Numerical Study Of Ammonia And Coal Co-Firing Using Combustion Model In Drop Tube Furnace

Abstract

This study presents a numerical investigation of coal and ammonia (NH?) co-firing using Computational Fluid Dynamics (CFD) within a Drop Tube Furnace (DTF). The objective is to evaluate the influence of ammonia blending on combustion characteristics and pollutant formation. Simulations were conducted at three mixing ratios—25%, 50%, and 75% ammonia based on calorific value—to assess their impact on temperature distribution and flue gas emissions, including CO?, CO, and NOx. The results indicate that increasing ammonia concentration significantly reduces peak combustion temperatures due to its lower heating value and the formation of water vapor, which absorbs a portion of the released thermal energy. CO? emissions decreased substantially with higher ammonia content, as ammonia contains no carbon. However, co-firing with higher ammonia ratios led to elevated levels of CO and NOx emissions, primarily due to incomplete combustion and the nitrogen content inherent in NH?. In particular, NOx emissions spiked at the 75% ammonia level, highlighting the need for effective mitigation strategies such as air staging, burner optimization, and post-combustion treatments. Overall, while ammonia shows promise as a carbon-free fuel alternative, careful combustion system design is crucial to ensure high thermal efficiency and regulatory compliance.