Upgrade of nickel and iron from low-grade nickel laterite by improving direct reduction-magnetic separation process

Low-grade saprolite nickel laterite, characterized by complicated minerals composition and fine-grained and complex dissemination, was commonly treated with a low recovery efficiency of Ni and Fe by conventional methods. Hence, an improved direct reduction and magnetic separation process was proposed. Meanwhile, the mechanisms on the enhanced growth of the Ni-Fe particles and the phase transformation in the nickel laterite pellets were explored. The low-nickel concentrates as a nucleating agent can obviously decrease the activation energy for growth of Ni-Fe alloy particles during the improved direct reduction process from 197.10 to 154.81 kJ/mol when the low-nickel concentrates were added from 0 to 20%. Hence, it is able to decrease nucleation barrier, induce the growth of Fe-Ni alloy particles and increase their average size. As a result, the size of Ni-Fe particles in the pellets from less than 10 mu m grew to more than 20 mu m, which is beneficial for the full liberation and recovery of Ni and Fe in subsequent magnetic separation process. Therefore, the preferable Ni-Fe alloy concentrates with 6.44% Ni and 82.48% Fe can be prepared with corresponding recovery rates of 96.90% and 95.92%, respectively, when adding 20% low-nickel concentrates.