United States
Environmental Protection
Agency
EPA/540/MR-94/528
November 1994
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Demonstration Bulletin
Radio Frequency Heating
KAI Technologies, Inc.
Technology Description: Radio frequency heating (RFH) is
a process that uses electromagnetic energy in the radio fre-
quency (RF) band to heat soil in situ, thereby potentially enhanc-
ing the performance of standard soil vapor extraction (SVE)
technologies. An RFH system developed by KAI Technologies,
Inc. was evaluated under the Superfund Innovative Technology
Evaluation (SITE) Program at Kelly Air Force Base (AFB) in San
Antonio, TX. This demonstration was performed in conjunction
with a technology evaluation being performed by the U.S. Air
Force (USAF).
Figure 1 is a schematic diagram of KAI's RFH system. A 25-kW,
27.12-MHz RF generator serves as the energy source for the
system. Coaxial transmission lines supply energy to two anten-
nae installed near the center of the treatment zone, progres-
sively heating the soil in a radial direction from each antenna.
Water and contaminants volatilize as the soil is heated.
Prior to the demonstration, six extraction wells were installed on
the edges of the treatment zone, and two extraction wells were
installed near the center of the treatment zone. A vacuum was
applied to one or more extraction wells. The vacuum level and
the extraction wells to which the vacuum was applied were
varied periodically throughout the demonstration. The vacuum
system pulled water and contaminant vapors into the extraction
TD1&TD2Q
wells, through a vapor collection system, and into a vapor
treatment system. The vacuum was applied throughout the heat-
ing portion of the demonstration, for 11 days before heating was
initiated, and for 14 days during cooldown.
The treatment zone was covered by a vapor barrier, which was
designed to eliminate direct contact between the surface of the
treatment zone and the ambient air. The vapor barrier had three
functions: to help maintain a vacuum for vapor collection, to
prevent fugitive emissions from the heated surface, and to
control infiltration of air into the treatment zone and thus into the
vapor treatment system.
The yapor treatment system consisted of condensate collection
and incineration. Vapors that condensed in the vapor collection
and treatment systems were collected, and were then trans-
ferred to a Kelly AFB wastewater treatment facility. Uncondensed
vapors were burned in a natural gas flare. This vapor treatment
system was site- and contaminant-specific and was not evalu-
ated as part of the RFH system.
Waste Applicability: RFH is a potential enhancement for in
situ SVE systems. RFH is designed to speed the removal of
volatile organics and to make it possible to remove semivolatile
organics that would not normally be removed by standard SVE
/\ - antenna
Q - pressure transducer
^ - extraction well
• - infrared temperature and electric
field profiling wells
• - thermowell
X • thermocouple string
= vapor collection linos
TC3
O x
TD6&TD3
O
TD5&TD2
TD4
E8
QTD7&TD8
Figure 1. Schematic diagram of KAI RFH system.
Printed on Recycled Paper
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technologies. Inorganics, metals, and other nonvolatile contami-
nants will not normally be treated by SVE or RFH technologies.
Demonstration Results: The original treatment zone, which
Was within an area historically used for intermediate storage of
wastes, was 10ft wide, 15ft long, and 20ft deep. RF heat was
only applied to the upper half of the treatment zone, however. As
a result, the upper half of the treatment zone is being designated
the "heated zone." Samples were collected inside the original
treatment zone, which includes the heated zone; below the
original treatment zone to a depth of 30ft; and on two sides of
the original treatment zone.
During the demonstration, RF energy was initally applied to
antenna A2 for 25.6 days, was then applied to antenna A1 for
9.8 days, and back to antenna A2 for 11.1 days. Temperatures
within and outside the treatment zone were monitored at various
depths throughout treatment. KAI's target temperature range for
the heated portion of the treatment zone was 100 to 130°C. The
maximum temperature on the perimeter of the treatment zone
was approximately 60°C. The maximum temperature recorded
near the center of the treatment zone was 2340C, but this peak
Was hot representative of the majority of the temperature mea-
surements a{ this location. During most of the heating period,
temperatures between 100 and 150°C were measured near the
antenna to which energy was being applied. Although not ob-
served during the demonstration, the developer claims that tem-
peratures will become more uniform after all moisture is removed
from around the antennae.
i ! JIB : ' : ' ' ' , . -' '•!
Changes In soil contaminant concentrations were evaluated as
matched pairs; each post-treatment sample was compared to its
corresponding pre-treatment sample. The primary objective of
the demonstration was to evaluate the removal of total recover-
able petroleum hydrocarbon (TRPH) concentrations (as measued
by EPA Method 418.1, following extraction with freon). The
TRPH concentration inside the original treatment zone exhibited
a 29% decrease between pre- and post-treatment sampling.
Inside the heated zone, the TRPH concentration exhibited a 42%
decrease between pre- and post-treatment sampling.
Changes in pre- and post-treatment concentrations of volatile
and semivolatilo organic compounds (as measured by SW-846,
Method 8240 and 8270, respectively) were also evaluated. Be-
cause pretreatment concentrations of these compounds were
expected to be low, these analyses were considered non-critical
and were performed for only half of the matched sample pairs.
Preliminary data indicate that pre- and post-treatment concen-
trations of many volatile and semivolatile organic compounds
were near or below practical quantitation limits, but final data
may indicate removal of some of these compounds.
A Technology Evaluation Report and an Innovative Technology
Evaluation Report describing the complete demonstration will
be available by summer 1995.
For Further Information:
EPA Project Manager:
Laurel Staley
U.S. Environmental Protection Agency
Risk Reduction Engineering Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
(513) 569-7863
Kelly AFB Project Engineer:
Ms. Victoria Wark
SA/ALC/EMRO
305 Tinker Drive, Suite 2, Building 305
Kelly AFB, TX 78241 -5915
(210) 925-1812
USAF Technical Program Manager, Site Remediation Division:
Mr. Paul F. Carpenter
AL/EQW-OL
139 Barnes Drive, Suite 2
Tyndall AFB, FL 32403
(904)283-6187
Halliburton NUS Project Manager:
Mr. Clifton Blanchard
Halliburton NUS
800 Oak Ridge Turnpike, Suite A600
Oak Ridge, TN 37830
(615) 483-9900
Process Vendor:
Mr. Raymond Kasevich
KAI Technologies, Inc.
170 West Road, Suite 7
Portsmouth, NH 03801
(603)431-2266
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
Penalty for Private Use
$300
BULK RATE
POSTAGE & FEES PAID
EPA
PERMIT No. G-35
EPA/540/MR-94/528
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