Session: Poster Session

Paper Number: 157874

Numerical and Experimental Study of In-Situ Sncr Reaction in Conceptual Design Burner 

Ammonia has gained significant attention as a potential alternative fuel for carbon neutrality. Its low liquefaction pressure (-33.6℃ or 10 bar) enables efficient storage, and its relatively high energy density (12MJ/L) compared to hydrogen makes it suitable for large-scale industrial facilities with high energy consumption. However, several challenges must be addressed to replace fossil fuels widely used in existing industries. Notable issues include flame instability caused by slow flame propagation speed and narrow operating conditions, as well as excessive fuel NO_X emissions during combustion due to the nitrogen atom in its molecular structure.

In our previous study, we designed a swirl burner for fuel ammonia combustion and analyzed the effect of swirl intensity on the recirculation zone using numerical method. When comparing the combustion of methane and ammonia at stoichiometric conditions using the designed burner, the outlet temperature of ammonia was approximately 150 K lower than that of methane, but the NO_X emissions were about three times higher (1903 ppm and 489 ppm). To reduce the excessive NO_X emissions during ammonia combustion, we devised an in-situ SNCR system that incorporates selective non-catalytic reduction (SNCR) technology. This system is similar to multi-stage combustion but differs in that it uses secondary injected ammonia as a reducing agent. In this study, combustion was initiated in the 1^st stage using ammonia as the main fuel, and a 2^nd stage combustion zone was created to induce the reduction reaction. The injection flow rate, injection location, and mixing ratio were set as design variables, and numerical simulations and experiments were conducted to analyze the effects of local equivalence ratio variations and residence time of ammonia on NO_X reduction and combustion efficiency.

Numerical simulation showed that NO_X reductions of up to 99% or more were achieved when the reductant injection volume was high, but unreacted ammonia emissions increased linearly. Conversely, when the reducing agent injection rate was insufficient, no unreacted substances were emitted, but the NO_X reduction rate decreased significantly. Analysis of the reaction pathway showed that intermediate products (NH₂, NH) generated from ammonia activated a type of SNCR reaction that reduces NO_X. The SNCR reaction showed higher activity with increased injection flow rate, and it was observed that the decomposed NO_X ultimately formed N₂. To address the conflicting goals of NO_X reduction and ammonia emissions, the research team developed a statistical predictive model based on numerical analysis results to derive the optimal in-situ SNCR conditions. The optimal operating conditions were found to be when the stage injection rate was less than 30% and the residence time was sufficient.

In this study, we induced a reduction reaction by secondary injection of ammonia into the combustion zone to reduce excessive NO_X generated during the combustion process of fuel ammonia. Numerical simulation results confirmed the activation of the NO_X reduction reaction pathway, and an optimal operating condition was derived through a predictive model for various design variables. A lab-scale burner was constructed, and the simulation results were verified through experiments.

Presenting Author: Jonghyun Kim Chosun Univeristy

Presenting Author Biography: Jonghyun Kim is a Ph.D. candidate in the Department of Mechanical Engineering at Chosun University, South Korea. His research focuses on developing high-efficiency and low-emission gas turbine combustion systems. Specifically, his research interests include combustion stability enhancement, NOx reduction technologies, and carbon-neutral technologies through hydrogen-blended combustion. By combining various fields such as thermoengineering, energy utilization and reaction technology, and reaction physics, he aims to contribute to the development of future energy systems.

Authors:

Jonghyun Kim Chosun Univeristy
Minhyeok Kim Chosun University
Jungsoo Park Chosun Univeristy