Coal Preparation » General
In 2015 project C23054 investigated and reviewed the Australian Standard for dust extinction moisture (DEM) of coal AS4156.6 and re‐enforced the validity and applicability of the test method described. However, the project outcomes also highlighted a number of possible areas where the accuracy of the test is compromised. Most notable, was the preparation method in obtaining and testing the coal samples.
This project investigated different sample preparation methods, from which a procedure, which results in reduced error and greatest level of repeatability was specified. A total of six coal samples, obtained in the full size (F/S) fraction, three from NSW and three from Qld were studied. Comprehensive testing was conducted on two coal samples, Coal A and Coal C. Following specification of a revised test method, verification tests were conducted on the remaining four coal types, Coal B, D, E and F. Additionally, characterisation tests including particle size distribution (PSD) and density, mercury intrusion porosimetry (MIP) and moisture analysis (free drained saturation) were also conducted for all coals.
The influence of air drying duration of the full size (F/S) coal samples was investigated prior to screening to the ‐6.3mm size fraction test samples. Air drying durations of 1, 3 4 and 5 days were investigated. Testing was also conducted on the as received samples with no air drying. Two moisture content reduction (drying) schemes of the test samples, in a controlled laboratory environment and in the oven at a temperature of 40°C were investigated. The method outlined in AS4156.6 stipulates that samples for moisture are scooped out (decanted) of the main test sample for moisture determination. This involved modifying the existing method to representatively sample the coal using a rotary sampler device (RSD). This resulted in increasing the size of the sample for moisture determination.
The existing test method was also extended to assess the inhalable, thoracic and respiratory (PM10, PM2.5 and PM1) particulate matter fraction levels of the coal samples tested. While this project shows that a parallel dustiness classification in terms of health‐related dust fractions similar to that outlined in the European Standard for dustiness classification EN15051‐2 is possible, additional, more comprehensive modification of the AS4156.6 test apparatus and a thorough testing programme of Australian coals is required for such a classification to be incorporated in the existing standard.