\ I /
                  United States
                  Environmental Protection
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711 //
                  Research and Development
EPA/600/S2-89/037 Aug. 1989
f/EPA         Project Summary
                   Potential Technologies  for
                   Collection and  Destruction  of
                   CFCs,  Halons,  and  Related
                   Kirk E. Hummef and Thomas P. Nelson
                    This report gives recommen-
                  dations of a multidisciplinary panel of
                  experts on new or novel technologies
                  (or modifications  of  existing
                  technologies) which show the most
                  promise  for the  collection  and
                  destruction of chlorofluorocarbons
                  (CFCs) and related  compounds. The
                  panel members met in a "roundtable"
                  format to  discuss their experiences
                  and relate them to the compounds of
                  interest.  The  panel  identified
                  technologies that held  the most
                  promise  and  suggested  general
                  areas  of research and development
                  needed to develop collection and
                  destruction technologies.
                     This  Project  Summary  was
                  developed by EPA's Air and Energy
                  Engineering Research  Laboratory,
                  Research Triangle Park, NC,  to
                  announce  key findings of the research
                  project that is fully documented in a
                  separate report of the same title (see
                  Project Report ordering information at

                    A family of chemicals  known  as
                  chlorofluorocarbons (CFCs)  has been
                  implicated  in  the depletion  of
                  stratospheric ozone. A number of adverse
                  health and ecological effects could result
                  from such  depletion.  For this reason a
                  number of strategies or options for
                  controlling the  release  of these
                  compounds are  being evaluated by
                  governments and industry worldwide.
  Existing technological means have not
been conclusively demonstrated as
suitable for curtailing  CFC emissions
from certain sources to acceptable levels.
Because of their great chemical stability,
CFCs are very difficult to break down. In
order to be destroyed, the CFC would
first have to be collected. Thus, EPA felt
a program was needed to evaluate
various existing and  new  or  novel
technologies  for  the  collection  and
destruction of CFCs.
  The  Navy needs  new  or  novel
technology to remove and destroy  toxic
compounds  which may be used in
chemical warfare  (CW)  The current
generation of shipboard  CW  defensive
systems are based  on activated carbon
adsorption.  These  devices  are
considered  effective  against  high
molecular weight, low volatility chemicals
such  as "nerve agents" which  are
strongly adsorbed.  However,  in order to
deal with high volatility, weakly adsorbed
toxic  compounds  (such as  hydrogen
cyanide, HCN), a reactive impregnant has
been  added to the  carbon. It is  known
that some CFCs are not strongly held on
carbon,  so it was assumed  that  (if  a
technology could  be developed for
collection and/or destruction of CFCs) it
might be  possible  to  modify such  a
process for shipboard use as  a  CW
defensive system.
  To this end, the U.S. EPA and the
Navy proposed assembling a  multi-
disciplinary  panel  of experts to
recommend new or novel technologies
(or modifications of existing technologies)

which show the most promise for future
development. The panel would then meet
in  a  "roundtable" format to discuss the
proposed technologies. This report gives
results of this meeting.

Summary of Expert Panel

   To address the issues for the EPA and
the Navy in  terms of their  particular
interests,  the  technologies  were
evaluated for two distinct classes:
   • Technologies  capable  of collecting,
    removing, or destroying  the
    compounds from the  feed  stream
    and providing  an off-gas or  effluent
    suitable  for  breathing  air  (for
    example,  shipboard  CW  defense);
   •Technologies capable  of collecting,
    removing, or destroying  the
    compounds from the  feed  stream
    with no requirement for a breathable
    off-gas   (for  example,   bulk
    incineration of contaminated CFCs).
   The   panel   reviewed   many
technologies including thermal, chemical,
and  biological processes.  In  most
instances biological  processes can  be
used only on dilute aqueous streams and
the biological destruction  rate is very
slow.  This is  based on experience with
highly halogenated  polychlorinated
biphenyls (PCBs). Therefore, for  the two
applications at hand, biological processes
were eliminated as possible  candidates.
   The overall conclusions  of the expert
panel  for the breathable air  situation was
that the use  of carbon  adsorption as
currently done by the Navy  was the most
reasonable,  commercially available
process. However,  carbon  adsorption is
limited because  high  volatility  toxic
compounds  are  not strongly held  on
carbon,  and the reactive  impregnants
which  are  added  to  remove  these
compounds are non-specific (they react
with a host of other contaminants) and of
limited capacity.  Furthermore, there is
currently  no method to  determine when
the carbon needs to be replaced.
   The potential candidates to  replace
the present carbon  adsorption  system

   • Inorganic Membranes: These  may
     be  either ceramic membranes or
     carbon molecular sieves. Inorganic
     membranes  operate  at  high
     temperatures  and are chemically
     resistant. A carbon bed may still be
     required  downstream or metallic
     salt impregnants may  be needed to
     react with high  volatility  com-
  •  Chemical  Scrubbing/Destruction:
     This technology includes the use of
     a highly  alkaline,  non-aqueous
     scrubbing liquor  to  absorb  and
     destroy the compounds of interest.
     This is superior to scrubbing alone,
     since equilibrium  limitation is
     removed. Downstream treatment is
     required to prevent  contamination
     of the carbon bed. Pretreatment of
     the  inlet  air may be  required to
     remove moisture.
  •  Corona  Discharge:  This  process
     uses highly energized electrons
     from an ionized corona discharge to
     dissociate  the  compounds of
     interest.  This process operates at
     essentially ambient  temperature
     and pressure.  A  carbon  bed  may
     still be  required  downstream. A
     high  voltage  power supply is
     required  and  ozone and/or  NOX
     may be generated.
  •  Metals Scrubbing: This technology
     uses  an  active metal  such  as  zinc
     or  aluminum  to  react  with  the
     compounds of  interest. It is  known
     that  active  metals  can  rapidly
     destroy halogenated  organics such
     as  PCBs. One advantage is that a
     solid salt may be formed which can
     easily be  removed. Pretreatment of
     the  inlet  air may be  required to
     remove moisture  since there  may
     be a problem in maintaining an
     active metal  surface   in  the
     presence  of air and moisture.
  •  New  Adsorbents:  This technology
     uses tailor-made  adsorbents, such
     as  new zeolites,  and aluminas, or
     polymeric adsorbents, to obtain the
     desired  separation.   These com-
     pounds have a  uniform or well-
     defined structure which results in
     more consistent performance. Also,
     their properties  may be  altered
     using various pretreatments. A new
     selective  adsorbent  bed  could
     conceivably  allow  some less toxic
     compounds through to be handled
     by a cheap carbon bed instead of
     an expensive  specialty adsorbent
  In the area of destruction of  fully
halogenated organics without the  need of
a breathable  off-gas,  current thermal
destruction processes may  be  adequate.
CFC  wastes   are currently   being
destroyed in   at  least one permitted
facility. The harsh environment  created
by the hydrogen fluoride (HF) in the off-
gas is one potential cause for  concern;
specially designed internal firebrick and
mortars may be required.
   Although  CFCs are currently  b
incinerated,  there are very limited
regarding  the  destruction  efficient
products  of incomplete combus
(PICs)  resulting  from  these  operati
Data are lacking  regarding the qus
and fate of PICs; such compounds
be toxic  and/or  may  pose a  three
stratospheric ozone.
   To  summarize  the  status
incineration  of CFCs, this is  the
demonstrated  technology  whic!
currently  being  used, and  will  li
continue  to  be used  in the near I
However, the feared potential of corr<
attack to the refractory and  the lac
accurate  data  on destruction effici
and  PICs are problems  which re<
   Other  technologies   which  \
recommended as good candidates  v
there is not a need for breathable air

   •  Catalytic  Thermal  Destruc
     Metal  catalysts   have   t
     successfully used to destroy i
     hydrocarbon  gas  stream
     reduced   temperature, the
     saving  energy and  improvmc
     economics  of  this  coi
     technology. Potential problem;
     the  destruction of chlorir
     hydrocarbons using this techn
     include low destruction  effic
     due to  catalyst deactivation.
   •  Chemical Scrubbing/Destru<
     This process has  already
     described for breathable air.
   •  Corona Discharge:  This  pn
     has  already been  describe
     breathable air.
   •  Metals Scrubbing: This proces
     already  been  describee
     breathable air.
   •  Pyrolysis: This technology in<
     thermal treatment in the absei
     air.  Since  CFCs  are  dest
     through  bond  homolysi
     hydrolysis,  simple heating v
     air is sufficient to break the I
     Heating without  air  resu
     reduced gas flow which can
     smaller  downstream  trea
     equipment.  Potential  prol
     include the  possibility of coi
     attack  and the formation of
     amounts of PICs.

   •  Supercritical  Water  Oxk
     (SCWO): This is a  modifica
     Wet Air  Oxidation (WAO
     scribed below)  which  invo
     supercritical fluid (water). Th
     technology  features much
     reaction rates than those ach

     in the well-known WAO technology.
     Furthermore,  SCWO operates  at
     very high oxidant  concentrations
     which  enhance  the  kinetics  and
     produce  favorable  equilibria.
     Potential  problems  are greater
     energy requirements  and possible
     metallurgical limitations.

  • Wet Air  Oxidation  (WAO): This
     process uses a  high temperature
     (>300°C) aqueous  stream  and
     oxygen to destroy many organic
     compounds.  Since CFCs  do not
     contain  a hydrogen  atom  or  a
     double bond, they are expected  to
     be resistant to oxidation. However,
     CFCs are susceptible to hydrolysis
     during incineration, so a  high
     temperature  aqueous  treatment
     could be effective.

Recommendations of the
Expert Panel

  The expert panel agreed that several
areas  deserve priority  for further

  CW Defensive Systems (Breathable

  • The panel agreed  that future
     research  in this area  should begin
     with fundamentals in  order  to
     determine the  optimum  long-term
  • The corona discharge process and
     the ceramic  membrane  process
     were proposed  as  good  potential
     candidates for initial research.
  • Liquid  scrubbing  with  a reactive
     component may have application;
     however, the Navy is  concerned
     with high humidity in the breathable

CFC Destruction (Non-Breathable Air)
  • A  literature  search is needed  to
     assemble all  available  data on
     previous  experience   with
     conventional  thermal  oxidation
     (incineration) of CFCs.
  • Products of incomplete  destruction
     (PICs)  should  be  identified  for
     residual ozone  depletion  potential
     and  toxicity  In  particular, the
     formation  of F  and Br  analogs  of
     dioxin should be investigated. Also,
     the thermal  stability of  CFCs and
     their basic combustion  properties
     should  be studied
  • Inorganic  membranes  should be
     studied  from a materials science
     perspective.  Also, new  adsorbents
     should  be investigated.
  • The chemistry   of  scrubbing
     systems  which contain  a reactive
     component should be studied.
  • The corona discharge process as it
     currently exists requires small scale
     tests,  energy efficiency  measure-
     ments,  and modeling.
  • Refractory linings that are resistant
     to  HF should be studied and tested.

  • Potential  catalytic  materials  for
     catalytic thermal destruction  should
     be evaluated.

   The  expert panel discussions on the
most favorable technologies that warrant
future development  for CFC destruction
and  naval  CW  defense  lead to  the
following conclusions.

1.    There do not appear to be any new
     near-term  technologies which  are
     as capable as activated carbon in
     removing a broad spectrum of toxic
     CW agents from shipboard air.

2.    Longer-term options  such as  the
     corona discharge process  and the
     ceramic membrane process should
     be pursued as  research projects
     where these options  could lead to
     improved  technologies  for
     shipboard  CW defense  compared
     to  conventional carbon adsorbers.

3.    Thermal incineration appears to  be
     feasible in  the near-term  for  the
     destruction of  bulk  quantities  of
     CFCs  (such  as  contaminated
     refrigerants or  waste solvents),
     although  materials of construction
     for the incinerator and byproducts
     of  combustion  should be further

4.    Sources  of dilute  emissions  of
     CFCs may  require  technologies
     available in the longer-term.  These
     options, which  include technologies
     such  as  catalytic  thermal
     destruction, pyrolysis, or  wet  air
     oxidation, may  be source-specific.

  Kirk E. Hummel and Thomas P. Nelson are with Radian Corporation, Austin, TX
  Dale L. Harmon is the EPA Protect Officer (see below).
  The complete report,  entitled  "Potential  Technologies  for  Collection and
        Destruction of CFCs, Halons, and Related Compounds," (Order No. PB
        89-219 968/AS; Cost: $15.95 subject to change) will be available only from:
           National Technical Information Service
           5285 Port Royal Road
           Springfield, VA22161
           Telephone: 703-487-4650
  The EPA Project Officer can be contacted at:
           Air and Energy Engineering Research Laboratory
           U.S. Environmental Protection Agency
           Research Triangle Park, NC 27711
United States
Environmental Protection
Center for Environmental Research
Cincinnati OH 45268
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