Page 497 - Air Pollution Control Engineering

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Emerging Pollution Control Technologies 469

6.2. Applications to Air Emission Control
Any point source of VOC can be controlled with an ICE-based system when the air
emission stream meets certain criteria. For this alternative to be economically attractive,
the air emission stream flow rate needs to be relatively small. The largest ICE-based sys-
tem is capable of processing an emission stream with a flow rate up to a few hundred
cubic feet per minute and a high concentration of VOCs. If the VOC concentration is less
than 1000 ppmv, then supplemental fuel requirements become excessive and process
becomes economically unfeasible. In California, ICE-based systems are commonly used
for VOCs; as a result, the majority of manufacturers are located in that state (23).
Relatively little information is available on the use of ICE technology on remediation
sites, but it is feasible for these systems to be utilized at Superfund sites to control emis-
sion stream from small-scale SVE systems and from small-scale air strippers. Because
their use is limited to small emission stream flows (several hundred cubic feet per
minute) the available literature has focused on the use of ICE to control emission streams
from SVE processes, capped-off landfills, and air stripping processes.
The ICE system becomes economically attractive when its use eliminates the need to
run electrical power to the site because the engine may be used to run vacuum fans and
other remediation equipment. Not only can these systems reduce utility costs, but they
can achieve destruction removal efficiencies (DREs) of 99+% when a catalytic converter
is incorporated into the system. Other advantages of the ICE system are their mobility
and small size. Disadvantages of the ICE system are their limited capacity of less than
several hundred cubic feet per minute, the noise levels emitted from the engine, and
monitoring requirements for controlling air-to-fuel ratio so that the engine operates effi-
ciently. The excessive noise levels can be controlled with sound-attenuating devices such
as mufflers and enclosures. A computerized system can be used to control the air-to-fuel
ratio so as to minimize monitoring costs.
Typically, ICE systems achieve removal efficiencies of 99% or greater. Pederson and
Curtis (23) recently compiled results of several studies in which they listed removal
efficiencies of different VOCs by ICEs from air emission streams from various SVE
and air stripping systems. The results from this study are shown in Table 2. Information
from case studies on ICE systems is summarized next.

6.2.1. ICE System Case Studies
VR Systems, an ICE vendor, supplies portable ICE systems that are designed to
control air emission streams from SVE systems and tank-degassing systems. These ICE
systems are designed to burn up to 100 kg/h (220 lb/h) of hydrocarbons. Additionally,
these systems utilize liquid propane or natural gas as a supplementary fuel and have a
computer system to control the air-to-fuel ratio to achieve higher DREs with fewer labor
requirements.
Another vendor (Kerfoot Technologies, Mashpee, MA) provides the Soil-Scrub ®
process that is used with a heat-assisted SVE system. An ICE system was provided as
primary control system for the emission from this SVE system. Additionally, the con-
trol system included a catalytic converter and GAC beds following the ICE system. The
case studied examined the use of this system on gasoline-soaked soil. This soil was first
encapsulated in plastic sheets and then was heated to 100ºC. The final DRE achieved was