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Show THE INFLUENCE OF SIZE DISTRIBUTION CHARACTERISTICS IN HETEROGENEOUS COMBUSTION f Donald J. Holve, Jacob Hoornstra J, and Thomas H. Fletcher Sandia National Laboratories Livermore, California for presentation at the American Flame Research Committee 1985 Fall Meeting, October 17-18 Sandia National Laboratories Livermore, California ABSTRACT Recent measurements have underscored the importance of pulverized fuel size distribution effects in combustion processes. In addition to conventional pulverized fuels, new physical forms, such as ultrafine grind coals, are being investigated in both dried and liquid form. Coal/water slurries exhibit many positive features, but atomization and agglomeration effects on the spray size distribution present drawbacks for efficient use in combustion systems. This paper presents an overview of the effects of size distribution on (1) devolatilization (including the effects of volatiles combustion and char formation), (2) char combustion, and (3) flyash size characteristics. W e also present some recent measurements of particle size distributions for pulverized coal and coal/water slurries burning in a laminar flow reactor along with some calculations of particle combustion behavior. The relative importance of physical (e.g., initial size distribution and particle swelling) and chemical effects throughout the combustion process is discussed. In general, the top end of the size distribution controls char burnout, the mid-range initiates the ignition process, and the entire distribution spread determines the formation of residual flyash. These results show that use of a mean value for the size distribution is inadequate for describing the effects of particle size on the combustion process. t Research conducted at the Combustion Research Facility and sponsored by the United States Department of Energy through the Pittsburgh Energy Technology Center's Direct Utilization Advanced Research and Technology Development Program. J Netherlands Energy Research Foundation UECN", Petten, The Netherlands 8-1 |