The current status of lead-zinc smelting in China and the direction of technological development

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The Current Status of Lead and Zinc Smelting in China and the Direction of Technical Development 1. Current Status of Lead Smelting Over the past decade, China’s lead smelting industry has developed rapidly. In 2005, the country produced 2.378 million tons of refined lead, an increase of 1.6718 million tons compared to 706,200 tons in 1996. During the same period, the world’s annual lead production increased from 5.785 million tons in 1996 to 7.4688 million tons in 2005, an increase of only 1.6838 million tons. It is evident that over 99% of the increase in global lead production during this time was achieved by China. China’s lead production has increased by an average of 14.9% per year over the past decade, boasting the fastest growth rate in the world. According to statistical data, there are currently over 400 lead smelting plants nationwide. Among them, in 2005, 3 plants had a refined lead production of more than 100,000 tons per year, 8 plants had an annual production of 50,000 to 100,000 tons, and 18 plants had an annual production of over 30,000 tons. Their total production amounted to approximately 1.33 million tons, accounting for 56% of the country’s total refined lead production. See Table 1. Lead produced by China’s traditional lead smelting processes accounts for 85% of the total output. Except for smelters such as Zhuzhou Smelter, Henan Yuguang, Jinli, Yubei, Wanyang, Jiaozuo Dongfang, and Inner Mongolia Lindong, which use sintering machines, the rest use sintering kettles or sintering trays for sintering. There are 4 plants in China that use the ISP process for lead and zinc production via sintering-blast furnace methods, with five production lines in operation; two of these are at the Shaoguan Smelting Plant, and one each at the Baiyin and Huludao Zinc Plants, as well as in Huangzhong County, Qinghai. The sintering-blast furnace lead smelting process is well-established, but it is difficult to recover low-concentration sulfur dioxide emissions. Zhuzhou Smelting Plant has adopted Topsoe acid production technology, while Henan Yuguang Gold and Lead Group, Yubei Metal Smelting Plant, and Jiyuan Wanyang Smelting Group all use non-steady-state acid production technologies. However, due to limitations in processing conditions and equipment, uncontrolled emissions of SO2 and lead dust pollution have not yet been effectively controlled. As for the sintering pot-blast furnace lead smelting process, which is still in use (**its production was banned in 2000**), pollution by SO2 and lead dust is particularly severe. Table 1: List of Chinese enterprises with an annual lead production of over 30,000 tons in 2005
| Serial No. | Enterprise Name | Lead Production (tons) |
|-------------|-----------------|------------------------|
| 1 | Yuguang Jinlian Group | 230,500 |
| 2 | Xuzhou Chunxing Alloy Co., Ltd. | 105,159 |
| 3 | Yubei Metal Smelting | 102,945 |
| 4 | Shuikoushan Non-ferrous Metals Co., Ltd. | 98,288 |
| 5 | Zhuzhou Smelting Group | 96,038 |
| 6 | Wanyang Smelting Group Co., Ltd. | 87,001 |
| 7 | Zhongjin Lingnan | 83,408 |
| 8 | Yunnan Metallurgical Group | 72,950 |
| 9 | Jinchengjiang Chengyuan Smelting Plant | 72,544 |
| 10 | Jiyuan Jinli Iron Smelting Co., Ltd. | 55,000 |
| 11 | Hechi Southern Non-ferrous Metals Smelting Company | 54,329 |
| 12 | Baoding Fengfan Non-ferrous Metals Co., Ltd. | 44,977 |
| 13 | Hubei Jinyang Alloy Co., Ltd. | 44,891 |
| 14 | Honghe Zhenxing Lead Industry Co., Ltd. | 41,500 |
| 15 | Gejiu Shadian Electrosmelting Plant | 40,663 |
| 16 | Anhui Chizhou Non-ferrous Metals Group | 37,087 |
| 17 | Taihe County Hongda Group | 31,140 |
| 18 | Ningxia Nima Metallurgy & Chemical Co., Ltd. | 31,006 |
| Total | | 1,329,426 |

In recent years, as environmental regulations have become increasingly strict, new lead smelting methods have been gradually adopted in China. For example, the ISA process introduced in Qujing, Yunnan, and the Kaldo process adopted by Northwest Mining Corporation have both been put into operation. In particular, the newly developed domestic process of oxygen bottom-blown-blast furnace reduction for lead smelting is being adopted at a rapid pace. In addition to four units in Henan’s Yu Guang Jin Lead Group, Chizhou in Anhui, and Shuikoushan in Hunan that have already been put into operation, Lingye Co., Ltd. in Lingbao, Henan, started up its furnace in August this year, while Yunnan Xiangyun Feilong Industrial Co., Ltd. began operations on September 20. Currently, new projects utilizing this process to build or upgrade existing lead systems are in the stage of schematic design, with three projects namely Chifeng Xingye, Baiyinnuoer Lead-Zinc Mine, and Jiyuan Jinli already at this stage. Four entities are conducting feasibility studies: Chenzhou, Guyang, Guixi, and Shadian. The oxygen bottom-blown-blast furnace reduction lead smelting process (SKS) is a pool melting technology that has been successfully developed in China through nearly 20 years of experimental research. It features low investment costs, good environmental performance, high recovery rates of sulfur and associated metals, and the ability to handle materials with high arsenic content. It holds great competitive advantages for the renovation of existing lead smelters, and is one of the **key environmental protection projects that should be promoted. Once the above 13 projects are completed and put into operation, over half of China’s refined lead from minerals will be produced using this process. With the promotion of several introduced technologies, the environmental conditions in lead smelting in our country will see fundamental improvement. The overall level will be at the world’s leading level. Currently, in the field of lead smelting research, Central South University has made certain progress in the direct lead smelting technology using oxygen-side blowing in a bath furnace in Xinxiang, Henan. Henan Yuguang Gold and Lead Group is conducting experiments on the direct reduction of liquid high-lead slag, and has encountered some engineering challenges, but the process mechanism has been proven to be feasible. In lead refining, China and Japan primarily use electrolytic refining processes; this method ensures stable product quality, results in low amounts of by-products, and makes it easy to recover accompanying elements, making it particularly suitable for processing high-bismuth crude lead. The pyrometallurgical refining method commonly used in Russia, Europe, and the United States has the advantages of lower investment, less lead accumulation during the process, and faster capital turnover. It is worth noting the 100,000 t/a electric lead production facility built and put into operation by Yunnan Metallurgical Group Corporation in Qujing, Yunnan, in 2005. This facility adopted internationally advanced production process technologies and equipment such as large melting pots, large electrolytic cells, large electrode plates, low current density, and long operation cycles. It also introduced from abroad advanced production lines for casting lead anodes using mold placement, automatic equipment for arranging lead cathodes, machines for manufacturing lead cathodes, and DM casting machines for producing starting electrodes. The completion and operation of this project have further narrowed the gap between China’s lead refining industry and world-leading standards in terms of technical equipment and process control, serving as an important model for lead refining production in China. 2. Development trends in lead smelting technology 2.1 Given that China has already adopted processes such as QSL, ISA, and Kaldo, and that Yunnan Tin Group has recently introduced foreign lead smelting processes like Ausmelt, those processes that utilize hot direct injection of pulverized coal for the reduction of high-lead slag present problems related to high dust emissions and large amounts of recycled material, as lead, lead oxide, and lead sulfide all have relatively low boiling points. The oxygen-side blowing melting process researched by Central South University also has the same problem. To reduce the dust emission during the lead reduction stage, both the bottom-blown melting method developed independently in China and the ISA method introduced from abroad utilize liquid high-lead slag slabs along with blast furnace reduction melting. This approach effectively lowers the dust emission during reduction melting, while also achieving high recovery rates for lead, silver, and sulfur. It operates smoothly and is easy to control, which is why the bottom-blown melting method has been rapidly adopted. However, in the reduction of high-lead slag billets using blast furnaces, the latent heat of the liquid slag is wasted. As the price of coke rises, the cost of lead production also increases. Therefore, developing a technology for direct reduction using electrically heated coke with liquid high-lead slag to replace blast furnaces can make full use of the latent heat of high-lead slag, reduce coke consumption and flue gas volume to their theoretical values, thereby significantly lowering the dust emission rate and production costs. This should be an important research and development focus as well as a direction for the advancement of lead smelting technology in China in the future. 2.2 Compared with foreign countries, the majority of lead smelting plants in China are small in scale, have low levels of equipment, low labor productivity, and poor capabilities in comprehensive resource utilization. The future development direction should focus on increasing concentration, expanding enterprise sizes, upgrading equipment levels, and establishing integrated lead-zinc enterprises to take advantage of the complementary strengths of lead and zinc smelting, thereby pursuing a circular economy approach and improving the level of comprehensive resource utilization. 3. The current status of zinc smelting in China: Over the past 15 years, China’s zinc production has grown rapidly, reaching 1.0767 million tons in 1995, 1.957 million tons in 2000, and 2.711 million tons in 2005. From 1995 to 2005, it increased by 9.7% on an average per year ； From 2000 to 2005, it increased by 6.7% on an average per year. As the base volume of zinc production increases, the annual average growth rate has been declining year by year. However, since 2002, China has ranked first in the world in both zinc production and consumption, making it a true major producer and consumer of zinc. In our country, the zinc smelting process is primarily based on wet smelting, with fire smelting being secondary. The standard process for hydrometallurgical smelting is roasting of zinc concentrate → leaching → liquid purification → electrowinning → electrolytic zinc product. Depending on the conditions of the leaching process, it is further divided into low-temperature conventional leaching and high-temperature high-acid leaching. The conventional leaching process is typically represented by Zhuye, where the leaching residues are mostly volatilized in rotary kilns to remove residual zinc. The leaching residues resulting from high-temperature and high-acid leaching are sent directly to waste dump sites for storage. There are four different processes in China for removing iron from such leachates: the xanthozerite method used by factories such as the Baiyin Zinc Smelting Plant, the ammonium aluminate ferric slag method used by factories such as the Chifeng Kubo Hongye Zinc Plant; since the zinc content in these iron slags is low, this method is also referred to as the low-pollution xanthozerite method. The magnetite method is used by companies such as Xiangyun Feilong Industrial Co., Ltd., while the spraying method is employed by factories such as the Wenzhou Smelting Plant – this method is known as the intermediate magnetite method. Based on these differences, the wet zinc smelting process exhibits diversity. Modern smelting plants with a capacity of 100,000 tons per year of electrolytic zinc produced by the wet zinc smelting process have been built and put into operation in Baise, Zhuzhou Iron and Steel, Qujing, Jiyuan, Bayannur, and other locations; two more such plants are under construction. Its equipment and automation levels have reached world-class standards; however, in terms of process operations, there is still a significant gap compared to developed countries in terms of labor productivity and the purity of the processed liquids. Pyrometallurgical zinc smelting: There are three existing pyrometallurgical processes for zinc smelting in China, namely shaft furnace zinc smelting, ISP blast furnace zinc smelting, and electric furnace zinc smelting. A few years ago, zinc smelting was carried out in remote areas using primitive types of furnaces such as trough furnaces, saddle furnaces, square furnaces, or somewhat more standardized flat pot furnaces. Due to their high energy consumption, low recovery rates, waste of resources, and environmental pollution, their use has been **strictly prohibited; such furnaces have now been largely shut down or modified. The last production line for zinc smelting in vertical kilns was shut down abroad as early as 1980. In China, the vertical shaft zinc smelting process is exemplified by the Huludao Zinc Plant. Through years of effort, this plant has developed new technologies such as high-temperature boiling roasting, self-heating sintering furnaces, large-scale distillation furnaces, rectification furnaces, double-layer gas generators, and vortex melting and volatilization furnaces for slag, thereby raising the level of vertical shaft zinc smelting to a new height. It has successively built facilities with a zinc smelting capacity of 200,000 tons per year. However, it has not been widely adopted due to the difficulty in scaling up production capacity for a single series, as well as higher energy consumption and environmental impact compared to wet-process technologies. ISP blast furnace zinc smelting, also known as the Imperial smelting method, produces zinc at the upper part of the furnace and lead at the lower part. Our country has 5 production facilities, which produced a total of 200,000–210,000 tons of zinc last year. This process has unique advantages for treating mixed concentrates of lead and zinc that are difficult to separate. It experienced rapid development in the 1960s and 1970s. With the improvement in technologies for sorting lead-zinc mixed ores, and given the difficulty in addressing environmental issues such as dust pollution from flue gases during the sintering process of lead-zinc concentrates and from the crushing of returned powder, the ISP process is now on the decline. A total of 19 ISP units have been built around the world; in developed countries, several of these units have been shut down for environmental reasons. In 2004, the ISP plants in Kirkcaldy and Clyde in Australia were also closed. Zinc smelting using electric furnaces has seen continuous development over the past decade or so in remote provinces and regions such as Yunnan, Guizhou, Sichuan, Shaanxi, Gansu, Ningxia, and Qinghai – areas that possess zinc ore resources and sufficient electricity supply. This method is favored due to its relatively low investment requirements, short production process, simplicity of operation, and minimal environmental issues. To date, 35 factories across the country have put 58 electric furnaces into operation; the total installed capacity of these furnaces is 112 k·kW, with an annual zinc production of 150,000 to 160,000 tons. Currently, there are 8 more manufacturers, with nearly 40 electric furnaces under construction, boasting a total capacity of almost 120 K·KW. Among them, the more significant ones include the Wenshan Electric Furnace Zinc Smelting Plant in Yunnan, which plans to build 6 4000kVA electric furnaces; Hezhang in Guizhou, which plans to build 10 2000kVA electric furnaces; and Liupanshui, which plans to build 14 3500kVA electric furnaces. The power of the electric furnaces in operation ranges from 1000 to 6300 kVA, and the electrical energy consumption per unit of product varies between 3500 and 4300 kW·H/t of crude zinc, depending on the grade of the concentrate. In addition, several manufacturers such as Liuzhou Zinc Products Factory and Shuikoushan Non-ferrous Metals Company compress zinc calcine into lumps and use Vickers furnaces for reduction and volatilization to directly produce commercial zinc oxide on a considerable scale; the annual output of zinc oxide ranges between 300,000 and 400,000 tons. This should also fall under the category of pyrometallurgical zinc smelting. China’s zinc production over the past decade is shown in Table 2: Table 2 China’s Zinc Production, Unit: 10,000 tons. Year, Item Name: 1995, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005. Zinc content in zinc concentrate: 101.07, 127.31, 147.61, 178.03, 169.32, 162.42, 202.92, 239.1. Zinc metal: 107.67, 148.61, 170.32, 195.72, 203.76, 215.52, 231.85, 271.92, 271.1. Of this, electrolytic zinc accounted for 44.37, 0.86, 81.89, 100.51, 117.81, 124.61, 143.71, 195.1 tons; refined zinc accounted for 32.13, 9.14, 39.79, 55.94, 5.95, 9.75, 6.27, 70.37 tons; distilled zinc accounted for 5.56, 6.52, 7.71, 4.42, 7.21, 1.71, 1.79, 1.82 tons. Other zinc products accounted for 25.73, 32.02, 40.93, 33.48, 32.82, 29.43, 30.24, 40.7 tons. Except for electrolytic zinc, all the products listed in Table 2 are obtained through pyrometallurgical methods. In 2004, electrolytic zinc accounted for 1.951 million tons, representing 71.8% of total zinc production that year; zinc produced by ISP blast furnaces accounted for 210,000 tons, or 7.7%; zinc produced by electric furnaces accounted for 160,000 tons, or 5.9%. The remaining zinc was produced using vertical shaft furnaces, amounting to approximately 350,000–360,000 tons, or 13% of total production. As shown in Table 2, the output of electrolytic zinc in 1995 accounted for only 41% of the total output that year, but by 2004 it had risen to nearly 72%, indicating that the development pace of wet-process zinc smelting is much faster than that of fire-process zinc smelting. In 2005, the enterprises in China that produced more than 30,000 tons of zinc per year are listed in Table 3: Table 3 Enterprises in China with an annual zinc production of over 30,000 tons in 2005. Unit: 10,000 tons. Ranking, Enterprise Name, Zinc Production: 1. Zhuzhou Torch Metal Co., Ltd. – 32.68; 2. Huludao Non-ferrous Metals Group – 24.56; 3. Zhongjin Lingnan – 18.14; 4. Baiyin Non-ferrous Metals Company – 13.11; 5. Yunnan Metallurgical Group – 10.37; 6. Hanzhong Bayi Zinc Industry Company – 7.24; 7. Shuikoushan Non-ferrous Metals Company – 6.94; 8. Sichuan Hongda Group – 8.69; 9. Shaanxi Dongling Zinc Industry Company – 6.69; 10. Xiangyun Feilong Industrial Company – 5.09; 11. Yuguang Gold and Lead Group – 5.00; 12. Chifeng Kubo Hongye Zinc Industry Company – 4.97; 13. Liuzhou Huaxi Group – 4.51; 14. Yunye Zinc Industry Company – 4.11; 15. Yunnan Jinding Zinc Industry – 4.61; 16. Sichuan Huidong Lead-Zinc Mine – 4.53; 17. Hunan Sanli Group – 4.05; 18. Shanxi Xiangfen Non-ferrous Metals Company – 3.91; 19. Shaanxi Zinc Industry Company – 3.41; 20. Western Mining – 3.30; 21. Xikangshan Shansing Tiye Company – 3.23; 22. Gansu Chengzhou Mining – 3.10. The total production of these enterprises was 182.2 tons, while the national total was 271.1 tons. These enterprises accounted for 67.2% of the total national zinc production. Source: **National Bureau of Statistics, China Non-ferrous Metals Industry Association. Technological advancements in zinc smelting in recent years: In the 1990s, with the construction of zinc smelting plants with a capacity of 100,000 tons per year, advanced equipment such as large-scale boiling furnaces with a surface area of 109 m2, waste heat boilers, leachate boiling coolers, high-efficiency cooling tanks, 150 m3 high-efficiency energy-saving mixing tanks, fully plastic large-scale electrolytic cells, mechanized zinc stripping machines, 40-ton large-scale low-frequency induction furnaces for zinc melting, and automatic casting, stacking, and packaging machines were adopted and developed. Additionally, technologies such as three-stage deep purification of antimony salts were utilized, enabling China’s wet-process zinc smelting technology to reach the world’s leading level. The latest developments include: 1) Yunnan Metallurgical Group and Kunming University of Science and Technology have jointly developed a new automatic catalytic pressure leaching process for high-iron zinc concentrate, designed to process concentrate containing 42.17% Zn, 14.38% Fe, and 29.28% S. The results of industrial-scale continuous tests showed an zinc leaching rate of 98.05%, an iron leaching rate of only 29.22%, and a sulfur conversion rate of 92.2%. This technology has enabled the construction and operation of a zinc electrowinning production line with an annual capacity of 10,000 tons, entering the industrialization stage. This process features a short flow sequence, as it combines multiple steps of conventional wet zinc smelting such as roasting, waste heat boiler use, dust collection, acid production, leaching, and slag treatment into one or two stages of pressurized leaching, resulting in a simplified process. Furthermore, this process produces elemental sulfur directly, avoiding the emission of exhaust gases resulting from the production of acid from roasted flue gas, as well as the environmental pollution caused by residual SO2 and acid mist. It is a clean process, and it offers even greater advantages for setting up plants in areas where there is no demand for sulfuric acid. 2) Significant progress has been made in recent years regarding the processing of high-silicon zinc oxide ore. Yunnan Xiangyun Feilong Industrial Co., Ltd. has developed a method in which high-silicon zinc oxide ore is mixed, in appropriate proportions, with the intermediate-temperature and medium-acid leaching residues from sulfide ore concentrates; subsequent high-temperature and high-acid leaching, iron removal using the magnetite method, silicon removal, liquid purification, and electrolysis are carried out to produce zinc metal – a process for which a **patent has been obtained. The plant has been using the aforementioned process for many years, achieving a total zinc recovery rate of 94% ±. By 2005, the plant’s zinc oxide production had exceeded 50,000 tons per year, demonstrating that this process is mature and reliable. It has opened up new ways for the economic and efficient utilization of high-silicon zinc oxide ores that are difficult to process in China. 3) As the price of indium exceeded 10 million yuan per ton, the value generated by one kilogram of indium was equivalent to that of one ton of zinc. The effective recovery of indium, an associated metal in zinc ores, has attracted great attention from the zinc smelting industry, and two research outcomes have been applied in industrial design. First, in the high-temperature and high-acid process for the hydrometallurgical treatment of jarosite, the intermediate leach residue is not sent directly to high-acid leaching; instead, it is pre-neutralized using smoke dust and high-acid leach solution. The supernatant resulting from this pre-neutralization is used for alum precipitation, while the bottom stream after pre-neutralization is then sent to high-acid leaching. The supernatant from the precipitation process is returned to the neutral leaching process, while the iron aluminate residue contains the majority of the indium, which is used as a raw material for indium extraction. With the improved leaching process, the total recovery rate of indium exceeds 70%, and indium-zinc smelters with a capacity of 50 t/year of indium and 50,000 t/year of zinc are being built in China using this process. 4) Another research achievement relates to the pyrometallurgical zinc smelting process: after desulfurization roasting of indium-zinc concentrate, the roasted ore is fed into an electric furnace for reduction and volatilization; the volatiles are condensed through zinc rain to yield crude zinc, which is then distilled to produce refined zinc. Indium remains in the distillation residue, namely hard zinc, and indium is recovered from this hard zinc through vacuum smelting. In this process, the volatilization rate of indium in the electric furnace is >90%, and the overall recovery rate of indium reaches 80%. A demonstration plant with an annual production capacity of 30,000 tons of zinc and 20 tons of indium is currently being built in China. 4. Development Discussion: China is a major producer and consumer of zinc smelting products, but not a leading country in this field. Like other non-ferrous metals, there are some common issues; without effective countermeasures, their development will be difficult to sustain. 1) With the rapid growth of zinc consumption in the domestic market, it is necessary to pay attention to the development and utilization of zinc resources abroad. Our country was originally a major producer of zinc resources, and in the last century it exported large quantities of zinc concentrate, metallic zinc, and alloys. As can be seen from Table 4, since 2001, the import volume of zinc concentrate has exceeded its export volume, and since 2003, the trade balance for zinc has shifted from a surplus to a deficit. Since 2004, the import volume of zinc and zinc alloys has exceeded its export volume. By the end of 2005, the total smelting capacity, including zinc production, had reached 4 million tons per year ±, whereas zinc output that year remained at the same level as in 2004 with a slight decline (see Table 2), mainly due to restrictions on imported concentrate. Table 4: Apparent consumption of zinc in China and its foreign trade situation
Year | Item
2000 | 2001 | 2002 | 2003 | 2004 | 2005
Apparent consumption (10,000 t) | 128.5 | 151.2 | 187.1 | 214.6 | 288.5 | 321.9
Zinc concentrate (10,000 t) | Imports: 7.79 | 65.29 | 78.47 | 74.56 | 61.61 | 56.78 | Exports: 13.89 | 1.34 | 0.35 | 0 | 0 | 0
Zinc, zinc products, zinc alloys (10,000 t) | Imports: 18.13 | 22.26 | 21.23 | 1.14 | 76.21 | Exports: 61.15 | 7.52 | 49.64 | 8.42 | 8.01 | 4.7
Foreign trade value (10,000 USD) | Import value: 23,200.1 | 37,878.2 | 49,191.2 | 57,816.6 | 83,252.0 | 119,222.5 | Export value: 73,439.3 | 61,575.6 | 49,276.2 | 51,393 | 89,622.2 | 34,309.9
Trade surplus: 50,239.2 | 23,697.48 | 5 | -6,802.7 | -44,289.8 | -84,912.6
The enthusiasm for building domestic zinc smelting plants remains high; this year, more than 200,000 t/year of smelting capacity was put into operation. The growth in zinc mining and processing capacity in the country fails to keep up with the increase in smelting capacity, and the volume of imported concentrate is also restricted by the international market. Insufficient raw material supply has become a bottleneck for the growth of zinc smelting capacity in our country. To change this situation, relevant departments and enterprises must focus on developing zinc mining resources abroad. According to statistics from 2005, China’s domestic zinc reserves amounted to only 20.95 million tons, with underlying reserves at 32.5 million tons. At the current pace of production and development, domestic zinc resources can only meet demand for another 7 to 8 years. If we do not pay attention now, a strategic resource crisis regarding zinc will arise in the near future. 2) Paying attention to the recycling of renewable resources is an effective way to address the shortage of zinc resources in our country. In our country, the recycling of waste metals such as copper, lead, aluminum, and tin has received a certain degree of attention from relevant authorities and enterprises. However, insufficient attention is still given to the recycling of zinc as a secondary resource; it operates on a voluntary basis without the development of an industry around it. According to the \"Compilation of Non-ferrous Metals Data,\" China’s recycled zinc production over the past 5 years is shown in Table 5. Table 5: China’s production of recycled zinc and its proportion from 2000 to 2005
Year: 2000, 2001, 2002, 2003, 2004, 2005
Production of recycled zinc (10,000 tons): 7.00, 6.97, 2.09, 3.24, 4.48, 8.5
Proportion of total production for that year: 3.5%, 3.4%, 2.09%, 1.40%, 1.65%, 3.14%
Due to the difficulties in collecting accurate statistics, the figures in Table 5 may not be precise; however, it is clear that the level of utilization of recycled resources is quite low. From 2004 to 2005, China’s apparent zinc consumption averaged 3 million tons per year. The proportion of its consumer industry is shown in Table 6. In these industries, zinc usage in galvanizing and dry cell manufacturing has exceeded 50%, and the scrap metals generated are not effectively recycled. Table 6: Percentage of zinc used in various consumption industries %; Percentage of industries using zinc in total zinc consumption: Galvanizing industry – 40%, Die-casting industry – 16.9%, Copper-zinc alloy industry – 15.2%, Dry battery industry – 13.2%, Zinc oxide-based chemical coatings industry – 11.4%, Zinc processing industry – 1.5%, Other industries – 1.7%. In developed countries, the recycling rate of secondary zinc resources has reached 30% of total zinc production. The United States has over 80 electric arc furnace steel mills that process used galvanized steel, generating dust containing Zn, Pb, and Cd. Through further enrichment and separation, this dust is used as raw material for the production of these metals, thereby effectively increasing the recovery rate of secondary metals such as zinc. Currently, there are about 50 recycled zinc recycling plants in the world, whose production accounts for 10% of the world’s total zinc production. The recovery of zinc from dry batteries is still in the research phase in China. It is reported that Japan and South Korea have already built plants for the recycling of dry batteries capable of producing over 5,000 tons of zinc per year. Secondary zinc resource recycling **must receive high attention from the relevant authorities. Firstly, the scrap materials of galvanized steel, which use the most zinc, need to be collected together and sent to specialized steel mills where zinc can be effectively recovered. Secondly, it is necessary to accelerate research efforts in order to develop an economically viable recycling process for used dry batteries as soon as possible. Apart from zinc oxide coatings, which are difficult to recycle, valuable metals in materials such as zinc, die-casting alloys, and copper-zinc alloys can be easily recovered as long as proper collection is ensured. If the secondary metal recycling rate of zinc reaches 30% of its consumption, it means that our country can recycle 900,000 tons of zinc per year, which will greatly alleviate the pressure on zinc resources. 3) Expanding the scale of enterprises is necessary to improve the overall level of comprehensive resource utilization. In China, there were several hundred zinc smelting enterprises a few years ago; alone, there were nearly 40 electro-smelting zinc plants, with the average annual zinc production per enterprise being less than 10,000 tons. There are five companies in the country that produce over 100,000 tons of zinc per year, with Chuzhou Smelting being the largest, producing 300,000 to 330,000 tons of zinc per year. Large enterprises such as Zhuye have a relatively high level of comprehensive resource utilization. It is difficult for small zinc plants to economically and efficiently recover the associated metals in zinc resources comprehensively, resulting in resource waste. Zinc companies abroad are relatively large in scale; the top ten lead-zinc companies in the world control 48.7% of the world’s total lead concentrate production and 43% of its total zinc concentrate production. The zinc production capacity controlled by GCL Group amounts to 640,000 t/a ； Umicore’s zinc production reaches 650,000 t/year ； Korya Lead Company’s lead and zinc production capacity reaches 900,000 tons per year, making it the world’s largest zinc refining company. These companies have a higher level of comprehensive utilization of zinc resources than the current level in our country. The development direction of zinc smelting in our country should also involve a moderate reduction in the number of zinc-related enterprises, an expansion of their scale, an improvement in labor productivity, and an enhancement in the level of comprehensive resource utilization, so as to gain a competitive edge in the international market and become a leading country in zinc production. 4) From a technical perspective, promoting the atmospheric pressure oxygen impregnation process deserves attention. Atmospheric pressure oxygen leaching shares the advantages of pressurized oxygen leaching; it enables the production of elemental sulfur, with an extraction rate for zinc exceeding 98%. It also overcomes the drawback associated with pressurized oxygen leaching, namely the tendency for material sticking to occur inside the reactor and in the pulp pipelines due to elemental sulfur. Additionally, its investment cost is lower than that of pressurized oxygen leaching technologies of similar scale, making it known as a new third-generation zinc smelting technology. It could also become the preferred technology for the promotion and application of zinc smelting in our country in the future.