United States
 Environmental Protection
 Agency	
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
 EPA/600/S2-89/048  Nov. 1989
 Project  Summary
 Experimental  Investigation  of
 Critical Fundamental  Issues  in
 Hazardous  Waste  Incineration
 J. C. Kramlich, E. M. Poncelet, R. E. Charles, W. R. Seeker, G. S.
 Samuelsen, and J. A. Cole
  The results  of a laboratory-scale
program  investigating  various
fundamental issues in  hazardous
waste incineration are presented. The
key experiment for each study was
the  measurement  of  waste
destruction behavior  in a subscale
turbulent  spray  flame.  Nozzle
performance of subscale nozzles was
directly measured in terms of droplet
size  by laser diffraction.  Because
some wastes can be highly viscous
or contain solids, atomization quality
can be a  limiting  factor,  even  for
correctly operating nozzles. Even in
the absence  of secondary atomi-
zation,  an influence of  compound
concentration in the feed stream has
been noted in field data. In field tests,
a large number  of compounds that
are apparently  unrelated to the
original  waste compounds  are
observed.
  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
back).
Introduction
  Incineration is an attractive alternative
for the disposal of organic hazardous
wastes. As opposed to landfilling or deep
well injection, it effects  a permanent
solution.  However,  incineration  is
attractive only if the waste is destroyed to
an acceptable efficiency and if harmful
emissions of hazardous  byproducts are
avoided. The Federal government  has
recognized that  the public welfare
requires government regulation of waste
disposal  through the  Resources
Conservation and Recovery Act (RCRA).
Through RCRA, Congress  has charged
the  Environmental Protection Agency
(EPA)  with  the development  of
regulations and the enforcement of these
regulations.  The EPA has identified over
300 compounds as hazardous and  has
established licensing and  operating
regulations for devices destroying these
compounds. These regulations recognize
the fact that thermal destruction devices
cannot  operate to 100% efficiency.
Therefore, some emission level must be
defined as a minimum  standard for
safety. Currently, 99.99% destruction and
removal efficiency  (ORE) of the principal
organic hazardous constituents (POHCs)
Is the standard.
  Field testing of full-scale waste
destruction facilities and testing  of
subscale flames have shown that well
designed systems have little trouble
meeting  the  performance standard.
Indeed,  the evidence suggests that a
substantial  perturbation of design  or
operational  parameters is necessary  for
substantial emissions to occur. These
perturbations have been  termed "failure
modes" because the perturbations have
caused some fundamental rate  limiting
step to fail to completely destroy the
waste. Thus, the key questions with
respect to ORE are:

  What  mechanisms permit  the small
  amounts of waste to  escape during
  high efficiency operation?

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  What mechanisms are responsible for
  waste release during a failure mode?


Objectives
  The objectives of this study were  to
define  and  address experimentally a
series  of  issues  fundamental   to
hazardous  waste incineration. These
issues were  selected  because  they
represent  practical   problems   or
approaches  to practical problems  that
can be addressed  through  fundamental
research. These issues include:

• Effect of Waste Atomization on  ORE:
  Combustion  efficiency  can  be
  degraded in industrial  flames by poor
  fuel atomization (i.e.,   large  droplets).
  The  key  problem  is defining  the
  mechanism  by  which  ORE   is
  influenced by waste atomization.

• Effect of Secondary  Atomization  on
  ORE: This addresses the question, can
  fragmentation  of  waste droplets  by
  internal boiling improve ORE?

• Effect of Waste Concentration on ORE:
  Field  data  indicate  a  correlation
  between waste  concentration and ORE.
  Identification  of  the mechanism
  responsible for this behavior would be
  an important step toward  defining  the
  fundamental release mechanism.

• PIC Formation: Considerable work has
  been  done  identifying  products  of
  incomplete  combustion  (PICs)  in
  idealized  plug flow experiments.  Here,
  the appearance of PICs  in turbulent
  spray flames is addressed.

In  addition  to  providing  specific
information on these issues, one goal of
this work was to provide insight into the
critical,  rate-limiting processes  that
govern  waste release from  practical
devices.


Conclusions
  Principal conclusions of this study are:

  LWasfe  Atomization: For  degraded
    atomizers,  the  principal  cause  of
    poor waste destruction efficiency is
    the increase in  the fraction of  very
    large droplets. The extreme delay in
    evaporation  associated with these
    large droplets can  allow  unreacted
    material to  reach  the   wall  or
    penetrate through the flame zone.
    Design to avoid this behavior is more
    difficult for  hazardous waste
    incineration  than for  conventional
    combustors because:

• A large amount of empirical experience
  has  been  obtained on liquid  fuel
  combustion.

• The  atomization  properties  of waste
  streams  (viscosity, surface tension,
  presence of  solids)  can  vary
  considerably.

The  results  suggest  a  design
methodology in which atomization quality
is  directly  measured in  cold  flow.  The
size and trajectory of the largest droplets
are  compared to  the   combustion
chamber geometry  to determine  the
initial suitability of the design

  2.Secondary Atomization: Some
    materials may have sufficiently  poor
    atomization  properties to prevent
    acceptable  spray fineness at any
    conditions.  The use  of  a volatile
    waste dopant was shown to  inc
    in-flame droplet fragmentation an
    Improve ORE. This suggests that
    of volatile dopants, or the blendin
    different waste streams can be  i
    to avoid poor ORE due to penetri
    of large droplets through the flam

  3. Compound Concentration: Field
    data  show a  remarkable correli
    between compound concentratic
    the  feed  and ORE.  Testing  in
    turbulent flame reactor also she
    this correlation. However, the  pa
    for the subscale flame indicated
    secondary  atomization  wa
    potential cause  of the  behavic
    higher concentrations. This doe;
    explain the subscale variation of
    with  waste  concentration at
    waste concentrations, nor  doi
    fully  explain the  field  dat<
    mechanism involving  mixing  lir
    equilibrium chemistry was prop
    for the field data.

  4. PIC Formation:  The yield  of
    organic compounds  was meas
    from the turbulent flame reactor
    results indicated that:

• PIC concentrations were  compa
  with waste emissions.

• Incomplete combustion of the au)
  fuel rather  than true  PICs frorr
  doped  waste dominated the  app
  PIC emissions.

Thus, PICs can  arise from any  c
hazardous or nonhazardous constil
of the waste stream or the auxiliary
The  implication is that  conditions
promote  high combustion efficienc
favor reduced PIC emission.
                                                                         A-ll <; GOVERNMENT PRINTING OFFICE: 1989/748-012/

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  J. Kramlich, E. Poncelet, R. Charles, W. Seeker, G. Samuelsen, and J. Cole are
    with Energy and Environmental Research Corporation, Irvine, CA 92718-2798.
  W. Steven Lanier is the EPA Project Officer (see below).
  The complete report, entitled "Experimental Investigation of  Critical Fundamen-
    tal Issues in Hazardous Waste  Incineration," (Order No. PB 90-108 507!'AS;
    Cost: $23.00, subject to change) will be available only from:
           National Technical Information Service
           5285 Port Royal Road
           Springfield, VA 22161
           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
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300

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