Cocombustion Characteristics of Blended Coal/Ammonia: Experiments and Atomistic-Labeling-Based Molecular Dynamics Simulations

In China, coal-fired power generation remains the primary source of CO2 emissions. Partially substituting coal with ammonia (NH3) as a fuel has been recognized as a feasible strategy for reducing the emissions of CO2 from power generation. Most existing studies mainly focus on the ammonia cocombustion behavior of single coal, relatively little attention has been paid to the ammonia cocombustion behavior of blended coals. However, due to rising coal prices and uneven coal resource distribution in China, coal blending has been widely adopted in Chinese thermal power generation, investigating the behavior of blended-coal/ammonia cocombustion is of greater practical significance. Therefore, this study investigates the kinetic synergistic mechanism of blended-coal/ammonia cocombustion through isothermal thermogravimetric experiments and atomistic-labeling-based molecular dynamics simulations. The results indicate that ammonia exerts a stronger inhibitory effect on the combustion rate of bituminous coal than on lignite. Furthermore, ammonia cocombustion with lignite produces a larger amount of OH radicals, which further enhance the combustion of ammonia than in bituminous coal/ammonia systems. However, the synergistic interactions between coal and ammonia are weakened at higher temperatures. Positive synergistic effects are observed for the O2 consumption and CO2 generation in blended-coal/ammonia cocombustion, and the addition of ammonia enhances this synergistic effect. Specifically, the combustion rate, O2 consumption, and the generation of CO2 of bituminous coal are promoted, whereas those of lignite are inhibited. Further analysis of the reaction pathways revealed that ammonia alters the intrinsic oxidation routes of coal molecules.