The history of world nickel production has been affected significantly by
the supply and demand situation and fluctuation of LME price of nickel
metal. In the beginning of the 1980s, the decline of price and demand
lead to the withdrawal of un-competitive producers and the shrinkage of
the production capacity. During the same period, Sumitomo Metal Mining maintained the
production level with continuous improvement of the traditional matte
electrorefining process. However, Sumitomo has recognised that the
continuous improvement alone does not promise us the ability to catch up
with rapid changes in the world. In the meantime, Sumitomo intensively
researched chloride hydrometallurgy and has developed the chloride
process for the nickel refining. This includes the solvent extraction and
chloride electrowinning in the mixed sulphide process and the chlorine
leach of the anode slime arising from matte electrorefining. In the late-1980s, Sumitomo Metal Mining decided to develop a new
nickel refining technology based on chloride hydrometallurgy. The new
process was designed from the comprehensive aspects involving safety
and the environment. Construction of the plant for the matte chlorine
leach electrowinning (MCLE) process was commenced in 1991. The
MCLE plant with a capacity to 2000 tonnes per month has been
commissioned at Niihama since 1992. The process has provided high
productivity, overall good economics and high quality of electrolytic
nickel produced. After the establishment of the process, Sumitomo has
maintained continuous improvement of the new process and has attained
the best practice of the work classification.