Improved Efficiency of Coal Burning in KWr-0.2 Low-Capacity Boilers by Redesigning the Air Supply

This study presents the results of research aimed at improving the efficiency of coal combustion in KWr-0.2 boilers. The improvement is achieved by optimizing the air supply to the stationary coal bed using vertically installed cylindrical air injectors equipped with side openings. The objective of the research is to increase the efficiency of low-power boilers by (1) enhancing the air supply to the coal bed, and (2) optimizing the number and arrangement of heat exchange pipelines within the combustion chamber. The research methodology included: numerical calculation of velocity and temperature fields above the fuel bed in the combustion chamber under specified post-combustion firing conditions; experimental analysis of the flue gas composition using a TESTO-300 gas analyzer; evaluation of residual energy content in coal and ash (obtained from both the collimator and integrated combustion systems) using a calorimetric bomb; and assessment of the elemental composition of ash structures via energy-dispersive X-ray spectroscopy. The results of the study demonstrated a 35% reduction in flue gas toxicity. Furthermore, the residual energy content in the ash resulting from the proposed method was found to be 40% lower than that observed with the conventional combustion method. The total content of chemical elements in the fuel combustion products decreased by 11–12%. The practical significance of the proposed coal combustion method is substantiated by its high economic efficiency, which enables a reduction in the required mass of coal burned by up to 40% per heating season.