Understanding pressure changes in smouldering thermal porous media reactors

Abstract

The use of thermal porous media reactors for environmental applications is growing rapidly. Understanding the pressures increases inherent in such systems is central to their success. Numerical modelling of thermal processes in porous media, supported by experiments, quantifies and explains the pressure increases occurring during gas injection into smouldering treatment systems. Air flux and pressure gradient are revealed to be linked by the pneumatic conductivity of the porous bed at two scales. Locally, air density, viscosity, and velocity are coupled to temperature. However, the air pressure gradient increases globally due to a global reduction in pneumatic conductivity. Finally, a new, simple method to estimate the maximum bed pressure drop for thermal porous media reactors is presented. Overall, this work provides the first quantitative analysis of these local and global phenomena in such systems and provides a simple design tool for engineers.