Energy Fuels 2009, 23, 5813–5820 Published on Web 10/15/2009
: DOI:10.1021/ef900646p
Comparison of Natural Upward and Downward Smoldering Using the Volume Reaction Method Fang He*,†,‡ and Frank Behrendt‡ †
School of Agricultural Engineering, Shandong University of Technology, Zibo, 255049 China, and ‡Department of Energy Engineering, Berlin Institute of Technology, Berlin, 10623 Germany Received June 26, 2009. Revised Manuscript Received September 16, 2009
Natural forward smoldering (which normally occurs in thermochemical conversion of solid fuel) and natural reverse smoldering (which normally occurs in self-ignition fire in piled materials) have been compared theoretically using the volume reaction method. One-dimensional vertical propagation of piled char powder smoldering was used as the model case, in which upward smoldering is reverse smoldering while downward smoldering is forward smoldering. Calculation has revealed that there is significant difference between natural upward and downward smoldering. The following applies in our simulation case: (1) Upward smoldering is dominated by kinetics of char oxidation while downward smoldering is oxygen transport controlled. (2) The propagation velocity of upward smoldering is more than ten times faster than that of downward smoldering. However, the degree of carbon conversion of upward smoldering is much less than that of downward smoldering. (3) The temperature inside the fuel bed of upward smoldering (
