Combustion rate of bituminous coal char in the temperature range 800 to 1700 K

✍ Scribed by Geoffrey D. Sergeant; Ian W. Smith

• Publisher: Elsevier Science
• Year: 1973
• Tongue: English
• Weight: 742 KB
• Volume: 52
• Category: Article
• ISSN: 0016-2361
• DOI: 10.1016/0016-2361(73)90012-4

✦ Synopsis

The combustion rates of three different sized fractions of char from a swelling bituminous coal have been measured in the temperature range 800 to 1700 K. The mass-median sizes of the fractions were 70, 35 and 18 pm. For each fraction the combustion rate was less than the limiting rate set by diffusion of oxygen to the particle. The chemical reaction rate coefficient (g/g s atm 02), calculated from the measured rates and corrected for the external diffusion resistance, varied with temperature in a manner appropriate to an apparent activation energy of approximately 27 kcal/mol for the three fractions. The chemical reaction rate coefficient when expressed on the basis of unit external area of particle (g/cm2 s atm 02) increased with increasing particle size at 800 K: at 1250 K the coefficients for the 35 and 18 pm fractions were equal, and lower than those of the 70 /.rrn fraction by a factor of 4. The densities of the particles did not vary appreciably with burn-off, except the density of the 70 pm fraction which increased sharply for values of burn-off between 0 and 001. It is probable that combustion occurred in a rate-control regime which was intermediate between that caused by chemical reaction alone and that caused by the combined effects of pore diffusion and chemical reaction.