Low temperature thermal upgrading of lateritic ores

摘要

This invention relates to a thermal upgrading process whereby nickel-containing limonite or limonite/saprolite blends are pelletized with requisite amounts of solid carbon reductant and a sulfure-bearing concentrating agent. The pellets are fed to a reactor where they are gradually heated, causing reduction of the metal values. The reduced pellets are then held in a "metallics growth zone" of the reactor at a temperature high enough to allow for liquid-phase migration of the metallics within the pellets but below the point at which the pellets become sticky. The metallics growth zone is provided with a carefully controlled combustion gas atmosphere equivalent to about 60-65% aeration of partial combustion of natural gas which prevents further reduction or re-oxidation and thus provides a good environment for metallic particle growth. After a sufficient retention time, the pellets are then rapidly cooled to prevent the disproportionation of wustite to magnetite. The cooled pellets are then ground and the magnetic fraction separated.