In mid-January, I attended the 49th annual Canadian Mineral Processors Conference in Ottawa. CMP had over 500 delegates from across Canada, and countries including Australia, UK, USA, Mexico, South Africa and Finland. There were many papers that focused on innovation and sustainability in mining themes.
The conference opened with a presentation by Dominic Fragomeni, “The Need to Innovate: Celebrate the Past…Look to the Future”. He described some of the successful innovations in mineral processing such as adoption of fine grinding stirred mills, alternative flotation machines, and advanced process techniques for refractory gold ores, such as non-cyanide leaching (e.g. thiosulfate), pressure oxidation and the Albion fine grinding and leach process. Dominic posed the question about innovation in mineral processing – “is our effort too fragmented?” (in my opinion, yes!), and reiterated the need for collaboration to solve complex challenges facing the mining industry.
Two papers were presented on ore sorting, which has the potential to substantially reduce the energy and water consumption per unit metal produced from an ore. Brent Hilscher (Sacre-Davey) showed some promising results of sorting silver, gold and zinc ores using XRF (X-ray fluorescence) and XRD (X-ray diffraction) detectors. In one case, a silver mine in Peru, ore sorting allowed the mine to decouple mining method and cut-off grade from mill feed grade, resulting in higher resource recovery and lower operating cost. Therefore, the mine didn’t have to shut down. Other applications included scavenging high grade rocks from otherwise uneconomic waste piles. In one of these cases, this also had the benefit of lowering the gold associated sulfide content of the pile to prevent it from producing acid rock drainage - a win for both profit and the environment. A second sorting paper on pre-concentration of gold bearing quartz ores was presented by Jorn Rohlender (Outotec). The paper described the process for determining the amenability of an ore to sorting, then different levels of pilot tests to confirm viability of a full-scale installation. Case studies of orogenic gold deposits in Northern Europe were presented. Tests suggested that typically 75 – 90% of gold could be recovered by rejecting 55 – 35% of weight in the feed, resulting in head grade upgrade ratios of 1.9 to 1.4. The benefits included increased resource recovery, reduced transport costs from satellite deposits and lower energy requirements for grinding.
Two papers were presented on cyanide destruction, which is an important unit operation to ensure that gold mines can maintain environmental compliance, and minimize the potential harm to bird and aquatic species surrounding their sites. Anca Nacu (Kemetco Research) described the different demonstrated cyanide destruction technologies and the advantages and disadvantages of their applications. The importance of test work and need to consider site specific conditions were emphasized. Neri Roux (Research and Productivity Council) described cyanide destruction investigations at Anaconda Mining’s Point Rousse gold project. It was found that by segregating the two residue sources, implementing new monitoring instrumentation and adding reagent addition controls, sodium metabisulfite (MBS) reagent addition could be reduced significantly, saving money. Further reductions were demonstrated with addition of ozone in conjunction with these changes.
Gabriel Garcia Curiel (Dundee Sustainable Technologies) presented a new method to stabilize arsenic from copper concentrates. This addresses a serious issue in the global copper and gold industries – a rising tide of arsenic that is coming from increasingly complex ores that contain arsenic bearing copper minerals such enargite (Cu3AsS4), tennantite (Cu12As4S13) and arsenopyrite (FeAsS). The technique sequesters arsenic by vitrification into a stable glass phase. The technique, which has been tested in a demonstration plant in Quebec, appears to be significantly cheaper than existing hydrometallurgical techniques that stabilize arsenic into the crystal phase, scorodite. This may make the difference between leaving a copper deposit in the ground, or mining and processing it economically and in an environmentally acceptable manner.
Peter Mehrert (ALS) presented laboratory and pilot plant results from the HydroFloat (TM) technology that showed potential for substantial increases in the recovery of copper sulphides at coarse sizes (> 400 um). This technology may eventually support plants in reducing power requirements through increasing grind size prior to flotation, while maintaining metal recoveries. This results in lower GHG emissions, and makes tailings easier to dewater, which in turn can reduce costs and risks associated with tailings disposal.
Several other papers covered flowsheet and equipment developments to improve metal recovery and product quality, including flash flotation, the use of fine grinding and Jameson cell technology to increase nickel grades at an Australian mine, and pyrite leaching of tailings at Penasquito mine in Mexico.
During the networking breaks, I met some eager students and shared my perspectives on careers in mining, and the importance of sustainable practices in maintaining a viable mining industry. Overall, the CMP was an excellent conference. It was great to meet both old and new colleagues, learn about industry innovations, and reinforce the message that sustainable business is good business.