Optimizing the use of Indigenous high ash bituminous coal for sustainable pulverized coal injection and efficient energy transfer

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Abstract
The beneficiation of indigenous high ash bituminous coal is crucial for optimizing its suitability for Pulverized Coal Injection (PCI) in the steel industry. This study investigates the impact of size and density-based beneficiation on key coal properties, including proximate and ultimate analysis, calorific value, organic petrography, swelling index and thermal analysis. The raw coal, with an initial ash content of 28.73%, volatile matter of 19.43%, and fixed carbon of 51%, goes through density separation into fractions ranging from 1.3 to 1.8 kg/m3. The < 1.44 kg/m3 fraction shows a significant reduction in ash content average 16.23% in all sizes with total recovery of 32.58%, which attracted investigations to assess its utilisation potential as PCI coal after blending it with very low ash imported non-coking coal. Furthermore, beneficiated coal with a density of < 1.44 kg/m3 reveals an optimal volatile matter content of 21.62% and fixed carbon above 61.46%, aligning with PCI specifications. Our study also magnifies the importance of maceral composition and vitrinite reflectance (Ro%), with low-density fractions (< 1.44 kg/m3) containing 62.4–77.8% vitrinite, enhancing combustion efficiency. Ultimate analysis endorses that the < 1.44 kg/m3 density fraction, with an average carbon content of 73.46% and minimal sulphur < 0.42%, ensures efficient energy transfer. Gross Calorific Value (GCV) unveils that this fraction consistently provides energy outputs between 6642 and 8355 kcal/kg, making it the most suitable for PCI applications. Thermal analysis (DSC-TGA-DTG) of the beneficiated coal samples revealed combustion profiles closely aligned with imported PCI coal, confirming their compatibility with significant recovery yield (32.58%), and the successful blending strategy that brings the final ash content to within PCI specifications (9.59%). The potential for synergistic effects in blended combustion further reinforces their suitability for efficient PCI application. This study accentuates the strategic advantage of beneficiation in reducing dependency on imported PCI coal, enhancing domestic resource utilization, and promoting cost-effective steel production.

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