Study On The Radiation Properties Of Coal Particles With The Burnout Rate Changes

Radiation heat transfer is the main heat transfer mode of combustion in the furnace.The radiation properties of the suspended particles, which are mixture of ash dispersed in thespace, and unburned carbon with different burnout rate, have an important influence on theaccurate calculation of the radiation heat transfer in the furnace. Although the single carbonparticle burns out fast, the burn-out states always exist in the big space due to theunevenness of the combustion. Thus it is of great importance to discuss the radiationproperties of the coal particles under different burnout rate.Process of the traditional solution, which is used to solve the radiation properties ofthe coal particles with the burnout rate changes, is generally based on the equaldiameter-variable density model or the equal density-shrinking core model. Based on thetraditional solving models, combining the pore volumes which are measured by theexperiment, it makes improvements to the traditional solution. Results calculated by theimproved model are more consistent with the actual situation.Then, the radiation properties of eight different kinds of coal particles with the burn rate changesare calculated by the improved model. It is found that size distribution have an important effect on theparticle radiation properties. With the increasing of the particle size, the monochromatic extinction,scattering and absorption efficiency curves under the same burn-out rate move to the larger wavelength.The monochromatic extinction, scattering and absorption efficiency curves of different kinds of bitumiteunder the same burn-out rate are almost the same, this is mainly because of the little difference in thecontent of bitumite. However, the monochromatic extinction, scattering and absorption efficiency curvesof different kinds of lignite under the same burn-out rate are not quite the same, this is because of thecomplex structure of lignite and the big difference in the content of lignite. What’s more, the averagemonochromatic absorption efficiency of lignite decreases with the burnout rate increasing, while theaverage monochromatic extinction, scattering and absorption efficiency of anthracite increase with theburnout rate increasing.