Outokumpu Harjavalta Metals Oy has been producing nickel since 1962,
based on conventional flash smelting technology followed by
electrowinning of nickel. In the 1980s, a research project was initiated to develop a converterless
direct smelting process to produce matte for further refining in the then
existing refinery. The process was tested on a pilot plant scale at
Outokumpu's research centre in Pori and was found to be viable. The
process was named the Direct Outokumpu Nickel Smelting Process or the
DON Process. At the turn of the 1990s, Outokumpu studied various options to
develop its nickel business and the Harjavalta operations. As a result of
this work, the DON Process was further developed to produce two mattes:
low iron matte in the flash furnace to be leached in the existing leaching
circuit and high iron matte in the electric furnace to be leached in the new
leaching circuit. In Harjavalta's case, it was essential and important that
the process could use the existing flash furnace and electric furnace
without converters.