roasting process. Lu Jie studied the reduction of red earth nickel ore in hydrogen and methane atmospheres. In addition, Shi Jianfeng et al. studied the mechanism of ammonium bisulfate roasting laterite nickel ore. Through thermodynamic analysis of the reaction, it was found that increasing the low temperature calcination temperature can promote the reaction of serpentine with ammonium hydrogen sulfate, but inhibits the reaction of olivine with ammonium hydrogen sulfate.
Adding an additive can effectively increase the leaching rate of nickel after baking. Shi Tangming studied the addition of sulfur-containing additives to strengthen the red earth nickel ore solid state reduction roasting. Five sulfur-containing additives such as elemental sulfur (S), calcium sulfate (CaSO4), sodium sulfide (Na2S), pyrrhotite (FeS), and sodium sulfate (Na2SO4) can enhance the reduction roasting-separation effect of laterite nickel ore, among which sodium sulfate (Na2SO4) has the most significant effect. Wang Zhijian et al. added sulfuric acid roasting of sodium sulfate to obtain the same desired effect. Hu Baolei et al. used ammonium sulfate roasting-water immersion process, the nickel leaching rate was 82.99%, and the cobalt leaching rate was 84.56%. Peng Jun et al. proposed a new process for the extraction of molybdenum and nickel from the existing nickel- molybdenum ore treatment process, and proposed a new process for nickel-molybdenum ore-calcium oxide roasting-low-temperature sulphate roasting-water leaching to extract nickel-molybdenum. Through the research and test on the Zunyi nickel-molybdenum mine in Guizhou, under the optimal process conditions, the leaching rate of molybdenum is 97.33%, and the leaching rate of nickel is 93.16%. Li Guanghui and others found that the addition of sodium salt roasting can improve the reduction-magnetic separation effect of laterite nickel ore, and significantly improve the nickel and iron grade and recovery rate of magnetic products. Fu Fangming et al. used a ammonium chloride chlorination roasting method to treat laterite nickel ore to achieve selective chlorination. When water immersion is used, valuable metals such as nickel, cobalt, and manganese are leached, and iron and magnesium are rarely leached. In order to reduce the cost of roasting, Yan Shufeng et al. used bituminous coal as a reducing agent to selectively reduce the calcination of low-grade laterite nickel ore to obtain better economic benefits.
B Activated roasting process and direct reduction process
Li Jinhui et al. used the treatment method of activated roasting laterite ore. After calcination, the same nickel leaching rate under other relatively harsh leaching conditions can be achieved in a shorter time, lower acidity and lower reaction temperature. , to a certain extent, inhibit the leaching of iron, which is conducive to the subsequent purification and enrichment process.
Coal-based direct reduction process for laterite nickel ore is a very important method for laterite nickel ore smelting, while laterite nickel ore has a high water content and generally contains 25% to 30% (mass fraction) of free water and crystal water. The high-temperature reduction smelting process consumes too much energy and will cause the production process to fail smoothly. It needs to be dried during the smelting process. Zhang Jianliang conducted an in-depth study on the mechanism of dehydration process. It was found that there are four mass loss steps in the red earth nickel ore during the heating process. The reduction process of laterite nickel ore can also be divided into three stages. In addition, Maurer et al. studied the direct reduction of laterite nickel ore to produce nickel-containing iron desulfurization process. The laterite nickel ore is used as a raw material, and a carbonaceous pellet is prepared by adding a reducing agent, a flux and an additive MnO, and is subjected to reduction and melting at a high temperature to obtain a nickel-containing iron. The desulfurization rate increased from 51.4% to 77.6%, and the desulfurization effect was significantly improved. The addition of MnO had little effect on the recovery of nickel, iron grade and nickel and iron in the granular iron.
2 Development of leaching process
For the leaching treatment of nickel-containing minerals, it is divided into acid leaching and alkali leaching according to the selection of the leaching agent, and is further classified into pressure leaching and atmospheric pressure leaching according to the leaching method.
A acid leaching
In recent years, researchers have conducted extensive thermodynamic and kinetic analyses of the nickel acid leaching process. Su Xiuzhu investigated the kinetics of microwave acid leaching process. The leaching process of nickel was controlled by surface chemical reaction, and the leaching process of cobalt was controlled by internal diffusion. Wang Gang et al. studied the kinetics of sulfuric acid leaching serpentine. The sulfuric acid leaching of serpentine is a liquid-solid multiphase reaction process. When sulfuric acid leaches nickel from serpentine ore, sulfuric acid concentration, leaching temperature and ore particle size are nickel. The leaching rate has a significant effect, and the stirring speed has little effect on the nickel leaching rate. The nickel sulphate extraction process follows the kinetics of the unreacted shrinkage nuclear model, and the leaching process is controlled by chemical reaction. Luo Wei et al. calculated the kinetics of sulfuric acid inlet and outlet system to obtain the activation energies of nickel and manganese of 53.9kJ/mol and 69.4kJ/mol, respectively. Li Jinhui et al. studied the hydrochloric acid leaching system. The thermodynamic calculation results show that the mineral phases (except Fe2O3) in the minerals can react with hydrochloric acid under normal pressure, and the equilibrium constant decreases with the increase of temperature.
By improving the conventional acid leaching process, the researchers obtained better process indicators. In the field of atmospheric pressure acid leaching, Li Jianhua et al. proposed an acid granulation process for the low-grade nickel oxide ore outside Jinchuan. Fan Xingxiang et al. improved the sulfuric acid leaching process and leached nickel from laterite nickel ore by dilute sulfuric acid two-stage countercurrent immersion method. Under the optimal conditions, the nickel leaching rate is above 78%, and the acid consumption is about 64t/t nickel. The effect is ideal. Luo Wei et al. found that the treatment of laterite ore by sulfuric acid atmospheric pressure acid leaching process, using low temperature (about 90 ° C) and prolonging the leaching time helps to increase the leaching rate of nickel. Liu Yao et al. use an atmospheric pressure sulfuric acid (hydrochloric acid) leaching process to easily dissolve nickel from humus ore. Yan Zonghua is also feasible to treat humus ore from Manuran Island, Indonesia, using a leaching-neutralization-sinking process. Zhou Xiaowen et al. used an atmospheric pressure acid method to treat a laterite nickel ore in Dingnan. The comprehensive recovery rate of nickel can reach more than 75%. The precipitation of nickel hydroxide is added to concentrated sulfuric acid to evaporate and crystallize, and the obtained crystalline nickel sulfate reaches the national GB 6392-1986. Requirements for secondary products.
RGMcDonald first grinds and classifies the laterite ore, reacts the ground slurry with the washing liquid and sulfuric acid in a certain ratio under heating conditions, leaches the nickel in the ore into the solution, and then uses calcium carbonate for neutralization. After treatment, liquid-solid separation is carried out. Gao Yan studied the extraction rates of nickel, cobalt, nickel, cobalt, manganese, iron and magnesium in the laterite nickel ore extraction by atmospheric pressure hydrochloric acid leaching process to 93.94%, 60.5%, 94%, 56% and 94%, respectively. Fu Fangming discussed the process conditions of hydrochloric acid leaching of laterite nickel ore in the Lancang area of ​​Yunnan, and the leaching rate of nickel reached 93.94%. Fu Fangming also used ascorbic acid as a reducing agent to dilute laterite nickel ore with dilute hydrochloric acid. The nickel leaching rate reached 95%.
In addition to the treatment of laterite nickel ore, Che Xiaokui uses sulphuric acid at normal pressure to leach silicon-nickel ore. The leaching rate of nickel in the leaching solution is about 86%, and the leaching residue contains about 0.12% nickel. Wang Baoquan et al. used the atmospheric pressure sulfuric acid leaching of limonite type laterite nickel ore after roasting sodium carbonate. The leaching rates of nickel, cobalt and iron were 99.2%, 99.5% and 97.8%, respectively.
B alkaline leaching and ammonia leaching
According to the relationship between nickel and copper leaching rate and time, Jiang Bo et al. obtained the kinetic equation of ammonia leaching process by fitting calculation. The results accord with the internal diffusion control model. Part of the nickel oxide enters the magnesium silicate mineral crystal lattice in the form of homogeneous phase. This part of nickel can not be leached under the ammonia-ammonium salt-water system, which is the main reason for the low nickel leaching rate. In addition, Yan Wenning et al. obtained the optimum conditions for high-concentration alkali leaching of silicon in laterite nickel ore by orthogonal test. The leaching process uses a single leaching process, and the extraction rate of SiO2 can reach more than 85%. After the red earth nickel ore is subjected to high-concentration alkali leaching, elements such as nickel, magnesium and iron are enriched in the slag, and the nickel content can reach 2.89%. It can be seen that the high-concentration alkali-leaching laterite nickel ore is feasible, which opens up a new way for the high value-added comprehensive utilization of laterite nickel ore.
C pressure leaching
In view of the problems of pressure leaching and the like, the autoclave is easy to scale, and the high acid is corrosive to the equipment, the researchers have made some improvements to the pressure leaching process and achieved good results. The study of high-pressure acid leaching laterite nickel ore has a leaching temperature of 250-280 °C. At this temperature, the pressure is higher, and the requirements for the autoclave are higher, which poses a safety hazard. Wang Yunhua improved the traditional high-pressure acid leaching (HPAL) process by initially charging a certain amount of oxygen in the reaction and leaching the Australian dry-type laterite nickel ore at a lower temperature. The leaching rates of nickel and cobalt were 99.83% and 90.44%, respectively, which were roughly equivalent to the leaching rates of nickel and cobalt when not filled with oxygen at 250 °C. Yan Xiujing et al. studied the problem of reactor fouling during high pressure acid leaching of laterite nickel ore and found that sodium dodecylbenzene sulfonate can reduce the surface tension and viscosity of the slurry. Zhang Yonglu et al. used alkaline pretreatment to treat laterite nickel ore and pressure leaching in mixed acid medium. The process has good stability, and the leaching rates of nickel and cobalt are maintained at 95% and 80%, respectively. Ma Baozhong conducted a pilot study on the pressure leaching process of laterite nickel ore using nitric acid. The leaching rates of nickel and cobalt are 84.50% and 83.92%, respectively, and the iron leaching rate is as low as 1.08%. The high-efficiency separation between nickel (cobalt) and iron is achieved, and the process stability is good.
In addition, for the leaching of nickel-molybdenum ore, Zhu Jun et al. realized the conversion of molybdenum and nickel sulfide to oxide under the conditions of calcination temperature of 500-550 ° C and calcination time of 4 h, and finally the leaching rate of nickel reached 97.18. %, the total leaching rate of molybdenum can reach 92.72%. In addition, Zhang Bangsheng proposed a new process for the treatment of nickel-molybdenum ore by a full-wet process combined with pressurized acid leaching-atmospheric pressure alkaline leaching-extraction. In pressurized acid leaching, the conversion of molybdenum can reach 98.3% or more, and the leaching rate of nickel reaches 98.7%. After alkali leaching-extraction, the comprehensive recovery rate of molybdenum and nickel is over 92%.
D other leaching process
In recent years, researchers have improved the leaching effect by changing the physical conditions of the leaching process. Han Chaohui et al. used a composite energy field of a high-energy physics with a power of 40 kW to enhance nickel leaching.
Microwave hydrothermal method is a new method for nickel ore leaching. Yan Xiujing was leached by microwave method. The leaching rate of nickel and iron and the temperature of the reaction system increased with the increase of microwave radiation power, and the leaching rate of nickel was 99%. Zhao Yan and others further studied the microwave leaching process of hydrothermal system. Compared with the common hydrothermal leaching system, the microwave leaching system has the best leaching effect of nickel and cobalt.
In addition, Zhang Yi et al. used the heating method to solve the problem that the laterite nickel ore is easily muddy, compacted, directly leached, has poor permeability, and the nickel leaching rate is very low. Xue Juanqin et al. added thiosulfate to the leaching system. It was found that the leaching rate of nickel increased as the concentration of Na2S2O3 increased. As the temperature increases, the nickel leaching rate increases, but when the temperature is higher than 70 ° C, the leaching rate does not increase significantly. Luo Yongji et al. found through experiments that nickel-containing serpentine ore is feasible to be leached with sulfuric acid under normal pressure. Sulfuric acid has good selectivity for leaching of nickel and iron.
3 Development of new processes
A segregation
In order to reduce the high pollution and high energy consumption of the roasting process, many researchers have studied the chlorination separation and nickel extraction process. The chlorination of nickel laterite ore is mainly carried out by chlorinating the valuable metal therein and then reducing and enriching the chloride on the surface of the reducing agent. This complex chemical change process is mainly affected by the amount of reducing agent, the temperature of separation, the time of separation, the heating system and external additives.
He Zhenjiang and others obtained the amount of reducing agent used as 6%, the amount of chlorinating agent (calculated as chlorine element) was 8%, the separation temperature was 1000 ° C, the separation time was 60 min, and the temperature was maintained at 600 ° C for 40 min. And the addition of 0.1% iron powder is the best chlorination conditions. Xiao Junhui and others used the separation-magnetic separation process, and the results were also very satisfactory. Chen Xiaoming conducted a semi-industrial test on the Yuanjiang nickel silicate mine and obtained an ideal test index. A nickel concentrate with a grade of 10.33% and a recovery rate of 87.22% can be obtained by using a new process of adding a chlorinating agent, a reducing agent ball, and a separation roasting magnetic separation.
B Extraction and precipitation
Li Lingdeng found an amino functional group structure capable of phosphoric acid is preferably a synthetic resin, has a significant effect on the separation of nickel and iron, having good prospects, ion exchange method can be applied to the extraction of nickel, heteroaryl-lean solution recovered solution The problem of medium nickel, the resin has great development prospects. Jiang Chengzhi uses Span80 as a surfactant, TBP as a mobile carrier, Na2S as an internal phase reagent, and an emulsion liquid membrane method, which can extract nickel more than 80%.
In the aspect of sedimentation process, Wang Ling et al. used Na2S·9H2 as a precipitant to enrich and recover nickel, cobalt and other valuable metals in the red earth nickel ore acid leachate after preliminary iron removal at normal temperature and pressure. Nickel and cobalt were used. The recovery of valuable metals is high, the method is simple, and it is easy to operate, especially the high-concentration magnesium is effectively separated, and high-grade nickel concentrate is obtained. Qi Jianyun studied an imported laterite nickel ore, leached with sulfuric acid under normal pressure to control certain conditions, and the nickel leaching rate reached 78.62%.
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