Coal upgrading technology refers to a class of technologies developed to remove moisture and certain pollutants from low rank coals such as sub-Bituminous coal and lignite (brown coal) and raise their calorific values. Companies located in Australia, Germany and the United States are the principal drivers of the research, development and commercialisation of these technologies.
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Environmental rationale
Around 30 nations collectively operate more than 1,400 brown coal-fired power stations around the world. Brown coal power stations that cannot economically dewater brown coal are inefficient and cause of high levels of carbon emissions. High emitting power stations, notably the Hazelwood power station in Australia, attract environmental criticism. Many modern economies including Greece and Victoria (Australia) are highly dependent on brown coal for electricity. Improved environmental performance and the need for stable economic environment provide incentive for investment to substantially reduce the negative environmental impact of burning raw ('as mined') brown coal.
Economic rationale
Coal upgrading technologies remove moisture from 'as mined' brown coal and transform the calorific performance of brown coal to a 'cleaner' burning status relatively equivalent to high calorific value black coal. Some coal upgrading processes result in a densified coal product that is considered to be a Black coal equivalent product suitable for burning in black coal boilers.
Victorian brown coal with a characteristic moisture content of 60% by weight is regarded as the 'wettest' brown coal in the world. The high moisture content is the key reason why the state's three major power stations are collectively regarded as the dirtiest carbon emitters in the world. Studies undertaken by the University of Melbourne and Monash University confirm that when moisture is removed from Victorian brown coal, naturally low levels of ash, sulfur and other elements rank it as being one of the cleanest coals in the world. When dewatered upgraded brown coal can compete in the export market at comparable prices to black coal.
With significant levels of brown coal mining occurring around the world, and mining levels increasing, the need for coal upgrading technologies has become more apparent. the technologies will help to address global environmental concern of rising emissions from the burning of brown coal and provide alternative fuel options to rapidly emerging economies such as Vietnam that face difficulty competing for black coal with China, India, Japan and other nations.
Technology comparison
Because of inherent high moisture content, all lignites need to be dried prior to combustion. Depending on the technology type drying is achieved either via a discrete operation or part of a process. The comparison chart identifies different technology drying methods that are in development in different countries and provides a qualitative comparison.