THE INFLUENCE OF PARTICLE AND GASEOUS RADIATION IN OXY-FUEL COMBUSTION

Övrigt konferensbidrag, 2011

This work focuses on radiation in oxy-fired conditions. Both gas and particle radiation is modeled in an axi-symmetric cross section of a cylinder and differences between air- and oxy-firing are investigated. The particle radiation is modeled by empirical correlations accounting for spectral properties of coal particles and scattering of the particles is assumed to be isotropic. For the gas radiation, a Statistical-Narrow-Band (SNB) model is applied as reference. Included in the analysis is also a non-gray or banded formulation of the Weighted-Sum-of-Gray-Gases (WSGG) model and grey approximations. The investigated cases cover both air-and oxy-fired conditions and the properties of the combustion gas are based on measured data from a lignite flame in Chalmers 100 kW rig. Wall fluxes and the radiative source term along the cylinder diameter are compared to evaluate differences in the radiative heat transfer between air- and oxy-fuel combustion. Special emphasis is put on the load and distribution of particles, with both in-flame conditions as well as furnace exit conditions being examined. The different approximations for gaseous radiation are evaluated to quantify the errors they result in when they are applied in conditions with a high particle load.