Nickel is a chemical element with symbol Ni and atomic number 28. It is a silvery-white lustrous metal with a slight golden tinge. Nickel belongs to the transition metals and is hard and ductile. Pure nickel, powdered to maximize the reactive surface area, shows a significant chemical activity, but larger pieces are slow to react with air under standard conditions because an oxide layer forms on the surface and prevents further corrosion (passivation). Even so, pure native nickel is found in Earth's crust only in tiny amounts, usually in ultramafic rocks.and in the interiors of larger nickel–iron meteorites that were not exposed to oxygen when outside Earth's atmosphere.The Philippines, Indonesia, Russia, Canada and Australia are the world's largest producers of nickel, as reported by the US Geological Survey.The Philippines is the world's fourth largest nickel producer.
Nickel ore is mainly composed of copper sulphide ore and oxide ore, two dressing and smelting process completely different: different stone selection method is adopted according to the level of copper and nickel sulfide ore, smelting, smelting of nickel oxide ore enrichment methods can be divided into two major categories of pyrometallurgical and Hydrometallurgical.
Process for the selection of copper sulfide nickel:
Sulfide copper nickel ore dressing method, the most important is the flotation. Collectors and foaming agents for flotation of copper sulfide minerals are commonly used in the flotation of copper sulfide ore. One of the basic principles of determining the flotation process is that it is better to make the copper into the nickel concentrate, while avoiding the nickel into the copper concentrate. Because the nickel in the copper concentrate is lost during the smelting process, the copper in the nickel concentrate can be recovered completely.
Smelting of nickel sulphide ore
Process selection according to the type of raw materials, components and the requirements of the product. Sulfide ore most of the use of matte smelting is all nickel sulfide ore by different fire metallurgy process of smelting low nickel matte, the low nickel matte with converter blowing smelting of high nickel matte, nickel and copper sulfide alloy. The high nickel matte by nickel refinery refining method to produce different products with different nickel.
Nickel oxide ore
The use of nickel oxide ore crushing and pre screening processes to remove large bedrock weathering weak, low nickel content. Because of the nickel oxide ore often to quality as the dispersed in the gangue minerals, and the grain size is very fine, and therefore can not be used mechanical processing methods to be enriched, only direct smelting.
Brief introduction of nickel oxide ore smelting
Method for smelting nickel oxide ore enrichment, can be divided into two major categories of law and wet fire. The former can be divided into sulfur melting, the nickel ferric and nodulize; the latter has reduction roasting and atmospheric pressure ammonia leaching, high pressure acid leaching method etc..
Nickel oxide ore in our country occupies an important position, only the gold factory, Yunnan Mojiang Yuanjiang settled areas have some reserves. By design, the ore used to make sulfur smelting (reduction roasting) than ammonia leaching method. But overall, the ore grade is low, high magnesium (MgO by 15% ~ 30%) of refractory, fuel consumption, transportation difficulties, the current is difficult to put on the construction schedule.
Due to the relatively less nickel sulfide ore resources on earth, so nickel oxide (laterite) extraction of nickel metal has gradually become the world from the mainstream of the nickel metal. There are mainly two kinds of extraction process of laterite ore: hydrometallurgy and pyrometallurgy.
The smelting process can be divided into ammonia leaching process, high pressure acid leaching process, reduction roasting acid leaching process and sulfuric acid roasting water leaching process. The ammonia leaching process is only suitable for the surface treatment of laterite ore, not suitable for the treatment of copper and nickel cobalt oxide containing high. High pressure acid leaching process for to deal with low magnesium (aluminum) high iron type laterite nickel ore and limonite type (70% of laterite are limonite type).
Hydrometallurgical advantages: low energy consumption, less pollution, quality, technology development has a long history, originated in the 20th century 70s, whether it is normal pressure or pressure acid leaching, the technologies are relatively mature, at home and abroad have a mature production line, with the degree of environmental protection in recent years the increase and some nickel exporter export restrictions, China gradually reduce the direct smelting of nickel laterite ore, instead of smelting after initial processing of nickel intermediate products to produce ferronickel and nickel electrolysis, thereby facilitating the import of intermediate products of nickel hydrometallurgy. The development advantage of the wet process is more obvious. It is the lack of technology investment, long cycle, complex process, high cost and high price, the market competition ability is weak, but it is difficult to change the status of a fashion.
Pyrometallurgical smelting process can be divided into nickel iron reduction smelting process and reduction smelting of sulfide nickel matte process two. Fire method is suitable for the treatment of silicon and magnesium nickel type ore deposit (namely the lower part of the deposit of silicon, magnesium content is relatively high, iron content is low, the content of cobalt is also low). Which are widely used for smelting nickel iron reduction process.
Smelting furnace based on reduction smelting equipment can be divided into two types: electric furnace smelting and smelting furnace smelting, the larger production scale of the plant is mainly used in electric furnace smelting, small plant is the use of blast furnace smelting. Smelting furnace is suitable for processing various types of nickel oxide ore, according to the raw material supply situation, the ore storage, decided, production scale can be big or small, on into the furnace charge size there is no strict requirements, powder and a larger piece of material can be directly, but the drawback is that the energy consumption is too large. The blast furnace smelting ferronickel production is a kind of small investment, low energy consumption, suitable for small scale, power supply difficulties and containing low nickel laterite ore to. The disadvantage is poor adaptability to the ore, on the content of magnesium have more stringent requirements, also cannot deal with ore powder, into the furnace burden, there are strict requirements.
Electrolytic process: the enrichment of sulfide ore roasting into oxide, carbon reduction into thick nickel, and then by the electrolysis of pure metal nickel.
Carbonyl method: the nickel sulfide ore and carbon monoxide to generate four carbonyl nickel, heat decomposition, and a high purity of the metal nickel.
Hydrogen reduction method: using hydrogen reduction of nickel oxide, nickel metal.
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