Evaluation of coal chip size cut by surface miners using digitized measurement and physical validation Techniques – A case study

Abstract

Surface miner technology is a continuous and productive method of cutting coal. Due to its various merits, many surface coal mines are shifting towards this technology for economic extraction and safe operations. The desired size of coal produced by surface miner is one of the important concerns in almost all surface coal mines due to its influence on the price offered by thermal power plants. A field study was conducted in two large surface mines of the Northern Coal Fields (NCL), Madhya Pradesh, India for measurement and evaluation of the entire size distribution of coal chips cut by the surface miner. A proper sampling technique was developed at field scale for obtaining the digitized images of the coal chips cut by the surface miners. The chip size was measured and characterized from the digitized images by use of WipFrag iOS (Version- 3.0) software. Further, a real time methodology to validate the results obtained from digitized image analysis was done by devising a novel field scale sieving technique. The study revealed that over 80 % of the coal cut by the surface miner was of (−)50 mm size, contrary to the assumptions of 100 mm size made by the mine management. Furthermore, the digitized image based measurement yielded excellent validation with the devised sieving methodology. Additionally, to provide credibility and rigor to the findings, a statistical analysis was performed. The results of statistical analysis indicate that that the image analysis slightly underestimates or overestimates the particle size compared to sieve analysis. Nevertheless, despite small discrepancies, the overall variation remains within an acceptable range, demonstrating that image analysis can be a reliable tool at field scale though minor calibration adjustments may be necessary to improve its accuracy and match physical sieving results more closely. © 2025 Elsevier Ltd