摘要:

Research has indicated that the accurate calculation of char burning rates at diffusion-limited conditions requires consideration of the effects of voids (gaps in the continuous surface of burnable material that are deeper than their surface radius) on the particle burning area. Experimentally, void area distributions as a function of void size can be quantified using scanning electron microscopy and digital processing of quenched char particle images. Modeling void area distributions is problematic, even assuming voids behave as pores, because of initial surface imperfections and effects of combustion on surface morphology. This work examines the effects of factors that affect general pore formation for their effect on voids larger than 1 μm, such as heterogeneous combustion, devolatilization, and particle size and how these factors influence the calculation of diffusion limited burning rate from temperature and image data. Void distributions were predicted using an established pore distribution model, with and without the effects of pore combination. Results indicate that void distributions roughly follow expected pore behavior through devolatiltzation, but not after ignition, with void area fraction increasing with increasing coal volatile content and particle heating rate, but not significantly affected by oxygen concentration or initial particle size. Further, analytical pore models provide reasonable approximations for void distributions in the calculation of particle burning rates from temperature and image data.

ISSN:0010-2202    

DOI:10.1080/00102200008947280

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor

摘要:

The thermal and concentration structures of the combustion front in the bilayer samples were studied by mathematical simulation. The combustion limits restricted by heat loss at various thermal effects and thermophysieal characteristics of the layers were determined. The rise of the ambient temperature was shown to be an efficient way to the control over the combustion process. It was found that the rise of the ambient temperature to one characteristic interval increases the critical value of the heal loss factor more than twenty times for the governing parameters used in calculations.

ISSN:0010-2202    

DOI:10.1080/00102200008947281

出版商:Taylor & Francis Group    

年代:2000

数据来源: Taylor