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Low Temperature

Thermally enhanced free product recovery of former MGP site, North Adams, MA

At lower temperatures (<100°C), TCH is applied to the thermal enhancement of free product recovery and the thermal enhancement of existing Soil Vapor Extraction (SVE) systems.

Thermally Enhanced Free Product Recovery

Many non-aqueous phase liquids (NAPLs) are difficult to recover at ambient temperatures. The application of TCH at temperatures below 100°C is used to facilitate the recovery of NAPLs. This application of TCH uses an array of heaters at a spacing of 20 to 40 ft. Horizontal trenches are used for shallow applications while vertical wells are used for deeper applications. Existing or new free product recovery wells are located between the heaters. By increasing subsurface temperatures to below the boiling point of water, LNAPL viscosities are reduced ten- to one hundred-fold, greatly enhancing free product recovery.

TerraTherm applied the TCH technology to recover >16,000 gallons of coal tar. Previous attempts at cold temperatures had recovered only a few gallons.

Thermally Enhanced Soil Vapor Extraction

Contaminants trapped in low-permeability or high-saturation layers are not efficiently removed using typical SVE systems.

The primary SVE induced vapor flow bypasses those layers and contaminant removal stalls. This can lead to years of continued SVE operations, without reaching soil cleanup goals.

The application of TCH to these “stalled” sites can accelerate mass removal from such layers by increasing the vapor pressure of the contaminants, partially drying the recalcitrant layers, and accelerating biological and chemical degradation reactions. This application of TCH uses an array of heaters placed between existing SVE wells without interruption to present SVE operations. The site is heated slowly by applying power to the TCH heaters, while maintaining SVE operations.

Vapor flow during 'cold' SVE occurs through preferential pathways, bypassing lower permeability zones

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Thermally Enhanced SVE results in heating and vapor flow through all affected zones, with 100% sweep

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