Most Indonesian coals are either Sub-bituminous (A, B or C) or High Volatile Bituminous (Bor C). In contrast the majority of Australian coals are High Volatile Bituminous A with lesser numbers at higher and lower ranks than this. Regarding Carbon content (daf), the Indonesian coals range from about 72 to 82%, whereas the Australian coals range from about 78 to 89%.
Figure 1: Ranks of Arutmin, KPC, other Indonesian and Australian Coals
Chemical and Physical Properties Related to Coal Rank
Apart from carbon content, many coal properties follow trends with rank. Figures 2 to 16 show variations in Moisture content, Volatile Matter, Ash content, Calorific Value, Hydrogen, Nitrogen, Sulphur, HGI, Ash Composition and Ash Fusion Temperature with rank for Indonesian coals (with Arutmin and KPC coals identified) and Australian coals. Notable observations include:
Moisture (Figures 2 and 3): There is a sharp increase in Moisture (arb4 or adb5) as the Carbon content decreases from 80 70 70%.
Volatile Matter Content (% daf, Figure 4): Decreases sharply for higher rank coals in the carbon range 80-90%. Reasonably constant at around 50% for Carbon in the range 70-80%.
Ash Content (% db, Figures 5): A slight trend for increasing Ash with Carbon in the range 70-80%.
Calorific Value (Figures 6 and 7): A sharp increase in CV (daf or arb) in the Carbon range 70-80%. Continuing increase in the Carbon range 80-90%.
Hydrogen Content (% daf, Figure 8): Generally reaches a maximum at Carbon about 79%,
with considerable scatter.
Nitrogen Content (% daf, Figure 9): Rough trend for nitrogen to increase with Carbon.
Sulphur Content (% daf, Figure 10): Not much of a trend. The range of Sulphur is wider for Indonesian coals than for Australian.
3 Data sources: KPC and Arutmin coal data was provided by the Bumi Group. Other
Indonesian and Australian coal data came from the Barlow Jonker database.
4 Total Moisture is strictly not a property since it can vary as a result of weather conditions and coal preparation processes. The values used here are considered typical.
5 Air-dried Moisture is not a property to the extent that the laboratory conditions of temperature and humidity are not rigidly controlled. Nevertheless it is a useful indicator of the inherent attraction of moisture to a coal. The sometimes used term inherent moisture is not completely justified.
HGI (Figure 11): Pronounced trend for HGI to increase for Carbon in the range 80-90%. For lower Carbon the HGI is generally low with some exceptions.
SiO2 in Ash (Figure 12): There is a general increase for Carbon in the range 70-80%. Above that, the SiO2 is very wide ranging.
Fe2O3, CaO and Na2O in Ash (Figures 13, 14 and 15): Generally higher for lower rank coals in the Carbon range 70-80%.
Ash Fusion Temperature (Figure 16): The Initial Deformation Temperature is generally lower for lower rank coals in the Carbon range 70-80%.
Figure 2: Total Moisture of Indonesian and Australian Coals
Figure 3: Moisture (adb) of Indonesian and Australian Coals
Figure 4: Volatile Matter Content (% daf) of Indonesian and Australian Coals
Figure 5: Ash Content (% db) of Indonesian and Australian Coals
Figure 6: Calorific Value (daf) of Indonesian and Australian Coals
Figure 7: Calorific Value (arb) of Indonesian and Australian Coals
Figure 8: Hydrogen Content (daf) of Indonesian and Australian Coals
Figure 9: Nitrogen Content (daf) of Indonesian and Australian Coals
Figure 10: Sulphur Content (daf) of Indonesian and Australian Coals
Figure 11: HGI of Indonesian and Australian Coals
Figure 12: SiO2 in Ash of Indonesian and Australian Coals
Figure 13: Fe2O3 in Ash of Indonesian and Australian Coals
Figure 14: CaO in Ash of Indonesian and Australian Coals
Figure 15: Na2O in Ash of Indonesian and Australian Coals
Figure 16: Ash Initial Deformation Temperature of Indonesian and Australian Coals
Summary: The above observations demonstrate that Indonesian coals typically differ in
many ways from Australian coals. Many of the noted trends can be related to differences in rank and are also observed over a much wider range of coals than just Indonesian and Australian. A summary of typical differences in given in Table 2.
Table 2: Typical differences between Indonesian and Australian coals based on
Standard Laboratory Analysis
