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. However, the distinction between the Vitrinite submacerals, Telovitrinite and Detrovitrinite, is unreliable, and although required in Australian analyses, the subdivision is not made in North American laboratories, nor incidentally, in the ICCP’s own Accreditation exercise. In any case, we have shown that the quality of coking and steam coals is more dependant on the fluorescence of the vitrinite component rather than the proportions of the two vitrinite sub-types, (see “Coal Quality from Automated Fluorescence Imaging Microscopy” below).
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.
Vitrinite Fluorescence-Typing & Quantifying Fluorescent Macerals
A Zeiss Universal robotic platform including autofocus, scanning stage, excitation and emission filter wheels and digital sensor is used to perform Fluorescence Imaging for digital analysis. This new technique includes Vitrinite Fluorescence Intensity analysis, called Fluorescence-Typing, (of both steam- and coking-coals), and image analysis to quantify the amount of liptinites in both coking- and low-rank steam coals. Our new technique is documented in Coal Quality from Automated Fluorescence Imaging Microscopy
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.
