Simulating field-scale thermal conductive heating with the potential for the migration and condensation of vapors

Qianli Xie; Kevin G Mumford; Bernard H Kueper

doi:10.1016/j.jhazmat.2023.131439

Simulating field-scale thermal conductive heating with the potential for the migration and condensation of vapors

J Hazard Mater. 2023 Jul 5:453:131439. doi: 10.1016/j.jhazmat.2023.131439. Epub 2023 Apr 17.

Authors

Qianli Xie¹, Kevin G Mumford², Bernard H Kueper²

Affiliations

¹ Queen's University, Department of Civil Engineering, Kingston, Ontario K7L 3N6, Canada. Electronic address: qianli.xie@queensu.ca.
² Queen's University, Department of Civil Engineering, Kingston, Ontario K7L 3N6, Canada.

PMID: 37088018
DOI: 10.1016/j.jhazmat.2023.131439

Abstract

Thermal conductive heating (TCH) is an in-situ thermal treatment (ISTT) technology for treating non-aqueous phase liquid (NAPL) source zones. Numerical models can be useful tools for improving remedial performance, but traditional multiphase flow models are rarely used to simulate mass recovery during ISTT applications at the field scale due to their computational expense. This study developed a 3D model based on macroscopic invasion percolation to simulate the vaporization of NAPL, and the subsequent vapor migration and potential condensation at the field scale. The model was used to simulate the mass recovery of trichloroethene (TCE) from a NAPL source zone under seven scenarios of different heater placements, including three scenarios with an undersized target treatment zone (TTZ). Simulation results showed that TCH was effective in removing NAPL within the TTZ, but the treatment zone did not extend far from the perimeter heaters. In addition, during heating, NAPL condensation outside the TTZ due to the escaping vapor was observed in all scenarios. Overall, the resulting mass recovery was lower in the three scenarios with an undersized TTZ (91-95%) than in the other four scenarios (≈ 99%). Moreover, the locations of unrecovered/condensed NAPL could be inferred by monitoring mass recovery tailing at individual extraction wells.

Keywords: Condensation; Macroscopic invasion percolation; Source zone remediation; Thermal conductive heating; Trichloroethene.