Low-Rank Coal Drying: Can it Bridge the Gap?

By Environmental Clean Technologies (ECT)

Environmental Clean Technologies is in the process of commercialising its low rank coal drying process: Coldry.

In the following article they explain the Fundamentals underpinning brown coal densification and how the Coldry process aims to deliver the first large-scale demonstration project in Victoria, Australia. They also touch on their brown coal-based iron making technology: MATMOR.


World Coal magazine ran an article by Nigel S. Dong of the UK IEA Clean Coal Centre in its December 2011 issue titled ‘Soaking it up’, which highlighted the drivers behind low rank coal drying and the technical and economic challenges facing successful development.

Our own Coldry process is mentioned in the December article and World Coal will feature a more in depth article on Coldry, titled ‘Drying Out’, in their April issue.

In that article we identify some of the key drivers behind the quest to dry low rank coal, including:

• Coal has made up almost half the increase in energy use over the last decade. The global demand for coal is forecast to increase by more than 1 billion tpa by 2035, despite concern over its role in global warming.

• Demand pressure, driven primarily by the growth in electricity demand in emerging nations, is consequently driving up the price of thermal coal. This makes lower rank coals increasingly attractive, both in terms of price and as an energy security option for existing and new power plants.

Our Coldry process is an ideal solution technically for drying low rank coal. It’s also cost-effective as well, thanks to its clever use of ‘free’ low-grade waste energy from the co-located power station, which is a significant point of difference to technologies that rely on high-grade energy.


Coldry is an evaporative drying process based on ‘brown coal densification’.

Essentially, brown coal is sheared and attritioned, reducing the mean particle size and releasing water naturally held in the porous coal microstructure forming a plastic mass. This dispersal of surface and physically trapped moisture lends itself to evaporative removal at or near ambient temperatures. However the extra benefit to drying, using brown coal densification, lies in its liberation of some of the chemically bound moisture without the need for high temperature or high pressure.

As the pellets densify the newly formed structure shrinks, resulting in a significantly more compact microstructure compared to the original coal. This new structure significantly reduces the propensity to self-heat to that of a typical bituminous coal.


When applied to suitable low rank coals, the mechanically simple Coldry process produces a feedstock in the form of densified pellets that are of similar calorific value to many bituminous coals, whilst significantly reducing CO2 intensity when generating electricity compared to its original brown coal form.

Now extrapolate that potential to emerging nations that are increasingly turning to low rank coal just to get and keep the lights on, and it’s easy to see the positive mitigation that drying technologies like Coldry can have globally compared to doing nothing.

For more information on ECT's Coldry process, go to the next page of this e-newsletter.