HYDROMETALLURGY

Leaching nickel and cobalt from lateritic and sulphide deposits via atmospheric, pressure oxidation or metathesis processes. The leach products can be taken through purification using solvent extraction, precipitation and ion exchange process to crude and pure semi-products such as hydroxides, carbonates and salts or refined to metals using divided cells, for example.

Leaching copper from low and high grade oxide deposits via heap leaching and tank leaching, as well as sulphide concentrate leaching via low and high temperature pressure oxidation processes. Copper concentrate recovered to metal via SXEW, or direct EW, is the standard processing route. However, Orway can also assist in helping clients to produce super concentrates from dirty concentrates with the concomitant clean-up and removal of uranium, cobalt, arsenic and other deleterious elements from copper sulphide concentrates.

Design and operational experience in the refining to 4N purity, platinum group metals and gold. Feed sources are typically concentrates from mattes and secondary feed stocks (spent automotive catalysts).

Processes include classical chloride systems and newer technologies incorporating substituted quaternary ammonia salts (SQAS).

Working with major mining houses and junior companies, the team is familiar with designing to air quality standards set out by NIOSH and ACGIH.

Services in uranium, including expertise in design and operations with calcrete, sandstone, granitic and sulphide hosted deposits across the globe. We can assist at any required stage of a uranium project, from scoping level to design. Through testwork, analysis, detailed mass balance modelling and the application of specialist expertise, processing options are assessed to determine the best extraction methods and optimal process flowsheet. The team routinely scope and supervises testwork programs and pilot plant trials using acid or alkali leaching methods followed by solvent extraction or ion exchange concentration.

Testimony to the expertise of Orway's team in providing expert advice in the uranium sector is shown by assistance to the International Atomic Energy Agency (IAEA) in developing countries.

The team can specify testwork, supervise pilot plant trials and interpret data to ensure the correct flowsheet selection for the project. The engineering implementation of the flowsheet is also important in incorporating the team's practical experience to assist clients through engineering, materials selections and commissioning to ensure the project is a success.

Orway specialises in all aspects of gold processing. Our team has extensive expertise in testwork design, engineering and operational support, offering a range of services, including:

• Liaising with geologists to ensure testwork sample selection is representative of spatial distribution and variability envelopes

• Specification and supervision of testwork programs to determine optimal extraction conditions such as grind size, oxygen addition and reagent optimisation. Refractory gold, high copper and preg-robbing ores can be problematic and Orway has the experience to address these issues

• Gravity gold extraction and downstream processing through intensive cyanidation leaching or gravity finish

• Leach/adsorption circuit specification and operation such as tank residence time, operating densities, reagent addition, carbon management and GIC accounting

• Refractory gold processing through preconcentration, oxidation process (POX, BIOX, Roasting), fine grinding and leaching

• Desorption circuit specification and operation such as AARL, Zadra, Merrill Crowe, as well as electrowinning cell operations, current density, sludging cells operations and carbon regeneration

• Gold room layout, operations and smelting

• Auditing and operations reviews to ensure best practice. Gold loss deportment and recovery improvements

• Cyanide destruction testing, circuit specification and optimisation

• Process design (PDC, P&IDs, equipment selection, layout and control philosophy)

• Commissioning support

Metals often occurring in conjunction with value metals Cu, Ni, and PGE include Pb, Bi, As, Sb, Se, and Te. These commodity types typically need to be recovered as by-products or precipitated stable compounds in tails stream. Our experience includes different types of leaching and recovery processes, including:

• Pressure oxidation

• Pressure metathesis

• Alkali sulphide leaching

• Pressure nitrogen process

• Pressure alkali leaching

• Immobilised to satisfy legislation

• Selenium

• Tellurium recovery using precipitation and reduction processes