GB432439A - Process for purifying nickel - Google Patents

Abstract

Crude nickel and scraps of impure nickel are refined by producing such an intense and violent intermixing between the metal in the molten state and a molten and very fluid slag of a suitable composition that an emulsion-like and turbulent mixture of nickel and slag is proproduced. If sulphur is to be eliminated from the metal a basic slag free from nickel oxide with a basis of alkali and/or alkaline earth oxides and containing, if desired, a small quantity of titanium oxide or silica is used. To eliminate impurities like arsenic, antimony and silicon whose oxides have with respect to the molecule of oxygen a higher heat of formation than nickel oxide and act as acids in the slag and to eliminate partially other impurities whose oxides have similar properties and are basic, basic or neutral slags containing nickel oxide are used. To eliminate impurities whose oxides have similar properties and act in the slag as bases and to eliminate partially impurities whose oxides are acid, acid slags containing nickel oxide partially in the free state and partially combined with the acid constituents are used. Said slags contain, in addition to nickel oxide, acid oxides such as silica or titanium oxide or neutral oxides such as alumina, and oxides, which are practically not reducible by the nickel such as magnesia or lime. To extract nickel oxide and other oxides dissolved in the nickel, slags, preferably acid, containing no nickel oxide or very little and which possess a high power of absorption with respect to nickel oxide are used. Before or during the refining treatment metals, such as manganese, magnesium and iron which are oxidized by the nickel oxide in the metal producing oxide which are soluble in the bath and more readily absorbable by the slag than nickel oxide are used. The process may be carried out in a series of operations in a convenient order according to the impurities present in the metal, and the purification from the same impurity may be repeated several times if necessary. The turbulent mixing may be carried by pouring the nickel in a large jet and from a sufficient height e.g. 3 to 5 metres upon the bath of slag or may be produced by mechanical means or by violent agitation by means of gases which are incapable of interfering with the purification operations. Specifications 404,300 and 405,633 are referred to.