Internal Combustion Engines for the Destruction of Hydrocarbon Vapors from Fuel-Contaminated Soils

Site Name:

Patrick Air Force Base



Period of

10/18/93 to 1/14/94


Field demonstration


Tom Davis
VR Systems
Anaheim, CA
Telephone: (714) 826-0483
Fax: (714) 826-8746

Internal combustion engine (ICE, as a supplement to SVE)
- Demonstration used a VR Systems Model V3 Ford Motor Company 460 in3 displacement engine, 55-gallon knockout drum prior to engine, and onboard computer
- Horizontal vent well installed at 4 ft bgs as part of a bioventing pilot test, and used in vapor extraction mode for demonstration
- During ICE demonstration, flow rate of 150 scfm and average engine speed of 1,790 rpm used for first 2 days, followed by a flowrate of 80 scfm
- Propane used as supplemental fuel; 1,925 ft3 used in first 2 days

Cleanup Authority:
Not identified

Air Force Contact:
U.S. Air Force
Center for Environmental Excellence
Technology Transfer Division
Brooks AFB, TX

Volatile hydrocarbons
- Initial soil gas contained TVH - 26,800 ppmv; benzene ND; toluene - 15 ppmv; ethylbenzene - 14 ppmv; xylenes 200 - ppmv; concentrations decreased after these initial levels were measured
- Low levels of oxygen and BTEX were found in the soil vapors

Waste Source:
Leaks from USTs

Type/Quantity of Media Treated:
Soil vapors
- Average depth to water table is 5 ft

Purpose/Significance of Application:
Use of an intenal combustion engine to treat extracted vapors from an SVE system

Regulatory Requirements/Cleanup Goals:
- The objectives of the demonstration included evaluating the performance and cost of the ICE technology

- Destruction efficiency was >99% for BTEX and >96% for TVH throughout the test period
- A 4% reduction in TVH destruction efficiency occurred when the engine rings and valves began to wear, allowing a portion of the propane to pass unburned through the exhaust

Cost Factors:
- Average operating cost was $325/day for first 5 days of operation, including equipment rental, propane, and labor
- Over the course of the test, operating costs ranged from $0.83 to 15.40/kg TVH destroyed, and $97 to 550/kg of BTEX destroyed
- Costs varied based on soil vapor concentrations and supplemental fuel requirements

A field demonstration of an internal combustion engine (ICE) technology for extracted soil vapors was conducted at Patrick Air Force Base in Florida. In Florida, soil vapor extraction must include a vapor treatment technology capable of removing 99% of the VOCs prior to discharge. The ICE demonstration was tested on the soil vapors extracted from a single extraction well at the Base Exchange service station.

The ICE tested was a Ford Motor Company 460 in3 displacement engine; it was preceded by a 55-gallon knockout drum. An onboard computer was used to control system operation. For the demonstration, the initial flow rate was 150 scfm with an average engine speed of 1,790 rpm, followed by rate of 80 scfm. Propane was used as supplemental fuel. The destruction efficiency measured was >99% for BTEX and >96% for TVH throughout the test period. The researchers found that initial soil gas oxygen levels were low, and they had to adjust flow rates to maintain an adequate oxygen/fuel ratio. They point out that ICE technology is most effective when initial soil gas TVH is greater than 40,000 ppm, when the unit can operate without supplemental fuel.