https://www.sciencedaily.com/releases/2023/03/230316114029.htm

To this end, various combustion methods like air an staging and swirl flow have been proposed. However, the efficacy of these technologies in mitigating the pollutant emissions while maximizing the burnout performance has remained unclear. Now, in a recent study made available online on 31 December 2022 and to be published in Volume 268, Issue 1 of the journal Energy on 01 April 2023, an international team of researchers led by Prof. Gyungmin Choi of Pusan National University, Korea analyzed the effectiveness of combining swirl flow and air staging in improving the combustion performance and reducing pollution. "The exhaust tube vortex (ETV) structure accompanying the swirl flow improves flame stability and combustion performance, but has the disadvantage of generating a large amount of NOx emissions. In contrast, air staging technology creates a fuel-rich environment in the primary combustion zone, which has a positive effect on NOx reduction but negatively affects combustion performance," explains Prof. Choi. "Therefore, if these two technologies are appropriately combined and applied in real life, a synergistic effect that reduces the emission of air pollutants as well as improves combustion performance can be expected."

Accordingly, the team employed both simulations and experiments to study the combined effects of different swirl configurations and air staging within a 16-kWth retrofitted down-fired pulverized coal boiler. The coal boiler was composed of three sections: the swirl burner, the boiler, and the exhaust pipe. For staged combustion, staged air was divided into two sides and injected tangentially into the boiler. Liquified petroleum (LPG) gas was used for preheating and flame stabilization. The staged-air and LPG flow rates were regulated, and for each setting, the temperature was measured using thermocouples. Additionally, the amount of gas-phase species was measured using a multi-gas analyzer.