Experimental and numerical investigation of co-firing lignite coal with upgraded coal and bituminous coal in a drop tube furnace

This study investigates the co-firing of pulverized lignite coal with upgraded lignite coal and bituminous coal (Vitol) in a drop tube furnace with detailed CFD simulations. The research examines the impact of different coal blends on unburned carbon and NOx emissions under various co-firing ratios. Experimental results demonstrate that co-firing lignite coal (BRC) with upgraded BRC coal (BHC) leads to lower unburned carbon and NOx emissions compared to co-firing with Vitol. Specifically, increasing the proportion of BHC in the blend reduces unburned carbon but increases NOx, while increasing the proportion of Vitol elevates both unburned carbon and NOx. This trend is attributed to the higher nitrogen content of Vitol (4.43%) compared to BHC (1.13%). The CFD simulations provide detailed insights into the temperature distribution and NOx formation mechanisms under different blending conditions. The temperature distribution analysis reveals that co-firing broadens the combustion zones compared to single coal combustion due to variations in devolatilization and ignition times among the different coal types. The study underscores the importance of selecting compatible coal blends to optimize combustion efficiency and minimize emissions in coal-fired power plants