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468 Lawerence K. Wang et al.

Fig. 10. Internal combustion engine-based VOC control system. (From US EPA.)

between the ICE and the incinerator is primarily in the geometry of the combustion
chamber. Figure 10 shows a simplified diagram of a typical ICE-based system. The
major components in an ICE-based system include the ICE (standard automobile or
truck engine), supplemental fuel supply (usually propane or natural gas), carburetor,
off-gas lines from remediation system, and additional air emission control devices
(adsorbent bed, catalytic converter, etc.). Additionally, an ICE-based system requires a
clean waste stream containing no acid and low levels of particulate matter; as a result,
a pretreatment device may also be required.
Another requirement for an ICE-based system is supplemental fuel to support com-
bustion when the VOCs in the airstream are insufficient. Supplemental fuel systems are
required for start-ups, remediation projects with low VOC extraction rates, and sources
such as soil vapor extraction (SVE) systems that produce changing VOC concentration
over time. Combustion in an ICE system is possible when the concentration for VOCs
in the air emission stream ranges from 60,000 to 100,000 ppmv at flow rates of 1.7–2.0
3
m /min or 60–70 acfm (22). Additionally, supplemental oxygen may be necessary to
dilute the gas stream if the VOC level exceeds 25% of the lower explosive limit. The
carburetor for automobile or truck engines must be modified to include two input
valves: one for gaseous fuel (air emission stream containing VOCs) and the other for
the supplemental liquid fuel.
The mobility of the ICE-based system is a major advantage of this technology.
When the air emission stream provides sufficient energy to operate the system without
the use of a supplemental energy source, then the mobility advantage of the ICE-
based system is further enhanced. Another advantage of the ICE-based system is
ready availability of parts for the automobile engine or truck engine and widespread
knowledge of the operation and maintenance of the engine. Additionally, control of the
emission stream from the ICE-based system can be accomplished with an off-the-shelf
automobile catalytic converter, which is relatively inexpensive when compared to a
custom-made unit.