Pilot scale test of producing nickel concentrate from low-grade saprolitic laterite by direct reduction-magnetic separation

Abstract

The enrichment of Ni from a low-grade saprolitic laterite ore, which has been pre-treated by high pressure grinding roller(HPGR) to be 74% passing 0.074 mm and contains 0.92% Ni, 18.47% Fe, 10.61% MgO and 42.27% SiO₂, was conducted by using pelletizing, rotary kiln reduction and magnetic separation process on a semi industrial scale, and the effects of reduction duration, mass ratio of coal to pellets(C/P), the types of magnetic separator, the sections of grinding-separation and the grinding fineness on the recovery of Ni and Fe were examined. It is shown that nickel concentrate containing 3.13 % Ni and 59.20 % Fe was achieved at recoveries of 84.36 % and 71.51 % for Ni and Fe, respectively under the following conditions: reducing at (1120±40) °C for 120 min, C/P being 1.0, wet grinding of reduced pellets up to 70%–87% passing 0.074 mm and a magnetic field intensity of 238.8 kA/m during the first section of grinding-magnetic separation, and a grinding fineness of 84%–91% passing 0.045 mm and a magnetic intensity of 39.8 kA/m during the second section of grinding-magnetic separation. The enriched Ni containing concentrate has a low content of S and P, and can be used for further processing to produce high-grade ferronickel alloy.