Smoldering Combustion in Cigarette Smoking and Generation of Combustion Byproducts

The process of cigarette combustion was analyzed in the framework of the filtration combustion theory, with a focus on the puff phase of the smoking cycle. Smoldering combustion regimes were examined by considering gas flow fields established within the cigarette during continuous draw, the kinetic regimes relevant to the propagation of smoldering combustion waves and the influence of the smoldering combustion regime on the fate of cigarette components. Particular emphasis was given to the assessment of the conditions that promote oxidative pyrolysis of the cigarette components, as opposed to inert pyrolysis of the same components in oxygen-starving atmospheres. The experimental activity was directed along a twofold pathway. On one hand, the process of smoldering combustion of a porous tobacco matrix was characterized under preset continuous draw conditions by means a purposely designed reactor. Experiments were directed to the characterization of the rate of propagation of combustion and thermal degradation fronts as well as on the prevailing nature--oxidizing vs. reducing--of conditions established during the thermal degradation of cigarette components. On the other hand en masse thermal analysis of tobacco was performed under thoroughly controlled conditions by means of a combined thermogravimetry/mass-spectrometry technique. Experiments were directed to assess the rate and yields of pyrolysis of selected cigarette components under a variety of test conditions. In particular, the relevance of the reaction environment (oxidizing versus inert) to the course of pyrolysis and to the process yield toward selected representative compounds was analyzed and discussed.