A brief discussion on the smelting process of nickel iron in ore smelting furnace
1 the metal nickel has good mechanical strength, ductility and corrosion resistance, chemical stability, can be magnetized, and a series of characteristics, widely used in stainless steel, high temperature alloy, electroplating and chemical industry, and plays an important role in the development of the national economy. About 2/3 of the world's nickel for the production of stainless steel, nickel raw material costs account for about 70% of the production cost of austenitic stainless steel.
2 the process of smelting nickel iron smelting iron and nickel smelting process is mainly based on the principle of fire and wet, and the two. For the nickel sulfide ore, the main method is to use the fire treatment method, and the copper nickel sulfur converting nickel concentrate is used to obtain the nickel metal by the roasting furnace of concentrate roasting. For the oxidized ore is mainly containing nickel laterite ore, its grade is low, suitable for wet treatment; the main methods of ammonia leaching and sulfuric acid two. Oxide ore pyrometallurgical nickel iron.
2.1 blast furnace blast furnace production of pig iron has a long history, but the general use of blast furnace production of nickel iron or Chinese invention (Liu Guanghuo) and the results of the study.
Blast furnace ferronickel production process mainly is: dry sieving ore (bulk crushing) - ingredients, sintering sinter and coke into blast furnace smelting flux and block - nickel iron ingot and slag water quenching - producing nickel ingot iron and slag.
2.2 (electric furnace furnace) method here refers to a kind of electric arc furnace is called smelting furnace, ore heat furnace ferronickel smelting process is: ore drying and crushing of coal blending and large flux into the rotary kiln to dry thoroughly and pre reduction furnace reduction smelting of iron nickel iron ingot and slag water quenching output: ferronickel ingots (or water quenched into nickel particles) and water quenching slag.
This process usually refers to the rotary kiln and furnace technology, has decades of production history in foreign countries, there is a relatively mature technology and theory, a few domestic manufacturers have a few years of production history, but are small equipment production, many technical problems, the benefit is not good, recently several enterprises have been put into operation and under construction on the scale of the production line.
This process can produce any nickel content in any nickel iron nickel grade ore, iron reduction rate control technology is in the stage of rotary kiln to achieve (nickel all reduced to metal and iron partially reduced into metal and low oxide), this is the biggest feature of this process, but also its vitality the reason, but because of the huge power consumption of smelting furnace and high production costs, in addition to its shortage areas.
3 nickel iron smelting furnace low cost production process (RKEF method) RKEF Technology ("rotary kiln furnace") began in 1950s, by the Elkem company in New Caledonia's successful development of an Bo Factory, the products of good quality, high production efficiency, energy conservation and environmental protection, RKEF process was soon replaced by blast furnace process. With the development of Metallurgical Science and technology, RKEF technology also attract a large number of the latest technological achievements including automation, clean production, in the design and manufacture, installation and production operation has become more and more mature, has become the mainstream technology of ferronickel production in the world, occupy the dominant position. At present, there are more than ten companies in the world using RKEF process to produce nickel iron, and the production plants are all over Europe, America, Japan, Southeast Asia and other places.
In the world, it is very suitable and economical to use RKEF as a raw material to produce nickel iron by using the method of fire.
3.1 RKEF 3.1.1 technology introduced the requirements on raw materials for the rotary kiln furnace (RK) - (EF) process, ore composition is very important, there are 3 indicators is the use of RKEF technology should be concerned: (1) Ni grade, in the hope of more than 1.5, more than 2 of the best.
(2) Fe / Ni, in the hope that the best 6~10, close to 6, Ni in high grade; if the Fe / Ni>10, it is difficult to smelt nickel iron containing 20%, because of the high Fe materials, it is difficult to control the iron oxide in the rotary kiln reduction degree.
(3) MgO/SiO2, in the 0.55~0.65 is appropriate, a small amount of flux can be added to the low melting point of the slag structure.
The above 3 conditions are suitable conditions, not the necessary conditions, in the ore conditions do not meet the above requirements, can produce low grade nickel iron, technical and economic indicators will be affected.
Reducing agent (bituminous coal or anthracite can be) and limestone is also necessary for the RKEF process, these two kinds of raw materials in China is rich in resources, easy to get.
3.1.2 typical process flow, main equipment structure (1) production process raw material field (laterite nickel ore) - crushing, screening, drying, blending ingredients, rotary kiln, ore heat furnace, iron ladle desulfurization, refining converter. On this basis, the development of raw materials, raw materials, pre drying ball rotary kiln waste heat power generation, energy-saving and efficient smelting furnace and low melting slag ingredients, with bottom blowing or side blown converter refining instead of BOF, ferronickel granulation technology, suitable for different conditions of the factory.
(2) technology of ore, limestone, reducing agent in the field, to raw material preparation between screening and crushing, mixing the ingredients into the rotary kiln, rotary kiln, raw material drying, roasting and reduction of nickel slag, made about 1000 DEG C, the rotary kiln flue gas waste heat boiler, dust removal, devulcanization after discharge the dust mixed with the raw material, after again into the kiln.
The nickel slag (rotary kiln) is added to the ore heat charge bin (lining refractory brick) in the closed heat insulation condition (the elevated feeding trolley).
Ore furnace product is crude nickel, wrapped in hot metal desulfurizing agent before tapping, tapping and desulfurization, crude nickel containing Si, C, P and other impurities, need to continue refining slag, adding acid converter, oxygen silicon removal, while adding nickel containing waste to prevent the high temperature of molten iron, desilication slag (slag or iron), duiru alkaline oxygen converter, dephosphorization and decarburization, while adding limestone made alkaline slag, nickel iron alkaline refining converter after sent to the casting workshop, cast nickel iron goods qualified or made of granular ferronickel.
3.2 RKEF technology to improve and innovate although RKEF is a mature technology, but because of the external conditions of different countries, such as electricity and energy structure, will affect the cost of production.
Domestic use of this technology must be improved. First of all, we must study the batching model. Domestic nickel oxide ore resources are poor, to rely on imports, imports of complex ore sources, the lack of a stable base of raw materials, making the development of more important ingredients model. In addition, the small scale industrial experiments are carried out in order to obtain the melting point of slag, the melting characteristics of slag and iron and the suitable sintering temperature, so as to guide the production.
4 the end of the smelting furnace smelting nickel iron has its characteristics, in our country batch smelting time is relatively short, but the RKEF process has become the main method of laterite nickel ore processing.
Research and development of high efficiency, short process, low energy consumption, environmental protection and other new smelting process has become the future development trend of laterite nickel ore.