&EPA
                                  United States
                                  Environmental Protection
                                  Agency
                                         EPA/540/MR-92/019
                                         September 1992
                                  SUPERFUND INNOVATIVE
                                  TECHNOLOGY EVALUATION
                                     Demonstration  Bulletin

                     Low Temperature Thermal Treatment (LT3®)System

                                             Roy F. Weston, Inc.
Technology Description: The Roy F. Weston, Inc. (Weston) low
temperature thermal treatment (LT3®) system thermally desorbs
organic compounds from contaminated soil without heating the
soil to combustion temperatures. The transportable  system is
comprised  of equipment assembled on three flat-bed  trailers.
With ancillary and support equipment, the system requires  an
area of about 5,000 sq ft. It was demonstrated under the SITE
program at the Anderson Development Company (ADC) site in
Adrian, Ml,  which was contaminated with volatile and semivolatile
organic compounds (VOC and SVOC), and 4,4'-methylenebis  (2-
chloroaniline) (MBOCA). The LT3® system is divided into three
main areas of treatment: soil treatment, emissions control, and
water treatment. The system is shown in Figure 1 and described
below.

The LT3® thermal processor consists of two jacketed troughs,
one above the other.  Each trough houses four  intermeshed
screw conveyors. A front-end  loader  transports feed  soil  (or
sludge) to a weigh scale and deposits the material onto a con-
veyor that discharges into a surge feed hopper located above the
                        thermal  processor. The surge hopper is equipped with level
                        sensors and provides a seal over the thermal processor to mini-
                        mize air infiltration and contaminant loss. Soil moves across the
                        upper trough, drops to the second trough, and exits the proces-
                        sor at the same end that it entered. Heat transfer fluid (or hot oil)
                        circulates through the  hollow screws and trough jackets. Thus,
                        each screw conveyor  mixes, conveys,  and  heats the contami-
                        nated soil during treatment. Soil is discharged from  the thermal
                        processor into a conditioner, where water is sprayed onto it for
                        cooling and to minimize fugitive dust emissions. An inclined belt
                        conveys the treated soil to a truck or pile.

                        A burner heats the oil to an operating temperature of 400 to 650
                        °F (about 100°F higher than desired soil temperature). Combus-
                        tion gases released from the burner are used as sweep gas in
                        the thermal processor. A fan draws  sweep gas and desorbed
                        organics from the thermal processor through a fabric filter bag-
                        house. Depending on contaminant characteristics, dust collected
                        on  the fabric  filter may  be retreated, combined  with treated
                        material, or drummed separately for offsite disposaL Exhaust gas
       Oversized
       material or
       wastewater
                      Feed
                     conveyor
Dust
                Aqueous Flow
            — Vapor Flow
Figure 1. Diagram of LT3® system.

                                                	Sweep_gas_	f   Hot oj, bumer off.gases
                                                                             Fuel/combustion air

Surge
hopper


I *
t*.
'o
•5
<§
Thermal
processo


-h
Hot oil
system

Conditioner
conveyor
Fabric filter
baghouse
                                               To atmosphere
                                                             Off-gases
Air-cooled
condenser


Oil/water
separator
                                                                  | Organics
                               To offsite
                               disposal
                                              To discharge or
                                              offsite disposal

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from the fabric filter is drawn  into an air-cooled condenser to
remove most of the water vapor and organics, and then through a
second, refrigerated condenser to further lower the temperature
and reduce the moisture  and organic content of the off-gases.
Electric resistance heaters then increase the off-gas temperature
back to 70°F to optimize the performance of the vapor-phase
activated carbon column which removes any remaining organics.
While this is a typical operation, caustic scrubbers and afterburn-
ers have been employed as part of the air pollution control system
at some sites.

Condensate streams are  typically  treated in  a three-phase oil-
water separator to  remove light and heavy organic phases from
the water phase that is then treated in the  carbon  adsorption
system to remove  residual organic contaminants. Treated con-
densate is often used for soil conditioning, and only the  organic
phases are disposed offsite.  However, the separation step may
not be appropriate when processing extremely wet materials like
sludge, due to the high volume of condensate generated.  In such
cases, aqueous streams from both condensers may be pumped
through a disposable filter to remove particulate matter  prior to the
carbon adsorption treatment and offsite disposal.

Waste Applicability: Weston reports that the  LP® system can
process a wide variety of soils with differing  moisture and con-
taminant concentrations, and that the technology is best suited for
soils with a moisture content of less than 20% and VOC contami-
nant concentration  of up  to  1%. Wastes with moisture  content
greater than 50% need to be dewatered prior to treatment in the
UP® system. Screening or crushing of oversized material (greater
than 2 in.), or clay  shredding may be required for some applica-
tions.

Bench-, pilot-, or full-scale LP® systems have been used to treat
soil contaminated with the following wastes: coal tar, drill cuttings
(oil-based mud), No. 2 diesel fuel, JP4 jet  fuel, leaded and
unleaded gasoline,  petroleum  hydrocarbons,  halogenated and
nonhatogenated solvents, VOCs, SVOCs, and polynuclear aromatic
hydrocarbons.

Demonstration Results: The LP®  SITE demonstration was
conducted in November and December 1991, as part  of a proof-
of-process test for full-scale remediation of the ADC lagoon sludge.
Feed preparation for the sludge at the ADC site included lime and
ferric chloride addition followed  by filter press dewatering to  a
moisture content of 14% to 44%. During the demonstration, con-
taminated sludge was heated to  above 500°F for a residence
time of 90 min; the system throughput was approximately 2.1
tons/hr.

Six replicate tests were conducted, each lasting approximately 6
hr.  Solid  and liquid sampling locations for each test  included
contaminated  feed sludge, treated sludge, fabric filter dust, and
condensate liquid. Off-gases were also sampled before and after
carbon treatment during each run. Solid, liquid, and gas samples
were analyzed for MBOCA, VOCs, SVOCs,  dioxins, and furans.
Samples were also analyzed for chloride and total organic halides,
to trace the fate of chloride through the system, and a variety of
other parameters were analyzed  to characterize the feed  and
treated sludge. Continuous emissions monitoring (GEM) of off-
gases included  total hydrocarbons (THC), carbon  monoxide,
carbon dioxide, and oxygen. Key findings from the SITE demon-
stration are summarized below:

  • The LP® system removed VOCs to below method detection
    limits (less than 0.060 milligrams per kilogram [mg/kg] for
    most compounds).
  • The  LP® system  achieved  MBOCA removal efficiencies
    greater than 88%; concentrations in the treated sludge ranged
    from  3.0 to 9.6 mg/kg.
  • The LP® system decreased the concentrations of all SVOCs
    in the sludge, with two exceptions. The increase in phenol
    concentration is most likely due to chemical transformations
    during heating.  A minor leak of heat transfer fluid,  which
    contains triphenylene, probably caused the apparent increase
    in chrysene concentration.
  • Dioxins and furans were formed  in the  system, but the
    2,3,7,8-TCDD isomer was not detected in  treated sludge.
  • Stack emissions of non-methane THC increased from 6.7 to
    11 parts per million by volume (ppmv) during the demonstra-
    tion;  the  maximum emission  rate was 0.2 pounds per day
    (ppd). The  maximum particulates  emission rate was 0.02
    ppd,  and  no chlorides were measured in stack gases.

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
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                             POSTAGE & FEES PAID
                                      EPA
                                PERMIT No. G-35
    EPA/540/MR-92/019

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