xvEPA
United States
Environmental Protection
Agency
EPA/540/MR-93/502
February 1993
SUPERFUND INNOVATIVE
TECHNOLOGY EVALUATION
Demonstration Bulletin
X*Trax™ Model 200 Thermal Desorption System
Chemical Waste Management, Inc.
Technology Description: The X*TRAX™ Mode! 200 Thermal
Desorption System developed by Chemical Waste Management,
Inc. (CWM), is a low-temperature process designed to separate
organic contaminants from soils, sludges, and other solid media.
The X*TRAX™ Model 200 is fully transportable and consists of
three semitrailers, one control room trailer, eight equipment skids,
and various pieces of movable equipment. The equipment re-
quires an area of about 125 ft by 145 ft. The system is shown in
Figure 1 and is described below.
The X*TRAX™ system is a thermal and physical separation pro-
cess; it does not involve incineration. Contaminated solids are
fed into an externally heated rotary dryer where temperatures
range from 750 to 950 °F. Evaporated contaminants are removed
by a ^circulating nitrogen carrier gas that is maintained at less
than 4% oxygen to prevent combustion. Solids leaving the dryer
are sprayed with treated cooling water to help reduce dusting
when the treated solids are returned to their original location and
compacted in place. The nitrogen carrier gas is treated to remove
and recover dust particles, organic vapors, and water vapors.
An ecluctor scrubber removes dust particles and 10% to 30% of
the organic contaminants from the carrier gas. Scrubber liquid
collects in a phase separator from which sludge and organic
liquid phases are pumped to a filter press, producing filter cake
and filtrate. The filtrate is then separated into organic liquid and
water phases. Most contaminants removed from the feed solids
are transferred to the organic liquids or the filter cake. The filter
Propane
Supply
Contaminated
Solids
4
^
•• w
i r~~
T *
XTrax™
Dryer
l^
Dry ^
Solids ~
-Carrier Gas -7
Product
Cooler
t '
Carrier Gas
*(r
'mating
'reated ^
Solids ^
Cooling Water
Makeup
Water
^f
^
fe
Scrub.
Liqui
^
Organic
Liquid
Filt
Eductor
Scrubber
ter
d
1
r
Scrubber
Phase
Separator
V 1
Filter
Press
-ate
1
*
r
r
Filtrate
Tank
/ .
/
'
/
^
W
\
w
Sludge
' \
•\
r
r Organic 1\
i Liquid J)
Conde
1
Conde
Phi
Sepa
i
Condensate
r
nsate
tS8 . I
rator %
;-4A
/Onsite /
Water /
'reatment/ ,
1
r
jj Excess A j
j
<_
A
Activated
Canister
- Condensec
Water
*
Activated
Carbon
+
/*" "\
f Vent ^
A-GasJ/
X7™'~" ' ' ' S
]
Key
Liquid Flow
—— Solids Flow
Gas Flow
C3 Input
O Output
Figure 7. Diagram of XTrax system.
Printed on Recycled Paper
-------
cake Is typically blended batchwise with feed solids and repro-
cessed In the X*TRAX™ system, while the concentrated organic
liquids are typically treated or disposed of offsite.
Carrier gas exiting the scrubber passes through two condensers
In series, where it is cooled to less than 40°F. The condensers
separate most of the remaining water and organic vapors from the
gas stream. Organic vapors are recovered as organic liquids;
water is treated by carbon adsorption and either used to cool and
reduce dusting from treated solids, or treated and discharged.
About 5% to 10% of the gas exits the system through a process
vent, passing through a particle filter and carbon adsorption sys-
tem before being discharged to the atmosphere. The volume of
gas released by the X*TRAX™ system is about 100 to 200 times
tess than the amount released by an equivalent capacity incinera-
tor.
Wast© Applicability: CWM reports that the XTRAX™ system
can process a wide variety of solids at feed rates up to 7.5 tons
per hour (tph). The technology is most effective for solids with a
moisture content of less than 50%. Screening of material greater
than 2.25 In. In size may be required for some applications.
Bench-, pilot-, and full-scale X*TRAX™ systems have been used
to treat solids contaminated with the following wastes: polychlori-
nated blphenyls (RGB); halogenated and nonhalogenated sol-
vents; semivolatile organic compounds (SVOC); polynuclear aro-
matic hydrocarbons; pesticides; herbicides; fuel oils; benzene,
toluene, ethylbenzene, and xylenes (BTEX); and mercury. The
X*TRAX™ system has also treated Resource Conservation and
Recovery Act (RCRA) hazardous wastes to meet Land Disposal
Restrictions (LDR) treatment standards. RCRA wastes treated by
X*TRAX™ include petroleum refinery wastes (K048 through K052)
and multlsource leachate treatment residues (F039).
Demonstration Results: The X*TRAX™ SITE demonstration
was conducted In May 1992, after a proof-of-process test at the
Re-Solve Superfund Site In North Dartmouth, MA. The system is
being used to treat approximately 35,000 tons of soil and sedi-
ment contaminated with PCBs at the site. For this application, the
soil te screened to remove particles larger than 1 in. in size.
During the SITE demonstration, about 215 tons of soil were
treated at an average feed rate of 4.9 tph, a residence time of 2
hr, and an average treated soil temperature of 732°F. PCS con-
centrations in contaminated soil ranged from 181 to 515 milli-
grams per kilogram (mg/kg). Average flow rates for the carrier gas
and process vent gas were 700 and 37 actual cubic feet per
minute (acfm), respectively.
The demonstration included three identical tests, each lasting (3
hr. During each test, solid, liquid, and gas samples were col-
lected from feed soil, treated soil, filter cake, filter press filtrate,
condensed aqueous liquids, water used to wet treated soil, and
process vent gases before and after activated carbon treatment.
Condensed organic liquids were collected before the start of the
first test and after completion of the third test. Extensive analyses
were performed under rigid quality assurance procedures. Key
findings from the XTRAX™ SITE demonstration are summarized
below:
• X*TRAX™successfully removed PCBs from feed soil and met
the site-specific treatment standard of 25 milligrams per kilo-
gram (mg/kg) for treated soils. PCB concentrations in all
treated soil samples were less than 1.0 mg/kg and the average
concentration was 0.25 mg/kg. The average PCB removal
efficiency was 99.9%.
• Polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated
dibenzofurans (PCDF) were not formed within the X*TRAX™
system.
• Organic air emissions from the X*TRAX™ process vent were
negligible (0.4 grams/day). PCBs were not detected in vent
gases.
• X*TRAX™ effectively removed other organic contaminants
from feed soil. Concentrations of tetrachloroethene, total re-
coverable petroleum hydrocarbons, and oil and grease were all
reduced to below detectable levels in treated soil.
• Metals concentrations and soil physical properties were not
altered by the X*TRAX™ system.
For-Further Information:
EPA Project Manager:
Paul R. dePercin
U.S. EPA Risk Reduction Engineering Laboratory
26 West Martin Luther King Drive
Cincinnati, OH 45268
(513) 569-7797; FAX (513) 569-7620
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/MR-93/502
------- |