United States
Environmental Protection
Agency
EPA/540/S-97/501
August 1997
&EPA
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Emerging Technology Summary
Vitrification of Soils Contaminated by
Hazardous and/or Radioactive Wastes
A performance summary of an ad-
vanced multifuel-capable combustion
and melting system (CMS) for the vitri-
fication of hazardous wastes is pre-
sented. Vortec Corporation has
evaluated its patented CMS for use in
the remediation of soils contaminated
with heavy metals and radionuclides
under the EPA's SITE program and
other waste treatment technology evalu-
ation programs. The Vortec CMS has
successfully demonstrated the ability
to effectively treat hazardous and/or ra-
dioactive soils and produce a stable
vitrified product with excellent leach
resistance. The ability to process con-
taminated soils either as dry granular
solids or in the form of a slurry has
been demonstrated with a ORE of
greater than 99.99% for organic com-
pounds. All the glass produced passed
the TCLP test with the concentration of
contaminants in the leachates signifi-
cantly reduced from those of the corre-
sponding feedstocks which did not
pass TCLP. The vitrified product also
demonstrated superior radionuclide
leach resistance, as no detectable quan-
tities of the surrogate radionuclide were
found by an ANSI/ANS-16.1 test.
This Summary was developed by the
National Risk Management Research
Laboratory's Sustainable Technology
Division, Cincinnati, OH, to announce
key findings of the SITE Emerging Tech-
nology program that is fully docu-
mented in a separate report (see Project
Report ordering information at back).
Introduction
Vortec Corporation has developed an
advanced multifuel-capable combustion
and melting system (CMS) for the vitrifica-
tion of hazardous wastes. Vortec has
evaluated the CMS for the remediation of
soils contaminated with heavy metals un-
der the EPA's SITE Programs, and for the
remediation of soils contaminated with
heavy metals, organic compounds, and
radionuclides under other waste treatment
technology evaluation programs.
The soil remediation programs focused
on demonstrating the ability of the Vortec
CMS to immobilize heavy metals and ra-
dionuclides by incorporating these con-
taminants into the matrix of a glassthe
vitrified product. The glass is formed by
the vitrification of the soil which contains
the hazardous constituents. Depending
upon the composition of the contaminated
soil, the addition of inexpensive glass-forming
agents may be required. The Vortec CMS
produces a vitrified product which has
long-term stability, reduces the teachabil-
ity of the heavy metals (and radionuclides)
below regulatory limits, and results in a
volume reduction of the waste material. In
the vitrification of contaminated soils that
are hazardous by characteristic and do
not contain radionuclides, the vitrified prod
uct would no longer be classified as a
hazardous waste. The Vortec CMS also
completely oxidizes any organic compo-
nents (hazardous or not) in the waste.
The Vortec CMS has demonstrated a de-
struction removal efficiency (ORE) greater
than 99.99% for all organic compounds in
the soil.
The unique features of the CMS make
it particularly suitable for the rapid and
efficient heating of fine granular materials,
and subsequent vitrification into a glass
product. A process diagram of the Vortec
CMS-based soil vitrification system is
shown in Figure I.
The basic components of the system
include:
the Vortec multifuel-capable CMS,
consisting of a counter-rotating vortex
combustor and a cyclone melter;
an upstream storage and feeding sub-
system;
a separator/reservoir assembly;
AWBERG LIBRARY U.S.
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DATE DUE
Fuel Oil
or Water
Wet
Grinding
Crusher
Dryer/
Grinder
Dry Soil
Bin
Transport
Air
Gla
Agitator
Tank
Glass-Forming
Additives
Figure 1. Vortec's CMS-based contaminated soil vitrificatic
-r"
Stack
ID
Fan
Recycled to
CMS System
Vitrified
Product
Storage
The Library Store #47-0106
a cullet handling subsystem;
a heat recoverysubsystem;
a flue gas conditioning assembly; and
an air pollution control subsystem.
Except for the CMS and the separator/
reservoir, all other subsystems or assem-
blies are commercially available or modi-
fied versions of commercially available
equipment.
The basic CMS can be modified to ac-
commodate the use of a variety of fuels,
including pulverized coal, coal slurry fu-
els, natural gas, oil, waste oils, and waste
solvents. The CMS is also capable of us-
ing any combination of these fuels. Natu-
ral gas is customarily used in
demonstration testing because of its con-
venience.
Complete combustion and in-flight sus-
pension preheating of the contaminated
soils, and any glass-forming additives,
takes place in the combustor. The feed-
stock ingredients are introduced into the
combustor through an injector and are
rapidly heated in the flame zone. Any
carbon-based materials are rapidly volatil-
ized and oxidized. The inert materials are
heated to nominally 230OF to 280OF,
depending on the characteristics of the
soil, prior to entering the cyclone melter.
Since combustion air is preheated to nomi-
nally 100OF to 140OF, high local flame
temperatures of more than 400OF can be
achieved in the combustor. However, due
to the rapid temperature quenching of the
combustion products by the inert soil par-
ticles and the staged combustion inherent
in the CMS design, the NOx emissions
have been demonstrated in pilot scale test-
ing to be lower than DOE's boiler emis-
sions standard of 0.6 Ibs NOx/MMBtu. NOx
emissions lower than 2 Ibs NOx/ton glass
have also been demonstrated.
The preheated solid materials from the
combustor enter the cyclone melter, where
they are distributed to the chamber walls
by the cyclone action of the combustion
products, thus forming a molten layer of
vitrified soil (glass). The glass and the
combustion products exit the cyclone
melter through a tangential exit channel
and enter the separator/reservoir. The
separator/reservoir separates the combus-
tion products from the molten glass and
provides additional residence time for the
completion of glass-forming reactions. The
glass exits the separator/reservoir through
either a tap hole in the floor or an over-
flow weir along a side wall. The combus-
tion products exit through an exhaust port,
which discharges into a conventional
radiation-type recuperator for combustion
air preheating.
A flue gas conditioning assembly re-
duces the temperature of the flue gas
exiting the radiation recuperator to satisfy
the temperature requirements of particu-
late control devices. Commercially avail-
able paniculate control devices are incor-
porated into the design as dictated by
local environmental regulations. A high ef-
ficiency venturi scrubber can be used for
particulate control in some applications.
Wet or dry electrostatic precipitators
(ESPs) or baghouses can be used to
achieve higher levels of particulate emis-
sions control. Additional air pollution con-
trol, such as acid gas scrubbers, may be
easily incorporated if required.
Two different techniques for transport-
ing the contaminated soil into the CMS
have been investigated. In one feed sys-
tem, the soil was pneumatically fed to the
CMS as dry granular solids. However,
many soils found at contaminated sites
are not in this preferred (dry) form. There-
fore, a second feed system was devel-
oped to handle wet soils in the form of a
slurry. The slurry feed system provides a
means of mixing the wet contaminated
soil and a liquid (water), and then deliver-
ing and atomizing this slurry into the CMS.
By processing wet soils in a slurry form,
the preparation and blending of the wet
soil and the glass-forming materials, as
well as the introduction of the resulting
mixture into the CMS, are simplified. The
Vortec CMS process demonstrated its abil-
ity to process both the dry and slurried
feed materials, while forming a fully-reacted
vitrified product.
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Procedure
Laboratory melts were conducted by
Vortec on EPA's Synthetic Soil Matrix
(SSM) to determine whether the addition
of glass-forming agents is required to pro-
duce a vitrified product that will consis-
tently pass the Toxic Characteristic
Leaching Procedure (TCLP). Table 1 pre-
sents the composition of EPA's SSM and
the resulting feedstock formulation used
in Vortec's SITE testing. Vortec, in coop-
eration with DuPont Chemicals, estab-
lished the types and quantities of heavy
metal compounds (shown later in Table 2)
that were used to produce the contami-
nated surrogate soil. Blending of the sur-
rogate soil, limestone and the heavy metal
compounds was performed just prior to
the initiation of testing, thus minimizing
the possibility of further contamination in
the feedstock.
The Vortec SITE program has con-
ducted two tests at Vortec's nominal 15-20
tons per day pilot facility using surrogate
soil spiked with heavy metal compounds.
The first test employed the pneumatic feed
system to process dry feedstock, while
the second test used the slurry feed sys-
tem to process an aqueous slurry contain-
ing contaminated surrogate soil. Prior to
the slurry feed test, an initial combustion
stability test was successfully completed
and demonstrated the ability of the com-
bustor to accept the designated water flow
rate of 400 pounds per hour. Additional
combustion stability testing was performed
using a slurry of 60% cullet (ground waste
glass) and 40% water. Cullet was used as
the sole constituent, rather than clean soil,
to avoid contamination of the materials
being used in concurrent testing. The sta-
bility testing using the cullet/water slurry
was also successful and verified the slurry
system design parameters. Finally, a slurry
containing 60% contaminated surrogate
soil/limestone mixture and 40% water was
used to perform the second of Vortec's
contaminated soil SITE tests. Sampling
and chemical analyses of the influent and
effluent streams from both pilot scale con-
taminated soil tests were performed by
DuPont's Water Quality Laboratory, Cham-
bers Works, NJ; and Geraghty and Miller,
Inc., Pittsburgh, PA. Under other demon-
stration programs, the feedstocks con-
sisted of different SSMs, glass-forming
additives, surrogate heavy metal com-
pounds, organic compounds, and surro-
gate radionuclides.
Results and Discussion
The tests conducted under the EPA
SITE Program, as well as all tests per-
formed under other demonstration pro-
grams, have satisfied all technical and
data quality objectives. Table 2 presents
the metal concentrations in the feedstocks
and the vitrified products produced during
the Vortec SITE tests. Table 2 also in-
cludes the results of the TCLP tests per-
formed on the feedstocks and the vitrified
products. Due to the high cadmium con-
tent in the dry feedstock leachate and the
high cadmium and lead content in the
slurried feedstock leachate, both feed-
stocks failed TCLP testing. Therefore,
these feedstocks would be considered haz-
ardous if classified as waste products.
However, all of the glass produced during
Vortec's testing passed TCLP testing, with
the concentration of heavy metals in the
leachates significantly reduced from those
of the corresponding feedstocks. The el-
evated chromium content in the vitrified
products is due to the leaching of this
element from the refractory present in the
CMS during the SITE testing. Under other
demonstration programs, the vitrified prod-
uct was also evaluated by the ANSI/
ANS-16.1 test for the leachability of the
surrogate radionuclide.
No detectable quantities of the surro-
gate radionuclide were found in any of the
leachates collected during the ANSI/
ANS-16.1 test procedures.
Table 3 presents system mass balances
and emission data for the Vortec SITE
tests. The production of carbon dioxide,
Table 1. EPA's Synthetic Soil Matrix (SSM) and the Feedstock Compositions used during Vortec's
SITE Program
SSM
Si02
A1203
K20
Na20
CaO
Fe203
MgO
Other oxides
Composition
wt%
57.43
11.74
1.55
0.84
20.26
2.32
5.29
0.57
Feedstock
SSM
Limestone
Water
Dry feed test
wt%
80.0
20.0
0.0
Slurry feed test
wt%
48.0
12.0
40.0
water vapor and the volatilization of other
materials present in the feedstock resulted
in the loss on ignition displayed in the
table. Both uncontrolled and controlled
stack particulate loadings are presented.
During the SITE testing, a venturi scrub-
ber was used as the pollution control de-
vice in the CMS exhaust system. A wet
ESP has since been placed in the sys-
tem, and based on subsequent testing of
a variety of materials, the anticipated emis-
sions under the conditions that existed
during the SITE tests would be lower than
0.003 gr/dscf.
As the contaminated soils are processed
within the CMS, the metal contaminants
partition to either the carryover stream or
the glass stream. The volatility of the met-
als and their oxides is the primary factor
controlling the partitioning of these con-
taminants. The non-volatile metals, chro-
mium, copper, and nickel, are found
primarily in the vitrified product, while the
semi-volatile metals, cadmium and lead,
have a significantly higher percentage par-
titioning to the carryover. Table 4 summa-
rizes the partitioning of the metal
contaminants among all the effluent
streams from the Vortec CMS. Through
the use of a high efficiency particulate
removal system, such as an ESP (wet or
dry) or a baghouse, the carryover can be
effectively recycled back into the molten
vitrified product within the CMS using a
proprietary technology developed by
Vortec. With the implementation of this
particulate-carryover recycle technology,
the Vortec CMS has the potential to be-
come a zero waste discharge process.
While the recycling of the particulate
carry-over into the vitrified product was
not performed during Vortec's SITE test-
ing, other programs are currently demon-
strating this carryover recycle feature.
Conclusions and
Recommendations
Pilot scale vitrification testing has dem-
onstrated that, with the addition of appro-
priate glass-forming additives, surrogate
soils representative of EPA Superfund and
other hazardous waste sites can be effec-
tively vitrified by the Vortec CMS. A high
capture rate of the heavy metal contami-
nants into the glass product is achievable
with the glass consistently passing the
TCLP testing requirements for the leach-
ing of RCRA metals. The CMS has dem-
onstrated DREs greater than 99.99% for
organic compounds. In addition, the CMS
has demonstrated the ability to effectively
process surrogate soil in both wet and dry
forms. With the implementation of a pro-
prietary particulate recycling technology,
the Vortec CMS-based contaminated soil
vitrification system can become a zero
waste discharge process.
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Table 2. Summary of Contaminant Concentrations and TCLP Data for the Feedstocks used and the Vitrified Products Collected under Vortec's SITE
'rogram
Metal
Contaminants
Concentration
in Feedstock
Feedstock
TCLP Result
Concentration
in Glass
Glass
TCLP Result
TCLP
RCRA Limit
Dry Feed Test
PPMa
PPM"
PPMC
PPM"
PPM
Arsenic
Cadmium
Chromium
Copper
Lead
Nickel
Zinc
Slurry Feed Test
(dry basis)
Arsenic
Cadmium
Chromium**
Copper
Lead
Nickel
Zinc
273
187
867
395
2132
128
2395
PPM
112
116
546
235
1106
85
1300
0.97
1.55
0.02
0.06
0.10
1.73
8.71
PPM
1.1
2.7
0.04
3.7
7.5
3.5
26.3
259
75
1615
366
872
189
1615
PPM
275
27
1209
381
505
229
1506
0.00
0.00
0.04
0.04
0.00
0.00
0.12
PPM
0.0
0.008
0.19
0.15
0.13
0.15
0.83
5.
1.0
5.0
N/
5.0
N/
N/
PPM
5.0
1.
5.0
N/A
5.0
N/A
N/A
a Average of 13 samples.
b Average of 19 samples.
c Average of 11 samples.
d Average of 18 samples.
N/A - not applicable.
** Excess levels of chromium leached from refractory into glass.
Table 3. CMS Performance During Vortec's SITE Program Testing
Mass Dry feed test
Slurry feed test
Feedstock
Glass produced
Loss on ignition
Ibs/hr
Ibs/hr
Ibs/hr
947
721
195
450
212
235
Emissions data
Uncontrolled particulate
Controlled particulate using
venturi scrubber
Controlled particulate
estimate using wet ESP
% of Feedstock
% of Feedstock
grains/dscf
3.3
0.3
<0.003
0.06
0.01
<0.001
Table 4. Partitioning of Heavy Metals among the CMS Effluent Streams During Vortec's SITE Program
Dry feed test
Slurry feed test
Metal
Arsenic
Cadmium
Chromium
Copper
ead
.'Jickel
Zinc
Glass
69.9
50.9
89.4
85.4
44.7
87.5
78.0
Scrubber
27.3
24.6
9.8
12.5
31.6
12.2
16.6
Stack gas
2.8
24.5
0.8
2.1
23.7
0.3
5.4
Glass
91.0
41.2
85.5
96.0
52.7
98.5
92.7
Scrubber
5.4
16.3
11.4
2.2
23.5
0.0
3.7
Stack gas
3.6
42.5
3.1
1.8
23.8
1.5
3.6
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James G. Hnat Is with Vortec Corporation, Collegeville, PA 19426.
Ten Richardson is the EPA Project Officer (see below).
Details of the completed SITE Emerging Technology project are given in an article
published in Glass Production Technology International, 1994 pp. 103-106.
The EPA Project Officer can be contacted at:
Sustainable Technology Division
National Risk Managemet Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection Agency
Center for Environmental Research Information (G-72)
Cincinnati, OH 45268
Official Business
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