Coal preparation essential for the economic and environmental viability of coal

14 November 2008

Froth flotation test in progress, CRL Energy’s coal preparation laboratory. Photo: Trevor Dine.

An upturn in the coal industry, and the recognition of the value of coal preparation, has seen CRL Energy’s Gracefield coal preparation laboratory busier then ever. In the past financial year the laboratory has expanded, including increasing the float/sink area to process larger samples. In addition, CRL Energy has invested in staff training and new equipment. New equipment includes a Denver Cell to provide froth flotation testing that meets Australian Standards. To help with the cell’s commissioning an Australian consultant was engaged to train several staff in the idiosyncrasies of froth flotation. Trevor Dine, manager of the Analytical and Environmental Business Group at CRL Energy, says basic coal preparation is the removal of impurities from run-of-mine (ROM) coal by using a series of separation processes in a washery or preparation plant.

“The type of testing we do here in the laboratory is crucial for coal producers for determining what needs to happen in their coal preparation plants (CPP). When coal is prepared in a plant they want to remove all the extraneous non-combustible material - particularly if the coal is fuel for thermal power generation, where cleaning it up at the plant reduces ash handling and sulphur, carbon and NOx emissions. Coal producers also benefit from reduced transport costs etc. per unit of heat and they provide a consistent, uniform product to their clients. Really coal preparation is essential for the economic and environmental viability of coal, especially for thermal power generation where coal users need optimum calorific value, consistent grindability, minimal moisture and ash variability,” says Mr Dine.

Testing in the CRL Energy coal preparation laboratory involves a number of steps:

1. The ROM coal sample is crushed to the desired topsize. At the CPP, crushing reduces the size of the coal pieces so that it can be more easily handled and processed. Crushing requirements are an important part of CPP design.
   
2. The coal is subject to a ‘drop shatter’ test. In the laboratory this simulates the coal breaking as it moves around the plant.
   
3. Size analysis of the coal pieces is carried out.
   
4. The sample is then subject to a ‘float/sink’ test, where different density liquids are used to separate the minerals and other contaminants from the coal.
   
5. Finally the sample is tested using ‘froth flotation’. The newly acquired Denver Cell is the industry standard for froth flotation. This gives a semi-quantitative indication of the results that may be achieved in a washery.
   

For more information about services at CRL Energy’s Coal Preparation Laboratory contact Trevor Dine or Grant Murray, Laboratory Supervisor - Solid Fuels.