United States
Environmental Protection
EPA/540/MR-97/506
August 1997
vvEPA
540MR97506
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Demonstration Bulletin
Cold Top Ex-Situ Vitrification Process
Geotech Development Corporation
Technology Description: The Geotech Development Corpora-
tion Cold Top Vitrification technology is an ex-situ, submerged-
electrode, resistance-melting technology designed to convert
contaminated soil into an essentially monolithic, vitrified mass.
AccorHinn to Geotech, a development engineering firm holding
four patents in the field of applied electrical power, vitrification
transforms the physical state of contaminated soil from assorted,
crystalline matrices into a glassy, amorphous solid comprising
interlaced polymeric chains that typically consist of alternating
oxygen and silicon atoms. Geotech claims that chromium can
substitute for silicon in these chains, rendering the chromium
immobile to leaching by aqueous solvents and, therefore, non-
toxic.
For the past 15 years, Geotech has operated a pilot plant that
has vitrified a wide variety of materials, including granite, blast
furnace slag, fly ash, spent catalyst, and flue dust. Several
production plants based on the Geotech technology are now
being used to produce mineral fiber and other commercial prod-
ucts. The heart of the system is an electric resistance furnace
capable of operating at melting temperatures of up to 5,200 °F
(2,870 °C). The furnace is cooled by water circulating within its
hollow jacket and is equipped with an off-gas treatment system,
which may include a baghouse, cyclone, and wet scrubbers,
dopsnding on waste characteristics.
A schematic diagram of the Cold Top Vitrification system used
during the SITE demonstration is shown in Figure 1. The furnace
is initially charged with a mixture of sand and alumina/silica clay.
Through electrical resistance heating, a molten pool forms; the
voltage to the furnace is properly adjusted; and, finally, contami-
nated soil is fed into the furnace by a screw conveyor. Geotech
removes the furnace plug from below the molten product tap
when the desired soil melt temperature is achieved. As the soil
melts, additional soil is added to maintain a "cold top." During the
demonstration test, the outflow was poured into refractory-lined
and insulated molds for slow cooling. Excess material was dis-
charged to a water sluice for immediate cooling and collection
before off-site disposal.
To air pollution
control system
Pretreated
contaminated
soil
Molten product tap
Mold containing
vitrified product
Figure 1. Cold Top Vitrification System schematic.
SM-X1
Printed on Recycled Paper
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Waste Applicability: According to Geotech, the Cold Top Vitrifi-
cation process has been used to treat soils contaminated with
hazardous heavy metals such as lead, cadmium, and chromium;
asbestos and asbestos-containing materials; and municipal solid
waste combustor ash residue. Waste material must be sized to
pass through a 1- to 1.5-inch mesh screen. The Cold Top Vitrifica-
tion process is most efficient when feed materials have been
dewatered to less than 10% water and organic chemical concen-
trations have been minimized.
Wastes similar to those treated during the demonstration may
require the addition of carbon and sand to ensure that the vitrifica-
tion process produces a glass-like product. According to Geotech,
in the molten state, inorganic contaminants fuse with the silica to
become an integral part of the fused material. The vitrified product
from the Cold Top process is designed to cool slowly to form a
high-density, noncrystaliine glass with physical properties suitable
for commercial use. Geotech claims that the vitrified product has
many uses, including shore erosion blocks, decorative tiles, road-
bed fill, and cement or blacktop aggregate, and that radioactive
wactes car; ts treated with thic technology.
Demonstration Procedures: Key participants in the planning and
execution of the Cold Top demonstration included the Geotech
Development Corporation, New Jersey Institute of Technology
(NJIT), New Jersey Department of Environmental Protection
(NJDEP), and the U.S. EPA SITE Program. Additional support
was provided by the New York State Department of Environmen-
tal Conservation (NYSDEC) and Stevens Institute of Technology.
Demonstration tests were performed on soils from two sites,
representing residue from two types of chromite-ore processing.
The sites were selected by NJDEP under an ongoing program to
clean up over 150 hexavalent-chromium-contaminated sites. Ex-
cavated soils from Liberty State Park and Site 130 were crushed,
sieved, dried, and amended with carbon and sand at a facility in
New Jersey. "Supersacs" containing the pretreated material were
then shipped to the Geotech facility in Niagara Falls, NY, where
demonstration runs were conducted on February 1 and March 11,
1997. The SITE team collected samples of untreated soil, offgas
generated during treatment, and baghouse dust. Cooled castings
were transported to NJIT, where samples were crushed and
ground for chemical analyses. Chemical analyses were performed
in triplicate by NJIT and by SITE-contracted laboratories.
Demonstration Results and Conclusions: The primary objec-
tive of the SITE demonstration was to determine if the waste and
products produced bv the Cold Top Vitrification system meet the
Resource Conservation and Recovery Act (RCRA) definition of a
characteristic hazardous waste because of their chromium con-
tent. The Toxicity Characteristic Leaching Procedure (TCLP) was
performed on both treated product and untreated waste to meet
this objective.
Secondary objectives of the demonstration were as follows:
1) evaluate the partitioning of total chromium from the waste feecJ
into the various waste and product streams; 2) determine if the
vitrified product meets NJDEP criteria for fill material, such as
road construction aggregate; 3) determine if process air emissions
meet NYSDEC compliance requirements; 4) determine the uncon-
trolled air emissions of oxides of nitrogen, sulfur dioxide, and
carbon monoxide; and 5) determine costs for treating the type of
waste treated during the demonstration.
A summary of preliminary SITE analytical results appears below:
Liberty State Park
Total Cr TCLP Cr
(mg/kg) (mg/L)
Feed soil (dried) 6,900 29
Vitrified product 1 0,000 1 .0
Site 130
Total Cr TCLP Cr
(my/kg) (rng/'L)
5,100 58
5,500 0.31
These results indicate that the vitrified product is not a character-
istic hazardous waste according to the RCRA definition. Field
observations and measurements made during the demonstration
indicate that several operational issues must be addressed during
technology scale-up. First, a consistent and controlled feed sys-
tem needs to be developed that spreads the waste feed uniformly
over the surface of the molten soil. This feed system must also
minimize dust generation. Second, an emission control system
needs to be configured to control any particulate and gaseous
emissions from the furnace and feed system.
A Technology Capsule and an Innovative Technology Evaluation
Report will be available in late 1997.
For Further Information:
Marta K. Richards
U.S. EPA SITE Project Manager
26 West Martin Luther King Drive
Cincinnati, OH 45268
(513) 569-7692; fax (513) 569-7676
Email: richards.marta@epamail.epa.gov
United States
Environmental Protection Agency
Center for Environmental Research Information
Cincinnati, OH 45268
Official Business
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EPA
PERMIT No. G-35
EPA/540/MR-97/506
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