United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S2-86/015 Aug. 1986
&EPA Project Summary
Design and Construction of a
Mobile Activated Carbon
Regenerator System
R. H. Hiltz
Activated carbon adsorption has be-
come a standard treatment for the clean-
up of contaminated water streams. To
facilitate such cleanups, mobile carbon
adsorption units have been constructed
and are now in use. Such units can be
moved to spill sites or other points re-
quiring water cleanup. Their primary
drawback is the logistics associated with
the disposal of the spent (contaminated)
carbon and its replenishment.
The adaptation of adsorption systems
to a mobile base suggested that regen-
eration systems could be similarly
adapted. A program was undertaken to
assess the feasibility of such adaptation
and to design and build a mobile carbon
regeneration unit that would also in-
corporate an incinerator and scrubber
system to degrade and dispose of the
offgases.
A system was designed and built based
on technology developed for the fabri-
cation of a laboratory-sized regenerator.
Housed in a standard van-type trailer,
the system met all weight and size
limitations for over-the-road operation.
The system includes a rotating barrel
kiln to regenerate the carbon thermally,
an incinerator or afterburner and a
scrubber to treat the offgases, and a
separator to reclaim the reactivated
carbon granules.
Test runs using spent carbon from
treatment of a spill were quite success-
ful. The carbon was returned to es-
sentially 100% activity, with an 88%
volume recovery- The unit has been
delivered to EPA for their use.
This Project Summary was developed
by EPA's Hazardous Waste Engineering
Research Laboratory, Cincinnati, OH, to
announce key . .-'lings of the research
project that Is fully documented In a
separate report of the same title (see
Project Report ordering Information at
back).
Introduction
The full report details the development
and construction of a mobile unit for
regenerating activated carbon in the field.
The system was developed to solve some
problems presented by a portable carbon
adsorption system used to treat con-
taminated water streams on site.
When hazardous chemicals spilled in
the field or leachate from landfills or
waste storage sites threaten a water
supply, activated carbon treatment is
standard practice. Because activated
carbon has a natural tendency to adsorb
selected classes of chemicals, when such
chemicals are dissolved or dispersed in
water, carbon preferentially removes
them.
To facilitate cleanup, portable carbon
adsorption systems have been developed.
These trailer- or skid-mounted units can
be moved by road or air to the cleanup
site. The portable systems have proved
quite versatile and effective, but they
have a significant drawback — the logistic
and administrative barriers associated
with the disposal of spent (contaminated)
carbon and its replacement. Large quan-
tities of carbon are usually required for
cleanup operations. Although the carbon
can technically be regenerated commer-
cially, it must be moved to a facility
having the necessary processing equip-
ment and appropriate permits for carbon
reactivation. Also, fresh carbon must be
moved to the field site to keep the cleanup
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operation active. This approach to regen-
eration can be complicated if hazardous
materials (such as PCBs or TCDD) are
involved for which strict regulations or
prohibitions exist that affect commercial
reactivation. For economic reasons, com-
mercial regeneration facility operators are
unwilling to operate their equipment
routinely at the temperatures needed to
destroy PCBs and TCDD. Further, the
regeneration market for carbon contami-
nated with these substances is not large
enough to justify the facility operator's
incurring the public concern that would
result if the facility were to accept such
substances. Because of these problems
with commercial reactivation, carbon
used to treat PCBs or TCDD is currently
being disposed of in chemical landfills
rather than being regenerated. Thus, the
toxics accumulated on the carbon are not
destroyed, only stored, and may enter the
environment in the future.
Clearly, the utility of portable activated
carbon systems (particularly when used
on contaminated carbon that is not com-
mercially regenerable) would be enhanced
if the carbon could be regenerated at the
cleanup site. Since the adsorption system
had been adapted to a mobile base, it
was not difficult to conceive of a regen-
eration process that could be fitted onto a
skid or mobile trailer bed.
Many materials that would be adsorbed
by the carbon can be stripped off by
means of steam or other thermal treat-
ments to regenerate the adsorptive capa-
city of the carbon. The residue removed
by this stripping would contain much
higher concentrations of the adsorbed
materials than the contaminated water
would. Since this residue still has to be
disposed of at an acceptable facility, the
regeneration system would have to con-
vert the residue at the spill site to a form
suitable for disposal.
In an earlier federally sponsored pro-
gram (Juhola, A.J., "Laboratory Investi-
gation of the Regeneration of Spent
Activated Carbon," U.S. Public Health
Service, Contract PH 14-12-469, 1970
Final Report MSAR 70-184), a laboratory-
sized carbon regeneration unit was devel-
oped that used thermal treatment to strip
the adsorbed material. This unit provided
a starting point for the design of a portable
unit that could provide on-site carbon
regeneration and waste material incin-
eration at spills and hazardous waste
sites.
System Description
The carbon regeneration system con-
sists of a direct-fired thermal regenerator
or kiln, an incinerator to degrade the
material stripped from the carbon, and a
scrubbing tower to remove undesirable
materials from the offgases (Figure 1).
The carbon regeneration unit is trailer
mounted for rapid transport to the spill
site, and self-contained for operation
when deployed near a source of fresh
water and provided with fuel. Only two
trained operators are required.
Spent carbon feed is drained of excess
water and transferred to a feed hopper at
the rear of the trailer. A screw feed
meters the spent carbon into a kiln. The
carbon is regenerated as it progresses
through a rotating kiln barrel, which is
direct-fired with a controlled-gas compo-
sition. The regenerated carbon product is
discharged from the kiln barrel through a
firing breech to a slurry quench tank
where a screening section removes fines
and discharges the remaining carbon for
reuse.
Flue and adsorbate gases are ducted
from the fume breech into a direct-fired
incinerator (afterburner) to oxidize the
objectionable contaminants. Incinerator
gases are then quenched with water
sprays and scrubbed with water or a
caustic solution to neutralize acids and
remove particulates before venting to the
atmosphere. Spent process water is
filtered, treated, and either recycled or
discharged to its source.
System design parameters were im-
posed by limitations of trailer size and
weight along with the expected over-the-
road stresses. Lightweight and resilient
fabrication was emphasized throughout,
including light structural containment,
ceramic fiber thermal insulation, and
flexible piping sections. Areas subject to
abrasion or corrosion at high tempera-
tures are protected with Inconel or stain-
less steel.
All process equipment is mounted in a
special semi-trailer van measuring 2.44
m W x 13.7 m L x 4.1 m H when closed
for storage or transit. A self-supporting
platform base was selected for off-the-
road operation with minimal bed deflec-
tion. Full enclosure is provided during
transport. The sides open to become an
awning and a platform to provide rain
protection and equipment access walk-
ways during operation (Figure 2). The var
is fitted for transportation by tractor-trucl*
or piggy-back by rail in accord with al
applicable requirements and regulations
Conventional width, height, length, anc
weight road limits are met.
Results and Conclusions
The program resulted in the successfu
design and fabrication of a trailer
mounted carbon regeneration system tha
met the original objectives. The regen
eration rate was 45.4 kg/hr of 40-mesf
granular carbon regenerated at <20°/
carbon loss and >75% adsorption capacity
A pilot run was made with the uni
before its shipment to EPA. An activate!
carbon material contaminated witl
Toxaphene (Ci0Hi0CI6) and minor quanti
ties of other chlorinated hydrocarbon
was obtained from EPA. Loadings wen
Figure 1. Prof He of kiln and incinerator.
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13% contaminant and 52% water. Regen-
eration yielded an 88% volume of a
completely reactivated material based on
iodine numbers. Vent gas analysis showed
CO and hydrocarbons to be below detect-
able limits.
The full report was submitted in ful-
fillment of Contract No. 68-03-2110 by
MSA Research Corporation under the
sponsorship of the U.S. Environmental
Protection Agency.
The development of the Mobile Carbon
Regenerator is continuing at Edison, New
Jersey, where testing on a variety of
contaminants under controlled conditions
and in the field will be conducted.
Figure 2. Trailer open for system operation
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R. H. Hiltz is with MSA Research Corporation. Evans City, PA 16033.
John E. Brugger is the EPA Project Officer (see below).
The complete report, entitled "Design and Construction of a Mobile Activated
Carbon Regenerator System," {Order No. PB 86-156 486/AS; Cost: $11.95,
subject to change) will be available only from:
National Technical Information Service
5285 Port Royal Road
Springfield, V'A 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Releases Control Branch
Hazardous Waste Engineering Research Laboratory—Cincinnati
U.S. Environmental Protection Agency
Edison, NJ 08837
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S2-86/015
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