Can iron be selected from laterite nickel slag?

Laterite nickel ore is an important nickel oxide ore, accounting for approximately 60% - 70% of the world's land-based nickel reserves. The hydrometallurgical process is an effective technology for extracting nickel from limonite laterite, the main nickel-bearing ore. Among them, reduction roasting ammonia leaching (RRAL) is one of the mature technologies for processing limonite laterite and has been widely used in industrial applications for decades.

In the reduction roasting ammonia leaching process, various metal oxide minerals in nickel laterite are first reduced by coal at 600-900°C, and nickel slag is generated after beneficiation. The occurrence of valuable metals such as iron, chromium, and nickel in nickel slag is relatively complex. Iron mainly exists in the form of magnetite and maghemite, with a coarse-grained size above 50 μm, and is the main mineable metallic mineral. Chromium exists in the form of monetite, with some Al 3+ and Mg 2+ cations replacing Cr 3+ cations in its crystal lattice. The chemical composition of dermatite is complex, making it difficult to separate by traditional physical methods, and the recovery rate is low.

Based on the mineralogical characteristics of nickel slag, it can be concluded that magnetite and maghemite, as the main iron-containing minerals, should be given priority for recycling, and conventional magnetic separation technology will be a more suitable mineral processing method. In view of the embedding characteristics of magnetite and maghemite minerals, the nickel slag is purified using a graded grinding-graded low-intensity magnetic separation process.

To this end, we have developed a two-stage grinding and two-stage low-intensity magnetic separation process to recover metallic iron. Under the conditions of a grinding fineness of -0.074 mm 77% and a primary magnetic separation magnetic field strength of 0.29 T, a magnetic concentrate was obtained with a total iron grade of 61.88% and a total iron recovery rate of 75.80%. The grinding fineness of the secondary magnetic separation was With a magnetic field strength of -0.074 mm 93% and 0.17 T, it can be used as raw material for subsequent sintering or pelletizing processes in the ironmaking industry.