Specialized metallurgical processes – compositions for use therei – Processes – Free metal or alloy reductant contains magnesium
Patent
1998-02-05
2000-03-21
Willis, Prince
Specialized metallurgical processes, compositions for use therei
Processes
Free metal or alloy reductant contains magnesium
423146, 4231503, 4231504, C21B 1500
Patent
active
06039790&
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for recovering nickel in one and the same process from two pyrometallurgically produced nickel mattes, one of which contains a remarkable percentage of iron. The leaching of iron-bearing nickel matte is carried out in one step by feeding the solution coming from the leaching cycle of the matte containing less iron to the leaching of iron-rich matte at a stage where the iron of the low-iron matte is in soluble form. The iron of the mattes is advantageously precipitated as jarosite, and the solution created in the leaching of iron-rich matte is conducted back into the leaching cycle of the low-iron matte.
A large part of the world's nickel is produced hydrometallurgically from sulfidic nickel mattes, which are pyrometallurgically produced. The produced mattes are mainly low-iron nickel-copper mattes, because in the hydrometallurgical further treatment the removal of iron from the process has been difficult.
In order to obtain a low iron content in the nickel matte, the pyrometallurgical treatment of nickel concentrate has generally consisted of three steps. In the first step the concentrate is smelted, and the obtained product is low-iron nickel matte, which is below called smelting matte in this specification. The employed smelting furnace can be for instance a flash smelting furnace. In addition to the matte, from the furnace there is obtained slag with a high iron content, which slag is in the second step of the process fed to an electric furnace. In the electric furnace the slag is reduced, and the obtained products are matte with a high iron content as well as slag to be discarded. In the third step both the smelting matte and the electric furnace matte are conducted into a converter, where the iron is removed by oxidation, and the matte going further to hydrometallurgical treatment is now called high-grade nickel matte.
The converting of the above described pyrometallurgical process removes iron and sulfur from the infed matte, but as a drawback this treatment also causes recovery losses, particularly as regards cobalt, but with other valuable metals, too. In this connection metals regarded as valuable metals are particularly nickel, copper and cobalt and precious metals. Consequently, the omission of the converting step improves the recovery of valuable metals and reduces the processing costs, but on the other hand requires a capacity for treating iron in a hydrometallurgical process.
The U.S. Pat. No. 4,323,541 describes a traditional method for recovering nickel from high-grade nickel matte with a remarkably low iron content. The leaching takes place in two atmospheric leaching steps plus one pressure leaching step, where the purpose is to leach the nickel contained in the high-grade nickel matte, so that the copper remains unleached. The copper-bearing precipitate from pressure leaching is returned to the copper smelting cycle.
The U.S. Pat. No. 4,042,474 describes a method wherein ferronickel, which is a nickel product with a high iron content, is treated in three leaching steps so that nickel is made to dissolve into an anolyte obtained from nickel electrowinning, and iron is made to precipitate as jarosite.
The method of the present invention is based on the fact that in pyrometallurgical treatment, the converting step is omitted, so that there are obtained two kinds of nickel matte: smelting matte and electric furnace matte, the former containing less iron and the latter having a higher iron content. The smelting matte is processed in its own cycle, in at least one atmospheric leaching step and one pressure leaching step. The electric furnace matte (EF matte) is leached in one step into a solution coming from the leaching cycle of the smelting matte, coming either from pressure leaching or from the last leaching step of atmospheric leaching, and the solution obtained from the leaching of the EF matte can be fed back into the leaching cycle of the smelting matte. The conditions in the solution coming from the leaching cycle of the smelting furnace matte
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Fugleberg Sigmund Peder
Hultholm Stig-Erik
McGuthry-Banks Tima
Outkumpu Technology Oy
Willis Prince
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