U.S. Air Force DOD Project - Case Study
Controlling the off-gas from a remediation project, where high concentrations of petroleum hydrocarbons are present, can be a difficult if not dangerous process when utilizing internal combustion engines and conventional oxidation technology.
In more recent years, the use of high vacuum pumps to accomplish both liquid and gas phase extraction — sometimes referred to as multi or dual phase extraction (MPE or DPE) — has further complicated the design requirements for safely applying off-gas treatment equipment.
The MPE technology relies upon the ability to maintain sufficient vacuum on the subsurface to accomplish the multiphase principle. Therefore the off-gas treatment system must process 100% of the hydrocarbon load. In many cases, this load is well above 50% of the lower explosive limit (LEL) and often has limited oxygen in the fume stream.
To date, conventional technologies, including internal combustion engines, thermal oxidizers and catalytic oxidizers, have all been applied with limited success on these hot sites.
The following case study represents real time experience in dealing with these different and difficult situations.
The end result of this project was the development of a hybrid off-gas treatment system designed to take the difficult and dangerous realities out of the equation.
An MPE system had been installed and was operating at a Department of Defense project for the U.S. Air Force. Free product on the site consisted of various jet fuels, diesel range organics and gasoline range organics. Concentrations in the effluent from the MPE ranged between 50,000-75,000 ppmv.
The off-gas from the MPE was being directed to an internal combustion engine (ICE). The ICE was having difficulty processing the hydrocarbon vapors and the unit itself required extensive maintenance, repair and on-site supervision to maintain operation. Overall uptime was poor and due to limited auxiliary fuel supply at the site, the ICE could only be used during the first stages of the project. An oxidizer would eventually have to be purchased for the project's longer-term operation.
The ICE was replaced with a Flame-Ox® high BTU thermal oxidizer developed by Catalytic Combustion Corporation.