United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati, OH 45268
Research and Development
EPA/600/S2-85/013 Apr. 1985
Project Summary
Preliminary Assessment of Costs
and Credits for Hazardous Waste
Co-Firing in Industrial Boilers
R. McCormick and L. Weitzman
The full report provides preliminary
information on the costs and credits
associated with hazardous waste co-
firing in industrial boilers. The main
objective is to identify and evaluate
the costs/credits inherent in current
hazardous waste co-firing practices,
plus the additional costs that may be
incurred as a result of more stringent
emissions limitations.
An overview of current hazardous
waste/industrial boiler co-firing prac-
tices is provided. This overview ad-
dresses the type of waste now being
disposed of in boilers, the generic
designs and capacities of boilers now
employing waste co-firing, and the
types of air pollution control device
(APCD) retrofits that may be required
in the advent of air emissions regula-
tions. Parametric cost estimate
methods are provided for: (1) waste
handling equipment addition, (2) com-
bustion system retrofit, (3) APCD
retrofit, (4) incremental O&M costs,
and (5) fuel savings and waste
disposal credits. The cost estimating
approach is designed to account for
differences in waste characteristics,
boiler design, capacity, and
waste/fuel co-firing ratio. Finally,
cost/credit calculations are presented
for two hypothetical waste co-firing
scenarios. These calculations are
presented to illustrate how the infor-
mation provided in this report can be
used; no conclusions concerning the
economy of waste co-firing are in-
tended.
This Project Summary was
developed by EPA's Hazardous Waste
Engineering Research Laboratory, Cin-
cinnati, Ohio, to announce key find-
ings of the research project that is ful-
ly documented in a separate report of
the same title (see Project Report
ordering information at back).
Introduction
The practice of burning hazardous
wastes in industrial boilers has become in-
creasingly popular over the past decade.
The reasons for this trend are two-fold:
(1) increased prices for conventional
• fuels, favoring waste substitution or co-
firing as a means of reducing fuel ex-
penditures, and
(2) stricter environmental regulations
and higher costs for hazardous waste
disposal by conventional methods, pro-
moting waste co-firing as a means to
eliminate or reduce waste disposal costs.
Two regulatory actions in particular
have favored boiler co-firing as a hazard-
ous waste disposal alternative. The first
such action was the virtual ban on liquid
waste landfilling which promoted thermal
destruction (in incinerators, boilers, ce-
ment kilns, etc.) as a favored disposal
method for hazardous organic liquids. The
second regulatory action favoring boiler
co-firing was the promulgation of emis-
sions limitations for incinerators burning
hazardous wastes. Since 1980, hazardous
waste incinerators have been subject to
Destruction and Removal Efficiency (DRE)
requirements for hazardous organic con-
stituents of the waste, paniculate emis-
sion limitations, and HCI removal re-
quirements. No such regulations have
been imposed on boilers burning hazard-
ous wastes.
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In order to assess the need for and im-
pacts of regulations governing hazardous
waste co-firing in boilers, the United
States Environmental Protection Agency
(EPA) is currently conducting a
Regulatory Impact Analysis (RIA) study.
One of the major elements of this pro-
gram is an economic assessment of the
impacts of boiler performance standards
and associated air pollution control re-
quirements. The study addressed in this
project summary is intended to provide
preliminary cost/credit information for
current boiler co-firing practices. As such,
it serves as a precursor to the economic
impact assessment phase of the RIA.
Objectives and Scope
The underlying objective of the study
was to provide a preliminary evaluation of
the costs and credits associated with
hazardous waste co-firing in industrial
boilers. Specific objectives are as follows:
(1) Identify the major waste/boiler co-
firing scenarios that need to be ad-
dressed for the purposes of the RIA.
This is basically an assessment of cur-
rent and probable future co-firing
practices.
(2) Identifying the major costs and credits
associated with boiler conversion to
waste co-firing, including capital re-
quirements for boiler retrofit, in-
cremental O&M costs, fuel savings
credits, and credits for elimination of
alternative waste disposal costs.
(3) Develop preliminary cost data for the
major and most probable boiler retrofit
activities, including possible addition
of air pollution control equipment.
(4) Develop a parametric approach to
estimate retrofit costs, incremental
O&M costs, and credits so that
cost/credit tradeoffs can be projected
as a function of waste type, waste:
fuel co-firing ratio, boiler design and
capacity, and potential air pollution
control requirements.
Due to the preliminary nature of the
study, none of the objectives are ad-
dressed in a completely thorough or
rigorous manner. The goal is simply to
provide a basis for initial decision-making
and more detailed future study.
Co-Firing Scenarios Evaluated
The range of hazardous waste co-firing
scenarios addressed in the study is
necessarily limited in terms of waste type,
boiler design characteristics, capacity, and
waste: fuel co-firing ratios. The evaluation
is limited to those scenarios that best
represent current practice and probable
future practice.
Waste Characteristics
As a starting point, the evaluation is
limited to hazardous organic liquid waste
co-firing. This limitation is imposed
because organic liquids are the prime can-
didates for boiler co-firing. Second, the
economic evaluation is based on on-site
generation of the organic liquid wastes
being co-fired. The third major assump-
tion is that the majority of wastes co-fired
in industrial boilers possesses desirable
fuel properties. Heating values are as-
sumed to be greater than or equal to
8,000-10,000 Btu/lb, such that the waste
will support combustion. Water, ash, and
halogen contents are also assumed to be
reasonably low. Finally, reasonable mid-
range waste: primary fuel co-firing ratios
are considered. The range is 10-50%
waste with primary fuel, with the percent-
age based on gross heat input.
Boiler Designs and Capacities
The basic boiler designs considered in
the study are those characteristic of the
industrial size range (up to 250,000 Ib/hr
steam) originally designed to burn natural
gas, distillate oil, residual oil, or a com-
bination of these fuels. The three most
common design types, addressed in the
study, are as follows:
1. Scotch firetube, N-pass design,
packaged boilers for natural gas,
distillate oil firing. Single burner
design, with no economizer for air
heater. Typical capacities are 10,000
to 30,000 Ib/hr steam, up to 50,000
Ib/hr steam. Saturated steam up to
150 psig.
2. Watertube design for natural gas,
distillate oil, gas/distillate, or
gas/distillate/residual oil firing (with
oil preheat equipment). Single or
multiple burner design. Steam
capacities of 20,000 to 100,000 Ib/hr
saturated at 125 to 250 psig design
rating. Economizers not atypical at
more than 50,000 Ib/hr steam, but
air heaters rare.
3. Watertube design with multiple
burners for gas/oil firing. Steam
capacities of 100,000 to 250,000
Ib/hr and up, with turbogenerator
steam pressures and superheat in
the larger size ranges. Economizers
typical, and possibly air heaters.
These boiler designs are most common
(and compatible) for liquid waste co-
firing, although a limited number of coal-
fired boilers are also being used to co-fire
hazardous liquids. Both stoker and
pulverized coal-fired boiler conversion for
waste co-firing are addressed to a minor
extent.
Findings
Capital Requirements For
Boiler System Retrofit
As indicated in the preceding section,
one of the baseline assumptions of this
study is that boilers co-firing hazardous
wastes are originally designed to burn one
or more conventional fossil fuels—natural
gas, or oil. Therefore, an initial capital in-
vestment is required to retrofit a boiler for
waste co-firing. This capital investment
can be divided into three components:
(1) addition of waste storage and
feeding equipment,
(2) boiler modification to accommodate
the waste fuel, and
(3) air pollution control device addition
for particulate/HCI removal, if re-
quired by regulation.
The direct capital cost requirements for
boiler retrofit were broken out as follows:
• Waste handling equipment
Tanks (installed)
Pumps (installed)
Piping (installed)
Filters (installed)
• Burner system modification
Equipment
Installation
• APCD additions
Equipment
Installation
Engineering designs and cost data are
provided on waste storage tanks and
transfer lines, as well as boiler nozzles,
complete burner assemblies, and burner
assembly plus blower and controls.
Design specifications and cost for elec-
trostatic precipitators, baghouses, and
venturi scrubbers/acid gas adsorber
systems are also given. To determine
design characteristics of air pollution con-
trol devices (APCD) it was assumed that
the boilers would have to meet standards
for paniculate and hydrogen chloride
emissions that were comparable to those
hazardous waste incinerators.
Cost multipliers are provided for
estimating the following indirect cost:
engineering and supervision, construction
and field expense, construction fee, start-
up, and contingency.
Incremental O&M Cost
Incremental O&M costs for boiler
operation are likely whenever waste,
rather than fuel, is burned. These in-
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cremental costs can include increased
consumption of electric power and water,
higher costs for maintenance and residue
disposal; add-on costs for scrubbing
chemicals, liquid nitrogen, and waste
analysis, plus capital recovery charges.
The full report identifies how boiler
retrofit affects each of these cost com-
ponents and provides typical units costs
for estimating incremental cost increases.
Incremental O&M costs for waste co-
firing in boilers are provided for each of
the following categories: power, water,
caustic, liquid nitrogen, ash disposal,
semivariable costs, operating labor,
maintenance, waste analysis, fixed costs,
capital recovery, and taxes and insurance.
Credits
Finally, the study provides a
methodology for estimating the credits
associated with co-firing hazardous
wastes. This includes the obvious fuel
savings, plus elimination of certain on-site
and/or contractor costs for disposal of
the waste. These credits fall into two
categories: reduced fuel requirements
(due to substitution of waste for fuel),
and elimination of waste disposal costs.
Cost/Credit Summary
Based on total capital investment, an-
nual O&M costs and annual credits the
net annual credit or cost of co-firing with
hazardous waste in boilers can be deter-
mined. Using the annual waste
throughput, an annual unit credit (or cost)
can be determined in dollars per pound of
waste fired.
Example Cases
The full report presents cost/credit
evaluations for two hypothetical co-firing
scenarios. These evaluations are intended
to demonstrate how the information
presented earlier in this report can be
used to assess the economics of hazard-
ous waste co-firing for specific situations.
Although the results indicate that co-firing
is profitable in both cases, no generaliza-
tion concerning co-firing economics is in-
tended.
Case A
The subject of this evaluation is a large
chemical intermediates plant located in
the midwestern U.S. Among the many
wastes and byproducts generated in this
plant is a 2,000 Ib/hr, 14 million Ib/yr
methacrylate bottoms stream with a
higher heating value of 12,000 Btu/lb.
This waste is currently disposed at a near-
by commercial incineration facility at a
cost of 4 cents/lb. Other than its 1% ash
content, however, this waste is a prime
candidate for co-firing in the plant boiler
facility.
This case study addresses the in-
cremental costs and credits associated
with the switch from off-site disposal to
on-site boiler co-firing. Tables 1 and 2
present the pertinent technical and cost
information in summary form; the follow-
ing subsections discuss the methods and
assumptions used to develop this informa-
tion, including the final cost/credit projec-
tions.
From this hypothetical case, waste co-
firing is an attractive alternative to off-site
waste disposal. The fuel savings alone
provide a net credit of nearly $700,000/yr.
Including waste disposal cost elimination,
the annual savings is $1.2 million. This
yields a payback period of less than 1 year
for the initial $1 million investment.
Table 1. Case A—Boiler Design and Operating Characteristics
Parameter
Basic design
Burner system
APCD system
Waste storage
Steam pressure, psig
Steam capacity, Kflblhr
Ave. steam load, KPIb/hr
Heat output, 10'Btu/hr
Mass feed rate, Ib/hr
Fuel
Waste
Total
Volumetric feed rate, gph
Fuel
Waste
Heat input, 10*Btu/hr
Fuel
Waste
Total
Heat input, with waste, %
Boiler efficiency, %
Excess air, %
Fuel
Waste
Total air flow, Jff'lb/hr
Combustion gas temp., °Fa
Combustion gas flow, 1O*lb/hr
10* acfrrf
103 dscfm
Paniculate loading, gr/dscf
ESP inlet
ESP outlet"
Required removal efficiency, %
Annual on-stream time, hrs/yr
Baseline fuel firing
Watertube, balanced draft.
with economizer
4 single register gas/ oil
None
None
250 sat
100.0
80.0
81.1
5,096
0
5,096
637
0
94.3
0
94.3
0
86.0
10
—
77.8
350
84.0
28.5
16.2
—
—
—
7000
Waste co-firing
same
same
ESP (insulated)
1-5000 gal tank
250 sat
99.4
80.0
81.1
3,836
2,000
5,836
480
263
71.0
24.0
95.0
25.3
85.4
10
25
80.5
350
87.4
29.8
16.8
0.14
0.03
78.4
7000
"Economizer outlet temperature.
bApplicable paniculate standard.
Table 2. Case A—Overall Cost/Credit Summary
Item
Cost/credit
Total capital investment
Annual O&M costs
Annual credits
Fuel savings
Waste disposal elimination
Total credit
Net credit
Annual waste throughput
Unit credit
$1,000,000
$ 258,000
$ 937,000
$ 560,000
$1,497,000
$1,239,000
14,000,000 Ib
$0.0885lib
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Case B
The subject of this evaluation is a small
chemical processing plant, also located in
the Midwest. This plant generates approx-
imately 500 Ib/hr (65-70 gph) of liquid
waste, primarily methanol and dirty
solvents, along with a larger quantity of
solid waste. Both the liquid and solid
wastes are currently disposed off-site at
an average cost of 5 cents/lb. However,
the liquid waste is a reasonably good can-
didate for boiler co-firing, despite the- fact
that it contains some chlorine and ash.
Tables 3 and 4 summarize the technical
information, retrofit costs, annual O&M
costs, and credits associated with co-
firing this waste is an on-site boiler for
process steam generation, as an alter-
native to off-site disposal.
In this hypothetical scenario, waste co-
firing is an attractive alternative to off-site
disposal assuming that no significant
boiler maintenance problems are en-
countered. The net annual credit is nearly
$200,000, providing a payback period of
14 months for the initial $230,000 invest-
ment.
However, the payback based on fuel
savings alone is marginal; less than
$20,000/yr or 8.3% return on investment.
This might not justify the initial capital in-
vestment if the waste was initially being
burned in an on-site incinerator, rather
than disposal off-site.
Table 3. Case B—Boiler Design and Operating Characteristics
Parameter
Baseline fuel firing
Waste co-firing
Basic design
Burner system
APCD system
Waste storage
Steam pressure, psig
Steam capacity, lO'lb/hr
Ave. steam load, KPIb/hr
Heat output, IPBtu/hr
Mass feed rate, Ib/hr
Fuel
Waste
Total
Volumetric feed rate
Fuel, JPscfh
Waste, gph
Heat input, 10*Btu/hr
Fuel
Waste
Total
Heat input, with waste, %
Boiler efficiency, %
Excess air, %
Fuel
Waste
Total air flow, lO'lb/hr
Combustion gas temp., °F
Boiler exit
APCD exit
Combustion gas flow, lO'lb/hr
Boiler exit
APCD exit
Combustion gas flow, KPacfm
Boiler exit
APCD exit
Combustion gas flow, Iffidscfm
Paniculate loading, gr/dscf
Boiler exit
APCD exif
Required removal efficiency, %
HCI removal efficiency, %
Annual on-stream time, hrs/yr
Firetube, forced draft
1 gas only
None
None
125 sat
10.0
9.0
9.04
547
0
547
11.9
0
11.9
0
11.9
0
75.8
9.03
550
9.70
4.33
1.80
7000
same
1 gas/liquid fuel
Wet scrubber
1-5000 gal tank
125 sat
9.9
9.0
9.04
325
500
825
7.07
66.7
7.07
5.0
12.07
41.4
74.9
5
20
9.48
550
155 (sat)
10.4
11.5
4.62
3.27
1.92
0.15
0.03
80.0
99.0
7000
'Applicable standard.
Table 4. Case B— Overall Cost/Credit Summary
Item
Total capital investment
Annual O&M costs'
Annual credits
Fuel savings
Waste disposal elimination
Total credit
Net credit
Annual waste throughput
Unit credit
Cost/credit
$ 230.000
t 146,000
$ 165,000
$ 175,000
$ 340,000
$ 194,000
3,500,000 Ib
$0.0554/11)
'Does not include maintenance costs, if any, arising from boiler tube fouling or HCI corrosion.
ou.S.Government Printing Office: 1985 — 559-111/10817
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R. McCormick andL. Weitzman are withAcurex Corporation. Mountain View, CA
94039.
Benjamin L. Blaney is the EPA Project Officer (see below).
The complete report, entitled "Preliminary Assessment of Costs and Credits for
Hazardous Waste Co-Firing in Industrial Boilers," (Order No. PB 85-172
575/AS; Cost: $ 10.00, 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:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
BULK RATE
POSTAGE & FEES PAII
EPA
PERMIT No. G-35
Official Business
Penalty for Private Use $300
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