GOLD EXTRACTION constraints could unlock more value from ores at lower costs in a process that is inherently environmentally responsible, being free from the use of cyanide and with no emission of sulphur dioxide to the atmosphere. Greenhouse gas emissions are also significantly lower than for conventional smelting and refining processes. Also, the process does not require expensive fine grinding or attrition reactor pretreatment to achieve high metal recoveries. The Kell Process is an alternative to concentrate treatment at a smelter and warrants serious consideration in any primary PGM, refractory gold, copper-gold or polymetallic project or operation. The process has been termed the“ next step change” towards the highly efficient and clean recovery of precious and base metals concentrates.
Dundee Sustainable Technologies( DST) has developed a chlorination process as an alternative to the conventional cyanidation process for the extraction of precious metals from ores or concentrates. DST says“ the technology offers viable and efficient gold recoveries and the ability to handle refractory ores and contaminated material( As, Hg, etc).” The process has been successfully demonstrated on hundreds of samples provided by various mines, exploration and development projects and has evolved from laboratory experiment to demonstration at an industrial scale.
A gold bearing pyrite concentrate was treated at the demonstration scale( 15 t / d) for the extraction of gold using the process. The pyrite was depressed in the flotation circuit in order to promote the flotation of copper and to achieve a sufficient copper grade to meet the copper smelter criteria. However, the recoveries of copper were 80 % and only about 50 % for the gold was found in the copper concentrate. The balance of the gold( 50 %) and copper( 20 %) contained in the pyrite concentrate as a reject from an overall flotation circuit. The grade in the pyrite concentrate is 5.40 g / t Au and about 0.77 % Cu. About 170 t of pyrite concentrate were processed in the DST demonstration plant. The concentrate was first oxidised using a fluid bed to produce a calcine. Copper was then extracted as copper sulphate using diluted sulphuric acid. The residual solid was submitted to the DST chlorination process for gold extraction. Thereafter, the gold was recovered from the pregnant brine by precipitation over silica using DST proprietary process. The maximum gold recovery by chlorination was 90 %. The average gold recovery by cyanidation of these calcines was 71 %. commercially proven, economical, efficient and environmentally friendly.
The company offers three areas of expertise: The Recyn process for cyanide recovery and detox; the Gold Room for innovative gold and silver recovery solutions for carbon circuits; and a Non-Chemical System( NCS) process incorporating the new InCon centrifugal concentrator.
Recyn is a specialist technology offered for the recovery of cyanide and dissolved metals from precious metal plant process streams. The process is based on the use of a functionalised resin bead, pre-treated to allow the dual duty of recovering free and complexed cyanide ions from solution with a high degree of efficiency. The GGT Treatment Plant is custom designed for each
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operation to match the various solution chemistries and throughputs. The two areas of cyanide recovery and metal detoxification are balanced to achieve the desired compliance levels. Equally applicable to slurries and solutions, Green Gold says“ the process is technically and economically superior to all others currently available for the detoxification of gold plant tailings.”
Carbon-based flow sheets( Gold Room) include innovative processes that increase metal recovery and reduce operating costs.
NCS retrieves gold and silver that is otherwise lost in the tailings dam. It offers enhanced, backend metal recovery using specialised sizing and gravity equipment designed and built by Green
Green Gold
Green Gold designs, develops and integrates technological innovations that maximise gold, silver, and cyanide recovery. Its products are
AUGUST 2017 | International Mining 45