Sherritt is a recognized leader in the application of pressure hydrometallurgy and has more than 60 years of experience in the development and commercialization of hydrometallurgical processes for the recovery of metals. With a long history as an operator of pressure hydrometallurgical circuits, we use our expertise to help clients unlock the value in ores and concentrate feeds. This covers a range of services including:
A number of commercial plants are currently operating using our proprietary technologies which include the following core processes:
We also work with clients to develop and commercialize processes for the recovery of copper, gallium, indium, lead, molybdenum, silver and vanadium, and for the removal of undesirable elements such as arsenic, cadmium, chromium, iron, manganese, selenium, silicon and tellurium. Recent process development studies have included pressure oxidation of copper concentrates, as well as pressure oxidation of copper-arsenic feeds to recover copper while fixing the arsenic as a stable residue. We are confident we can help your company develop the right process.
High pressure acid leaching (HPAL) has been developed by Sherritt for recovery of nickel and cobalt from nickel laterite deposits (1 to 3% Ni). Laterite ore is leached at high temperatures (245 to 260ºC) with sulphuric acid to extract nickel and cobalt into solution. After liquid solid separation and solution purification, nickel and cobalt are precipitated as a mixed sulphide intermediate with H2S gas. This intermediate is then refined to produce pure nickel and cobalt metals, using flowsheets based on either acid or ammoniacal leaching of the mixed sulphides.
Sherritt is a major producer of nickel and cobalt using HPAL technology. The Moa Nickel plant has been in continuous operation since 1960 and has been operated as a joint venture between Sherritt and General Nickel since 1994. Sherritt is also the operator for the Ambatovy Nickel Joint Venture in Madagascar, which began commercial production in 2014.
Sherritt provided support in the development of the following commercial HPAL projects, including the licensing of Sherritt’s HPAL and mixed sulphide refining technology for the Murrin Murrin plant.
Hydrogen reduction of nickel and cobalt was developed by the Chemical Construction Company as an alternative to electrowinning for the production of nickel and cobalt metals. [Sherritt obtained the technology, which was subsequently used in the Fort Saskatchewan operation.] High purity nickel and cobalt powders are produced by the following reactions in high pressure autoclaves. Ammonium sulphate is produced as a valuable by-product of this process.
NiSO4 + 2 NH3 + H2 → Ni + (NH4)2SO4
CoSO4 + 2 NH3 + H2 → Co + (NH4)2SO4
This process is highly versatile and has been integrated with acid and ammoniacal leaching flowsheets for the treatment of nickel-copper mattes and for the treatment of mixed nickel-cobalt sulphides from high pressure acid leach (HPAL) operations.
Sherritt’s hydrogen reduction technology has been operating commercially for over 60 years, including at the following plants:
Many gold ores and concentrates contain fine gold particles locked within sulphide minerals, such as pyrite and/or arsenopyrite, which make this gold unavailable for recovery by conventional cyanide leaching. Sherritt pioneered the use of pressure oxidation technology to treat these refractory sulphide ores and make the gold amenable to recovery by cyanide leaching, including the first commercial application at Homestake’s McLaughlin mine in California in the early 1980s.
Sherritt’s pressure oxidation process has several advantages over other processes used commercially to treat refractory gold feeds:
Sherritt’s refractory gold process has been operating commercially for over 30 years, including at the following installations that are currently in operation:
Sherritt’s matte leach process uses sulphuric acid leaching in a combination of atmospheric and/or pressure leaching steps to quantitatively dissolve nickel and copper in nickel-copper matte and produce a high-grade platinum group metal (PGM) concentrate for refining.
Sherritt’s matte leach process has been operating commercially for over 40 years and most of the world’s platinum supply is recovered from matte treated with this process. Sherritt has worked with PGM producers to tailor the process to accommodate differences between plants in matte composition, impurity content, PGM deportment and desired products, including nickel and copper cathodes, nickel powder (hydrogen reduction), crystalline nickel sulphate, and copper sulphides.
The following commercial base metals refineries currently employ Sherritt’s matte leach technology:
Sherritt developed the Sherritt Zinc Pressure Leach Process, in conjunction with Cominco Ltd, as an alternative to conventional zinc roast-leach technology. Direct pressure leaching of zinc concentrate by the following reaction allows zinc to be recovered as zinc solution amenable to conventional purification and electrowinning, while producing elemental sulphur, which can be sold and/or stockpiled, and a solid residue containing impurities, such as iron and silicon.
ZnS + H2SO4 + ½ O2 → ZnSO4 + H2O + So
The process can be readily integrated with existing roast-leach plants or it can be used to replace roasting entirely in a new installation. The advantages of the Sherritt Zinc Pressure Leach Process include:
The Sherritt Zinc Pressure Leach Process has been operating commercially for over 30 years. The following installations currently utilize Sherritt’s zinc pressure leaching technology:
Sherritt has adapted elements of its proven pressure acid leach technology for zinc concentrates, which has been successfully applied commercially in five operating plants, or similarly, adapted elements of high temperature pressure oxidation technology, used in numerous commercial gold operations, in developing viable processes for treating chalcopyrite concentrates. Sherritt has extensively tested medium and high temperature pressure leaching of copper feedstocks in continuous integrated pilot plant operations, from pressure acid leaching through to copper electrowinning. High copper extractions and the production of residues amenable to high recoveries of gold and silver have been demonstrated.
Sherritt’s moderate temperature pressure leach process for chalcopyrite concentrates, largely patterned after its zinc pressure leach process, involves leaching in solvent extraction raffinate or spent electrolyte, under oxygen pressure at 150°C. Small amounts of coal are added as a dispersant to prevent agglomeration of unreacted sulphides with elemental sulphur; this additive is an essential part of the process.
With a fine grind, copper extraction of greater than 98% is readily attainable in a single pass. Alternatively, conditions may be adjusted to limit copper extraction to about 85 to 90% in a first pass leach, followed by recovery of the unleached sulphides by flotation and removal of elemental sulphur, and recycle of the recovered sulphides to the pressure leach; overall copper extraction of greater than 98% is also achievable. The pregnant pressure leach product solution is processed by conventional solvent extraction and electrowinning to produce high-grade copper cathode. Elemental sulphur is separated from the flotation concentrate by melting and filtration. Gold is recovered in high yield, along with a portion of the silver, from the flotation tailings by treatment with lime and conventional cyanidation.
In high temperature pressure leaching of chalcopyrite concentrates, typically carried out at temperatures in excess of 200°C, sulphide sulphur in the concentrate is almost completely oxidized to sulphate sulphur. Oxidation of all sulphides to sulphate means the process is a net sulphate generator and if an acid source is required for a nearby process, e.g., heap leaching of oxide ore, then a savings on neutralization reagent is realized.
Telephone: 1 780 992 8000