Maceral analysis categorizes the microscopic constituents of coal according to morphology and reflectance. It is then used to determine the proportion of reactive to inert macerals for prediction of various coal quality parameters. In our laboratories, maceral nomenclature follows the definitions of the International Committee for Coal & Organic Petrology, which are recognized by ASTM, ISO, and the Australian Standards Institute.
Automated Group-Maceral Partitioning
In addition to the carefully measured manual maceral count, we are able to provide automated group-maceral partitioning from Fingerprint data. A probability plot overlay of our Fingerprint (the Reflectance Profile), provides a very quick visual appraisal of the Vitrinite and Inertinite contents of a coal. The location of the inflection point of the curve separates these two group-maceral populations, and the percentages of each can be read from the ordinate on the right of the graph, uniquely validating a manual maceral count.
Petrography is used by coal-producers to evaluate the nature of coal deposits, to confirm the quality of vessel or train cargoes, and to show the uniqueness of a specific product relative to another. Steel producers use petrography as an aid in the design of coking coal blends, to help in trouble-shooting problem-cokes, and to confirm the nature of vessel or train cargoes. Steam coals can benefit from an evaluation of the Liptinite content, because Resins and Liptinites have elevated volatile contents, and strongly impact on a coal’s reactivity, and ignition stability.
Point-Counting Fluorescent Macerals
We have modified a Ploemopak-equipped Leitz Orthoplan microscope to enable single-keystroke switching between fluorescence and white light modes. This greatly simplifies and makes commercially viable the point-counting of fluorescing macerals.
Automated Fluorescence Microscope System
The Detrovitrinite component of several Queensland coals possesses a brown fluoresence in blue light. A correlation between these fluorescing components and the rheology of the coals has recently (2010) been determined.
Non-fluorescing Telocollinite adjacent to brown fluorescing, and Sporinite-bearing Detrovitrinite. Blue light excitation (BG12), emission filter K510, German Creek Formation, Queensland
This technique is equally important for the correct evaluation of steam coals. For example, Kaltim Prima steam coal from East Kalimantan, Indonesia, contains abundant fluorescing Liptinites that are mainly responsible for its’ superior combustion characteristics.
Highly-Reflecting Binder used in the Study of Liptinites
In lower rank coals, pellet binder and Liptinite often have the same reflectance, and cannot be discriminated. In the case of Low- or Liptinite-free coals, the problem can be ignored, and the lower reflectance boundary of Vitrinite in Fingerprints is located and marked by Thresholding. However, in those situations where it is necessary to quantify the reflectance and true volume of Liptinites in either Steam- or Coking-coals, we have found it beneficial to use a highly reflecting binder when making pellets. In the example below, the coal was embedded with white latex paint as binder, and although a reflectance halo occurs in Vitrinite at the boundary of the grain, the Liptinites, which are artificially enhanced with green in the image, are easily distinguished from binder and are unambiguously displayed in the Fingerprint. Again, the volume of Liptinite can by determined from the cumulative probability plot overlay of the Fingerprint, by the location of the First Inflection point.
