PREPARATION OF HIGH-MAGNESIUM SIDERITES OF THE BAKAL ORE FIELD FOR METALLURGICAL PRODUCTION BY METHODS OF PYRO- AND HYDROMETALLURGY
Ores of the Bakal ore field are hard to concentrate, due to the fact that compounds of iron and magnesium, both the ones comprised in the main mineral before roasting - a sideroplesite, - and in a roasted product obtained by the existing method of preparation, form common crystal lattice. Despite the fact that it was proposed and tested on semi-industrial scale a number of schemes of the Bakal siderite's preparation to metallurgical production by methods of pyro- and hydrometallurgy, none of them has been implemented on an industrial scale. It is shown in the paper that heat treatment of high-magnesium siderites in the so-called conditions of “soft” roasting, enables selective extraction of magnesium oxide with a solution of carbon dioxide in water. It is established that the effective activation energy of the leaching process is, about, 45 kJ/mol, which corresponds to the process proceeding in the kinetic regime. The scheme of preparation of high-magnesium siderite to metallurgical production by methods of pyro- and hydrometallurgy, which allows to obtain magnesian iron ore concentrate containing more than 58 % of total iron whereas the content of magnesium oxide is of 5-8 %, is proposed. The accompanying product of this scheme implementation is highly active magnesia, containing no less than 98 % of magnesium oxide. The increase in total iron of no less than 8 % simultaneously with the decrease in the content of magnesium oxide of more than twice, compared to its level in the concentrate obtained by the existing method allows to significantly expand the scope of its application. Implementation of the developed scheme of preparation of high-magnesium siderite to metallurgical production by methods of pyro- and hydrometallurgy provides complex extraction of associated elements that makes the scheme economically valid.