World demand for metals is growing, making the low-grade ore in the study of metal extraction even more urgent, due to continuous development and depletion of mineral resources of zinc sulfide, how to develop and make good use of zinc oxide ore resources appear to be increasingly important.

Zinc oxide ore is a secondary mineral of zinc and is an important class of zinc-containing minerals, mainly from ZnCO 3 (ZnCO 3 ), heteropolar ore [Zn 4 (Si 2 O 7 )(OH)·H 2 O], Zinc-zinc ore (ZnSiO 4 ) exists in the form of a large amount of metal impurities such as lead , iron , cadmium , copper, etc. Among them, gangue minerals are mainly calcite , dolomite, quartz , clay , iron oxide and iron hydroxide. Zinc oxide ore is distributed in many countries in the world, such as Brazil, Zambia, Morocco, Namibia, Turkey, Thailand, Vietnam and other countries. China's zinc oxide ore resources are also very rich, Yunnan, Guizhou, Gansu, Shaanxi and other provinces; especially in Yunnan, large reserves (such as Lanping lead-zinc mine), high grade, wide distribution, almost all of the province.

According to the statistics of the National Bureau of Statistics of China, the total annual zinc output in 2007 was 3.784 million tons, an increase of 18.1% year-on-year. China is the world's largest zinc-producing country and a better developed non-ferrous metal in China. Because the cost is lower than the world average, With profitability, major smelters have increased their production capacity and expanded their scale. At present, China's zinc ingot exports rank first in the world, and exports from January to November 2002 were 444,600 tons. China's total export of zinc metal accounts for more than 60% of China's zinc production, about 1 million tons. Experts predict that as automobiles, architectural coatings and durable industrial products are in the ascendant in China, the consumption of zinc metal in China will increase at a rate of 4% per year in the next 20 years. From the Dahua Finance website at the end of July 2007, the zinc market has been in short supply in the past three years. According to data provided by Xuanlong Investment, which specializes in futures research, in 2004, the global zinc supply gap was 255,000 tons; in 2005, the supply gap was 592,000 tons, and the supply gap in 2006 reached 426,000 tons. However, in 2007, there was an inflection point in the market. It is estimated that the global supply of zinc will be 11.706 million tons this year, the consumption will be 11.646 million tons, and the supply will exceed 60,000 tons. CBI non-ferrous metals analyst said: "After the first three years of tight supply, this year (2007) began, the world's major zinc mine production increase projects have been put into production. It is estimated that in 2007 foreign net increase in electrolytic zinc production capacity of 1.17 million tons According to the calculation of 40% of production capacity, it will bring about an increase of about 470,000 tons in 2007. The domestic mine output will increase by at least 400,000 tons, so the global zinc mine output is expected to increase by about 870,000 tons, an increase of 8.1%."

From the data of the China Finance website at the end of 2007, the domestic refined zinc output in June was 32,600 tons, a slight decrease from the 323,600 tons in May.

Due to the increase of production capacity in the past 10 years, the consumption of domestic zinc concentrate is huge, and the lead-zinc mine has been exploited for many years, and the output is difficult to increase. At present, the development intensity of China's zinc mine reserves is 0.6%-0.8%, far less than China's. The development speed of zinc smelting, domestic large lead-zinc mines, such as: Fankou lead-zinc mine, Huangshaping lead-zinc mine, Shuikoushan lead-zinc mine reserves have been developed 54.54%, of the undeveloped reserves, a large number Remote areas with poor resources and construction conditions. The contradiction between mine-free mining and raw material supply shortage faced by China's lead and zinc industry has become increasingly prominent. From January to May 2008, China consumed 1.557 million tons of zinc, requiring import and export of 1,238,800 tons. Exploration shows that China's Lanping lead-zinc mine contains a large amount of zinc oxide ore, which is the only giant deposit with a reserve of more than 10 million tons in China, which can compete with world-class giant deposits. In addition, China's reserves are more than 2 million tons. There are 6 deposits in the Gansu factory, and there are also a large number of zinc oxide ore (the amount of metal is about 260,000 tons). At present, zinc concentrate has been imported in large quantities (more than 500,000 tons). It can be seen that the treatment and smelting of zinc oxide ore has received much attention as an important source of zinc metal.

The grade of zinc oxide ore is relatively low and the composition is complex. When the ore enters the smelting process directly, it is difficult to recycle and the production cost is relatively high. Therefore, the research on the treatment of zinc oxide ore has been utilized by zinc oxide ore. Research topics. At present, there are two types of zinc oxide ore treatment methods: one is that zinc oxide ore enters the smelting process to obtain metal zinc after beneficiation and enrichment; the other is that the zinc oxide ore is directly processed into the smelting process, and the direct smelting method can be Divided into fire and wet.

1. Zinc oxide ore beneficiation

The purpose of the beneficiation of zinc oxide ore is to pre-enrich the zinc oxide ore to increase the low smelting cost of the zinc oxide concentrate. So far, in addition to the full flotation method, the ore dressing method has heavy medium-flotation method, magnetic-floating process and other methods, but the ore dressing indicators are not very good, the recovery rate is 60% to 70%, and the concentrate grade It is 30% to 40%. The treatment of zinc oxide ore by flotation is one of the most studied directions. This year, a lot of research and improvement work has been carried out on the flotation reagent and flotation process of zinc oxide ore, and various new agents have been developed. There has also been considerable progress in the mineral processing process, such as:

Liu Sanjun et al. used the ammonium sulfide method for flotation, that is, using a primary amine as a collector to float zinc oxide minerals in a sodium sulfide medium. The grinding fineness is below 74μm, accounting for 86.5%; the (NaPO 3 ) 6 dosage is 400g/t, the Na 2 S dosage is 6000 g/t, and the dodecylamine dosage is 550 g/t, the zinc concentrate grade is 24.52%. The recovery rate was 69.27%. Since the test zinc oxide containing a large amount of mud, grinding not too small, otherwise it will cause more metal loss; test using sodium hexametaphosphate as a dispersing agent were tested, the test results in general. The grade of zinc oxide concentrate has not increased much, and effective flotation separation has not yet been carried out.

Yan Xiaoling used a single flotation method to conduct a 30kg/h continuous flotation test on low-medium iron-lime-type zinc oxide ore in the Lanpingjiashan area of ​​Lanping, Yunnan. The zinc content of the ore was 49.22%, and the total zinc recovery rate was 72.2%. In addition, a small amount of qualified sulfur concentrate and lead concentrate are produced, so that the valuable components thereof can be comprehensively utilized. However, it also produced a sludge containing 11.97% of zinc grade, accounting for 16.94% recovery rate, which is difficult to use. In addition, the slime interferes with the flotation operation, the consumption of the medicament is large, and the cost is high.

Zheng Ping et al. used a grinding machine, a spiral classifier, a split mud bucket, a cylinder sieve, and a shaker as equipment to change the size of the particle size by controlling the particle size, slurry concentration, and shaking. The bed is graded, stroked, sprinted, and the zinc concentrate is obtained by re-election of the slurry under the impact of clean water in a shaker classification tank. The outstanding advantage is that the environmental pollution is small, no chemicals are needed, the processing volume is large, the investment is small, the benefit is good, and the tailings can be turned into profit.

Wang Qingzhong separated the coarse-grained minerals by scrubbing, stirring and sedimentation, and then sedimented and separated the clay impurities to obtain powder concentrates such as diatomaceous earth . Finally, the powdery impurities were separated from the diatomaceous earth and separated by the above three stages. High-purity concentrate with high recovery rate, low cost and no pollution. The beneficiation system of the invention has the characteristics of high automation degree, simple structure, small land occupation, low energy consumption, low processing cost, simple operation and continuous production. Adapted to low-grade non-ferrous metal or non-metallic mineral tailings or low-grade tin zinc oxide, copper oxide, manganese oxide or ultra-low-grade uranium ore purification and so a high quality concentrate.

Chen Tie et al. aimed at the floating characteristics of the granitic zinc oxide ore after floating small particles and floating the large particles. After the minerals were subjected to grinding and oxidative flotation, the flotation tailings were coarsely selected from grade 1 to 3, and each stage was coarsely selected. The concentrate is selected 1 to 3 times. After the rough selection of the ore and the first selected medium ore into the next stage of rough selection, the fine flotation is carried out to obtain the concentrate. The invention patent solves the problem that the prior art is difficult to float the shale zinc oxide ore, and not only selects a useful zinc ore from the shale zinc oxide ore, but also improves the recovery of the zinc oxide ore. The rate reduces the amount of zinc oxide in the tailings and reduces the consumption of flotation agent, so that the mineral resources of the argillaceous zinc oxide ore are effectively utilized.

Sun Zhenguang uses chemical raw materials to select zinc oxide ore. The method uses non-toxic and non-polluting sodium hexametaphosphate as a separating agent, and is added to the ore immersed in water. The clay in the ore is separated by muddy water after being stirred and precipitated; After the ore is dried and pulverized, sodium hexametaphosphate is used as a separating agent, and sodium polyacrylate is used as a precipitating agent. The two are added to the ore powder immersed in water, and the ore powder is separated and precipitated by stirring, and the obtained ore powder is dried. After that, it is a zinc concentrate. The method for selecting zinc oxide ore according to the invention has the advantages of short process flow, good operability, low equipment investment, low processing cost and energy saving; the used water can be recycled after being precipitated without environmental pollution.

However, the enrichment of mineral processing is difficult and the recovery rate is low. Therefore, it is considered that the use of the flotation method cannot effectively recover the zinc oxide ore.

Second, zinc oxide ore fire treatment

Since ancient times, people have used smelting equipment such as a manger furnace to heat and reduce the smelting of crude zinc. The traditional smelting method of modern technology is: the grade is lower, generally it is first blasted with blast and then volatilized by the smelting furnace; the higher grade is generally volatilized directly by the rotary kiln and other equipment, both of which can obtain zinc. % to 60% of zinc oxide powder. This zinc oxide powder is desulfurized and chlorine removed by equipment such as rotary kiln and multi-hearth furnace, and then smelted by conventional wet method (wet leaching with acid leaching, alkali leaching) to produce electric zinc. .

Chen et al coke and coal charge zinc crushed into particulate material less than 40 mesh, zinc and coke charge in proportion to 0.35 1:0.30 be blended mix obtained mixture, then the mixture is made effective diameter of 8 to 15mm granule mixture, and finally the granule mixture is put into the rotary kiln for smelting. It has a large saving of coke or combustion when smelting zinc oxide ore containing zinc-containing ore containing zinc in the range of 15% to 25%, and the product obtained by smelting is of good quality and the productivity is small. .

Guo Xiaojun puts the zinc oxide ore into a high-temperature furnace for roasting. When roasting, the temperature of the charge is controlled between 1000 and 1500 °C, and the furnace gas property of the furnace layer is controlled to be weakly reducing or oxidizing. The zinc-containing material obtained by the process of removing lead and removing cadmium can be used for producing zinc oxide containing not less than 98% of ZnO.

Although zinc oxide ore is easy to be treated by fire, it has many process steps, long process, large fire equipment and high energy consumption. The energy consumption of 1t zinc is 10~15t, the recovery rate is only 50%~60%, and the environmental conditions are not. Well, therefore, metallurgical scholars in various countries are studying direct wet leaching.

Third, zinc oxide ore wet processing

Wet leaching generally has acid leaching and alkali leaching.

(1) Acid leaching

Direct acid immersion hydrometallurgical treatment of zinc oxide ore, including the treatment of high-silicon zinc oxide ore, is a new process that has been studied in many countries in the world in recent decades. Researchers have attempted to obtain qualified sulfuric acid by direct acid immersion hydrometallurgical process. Zinc solution is used as electrolytic zinc liquid to produce metal zinc. Most of the process is in the semi-industrial and industrial test stage. The leaching of zinc oxide in wet smelters in China usually uses two-stage intermittent leaching. For example, Zhuzhou Smelter uses a neutral leaching and two-stage acid leaching to treat zinc oxide. The process is shown in Figure 1. (One leaching is neutral leaching or acidic. Leaching should depend on the ingredients of the raw materials). Kunming Metallurgical Research Institute has carried out many years of experimental research on this process since the late 1970s, and the direct recovery rate of zinc is more than 75%. Several wet smelters of different sizes (200-5000 t/a electric zinc) have been built in Yunnan Province.

Figure 1 A section of neutral leaching and two-stage acid leaching process

Xie Meiqiu et al. designed a new process for low acid leaching, goethite iron removal and desiliconization and zinc extraction. The process consists of four main processes: acid leaching, desiliconization, iron removal, purification and electrowinning, as shown in Figure 2. . The acid leaching solution is purified by desiliconization and iron removal, and the waste liquid is returned to acid leaching, and the whole process solution constitutes a closed circuit cycle. In the process of desiliconization and iron removal, no additional neutralizing agent was used. According to the process, the leaching rate of zinc is 95.56%, the recovery rate of zinc is 86.96%, the slag amount is less, the slag rate is 70.35%, and the washing, clarifying and filtering properties are better; iron, Silica is mainly concentrated in acid leaching slag. The slag content of silica is 95.95%, and the slag content of iron is 96.91%. In the process of desiliconization and iron removal of acid leaching solution, iron in the goethite is removed. Impurities such as silica also enter the iron slag and are well removed. After desiliconization and iron removal, the liquid contains iron 37.2mg/L, silica 40 mg/L, cobalt 0.99 mg/L, arsenic 0.86 mg/L, and 锑 0.95 mg/L. The process is smooth and stable, and the effective recovery of zinc and The purpose of removing impurities.

Figure 2 Zinc oxide ore low acid leaching and zinc extraction process

Jiang Rongguang used a silicon-resistant acid leaching process in the acid leaching process, and added a silicon removal process before the oxidation neutralization and impurity removal process and the crystallization dehydration process. By using the method of the invention, zinc sulfate can be produced by using zinc oxide ore containing 10% to 30% of silicon oxide to achieve normal production, and the product quality reaches the national internal standard or primary standard. The invention utilizes general chemical equipment, has low investment and considerable economic benefit, which plays an active and effective role in improving the development and utilization of ore resources, and greatly reduces the cost of using the zinc sulfate to obtain lithopone and other zinc salts in the market. The process flow is shown in Figure 3.

Figure 3 Silicon-soluble acid leaching zinc oxide process

Wang Fengqin leached zinc oxide ore with ammonium chloride solution at a stirring speed of 300r/min, an average sample size of 0.075min, a reaction temperature of 90°C, an ammonium chloride concentration of 5mol/L, and a reaction time of 4h. The leaching rate is nearly 90%, and the iron concentration in the leachate is only 0.61 mg/L.

The shortcomings of the acid leaching process of zinc oxide are strict control of technical conditions and technical difficulty. In addition, the economic benefits are restricted by the grade of ore zinc. According to the current technical level, foreign treatment contains about 25% Zn, and domestic treatment contains Zn higher than 30. % zinc oxide ore has good technical and economic indicators. Moreover, the following problems exist:

1. There is a certain amount of silicon in the zinc oxide ore, and acid leaching is not easy to desiliconize.

2. The leachate has low zinc content, and the amount of leaching neutralization slag is large, and the solution balance is difficult to control.

3, the consumption of sulfuric acid is large, 1t zinc consumes more than 1t of acid, which is more than 5 times of zinc sulfide mineral acid consumption.

(2) Alkali leaching

The use of zinc is an amphoteric property which can be dissolved in an acid or a base. It has been proposed to leach zinc oxide by an alkali method such as an ammonia-carbon ammonium method or a sodium hydroxide method.

When leaching with the "ammonia-carbon ammonium" method, the reaction equation is:

ZnO+(NH4) 2 CO 3 =Zn(NH 3 ) 2 CO 3 +H 2 O

ZnSO 4 +(NH 4 ) 2 CO 3 +4NH 3 =ZnO(NH 4 ) 2 CO 3 +H 2 SO 4

Cu, Cd, Pb, and As have similar reactions.

When leaching with the "sodium hydroxide" method, the reaction equation is:

2NaOH+ZnO=Na 2 ZnO 2 +H 2 O

Liu Sanjun and others directly treated sodium lanthanum and ammonium-carbonammonium in Yunnan Lanping zinc oxide ore. The leaching conditions were: sodium hydroxide concentration 4 mg/L; leaching temperature 80 °C; liquid-solid ratio S:L=1: 10; leaching time 2h, the leaching rate of zinc oxide can reach 92.6%. For ammonia-carbon ammonium leaching, the leaching conditions are: leaching agent concentration 5 mg / L; temperature 25 ° C; S: L = 1: 15; time 1h, zinc oxide leaching rate can reach 91.3%.

Ma Qikun et al. used the alkali leaching-electrowinning process to treat low-grade zinc oxide ore, produce metal zinc powder or hydrolyze precipitate to produce zinc oxide powder, and use NaOH as solution as leaching agent to make zinc in ore as sodium zincate. Into the solution, the Na 2 S aqueous solution is used as a precipitate of lead, copper, cadmium and other impurity elements remaining in the slag to achieve separation of zinc and impurities. This process has low operating temperature, low energy consumption, simplified liquid cleaning operation, and shortened process A little bit, so that the zinc resources to be developed can be fully and effectively utilized. This method is particularly suitable for treating low grade zinc oxide ore containing less than 20% Zn.

Zhao Yicai et al. pulverized the zinc oxide ore to 0.1 to 1 mm, followed by leaching with a strong alkali solution, and after 10 to 100 ° C, and slowly stirring for 60 to 100 minutes, zinc and lead in the zinc oxide ore were leached. Filtration, filter residue discharge for brick or landfill. Leave a filtrate containing zinc and lead. Further, 0.1 to 5 times (molar ratio) of the separating agent is added to the filtrate, and the mixture is stirred for 60 to 100 minutes. After filtering and separating the lead-containing precipitate, the remaining zinc-containing filtrate is directly electrolyzed, and finally, on the cathode. The metal zinc having a purity of 99.95% or more is obtained by deposition, and the solution is returned to the alkali leaching after the electrolysis is completed. The cost of the invention is only less than half of the traditional process, and has no environmental pollution, and can be comprehensively utilized, and has greater economic and social benefits. This is a process for producing high-purity metal zinc using low-grade zinc oxide ore as a raw material.

Zhang Anzhen uses a metathesis reaction one-step method to produce basic zinc carbonate. The low-purity zinc salt mother liquor prepared from low-grade zinc oxide ore is used as raw material. At 78-85 °C, the amount of zinc is 2.3-2.8 times. The precipitated basic zinc carbonate can be obtained by inputting solid ammonium ammonium. The process produces basic zinc carbonate, which has stable quality, high output, fast production speed, simple equipment and low cost, and is especially suitable for production in small and medium-sized enterprises in towns and villages.

Yin Guozong extracts zinc, copper, nickel and cobalt from the smelting ore by water smelting method. The mixed solution of ammonia water and ammonium bicarbonate is used as the extracting agent. After mixing with the ore powder, it can be fully stirred for a certain period of time, which can reach more than 90%. The extraction rate, and then the metal solution is heated, decomposed, filtered, dried, and electrolyzed to obtain the extracted metal, especially for the low-grade zinc oxide ore, the method is simple and reliable, the use range is wide, and the cost is low. The extraction rate of the metal of the present invention can reach 90%.

Fourth, recommendations and prospects

When the zinc oxide ore is treated by the beneficiation method, the enrichment and enrichment is difficult and the recovery rate is low. It can be considered that the flotation method cannot directly and effectively recover the zinc oxide. If the metal recovery rate is to be improved, it is recommended to remove the slime before the flotation. It can meet the requirements of increasing the metal recovery rate, and can also greatly reduce the consumption of the zinc oxide ore flotation.

The disadvantage of the acid leaching process of zinc oxide is that the technical conditions of the process are strictly controlled and the technical difficulty is large, mainly because there is a certain amount of silicon in the zinc oxide ore, and the acid leaching is not easy to desiliconize. In order to prevent the harm of silica and increase the leaching rate of zinc, the following two methods can be adopted: one method is to dissolve silicon dioxide in the leachate as little as possible during the ingress and egress, and the other method is that the leaching process is not controlled. The dissolution of silica, but the attempt to remove the silica before gelation, improves the performance of slurry solid separation.

The alkali leaching method has the advantages of high leaching rate and small environmental impact. It can be said that the alkali treatment is an environmentally-friendly and efficient new method for leaching zinc oxide. The process is simple and easy to control, and the energy consumption is low. Recycling, the loss rate of alkali is small, the production cost is reduced compared with the traditional process, and there is no environmental pollution, and it can be comprehensively utilized, which has greater economic and social benefits. However, the current alkaline leaching process is not mature enough. If the product zinc oxide can be obtained simply by the 1-2 step treatment method, the cost will be greatly reduced, and it will also make a greater contribution to the zinc smelting in China.

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