v-/EPA
United States
Environmental Protection
Agency
EPA/540/MR-94/507
April 1994
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Demonstration Bulletin
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Thermal Desorpticn System
Clean Berkshires, Inc.
Technology Description: A thermal desorption system
(TDS) has been developed by Clean Berkshires, Inc. (CBI),
Lanesboro, Massachusetts for ex-situ treatment of soils and other
media contaminated with organic pollutants. The TDS uses heat
as both a physical separation mechanism and as a means to
destroy contaminants. The process is continuous and is com-
posed of three different operations: feed preparation, contami-
nant volatilization, and gas treatment.
Feed preparation begins with a sequence consisting of crushing,
shredding, and screening excavated or dredged waste material
to reduce maximum particle size to 3/4-inch. Next, using a front-
end loader, the waste is repeatedly folded into itself in an attempt
to distribute moisture and pollutants evenly. This step is particu-
larly important since it helps protect the system from severe,
sudden thermal shocks caused by "hot spots" in the waste. The
prepared material is then dumped into surge bins and fed into a
kiln through a two-stage conveyor belt system.
Contaminant volatilization begins after the prepared material en-
ters the kiln. The temperature of the soil is increased through
contact with an air stream heated by a natural gas burner located
at the entrance of the kiln. The kiln is equipped with specially
designed flights which lift and veil the soil, exposing greater
surface area to the hot gases, improving volatilization. Treated
soil exits the kiln and enters a pug mill which combines the
material with solid residuals from gas treatment. Water recycled
from the quench tower is added at this time to cool the treated
materials and to control fugitive dust emissions. The solids are
deposited onto a discharge conveyor and stockpiled.
Gas treatment begins when the gas stream from the kiln, which
contains volatilized contaminants and entrained paniculate, en-
ters a multi-stage treatment sequence. The sequence uses the
following: a cyclone to remove coarse particulate, a high-effi-
ciency afterburner to destroy organics, a quench tower to cool
the gas stream, and a baghouse to remove filterable particulate
still suspended in the gas stream. A scrubber could be added to
remove sulfur dioxide if levels are high enough to impact air
quality standards. Treated gases exit the system through a 75-
foot high stack. Solid residuals from gas treatment are trans-
ferred by a screw auger to the pug mill and are combined with
the treated waste material.
The TDS is transportable and is monitored and controlled by a
computer-based data acquisition system.
Waste Applicability: The CBI TDS process has been
successfully applied at two sites processing soils from throughout
New England and New York. To date, over 250,000 tons of solid
wastes have been treated using this technology. The CBI TDS
can remove volatile organic compounds (VOCs), semivolatile
organic compounds (SVOCs), organometallic complexes, and
total petroleum hydrocarbons (TPHs). Full-scale CBI TDS opera-
tions] have been used to remove VOCs such as benzene, tolu-
ene, ethylbenzene, and xylene (BTEX); SVOCs such as naphtha-
lene, phenanthrene, chrysene, benzo(a)pyrene, and other poly-
nuclear aromatic hydrocarbons (PAHs); organometallic complexes
such; as ferricyanides; and TPHs in the range of C4
toC,'.
Demonstration Results: The CBI TDS Demonstration
took place at the Niagara Mohawk Power Corporation's Reme-
diation Technologies Demonstration Facility at Harbor Point in
Uticaj New York between November 15 and December 13,1993.
Figure 1 is a photo of the TDS used at this site. Harbor Point is
the site of a former manufactured gas plant (MGP) and is con-
taminated with BTEX and PAHs, ferricyanide compounds, and a
variety of heavy metals. Four different types of MGP solid
wastes were tested: (1) coke plant residuals; (2) purifier wastes;
(3) water gas plant residuals; and (4) Utica Terminal Harbor
sediments. Maximum pollutant concentrations were 320 milli-
grams per kilogram (mg/kg) BTEX; 3500 mg/kg PAHs; 1200 mg/
kg cyanide; 60 mg/kg arsenic; and 320 mg/kg lead.
Three 4-hr replicate runs were conducted for each waste type.
For each run, samples were collected from feed soil, treated soil,
cyclone solids, baghouse solids, quench water, intake water, and
stack gases. Samples were analyzed for PAHs, BTEX, cyanide
and metals. Feed soil samples were also analyzed for other
chemical and geotechnical parameters.
Critical operating parameters were optimized and monitored for
each {waste type. Soil feed rate and kiln soil exit temperature
were varied for each waste stream, based on preliminary results
from an experimental test phase. The range for each parameter
was as follows: feed rate, 16 to 22 tons per hour; kiln soil exit
temperature, 620 to 860 °F; afterburner residence time, 0.82 to
0.87 seconds; and afterburner temperature, 1810 to 1820°F.
Printed on Recycled Paper
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Hgure 7. Ctean Berkshlres, Inc. Thermal Desorption System
Preliminary results from the SITE Demonstration are summarized
below: *
• The CBITDS achieved DREs of 99.99 percent or better in
alt 12 runs using total xylenes as a volatile principal or-
ganic hazardous constituent (POHC).
* DREs of 99.99 percent or better were achieved in 11 of 12
runs using naphthalene as a semivolatile POHC.
* Average concentrations for critical pollutants in treated
soils were 0.066 mg/kg, BTEX; 12.4 mg/kg, PAHs; and 5.4
mg/kg total cyanide.
• Comparison of the dry weight basis concentration of pollut-
ants in the feed and treated soil showed the following
average removal efficiencies: 99.8 percent, BTEX; 986
percent, PAHs; and 97.4 percent total cyanides.
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• The CBI TDS showed good operating stability during the
Demonstration with only a minor amount of down time.
An Innovative technoiogyEvaiuatiori Report describing the com-
plete Demonstration will be available in the Fall of 1994.
For Further Information:
• i, '., ;"'1 , .in1 ii!, , , i1 "'i"" i iri1'1"1:11'1! ..... .'iih;-!''"!.!,!:; '"iiij.!.;!1 v:i t ..p .in „ iii'iwr i1 w».ii: ' ,,i, ,i ' ! "'«,,,,, ,„ : i ' w, ...... H? "ir, .1,, !,• ...... B, .m , uttri't,,, ,u nn 'i|!i.i,i.:
EPA Project Manager
Ronald F. Lewis
U.S Environmenta.1 Protection Agency
Risk Reduction Engineering Laboratory
26 W. Martin Luther King Drive
Cincinnati, OH 45268
(513) 569-7856 -u.S. Government Printing Office: 1994— 650-067/80267
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-94/507
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