v°/EPA
United States
Environmental Protection
Agency
EPA/540/S5-91/007
August 1992
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Technology Demonstration
Summary
Technology Evaluation Report;
SITE Program Demonstration
Test; Retech, Inc. Plasma
Centrifugal Furnace; Butte, MT
A demonstration of the Retech, Inc.
pilot-scale Plasma Centrifugal Furnace
(PCF-6) has been performed under the
Superfund Innovative Technology
(SITE) Program. The demonstration oc-
curred in July 1991 at the U.S. Depart-
ment of Energy's (DOE's) Component
Development and Integration Facility
(CDIF) in Butte, MT. The PCF is de-
signed to treat hazardous material
contaminated with both inorganic
(metal) and organic constituents by us-
ing the heat generated from a plasma
torch to melt metal-bearing solids and,
in the process, thermally destroying
organic contaminants.
During the Demonstration Tests, the
PCF-6 treated a waste matrix consist-
ing of soil from the Silver Bow Creek
Superfund Site and 10% by weight No.
2 diesel oil. The Demonstration Test
results indicate that the PCF can bind
inorganic compounds into the treated
soil (a nonleachable monolith). Testing
activities also demonstrated that the
process can effectively destroy the or-
ganic compounds tested, achieving at
least a 99.99% Destruction and Removal
Efficiency (DRE).
The air emissions generated during
the Demonstration Tests contained only
low levels of volatile and semivolatile
organic compounds. However, metals
(in the solid phase) were present in
abundance in the stack gas and the
paniculate emissions during each of
the three tests exceeded the RCRA
regulatory limit of 0.08 grains/dscf.
The post-test scrubber liquor did not
contain any significant quantities of or-
ganic compounds. The lack of organic
compounds in the scrubber liquor and,
as stated above, the absence of
volatiles or semivolatiles in the exhaust
gas, indicates that combustion of the
organic compounds was complete. The
scrubbing unit was very inefficient in
the capture of particulates and inor-
ganic compounds.
The cost of this remediation technol-
ogy is high because of the capital cost
of the equipment and the labor require-
ments. The cost per ton for this tech-
nology is very dependent on the feed
rate of the contaminant to the furnace.
This summary was developed by
EPA's Risk Reduction Engineering
Laboratory, Cincinnati, OH, to announce
key findings of the SITE Program dem-
Printed on Recycled Paper
-------
anatratlon that Is fully documented in
two separate reports (see ordering in-
formation at back).
Introduction
In response to the Superfund Amend-
ments and Reauthorization Act of 1986
(SARA), the U.S. Environmental Protec-
tion Agency's (EPA's) Offices of Research
and Development (ORD) and Solid Waste
and Emergency Response (OSWER) have
established a formal program to acceler-
ate the development, demonstration, and
use of new or innovative technologies as
alternatives to current containment sys-
tems for hazardous wastes. This new
program is called Superfund Innovative
Technology Evaluation or SITE.
The major objective of the SITE Pro-
gram is to develop reliable performance
and cost information for innovative tech-
nologies. One technology, which was
demonstrated in July 1991 at DOE's CDIF
in Butte, MT, was the Retech, Inc. Plasma
Centrifugal Furnace. The Retech system
Is comprised of a thermal treatment system
and an exhaust gas treatment system,
shown conceptually in Figure 1. The PCF
uses heat generated from a plasma torch
to melt and vitrify solid feed material. Metal-
bearing solids are bound into a monolithic
nonleachable mass. Organic components
are vaporized and decomposed by the
intense heat of the plasma and are oxi-
dized by the air used as the plasma gas,
before passing to the off-gas treatment
system.
The waste matrix utilized during this
demonstration was a mixture of heavy
metal-bearing soil and diesel oil spiked
with both a metal and an organic com-
pound to ensure traceability. Three Dem-
onstration Tests were performed to evalu-
ate the effectiveness of the Plasma Cen-
trifugal Furnace in treating this waste ma-
trix and to evaluate the feasibility of em-
ploying similar units at hazardous waste
treatment facilities throughout the country.
To facilitate this evaluation, the following
objectives were established:
• To evaluate the ability of the fur-
nace to effectively vitrify inorganic
and metal constituents within a soil
into a monolithic nonleachable
mass. (Zinc oxide was spiked into
the soil at a level of 28,000 ppm.)
• To evaluate the ability of the Plasma
Centrifugal Furnace to meet 99.99%
destruction and removal efficiency
(DRE) for the target analytes in a
soil contaminated with up to 10%
organics. (Hexachlorobenzene was
spiked into the feed soil at 1,000
ppm so that a DRE of 99.99% could
be easily calculated. DREs for other
target analytes were determined if
these compounds were present at
high enough levels in the feed soil.)
Specific critical and noncritical objec-
tives may be found in the Demonstration
Plan [1]. In addition to allowing an evalua-
tion of the technology for potential Super-
fund applications, the activities and re-
sults of this testing wijl also provide as-
sistance to DOE in their evaluation of the
technology for the remediation of hazard-
ous waste sites under their jurisdiction.
Procedure
A total of 1,440 Ib of the spiked soil
were treated during the three Demonstra-
tion Tests. For each test, samples of the
feed soil, the treated soil, the scrubber
liquor, and the stack emissions were col-
lected to evaluate the performance of the
technology. Samples were collected and
analyzed in accordance with the Demon-
stration Plan with only minor changes in
some of the sampling and analytical
methods. Analyses included volatile and
semivolatile organic compounds, dioxins/
furans, metals, and particulate matter. Both
the test soil and the treated soil were
subjected to the Toxicity Characteristic
Leaching Procedure (TCLP) and analyzed
for semivolatiles and metals.
Process operations were continuously
observed by operators and their supervi-
sors. Process measurements were re-
corded manually or electronically by the
data acquisition system (DAS). Important
process information was also calculated
by the DAS.
To aid in striking the arc, approximately
100 Ib of mild steel in the form of a 1 -in.
Bulk Feeder
• Oxygen Lance
Plasma Torch
Oxygen Jets
Afterburner
Secondary Chamber
Collection Chambe,
Primary Chamber
Copper Throat Jet Scrubber
Exhaust Gas
Treatment System
Vent to
Atmosphere
Scrubber Sump
Figure 1. Conceptual Design of Plasma Centrifugal Furnace.
-------
thick "doughnut" were placed inside the
primary combustion chamber. The torch
was struck after a final check of the pro-
cess equipment. Before material could be
fed into the furnace, operating procedures
require that the primary chamber tem-
perature must be at least 2,100 °F and
the afterburner temperature 1,800 °F.
Three to five hours of operating time were
necessary to achieve these temperatures.
The torch arc was struck on the copper
throat or the mild steel doughnut,_bqth
centrally located at the bottom of the spin-
ning furnace. This area was the first loca-
tion to be preheated. After the material
adjacent to the copper throat was heated
to the conducting temperature, the torch
was moved slowly to heat and melt more
of the soil of the bottom of the furnace
and eventually the sidewall. This was
continued until the entire contents of the
primary chamber were melted by the torch.
Following the preheat period, the test
soil was fed into the furnace in a semi-
batch manner. Approximately 120 Ib of
the soil were manually loaded into the
feeder at a time and fed into the furnace
at a uniform rate. Once fed into the fur-
nace, treatment of the waste material with
the plasma torch was initiated. It took ap-
proximately one hour to melt each feeder
load. After each feeder load was melted,
the feeding process was repeated until a
maximum of 1,000 Ib were fed to the
furnace.
The waste material was brought to tem-
peratures sufficient to melt soil. The melt-
ing point for typical soil is on the order of
3,000 °F. Volatile components were va-
porized and decomposed by the heat of
the plasma, and were oxidized by the air
used as the plasma gas. To combust any
products of incomplete combustion (PICs)
that were formed, a natural gas afterburner
was employed just downstream of the pri-
mary chamber.
After the last desired charge was melted,
the afterburner was extinguished, the fur-
nace spin rate was slowed to allow the
molten pool to move inward and the melted
soil to pour out of the bottom of the fur-
nace, into the secondary chamber. The
organics that were volatilized and oxidized
were drawn off to the exhaust gas treat-
ment system.
The molten mass fell from the second-
ary chamber, through the collection cham-
ber, and into a heavy pig mold. The pour-
ing process took 5 to 10 min for a 600-lb
pig. The molten mass solidified into a hard
monolith which was then disposed of in
an appropriate landfill or otherwise utilized.
Results and Discussion
TCLP analysis of the feed soil for met-
als showed that the only elements which
exhibited significant teachability charac-
teristics were calcium, sodium, and the
spiked zinc. Table 1 summarizes the re-
sults of the TCLP metals analysis of the
feed soil. None of the eight RCRA charac-
teristic metals found in the feed soil
leachate were above their regulatory lim-
its, therefore, the evaluation of the leach-
ability of the vitrified slag was based on
calcium, which leached at an estimated
average of 180 ppm, and zinc, which
leached at an estimated average of 980
ppm. (Sodium was not used because of
its unusual solubility properties.)
The treated soil TCLP metals analysis
is also shown in Table 1. None of the
metals, with the exception of sodium,
showed any strong characteristic for
leaching. Both tracer metals, calcium and
zinc, showed significant reductions in
leaching properties in the treated soil as
compared to the feed. In fact, all of the
metals, with the exception of aluminum
and iron showed reduced leaching char-
acteristics. It is quite possible that the
teachability for the aluminum did not
change since the values obtained for both
the test soil and the treated soil are only
estimates (see Table 1). The increase in
teachability of iron in the treated soil was
probably because of the mild steel placed
in the furnace to aid in initiating the strik-
ing of the torch arc.
Table 1. TCLP Results for Demonstration Tests
The only organic constituents that were
found to be teachable from the feed soil
were 2-methylnaphthalene and naphtha-
lene, as shown in Table 1. Although the
feed soil was spiked with high levels of
hexachlorobenzene (1,000 ppm), it did not
leach from the soil. No organic compounds
were found to leach from the treated slag.
The Destruction and Removal Efficiency
(ORE), used to determine organic de-
struction, was determined by analyzing for
the Principal Organic Hazardous Com-
pound (POHC), hexachlorobenzene, in the
feed soil and the stack gas. No hexachloro-
benzene was detected in the stack gas,
therefore, all DREs determined are based
on the detection limit from the appropriate
tests. Table 2 gives these DREs based on
the 95% confidence interval of the feed
soil and the detection limit for the POHC
in the stack gas for each test.
As can be seen from Table 2, the esti-
mated average ORE values for these tests
ranged from >99.9968% to >99.9999%
for a highly chlorinated compound (hexa-
chlorobenzene). It can be reasonably as-
sumed that this level of DRE (if measur-
able) can be achieved for most chlori-
nated or halogenated compounds.
Analysis of the feed soil indicated that
sufficient 2-methylnaphthalene, another
semivolatile compound, was present at
high enough levels in the feed to deter-
mine a significant DRE for each test. This
level of contamination in the feed soil leads
to the DREs given in Table 2, again based
Treated Soil Leachate Concentration
fivoietyv roou &uti
Compound Leachate Concentration Test 1
(mg/L) (mg/L)
Metals:
Aluminum
Barium
Cadmium
Calcium
Copper
Iron
Magnesium
Manganese
Nickel
Potassium
Sodium
Vanadium
Zinc
Semivolatiles:
Hexachlorobenzene
2-Methylnapthalene
Napthalene
0.23 J
0.14
0.067
180
4.6
0.063
8.1
4.8
0.022
4.6
1,500
0.099
980
<0.0010
0.28
0.40
0.45 J
0.078
<0.039
2.1 J
0.15
2.5
<0.039
0.057
<0.011
<0.70
1,500
<0.0043
0.45
<0.0010
<0.0019
<0.0026
Test2
(mg/L)
0.42 J
0.085
<0.039
2.6 J
0.36
3.0
<0.039
0.061
0.010 J
<0.70
1,400
<0.043
0.36
<0.0010
<0.0019
<0.0026
Tests
(mg/L)
0.32 J
0.075
<0.039
2.0 J
0.30
31.2
<0.039
0.24
0.11
<0.70
1,400
<0.043
0.3
<0.0010
<0.0019
<0.0026
J Estimated result. Indicates that the result is less than the quantitation limit. The quantitation
limit is defined as 5 times the instrument detection limit.
< Indicates that this constituent was not detected at or above the detection limit.
-------
Table 2, ORE Results for Demonstration Tests
Compound
Testl
Testl
Duplicate
Test2
Tests
Hsxachhrobenzene
Lower95% Conf.lnt. >99.9964 >99,9982 >99.9990 >99.99989
Mean >99.9968 >99.9984 >99.9991 >99.99990
Upper95% Conf. Int. >99.9971 >99.9986 >99.9992 >99.99991
2-Mathylnapthalono
Lower95% Conf.Int. >99.9853 >99.9930 >99.9958 >99.9996O
Mean >99.9872 >99.9939 >99.9964 >99,99965
Upper 95% Conf.lnt. >99.9891 >99.9948 >99.9969 >99.99970
on detection limits, as none of this com-
pound was detected in the stack gas.
Total xylenes, a group of volatile com-
pounds, were also found in sufficient
quantities In the feed soil to determine a
significant ORE. Over all three tests, the
ORE range for xylenes was >99.9929% to
>99.9934%. These DREs are an average
over all three tests based on the 95%
confidence interval of xylenes in the feed
soil and the detection limit for xylenes in
the stack gas.
Overall, the PCF-6 appeared to be very
efficient in destroying both volatile and
semivolatiie compounds when both the
primary reaction chamber and the after-
burner were operating.
Measured HCI emission rates ranged
from 0.0007 to 0.0017 Ib/hr. Because of
the low chlorine input, the regulatory re-
quirement of <4 Ib/hr was met.
As shown in Table 3, the particulate
emissions during each of the three tests
exceeded the RCRA regulatory limit of
0.08 grains/dscf. Hazardous waste incin-
erators operating under conditions of oxy-
gen enrichment (such as the Retech PCF)
are exempt from the RCRA requirement
to correct emissions to 7% O2. Therefore,
these emission rates have not been cor-
rected of 7% oxygen. If the correction was
to be applied only during the feeding cycle
(when presumably the particulates were
being generated) then the values given in
Table 3 should be increased by a factor of
1.4.
Table 3. Particulate Results for
Demonstration Tests
Testl Testl Test2 Tests
Duplicate
Particulate
Concentration 0.341 0.240 0.422 0.470
(grains/dscf)
Paniculate
Emissions 0.342 0.238 0.418 0.423
(Ib/hr)
The air emissions consisted primarily of
particulates and low levels of products of
incomplete combustion (PICs). Table 4
presents a summary of the semivolatiie
organic compounds emitted in the stack
gas. Very low levels of volatile organic
compounds were also detected in the ex-
haust gas stream.
Sampling and analysis for polychloro-
dibenzodioxins (PCDDs) and polychloro-
dibenzofurans (PCDFs) in the exhaust gas
stream were accomplished during the
Demonstration Tests. The results of these
analyses indicate that no PCDDs or PC-
DFs were formed in the stack gas. Al-
though some PCDDs and PCDFs were
detected in some of the samples analyzed,
the levels detected were less than the
corresponding blank sample detection limit.
Metal emissions were almost exclusively
in the solid phase. Table 4 summarizes
these results. The only significant vapor
phase metals found were calcium and
mercury. A very volatile metal such as
mercury is expected to be found in the
vapor phase. Arsenic, copper, iron, lead,
potassium, and zinc were in abundance in
the stack gas in the solid phase. It ap-
pears that not all of the volatile metals
were captured in the molten soil at the
completion of treatment. If this is the case,
then these volatile metals should have
been captured by the gas treatment sys-
tem (assuming it is correctly designed).
Analysis of the feed soil showed that it
contained volatile compounds consistent
with those associated with diesel fuel:
benzene, toluene, ethyl benzene, and xy-
lene (BTEX). These compounds were de-
tected in the quantities presented in Table
5. The semivolatiie compounds found most
predominantly in the feed soil were the
spiked hexachlorobenzene and 2-methyl-
naphthalene (see Table 5). As shown in
Table 6, the metals found most abun-
dantly in the feed soil were aluminum,
calcium, iron, potassium, sodium, and zinc.
Volatile organic analysis was not per-
formed on the treated soil as no volatile
compounds were considered to exist in
the slag after it had reached its melting
point temperature. The only semivolatiie
organic compounds found in the treated
soil were low levels of two phthalate com-
pounds which were probably sampling or
analytical contaminants. This agrees with
the TCLP analysis of the slag discussed
earlier in which no semivolatiie compounds
leached from the slag.
A mass balance that yields meaningful
results cannot be performed on this tech-
nology since a portion of material from
each test can possibly remain in the fur-
nace at the end of treatment. It is pos-
sible, though to compare the concentra-
tion of the inorganic elements in the feed
soil with that of the collected slag, taking
into account the destruction of the 10%
organics and assuming that none of the
elements are concentrated in the poured
slag. Table 6 gives the concentrations of
the metals in feed and in the slag for all
three of the tests. The feed is an average
of all feed samples from the three tests.
This table shows that a large percentage
of the metals from the feed soil are re-
tained within the vitrified slag. For ex-
ample, for Test 3, 88% of the aluminum
originally present in the feed soil was de-
tected in the treated soil. Exceptions to
this trend are generally the volatile metals:
arsenic, lead, mercury, and zinc. During
Test 3, only 38% of the zinc from the feed
soil was retained in the treated soil. These
volatile metals have been found, as stated
earlier, to be exiting the system through
the exhaust stack or plating out on the
walls of the extensive exhaust system. In
addition, some of these metals can be
found in the scrubber liquor.
Only the treated soil (not the feed soil)
was analyzed for PCDDs and PCDFs dur-
ing the Demonstration Tests. The levels
of PCDDs and PCDFs in the treated soil
were very low. However, as described
earlier for stack gas emissions, the detec-
tion limits for blank samples are higher
than the amount of PCDDs and PCDFs
detected in the samples. It is therefore
reasonable to conclude that no PCDDs or
PCDFs were formed by the treatment pro-
cess, and if any dioxins/furans were in the
feed, they were destroyed by the intense
heat of the process.
The pre-test scrubber liquor for each of
the three Demonstration Tests contained
very little in the way of organic compounds.
A metals scan on the pre-test scrubber
liquor showed that, generally, only low
levels of inorganic elements were present.
The post-test scrubber liquor did not con-
tain any significant quantities of organic
compounds. The lack of organic com-
pounds in the scrubber liquor and, as
-------
Table 4. Stack Gas Composition During Demonstration Tests
Testl
lb/100lb
feed
ppm
Test2
lb/100lb
feed
ppm
Tests
lb/100 Ib
feed
ppm
Semivolatiles:
Acetaophenone <2.15E-06 <0.38
Benzole Acid 3.77E-04 6.7
Benzyl Alcohol <4.9SE-07 <0.0099
Butylbenzylphthalate <3.28E-07 <0.0023
Dibutylphthalate <9.93E-07 B <0.0077 B
Diethlyphthalate <5.41E-05 B <0.70 B
2,4-Dinitrophenol 2.13E-O5 J 0.25 J
bis(2-Ethlyhexyl)phthalate 7.36E-OS B 0.41 B
Naphthalene 1.68E-05 B 0.26 B
Nitrobenzene <3.13E-07 J <0.0055 J
2-Nitrophenol <8.56E-06 J <0.13 J
4-Nitrophenol 1.15E-05 J 0.18 J
4.63E-06
3.29E-04
<1.65E-07
<1.09E-07
4.48E-06
2.54E-05
1.27E-OS
5. QBE-OS
8.96E-06
2.84E-06
2.09E-06
<1.43E-05
J
JB
B
J
B
B
J
J
0.71
4.9
<0.0033
<0.00079
0.030
0.28
0.13
0.24
0.12
0.042
0.028
<0.22
J
JB
B
J
B
B
J
J
2.30E-O6
1.98E-04
3.76E-07
3.76E-07
1.15E-06
2.50E-OS
5.74E-06
4.69E-06
1.1SE-05
1.56E-06
1.36E-05
1.01E-05
J
J
B
B
B
B
0.031
2.6
0.0056
0.0056
0.0067
0.24
0.050
0.019
0.134
0.021
0.16
0.12
B Indicates that this compound was detected in a blank.
J Estimated result. Indicates that result is less than the quantitation limit. Quantitation limit is five times the instrument detection limit.
< Not detected at or above the detection limit.
stated earlier, the absence of volatile or
semivolatiles organic compounds in the
exhaust gas, indicates that combustion of
the organic compounds was complete.
The scrubbing unit was very inefficient
in the capture of the inorganic compounds.
There was less than 0.5% total solids in
the scrubber sump tank. The scrubber did
capture some of the volatile metal ele-
ments but not at the levels that would
typically be expected from a well-designed
system. As stated previously, the exhaust
gas contained a variety of metals that
should have been captured by the scrub-
bing unit. The types of metals found in the
scrubber liquor were similar to those found
in the stack gas; that is, arsenic, iron, and
zinc were the elements in abundance. High
sodium levels found in the liquor were a
consequence of the scrubber make-up
(sodium hydroxide).
Throughout each of the three tests, CO,
CO O2, NOX, and Total Hydrocarbons
(THC) were monitored continuously to
present a real time image of the combus-
tion process and to determine if regula-
tory standards were being exceeded. The
low flowrate of the stack gas (110 scfm)
prevented these emissions from ap-
proaching regulatory limits. During the
Demonstration Tests, the THC exiting the
system was low (<4 ppm), even with 10%,
or more, organics in the feed. The ex-
haust gas contained low levels of CO (ap-
proximately 1.4 ppm) and a level of ap-
proximately 8% CO2. These levels of THC,
CO, and CO., gave a good indication that
effective thermal destruction of the organic
compounds occurred. However, the levels
of NOX were consistently high throughout
each of the three tests.
Table 5. Organic Compounds in the
Demonstration Test Soil
J
J
B
B
B
B
Metals:
Aluminum
Antimony
Arsenic
Barium
Beryllium
Cadmium
Calcium
Chromium
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Nickel
Potassium
Selenium
Silver
Sodium
Thallium
Vanadium
Zinc
5.02E-04
1. 18E-05
1.88E-03
4.26E-05
1.63E-07
1.76E-05
8.41 E-04
3.39E-04
1.63E-03
1.51E-02
9.28E-04
2.01E-04
1. 14E-04
1.38E-06
6.65E-05
3.76E-03
5.02E-06
2.88E-06
2.26E-03
5.52E-06
2.76E-05
3.01E-02
B
B
B
B
B
B
B
B
B
B
B
B
B
1.34
0.031
5.02
0.114
0.001
0.047
2.51
0.904
4.35
40.2
2.48
0.535
0.305
0.004
0.177
10.0
0.013
0.008
6.02
0.015
0.074
80.3
B
B
B
B
B
B
B
B
B
B
B
B
B
9.56E-04
4. 16E-05
2.98E-03
8.09E-05
3.58E-07
3.99E-05 .
1.74E-03
6.57E-04
4.71 E-03
3.01E-02
2.29E-03
3.26E-04
2.48E-04
2.92E-06
1.10E-04
7. 11 E-03
1.11E-05
6.32E-06
4.26E-03
1.35E-05
6.57E-05
8.36E-02
B
B
B
B
B
B
B
B
B
B
B
B
B
B
2.10
0.091
6.54
0.177
0.001
0.088
3.81
1.44
10.3
66.1
5.02
0.716
0.544
0.006
0.372
15.6
0.024
0.014
9.35
0.030
0.144
183
B
B
B
B
B
B
B
B
B
B
B
B
B
B
5.67E-04
2.62E-05
2.47E-03
6.11E-05
2.91E-07
2.76E-05
9.60E-04
7.27E-04
2.04E-03
4.51E-02
1.60E-03
2.47E-04
3.20E-O4
5.09E-06
1.74E-04
6.69E-03
6.40E-06
4.65E-06
3.78E-03
1.25E-05
4.51E-05
5.53E-02
B
B
B
B
B
B
B
B
B
B
B
B
B
B
1.14
0.053
4.97
0.123
0.001
• 0.056
1.93
1.46
4.09
90.6
3.21
0.497
0.643
0.010
0.351
13.4
0.013
0.009
7.56
0.025
0.091
111
B
B
B
B
B
B
B
B
B
B
B
B
B
B
Compound
Volatiles*:
Benzene
Ethyl Benzene
Toluene
Xylene
lb/100 Ib
feed
9.91E-05
2.84E-03
1.81E-03
1.34E-02
ppm
0.991
28.4
18.1
134
Semivolatiles":
Hexachlorobenzene 9.72E-05 972
2-Methylnaphthalene 4.58E-05 458
Naphthalene 1.52E-02 150
Phenanthrene 6.62E-03 66.2
* • 1,2-Dichloroethane and methyl ethyl
ketone were both detected in a few
samples, but only at low levels.
" Other compounds were detected in.a few
samples, but only at low levels.
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Table 6. Metals in the Demonstration Tsst Feed Soil and Treated Soil
Element
Aluminum
Arsenic
Barium
Calcium
Chromium
Copper
Iron
Lead
Magnesium
Manganese
Mercury
Nickel
Potassium
Sodium
Vanadium
Zinc
Average
Feed Soil
(ppm)
49,400 B
201
508
12,500
23.6 J
591
36,900 B
426
4,650
814
1.00
NA
19,360
10,200
77.3 J
23,200
Testl
(ppm)
51,200
12.0 J
523
28,800
500
780
160,000
98.3 J
5,720
1,850
<0.133
270
15,500
8,180 B
59.8 J
6,480
Treated Soil
Test2
(ppm)
46,000
16.0 J
480
20,500
510
1,500
150,000
115 J
4,600
1,900
<0.133
265
16,000
8,650
159.5 J
9,050
Test 3
(ppm)
43,700
11.3
453
18,000
617
827
213,333
120
4,670
2,570
<0.133
287
14,700
7,830
50.0
8,800
J
*
J
B Indicates that this compound was detected in a blank
J m Estimated result. Indicates that tfre result is less than the quantitation limit. The quantitation
limit Is defined as 5 times the instrument detection limit.
NA~ Not analyzed
Since all three Demonstration Tests
were designed to be identical in nature,
operating conditions during the tests were
relatively constant. Although the mass of
material to be fed during each test was
anticipated to be 960 Ib, the actual weight
of the feed was 480, 360, and 600 Ib for
Tests 1, 2, and 3, respectively. The cor-
responding weight of the treated soil gen-
erated during the tests was 277, 265, and
595 Ib.
The torch power ranged from an aver-
age of approximately 410 kW during Test
3 to nearly 460 kW during Tests 1 and 2.
The total power consumption of the torch
ranged from 3,308 kWh (Test 1) to 4,720
kWh (Test 3). The torch gas in each case
was air with a flowrate of 23 to 24 scfm.
Excess oxygen was supplied from an oxy-
gen lance at a rate of approximately 1 Ib/
min.
The reactor chamber temperature, once
it stabilized, achieved an average value of
approximately 2,250 °F. The afterburner
temperature averaged around 1,800 °F
(slightly higher during Test 3) once the
system reached operating range.
The scrubber liquor generated during
each of Tests 1 and 2 was close to 150
gal. During Test 3, this value was greatly
exceeded due to frequent blowdowns of
the scrubber in an attempt to reduce par-
ticulate loading on the blower downstream.
Nearly 800 gal of scrubber liquor were
generated during Test 3.
Conclusions
Based on the Demonstration Tests, a
number of conclusions regarding the Re-
tech Plasma Centrifugal Furnace may be
drawn. The conclusions are presented
below:
• The PCF is an innovative technol-
ogy used to process media con-
taminated with both organic and
inorganic regulated compounds
which became non-leachable after
treatment.
• The Destruction and Removal Effi-
ciency (ORE) of organic compounds
tested was greater than 99.99%.
• Particulate emissions from the
treatment process used during the
Demonstration Tests exceeded the
RCRA regulatory limit of 0.08
grains/dscf.
• NOX concentrations in the stack gas
were high, averaging 4,800 ppm
(uncorrected to 7% oxygen); how-
ever, emission rates were within
regulatory limits because of the low
flowrates.
• A high percentage of the metals
from the feed soil were captured
and retained in the vitreous slag. A '
proportion of the more volatile met-
als evolved from the feed and
passed through the furnace and the
gas scrubbing system.
• The scrubber was not effective in
capturing the volatile metal ele-
ments.
• The PCF-6 is not mobile. Retech
estimates that approximately 2 mo
are required to install, erect, and
shakedown all equipment prior to
operation of the system.
• The furnace, as configured, must
be erected within an enclosed fa-
cility. Onsite requirements include
adequate power supply, cooling
water, and cranes for lifting.
• The Plasma Centrifugal Furnace
was effective for treating soils con-
taminated with both metal and or-
ganic compounds. However, the
projected cost of this remediation
technology is high because of the
capital cost of the equipment and
the labor requirements. The cost
per ton for this technology is very
dependent on the feed rate of the
contaminant to the furnace. For a
feed rate of 500 Ib/hr and an on-
line factor of 70%, the cost is
$1,816Aon; for 2,200 Ib/hr (70% on-
line factor) the cost becomes $757/
ton.
References
1. Science Applications International Cor-
poration. July 11, 1991. "Demonstration
Plan for Centrifugal Plasma Furnace
Technology."
•U.S. Government Printing Office: 1992 — 648-080/60056
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-------
The EPA Project Manager, LaurelJ. Staley, is with the Risk Reduction
Engineering Laboratory, Cincinnati, OH 45268 (see below)
The complete report, entitled "Technology Evaluation Report of Retech's
Plasma Centrifugal Furnace," consists of two volumes:
"Volume I" (Order No. PB92-2W 035-V1; Cost: $26.00, subject to change)
discusses the results of the demonstration.
"Volume II", (Order No. PB92-216 043-V2; Cost: $43.00, subject to change)
contains the appendices.
Both volumes of this report will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
Telephone: 703-487-4650
A related report, entitled "Applications Analysis Report: Retech, Inc., Plasma
Centrifugal Furnace," discusses the applications of the demonstrated tech-
nology.
The EPA Project Manager can be contacted at:
Risk Reduction Engineering Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
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/S5-91/007
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