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Modeling discrete gas bubble formation and mobilization during subsurface heating of contaminated zones |
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| Authors: | Magdalena M Krol |
| Institution: | a University of Toronto, Department of Civil Engineering, Toronto, ON, Canada M5S 1A4 b Queen’s University, Department of Civil Engineering, Kingston, ON, Canada K7L 3N6 c Oregon Health & Science University, 20000 NW Walker Road, Beaverton, OR, USA |
| Abstract: | During thermal remediation the increase in subsurface temperature can lead to bubble formation and mobilization. In order to investigate the effect of gas formation on resulting aqueous concentrations, a 2D finite difference flow and mass transport model was developed which incorporates a macroscopic invasion percolation (MIP) model to simulate bubble expansion and movement. The model was used to simulate three soil scenarios with different permeabilities and entry pressures at various operating temperatures and groundwater velocities. It was observed that discrete bubble formation occurred in all three soils, upward mobility being limited by lower temperatures and higher entry pressures. Bubble mobilization resulted in a different aqueous mass distribution than if no discrete gas formation was modeled, especially at higher temperatures. This was a result of bubbles moving upwards to cooler areas, then collapsing, and contaminating previously clean zones. The cooling effect also led to possible non-aqueous phase liquid (NAPL) formation which was not predicted using a model without discrete bubble formation. |
| Keywords: | Discrete gas phase Temperature Thermal remediation Macroscopic invasion percolation Bubbles Buoyancy |
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