*************************************************************
 VITRIFICATION

This profile provides the following general information about
vitrification:
     
     1.   Description
     2.   Applicability
     3.   Limitations
     4.   Availability and vendor list
     5.   Performance data and field applications
     6.   Sources of information for this profile




1.   Description

Two forms of vitrification are currently available: in-situ
vitrification (ISV) and ex-situ vitrification (ESV).   

> IN SITU VITRIFICATION
In situ vitrification (ISV) uses an electric current to melt soil
or other earthen materials at extremely high temperatures (1,600
to 2,000 ¿C or 2,900 to 3,650 ¿F) and thereby immobilize most
inorganics and destroy organic pollutants by pyrolysis.  Inorganic
pollutants are incorporated within the vitrified glass and
crystalline mass.  Water vapor and organic pyrolysis combustion
products are captured in a hood, which draws the contaminants into
an off-gas treatment system that removes particulates and other
pollutants from the gas.

High temperatures are achieved using a square array of four
graphite electrodes.  To initiate the process, a path of
conducting material (graphite) is placed on the surface of the
soil so that current can flow in the soil beyond the boiling
temperature of water (dry soil is not conductive after the
conduction path in soil pore water is boiled off) to the melting
point of the soil.  The joule heating of the starter path achieves
temperatures high enough to melt the soil (value is dependent on
the soil"s alkali metal oxide content), at which point the soil
becomes conductive.  The molten soil zone grows downward and
outward.  New designs incorporate a moving electrode mechanism to
achieve a greater process depth.  A vacuum pressurized hood is
placed over the vitrification zone to contain and process any
contaminants emanating from the soil during vitrification.  The
vitrification product is a chemically stable, leach-resistant,
glass and crystalline material similar to obsidian or basalt rock. 
The process destroys and/or removes organic materials. 
Radionuclides and heavy metals are retained within the molten
soil.


> EX SITU VITRIFICATION
Ex situ vitrification encapsulates inorganic contaminants and
destroys organic contaminants, as does ISV.  The principal
differences are that the soil is treated in an above-ground
reactor, and the treated material is in the form of pellets or
sand, rather that a glass-like block.

Ex situ vitrification is effective in reducing the mobility of the
contaminated wastes within the media.  The vitrified mass has high
strength and resistance to leaching.  The strength properties of
material vitrified by different systems can vary widely.  Systems
in which the vitrified mass is quench-cooled may produce a more
easily fractured mass than systems in which the mass is allowed to
air cool.  Systems in which fluxing agents are used will also have
different strength properties.  The composition of the soil that
is vitrified may also affect the strength properties of the
vitrified material.

Ex situ vitrification is normally considered a standalone
technology; however, its potential for use in treating the solid
residuals from other technologies, such as incinerator ash, is
receiving increasing attention.




2.   APPLICABILITY

The in situ process can destroy or remove organics and immobilize
most inorganics in contaminated soils, sludges, or other earthen
materials.  The process has been tested on a broad range of VOCs
and SVOCs, other organics including dioxins and PCBs, and on most
priority pollutant metals and radionuclides.

Ex situ vitrification is applicable to the full range of
contaminant groups, but inorganics is the target contaminant
group.  Metals, radionuclides, etc. are encapsulated in the
vitrified mass, resisting leaching for geologic time periods



3.   LIMITATIONS

Factors that may limit the applicability and effectiveness of the
in-situ process include:

     Rubble exceeding 20% by weight.

     Heating the soil may cause subsurface migration of
     contaminants into clean areas.

     Combustible organics in the soil or sludge exceeding 5 to 10
     weight percent (wt%), depending on the heating value.

     The solidified material may hinder future site use.

     Processing of contamination below the water table may require
     some means to limit recharge

Factors that may limit the applicability and effectiveness of the
ex-situ process include:

     Organic off-gases need to be controlled.  Some volatile heavy
     metal and radioactive contaminants may volatilize and require
     treatment in the off-gas system.

     Use or disposal of the resultant vitrified slag is required.




4.   AVAILABILITY AND VENDOR LIST

In-situ vitrification is commercially available from one vendor, 

Geosafe Corporation                          509-375-0710  

The ISV process was invented by Battelle, Pacific Northwest
Laboratory for DOE in 1980.  The patent is assigned to DOE, is
licensed to Battelle, and is sublicensed to Geosafe Corporation
for worldwide rights (Patent No. 4,376,598, issued 15 March 1983).

Ex-situ vitrification vendors include:

B&W Nuclear Environmental Services           804-948-4610
Battelle Pacific Northwest Laboratories      509-376-6576
Bio-Electrics                                816-474-4895
EET Corporation                              615-671-7800
Electro-Pyrolysis                            610-687-9070
EM&C Engineering                             714-957-6429
Geosafe Corporation                          509-375-0710
Retech Inc.                                  707-762-6522
Stir-Melter Inc.                             419-536-8828
Texaco Syngas Inc.                           914-253-4003
Vortec Corporation                           610-489-2255



5.   PERFORMANCE DATA

The ISV process has been operated for test and demonstration purposes
at the pilot scale and at full scale at the following sites:  (1)
Geosafe Corporation's test site, (2) DOE's Hanford Nuclear
Reservation, (3) DOE's Oak Ridge National Laboratory, and (4)
DOE's Idaho National Engineering Laboratory.  More than 170 tests
at various scales have been performed on a broad range of waste
types in soils and sludges.  A SITE demonstration took place at
the Parsons/ETM site in Grand Ledge, Michigan.  A demonstration 
on PCB-bearing waste was performed at a General Electric site in 
Spokane Washington in support of a National TSCA treatment permit; 
the results are not yet final, and the permit has not yet been awarded.  
Geosafe is preparing for implementation of ISV at the Wasatch Chemical 
Superfund site in Utah.

Process depths up to 6 meters (19 ft) have been achieved in
relatively homogeneous soils.  The achievable depth is limited
under certain heterogeneous conditions.

An EPA SITE program demonstration of plasma arc vitrification was
conducted in 1991 at DOE"s Component Development and Integration
facility in Butte, Montana.  During the demonstration, the furnace
processed approximately 1,820 kilograms (4,000 pounds) of waste. 
The waste consisted of soil with heavy metals from the Silver Bow
Creek Superfund site, spiked with 28,000-ppm zinc oxide and 
1,000-ppm hexachlorobenzene and mixed in a 90-to-10 weight ratio with
No. 2 diesel oil.

DOE is currently developing a full-scale prototype of a fixed
hearth DC plasma torch process that will convert full drums of
waste materials directly to an enhanced waste form in a one step
process.  An arc melter vitrification process exists but requires
engineering development. 



6.   Source:

Marks, Peter J., Walter J. Wujcik and Amy F. Loncar, October 1994.
REMEDIATION TECHNOLOGIES SCREENING MATRIX AND REFERENCE GUIDE,
SECOND EDITION.  DOD Environmental Technology Transfer Committee.
NTIS No. PB95-104782.  Reproduced for the Bloomington, Indiana PCB
Superfund Sites Bulletin Board with the permission of USAEC, 
SFIM-AEC-ETD, APG, MD.  Supplmented by MVA Consulting, Inc.
*******************************************************************************