UK stock market listed mineral processing technology company, Alexander Mining, is moving closer to commercializing a new way of extracting a range of non-ferrous metals from their ores that is more cost effective and environmentally friendly than conventional methods.
The proprietary process known as AmmLeach, which is ideally suited to oxide ore bodies containing copper, cobalt and zinc rather than ferrous metals such as iron, should, if all goes according to plan, see the first pilot plant up and running by the middle of next year. The process has already successfully gone through the development and feasibility study stage at the company’s former copper project in Argentina.
“Alexander Mining has already announced opportunities for the use of its technology with two Canadian/Australian stock exchange listed mining companies, Anvil Mining and Tiger Resources, which have mining projects and operations in the Democratic Republic of Congo (DRC),” said Martin Rosser, CEO of Alexander Mining.
The deal with Anvil Mining is a joint venture (JV) agreement to build and operate a pilot plant to treat a total of 150,000 tonnes of cobalt ore at Anvil’s Mutoshi project. The pilot plant will utilize Alexander’s AmmLeach to process ore for the production of cobalt metal.
Under the terms of the JV, the construction and development of the pilot plant is conditional upon Alexander Mining obtaining financing and Anvil will be responsible for providing a minimum of 150,000 tonnes of cobalt ore to the pilot plant as well as providing access and infrastructure support for construction of the Pilot Plant at Mutoshi. Given the major commercial value of its breakthrough technology, Alexander is investigating financing arrangements that exclude equity dilution.
“Revenue generated from the sale of cobalt produced from the pilot plant shall be used first, to repay Alexander Mining’s capital and operating costs; second, to repay costs incurred by Anvil; and third, any remaining revenue is to be distributed equally between Alexander Mining and Anvil,” said Rosser.
The results from the Pilot Plant will form part of a decision by Anvil on progressing to a feasibility study for the development of a commercial-scale plant at Mutoshi.
Separately, Alexander Mining is currently undertaking AmmLeach test and design work for Tiger Resources on ore from its Kipoi copper/cobalt project which may lead to a decision by Tiger for a pilot plant.
In essence, copper oxide ores, which are found at depths from surface down to typically 70-100 meters, are treated in a process invented in the late 1960s called heap leaching, solvent extraction electro-winning (SX-EW). The now conventional process, which accounts for around 20% of global mined copper supply, uses sulfuric acid-as the leaching reagent. However, for carbonate-hosted oxide ores, which are common in many parts of the world, and especially in the DRC, which has huge quantities of rich copper oxide mineralization, can consume very large quantities of sulfuric acid, making the process potentially expensive. In addition, especially where cobalt is a valuable co-product, like the DRC, the process plant is complicated by expensive clean up circuits to remove unwanted metals. These circuits are effectively eliminated in the AmmLeach process.
The limitations of the current technology are increasingly bumping up against the reality that mining is getting more expensive and difficult, with so many of the easier to mine and process surface deposits already being exploited and a growing move to underground mining. According to Rio Tinto figures, global average ore head grades for copper have fallen to 1.2% from 1.6% in 1990. Meanwhile, the cash cost of copper open pit mining (for 2008) comes in at an average of $0.95 per lb, compared with $1.33 for underground mines.
But according to Rosser, Alexander Mining, reckons it has a cheaper and more environmentally friendly solution for high acid consuming oxide ores using ammonia. “Importantly, all the equipment is basically the same as with the traditional approach, it’s just the pre-treatment process, which is proprietary, and the recycled use of reagent (ammonia), which differs,” said Rosser.
Alexander Mining’s AmmLeach offers compelling economics
Though ammonia is more expensive than sulphuric acid, the fact that a lot less of it is needed per tonne of ore processed adds up to major operating and capital cost savings, says Rosser. For instance, typical high acid consuming ores can require 50-100 kg or more of sulphuric acid for each tonne of ore processed, compared with 3-5 kg of ammonia using AmmLeach. “For high acid consuming copper-cobalt oxide ores in the DRC, the savings would be substantial – around 30% for capital and 40% for operating costs,” says Rosser. As such, mining companies which have previously focused on the lower acid consuming ores now have a highly attractive alternative process. In isolated locations mining companies invariably need to make their own sulphuric acid, which could cost have a capital cost of $80 million-$100 million. For ammonia, it requires a much smaller plant costing maybe $15-20 million.
Also, the sulfuric acid consumed remains entrained in the spent heap which gives rise to potential acid mine drainage problems. By contrast, because the ammonia is recycled, any minor residual ammonia left in the heap acts as a fertilizer to greatly aid re-vegetation.
As well as copper and cobalt, the technology has major potential for treating zinc oxide deposits, which are normally high grade and have proved extremely challenging to treat economically.
A lexander Mining intends to make a return on the technology by licensing it in exchange for a royalty in the region of 2% on the gross revenue of mines where its process is used. The company believes that once AmmLeach is demonstrated processing ore in a new pilot plant in a part of the world such as the DRC with its huge potential, it will see quick adoption as there are many suitable mines across the world.