This chloride leaching process recycles resources

Outotec Oyj (Espoo, Finland; www.outotec.com) has developed a new chloride-based leaching process for recovering nickel from nickel matte — a commercial intermediate product of nickel smelting that contains about 65% of nickel. Developed since the 1980s, originally for Cu recovery and since extended to Ni, Zn and Au, the Outotec Nickel Matte Chloride Leaching process is a more resource-efficient and environmentally sustainable option for Ni refining compared to existing leaching processes, says Kaarlo Haavanlammi, technology manager — Nickel Hydrometallurgy. Besides Ni matte, the process can be modified to treat all sulfidic nickel concentrates, as well as low-grade sulfides (<5% Ni), says Haavanlammi. The new process (flowsheet) is based on a calcium chloride solution, which enables easy acid (HCl) and base (NH3) regeneration in the process. Leaching is performed in acidic conditions (pH low enough to prevent Fe precipitation), using HCl solution from acid regeneration, and the addition of O2 (to prevent H2 formation). Leaching is performed in multiple steps at near boiling point temperatures and atmospheric pressure for 10–15 h. After leaching, the metals (Fe, Cu, Co and Ni) are recovered from the chloride solution…