Considerations on Temperature Dependent Effective Diffusion and Permeability of Natural Clays

Area of Science:

• Materials Science
• Geochemistry
• Chemical Engineering

Background:

• Understanding gas transport in porous materials is crucial for industrial processes like clay brick firing.
• Clay properties significantly influence gas diffusion and permeability, especially under thermal stress.

Purpose of the Study:

• To investigate the temperature-dependent diffusivity and permeability of porous clay samples.
• To elucidate the role of CO2 surface diffusion in gas transport mechanisms within clays.

Main Methods:

• Gas diffusion and permeability measurements in a diffusion chamber from ambient to 900 °C.
• Application of the mean transport-pore model and Darcy's law for analysis.
• Expansion of the diffusion model to include surface diffusion effects.

Main Results:

• CO2 diffusivity increased significantly with temperature, while O2 diffusion showed limited increase.
• Surface diffusion of CO2 was identified as a key factor explaining observed diffusivity.
• Permeability progressively increased with temperature, consistent with existing literature.

Conclusions:

• Incorporated carbonates in clay significantly influence gas-phase diffusivity.
• CO2 surface diffusion appears to be an intrinsic property of natural clays.
• Temperature-dependent gas transport characteristics are vital for understanding clay thermochemical processes.