Densified coal
Densified coal is the product of the Coldry Process coal upgrading technology that removes moisture from low-rank coals such as sub-bituminous and lignite/brown coal. The densification process raises the calorific value of low-rank coal to equal or exceed that of many export-grade black coals. Densified coal resulting from the Coldry Process is regarded as a black coal equivalent or replacement for black coal.[1]
Overview
Densified coal as an ostensibly ‘new’ product emanating from brown coal was first identified by Dr R.B. Johns and colleagues at the Organic Chemistry laboratory at Melbourne University following observations made at the Maddingley Mine near Bacchus Marsh, Victoria, Australia. The mine operator identified that hardened bitumen-like road surfaces formed naturally and spontaneously after heavy trucks churned up brown coal fines with moisture from rainfall when the trucks 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 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.[2] The process fundamentally alters the 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, and readily transportable.
Characteristics of densified coal
The chemical and calorific values of densified coal derived 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
- Bituminous coal
- Bergius process
- Coal assay
- Coldry Process
- Energy value of coal
- Orders of magnitude (specific energy density)
- Fischer-Tropsch process
- Karrick process
- Leonardite
- Maddingley Mine
- List of CO2 emitted per million Joule of energy from various fuels