CFD Evaluation of Heat Transfer and NOx Emissions When Converting a Tangentially Fired Coal Boiler to Use Methane

Abstract

The need to reduce global carbon dioxide (CO2) emissions is driving the conversion of coal-fired power plants to use methane, which can reduce CO2 emissions by >40%. However, conducting gas firing in coal boilers changes the heat transfer profile; therefore, preliminary evaluations using computational fluid dynamics are required prior to conversion. Here, methane was used as a heat input source in the simulation of an existing coal boiler, and combustion, nitrogen oxides (NOx) emission characteristics, and heat transfer profile changes inside the boiler were analyzed. Furthermore, changes in the burner zone stoichiometric ratio (BZSR) were simulated to restore the decreased heat absorption of the furnace waterwall, revealing that air distribution could change the heat absorption of the waterwall and tube bundles. However, this change was smaller than that caused by conversion from coal to methane. Therefore, to implement gas firing in coal boilers, alternatives such as output derating, using an attemperator, or modifying heat transfer surfaces are necessary. Despite these limitations, a 70% reduction in NOx emissions was achieved at a BZSR of 0.76, compared with coal. As the BZSR contributes significantly to NOx emissions, conducting gas firing in existing coal boilers could significantly reduce NOx and CO2 emissions.

Applying the Random Forest Method to Improve Burner Efficiency

“…When burning fuel in combustion devices, it is necessary to ensure that the most economical mode is maintained to reduce the emission of pollutants. When organizing the operation mode of the combustion devices of power plants, it is required to organize the influence of heat and mass transfer processes and aerodynamics on the ongoing chemical reactions in such a way as to ensure the most complete and environmentally friendly fuel combustion [1,2]. At high temperatures, a certain amount of toxic nitrogen oxides is formed in the combustion chamber in the form of NO, NO 2 , N 2 O 4 , N 2 O 5 , etc., along with emissions of SO 2 , CO 2 [3,4].…”