Modeling and analytical simulation of high-temperature gas filtration combustion

Abstract

High temperature filtration in combustion and gasification processes is a highly interdisciplinary field. Thus, particle technology in general has to be supported by elements of physics, chemistry, thermodynamics and heat and mass transfer processes. Presented in this paper is the analytical method for describing hightemperature gas filtration combustion in an inert porous medium. We assume the porous media is highly permeable and both the contact time between the phases and the rate of oxidizer diffusion through the gas stream to the surface of the solid particles where the reaction occurs are not large. Also, we assume that the initial temperatures increase lengthwise. The coupled nonlinear partial differential equations describing the phenomenon have been decoupled using the parameter-expanding method and solved analytically using eigenfunctions expansion technique. The results obtained revealed that the combustion wave is propagated and oxidizer is consumed. A self-oscillating mode of gas filtration combustion was found with variation in the values of interfacial heat transfer. ©JASEM https://dx.doi.org/10.4314/jasem.v21i5.20Keywords: Analytical method, filtration combustion, fuel, oxidizer, porous medium, temperature.Filtration combustion, when an oxidizer is injected into a porous medium containing fuel, has numerous applications in technology and nature (enhanced oil recovery by in situ ombustion, coal gasification, selfpropagating high-temperature synthesis (SHS), smolder waves etc.). A High temperature, high pressure gas filtration is a fundamental component of several advanced coal-fired power systems ( Endo Kokubun et al., 2016).Smoldering and SHS are both complicated processes involving chemistry; diffusive and convective transport of reactants, products, and heat through a porous medium; heat losses to the environment by radiation and convection (Wahle et al., 2003).Mathematical models for filtration combustion of gases and condensed materials are based on the equations of the mechanics of multiphase media supplemented with the equations of chemical kinetics (Aldushin and Merzhanov, 1988). A fairly complete review of experimental and theoretical studies of filtration gas combustion in inert porous media is presented in (AbdulMujeebu et al., 2009). Numerical two-dimensional calculations of temperature and concentration fields supported experimentally have been performed in (Brenner et al., 2000) for combustion of a methane-air mixture in a rectangular burner with an inert coarse-pore section. Unsteady filtration combustion of gases in an inert porous layer is considered in (Prokof'ev et al., 2010) taking into account the gas pressure distribution in the pores. Due to the complexity of two-temperature models, very few results have been obtained. Wahle et al. (2003) employed a two-temperature model to study coflow FC in a sample open to gas flow only at the ends of the sample.The objectives of this paper are to propose a twotemperature model for gas filtration combustion in an inert flat ...