Coldry Process


Coldry Process

Coldry Process is a coal upgrading technology developed in Victoria, Australia by Environmental Clean Technologies Limited[1] to specifically beneficiate low-rank brown coal (lignite) and sub-bituminous coal by removing natural high moisture content and certain pollutants; harden and densify the coal; raise the calorific value of the coal to more than 5800 kcal/kg; and transform the coal into a stable, exportable black coal equivalent product for use by black coal fired power generators to produce electricity. The Coldry Process is a commercial method to achieve large scale beneficiation of low-rank coal without a need for government subsidy.

Contents

Origin

The Coldry Process evolved from theoretical and test work in the Department of Organic Chemistry, University of Melbourne, Victoria, in collaboration with CRA Advanced Technical Development, Melbourne in 1989.[2] This work was based on earlier theoretical work around Densified coal undertaken by the Department of Organic Chemistry, University of Melbourne in 1980-81. The possibility of creating densified coal was identified following observations made at the Maddingley Mine near Bacchus Marsh, Victoria. The mine operator observed that hardened bitumen-like road surfaces formed naturally soon after rain events when trucks had churned up brown coal fines with moisture when they entered and left the mine. In the days that followed a rain event the road surfaces at the mine would harden like tarmac and no longer absorb water. Dr Johns and colleagues identified that a process of low-mechanical shear had occurred where brown coal mixed with a small amount of moisture and subject to low-level mechanical shear had triggered a natural exothermic reaction process within the coal leading to the expulsion of its moisture content.[3] The low mechanical shear process fundamentally alters micro chemical bonds within the coal, naturally reducing moisture content to around 11 per cent; boosting calorific value over 5600 kcal/kg; and creating a new ‘densified coal’ product that is hydrophobic, no longer prone to spontaneous combustion, readily transportable and from a commercial and environmental point of view, a black coal equivalent.

History

For some years the Maddingley Mine provided brown coal to an adjacent manufacturing plant located to the south of Bacchus Marsh. The plant and the mine were decommissioned in the late 1980s. In 1990 the Calleja Group transport company acquired the mine and the business park and became aware of the possibility of densified coal. The company acquired Intellectual Property rights for the densified coal process around 1994. Under the leadership of David Calleja and David Wilson the company invested in the process of developing and commercialising the densified coal methodology and succeeded with bench tests by 1997. At this time the technology process became known as the Coldry Process. For some time the company sought without success to include the Coldry Process as a technology worthy of review, investment and development by the government funded Cooperative Research Centre for Lignite program. Subsequently the Calleja Group invested in the establishment in February 2004 of a large scale working 16,000 tonne per annum pilot plant to demonstrate the process. By April 2004 the Coldry plant rapidly established itself as a viable commercial method to dewater brown coal without need for government subsidy or producing hazardous byproducts. The operation of the pilot plant was assigned to Asia Pacific Coal & Steel Pty Ltd (APCS) in June 2004 when APCS was given responsibility to commercialise the technology. In March 2005 APCS was acquired by ASX listed company Environmental Clean Technologies Limited, which took responsibility for commercialising the Coldry Process. An expanded pilot plant has since been established at the Bacchus Marsh site and testing of more than 300 coal types from around the world has been achieved. Additional improvements include a water recovery process funded by the Victorian government in 2007. Since 2009 ECT Limited has focused on attracting investment partners and investment to fund the establishment of a 2 million tonne per annum Coldry production plant in the Latrobe Valley.

Densified brown coal

The Coldry Process produces Densified coal using raw brown coal with an as-mined water content as the sole material. Only the water originally present in the coal is removed by the drying process. This is a distinct advantage over all other known current and planned procedures aimed at producing a dewatered product. Recovered clean, distilled water is the only by-product of the Coldry Process. The Coldry Process attritions brown coal in large energy efficient kneaders to produce a coal paste easily extruded to a uniform pellet size. The resulting pellet is dried by evaporative water loss at ambient temperatures to produce a densified brown coal. Water loss is fully recovered and captured as a demineralised (distilled) water. The compressive strength of the densified coal generally equals that of briquettes or hard coals. As a consequence of water loss, densified brown coal has a calorific value equivalent to that of high rank black coal, establishing Coldry Process pellets as a Black Coal Equivalent. The densified brown coal product emanating from the Coldry Process possesses abrasion resistance and is stable and safe to transport as an export product. The low mineral content characteristic of densified BCE derived from Victorian brown coal gives a distinct advantage over black coals, which by comparison contain higher levels of ash and sulphur. The percentage of Volatile and Fixed Carbon values of raw coal is retained by the Coldry Process, ensuring the chemical reactivity characteristic of raw brown coal is substantially retained in the densified product. Retention of valuable volatile fractions makes densified Coldry BCE an ideal feed for gasification processes.

Characteristics of Coldry densified coal

The chemical and calorific values of densified coal derived via the Coldry Process from typical Victorian brown coal with a natural average moisture content of 60 per cent by weight compares well with typical high grade black coal exported from Tarong Queensland, and Newcastle New South Wales Australia.

Chemical composition

Name C Carbon % H Hydrogen  % N Nitrogen % O Oxygen % S Sulfur %
Victorian Brown Coal (Lignite) 26.6 1.93 0.21 9.4 0.39
Densified Brown Coal (Coldry ) 59 4.24 0.46 21 0.85
QLD Black Coal (Export) 52 2.59 0.74 11 0.25
NSW Black Coal (Export) 48.9 3.29 1.19 10.1 0.81

Comparison of calorific values

Name Moisture % Volatiles % Fixed Carbon % Ash % Sulfur % Net Weight Specific Energy
Morwell Brown Coal (Lignite) 59.3% wb 20.0% wb 19.86% wb 0.9% wb 0.3% db 2006 kcal/kg ar

8.4 Mj/kg ar

Tarong Black Coal (Export coal) 15.5% adb 22.5% wb 44.1% wb 17.9% wb 0.42% wb 4800 kcal/kg adb

20.1 Mj/kg adb

Densified Brown Coal (Coldry) 12.0% adb 48.9% wb 49.1% wb 2.4% wb 0.3% wb 5874 kcal/kg adb

24.6 Mj/kg adb

Percent by weight

adb = as dry basis. ar = as received. db = dry basis. wb = wet basis.

See also

References

  1. ^ ECT Limited website
  2. ^ The Conversion of Brown Coal to a Dense, Dry, Hard Material. B.A. Johns, A.L Chaffee and K.F. Harvey Dept of Organic Chemistry, University of Melbourne, Victoria, in collaboration with A.S. Buchanan and G.A. Thiele at CRA Advanced Technical Development, Melbourne., 1989
  3. ^ Johns, R.B., Chaffee, A.L., and Verheyen, T.V. International Conference Coal Science, Dusseldorf 1981

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