Ferronickel Recovery from Thermally Treated Ultramafic Nickel Sulfide Concentrate

Nickel sulfide is a superior source of Ni due to its high nickel content and low-energy requirements for processing, also the product being high-purity. Hie demand for nickel, which is a critical element in many jurisdictions is predicted to increase rapidly as part of the transition to clean energy. With high-grade nickel sulfide resources gradually depleting, there is a growing need to explore low-grade ultramafic nickel sulfides as a potential resource. Although these deposits have the benefits of being amenable to surface mining and low sulfur content, which translates to fewer sulfur emissions, their high MgO content complicates the flotation of Ni minerals and also raises the slag liquidus temperature and viscosity, pushing the need for higher smelting temperatures. An environmentally friendly two-stage solid-state thermal extraction method has been proposed to extract nickel from the ultramafic sulfide concentrate by the addition of iron. In this process, nickel precipitates as ferronickel particles at relatively low temperatures, while sulfur is captured by iron to form FeS, minimizing S02 emissions. A high-grade ferronickel concentrate is expected after thermal treatment and physical separation. This study focuses on the optimization of ferronickel recovery from a thermally treated ultramafic nickel sulfide concentrate. A flowsheet for grinding the thermally treated nickel sulfide concentrate and following wet magnetic separation to obtain the ferronickel concentrate was designed and optimized for this purpose, the experimental results yielded a final ferronickel concentrate with a Ni grade of above 18 % and Ni recovery of above 87 %.This paper provides an overview of the optimization method for recovery of ferronickel from the thermal treatment products, through comminution and multi-stage magnetic separation.