Abstract
Combustion experiments on cylindrical bio-coke (BIC), a highly densified biomass briquette, have been
conducted to observe whether quasi-one-dimensional steady combustion can be attained in room temperature
air flow. In the experiments, the air flow velocity was the main test condition and the fuel consumption
rate when the bottom surface of the BIC sample burned was evaluated as the regression rate of the
combustion zone at the bottom surface. In addition, one-dimensional calculations based on an energy
equation at the combustion zone were conducted to understand the mechanism that results in steady combustion
and predict the effect of water and volatile matter content in BIC on the extinction limit. The
results showed that steady combustion of the BIC sample could be attained in 4.67 m/s or more, and,
in contrast, extinction was observed in 3.82 m/s or less. The critical regression rate explained by the combustion
zone temperature was shown, and the reason combustion becomes unsteady could be explained by
the energy balance at the combustion zone. Though the main reason for extinction was radiation heat loss,
the heat loss by water and volatile matter was not negligible. Therefore, the effect of water and volatile matter
content on steady combustion must be considered.
2014 The Combustion Institute. Published by Elsevier Inc. All rights reserved.