Dragon aims to strike gold

Materials World magazine
1 Apr 2015

Traditional mining techniques are being challenged by thermal fragmentation. Glynn Garlick looks at how it works. 

Nippon Dragon Resources aims to put the heat on established methods used to extract precious and base metals with its thermal fragmentation process. The Canadian company’s technology uses heat to shatter narrow veins, reducing the need to use explosives to extract high-grade ore deposits.

For most hard rocks, thermal fragmentation uses heat of 800–900°C during the process. But Jean-Yves Therien, the company’s Vice President Business Development, says, ‘You can touch the extracted ore with your hand when it is out. It is not that hot. It is the thermal stress more than the heat that causes the rock to fracture.’

The process involves drilling 15cm pilot holes into the vein. A thermal head, compressed air and water are then inserted to spall the rock and increase the diameter of the hole to 30–110cm.

Ore is extracted in fragments of up to 13mm, while leftover rock between fragmented holes is broken up to recover remaining ore.

The company, based in Brossard, Quebec, says that as less waste rock is extracted during the thermal fragmentation process, far less mining waste is produced. This means fewer chemical products per ounce mined are needed.

There is also less alteration to the terrain during the process, and no wall damage from blast vibrations.

Nippon Dragon Resources says the process can be used in any mine in the world and can give a second life to closed mines that still contain ore. It is currently targeting South Africa and Japan and also aims to win business from the construction industry.

Sowing the seeds of separation

A ‘miracle’ tree could help reduce the need for expensive synthetic materials in mining industry separation processes. Researchers at Sweden’s Uppsala University have shown that Moringa oleifera seeds can be used to separate materials as well as purify water. 

Protein from crushed M. oleifera seeds binds to particles in water and causes them to aggregate. They can then be removed by filtration or settling.The properties of the protein in the seeds were studied by a group from Uppsala University in collaboration with the Polytechnic of Namibia, Windhoek, and the Institut Laue-Langevin in Grenoble, France. Results from neutron reflectometry experiments suggest that Moleifera seeds could also be used to separate materials. Experiments with detergents added to the bound protein showed behaviour changes for different materials. A cationic detergent, widely used as a disinfectant, causes the protein to detach from the surface of alumina.

This discovery allows control of aggregation and offers a way to separate materials.

Call for action on restoring opencast mines  

MPs have called for the Government to deal with unrestored opencast mining sites in the UK.

Issues highlighted in a recent debate in the House of Commons included developers going into administration after extracting coal or having a shortfall of cash put aside for restoration work.

MPs said not all sites required restoration bonds to cover the cost of such work, while some companies had said they could only afford to restore old sites by being given permission for new ones.  

MPs called for the UK Government, devolved governments, local authorities and mining companies to work together to ensure taxpayers were not left footing the bill.

The Government has already responded to a House of Commons BIS Select Committee report issued after an inquiry into the extraction of minerals, oil and gas in the UK and across the world.

To read the debate on unrestored opencast mines, visit bit.ly/1M6GcC0