Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
9629184 | Fuel | 2005 | 13 Pages |
Abstract
Particle mixing caused by grate movement in a packed bed of solids is an important process for biomass combustion and waste incineration. In this paper, a diffusion model for particle mixing in a burning bed is proposed and the related diffusion coefficient is measured. The diffusion model was incorporated into a combustion model for waste incineration in an actual full-scale bed and numerical calculations were carried to assess the effect of different mixing levels on the burning characteristics of the furnace. In-bed measurement of temperature, oxygen concentration and particle movement was also made using a special electronic device. It is found that the modelled flame front reaches the bed bottom at an earlier stage for a higher level of particle mixing; the average burning rate ranges from 0.05 to 0.13Â kg/m2Â s and the mass loss rate for a higher mixing level can be twice of that for a lower mixing level. However, excessive mixing can cause significant delay in ignition or even extinction of the bed combustion; the obtained local air to fuel stoichiometric ratio covers a range from sub-stoichiometric (0.6 for the highest mixing level) to super-stoichiometric (1.6 for the lowest mixing level); the carbon in ash ranges from 3.5 to 10.5%; the most reasonable range of the particle-mixing (diffusion) coefficient is from 1.8 to 6.0Â cm2/min for a full-scale bed, according to the calculation.
Related Topics
Physical Sciences and Engineering
Chemical Engineering
Chemical Engineering (General)
Authors
Y.B. Yang, C.N. Lim, J. Goodfellow, V.N. Sharifi, J. Swithenbank,