New method for cleaning coal could help determine economic viability of coal projects

08 May 2017

A new method for cleaning metallurgical coal to verify coal quality for coke making could replace a widely-used chemical-based process leading to a more accurate assessment of the economic viability of coal projects.

This month, the Canadian Carbonization Research Association (CCRA) and Geoscience BC will launch a research project to assess the effectiveness of an innovative water-based cleaning process for washing exploration samples of B.C. metallurgical coal used in the steel-production process to determine coal and coke quality – key considerations in evaluating the economic feasibility of coal deposits.

“This research will help us identify the best method of determining coal quality before a mine is built,” stated Melanie Mackay, President of the Western Canadian Coal Society and Technical Member of the CCRA. “The ability to accurately evaluate coal quality and the coking characteristics of metallurgical coal during the exploration stage is essential to determining the economic viability of a coal deposit.”

“The potential of finding a faster, safer more reliable method of determining coal quality is a real boon for the coal industry,” added Bruce Madu, Vice President, Minerals and Mining at Geoscience BC. “Ultimately, the more accurate information a prospector or company has about the quality of coal beneath the ground, the higher the value they could get for their property or the end product.”

Coal is B.C.’s largest export commodity. Provincial 2016 estimates peg the value of B.C.’s coal production at $3.32 billion. Coal production currently represents over half of the total mineral production revenues in the province. Between 70-90 per cent of coal produced in B.C. is metallurgical coal.

The research project will compare the water-based Roben Jig coal washing process to the traditional method of analyzing small-scale exploration samples of metallurgical coal, known as the float-and-sink method. This process uses various solvent-based chemicals such as white spirit, methylene bromide, and perchloroethylene (PCE) to remove impurities, namely ash, and produce a clean coal sample suitable for analysis. PCE, a chemical that was commonly-used in the dry cleaning industry, is also a known carcinogen posing potential health risks for laboratory workers.

Coal washing using the Roben Jig process involves loading the coal sample into a specially designed cylinder with water. A motor moves the cylinder up and down in a “jigging” motion which sorts the coal particles by density, with the heaviest particles sinking to the bottom and the lightest particles moving to the top. Clean coal samples are then extracted from the jig and undergo various tests to determine quality, most notably maximum fluidity (melting and interaction/bonding behaviour), and the resultant coke is tested for coke strength after reaction or CSR (an indicator of coke performance in an industrial blast furnace).

If the Roben Jig process provides equivalent or superior results to traditional coal washing methods, it could potentially benefit B.C. and the global coal industry by eliminating the need to use harmful chemicals for treating/cleaning coal prior to coal and coke quality analysis.

CCRA and Geoscience BC will be testing four coal types from B.C. using the Roben Jig and float-and sink methods to evaluate the effectiveness and accuracy of both processes and their relative impacts on coal thermal rheological properties and coke characteristics. Three of these coal samples will come from southeast B.C. coal fields, and the other one from northeast B.C. Testing of the two washing methods will be conducted by Birtley Coal and Minerals Testing, a division of GWIL Industries Inc., in Calgary. Follow-up analysis will be conducted at CanmetENERGY laboratories in Ottawa, where clean coal samples will be carbonized in a small coke oven and resultant coke properties including CSR will be evaluated.

SOURCE : http://www.reuters.com