Validation of the integral model for the pyrolysis of charring materials with a moving grid

Abstract

For the pyrolysis of charring materials a new one dimensional moving grid model is developed. The solid is divided by a pyrolysis front into a char and a virgin layer. Only when the virgin material reaches a critical temperature it starts to pyrolyse. The progress of the pyrolysis front determines the release of combustible volatiles. Since the model is used here as a stand-alone model, the external heat flux that heats up the solid, is assumed to be known.The char and virgin grid move along with the pyrolysis front. Calculations are done on uniform and nonuniform grids for the virgin layer. In the char layer only a uniform grid is used. Calculations done with a non-uniform grid are about 3 times faster than with a uniform grid.The moving grid model is used to validate the approximate integral model. This revealed that the integral model gives significant errors when there are sudden changes in the boundary conditions.