The total reserves of iron ore in China are about 46.232 billion tons (excluding Taiwan Province), of which the reserves above Grade C are about 22.031 billion tons [1,2], accounting for about 17.86% of the world’s total reserves. The characteristics of iron ore in China are:
(1) There are many poor mines and few rich mines. The average grade of the ore is low, with poor ore accounting for 97.5% of the total reserves and rich ore entering the furnace accounting for only 2.5%.
(2) The type of ore is complex, with many oxidized ore, multi metal coexisting ore, and difficult to select ore, and the embedded particle size is fine. Therefore, almost all mined ores need to undergo beneficiation treatment to improve the grade of smelting raw materials and the comprehensive utilization of useful components. Entering the 21st century, mineral resources, as an important national strategic resource and an important basic raw material for social and economic development, play a crucial role in national economic construction, national defense technology construction, and other aspects. With the rapid growth of China’s steel production, the demand for iron raw materials for blast furnace smelting has increased significantly, and the requirements for quality have also become increasingly high. Iron ore is facing enormous opportunities and challenges, and should have great potential. However, the grade of domestic iron ore is getting lower and lower, and the requirements for iron concentrate grade in blast furnace ironmaking are becoming increasingly strict. The continuous import of high-quality foreign iron ore is strongly impacting the domestic iron ore market. To survive in this situation, Iron Mine must strengthen its own technological transformation, connect with the actual situation of the mine in mining management, mining technology, and other aspects, continuously explore, actively cooperate with higher education institutions and research institutes, and strengthen the development and application of new technologies.
It is gratifying that in recent years, with the active efforts of mineral processing workers in China, a number of mineral processing technology achievements have been ranked among the world’s advanced levels, greatly promoting the development of productivity and supporting the development of the national economy, continuously exploring, seizing opportunities, and daring to challenge.
1. Significant breakthroughs have been made in mineral processing technology
At present, the main types of iron ore processed by domestic beneficiation plants are magnetite and hematite, with magnetite concentrate production accounting for about 3/4 of China’s iron concentrate production. Moreover, most domestic iron mines mainly focus on these two types of ores in terms of beneficiation technology innovation.
1.1 Progress in magnetic ore beneficiation process
China has relatively abundant iron ore resources, second only to countries such as Russia, Canada, Australia, and Brazil in terms of reserves. Among the iron ore resources, Anshan style iron ore is the most widely distributed and the most important iron ore deposit in China. Its reserves account for more than half of the total iron ore reserves in the country, and its scale is generally relatively large. Its ore type is mainly magnetite, which is currently the main selected ore type for domestic iron ore dressing plants. The representative new processes that have emerged in recent years are mainly “stage grinding, weak magnetic separation reverse flotation process”, “full magnetic separation separation process”, and “ultra fine crushing wet magnetic separation tailings disposal process”.
1.1.1 Stage grinding, weak magnetic separation – reverse flotation process
Due to the fine particle size of the magnetite currently selected in China, the negative impact of magnetic agglomeration in beneficiation is becoming increasingly apparent, making it increasingly difficult to improve the concentrate grade relying on a single magnetic separation method. Combining magnetic separation with anionic reverse flotation can achieve complementary advantages in the beneficiation process of magnetite, which is beneficial for improving the concentrate grade of magnetite beneficiation. The stage grinding, weak magnetic separation and reverse flotation process is one of the more effective processes for increasing iron and reducing silicon in iron concentrate in China. The cationic reverse flotation process is adopted in Angang Gongchangling Concentrator. The final concentrate is obtained through one roughing and one cleaning. The reverse flotation foam is reground after concentrated magnetic separation. The reground product is discarded after the dewatering tank and multiple sweeping magnetic separation. The magnetic separation concentrate is returned to the reverse flotation operation for re separation. The iron grade of the concentrate is increased from 64% to 68.89%, the SiO2 content in the concentrate is reduced to below 4%, and the iron recovery rate is above 98%. Taiyuan Iron and Steel Jianshan Iron Mine adopts an anionic reverse flotation process, which is subjected to efficient flotation agents for one rough selection, one selection, and three sweeps. Before the transformation, the concentrate grade was about 65.5%, and the SiO2 content was about 8%. After the transformation, the concentrate iron grade was above 68.9%, and the SiO2 content was below 4%. The reverse flotation recovery rate was about 98.5%, and the physical and chemical properties of the concentrate slurry met the requirements of long-distance pipeline transportation.
1.1.2 Full magnetic separation process
The full magnetic separation process is based on the existing stage of grinding, weak magnetic separation – fine screen re grinding and re separation process, and is selected using high-efficiency fine screen and high-efficiency magnetic separation equipment. Compared with the reverse flotation process, this process is simple, reliable, investment saving, short construction period, and easy to operate. The selected ore from the Shougang Mine Dressing Plant belongs to the Anshan style lean magnetite, with a strip-shaped and gneissic structure. The metal spinning aluminum minerals are mainly magnetite, with a small amount of hematite. The full magnetic separation process has been applied in the Shougang Mine Dressing Plant for many years, and its iron concentrate grade has been maintained at around 67%, winning the national championship in iron concentrate quality . The full magnetic separation process with high-frequency vibrating screen, BX magnetic separator, magnetic separation column, and disc filter as the main equipment in China was first adopted at the Nanfen Concentrator and Waitoushan Concentrator of Benxi Iron and Steel Co., Ltd. This process has accurate entry points and few openings, which is both reasonable and economical for optimizing the overall process flow and achieving the ultimate goal of reducing silicon and increasing iron content. The application results show that the iron grade of the concentrate can be increased to about 69.5%, the SiO2 content in the concentrate can be reduced to below 4%, the tailings grade and metal recovery rate remain basically unchanged, and the newly added processing cost is less than 20 yuan/t.
1.1.3 Ultra fine crushing – wet magnetic separation tailing process
This process involves finely crushing the ore to a size of 5mm or less, and then using a permanent magnet medium field strong magnetic separator for wet magnetic separation and tailings disposal. This process is of great significance for energy conservation and consumption reduction, effective utilization of extremely poor iron ore, and improving the quality of the final iron concentrate. In order to develop and utilize iron ore with a grade of less than 20%, Masteel Gaocun Iron Mine used a high-pressure roller mill to finely crush the ore to below 3mm, and a field strong wet magnetic separation to remove about 40% of coarse tailings. The iron grade of the raw material was increased to about 40%, and the final iron concentrate was obtained after re grinding and re selection. The final iron concentrate grade of this process reached over 65%, the SiO2 content decreased to below 4%, and the tailings grade was below 10%. In addition, Shandong Laiwu Iron Mine, Jinling Iron Mine, etc. adopt the hammer crusher wet permanent magnet field high intensity magnetic separation process, with a particle size of -5mm accounting for over 80% of the selected materials, which can remove coarse tailings with a production rate of about 30-40%. [next] 1.2 Progress in red ore beneficiation process
China has a large reserve of red ore resources with poor washability, mainly distributed in Liaoning, Hebei, Gansu, Anhui, Inner Mongolia, Henan, Hubei, Shanxi, Guizhou and other places. The domestic easily beneficiated magnetite resources are facing an increasing shortage, with a clear shortage of backup magnetite mines. Most of the relatively easily beneficiated red iron ore mines have entered a deep mining period, with mining costs increasing year by year. Red ore beneficiation has always been a major challenge in China’s beneficiation industry. In recent years, Chinese beneficiation technology workers have persistently carried out beneficiation research and developed new beneficiation reagents, processes, and equipment based on the specific characteristics of red ore. This has made significant breakthroughs in China’s red ore beneficiation technology, and the process technical indicators have reached the international advanced level. 1.2.1 Continuous grinding magnetic separation flotation combined process
After studying and comparing processes such as “continuous grinding, weak magnetic strong magnetic anionic reverse flotation process”, “continuous grinding, weak magnetic strong magnetic acidic positive flotation process”, “stage grinding, gravity separation magnetic separation acidic positive flotation”, “continuous grinding, weak magnetic strong magnetic cationic reverse flotation process”, etc., the “continuous grinding, weak magnetic strong magnetic anionic reverse flotation process” was determined based on experimental results, The process has a reasonable and compact structure, strong adaptability to changes in ore properties, and stable production. After the renovation of the Diaojuntai beneficiation plant based on this process, the concentrate grade was over 67.59%, tailings grade was 10.56%, and metal recovery rate was 82.24% at a raw ore grade of 29.60%. At present, in addition to the Diaojuntai Beneficiation Plant, Qidashan Beneficiation Plant and Donganshan Sintering Plant have completed technical transformation according to this process. The Sijiaying Beneficiation Plant, Wuyang Red Iron Ore Beneficiation Plant, and Gongchangling Red Iron Ore Beneficiation Plant have started construction according to this process and have made significant progress. Based on this process, the red iron ore dressing plants of Guanmen Mountain and Hujiamiao are also being planned and constructed.
1.2.2 Stage grinding gravity magnetic separation flotation combined process
Since 2001, Qidashan Concentrator has adopted the stage grinding, gravity concentration strong magnetic anion reverse flotation process instead of the stage grinding, gravity concentration strong magnetic acid positive flotation process in the first concentration workshop, and the roasting magnetic separation process in the second concentration workshop. The concentrate grade in the first concentration workshop has increased from 63.60% to 66.21%, and the concentrate grade in the second concentration workshop has increased from 63.26% to 66.80%, At present, the iron concentrate grade of the entire beneficiation plant has been stable at over 67% since April 2004, and the tailings grade has also decreased from 12.5% to 11.14%. SiO2 has decreased from 8% to below 4%, and the iron concentrate grade has increased by 3.8 percentage points compared to before the renovation. The tailings grade has decreased by 1.36 percentage points, and the first grade product rate has reached over 99.80%. The Donganshan Concentrator of Ansteel also adopted this process to obtain technical indicators such as concentrate grade of 64.49% and metal recovery rate of 76.11%.
1.2.3 Strong magnetic reverse flotation roasting combined process Currently, the reduction roasting magnetic separation process for red iron ore in China is not widely used due to its high cost and low grade of iron concentrate. This process is mainly suitable for iron ore with high burning loss such as limonite and siderite. Due to the low theoretical grade of this type of iron ore, iron concentrate with low impurity content can be obtained through strong magnetic reverse flotation, and then the iron grade of the product can be greatly improved through ordinary roasting or production of pellet ore, which is still a high-quality ironmaking raw material. The experimental research results of Ma’anshan Mining Research Institute on iron ores such as Jiangxi Tiekeng limonite show that the iron grade of roasted products can reach over 65%. Compared with the combined process of roasting, magnetic separation, and reverse flotation, the production cost is significantly reduced, making this type of iron ore have economic mining and utilization value.
2. Significant progress has been made in mineral processing equipment
In recent years, the improvement of China’s iron ore beneficiation process level has been supported by new beneficiation equipment and advanced foreign equipment, especially in the development or introduction of many new and efficient equipment in crushing, grinding and classification, separation (including gravity separation, magnetic separation, flotation, etc.), dehydration, filtration, etc., which have been successfully applied, providing equipment guarantee for the progress of beneficiation technology.
2.1 Crushing equipment
For decades, China’s metal spinning copper mines have been working hard to save energy, reduce consumption, and improve economic efficiency, with the basic principle of “more crushing and less grinding”. The progress of crushing equipment is mainly reflected in the development and application of innovative and practical crushing equipment such as new external moving jaw evenly swinging jaw crushers, double cavity jaw crushers, double cavity rotary crushers, and impact jaw crushers. However, there is still a certain gap in technology and effectiveness between these equipment and imported crushing equipment from abroad. High efficiency cone crushers from foreign companies such as Metso and Sandvik reduce the average final crushing particle size by 5-8mm. The high-pressure roller press that has been developed domestically and can replace fine crushing and one stage of rough grinding is currently undergoing industrial testing at mines such as Masteel Nanshan Mining Company. In addition, column mills are currently also used in some mines in China. This type of equipment has a large energy-saving and consumption reduction range, which can increase the system’s output by more than 30% -50%. Moreover, the equipment has a high operating rate and little impact on the environment.
2.2 Grinding equipment
Due to the fact that ball mills are mature equipment with many advantages, research on grinding equipment mainly focuses on energy conservation and mill liners. The energy conservation and consumption reduction of mills are mainly reflected in the specifications of grinding equipment, grinding media, equipment structural performance, and the configuration of grinding equipment and process flow. The development of mill liners has gone from metal liners (manganese steel, high chromium alloy steel, hard nickel alloy, etc.) to non-metallic liners (rubber liners), and then to magnetic liners . The use of magnetic liners can make the mill load small, have a long service life, and have low noise. Magnetic liners have been successfully applied in enterprises such as Bensteel’s Waitoushan Iron Mine, Ansteel’s Qidashan Concentrator, and Baosteel’s Concentrator, achieving significant economic benefits. In addition, there has been some progress in the research of automatic control of grinding and grinding aids.
2.3 Fine particle screening and grading equipment
In recent years, by continuously introducing and digesting advanced technologies from abroad, China’s fine particle screening and grading equipment has reached international level. MVS high-frequency vibrating screen is widely used in the process of improving the quality and reducing impurities of iron concentrate in metallurgical mines in China. It has been successfully applied in mining enterprises such as Shougang beneficiation plant, Bengang beneficiation plant, Ansteel beneficiation plant, and Wuhan Iron and Steel beneficiation plant. Production practice has proven that using this fine screen instead of traditional nylon fine screen can increase the screening efficiency from less than 30% to 50% or higher, significantly improving the efficiency of the regrinding machine, and saving energy while improving the quality and impurities of iron concentrate. In addition, GYX31-1207 high-frequency vibrating fine screen can effectively improve the grade of iron concentrate. The equipment has good mechanical performance, good screening efficiency, and a longer service life of the screen. It has been successfully applied in Heishan Iron Mine. The new inclined narrow flow classification equipment has the characteristics of large production capacity per unit area, high classification efficiency, high cost-effectiveness, and wide application range in the classification process. At present, it has been effectively applied in the Huangmaoshan Concentrator of Yunxi Company and the Yunnan Yancang Lead Mine. The American Derek high-frequency fine screen has also been applied in China’s magnetite beneficiation plants. After using this fine screen instead of ordinary nylon fine screen, Laiwu Mining Company and Lunan Mining Company increased the raw ore processing capacity by more than 25% and the concentrate grade by nearly 1 percentage point.
2.4 Magnetic Separation Equipment
The development of magnetic separation equipment in China is relatively fast, from weak to strong magnetism, from electromagnetism to permanent magnetism, and from dry to wet. People have done a lot of research work and made great progress, resulting in a batch of high-level magnetic separation equipment. At present, the magnetic separation equipment developed and developed in China mainly includes: a. Wet weak magnetic separation equipment, typical of which include φ 1050 series permanent magnet cylindrical magnetic separator, LP series vertical disc permanent magnet separator, BX series new high-efficiency permanent magnet separator, BK series dedicated permanent magnet separator, YCMC series permanent magnet pulsation magnetic separator, magnetic separation column, etc; b. Permanent magnet bulk ore dry magnetic separator, representative of CTDG series permanent magnet bulk ore dry magnetic separator; c. Medium magnetic field permanent magnet cylindrical magnetic separators, representative of which are ZC and WCT series medium magnetic permanent magnet cylindrical magnetic separators. d. High intensity magnetic separators mainly include CS series induction roller type high intensity magnetic separators, Shp series flat ring type high intensity magnetic separators, Slon series vertical ring pulsation high gradient high intensity magnetic separators, DPMS series open gradient permanent magnet high intensity magnetic separators, YCG series coarse grained permanent magnet roller type high intensity magnetic separators, etc.
2.5 Magnetic – gravity separation equipment
At present, significant progress has been made in composite force beneficiation technology. The magnetic gravity separation equipment developed and applied mainly includes magnetic separation columns , magnetic agglomeration gravity separators, low field strength self heavy medium jigs, CSX series magnetic field screening machines, etc. Their characteristic is a composite force field, which includes gravity and hydrodynamic forces in addition to magnetic force, and is a combination of magnetic and gravity separation. Various forces complement each other, thereby improving the selectivity of sorting. These equipment are now being applied in practical production, among which magnetic separation columns and magnetic agglomeration gravity separators are widely used.
The Nanfen and Waitoushan beneficiation plants of Benxi Iron and Steel Company use magnetic separation columns to improve the quality and impurities of magnetic concentrate. The iron grade of the concentrate can be increased to over 69%, and the SiO2 content in the concentrate can be reduced to below 4%. The recovery rate of the concentrate can reach 98.57%. The Tongban Shigou Iron Mine beneficiation plant uses 8 Φ 600 magnetic separation columns to increase the concentrate grade from the original 65.5% to 67.48%. The Baogang beneficiation plant uses magnetic separation columns to process weak magnetic separation concentrate in industrial analysis experiments, and the concentrate grade is increased from 61% to 65%, and the SiO2 content is reduced from 3.5% to 2.13% . The concentrator of Ekou Iron Mine at Taiyuan Iron and Steel Group Co., Ltd. uses a variable diameter magnetic agglomeration machine to treat the ore with extremely fine embedded particle size in the northern area, and the grade of the iron concentrate has increased from 63.88% to 66.01%. The research results of using electromagnetic concentrators instead of ordinary permanent magnet concentrators in the beneficiation plant of Shougang Water Plant have shown that the grade of iron ore concentrate can be increased by more than 2 percentage points, and it also indicates that the particle size of coarse beneficiation can be increased .
2.6 Flotation equipment
Flotation equipment is widely used in iron ore beneficiation operations. Currently, various types of flotation machines are widely used in China, including self aspirated mechanical stirring, aerated mechanical stirring, and aerated types. Research on flotation machines mainly focuses on the structure of the flotation machine tank, impeller shape, impeller speed, impeller diameter, stator, and other aspects. The commonly used flotation machines include XT series flotation machines, BF series flotation machines, JJF series flotation machines, CF series flotation machines, etc. In recent years, the relatively new ones mainly include XTB rod flotation machines, as well as fine particle parallel flow flotation machines and XPM type jet flotation machines. In addition, academician Yu Yongfu from the Chinese Academy of Sciences, who was originally widely used in the coal industry, successfully applied the most advanced micro bubble type “flotation column” to iron ore cations for the first time in China. Recently, a successful industrial experiment was conducted at Anshan Iron and Steel Company, which not only greatly simplified the process flow, but also selected iron ore with higher purity.
2.7 Filtration and dehydration equipment
In recent years, there have been significant breakthroughs in filtration and dehydration equipment. New filtration and dehydration equipment mainly includes disc vacuum filters, filter presses, ceramic filters, and the latest research and development includes membrane filtration technology. The disc vacuum filter is optimized and designed for the characteristics of high density, fast settling speed, and high viscosity of metal spinning stainless-steel. It has the characteristics of sturdy and reasonable structure, smooth operation of the filter disc, automatic speed regulation and strong mixing, reliable shaft end sealing, and no leakage of mineral slurry. At present, nearly a hundred beneficiation plants have replaced the original filter with over 300 disc filters, significantly improving the filtration indicators. The ceramic filter utilizes the micropores on the ceramic plate to generate capillary action, and the liquid enters the micropores on the ceramic plate through capillary action without external force. Under the negative pressure generated by the vacuum pump, the solid and liquid are separated. The use of ceramic filters in the Donganshan Concentrator of Angang Iron and Steel shows that compared to the cylindrical internal filter, the filtration equipment coefficient has increased from 0.227t/(m2. h) to 0.757t/(m2. h), and the water content of the filter cake has decreased from 13.48% to 9.41%. At present, Donganshan Concentrator has replaced the original cylindrical internal filter with 50% ceramic and 50% disc filter equipment.
3. Mineral processing reagents are constantly updated
The progress of beneficiation reagents has played an important role in the development of China’s iron ore beneficiation process, especially in the work of increasing iron and reducing silicon. The iron ore flotation reagents developed domestically mainly include collectors and inhibitors, which are divided into three categories: anionic collectors, cationic collectors, and chelating collectors. In recent years, mineral processing workers in China have mainly modified and mixed fatty acids and petroleum sulfonates to significantly improve their selectivity and collection capacity, especially in the field of anionic reverse flotation collectors. The new high-efficiency anionic collectors SH-37, MZ-21, and RA-515 have been successfully applied in red iron ore dressing plants such as Angang Diaojuntai Dressing Plant, Qidashan Dressing Plant, and Donganshan Sintering Plant. The iron concentrate grade has reached over 66% to 67%, and the reagent cost per ton of concentrate has been reduced by more than 15%. The adaptability to temperature has been enhanced, and the economic benefits are significant. The new high-efficiency collectors MD-28 and MH-80, which are used for improving the quality and impurities of magnetite concentrate, have been promoted and applied in Lunan Mining Company and Taiyuan Iron and Steel Jianshan Iron Mine, respectively. The grade of magnetite concentrate has been increased to over 69%. The newly developed MH-88 special collector was used to separate the lean hematite ore from Tieshanmiao in Wuyang, achieving a good indicator of iron concentrate grade of over 65% and metal recovery rate of 72.56%.
Cationic collectors are mainly amine collectors used for flotation of siliceous minerals, including fatty amines and ether amines. There are not many mineral processing plants in China that use amine collectors, and there are few types of reagents, mainly consisting of twelve carbon fatty amines and mixed amines. Angang Gongchangling Concentrator has adopted a new type of cationic collector YS-73. In addition, the new cationic collector GE-601 developed by Wuhan University of Technology has the characteristics of low temperature resistance and high efficiency. It can not only solve the problem of dodecylamine, but also directly dispose of the tail without the need for magnetic separation, thereby simplifying the process flow.
Chelating collectors can form stable chelates with metal ions on mineral surfaces, and their selectivity is significantly improved compared to fatty acid collectors. The application of water-soluble carboxymethyl starch in industrial production at Anshan Iron and Steel’s Diaojuntai Concentrator greatly simplifies the preparation process of reagents and reduces production costs, with an annual profit of over 3 million yuan. The special desulfurization activator MHH-1 for iron concentrate has a significant effect on removing sulfide ore, especially pyrrhotite with strong magnetism and poor floatability. Compared with other activators, MHH-1 has the characteristics of low dosage, low cost, and obvious desulfurization effect. Currently, this product has been successfully applied in multiple mines. Therefore, the development of this product provides a new way for improving iron and reducing sulfur in iron concentrate.
4. The development direction of beneficiation technology in China’s iron mines Although some of China’s iron ore beneficiation technology and concentrate quality have reached international advanced levels, the characteristics of poor, miscellaneous, fine, and diverse types of iron ore in China, as well as the new requirements of the steel industry for iron concentrates, have posed new challenges for beneficiation workers in China. Therefore, there is still a deeper development in the beneficiation technology of metallurgical mines in China:
(1) While promoting the application of high-quality iron concentrate beneficiation technologies such as magnetic separation reverse flotation and high-efficiency magnetic separation (magnetic gravity separation), the beneficiation process should be as efficient and simple as possible. Therefore, research on beneficiation equipment and processes should be strengthened to achieve the best results with the most suitable process as much as possible. The reverse flotation process has important application prospects for improving the recovery rate of metals, and research on reverse flotation reagents should be actively strengthened .
(2) While continuing to attach importance to the technology of increasing iron and reducing silicon in iron concentrate, future research should focus on reducing other harmful impurities, including S, P, K, Na, F, etc.
(3) Further efforts should be made to strengthen the research on the beneficiation technology of extremely fine grained red iron ore and composite polymetallic red iron ore, in order to further improve the utilization rate of poor red iron ore in China.
(4) In terms of grinding and sorting equipment, we should focus on the introduction and cooperative development of energy-saving ultra-fine crushing equipment in the future. We should increase the introduction and digestion of advanced foreign technology and equipment, and quickly improve the overall technical equipment level of China’s iron ore. Simultaneously considering the development and research of coarse particle tailings disposal technology and related equipment. Further efforts should be made to develop energy-saving beneficiation equipment that can effectively recover fine-grained iron minerals, including permanent magnetization of strong magnetic equipment, fine-grained flotation machines, and flotation columns. We need to conduct more in-depth research on multi drum magnetic separators with multi stage continuous separation performance.
(5) In terms of mineral processing reagents, emphasis should be placed on developing reagents that are highly adaptable, efficient, low temperature resistant, and non-toxic to various ores; Research on the simultaneous preparation and addition of compound drugs; At present, emphasis should be placed on developing efficient collectors that can flotation non quartz silicate gangue minerals and expanding the application range of reverse flotation technology.
(6) At present, research on flotation equipment is mainly developing towards large-scale and energy-saving directions, reducing the lower limit of flotation particle size and introducing a composite force field into flotation machines. In addition, research on automatic control of flotation machines should also be strengthened. There is still a lot of work to be done for the application of flotation columns in iron ore mines, which has great prospects.
(7) In terms of filtration and dehydration equipment:
① Research and development of efficient filtration media;
② Develop multifunctional integrated components to enhance sealing performance;
③ Develop composite filtration technology equipment;
④ Equipment large-scale, energy-saving, and automation.
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