United States
Environmental Protection
Agency
EPA/540/MR-94/504
March 1994
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION I
Demonstration Bulletin
The ECO Logic Thermal - Desorption Unit
Middleground Landfill -Bay City, Ml - ELI ECO Logic International, Inc.
Technology Description: ECO Logic has developed a ther-
mal desorption unit 0"DU) for the treatment of soils contaminated
with hazardous organic contaminants. This TDU has been de-
signed to be used in conjunction with Eco Logic's patented gas-
phase chemical reduction reactor. The Eco Logic reactor is the
subject of an independent SITE Demonstration (see SITE Bulle-
tin: EPA/540/MR-93/522, September 1993).
The TDU (see Figure 1) consists of an externally-heated bath of
molten tin metal, blanketed in a hydrogen gas atmosphere. Eco
Logic offers several reasons for using tin: tin and hydrogen are
nonreactive; tin's density allows soils to float on the surface of the
molten bath; tin's low vapor pressure prevents evaporation of the
tin into the hydrogen; molten tin is a good fluid for heat transfer;
tin is non-toxic as a soil contaminant; and tin has been used as a
bath medium in the manufacture of plate glass for many years.
Contaminated soil is conveyed into a hopper where an auger
feeds the soil into the TDU. The screw feeder provides a gas seal
between the outside air and the hydrogen atmosphere inside the
TDU. The auger's variable speed drive provides feedrate control.
Soil inside the TDU floats on top of the molten tin and is heated
to 600°C, vaporizing the water and organic material. Decontami-
nated soil is removed from the tin bath into a water-filled quench
tank, the water in the quench tank provides a gas seal between
the TDU's hydrogen atmosphere and the outside air. A scraper
mechsinism removes desorbed soil from the quench tank into
drums!
After desorption from the soil, the organic contaminants are
swept into the companion reactor where they undergo gas-phase
reduction reactions with the hydrogen at elevated temperatures.
This gas-phase reduction reaction takes place within Eco Logic's
specially-designed reactor: a cylindrical vessel with a hollow
ceramic tube and electric glo-bar heaters. The reactor operates
in a Hydrogen atmosphere. Desorbed organics from the TDU
enter the reactor and swirl between the reactor's side wall and
the ceramic tube. By the time the mixture enters the central tube,
it has been heated to at least 850°C. The reduction reactions
take place as the gas travels up the central tube to the scrubber.
The scrubber removes hydrogen chloride, heat, water, and fine
particiilate matter from the gas stream. When processing low
organic wastes, approximately 95% of the hydrogen-rich gas
recirculates back into the reactor, while the remaining 5% is used
as supplementary fuel for the system's propane-fired boiler. Pro-
Site
Soils —'L
H2 _j_
Propane
Air
ench
\ Tank \
TDU
Figure 1. ECO logic thermal - desorption unit shown with reactor.
Sludge and Decant
Water Slowdown
Clean Steam
Stack Gas
f Boiler
REACTOR SYSTEM
Hydrocarbon
Gas (5%)
Printed on Recycled Paper
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cesstng waste streams with a high organic content produces
much more excess gas, which can be compressed, stored, and
analyzed before use as a supplementary fuel.
The TDU can be transported on a single, standard flatbed trailer.
Tha companion reactor, scrubber, boiler, and auxiliary equipment
are mounted on two standard, drop-deck highway trailers.
Waste Applicability: The TDU, when coupled
panfon reactor, Is suitable for many wastes includir
I with it's corn-
including polychlori-
hated blphenyls (PCBs), poiycyclic aromatic hydrocarbons (PAHs),
chlorinated dioxins and dibenzofurans, chlorinated solvents,
chforbenzenos, and chtorophenols. The TDU is designed to treat
most soli and sludge wastes, including those with a high water
content.
Demonstration Results: The U.S. ERA'S Superfund Inno-
vative Technology Evaluation (SITE) Program, in cooperation with
Environment Canada, the Ontario Ministry of the Environment,
and the City of Bay City sponsored a demonstration of the Eco
Logic TDU In conjunction with the Eco Logic reactor system at the
Middloground Landfill in Bay City, Michigan during November and
December 1992. Previous tests of the reactor system conducted
during October 1992 demonstrated 99.9999% destruction and
removal efficiency on PCB-contaminated water (approximately
4000 ppm PCBs) and oil (24.5% PCBs).
The TDU test plan called for three analytical test runs on soils
excavated from the landfill. The soils contained approximately
1000 ppm PCBs. Tests were conducted under a TSCA R&D
permit. Run 1, hampered by shakedown and materials handling
problems, caused Eco Logic to make modifications to the system
prior to Run 2. Run 2 was conducted with a reduced feed through-
put in order to increase soil residence time on the tin bath to
adequately heat clumps of soil that formed in the system. Run 3
was cancelled due to TSCA permit time constraints.
The demonstration achieved the following:
• PCB destruction and removal efficiencies (DREs) for the TDU
and reactor system combined were 99.9999% for Run 1. Run
2 results were impacted by sampling and analytical problems.
• PCB concentrations in the cleaned soil ranged between 8 and
30 ppm.
• Destruction efficiencies (DEs) for hexachlorobenzene (added
as a surrogate waste) ranged from 72% for Run 1 to 99.99% for
Run 2.
• Throughput was 180 Ib/hr for Run 1 and 55 Ib/hr for Run 2.
Eco Logic plans to modify the materials handling capabilities of
the TDU to eliminate clump formation and increase throughput.
The final report will address other test results, including an
analysis of process inputs, intermediates, and outputs. System
reliability, mass balances, costs, and safety will also be ad-
dressed.
For Further Information Contact:
SITE Project Manager:
Gordon M. Evans
U.S. EPA
Risk Reduction Engineering Laboratory
26 W. Martin L. King Dr.
Cincinnati, OH 45268
(513)-569-7684
•U.S. Government Printing Office: 1994— 550-067/80235
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«40/MR-94/5Q4
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