Gas-Solid Nonequilibrium in Filtration Combustion

Faculty:  Chris Wahle

Summary:

Filtration Combustion (FC) involves a heterogeneous reaction between the reactive component of a porous solid sample and an oxidizer carried by a gas which flows through the pores of the solid matrix.  The applications of filtration combustion include, but are not limited to, natural processes, such as underground fires and smoldering, and technological processes, such as regeneration of coked catalysts, coal gasification, self-propagating high temperature synthesis (SHS), extraction of oil, and waste incineration.  Our primary focus is on the applications to SHS.  SHS is a technique that employs combustion waves to synthesize materials.  In this process, ignition at one end of a porous powder sample initiates the propagation of a high-temperature combustion wave which travels through the sample while using the internal energy of the reaction to convert the reactants into desired products.  SHS is a useful technological process and the goal is to ensure propagation leading to complete conversion of the reactants. Conventionally, the solid and the gas particles are assumed to attain rapid thermal equilibrium, so that the two phases share a common temperature distribution, and thus, only a one temperature model is required.  However, analysis of FC by means of a two temperature model reveals an alternate mode of combustion which has received little attention in the literature. The mode corresponds to rapidly propagating combustion waves which depend on a pronounced temperature difference between the two phases.  This research involves the analytical and numerical investigation of the rapid mode of propagation.  Rapidly propagating FC waves may prove to be quite beneficial in the SHS application since rapidly propagating FC waves can synthesize materials more rapidly and efficiently.  In other contexts, rapidly propagating FC waves are more dangerous due to the faster propagation velocity and higher burning temperature.

Publications:

1. Effects of Gas-Solid Nonequilibrium in Filtration Combustion, C.W. Wahle, B.J. Matkowsky, and A.P. Aldushin, Combustion Science and Technology, 2003, 175, pp. 1389-1499.


2. Rapid, Buoyant Filtration Combustion Driven by Convection C.W. Wahle and B.J. Matkowsky, Combustion and Flame, 2001, 124, pp. 14-34.