Download MSVR-Final Brochure (NIH Acknowledgement)

Microwave Soil Vapor Treatment
On-site Carbon Regeneration
Closed Circulation System
Zero Contaminant Discharge
Chemical Recovery for Recycle or Disposal
CHA Corporation
372 W. Lyon
Laramie, WY 82072
Telephone:
(307) 742-2829
Fax:
(307) 742-3415
Website:
www.chacorporation.com
Email:
[email protected]
Background
The National Institute for Health has awarded a
SBIR Phase I grant to CHA Corporation to build
a prototype microwave reactor system capable of
recovering chemicals from soil vapors produced
during hazardous site remediation without using
catalytic oxidation. The field testing has been
successfully completed at McClellan Park. The
U.S. Air Force Real Property Agency also
supported this field demonstration. For the past
13 years CHA Corporation has focused on the
utilization of microwaves to induce or enhance
chemical reactions. These efforts, made possible
through industrial and governmental support,
emphasize the development of new technologies
for gas and water cleanup through selective
destruction in contaminated waste streams.
CHA
Corporation
Principles of Technology
The CHA microwave-based gas cleanup
process is designed to capture and recover a
wide variety of both chlorinated and nonchlorinated volatile organic compounds
(VOCs), many of which are commonly found
at industrial and military sites.
This
technology is currently being demonstrated at
McClellan Air Force Base.
CHA Corp Microwave Carbon Regeneration & Chemical Recovery System
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CHA Corporation Field Demonstration
Fall 2003
Microwave Soil Vapor Treatment
Activated carbon readily adsorbs most VOCs, allowing
removal efficiencies near 100% if sufficient carbon
adsorbent and appropriate contact times are utilized. As the
carbon continues to adsorb VOCs, the available adsorption
sites are diminished and the carbon becomes saturated.
Microwave energy is used to regenerate the saturated carbon.
Rapid on-site regeneration of the carbon facilitates
continuous, cost effective removal of VOCs by reusing the
carbon in adsorption systems. When using microwaves,
VOCs desorbed from the carbon are efficiently condensed in
a condenser and recovered as a liquid. Overall, the process
uses granular activated carbon (GAC) to remove VOCs from
the air stream, continuously regenerates the used GAC with
microwaves, and recovers the VOCs desorbed from the GAC
by condensation. There are three main components of the
CHA Microwave Soil Vapor Treatment System:
Adsorber vessel
Microwave carbon regeneration reactor
Two-stage condenser system
Adsorber Vessel
The inlet and outlet of the adsorber vessel will be connected
to an on-site SVE (soil vapor extraction) system. The
contaminated air stream from the discharge side of the SVE
main blower enters the bottom of the adsorber and passes
upward through the GAC adsorption bed. Normally, the
cleaned air will exit the adsorber and will be discharged to
the atmosphere. However, in this field demonstration, the
cleaned air is recycled back to the inlet of the SVE FTO
(flameless thermal oxidizer). This provides a closed system
for the contaminated air, resulting in zero emissions
discharge into the atmosphere. As the GAC in the adsorber
becomes saturated, the saturated GAC is transported to the
microwave regeneration reactor by means of a pneumatic
conveyor system. Consequently, the regenerated GAC
above the clean gas outlet moves towards the bottom of the
adsorber, allowing continuous operation of the adsorber.
Microwave Carbon Regeneration
Reactor
The moving bed microwave carbon regeneration reactor
consists of two stainless steel hoppers with cone-shaped
bottoms, a quartz tube reactor, a rotary valve with
variable speed drive motor, a multimode cavity
applicator, and a 3-kW microwave generator. Saturated
carbon is transported from the bottom of the adsorber to
the top feed hopper by the pneumatic conveyor system.
The carbon passes through the quartz tube reactor,
where it is exposed to microwave energy in the
multimode cavity applicator. The rotary valve is used to
control the carbon flow rate through the quartz tube
reactor. The regenerated carbon is stored in the receiver
hopper until it is returned to the top of the adsorber.
Two-Stage Condenser System
The two-stage condenser system is used to recover
organic chemical vapors as the carbon is regenerated.
Nitrogen is used as a sweep gas to remove chemical
vapors desorbed from the carbon.
If there is
accumulation of excess sweep gas, a slight pressure rise
in the regenerator is detected, causing a valve to open,
venting the excess gas back to the adsorber inlet. Again,
no vapors are allowed to leave the closed regeneration
system. Condensed liquid in the nitrogen stream is
collected in a knockout pot prior to entering the
compressor. In order to separate the remaining chemical
vapors in the nitrogen stream, the outlet of the
compressor flows into the second water-cooled
condenser. Chemical vapors in the nitrogen stream are
cooled in the second condenser and the condensed liquid
is collected in the second knockout pot. Vapor free
nitrogen is recycled back to the microwave regenerator.
Technological Advantages
Provide on-site regeneration of GAC, eliminating
handling and transporting of hazardous saturated carbon.
Restore the original adsorption capacity of GAC and
eliminate the need for supplying fresh GAC.
Reduce the volume of air containing VOCs and other
contaminants that require further treatment.
Recover VOCs and other contaminants in soil vapors and
avoid the generation of secondary air pollutants.
Provide an effective means to replace the existing
catalytic oxidizers and acid gas scrubbers by GAC
adsorbers.
Save energy by eliminating natural gas used in catalytic
oxidizers and flameless thermal oxidizers.
Recycle valuable recovered chemicals such as fuels and
solvents.
Reduce the life-cycle cost for base cleanup significantly.