Characterization, Pelletization, and Incineration Behaviour of Coal Sludge–Hay Fuel Blends with Emphasis on Emissions

This study investigates the pelletization and incineration behaviour of coal sludge blended with hay as a potential waste-to-energy fuel. The objective was to assess fuel performance, emission characteristics, and environmental implications using blend ratios from 100% hay to 100% coal sludge. The produced pellets were combusted under controlled conditions, and resulting flue gas components were analysed, including CO ₂ , CO, NO ₂ , SO ₂ , HCl, HF, and trace hydrocarbons. The results demonstrate stable incineration across all fuel mixtures. Carbon monoxide concentrations remained within a narrow range, and NOx levels showed minimal variation, indicating that changing fuel composition did not significantly influence oxidation efficiency. Flue-gas moisture decreased with increasing sludge share, consistent with its lower volatile content. In contrast, sulfur- and chlorine-derived emissions showed a strong dependence on sludge content. SO₂ increased from 64 mg·m⁻³ₙ for pure hay to 738 mg·m⁻³ₙ for pure sludge, while HCl rose from 17 mg·m⁻³ₙ to 81 mg·m⁻³ₙ.