United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA-600/S2-84-197 Jan. 1985
&ER& Project Summary
A Technical Overview of the
Concept of Disposing of
Hazardous Wastes in
Industrial Boilers
C. Castaldini, H. K. Willard, C. D. Wolbach, and L. R. Waterland
An evaluation of the concept of
disposing of hazardous wastes in indus-
trial boilers was conducted for the EPA
by the Acurex Corporation of Mountain
View, California. The information pre-
sented in the full report includes a
review of the rate of generation of
hazardous wastes which are candidates
for such use. and the present and
projected extent of the use of boilers for
this purpose. Also presented is an
inventory of industrial boilers, standard
boiler characteristics, and the tempera-
ture-time profiles of each boiler studied.
Theoretical temperature-time require-
ments for destruction of hazardous
wastes are compared to those expected
in industrial boilers to assess whether
the boiler is an appropriate vehicle for
waste destruction. Many key variables
must be considered in the use of this
type of model. Examples of these are
the degree of waste fuel atomization.
variation of gas residence times from
the mean furnace residence time, tem-
perature variations from the bulk stream
temperature across any furnace cross
section, and effects of boiler load
changes. The general conclusion is that
expected variations in these variables
are sufficient to warrant careful evalu-
ations of waste streams and boiler
combinations before firm conclusions
are reached on the environmental safety
of co-firing hazardous wastes as fuel.
An overview of the elements for a
complete evaluation of this potential
disposal technology is presented.
This Project Summary was developed
by EPA's Hazardous Waste Engineering
Research Laboratory, Cincinnati. OH,
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
Approximately 40 million metrictons of
hazardous wastes are currently generated
annually in the U.S. On May 18,1980, the
Environmental Protection Agency (EPA)
promulgated Phase I rules and interim
status standards regulating the genera-
tion, transportation, treatment, storage,
and disposal of these wastes under
authority of the Resource Conservation
and Recovery Act (RCRA). These and
subsequently announced regulations
place stringent restrictions on generators
of waste, including requirements for
manifesting wastes and chain-of-custody
liability. These restrictions may ultimately
impose additional costs on the waste
generator for off-site disposal. Thus,
economic incentives for disposing of
wastes on-site may result.
One method of disposing of wastes
with high organic content is by thermal
destruction. This can be done by high-
temperature incineration, which is regu-
lated by RCRA. However, another means
of thermal destruction is by co-combus-
tion of the waste or, if its heating value is
sufficiently high, use of the waste as a
fuel in devices whose primary purpose is
energy production, such as boilers and
process heaters.
Currently RCRA regulations specifically
exempt facilities that burn wastes in
-------
energy-producing operations from com-
plying with RCRA incineration mandates.
In fact, it is estimated that about 20
million metric tons of wastes that might
be classified as hazardous are currently
hurried as fuel or co-combusted with fuel
in energy-producing operations.
The purpose of this project was to
provide a basis for answering the follow-
ing key questions:
• What is the present and projected
magnitude of hazardous waste com-
bustion or co-combustion in boilers?
• Which waste materials and boiler
types are the most compatible?
• Are there potential mechanical diffi-
culties or environmental hazards
associated with waste combustion in
boilers?
The opportunity for combustion of
hazardous wastes in industrial boilers is
greater than currently practiced. There
are over 40,000 industrial boilers in the
U.S. with capacities greater than 10
million Btu/hr. These units offer great
potential for hazardous waste combus-
tion.
Regulations published on January 23,
1981 for incineration of hazardous wastes
require 99.99-percent destruction and
removal efficiencies (DREs) for the prin-
cipal hazardous organic constituents in
the waste incinerated. If the temperature-
time profile of a given boiler type is similar
to the time and temperature required to
destroy a given waste, then the disposal
of the hazardous waste in the boiler can
become an option open for more extensive
evaluation. This evaluation would con-
sider the compatibility of the primary fuel
to the waste, potential impacts on the
design conditions of the boiler, retrofit
requirements, and fugitive and secondary
emissions. The full report presents in-
formation on each of these issues.
Summary of the Research
Conducted
The objective of this project was to
assess the problems and potential of
destroying hazardous wastes in industrial
boilers. The major elements of this over-
view include:
• Surveying hazardous waste generation
and disposal practice
—Document present generation and
disposal inventories
—Establish the present extent of waste
combustion as fuel
—Project the future extent of waste
combustion as fuel
• Assembling an inventory of industrial
boiler capacity capable of hazardous
waste combustion
—Inventory by size, design type, and
fuel fired
—Provide regional inventories
—Select a set of model boilers typifying
the installed population
• Characterizing the combustion char-
acteristics of typical boilers
—Establish boiler operating and design
characteristics
—Establish boiler temperature-time
profiles as a function of boiler
characteristics
• Characterizing hazardous wastes suit-
able for combustion
—Specify the requirements (tempera-
ture and time) for waste constituent
destruction
—Define the composition of candidate
wastes and rank the listed waste
streams for potential use as fuel
• Identifying the matrix of wastes/boiler
typ.es suitable for hazardous waste
combustion
—Combine boiler combustion charac-
teristics with waste constituent
destruction requirements
—Specify boilers/wastes achieving
99.99-percent destruction
• Provide an overview of considerations
for further evaluating the waste/boiler
destruction option.
Conclusions and
Recommendations
As discussed in the introduction, the
primary purpose of this study was to
determine whether hazardous wastes
could potentially be safely destroyed
under the conditions found in a number of
industrial boilers. The study determined
that the thermal destruction requirements
of most wastes evaluated are satisfied by
the conditions found in a large percentage
of industrial boilers currently in use.
However, because of the nature of such a
theoretical evaluation, it can only be
concluded that boilers appear to have the
potential for safe waste destruction.
Further experimental work is necessary
to confirm this conclusion. In this respect,
this study represents only a starting point
for more detailed technical evaluation of
industrial boilers as vehicles for the safe
disposal of hazardous wastes. This project
did establish that further work is war-
ranted and could result in significa
benefits in both the expansion of sa
hazardous waste disposal capacity at
the utilization of the energy content th
wastes represent.
Conclusions
The following conclusions were deve
oped from this theoretical analysis:
• Co-firing of hazardous wastes at
small percentage of the base fui
(about 5 to 10 percent) appears to be
viable method of disposing of mo:
hazardous organic material.
• Co-firing many wastes or firing som
high Btu content wastes entirely ma
produce lower levels of criteria pollu
tant and trace element emissions tna
either traditional coal or oil combus
tion.
• The conditions found in many types c
watertube boilers appear to be suffi
cient to achieve at least 99.99-percen
destruction of most hazardous organi
compounds.
• The conditions found in firetube boiler
do not appear to be suff fcient to destro1
all hazardous organic materials. Then
is too great a likelihood that cold tube
wall quenching of the waste degrada
tion reactions is possible befori
complete destruction can occur.
• Watertube boilers whose furnace ex
temperatures are greater than 1,100
(1,500°F) and whose furnace meat
residence times are greater than om
second appear to be best candidate:
for the destruction of simple hazardous
organic waste streams.
• Complex organic waste streams art
likely to require approximately 200H
(360°F) higher temperatures.
• Insufficient data are available to predic
whether hazardous products of com-
bustion could be released from a boiler
Laboratory data should, however, be
able to provide some conservative
estimates of the likelihood of the
release of such materials. The forma-
tion of hazardous products of combus-
tion must be addressed by furthei
research.
• In the absence of other data, the
autoignition temperature appears tc
be a possible predictor of the relative
ease of thermal destruction of a
compound. This needs further confir-
mation.
-------
Recommendations
This study showed that, theoretically,
certain boilers can destroy hazardous
organic materials. This work suggests
that the following areas of further re-
search need to be addressed:
• The available waste destruction kinetic
data are based on results obtained
from thermal destruction analytical
system (TDAS) experiments. While
such work is very useful, it does not
model the destruction phenomena that
occur in a flame. This type of informa-
tion must now be obtained through a
flame-mode destruction apparatus.
• The current TDAS work (as well as
future flame-mode work) needs to be
broadened to include destruction
characteristics of the wastes under
the pyrolytic (no oxygen) as well as
under high oxygen concentration con-
ditions. Further information on the
formation and destruction of hazard-
ous products of combustion is also
needed.
• The information that will be obtained
by EPA under the hazardous waste
manifest system needs to be evaluated
to determine other wastes which are
potential candidates for destruction in
boilers.
• A field program needs to be initiated to
verify the preliminary results of this
study. The program should include
testing of the full boiler system, not
just the boiler emissions. The test
should include:
—Full input/output analysis of all
streams
—Boiler temperatures at a number of
points in the combustion chamber
—Boiler residence time variations
—Testing for the principal organic
hazardous components in the waste
and for hazardous products of com-
bustion. TDAS data can be used to
determine which products of com-
bustion could occur and hence
should be tested for.
C. Castaldini, H. K. Willard, C. D. Wolbach, and L R. Waterland are withAcurex
Corporation, Mountain View, CA 94039.
Robert A. Olexsey and George C. Huffman are the EPA Project Officers (see
below).
The complete report, entitled "A Technical Overview of the Concept of Disposing
of Hazardous Wastes in Industrial Boilers," (Order No. PB 85-138 576; Cost
$ 17.50, 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 Officers can be contacted at:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
* U S. GOVERNMENT PRINTING OFFICE, 1985 - 559-016/7881
-------
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
• <'1 ^ i CJ^^??!!"^ »*; |
POSTAGE & FEES P/
.-••-;. ' ,,EP^ 7 .<
' , PERMIT tfo.G-35:
Official Business
Penalty for Private Use $300
CHiCAGU It 6060a
------- |