Brown coal gets greener

AUSTRALIAN scientists have developed a new way to slash greenhouse emissions from brown coal, through the successful trial of a revolutionary process for drying brown coal which can reduce greenhouse emissions from power generation by a third or more.
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The Loy Yang Power Station

Angie Tomlinson

CRC’s (Cooperative Research Centre for Clean Power from Lignite) Mechanical Thermal Expression (MTE) technology removes more than 70% of the water from the brown coals found Victoria and South Australia, resulting in huge greenhouse savings when the dry coal is burnt in a power station.

Brown coal – or lignite – may contain up to two thirds water, producing low energy efficiency, high CO2 emissions and high capital costs in power generation. Offsetting this, reserves are plentiful and estimated to last another 500 years.

MTE dries the coal by a process of mild heating and squeezing, reducing it to a state far more suitable as a feed for efficient power generation.

“Using our technology to dry coal for a new “state of the art” power station, greenhouse gas emissions can be reduced by more than 30 per cent compared to today’s power stations,” says CRC CPL chief executive Peter Jackson.

“Even bigger reductions - over 40% - will be achieved if the dry coal is fed to the next generation of integrated coal gasification combined cycle (IGCC) plants.”

Drying brown coal in this way has the potential to far exceed the greenhouse gas savings from the Federal Government’s Mandated Renewable Energy Target Scheme (MRET), saving 9 million tonnes of CO2 a year if applied to remove half of the lignite water in existing power stations, against the MRET target of 6.5 million tonnes, he said.

CRC researchers are now working on a design for a continuous-feed pilot plant capable of drying 15 tonnes of coal per hour, as a test-bed for industrial application of the technology and as a forerunner to a commercial scale demonstration plant.

The research has also identified potential uses for the large amounts of water removed from the coal by the MTE process. The MTE product water could readily replace some of the lower quality water requirements in a power station - such as cooling water make-up and ash pond water - thus reducing the consumption of fresh water.

The CRC plans to extend trials to include overseas lignites and low-rank coals, with a view to developing export markets for its patented MTE technology.