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.
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.
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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