Computational investigation of hydrodynamics, coal combustion and NOx emissions in a tangentially fired pulverized coal boiler at various loads--颗粒学报PARTICUOLOGY

Chang, J., Zhou, Z., Ma, X., & Liu, J. (2022). Computational investigation of hydrodynamics, coal combustion and NOx emissions in a tangentially fired pulverized coal boiler at various loads. Particuology, 65, 105-116. https://doi.org/10.1016/j.partic.2021.06.012

Computational investigation of hydrodynamics, coal combustion and NO_x emissions in a tangentially fired pulverized coal boiler at various loads

Jian Chang ^*, Zhijian Zhou, Xinrui Ma, Jinshuo Liu

School of Energy, Power and Mechanical Engineering, North China Electric Power University, Beijing 102206, China

10.1016/j.partic.2021.06.012

Volume 65, June 2022, Pages 105-116

Received 19 March 2021, Revised 22 May 2021, Accepted 21 June 2021, Available online 8 August 2021, Version of Record 8 November 2021.

E-mail: changjian@ncepu.edu.cn

Highlights

• Decreasing boiler loads impair air–fuel mixing and steady furnace combustion.

• High-temperature zone and flame move toward side walls with decreased boiler loads.

• O₂ and NO_x contents increase, whereas CO content decreases with reduced load.

• A decreased burner tilt angle favors heat transfer and NO_x emissions.

Abstract

This work presents a computational investigation of hydrodynamics, coal combustion and NO_x emissions in a tangentially fired pulverized coal boiler at different loads (630, 440 and 300 MW; relative loads of 100%, 70% and 48%) to clarify the effect of load change on the furnace processes. A computational fluids dynamics model was established; the flow field, temperature profile, species concentration and NO_x emissions were predicted numerically; and the influence of burner tilt angles was evaluated. Simulation results indicate that a decrease in boiler load decreases the gas velocity, attenuates the airflow rotations, and increases the tangent circle size. The high-temperature zone and flame moved toward the side walls. Such behaviors impair air–fuel mixing, heat transfer and steady combustion in the furnace. In terms of species concentrations, a decrease in boiler load increased the O₂ content, decreased the CO content, and decreased the char burnout rates only slightly. A change in boiler load from 630 to 440 and 300 MW increased the NO_x emissions from 202 to 234 and 247 mg/m³, respectively. Burner tilt angles are important in coal combustion and NO_x emissions. A burner angle of –15° favors heat transfer and low NO_x emissions (<185 mg/m³) for the current tangentially fired boiler.

Graphical abstract

Keywords

Combustion; NO_x emission; Tangentially fired boiler; Variable load operation; Computational fluids dynamics

文章导读