Hydrometallurgical And Pyrometallic Nickel

Nickel is a transition metal element with element symbol Ni, located in group VIII of the fourth period, with atomic number 28. Nickel is a silver-white metal with good mechanical strength and ductility. It is insoluble in water and has strong corrosion resistance to acids and alkalis, but it is easily soluble in dilute nitric acid and aqua regia. High temperature resistance, melting point 1455 °C, boiling point 2730 °C. The density is 8.902g/cm³. It can be used to make currency, etc. It can be plated on other metals to prevent rust.
 
Due to the small amount of nickel sulfide ore resources on the earth, the extraction of nickel metal from nickel oxide ore (latite nickel ore) has gradually become the mainstream of nickel metal extraction in the world. There are two main extraction processes for laterite nickel ore: hydrometallurgy and pyrometallurgy.
 
Hydrometallurgy
 
The smelting process of wet smelting can be divided into ammonia leaching process, high-pressure acid leaching process, reduction roasting-acid leaching process and sulfated roasting-water leaching process. Among them, the ammonia leaching process is only suitable for treating laterite ore on the surface, and not suitable for treating nickel oxide ore with high copper and cobalt content. The high-pressure acid leaching process is suitable for processing low-magnesium (aluminum) high-iron type lateritic nickel ore-limonite type (70% of laterite ore belongs to limonite type).
 
Advantages of hydrometallurgy: low energy consumption, low pollution, high quality, long history of process development, originated in the 1970s, whether it is atmospheric pressure or pressure acid leaching, the current technology is relatively mature, and there are many mature products at home and abroad With the increase in environmental protection in recent years and the export restrictions of some former nickel exporting countries, my country has gradually reduced the direct smelting of laterite nickel ore, and instead smelted the primary nickel intermediate products to produce nickel iron and electrolytic nickel. Promoted the import of nickel hydrometallurgical intermediate products. The development advantages of hydrometallurgy are more obvious. Its shortcomings are the large process investment, long cycle, complex process, high cost and high price, and weak market competitiveness, but this situation is difficult to change at a time.
 
Fire smelting
 
The smelting process of pyrometallurgy can be divided into reduction smelting ferronickel process and reduction sulfide smelting nickel matte process. Pyro smelting is suitable for processing silicon-magnesium-nickel type ore (that is, the ore with higher silicon and magnesium content, lower iron content, and lower cobalt content in the lower part of the deposit). One of the most used is the reduction smelting process of ferronickel.
 
Pyro smelting can be divided into electric furnace smelting and blast furnace smelting according to reduction smelting equipment. Large-scale factories mostly use electric furnace smelting, while small plants use blast furnace smelting. Electric furnace smelting is suitable for processing various types of nickel oxide ore, depending on the supply of raw materials, ore storage, etc. The production scale can be large or small, and there is no strict requirement on the particle size of the charge into the furnace, powder and larger pieces All materials can be processed directly, but the disadvantage is that it consumes too much energy. The advantages of blast furnace smelting to produce ferronickel are small investment and low energy consumption. It is suitable for small scale, difficult power supply and laterite ore with low nickel content. The disadvantage is that it has poor adaptability to ore and has stricter requirements for magnesium content. In addition, fine ore cannot be processed, and there are strict requirements for furnace charge. On the whole, the fire method has high energy consumption, poor comprehensive metal recovery effect, and the cost is equivalent to the cost of wet smelting, which is a traditional treatment method.