Numerical analysis of ammonia/coal-volatile combustion under water dilution conditions
Yueru Chen, Bin Zhang, Jieyu Jiang, Xiaoyong Zhang, Xianran Zhu, Chunjie Sui
Abstract
Ammonia (NH 3 )/coal co-combustion offers an effective approach for reducing carbon emissions from coal-fired boilers while enhancing the combustion characteristics of NH 3 . The addition of NH 3 introduces fuel-N, and the use of water vapor dilution combustion technology can help lower NO X emissions. However, the use of H 2 O vapor as a diluent in combustion, particularly within NH 3 -coal-volatile co-combustion systems, remains under researched. This study addresses the gap by examining different NH 3 and H 2 O ratios. A new NH 3 /coal-volatile co-combustion mechanism was developed. The flame propagation characteristics of the laminar flame were analyzed. Additionally, the H/O/OH/CH 3 free radical pool was observed, and chemical reaction kinetics were analyzed to understand the mechanisms behind NO X (NO and N 2 O) reduction. The results indicate that increasing the ratio of H 2 O to NH 3 significantly reduces the laminar burning velocity while increasing the flame thickness. Such change also decreases and delays the peak mole fractions of H/O/OH radicals. Under stoichiometric conditions, H 2 O promotes the NH 2 +NO reaction. H 2 O also enhancing the thermal DeNO X process and effectively inhibiting NO generation.