PolyMet Selects Pressure Oxidation
as The Metallurgical Process for its NorthMet Project
GOLDEN, Colo., Aug. 10 /PRNewswire/ -- POLYMET MINING CORP. (Vancouver: POM -
news) has selected pressure oxidation (POX) as the metallurgical process for its NorthMet
polymetallic deposit in northeastern Minnesota. Full bio-leaching of NorthMet concentrates
resulted in high recoveries of base metals, but lower recoveries of platinum group metals (PGMs)
and gold than did POX. The Company also evaluated a hybrid process combining bio-leaching
and POX in order to improve PGM recovery. This alternative was economically competitive with
the POX process; however, after considering all NorthMet project factors, the Company has
chosen POX as the process for pilot plant testing.
PolyMet is presently optimizing the POX process developed through test work at Lakefield
Research and plans to further refine the process during continuous mini-pilot plant testing in
December 1999 or January 2000. Results of the pilot plant tests will be incorporated into the
pre-feasibility study expected in the first quarter of 2000.
The Company based the selection of the metallurgical process on estimated operating and capital
costs derived from an evaluation of flowsheets and recoveries from bench-scale metallurgical tests
of POX and bio-leaching run under laboratory conditions, as well as other major project factors.
Processing assumptions incorporated in the analysis of alternatives include: 1) the grade of ore
(millfeed) and associated recoveries, as determined in previous testing at Lakefield, would be as
stated in the table below; 2) ground ore would be processed in a flotation circuit to produce 1,200
tonnes/day of bulk concentrate; 3) the concentrate would be pressure leached in autoclaves at 220
degrees Centigrade; 4) PGMs and gold would be recovered from the leach solution; 5) copper
would be recovered as LME grade copper cathode in a conventional copper SX-EW circuit; 6)
nickel and cobalt would be sequentially recovered by solvent extraction, followed by
electrowinning of nickel to make cathodes, and the precipitation of saleable cobalt sulfide.
Copper Nickel Cobalt Platinum Palladium Gold
Ore (millfeed) 0.43% 0.12% 0.0096% 0.143 g/t 0.389 g/t 0.088 g/t
Recovery to
flot. conc. 94.6% 77.2% 46.0% 76% 76% 77%
POX Process
Recovery 97.5% 92.5% 92.5% 94% 94% 94%
Overall Recovery 92.2% 73.0% 42.6% 71.4% 71.4% 72.4%
The comparison of processing alternatives used capital and operating cost estimates developed by
O'Kane Consultants, Inc. in a July 1999 scoping-level report for PolyMet, and assumed a nominal
open-pit mining rate of 50,000 tonnes of ore per day. Metal prices used were US $0.65/lb.
copper, $2.45/lb nickel, $10.00/lb. cobalt, $350/oz. platinum, $330/oz. palladium, and $265/oz.
gold. At these metal prices, and based on the recoveries stated above, the Company calculates
approximate overall recovery from a tonne of mineralized material to be about US $15.90/tonne
including 50c for byproduct PGMs.
Given the above assumptions and project parameters, the O'Kane Consultants, Inc. report an
estimated project capital cost of US $500 million and a cash operating cost of $8.11/tonne. On a
copper equivalent basis, the operating cost is anticipated to be about 33c/lb. of copper. These
scoping-level cost estimates are preliminary and will be refined during preparation of the
pre-feasibility study.
Certain statements contained herein are ``forward-looking' statements within the meaning of
Section 21E of the Securities Exchange Act of 1934, as amended, and the Private Securities
Litigation Reform Act of 1995. Because such statements include risks and uncertainties, actual
results may differ materially from those expressed or implied by such forward-looking statements.
For further information, please contact Leslie Landefeld at the Company headquarters in Golden,
Colorado at (877) 233-4831 (toll free). You may also visit our web site at
www.polymetmining.com.
Signed,
DONALD W. GENTRY
President & CEO
This news release was prepared by Leslie Landefeld on behalf of PolyMet Mining Corp., which is
solely responsible for its contents. The Vancouver Stock Exchange has neither approved nor
disapproved the information herein.
Sounds like the news we have been waiting for. Anyone have a calculator?? |
