United States
Environmental Protection
Agency
Hazardous Waste Engineering
Research Laboratory
Cincinnati OH 45268
Research and Development
EPA/600/S7-85/033 July 1986
SEPA Project Summary
Assessment of Energy
Recovery Potential of
Industrial Combustion
Equipment
P. K. Engel, S. C. Hunter, S. S. Cherry, and R. J. Goldstick
An assessment was conducted to
evaluate the waste heat content and
energy recovery potential of flue gases
from 30 industrial combustion devices.
Pollution controls on nine of the
devices were evaluated to estimate en-
ergy requirements and particulate re-
duction; energy requirements were
compared with incremental emissions
at electric utilities supplying power for
the pollution controls. Metal process-
ing furnaces had the highest waste heat
content in the exhaust gas (57%-86%
of fuel heat input). The remaining
devices and waste heat content range
were: Internal Combustion Engines (21
and 38%), Mineral Kilns (11-55%),
Petroleum Process Heaters (14-38%),
Boilers (10-41%), and Gas Turbine
Combined Cycles (15 and 16%). Energy
recovery by combustion air preheat,
process heat utilization, or heat engine
cycles was evaluated on a preliminary
basis and appears to be practical for
many of the devices. Energy require-
ments for particulate emissions control
were found to be less than 2.0 percent
of heat input. The recoverable energy
exceeded pollution control energy in
seven of nine cases by a ratio of from 2
to 49. The particulate reduction on a
mass basis at the industrial facilities
ranged from 7.3 to 23,000 times the in-
cremental mass of total emissions gen-
erated at electric utilities supplying
power to operate the control equip-
ment.
This Project Summary was devel-
oped by EPA's Hazardous Waste Engi-
neering Research Laboratory, Cincin-
nati, OH, to announce key findings of
the research project that is fully docu-
mented in a separate report of the same
title (see Project Report ordering infor-
mation at back).
Introduction
The purpose of this study was to de-
termine the energy recovery potential
and pollution control energy consump-
tion of industrial combustion devices
for which site-specific operation data
had been previously gathered in two
other EPA projects. The study results
are intended to serve as specific exam-
ples of energy usage and waste heat re-
covery potential of these boilers and
process units. It is not intended that
quantitative conclusions that are gener-
ally applicable throughout the industry
could be reached by this study.
The project scope incompassed com-
bustion and emissions data from indus-
trial combustion devices tested under
EPA Contracts 68-02-2144 and 68-02-
2645. These devices consisted of
petroleum process heaters, mineral
kilns, metal processing furnaces, boilers
operating with unconventional fuels, in-
ternal combustion engines and gas tur-
bine cycles.
The full report considers waste
heat recovery for three purposes:
(1) combustion air preheat, (2) process
heat, and (3) heat engine operation. The
analysis determined the amount of
energy recoverable for each purpose,
the capital cost of waste heat recovery,
cost benefits due to fuel savings and ex-
-------
Table 1. Combustion Device Summary
Combustion Location/
Device Unit-Test* Fuel
Petroleum Process
Heaters
(Natural Draft)
(Forced Draft)
Mineral Kilns
Clay
Cement
Cement
Cement
Lime
Metal Processing
Furnaces
Aluminum
Aluminum
Steel OH
Steel Reheat
Steel Soaking
Pit
Boilers
Internal
Combustion
Engines
Gas Turbine
Combined Cycles
4-4
4-6
5/1
5/2
7/1
7/2
7 (2645)*
7 (2645)*
12/1-1
12/1-8
12/2-1
12/2-2
1-1
3-2
9-1 A
9 (2645)*
6 (2645)*
6-1
6-3
14-1
16/1-17
16/2-1
10/1-1
10/2-2
13-6
11-1
19-53
19-97
19-181
200-G-2
200-24
3 (2645)*
5 (2645)*
2-1
15-1
7/3-1
8-1
Gas/Oil
Refinery Gas (RG)
RG
RG
RG
RG
Natural Gas (NG)
NG/No. 6 Oil
RG
RG/No. 6 Oil
RG
No. 6 Oil
NG
Coke
NG
Coal
No. 6
Natural Gas (NG)
No. 2 Oil
NG/No. 6 Oil
NG
NG
Wood/NG
Black Liquor
Wood/Coal
CO/RG
No. 2
No. 6
NG
NG
No. 6
Wood/Coal
Wood/Oil
NG
No. 2 Oil
Refinery Gas (RG)
RG
Heat
Input,
MW
30.9
31.1
18.5
10.1
15.5
15.1
15.9
14.3
22.5
22.5
10.2
10.2
12.4
69.9
61.4
57.1
15.6
6.5
7.1
30.3
24.6
2.3
75.3
140.3
25.5
94.9
5.0
5.8
5.7
11.7
11.2
29.4
78.0
3.2
1.3
202
519.9
Stack
Temp.,
°tf
550
557
478
481
592
780
693
687
396+
398+
563
556
330+
558+
422+
494+
527+
1211
1208
550+
730
1583
533+
425+
478+
589
543
527
538
496t
491 +
489+
513+
622
475
456
499
Pollution
Control
No
No
No
No
No
No
No
No
No
No
No
No
No
Multicyclone
and Baghouse
Electrostatic
Precipitator
No
No
No
No
Electrostatic
Precipitator
No
No
Multicyclone
and Venturi
Scrubber
Electrostatic
Precipitator
Multicyclone
Multicyclone
No
No
No
No
No
Multicyclone
Multicyclone
and Venturi
Scrubber
No
No
No
No
industrial pollution control was effec-
tively reducing national emissions.
Study Limitations
The analyses reported are first order
estimates of the cost-effectiveness of
waste heat recovery techniques and of
pollution control equipment. Because of
this and because the report reflects a
small sample of industrial combustion
units, the results should only be used as
an indication of which combustion
devices are most likely to show benefits
from waste heat recovery. Because
there are many site-specific factors
which can influence the cost-
effectiveness of waste heat recovery.
every combustion unit should be con-
sidered on its own merits. The assess-
ments of pollution control energy con-
sumption and emissions reduction
were based on more limited data and
had to be supplemented in some cases
with estimates. As a result, the control
technology analysis had a higher de-
gree of uncertainty than the analysis of
waste gas energy recovery.
Units Analyzed
Table 1 summarizes the combustion
units which were field tested, showing
the fuels they used, heat input and stack
gas temperatures. The pollution control
devices in use at the facilities are indi-
cated. Column two shows the units lo-
cation and the test run during which the
data were collected, as discussed in full
in the project report.
The test units were chosen because
they were determined to be representa-
tive of those commonly employed by
industry as of 1980. This determination
was made from existing data and from
contacts with manufacturers and trade
associations. In addition, emphasis was
placed upon selecting units within in-
dustries that are most significant in
terms of national emissions of criteria
pollutants and in terms of energy con-
sumption. As a result, energy conserva-
tion at these sites have the potential for
significantly reducing air pollution.
*(2645) indicates devices tested under Contract 68-02-2645, remaining were tested under Con-
tract 68-02-2144.
+This combustion device has an existing heat recovery unit.
istance of a demand for that form of re-
covered energy at the site.
The study also determined the energy
consumption by air pollution control
technologies used on the combustion
units. A comparison was made between
this energy demand and the waste heat
2
recoverable from each unit. In addition,
the amount of air pollutants produced
by an electric power plant in order to
power each industrial pollution control
device was compared with the reduc-
tion in emissions which that device
achieved, in order to determine whether
Analysis Procedure
The waste heat content of the exhaust
gas was determined with reference to
298 K (77°F) with moisture in the flue
gas condensed. Each combustion de-
vise was examined to determine if ex-
haust gas energy recovery is practical,
what recovery methods might be em-
ployed and the percentage of energy re-
covery that should be achievable. For
combustion air preheat and process
-------
heat utilization an exhaust gas tempera-
ture of 400 K (260°F) was assumed,
based on conservative application of
limits recommended by a major heat re-
covery equipment manufacturer1 and
an assessment of the units already
equipped with heat recovery that were
included in this study. For heat engines
a minimum inlet flue gas temperature of
533 K (500°F) and an exhaust gas tem-
perature from the heat engine itself of
416 K (290°F) were taken as typical, as
there is no ambient cold fluid input to
the energy recovery system and the
cold-end corrosion problem is less
severe.
In all cases the lower limit of recover-
able energy was taken to be 0.5
megawatts (MW), as this was consid-
ered a reasonable value to warrant cap-
ital expenditures.
The influence of economics and po-
tential for utilizing the recovered energy
were also analyzed. Installed costs for
waste heat recovery technologies and
the fuel savings that they should
achieve were projected through simple
first-order estimates and presented to
show the relative economic merits
rather than a complete return on invest-
ment. The potential for waste heat uti-
lization (e.g., demand for steam at the
facility) was also determined from infor-
mation on other process units at each
industrial site.
The operating energy requirements
for the pollution control devices were
estimated. These consisted of the direct
energy consumption due to the pres-
sure drop across the device and the pe-
ripheral equipment energy requirement
associated with pumps, waste removal
and disposal.
The emissions reductions were calcu-
lated by measuring flue gas paniculate
concentrations either upstream or
downstream of the control device and
then estimating device efficiency. The
reduction in pollutants at the site was
compared with the emissions gener-
ated at a power plant due to the electri-
cal energy requirement of the control
device.
Findings
Metal processing furnaces had the
highest heat content in the exhaust gas
(57-86% of fuel input). The remaining
units and waste heat content ranges
were: internal combustion engines (21
and 38%), mineral kilns (11-55%),
petroleum process heaters (14-38%),
'Sales literature from the C-E Air Preheater Com-
pany, Wellsville, New York.
boilers (10-41%) and gas turbine com-
bined cycles (15 and 16%). Heat recov-
ery by combustion air preheat and proc-
ess heat utilization were found to be
practical for many devices, but heat en-
gine cycles had much less potential. De-
tails on amounts of recoverable energy
are provided in Table 2. Cost savings
and potential for waste heat utilization
are discussed in the project report.
Energy requirements for particulate
emissions control were found to be less
than 2.0 percent of heat input. The par-
ticulate reduction on a mass basis at the
industrial facility ranged from 7 to
23,000 times the emissions from a ther-
mal power plant which generated the
electricity to operate the control tech-
nology equipment. The energy recovery
potential exceeded pollution control en-
ergy in seven of nine cases by a ratio of
from 2 to 49.
Conclusions
Based on the analysis of this limited
number of units, the following conclu-
sions regarding the potential for energy
recovery of stack gas waste heat can be
drawn.
1) Stack gas temperatures are suffi-
ciently high (up to 1583 K) on
many industrial devices to provide
good potential for energy recov-
ery.
2) Some industrial devices have little
potential for energy recovery due
either to low stack gas tempera-
tures or low gas flow rates.
3) Where stack gas energy recovery
appears feasible, the recovery po-
tential ranges from 1.4 to 76 per-
cent of the fuel heat input, depend-
ent on stack temperatures and
recovery method.
4) Metal processing furnaces provide
the best potential for energy re-
covery, ranging from 34 percent to
76 percent of fuel heat input.
5) Internal combustion engines and
gas turbine combined cycles ap-
pear to have the least potential for
energy recovery.
6) Recovery of waste heat by process
hot water or steam appears to
offer the highest potential for en-
ergy recovery.
7) Combustion air preheat appears
somewhat less favorable com-
pared to process heat but is fre-
quently employed because it does
not require an external process in
which to absorb the recovered
heat.
8) Thermodynamic heat engine cy-
cles do not appear favorable com-
pared to process heat o'r air
preheat.
The following conclusions were
drawn with regard to the pollution con-
trol device effectiveness and energy
penalty for the units examined:
1) The emissions reduced at indus-
trial plants are considerably
greater than the emissions gener-
ated at power plants to operate the
control equipment.
2) The energy recovery potential at
industrial plants was considerably
greater than the energy require-
ment for most pollution control
devices.
Recommendations
As a result of this study, further re-
search should be considered in the fol-
lowing areas.
1) Application of waste heat recovery
on metal processing furnaces as
this has the greatest potential for
energy efficiency improvement.
2) Use of process heat as an option
for waste heat recovery as com-
pared with combustion air pre-
heating, with emphasis on the
petroleum industry.
3) Comparison of the results of this
study with other studies of indus-
trial energy use to improve the as-
sessment of nationwide potential
for industrial energy recovery.
4) Expansion of the study of pollution
control energy to include SOx re-
moval equipment and additional
particulate removal sites.
-------
Table 2, Summary of Waste Energy Recovery Analysis
Location/
Combustion Device Unit - Test Fuel*
Petroleum Process Heaters
(Natural Draft)
(Forced Draft)
Mineral Kilns
Clay
Cement, Dry Process
Cement, Wet Process
Cement, Wet Process
Lime
Metal Processing Furnaces
Aluminum Melter
Aluminum Melter
Steel Open Hearth
Steel Reheat
Steel Soaking Pit
Boilers
Internal Combustion
Engine
Gas Turbine
Combined Cycles
4
4
5/1
5/2
7/1
7/2
7 (2645)
7 (2645)
12/1-1
12/1-8
12/2-1
12/2-2
1-1
3-2
9-1 A
9 (2645)
6 (2645)
6-1
6-3
14-1
16/1-17
16/2-7
10/1-1
10/2-2
13-6
11-1
19-53
19-97
19-181
200-G-2
200-24
3 (2645)
5 (2645)
2-1
15-1
7/3-1
8-1
Gas/Oil
RG
RG
RG
RG
RG
NG
NG/No. 6
RG
RG/No. 6
RG
No. 6
NG
Coke/NG
NG
Coal
No. 6
NG
No. 2
NG/No. 6
NG
NG
Wood/NG
Blk Liq.
Wood/Coal
CO/KG
No. 2
No. 6
NG
NG
No. 6
Wood/Coal
Wood/Oil
NG
No. 2
RG
RG
Fuel
Heat
Input,
MW
30.9
31.1
18.5
10.1
15.5
15.1
15.9
14.3
22.5
22.5
10.2
10.2
12.4
68.9
61.4
57.1
15.6
6.5
7.1
30.3
24.6
2.3
75.3
140.3
25.5
94.9
5.0
5.8
5.7
11.7
11.2
29.4
78.0
3.2
1.3
202
519.9
Stack
Temp.,
K
550
557
478
481
592
780
693
687
606
546
563
556
300
558
422
455
527
1211
1208
550
730
1583
533
425
478
589
543
527
538
496
491
489
513
622
475
456
499
Waste
Heat
Content,
%
24.3
24.1
20.5
13.9
27.1
38.4
25.2
23.5
20.4
16.0
35.3
20.6
11.3
12.9
55.0
45.7
18.8
60.6
61.5
60.0
56.8
86.3
40.9
23.4
22.4
51.0
23.5
15.1
24.8
10.2
12.9
17.1
19.5
38.2
21.4
15.3
16.1
Technically Applicable Energy
Recovery Techniques
Recoverable Energy, MW
Air Preheat
2.1
2.2
0,7
(0.3)
1.4
2.5
1.8
1.6
2.8**
3.1*'
0.6
0.7
—
—
—
—
—
1.5
2.2
—
2.6
1.0
6.5
—
1.1
6.1
(0.3)
(0.3)
(0.3)
(0.5)
0.6
1.3
6.6
—
—
—
—
Process Heat
2.4
2.3
0.7
(0.3)
1.7
3.3
2.2
2.0
1.9
1.4
0.9
0.8
—
3.2
0.9
2.2
1.4
2.8
3.4
—
8.4
1.7
7.5
—
1.2
16.7
(0.3)
(0.3)
(0.3)
(0.4)
(0.4)
1.5
4.9
(<0.5)
«0.5)
4.3
17.4
Heat Engine
(0.5)
(0.5)
—
—
(0.3)
0.7
(0.5)
(0.4)
(0.4)
(0.3)
(0.2)
(0.2)
—
0.6
—
—
—
0.6
0.7
—
1.8
0.4
—
—
—
3.4
(0.1)
—
(0.1)
—
—
—
—
«0.5)
—
—
—
*RG = Refinery Gas, NG = Natural Gas, Blk Liq. = Black Liquor,
() = Recoverable energy less than 0.5 MW.
— = Temperatures too low for recovery.
** = This heat recovery method is an existing installation.
ft U.S. Government Printing Office: 19i6—646-116/40617
CO = Carbon Monoxide.
-------
P. K. Engel. S. C. Hunter, S. S. Cherry, andR. J. Goldstickare withKVB, Inc., Irvine,
CA 92714.
Benjamin L. Blaney is the EPA Project Officer (see below).
The complete report, entitled "Assessment of Energy Recovery Potential of
Industrial Combustion Equipment," (Order No. PB 85-245 959/AS; Cost:
$11.95, 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
EPA/600/S7-85/033
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