Coal quality related to microfractures identified by CT image analysis

Abstract Identification of microfractures developed in coal are indispensable to coal quality assessment and helpful to understanding the tectonic history. X-ray computed tomography (CT) scanning has promised to be one of the most powerful non-destructive testing methods for these factors. In this work, we aimed to develop methods for identifying microfractures from CT images, and to identify the relationship between these properties and coal quality. Lati Coal Mine in East Kalimantan, Indonesia, was selected as a case study area, and fifteen samples were taken from three seams. We developed a successful process of setting the samples in water to avoid cupping artifacts in the CT images, and applied image processing to characterize fractures in detail. Ash content increased in proportion to the total length of microfractures. Correlations of CT-values with coal quality such as the ash (%) and caloric content (cal/g) suggest that coal quality is inversely proportional to the CT-values. Positive correlation was found between ash and the total number of microfracture widths, which is interpreted to mean that the coal contained mineral impurities (a source of ash) in proportion to the development of microfractures. Because local structures control microfracture occurrence, and microfracture development controls coal quality by allowing the infilling of mineral impurities, local structures influence coal quality.

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