5328103 Process for impact crushing of rock and ore lumps and an apparatus for performing same

Abstract

Two different nickel sulfide intermediates must be refined to pure nickel and cobalt products: sulfide matte from nickel sulfide smelting and converting and sulfide precipitates from nickel laterite leaching. These data indicate that hydrometallurgy is the principal method for making high-purity nickel from these mattes and sulfide intermediates. The objective of this chapter is to describe the overall hydrometallurgical processes used to refine mattes and sulfide intermediates. Sulfide precipitates are refined to nickel and cobalt at following refineries; Fort Saskatchewan, Canada (Sherritt); Murrin Murrin, Australia (Minara Resources); and, Niihama, Japan (Sumitomo). Nickel is leached from laterite ores and precipitated as a sulfide. The objectives of the leaching stage are to extract the nickel and cobalt into solution, to oxidize the cobalt so that it is present as cobaltic hexamine. The filtrate is sent to ammonia stripping while the solids are sent to the cobalt circuit. The solution from the cobaltic hexammine precipitation is treated to reduce the concentration of ammonia in two steps: stripping with air and distillation. This solution passes through four reactors known as the ‘copper boil’ where copper is removed. Elemental sulfur and sulfur dioxide are added to the second reactor, which results in the precipitation of copper as copper sulfide. The processing of nickel–copper mattes is significantly different from the processing of mixed sulfide precipitates. This difference arises from the need to separate nickel from copper in the refinery. The Nikkelverk refinery at Kristiansand, Norway, uses chloride chemistry to refine nickel–copper matte. The Norilsk refinery at Harjavalta, Finland, uses sulfate chemistry to refine mattes that are relatively low in copper.