PHYSICO-CHEMICAL AND STRUCTURAL ANALYSIS OF COAL ASH FOR IMPROVED COMBUSTION EFFICIENCY
Abstract
ABSTRACT
The growing demand for efficient and sustainable energy production has intensified the need to optimise coal combustion processes, particularly in regions where coal remains a dominant energy source. This study examines the physico-chemical and structural properties of coal ash derived from three sub-bituminous coal samples sourced from Onyeama, Okpara, and Ogbete mines in Enugu State, Nigeria. By employing a combination of analytical techniques, including Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy with Energy-Dispersive X-ray Spectroscopy (SEM-EDS), Thermogravimetric Analysis (TGA), X-ray Fluorescence (XRF), and Ash Fusion Temperature (AFT) analysis, the coal ash samples were comprehensively characterised. The results revealed that the ashes predominantly comprised silicate and aluminosilicate compounds, which influenced their thermal stability and combustion behaviour. SEM-EDX analysis highlighted morphological variations among the samples, correlating with combustion completeness and mineral residue. TGA findings indicated differing devolatilisation patterns and thermal stabilities, with Coal Ash II exhibiting the highest residual ash content of 15%. XRF results confirmed high concentrations of SiO₂ and Al₂O₃, with Coal ash II showing the highest levels at 52.078% and 28.656% respectively. The slagging indices initially suggested low fouling tendencies due to the high iron-calcium ratio, which is greater than 3, as well as the slagging viscosity indices, which exceed 72. However, the silica-to-alumina ratio ranged from 0.31 to 3, indicating that fouling tendencies were indeed high. AFT measurements revealed significant differences in thermal deformation points, underscoring the impact of compositional variance on the risk of slagging, with Coal ash III exhibiting the highest flow temperature of 1550°C. The study concludes that understanding the mineral and structural characteristics of coal ash is crucial for enhancing combustion efficiency and minimising operational challenges in coal-fired systems.
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