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
EPA/600/S2-89/048
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