DUPLEX PROCEDURE FOR THE PRODUCTION OF METALS AND METAL ALLOYS FROM OXIDIC METAL ORES

摘要

The production of highly metallised feed, an intermediate product produced solely by gaseous reductants in two stage reduction processes of that kind, encounters sticking problems, which interfere with continuous processing and productivity. This problem has been overcome by exploiting a high volatile carbonaceous material, such as coal, as the reducing agent for the (partially reduced) oxide ore starting material in the solid state prereduction stage of a duplex process, in which the final stage consists of smelting, to produce the final metal (alloy). Intermediate products of the first stage are char from the coal, which avoids the sticking problem, partially reduced ore and CO and H2, which participate in the prereduction. The process has particular application to iron ores, such as haematite and magnetite and similar derivatives, namely, chromite and oxidic nickel ores. The process may be extended to a triplex, which includes drying, preheating and partial reduction in the first stage, followed by further partial reduction and finally the smelting step. Plant for the process may consist of a shaft furnace or fluidised bed for the prereduction sequence, preferably the latter. For the triplex process, two associated fluidised beds (3, 5) are preferred. Any suitable furnace (7) may be used for smelting, as long as it is equipped for the injection of partially reduced ore, char and fluxes, hot air lancing, off gas and the tapping of molten metal and slag. The final stage of solid state reduction takes place at a temperature of at least 550 DEG C, preferably 750-900 DEG C. At least 50 % of metallisation is essential for satisfactory processing, preferably at least 80 %.