In 1930, the Rrupp Company developed the direct reduction Rrupp Renn process. During World War II, Japan's Dajiangshan Smelter used Rrupp Renn process to treat the low-nickel pig iron produced by surrounding minerals with very low nickel content and used it as raw material for alloy steel. After the war, the raw material was changed and laterite nickel ore was used. The process of semi-melting reduction roasting at high temperature (about 1350℃), water quenching, jig gravity separation, tailings ball milling and magnetic separation is used to directly produce nickel-ferro alloy containing more than 20% nickel for the production of stainless steel.
Development process of reduction production of laterite nickel ore
1. Sintering ore-small blast furnace melting process
As early as 1879, blast furnaces (blast furnaces) were used to treat laterite nickel ore in New Caledonia, but this technology was not popularized due to high energy consumption, unstable process and serious pollution.
The advantages of blast furnace smelting production of ferro nickel are small investment, low energy consumption, suitable for small scale, power supply difficulties and low nickel content laterite mining area; Its disadvantages are poor adaptability to the ore, strict requirements on magnesium content, energy consumption is too large, serious environmental pollution, in addition, it can not deal with the fine ore, the furnace charge also has strict requirements. Electric furnace smelting process is suitable for treating various types of nickel oxide ore.
2. Mineral Furnace process rotary kiln-electric furnace melting method (RKEF)
The production of nickel-iron from laterite ore by rotary kiln-electric furnace smelting process (RKEF) began in the 1950s. As the raw ore contains a large amount of free water and crystallizing water, it needs to be dried, dehydrated and preheated by rotary kiln at 800℃ in the preparation stage of smelting furnace charge. Then the hot charge is sent to the electric furnace in the high temperature of about 1550~1600℃ reduction smelting nickel iron production.
Advantages: 1) The process is mature, can realize mass production; 2) Nickel-iron products are of good quality and can be used for middle and high grade stainless steel production; 3) Strong raw material adaptability, all types of laterite nickel ore can be treated; 4) After water quenching treatment, electric furnace slag can be used as raw material for cement production to realize harmless utilization of waste slag.
Defects: High power consumption and high cost of electric furnace smelting.
3, rotary kiln reduction - magnetic separation process
Since 1952, Japanese metallurgical company Dajiangshan Smelter began to use the Dajiangshan process to smelt stainless steel. Dajiangshan process is the raw ore is dried, crushed and screened, mixed with flux and reducing agent in proportion to make pellets. The pellets are dried and calcined at high temperature, and the calcined sand is then water quenched, crushed and screened, and sorted to get sponge granular nickel-iron products. It is a new process for the preparation of nickel-iron alloy raw materials by reduction roasting and magnetic separation of laterite nickel ore.
Advantages: short process, less energy consumption, low production cost.
Disadvantages: rotary kiln investment cost is large, covers an area of much.
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