A History of Sherritt – Fifty Years of Pressure Hydrometallurgy at Fort Saskatchewan – by M. E. Chalkley, P. Cordingley, G. Freeman, J. Budac, R. Krentz and H. Scheie (Part 5 of 5)

Application of Sherritt’s Pressure Hydrometallurgical Technology to Other Metals

Much of Sherritt’s metallurgical and product technology developed over the last 50 years can be traced back to work done during the development of the ammonia leach process.  Pressure leaching of sulphide ores and concentrates, using continuous horizontal autoclaves, provided the basis for a thriving pressure hydrometallurgical process licensing business which offered processes for treating nickel mattes and concentrates, zinc concentrates, and refractory gold ores and concentrates.  The nickel reduction process perfected in the Ottawa pilot plant was subsequently licensed worldwide.

During the early 1950’s, following the successful commissioning of the nickel refinery at Fort Saskatchewan, Sherritt utilized its laboratory and pilot plant facilities in Ottawa to look for other potential applications for pressure leaching processes in the metals industry (14).  Laboratory tests were carried out on the pressure leaching of uranium ores and on the pressure oxidation of refractory gold ores, where the oxidative pressure treatment proved an excellent method for oxidizing pyrite and arsenopyrite to liberate the gold for subsequent recovery.

Two additional leaching plants were built by Chemico to treat cobalt concentrates in the aftermath of the Korean War, when the cobalt price was artificially high, but both plants became uneconomic as the price of cobalt declined, and closed in the early 1960s.  A fourth pressure leaching plant was the Port Nickel plant, constructed by Freeport to treat the nickel-cobalt sulphide from Moa.

In 1957, Sherritt purchased the interests of Chemico in all patents in the chemical metallurgical field in which Sherritt was involved. These patents covered inventions, which were made or developed during the period 1947 to 1956, leaving Sherritt as sole owner of jointly developed technologies. This included an assignment of the royalties from Freeport for the use of these patents in its plants under construction at Moa. An unfavourable development in 1960 was the action of the Cuban Government in taking over the Moa nickel operation. This deprived Sherritt of a source of revenue and made the license agreement covering the operation of this plant of doubtful value.  The Port Nickel plant was shut down and mothballed, until refurbished by Amax in 1974 as a refinery for nickel-copper matte.

During 1957, the Research and Development group demonstrated the feasibility of treating nickel matte by the Sherritt leaching and reduction processes (15). This was very important because it widened the potential supply of additional feed materials for the refinery at Fort Saskatchewan.  By the early 1960s the only surviving operating pressure leach plant was Sherritt’s nickel and cobalt refinery at Fort Saskatchewan.  Sherritt, under the technical leadership of Vladimir Mackiw, continued to develop the acid pressure leaching technology with a series of pilot plant campaigns on a variety of nickel and nickel-copper mattes.

These efforts paid off with overseas process license sales.  The acid pressure leach for nickel-cobalt sulphides was licensed to the Finnish nickel company, Outokumpu, in 1967.  Two years later the ammonia refining process for nickel concentrates was licensed to Western Mining Corporation in Australia, and a new acid leaching process for separating platinum group metals from nickel and copper sulphides was developed for Impala Platinum in South Africa.  By 1991, the latter process has been licensed to five major platinum producers in South Africa.  In 1996, the first North American plant, based on the flowsheet at the Western Platinum refinery was commissioned for Stillwater Mining Company in Montana, U.S.A.

By 1960, while always giving priority to technical assistance to the refinery operation, the Research and Development Division was broadening its activities to include treatment processes for zinc and lead.  In 1961, the first major custom pilot plant operation was undertaken, for Marinduque Iron Mines Agents, Inc., on copper-zinc concentrates from its mines in the Philippines, using the ammonia leaching process. The operation demonstrated the production of high purity copper powder, zinc carbonate and ammonium sulphate, but a commercial plant was never built.

Eldon Brown and Vladimir Mackiw had always believed that the eventual world supply of nickel would come from lateritic ores because the deposits of sulphide nickel ore would eventually be depleted. It was thus with Brown’s encouragement that Sherritt Research and Development in 1962 had started bench work on a laterite treatment process which by 1963 was ready for piloting. A new much larger pilot plant, or demonstration plant, was designed and built.

By 1969, Marinduque Mining and Industrial Corporation of the Philippines had acquired sufficient ore reserves from the Philippine government to justify a plant to produce 34 000 tonnes of nickel metal per year on Nonoc Island. Sherritt agreed to license its laterite process and know-how to Marinduque and to supply technical personnel and advice on the management and operation of the plant.  A 9 000 tonne sample of lateritic ore was shipped to Fort Saskatchewan for the pilot plant. Bechtel Corporation was retained by Marinduque to design the commercial plant that was built at Nonoc Island. Sherritt engineers were hired as consultants to Bechtel on the design and construction. In 1973 and 1974, Sherritt staff members and their families were transferred to the Philippines to participate in the final stage of construction and plant start-up. Sherritt Gordon acquired a 10% interest in the Marinduque Mining and Industrial Corporation.

Subsequently, demonstration runs were made for Le Nickel, the French nickel laterite mining company in New Caledonia, and for P.T. Pacific Nickel Indonesia on their laterite ore from Gag Island.

More recently in the 1990s, Outokumpu installed hydrogen reduction facilities for nickel production at the Harjavalta refinery in Finland (now owned by OMG). Further, Anaconda Nickel (now Minara Resources) in Western Australia adopted the Sherritt pressure acid leach (PAL) process as used at Moa, as well as hydrogen reduction for nickel and cobalt recovery (16).

In the 1970s Sherritt’s process research and development resources were spread more widely to include the treatment of both zinc and copper concentrates.  The successful zinc pressure leach process took many years of persistent and patient effort to reach commercial application.  This process, in which zinc sulphide is pressure leached in sulphuric acid solution at 150oC in an oxygen atmosphere to produce zinc sulphate solution and elemental sulphur, is an environmentally attractive alternative to fluid bed roasting, which produces sulphur dioxide.

The initial laboratory testwork, which identified the potential of the process, was carried out for Sherritt by Frank Forward and Herb Veltman at U.B.C. in 1958.  However the problems presented by the behaviour of elemental sulphur, which is molten at the leaching temperature, both in the leach itself, and during further treatment of the leach residue, were not fully resolved until the 1970s.  The process was piloted in 1976, and the first commercial plant started up at Trail, B.C. in 1981.  The second commercial plant was also in Canada, at the Kidd Creek operation at Timmins, Ontario that was commissioned in 1983.  The first overseas plant was built by Ruhr Zink in Germany in 1991.  Following that, a third Canadian zinc pressure leach plant was commissioned for Hudson Bay Mining and Smelting at Flin Flon, Manitoba in 1993, the first commercial application of the Sherritt two-stage zinc pressure leach process (17).

A technically and economically viable hydrometallurgical process for the treatment of copper sulphides has long been sought, primarily because of the concern for the environment with regard to sulphur dioxide emissions.  Since the late 1950s, Sherritt, as well as others, has expended considerable effort in the field of copper hydrometallurgy and had developed two potential processes both of which were successfully piloted at Fort Saskatchewan.  One was based on ammoniacal pressure oxidation leaching, followed by recovery of the copper from solution as refined copper powder by hydrogen reduction, and produces ammonium sulphate as a byproduct.  The other was based on sulphuric acid oxidation leaching and produces elemental sulphur as a byproduct.  Both processes, particularly the latter, are applicable to chalcopyrite, the most abundant and one of the most refractory copper sulphides (18).

In 1971, an intensive and cooperative research program was initiated jointly by Sherritt and Cominco to develop a versatile hydrometallurgical process for producing refined copper and recovering sulphur and other metal concentrates as byproducts from a variety of chalcopyrite containing copper concentrates.  After laboratory development of a process that appeared to be economically competitive with smelting, the Government of Canada and the two companies supported the construction, in 1975, and operation, in 1976, of a comprehensive pilot plant facility.  The process that resulted from this work is now known as the Sherritt-Cominco (S-C) copper process (19).

Sherritt’s interest in the pressure oxidation of pyrite containing ores and concentrates was revived in the late 1970s, in the work carried out with Anglo American Corporation of South Africa to develop a process for the pressure leaching of pyrite containing uranium ores.  Extensive piloting was carried out and a commercial plant was constructed, but never operated due to a depressed uranium market.  Sherritt was engaged from 1977 to 1980, by the Key Lake Mining Corporation, to assist in the development of a process for the very high-grade uranium-nickel-arsenic ores that this company had in northern Saskatchewan.  The process that was evolved for this application relied on mild pressure leaching in dilute sulphuric acid in the second stage of a two-stage system.  Milling of the ore commenced in October 1983 and full production was achieved, and surpassed, by May 1984 (20).

Pressure oxidation of refractory gold ores finally came into its own in the 1980s as a healthy gold price encouraged the exploitation of refractory gold ore deposits (21).  Sherritt has played a significant part in the commercialization of pressure oxidation for refractory gold ores.  Several pressure oxidation plants have been established since 1985 in the U.S.A. and Brazil (22).  Canada’s first installation, at Campbell Red Lake in Ontario was commissioned in 1991 (23).  Two plants were also commissioned in Papua New Guinea, the Porgera operation with startup in 1991 and further expansion in 1994, and the Lihir plant in 1997.

During the last 50 years, from conceptual research at the University of British Columbia, Sherritt Gordon Limited, the Chemical Construction Corp. and, later, many other locations, pressure hydrometallurgy has become well established worldwide.  It has provided the mining industry with very versatile tools to solve some of its most difficult problems in metal extraction and recovery from ores, concentrates and other intermediate products.  Pressure hydrometallurgy has now become a standard unit operation throughout the industry.


1.  D.G.E. Kerfoot, “Historical Metallurgy – The Development of the Sherritt Ammonia Pressure Leach Process”, CIM Bulletin, Vol. 82, No. 926, 1989, 136-141.
2. J.R. Boldt Jr. and P. Queneau, The Winning of Nickel, Longmans Canada Ltd., Toronto, Canada, 1967, 299-314.
3. Manitoba Industry Economic Development and Mines. http://www.gov.mb.ca/itm/mrd/min-ed/minfacts/history.pdf
4. F. A. Forward, C.S. Samis and V. Kudyk, “A Method for Adapting the Ammonia-Leaching Process to the Recovery of Copper and Nickel from Sulphide Ore and  Concentrate”, C.I.M. Trans Vol. LI, 1948, 181.
5. V. N. Mackiw, R.L. Benoit, R. J. Loree and N. Yoshida, “Simultaneous Distillation of Ammonia and Separation of Copper from nickel-bearing solutions”, Chem. Eng. Vol.  54, 1958, 79-85.
6. D.G.E. Kerfoot, “Process for the Separation of Cobalt from Nickel”, Canadian Patent, No. 2,068,982, 3 October 2000.
7. B. Benson and N. Colvin, “Plant Practice in the Production of Nickel by Hydrogen Reduction”, Proceedings of the AIME International Symposium on Hydrometallurgy,  Dallas, Texas, February 1963, 735-752.
8. V. N. Mackiw, W.C. Lin and W. Kunda, “Reduction of Nickel by Hydrogen from Ammoniacal Nickel Sulphate Solutions”, J. Metals Vol. 9, 1957, 786-793.
9. D.G.E. Kerfoot and P.D. Cordingley, “The Acid Pressure Leach Process for Nickel and Cobalt Laterite.  Part II: Review of Operations at Fort Saskatchewan”, Nickel  Cobalt 97, Vol. 1: Hydrometallurgy and Refining, W. C. Cooper and I. Mihaylov, Eds.,  CIM, Montreal, 1997, 355-370.
10. B. Willis and J. Von Essen, “Precipitation of Nickel Metal by Hydrogen reduction: A new perspective”, ALTA2000 Nickel-Cobalt –6 Conference, Perth, Australia, May 15- 18, 2000, 1-12.
11. (a) F. A. Schaufelberger, “Separation of Nickel and Cobalt Metal from Acidic Solution”, U.S. Patent, No. 2,694,005, 9 November 1954.
(b) F. A. Schaufelberger and P. J. McGauley, “Separation of Nickel and Cobalt Metal from Ammine Solution”, U.S. Patent, No. 2,694,006, 9 November 1954.
(c) F. A. Schaufelberger and A. M. Czikk, “Cobalt Pentammine Separation”, U.S. Patent, No. 2,767,054, 16 October 1956.
(d) F. A. Schaufelberger, “Cobalt Pentammine Sulfate Separation”, U.S. Patent, No. 2,767,055, 16 October 1956.
12. V.N. Mackiw and T.W. Benz, “Application of Pressure Metallurgy to the Production of Metallic Cobalt”, Extractive Metallurgy of Copper, Nickel and Cobalt, AIME  International Symposium, P. Queneau, Ed., Interscience Publishers, New York, 1961, 503-534.
13.  M.E. Chalkley and I.L. Toirac, “The Acid Pressure Leach Process for Nickel and Cobalt Laterite.  Part I: Review of Operations at Moa”, Nickel Cobalt 97,Vol. 1:  Hydrometallurgy and Refining, W. C. Cooper and I. Mihaylov, Eds., CIM, Montreal, 1997, 341-353.
14. V.N. Mackiw, R.M. Berezowsky and D.G.E. Kerfoot, “Recovery of Nonferrous Metals by Pressure Hydrometallurgy”, 41st Canadian Chemical Engineering Conference,  Vancouver, Canada, Oct 6-9, 1991.
15. M.J.H. Ruscoe, “Sherritt Research: A History of Achievement”, unpublished paper, Fort Saskatchewan, Alberta, Canada, December 5, 1996.
16. G. Motteram, M. Ryan and R. Weizenbach, “Application of the Pressure Acid Leach Process to Western Australian Nickel/Cobalt Laterites”, Nickel Cobalt 97,Vol. 1:  Hydrometallurgy and Refining, W. C. Cooper and I. Mihaylov, Eds., CIM, Montreal, 1997, 391-407.
17. E. Ozberk, W.A. Jankola, M. Vecchiarelli and B.D. Krysa, “Commercial operations of the Sherritt zinc pressure leach process”, Hydrometallurgy, Vol. 39, 1995, 49-52.
18. W. Kunda and R. Hitesman, “The Reduction of Copper to Powder from its Aqueous Ammine Ammonium Sulphate System using Hydrogen under Pressure”, Paper  presented at the American Inst. Of Chemical Engineers 64th Annual Meeting, Nov.28 – Dec. 2, 1971.
19. G.M. Swinkels and R.M.G.S. Berezowsky, “The Sherritt-Cominco Copper Process, Part 1: The Process”, Paper presented at the 16th Conference of Metallurgists of the  Metallurgical Society of CIM, Vancouver, British Columbia, Aug. 21-25, 1977.
20. D.R. Weir and I.M.Masters, “The Key Lake Uranium Process, Part 1: Uranium Extraction”, Paper presented at the CIM Conference of Metallurgists, Halifax, N.S., Aug.  24-28, 1980.
21. D.R. Weir and R.M.G.S. Berezowsky, “Recovery of Gold from Refractory Auriferous Iron-Containing Sulphidic Ore”, U.S. Patent, No. 4,571,264, 18 February 1986.
22. R.M.G.S. Berezowsky and D.R. Weir, “Refractory Gold: The Role of Pressure Oxidation”, Gold Forum on Technology and Practices – World Gold ’89, R.B. Bhappu and  R.J. Hardin, Eds., Littleton, CO: SME 1989, 295-304.
23. J. Frostiak, R. Raudsepp and R.F. Stauffer, “The Application of Pressure Oxidation at the Campbell Red Lake Mine”, Randol Gold Forum ’90, Squaw Valley, CA, Sept.  13-15, 1990.

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