Three main processes for extracting nickel metal from laterite nickel ore
Our steel output has ranked first in the world for many years in a row, a truly global steel power. As one of the symbols of the world's steel powers, China's high-performance, high value-added annual output of stainless steel has reached 7.2 million tons in 2007, ranking first in the world for three consecutive years. The output of 300 series stainless steel containing high nickel accounts for about 58%. about.
China is a country with relatively scarce nickel resources, and a large proportion of it relies on imports. Traditional extraction of nickel from nickel sulfide ore metal for nearly a hundred years of history, process maturity, but after a century mining, the increasing depletion of the Earth's nickel sulfide ore resources, and therefore nickel oxide ore (commonly known as: nickel laterite) nickel metal being extracted Gradually become the mainstream of the world's extraction of nickel metal.
As the world's largest importer of nickel ore and nickel metal, China is researching and exploring a development path of nickel metal production suitable for China's national conditions, aiming at the characteristics of different processes for extracting nickel metal from nickel ore. It is recommended that relevant government departments formulate corresponding strategies and The strategy has great practical significance for ensuring the supply of nickel resources necessary for the sustainable and healthy development of China's stainless steel and special steel industries.
There are three main processes for extracting nickel metal from laterite nickel ore, namely wet smelting (electrolysis), pyrometallurgy (electric furnace), and pyrometallurgy (blast furnace). At present, China's new industrial projects have implemented a one-vote veto system for environmental protection assessment. Therefore, the first comparison is from environmental protection and circular economy: wet smelting: general laterite nickel ore contains Ni between 0.8 and 3.0%, and Co contains 0.02 to 0.3. Between the %, wet smelting only extracts Ni and Co, and the remaining 97% contains Fe (higher than 10% to 45%) and a small amount of Cr is discarded as solid waste. Special site stacking; wet smelting uses liquid acid or ammonia as leaching agent for Ni and Co. After use, except for partial recycling, the rest are treated with liquid and discharged into rivers or reclaimed into waste pool; wet smelting will also Produces a large amount of CO 2 gas emissions. Since solid, liquid, and gaseous waste generated in production cannot be recycled, which causes great harm to the environment, it is a total discharge of three wastes. Therefore, there is no development prospect in China.
Pyrometallurgical smelting: Whether it is electric furnace or blast furnace, the solid slag produced in the production is calcined at high temperature, and becomes a low-strength cement after drying and grinding. It is the best filler for cement manufacturers to produce standard cement, and it is also the production of brick factory. The high-quality raw materials of bricks and tiles can be recycled 100%; in addition, the cooling water used in the production of blast furnaces can be closed for use in closed cooling water tanks; the blast furnace slag water can also be recycled and recycled. Therefore, almost all solid and liquid wastes produced by pyrometallurgical smelting are recycled and utilized, and the two wastes are completely solved in the three wastes. Therefore, it is the development direction of China's nickel metal refining industry. However, no matter whether it is electric furnace or blast furnace, there is no way to completely solve the CO 2 emissions generated in production, and there is no report on solving this problem in the world. Since nickel laterite ore ships with low sulfur content as compared to the production of SO 2 emissions and therefore a more general pig iron smelting greatly reduced, but Pyrometallurgy recycling coal gas, recycling of dust is the focus. Among them, the electric furnace has a small footprint and is easy to handle; the blast furnace has a relatively large amount of engineering and investment. We should closely combine the reality of our country, accelerate the research, and develop a complete set of equipment, standards and processes that meet the needs of environmentally friendly production and recycling economy for smelting ferronickel.
In addition, electric furnace smelting mainly uses electricity as the main energy source. Most people think that electric energy is clean and convenient, and does not emit CO 2 during smelting, which is environmentally friendly. We should understand that if the electricity used is nuclear power, wind power, solar power, this view is certainly good. However, the fact is that most of the electric furnace smelting in China uses coal power. During the power generation process, a large amount of CO 2 and waste gas are generated. The coal combustion turns the water into high temperature and high pressure steam. The gas can drive the gas turbine to form mechanical energy, and the mechanical energy of the steam turbine is driven again. The generator rotates to form electrical energy. Every time the energy form is converted, the efficiency is reduced once; in addition, the loss of electrical energy is transmitted over long distances. Therefore, the loss of electricity per layer of electricity to the user's electric furnace is much lower than that of the coal that will send this electricity. The heat generated by the blast furnace. Because the coke put into the blast furnace is directly burned without energy conversion and is highly efficient. Since electric energy and electric furnace smelting must reach the same temperature as the blast furnace to produce molten iron, the amount of electricity and electric furnace smelting electricity converted into electric coal will be higher than that of blast furnace coke, in other words, The total amount of CO 2 emitted by electric energy through electric furnace smelting will exceed that of blast furnace smelting. Secondly, coke is used as energy in blast furnace smelting, and hundreds of chemical raw materials can be extracted from coal by refining coal into coke. It is recognized as the most effective way to comprehensively utilize coal resources economically and rationally. Finally, investment in electricity production is large, and coke production is low. Therefore, the production of ferronickel in blast furnaces is superior to the production of electric furnaces in energy consumption and environmental protection.
From the comparison of product quality and price of different processes with market demand, wet smelting: can extract 99.9% nickel and cobalt metal separately, which is the biggest advantage of wet smelting. Its pure nickel is the main raw material for electroplating, battery, chemical catalytic equipment and special stainless steel special steel; pure cobalt is the main raw material for high strength, high temperature and high wear resistance special steel.
Wet smelting has a long history in China, accounting for a high proportion of nickel metal production in China. However, the annual production of pure nickel has far exceeded the annual market demand for the above purposes. Therefore, a significant portion of this is currently being converted to the smelting of 300 series nickel-containing stainless steel. This is really an anti-aircraft gun to fight mosquitoes, and it is suspected of being overused. Because of the large investment in wet smelting production process, long cycle, complicated process, high cost and high selling price, stainless steel and special steel production enterprises love and hate it. Love is high in purity, easy to use, product quality is guaranteed; hate its price is too high, so that product cost increases profitability and reduce market competitiveness, but this state is difficult to change.
The electric furnace process of pyrometallurgical smelting: It can extract nickel-iron containing 10~25% of nickel and containing a small amount of cobalt and chromium , which can replace pure nickel to become the nickel raw material of smelting 300 series stainless steel. Because it uses electricity as the main heat energy (generally consuming 7,000-8,000 kWh to produce one ton of ferronickel), it does not use coke as a heat source in the blast furnace and also brings the phosphorus in the coke into the product. Therefore, the ferronickel produced by the electric furnace The content should be lower than that of the blast furnace, which is beneficial to shortening the time of smelting stainless steel, so it is widely welcomed by the market. However, the fly in the ointment is that China's power supply continues to be tight, China's high-power consumption industry is very strict, and once the electricity production area is tight, the first thing to do is to cut off the electricity used by large electric households to make the production abnormal. Secondly, the output of electric furnace ferronickel is relatively low. A single 25,000 KW electric furnace produces about 15,000 tons of nickel-iron with a nickel content of about 25,000 tons per year, which is far from meeting the development of nickel-metal in the stainless steel industry in recent years. A large number of demand; Finally, it should be stated that the smelting of nickel-iron containing 15 to 25% of nickel and even higher nickel content is not achieved by increasing the nickel content of the nickel ore in the furnace, but by reducing the reduction of iron in the nickel ore. Such a large amount of unreduced iron oxide is discharged as slag (sometimes the content of iron in the slag is as high as 20% or more), and the slag is transported to the cement factory as a cement or brick factory to make bricks. Considering that the current market price of imported iron ore with 65% iron content has reached tens of several hundred yuan a ton, the large amount of iron-containing slag to be used as cement or brick is a great waste of resources.
The sales price of ferronickel produced by the electric furnace process is based on the nickel content. The market price is based on the pure nickel price. The rest of the iron, cobalt and chromium are not valued. The smelting 300 series stainless steel is smelted with pure nickel, which can be reduced per ton. The cost is 3,000 to 4,000 yuan.
Pyrometallurgical blast furnace method: It can smelt ferronickel containing 1.5~10% nickel and containing a small amount of iron and chromium, which can be used as the basic raw material for smelting nickel-containing stainless steel. Due to the high price of ore and sea freight and the sale of ferronickel only in terms of nickel content, unless the customer specifically requests and gives a price increase, ferronickel containing less than 4% nickel is rarely smelted by the manufacturer, and the market is most affected. Welcome to nickel-nickel containing 10% nickel and phosphorus ≤0.035%. Stainless steel manufacturers only need to add a certain amount of ferrochrome to smelt into 300 series products (less than nickel content of 10% nickel to smelting 300 series stainless steel) It is necessary to add a certain amount of pure nickel or electric furnace to produce high nickel nickel iron for adjustment). Due to the technical and mineral composition, there are not many blast furnaces that can produce the above ingredients. The biggest characteristic of blast furnace smelting ferronickel is high output. The annual output of a 208m3 blast furnace can reach more than 40,000 tons. Due to the need to add ferrochrome and high-nickel iron, six such blast furnaces can meet the basic nickel and iron demand of a 300,000-tonne 304 stainless steel plant.
Dephosphorization of stainless steel is the most difficult, and the control of phosphorus content in blast furnace ferronickel is below 0.035%. At present, the company has basically controlled the dephosphorization technology in the blast furnace. Our products are even higher in nickel and lower in phosphorus than some electric furnace smelters. Because the output is relatively high, the nickel content is generally lower than that of the electric furnace, and the sales pricing method is the same as that of the electric furnace ferronickel, but the discount coefficient is larger, and each nickel is slightly lower than the electric furnace nickel price. In summary, the blast furnace ferronickel as the basic raw material and the electric furnace ferronickel as the raw material are the best combination of the lowest cost and the most guaranteed supply of the 300 series stainless steel raw materials, which is the future development direction.
The blast furnace can refine iron and also smelt nickel iron. Although the difference between ferronickel and pig iron is divided into two industries, iron alloy and ordinary iron, there are quite different differences in the mineral composition, formula and smelting process. The concept of smelting pig iron is hardened to smelt nickel-iron smelting. It is absolutely wrong.
1. The metal content of the mine is different: the blast furnace smelting pig iron uses 65% iron in imported iron, and produces tens of kilograms of slag in one ton of iron; for example, nickel iron with 7% nickel is required to consume nickel 1.5. %, about 20% of dry ore containing 5 tons of dry ore, about 7.7 tons of wet ore, and the total metal content of the ore is about 21.5%, so that 1 ton of ferronickel produces 4 tons of slag, which is almost ten times that of pig iron smelting and slag. . When the slag opening is opened and the slag is discharged, the number of slag discharges is significantly increased, and the process must be greatly adjusted.
At present, the prefabricated iron blast furnace is advanced in productivity and environmentally friendly. The small blast furnace is backward productivity, is a big polluter, must be eliminated, and this view is hard-wired to smelt ferronickel. In fact, this is a big misunderstanding. Since the slag from smelting nickel is many times more than the smelting iron, the blast furnace is not suitable for converting ferronickel, because the amount of slag is too large, and the opening time of the slag opening is too long, which affects the furnace temperature and affects the production. From the ton of iron ore per cubic meter of furnace capacity per day, the coefficient of iron output of a small blast furnace of 100-200 cubic meters is generally 3.4, that is, 3.4 tons of iron per cubic meter per day. If the furnace type, charge and technology are well matched, This factor can also be exceeded. On the contrary, in recent years, thousands of cubic meters of blast furnaces that have been put into production at home and abroad have a cast iron coefficient of only about 2, what is the reason?
The original blast furnace size is measured by the furnace capacity, and the furnace capacity is a three-dimensional space of length, width and height, measured by the third power of the length meter, but the blast furnace is gradually reduced and burned after adding the sinter and coke at the top. The temperature gradually rises until a certain level of temperature reaches the temperature of the iron oxide in the mine. The main iron production is determined by the size of the layer, and the area of ​​the layer is 2 The second party measures, after the number of meters is greater than 1, the square of the meter is always less than the cube of the meter. Therefore, the big blast furnace must be better than the small blast furnace. On the iron output ratio, the opposite is true. Although the environmental protection equipment on the large blast furnace is relatively economical and the labor cost allocation is relatively low, if the large blast furnace is not equipped with energy-saving and environmental protection equipment, it is also a big polluter.
At present, domestic smelting ferronickel blast furnaces are generally rebuilt from ironmaking blast furnaces. The maximum furnace capacity is no more than 400m3, and the production is still normal. However, we have found that the larger the furnace capacity, the more difficult the production, the less the amount of nickel and iron per unit volume per day. law. Practice is the sole criterion for testing truth. The scientific concept of development must first be based on the objective and practical investigation of science, in order to ensure that new policies are formulated on the basis of seeking truth from facts. Therefore, in the case of blast furnace smelting ferronickel, it is said that the blast furnace must be better than the small blast furnace, even without investigation and research, it is a typical anti-scientific behavior to make the new ferronickel blast furnace to reach the standard of 1000m3 or more. Has caused very serious consequences. For example: the products produced by our company are shipped to several major stainless steel plants in China for cold smelting of 300 series stainless steel. One of the stainless steel smelters was put into operation last year due to the construction of a new tens of cubic meters of blast furnace. The original two blast furnaces each with more than 700 cubic meters will be shut down. I hope that our company will refine the ferronickel. The company agreed .
We expect that these two blast furnaces, which are fully in line with the national ferroalloy production standards, can produce about 250,000 tons of nickel-iron water containing about 7% of nickel per year. They can be directly converted into 300 series stainless steels in the converter and AOD furnace. The ferronickel hot charging heat delivery is in line with the energy conservation and emission reduction policy strongly advocated by the state. Compared with the use of the cold nickel iron block, the intermediate frequency furnace can save electricity costs of 300-400 yuan per ton, which is 250,000 tons per year. Saving nearly 100 million yuan in electricity bills is equivalent to saving nearly 70,000 tons of coal per year, which can reduce CO 2 emissions by about 200,000 tons. But soon the plant said that the two blast furnaces must be dismantled in order to complete the energy-saving emission reduction targets. At the end of last year, when the front page of a famous newspaper published the dismantling of two more than 700 cubic meters of blast furnaces in the factory, I was only distressed when I reduced the number of tons of exhaust gas per year. The assets of hundreds of millions of fully used national assets were squandered every year. Hundreds of thousands of tons of cold nickel iron blocks are still being transported to the plant for heating and melting into stainless steel, all of which are carried out under the name of energy saving and emission reduction.
In summary, it is recommended to formulate a long-term development strategy for China's nickel metal industry. First, from the perspective of economy, environmental protection and product market saturation, further expansion of wet-process smelting of nickel metal production should be strictly prohibited or restricted in the future. .
Second, in areas with abundant hydropower, wind power, and nuclear power resources, and in areas where coal and electricity are heavily wasted in the evening, low-valley electricity should be preserved or a new batch of pyrometallurgical nickel-iron smelting enterprises should be retained, mainly producing high-nickel series ferronickel. It is used for the adjustment of the production of 300 series stainless steel with insufficient nickel content.
Third, in areas close to the sea near the port and close to the coke production base in line with the national steel industry development policy, some small blast furnaces with convenient transportation and good production and environmental protection facilities are reserved. If the environmental protection is not up to standard, the course needs to be replenished; A new batch of special blast furnace suitable for smelting ferronickel is appropriately built. The new blast furnace should give priority to the joint venture of the owners who have been banned from the blast furnace to build a new company, build a new blast furnace, and the government will give appropriate subsidies and tax incentives to compensate the losses of these owners.
Fourth, the scale of retention or new construction: In 2007, China's stainless steel output was about 7.2 million tons, of which high-nickel stainless steel production accounted for about 58%, about 4.2 million tons. After deducting imported waste nickel-containing stainless steel and stainless steel smelting and processing enterprises, about 700,000 tons of materials are returned. After deducting the added ferrochrome and high nickel of 500,000 tons, China needs blast furnace smelting ferronickel for 300 series of basic materials of 2.5 million tons. The ferrochrome and the electric furnace high-nickel iron can be used to meet the annual production of 3.5 million tons of 300 series stainless steel. Oil is a strategic material, food is a strategic material, and metal nickel is a strategic material. It is necessary to establish a reserve of ferronickel.
Based on a reserve of 500,000 tons of blast furnace ferronickel per year, the blast furnace ferronickel should be produced in 2008 at about 3 million tons. Based on 7% nickel-bearing nickel, the annual blast furnace smelting nickel-iron needs 1.5% nickel. The mine is about 21 million tons; considering the electric furnace smelting, about 25 million tons of laterite nickel ore is needed throughout the year. In the small blast furnace, the output of nickel 7% nickel iron is 0.6 tons per cubic meter per day. The total furnace capacity of the small blast furnace should be 15,000 cubic meters. For example, in each blast furnace 200 cubic meters, 75 blast furnaces are required. The 15,000 cubic meters of furnace capacity, such as refined iron, is 3.4, and the annual output is about 17 million tons. It is hoped that all levels of government departments will promptly approve according to the actual needs of China, so that the furnace can be kept under the knife.
For example, the government's competent authorities still insist on the policy of rushing to kill the small blast furnace instead of properly selecting and retaining a batch, which will artificially cause the shortage of nickel metal supply in China's stainless steel and special steel smelting enterprises. The relationship between supply and demand determines the price. When the small blast furnace is eliminated, it is the time when the monopoly of pure nickel production raises the price and affects the output of stainless steel in China.
The world today is very clear: who has the resources and who has the future. Recently, oil has soared to more than 100 US dollars a barrel, and iron ore has skyrocketed by tens of thousands of years. The fate of Chinese enterprises is only forced to accept, and there is no right to speak at all. Therefore, when the small blast furnace is completely wiped out, the day when pure nickel skyrockets to 50,000 or even 100,000 US dollars a ton will come sooner or later. At that time, the dream of China’s rapid growth from a world steel country to a world steel power will be ruined by the wrong policy makers. In the hands, it is not to believe, let history prove.
Chinese enterprises should build a number of mineral bases in the red earth nickel ore deposits in Southeast Asia as soon as possible with the support of the government to ensure the long-term stable supply of laterite nickel mines. Further, we can establish joint ventures or sole proprietorships with mining and smelting companies. Direct production of ferronickel or stainless steel, and the path of prosperity with the people of the resource countries.
Sixth, the stainless steel and special steel industries are high-tech, high-input, high value-added industries. For a long time, the world's steel powers have tried every means to enter the Chinese market in order to share their interests. We believe that China should gradually reduce the export of resource-based low-tech and low-value-added products such as pig iron, coke and ordinary steel, and vigorously promote the export of high-tech and high-value-added products such as stainless steel and special steel. At present, regardless of high-tech or low-tech, high value-added or low value-added products, it is a foolish policy to reduce the export tax rebate for steel products and even to impose high export tariffs to curb the excessive growth of foreign exchange surplus. Relevant departments should implement a policy of full-fledged change in the export of high value-added products such as stainless steel and its products to promote the healthy and sustainable development of China's stainless steel industry.
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