Combustion characteristics of low-quality lignite for different bed material sphericities in a circulating fluidized bed boiler: A numerical study

Abstract

This study delves into the combustion behavior of various lignite types within a circulating fluidized bed boiler (CFBB), with a primary focus on the impact of different bed material sphericity ratios (0.5, 0.7, and 0.9). Utilizing bed material with a sphericity ratio of 0.9 sourced from the Çan power plant and verified through experimentation, the research reveals several key findings. Notably, furnace temperatures tended to rise with higher sphericity ratios, albeit with variations between lignite types, particularly highlighting the complexity of this relationship in the case of GLI-Tunçbilek lignite. Pressure levels in the combustion chamber remained consistent across different sphericity ratios, indicating minimal influence on pressure dynamics. Improved combustion efficiency, especially at the bottom of the boiler, was observed at lower sphericity levels (0.5 and 0.7) for Çan lignite, as reflected in CO2 mole fractions. While NOx emissions generally decreased with lower sphericity, the sensitivity to sphericity varied by lignite type, with Ilgın lignite showcasing low NOx but high SO2 emissions, underscoring the intricate interplay between lignite properties, sphericity, and emissions. Overall, this study advances our understanding of CFBB combustion dynamics, offering insights valuable for optimizing performance and emissions control, particularly in lignite-based power.