Influence of ash particles on radiative heat transfer in air- and oxy-fired conditions

Övrigt konferensbidrag, 2012

This work focuses on thermal radiation in oxy-fired conditions. Both gas and particle radiation is modeled in an axi-symmetric cross section of a cylindrical furnace and the influence of ash and its properties is investigated. Coal and ash particles are treated separately and their properties are calculated according to the Mie-theory. For the gas radiation, a Statistical-Narrow-Band (SNB) model is applied. The intensity field is calculated according to the discrete transfer method and scattering is assumed to be isotropic. Calculations are done on spectral basis, solving one intensity equation for each narrow band, to account for the spectral nature of the gases and the ash particles. 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. Temperatures and particle profiles are chosen to represent different sections of a boiler and gas concentrations corresponding to both dry and wet flue gas recycling are examined.