HEAT-TRANSFER MECHANISMS AND MULTISTEP KINETICS IN THE ABLATIVE PYROLYSIS OF CELLULOSE

A new model is presented of a cellulosic cylinder which thermally degr ades, because of a high pressure contact of its bottom side against a hot spinning disk. From the chemical point of view, the solid undergoe s, in the first place, a depolymerization process with the formation o f a molten active intermediate which. subsequently, vaporizes or gives rise to the formation of chars and gases. From the physical point of view, the model accounts for transport phenomena through the porous so lid and the molten layer (adjacent to the hot plate) whose properties and size vary during thermal degradation. The dependence of process dy namics, ablation rate, thickness of the reaction zone and product yiel ds on the plate temperature and applied pressure are simulated. Some i mportant experimental findings are confirmed.