Wet Milling

12

Plant being constructed

Construction of a wet milling pilot plant
capable of producing 1,000 tonnes of
fibre per annum commenced in
December, 1987 and is scheduled for
completion by mid-year. The decision to
proceed with this plant is based on
encouraging test results obtained from
the operation of a small scale pilot
facility and the positive reaction of
customers to the fibre produced. The
new plant will allow Cassiar to supply
customers with sufficient quantities of
fibre for commercial testing while
obtaining operating experience and
design criteria for a commercial size wet
milling plant. Minor modifications and
additions can increase the new pilot
plant production to 5,000 tonnes of fibre
per annum which would result from
treating one-third of the mill's current
tailings. When the new process is tested
and proven to be successful by treating
current tailings, the potential exists for a
larger scale operation using material
from the tailings stockpile. An
additional module could be added
relatively inexpensively to increase the
total fibre production of the plant to
10,000 tonnes per year.

Available stockpile

Because of the limited grades of fibre
extracted from the Cassiar ore during
the initial twenty years of operation, the
mill tailings stockpile contains
considerable quantity of fibre. An
evaluation conducted in 1981 established
that the tailings stockpile consists of
approximately 14 million tonnes having
an average grade of 3.5%. This tonnage
is sufficient to permit the recovery of
more than 300,000 tonnes of fibre by
using the wet milling process.

Cost effective

Cassiar developed the wet milling
technique with assistance from the
Federal Government. The process allows
the extraction of shorter fibres without
the costs of drying the mill feed which is
required for conventional dry milling
techniques. In addition to low energy
costs, and the low cost of recovering
mill feed from available tailings, the new
process, being wet, will not require the
stringent dust control measures used in
conventional milling.