South African gas and welding products supplier, Afrox will use the Electra Mining Africa 2010 event as a platform to showcase its expertise as a technical solutions provider.
Afrox business manager for industrial gases Carte Lubbe explains that the company has always been more than simply a supplier of gas and welding products and it will use the show as a platform to emphasise its extensive product range and process solutions offerings.
“We offer process solutions to four main industry sectors, namely metals, food and beverages, chemicals” says Lubbe.
“We have a team of dedicated application engineers who are all experts within their specific arenas and are trained within that environment to ensure they are able to understand the needs and challenges facing clients.”
An area on which the company is placing strong emphasis is that of water treatment, with it applying its experience and skills to develop a gas based solution to the problem of acid mine drainage (AMD).
Lubbe explains that the process is essentially the oxidation of the ferrous iron to ferric iron, followed by pH adjustment, resulting in the precipitation of the iron as a brown iron hydroxide sludge. Once the water is clarified it can be economically reused in the gold plant leach circuit, thereby making a substantial saving on cyanide and water usage.
In 2007, a West Rand gold mine began operation of a water treatment plant to treat AMD water arising from both underground and surface runoff, which is currently stored on the mine with oxygen supply from Afrox.
Afrox’s manufacturing industries process development team also assists with developing innovative solutions to repair and protect equipment used in this highly corrosive environment.
During this year, the company has expanded its Goldox suite of technologies with the addition of a new leach feed diagnostics system developed for infield evaluation of oxygen demand characteristics.
Goldox is the process offered by Afrox which uses oxygen in cyanide gold leaching. It was first introduced to South African gold mines in the mid-1980s and is now used by mines in North America, Australia and South America, establishing it as an internationally-proven technology.
The Goldox process performs a dual function. Through the introduction of pure oxygen in the preconditioning stage to the ore slurry, the dissolved oxygen concentration is increased, reducing the ore reactivity. This results in an increased gold leaching rate, which improves gold recovery and profitability.
Part of the Goldox offering is a complete analysis by Afrox specialists of customer processes to determine the suitability of the technology and to establish the best approach to maximise its performance.
As Afrox applications engineer Rob de Zoeten explains: “Goldox is more than simply a supply of oxygen to gold mine process plants. It is a complete solution, backed by technical expertise, which maximises customer returns from invested capital.”
With the company already supplying oxygen through the Goldox application to most mining facilities, it began to explore utilising ozone for cyanide destruction.
As a first step in commercialising the use of ozone in cyanide destruction, Afrox embarked on trials at various leaching operations utilising an existing Afrox Goldox oxygen supply facility, which simplified execution of trials.
The trials were conducted on the gold plant tailings prior to deposition on the tailings dams. Ozone was produced using on-site gaseous oxygen and portable generators. The ozone gas produced was then injected using spargers into the tailings to ensure optimal reaction efficiency before it was pumped into the tailings dams. Samples were taken at the pumps and analysed for free cyanide to determine the effectiveness of the cyanide destruction.
The results were very encouraging, suggesting that using ozone in cyanide destruction could prove to be a viable process route for gold plants with available oxygen wishing to reduce cyanide levels in their tailings.
In addition, Afrox’s parent company The Linde Group is developing technology which will significantly improve the efficiency of converting oxygen to ozone, thereby reducing the operating costs of using ozone for cyanide destruction.