Mechanism of smoldering of cellulosic materials

• Published in: Symposium, International, on Combustion Vol. 16; no. 1; pp. 1447 - 1457
• Main Authors: Moussa, N.A., Toong, T.Y., Garris, C.A.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 1977
• ISSN: 0082-0784
• DOI: 10.1016/S0082-0784(77)80427-X

A coordinated theoretical and experimental investigation of the mechanism of smoldering in cellulosic materials has been conducted. Both steady and transient smoldering have been observed for single cylindrical cellulosic elements, mounted horizontally in quiescent oxygen/nitrogen environments of varying pressures and compositions. An extinguishment limit, separating the steady from transient regions, is observed at well-defined combinations of oxygen mole fraction and partial pressure. In the region of steady smoldering, the measured propagation speed and maximum temperature in the smoldering zone depend on the oxygen partial pressure and mole fraction in the environment. However, independent of the environmental conditions, the speed is uniquely related to the maximum temperature. It is postulated that cellulose, upon heating, decomposes to yield char and volatiles. The char then reacts with oxygen, diffusing from the surroundings, to provide the heat flux needed to sustain pyrolysis. On the basis of this mechanism, the predicted characteristics of steady smoldering and of the extinguishment limit are found to be in good agreement with the experimental results, thus demonstrating the validity of the proposed mechanism.