Physico-chemical characterization of coal combustion by-products derived from thermoelectric power plants

The widespread use of coal as a primary source of commercial energy in India resulting in substantial waste production from power plants, including fly ash and bottom ash. Inappropriate disposal of these waste by-products poses a range of environmental challenges and hence requires proper attention. The current work examines the physico-chemical nature of coal and ash characteristics of the power plant in Rupnagar, India. A combined approach using X-ray diffraction (XRD), Field Emission Scanning Electron Microscopy, Fourier Transform Infrared (FTIR), Energy Dispersive X-ray, and Inductively Coupled Plasma Mass Spectrometry (ICP-MS) was used to characterize the samples. As a result, the total moisture content of the feed coal exhibited a range of 7.09–9.75%, while the fly ash and bottom ash varied from 4.19–6.28% and 2.16–5.12%, respectively. The air-dried ash and air-dried moisture content in coal varied between 5.95–6.39% and 39.5–44.81%. The volatile matter in the feed coal samples showed variability within the range of 19.71–21.34%. The coal’s gross calorific value was measured in the range of 14.23–15.87 MJ kg⁻¹ having carbon and sulfur content of 39–43% and 0.35–0.48%, respectively. Further, XRD analysis showed quartz, mullite, kaolinite, and hematite in feed coal, fly ash, and bottom ash. Morphologically, fly ash was characterized by fine spherical particles compared to bottom ash, which were observed as large carbon particles with a high abundance of Si and Al in chemical composition. Furthermore, the fly ash samples exhibited higher concentrations of various heavy metals, particularly Zn (80.67 mg kg⁻¹), Cu (25.66 mg kg⁻¹), and Pb (16.7 mg kg⁻¹) compared to bottom ash and the feed coal. FTIR analysis showed the Al–O and Si–O due to the large kaolinite and quartz particles. By examining coal, fly ash, and bottom ash, this research aims to provide important insights into coal combustion products and reduce the environmental impact of waste generation from power plants.

Graphical abstract