Process Design for Direct Production of Battery Grade Nickel Sulfate

The clean energy transition has increased the global demand of nickel sulfate used in the Li-ion batteries. A short-term solution is to refne the nickel sulfate product from nickel intermediates. In the long-term, new direct nickel sulfate productiontechnologies are needed. This research focused on the modeling-based concept development of a novel direct hydrometallurgical nickel sulfate process consisting of chemical leaching, impurity removal by precipitation, solvent extraction, andcrystallization as an alternative to the conventional nickel sulfate production route via a nickel matte intermediate. The conventional process route with the studied nickel concentrate had lower chemical consumption and waste production comparedto direct hydrometallurgical process where approximately 60% of iron was leached consuming oxygen, and the following ironprecipitation step consuming calcium carbonate resulted in a high amount of iron precipitate together with gypsum. However,hydrometallurgical alternatives are often suitable for lower ore grades or volumes and can recover copper as by-productmetal. The biggest impacts on carbon footprint from chemical consumption in the direct hydrometallurgical process weregenerated in iron precipitation and oxygen use in leaching. With the studied nickel concentrate, pyrrhotite played a key rolein both oxygen use and iron precipitation. In the leaching step, 68% of total oxygen consumption was related to pyrrhotiteleaching, while in iron removal 73% of total iron originated from pyrrhotite. Thus, especially pyrrhotite removal prior toleaching needs to be developed to reduce the carbon dioxide footprint, when the pyrrhotite content in the material is high.