(MERAF) for the Base Metals Smelting Sector - CCME

3.2.4. Inco Limited, Thompson Division, Thompson, Manitoba 82
Figure 7 and Figure 8 contain schematic block flow diagrams for the Nickel
Smelter and Nickel Refinery respectively. Each shows the general sequence of
the major unit operations, from the receipt of raw materials to the production of
metals. When these unit operations are referred to in the text, the corresponding
words starts with an upper case letter. These diagrams are highly simplified and
are included solely to aid in the discussion and understanding of the pollution
control at the facility.
3.2.4.1. Nickel smelter
The concentrate slurry is pumped from the flotation section of the mill where it is
thickened to the roaster building where it is filtered. The fluid bed roasters
oxidize approximately one-half the concentrate's sulphur and its associated iron.
Flux is also added to the roasters.
Most of the roasted concentrate is carried out of the roasters by the off-gas. The
roasted concentrate, or calcine is separated from the off-gas in cyclones and
electrostatic precipitators. The treated off-gas is then discharged directly to the
atmosphere via the main smelter stack.
The calcine is fed into electric furnaces where it separates into slag (oxide) and
matte (sulphide) phases. The slag is skimmed, granulated with water and then
pumped to the slag storage area.
The finished matte from the converters is cast as anodes for further processing in
the Inco Thompson Refinery. Off-gas from the converters also pass through
electrostatic precipitators and to the main smelter stack.
High copper concentrates are treated separately to produce high copper calcine
which is sent directly to the Inco smelter in Sudbury.
3.2.4.2. Nickel refinery
Matte anodes are transferred to the Nickel Refinery where they are electrorefined
in electrolytic tanks to produce high purity nickel cathodes. The tanks
contain a standard chloride-sulphate solution as the electrolyte. The cathodes
are washed and then sheared into pieces for the markets. Trademark products
are also produced. INCO S-ROUNDS and INCO R-ROUNDS are button shaped
products which are flat on the back and about one inch in diameter.
By-product residue is sent to Inco’s Port Colborne Refinery for cobalt and
precious metal recovery.
Excess water is treated with lime to precipitate heavy metals and their releases
to the environment.
82 Hatch Associates, Review of Environmental Releases for the Base Metals Smelting Sector,
prepared for Environment Canada, dated November 2000
62