Simulation of Soot Formation in Pulverized Coal Combustion under O₂/N₂ and O₂/CO₂ Atmospheres

Abstract

In this study, simulations were carried out to study the combustion characteristics within a 600 MW W-shaped pulverized coal boiler under O₂/N₂ and O₂/CO₂ atmospheres. The objective of this work is to develop and validate a novel model for pulverized coal combustion under O₂-enriched conditions, specifically optimized for the O₂/CO₂ atmosphere. The innovation in this model lies in the precise calibration of kinetic constants for soot nucleation and surface growth rates, enabling a more accurate simulation of flame characteristics (such as the flame temperature and soot volume fraction) under O₂-enriched combustion conditions. The study reveals that an increase in the O₂ concentration significantly reduces the combustion flame height and flame penetration depth, thereby enhancing the local temperature inside the furnace. Moreover, at higher oxygen concentrations, the high levels of OH and O accelerate the oxidation reaction rate and shift the high-temperature zone upward. Subsequently, the maximum value of the nucleation rate increases. Therefore, compared to those of the O₂/N₂ atmospheres, in the O₂/CO₂ atmospheres, the peak volume fractions of soot decreased by 0.72, 25.5, and 15.9% for oxygen contents of 21, 30, and 40%, respectively. This demonstrates the impact of the oxidizing environment on soot production. Therefore, this study delves into the effects of oxygen concentration and temperature on soot formation and provides a new model for better predicting and optimizing combustion processes in industrial applications.