Mathematical Modeling of a 2.4 MW Swirling Pulverized Coal Flame

Abstract

Predictions and measurements of a swirling unstaged, high NO_x, pulverized coal flame are presented. The predictions have been obtained by means of relatively simple models for turbulence, turbulent combustion and turbulent nitric oxide chemistry. Turbulence is modeled using the standard k-epsilon model. The turbulent combustion model incorporates a two-step reaction scheme together with an eddy break-up model. In the NO- chemistry model, thermal-NO and fuel-NO chemical reaction rates are statistically averaged over the fluctuating temperature using the Beta probability density function. Radiation is computed by means of the Discrete Transfer Radiation model. A constant linear absorption coefficient is assumed while scattering is not taken into account. The paper contains a unique, comprehensive comparison between predictions and measurements of a pulverized coal flame issued from an industrial-scale burner. The coal fired was Gottelborn hvBb coal. Attention is paid to velocities, turbulence quantities, temperatures, coal burnout levels and species concentrations of oxygen, carbon monoxide, carbon dioxide, nitrogen oxides precursors and nitrogen oxides. Radiative heat fluxes near the furnace refractory wall and the heat extraction of the cooling loops are addressed also.

Keywords:

• Mathematical modeling
• pulverized coal
• turbulent diffusion flame
• eddy break-up concept
• nitric oxide formation
• probability density functions