China Nonferrous Metallurgy

Transitional laterite nickel ore is a sluggish and difficult-to-utilize resource. The existing acid leaching process tends to introduce impurity elements such as iron, magnesium, and aluminum into the leachate, making effective separation difficult. The reduction roasting-ammoniacal leaching process tends to generate Fe(OH)₃ colloid, resulting in low recovery rates of nickel and cobalt and a lengthy process. This study addresses this issue by focusing on a certain mine's transitional laterite nickel ore as the research subject. It systematically investigates its process mineralogy characteristics, proposes a process for recovering nickel and iron through carbothermic reduction-magnetic separation, examines the impact of temperature on nickel and iron recovery, and analyzes the structural characteristics of the products. The main conclusions are as follows. The chemical composition and mineral phase analysis of the ore reveal that the nickel and iron grades in the sample are 1.23% and 28.14%, respectively, with SiO₂/MgO ratio of 1.53, indicating a low-iron, high-magnesium transitional laterite nickel ore. The microscopic analysis of minerals indicates that nickel and iron elements occur in multiple carriers, with nickel magnetite and goethite being the main occurrence phases; nickel is distributed in olivine, limonite, and hypersthene in an isomorphism manner. By adding 25% coal powder and 5% CaO to the raw material and reducing it through roasting at 1 340°C for 2 hours, the phase composition of the product consists of Fe-Ni, Mg₂SiO₄, and Al₂SiO₅. The grades of Ni and Fe in the magnetic separation product reach 4.04% and 83.67%, respectively, with corresponding recovery rates of 92.26% and 79.87%. After magnetic separation, the Fe-Ni alloy is enriched in the magnetic separation product, which exhibits saturation magnetization with a saturation magnetization intensity of 145.51 A·m²/kg, allowing for efficient enrichment through low-intensity magnetic separation. Impurities such as Si and Mg are mainly discharged with the magnetic separation tailings in the form of Mg₂SiO₄.