Steam Injection and Hot Air Stripping

In situ injection of steam has been a common practice in the oil fields of southern California for several decades. The addition of heat reduces the viscosity of the crude oil, allowing it to migrate more easily. The increased temperature also beneficially increases the vapor pressure of the oil, which allows volatile compounds to be more easily recovered. For most VOCs, vapor pressure doubles for every 20°C increase in soil temperature. The use of injected heat, steam, hot water, or air exemplifies the effective transfer of technology from other fields. 

Injection of steam or heated air into the subsurface provides large amounts of thermal energy, which speeds the mobilization of adsorbed organic contaminants and results in their removal as either a vapor or liquid phase. Elevated temperature increases the vapor pressure of the chemicals involved and promotes transfer of constituents across the air-water interface, which results in the increased removal of contaminants in high-humidity or nearly saturated soil systems. Additionally, the presence of high-temperature water sometimes results in oxidation or hydration of organic contaminants. 

Steam (or hot air) injection requires the placement of injection wells outside the contaminated area and extractions near the center of the targeted treatment area. 

FIGURE 10.7 Air sparging pilot test showing portable compressor, airflow regulator meter/oil filter, and injection well layout (A), injection well with quick connect air line and pressure gauge (B), and observation well with magnihelic pressure gauge sensitive to 0.01-in. water column (C). 

FIGU RE 10.8 Schematic showing use of injected steam for the remediation of hydrocarbon-impacted soil. 

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