vxEPA
United States
Environmental Protection
Agency
Industrial Environmental Research
Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S7-81 -169 August 1982
Project Summary
Emissions from Refinery
Process Heaters Equipped with
Low-NOx Burners
R. J. Tidona, H. J. Buening, and J. R. Hart
This report summarizes results of an
investigation of the performance of
commercial Iow-N0x burners in refin-
ery process heaters. Refineries in
Southern and Central California were
surveyed to determine the number of
low-NOx burner installations existing
or planned. Ten process heaters, equip-
ped with low- N Ox burners, were tested
to measure gaseous emissions, partic-
ulates, and efficiences over a normal
range of operating conditions. The as-
found NOX emission increased from
58 to 245 ng/J as the fuel-bound
nitrogen increased from 0 to 0.81
percent. The NOX concentrations were
strongly influenced by excess air levels
in most cases. Reducing excess air to
about 3-4 percent reduced NOxto 34-
200 ng/J, depending on fuel nitrogen.
Comparisons of present emissions
data with past field test data for
refinery heaters equipped with stan-
dard burners showed that for mechan-
ical-draft gas-fired heaters, low-NOx
burners may reduce the NOX emission
factor by 32-77 percent below the
mean emission factor for standard
burners. Three heaters (one firing gas,
another firing distillate oil, and the
third firing residual oil) were selected
as suitable candidates for 30-day
continuous monitoring of gaseous
emissions.
This Project Summary was devel-
oped by EPA's Industrial Environmen-
tal 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
Approximately 6000 refinery process
heaters are in operation in the United
States (Ref. 1). Of these, about 5400
have natural draft burners; the remain-
der have forced or balanced draft
burners. Both types emit a total of about
121.5 Gg/y (134,000 tons/y) of NO,,
making process heaters one of the
largest industrial emitters of this pollu-
tant.
Several field test programs have been
conducted to characterize NO* emis-
sions from process heaters over a wide
range of operating conditions. However,
all the previous field test work was
conducted on heaters equipped with
conventional burners. Only recently
have refinery heater burner manufac-
turers begun to market low-NOx burners
for the petroleum industry, and new
commercial installations are somewhat
sparse.
It was the purpose of this program to
(1) locate refineries in Southern Cali-
fornia which have installed or ordered
low-NOx burners, (2) test nine gas- or
oil-fired process heaters in which low-
NOx burners have been installed (NO,
and other gaseous emissions were to be
measured over a normal range of oper-
ating conditions), and (3) assess the
potential for long term (30-day) tests of
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the heaters with the goal of finding
three suitable sitesone firing gas, a
second firing distillate oil, and the third
firing residual oil.
Southern California was selected for
the heater survey because of its strict
NOx emission regulations; hence, a high
likelihood of finding installations with
low-NOx burners. Results of the survey
are summarized in Table 1. At least 29
heaters were found with low-NOx
burners installed or planned for instal-
lation. Heaters which were tested in this
program were assigned the site num-
bers shown in Table 1.
Results of the tests conducted at these
10 sites are reported here. (Site 10 was
added to the required nine because it
was near Sites 6 through 9 and the
refinery was willing to allow it to be
tested.)
Summary of Program Results
and Comparison with Past
Results
This program required that baseline
tests be conducted for nine refinery
process heaters equipped with low-NOx
burners. Tests were completed on 10
process heaters, since one extra could
be tested for minimal additional cost.
At each test site, the gaseous emis-
sions and stack gas temperature were
measured. Samples of fuel were taken
and submitted to an independent labora-
tory for analysis. Unit operational data
such as flow rate, pressure, and tem-
perature were recorded periodically.
After testing the unit in the as-found
condition, burner registers and/or stack
dampers were adjusted to determine
the effect of excess oxygen on unit
operation, gaseous emissions, and
heater efficiency.
The heaters tested included four
natural draft and six mechanical draft
units firing gas, distillate, and residual
oils. Four of the mechanical draft units
had preheated combustion air.
Emission Test Methods and
Instrumentation
All emission measurement instru-
mentation was carried in a 2.4 x 12.8 m
(8 x 42 ft) mobile laboratory trailer. Thi
trailer was used at all test sites. Gaseou
species were measured with analyzer
in the trailer. The emission measure
ment instrumentation used is listed ii
Table 2.
Results
Figure 1 shows NOx emissions as i
function of stack oxygen for the 11
process heaters tested. These data shov
that for all heaters, lowering the oxygei
resulted in lower N0» emissions. Th<
gas-fired heaters had lower NO, emis
sions than did the distillate-oil-firei
heater, and the residual-oil-fired heater:
had the highest NOx emissions. Thi
gas-fired heaters with combustion ai
preheat had higher NO, emissions thai
gas-fired heaters with ambient combus
tion air. The points at which significan
CO emissions or visible smoke occurrei
are marked in the figure as "CO limits.'
Gas-fired heaters with ambient com
bustion air showed NOx emissions a<
40-50 ng/J (80-100 ppm at 3 percent
Table 1. Heater Low NOK Burner Test Site Survey
Location
A
B
C
D
E
F
G/i
G/2
H
1
J/1
J/2
K
L/1
L/2
M
N
0/1
O/2
P
Site
No.
2
-
-
-
_
-
6, 7,
8,9
10
-
-
-
-
7
4
3
5
-
-
-
-
Air
Quality
Control
Region
31
31
24
24
24
31
30
30
24
31
24
24
24
31
31
31
24
30
30
31
No.
Heaters
1
1
-
-
1
11
4
1
1
1
1
1
1
1
1
1
-
1
1
-
Heat Input Rate
106
MW Btu/Hr
4.7
16.4
-
-
7.5
-
93.8°
8.8
7.7
10.3
-
-
6.1-6.7
6.7
11.7
11.7
-
21.4
6.4
-
~ 16
56
-
-
25.7
-
320
30
26.4
35
-
-
21-23
22.9
39.9
40
-
73
22
-
Burners
1
8
-
-
4
-
32
1
8
3
-
-
3
3
12
10
-
-
-
-
Operational
Yes
Yes
-
-
Dec. 8O-
Jan. 81
-
Sept. 80
Sept. 80
Jan. 81
March 81
Jan. 81
Jan. 81
Yes
Yes
Yes
Yes
-
Yes
Yes
-
Fuel
LO-S resid
6 Gas, 2 Oil
-
-
Gas
-
Gas
Gas
-
#6 Oil
Gas
Gas
Gas
#5 Oil, gas
#5 Oil, gas
#£+/?G
-
Gas
Gas
-
Comments
Natural Draft
Old heater; leaks above firebox
Natural Draft
Preheat, Balanced Draft
Ambient, Forced Draft
Natural Draft
Natural Draft
Natural Draft
Forced Draft
Natural Draft
Natural Draft
Natural Draft
Natural Draft
Natural Draft
aTotal for four heaters.
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02, dry*) in the as-found condition. By
lowering the excess oxygen to a CO limit
or to the minimum acceptable condition
as determined by the plant, NO* emis-
sions were reduced to about 25 ng/J
(50 ppm). Heaters with preheated com-
bustion air showed as-found NO* emis-
sions as 58-76 ng/J (115-150 ppm).
Lowering excess oxygen resulted in
NO, reduction to 25-43 ng/J (50-85
ppm).
As-found NO emissions from a natural-
draft distillate-oil-fired process heater
were 92-117 ng/J (168-212 ppm) and
were reduced to approximately 58 ng/J
(105 ppm) by lowering excess air to the
single burner.
Emissions in the as-found condition
were considerably higher for the three
units firing residual oil. All were natural
draft units, and two were found to be
emitting 207-281 ng/J (370-500 ppm)
of NO. The unit at Site 5 fired 15-20
percent refinery gas simultaneously
with residual oil. This unit was found to be
emitting 194-205 ng/J (350-370 ppm)
of NO and was the only unit firing
residual oil which showed a significant
tendency toward reduced emissions
when excess air levels were lowered. At
reduced excess air settings, this unit
produced about 166 ng/J (300 ppm) of
NO.
Table 3 is a summary of gaseous
emissions and efficiency for each site
tested. Emissions at as-found conditions
and at optimum low-NO* conditions (i.e.,
lowest NOx emission without adverse
effects on flame stability or unit effi-
ciency) are compared in this table. At
most sites, significant reductions in NO*
emission below as-found levels could
be achieved along with small increases
or, at worst, no change, in efficiency.
With respect to flame stability, product
flows and temperatures, and emissions
of CO and unburned hydrocarbons, unit
operations at the optimum Iow-N0x
conditions were generally unchanged
from the as-found conditions.
Figure 2 is a plot of the effect of fuel-
bound nitrogen content on the NO,
emission factor. The three circles plotted
in this figure represent data from the
oil-fired units tested. Site 2 burned 100
percent No. 2 oil; Sites 3 and 4, No. 6 oil
(both units burned fuel having the same
composition); Site 5, a combination of
80 percent No. 6 oil (by heat input rate)
and 20 percent refinery gas. The "zero
*AII emission concentrations given as ppm are
corrected to 3 percent 02, dry basis.
Table 2. Emission Measurement Instrumentation
Species Manufacturer Measurement Method Model No,
Hydrocarbon
Carbon Monoxide
Oxygen
Carbon Dioxide
Nitrogen Oxides
Particulates
Sulfur Dioxide
Beckman Instruments
Beckman Instruments
Teledyne
Beckman Instruments
Thermo Electron Co.
Joy Manufacturing Co.
DuPont Instruments
Flame lonization
IR Spectrometer
Polarographic
IR Spectrometer
Chemiluminescent
EPA Method 5 Train
UV Spectrometer
402
865
326A
864
10A
EPA
400
500
400
£300
I
d
^ 200
100
I-Site 4
'Residual Oil
Natural Draft
Site 3
Residual Oil
Natural Draft
-Site 5
fS Residual Oil/RG
xv/' Natural Draft
0
Figure 1.
468
Stack Oxygen, % Dry
Site 2
Distillate Oil
Natural Draft
Site 6-9
Refinery Gas
Balanced Draft
Site 10
Refinery Gas
Forced Draft
Site 1
NG/RG
Forced Draft
RG = Refinery Gas
NG = Natural Gas
= Denotes as-found cond.
10
12
14
NOX emissions as a function of stack oxygen for Iow-N0x burners in
process heaters.
3
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Table 3. Optimum Low-N0x and As-Found Gaseous Emissions and Efficiencies at 10 Heaters Equipped withLow-NOxBurners
As-Found Optimum Low-N0x
Site
1
2
3
4
5
6
7
8
9
10
Heater' Test Nos.
Config. (A.F.:Low-NOx)
121 1-13; 1-24
211 2/1-1e;2/1-3a
311 3-1:3-3
311 4-1:4-4
411 5-3:5-6
132 6/5-3:6/5-1
132 7/1-1:7/2-2
132 8/1-1:8/1-3
132 9/1-1:9/1-3
121 10/1-1; 10/1-4
3Heater configuration designations
1st Digit
Fuel Burned
1 = gas
2 = dist. oil
3 = residual oil
4 = combined oil
&gas
NO
(ng/J)
39.0
92.4
222.0
268.0
194.0
57.9
65.8
74.9
60.2
51.6
are:
NO 02
(ppm) (%)
77 6.2
168 5. 1
396 5.2
477 8. 1
352 7.7
114 4.8
130 5.3
148 7.7
119 8.4
102 6.7
2nd Digit
Draft Type
1 = natural
2 = forced
3 = balanced
CO
(ppm)b
0
11
11
0
11
11
11
14
0
13
Htr.
Eff.
(%)
79.9
64.0
63.4
67.9
69.8
68.0
65.4
66.4
73.1
NO
(ng/J)
24.0
80.4
203.0
264.0
167.0
38.1
35.4
41.0
32.9
32.9
NO
(ppm)
48
145
361
471
303
75
70
81
65
65
02
(%)
3.0
4.0
4.3
7.1
4.4
3.5
2.3
3.8
3.3
2.8
CO
lppm)b
20
11
11
0
22
11
33
15
10
10
Htr.
Eff.
(%)
83.0
64.0
64.5
68.6
71.3
68.5
69.2
68.8
74.4
%NO
Reduction
38.5
13.0
8.5
1.5
13.9
34.2
46.2
45.3
45.3
36.2
3rd Digit
Air Temp.
1 =
2 =
ambient
preheater
bDry, corrected to 3%02.
Fuel Bound Nitrogen, Percent by Weight
Figure 2. Fuel-bound nitrogen effect on NOX emission factor.
level" or base HO* emission factor for
gaseous fuel (containing no fuel-bound
nitrogen) was computed by taking the
average as-found NOX emission factor
for all sites firing gas fuel only. This
value was 58 ng/J. The increase. A, in
emission factor for No. 2 oil was 34
ng/J (as found). For No. 6/gas fuel, the
increase over the gas fuel emission
factor was 136 ng/J (as found). For No.
6 oil, A was 187 ng/J (as found).
Comparing these points to the curve
fit of previous laboratory data (Figure 2),
shows that in all cases the emissions
from low-NOx burners fall below that
curve. It is interesting to note that
operation at the optimum low-NOx mode
(represented by squares in Figure 2) did
not significantly alter the fuel-bound
nitrogen conversion to NO,. Also, except
for Site 2, in the as-found condition all
points plotted in Figure 2 fall within the
bounda ry curves for the laboratory data.
The effect of fuel nitrogen on NOx
emissions is thus responsible for the
large differences in emissions between
gas- and oil-fired heaters shown in
Figure 1.
Table 4 summarizes NO emissions
from the heater configurations studied
over the tested range of operating
variables. The values reported in paren-
theses are ppm corrected to 3 percent
Oz, dry. (NOz emissions were not in-
cluded due to lack of data at some sites.
The data available from Sites 6-10,
however, show that the NOz emissions
average only 3.6 percent of the total NO,
emissions.)
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Past Results - Comparison to
Present
Reference 2 summarizes past NOx
emissions data on refinery process
heaters firing oil and gas. These data are
presented in Table 5. Unfortunately, the
paucity of baseline data from oil-fired
process heaters with standard burners
makes it difficult to compare them with
present Iow-N0x burner data. Mechan-
ically drafted heaters with low-NOx
burners firing gas, however, appear to
have significantly lower NO, emissions
relative to the standard burners. Tables
4 and 5 reveal that low-NO. burners
produced NO* emissions (neglecting
NOz) which were 32-77 percent less
than the average emission factor for all
standard burners on mechanical-draft
gas-fired heaters. The variations in NO*
emissions from low-NOx burners were
due to operating differences between
units (e.g., excess air level and air
register settings). It is important to note
that there is no NO, data available on
a ny of the units tested for operation with
standard burners. Thus, NO, emissions
with and without low-NO, burners
cannot be compared directly for any
heater. Because of a lack of availability,
no natural-draft gas-firing low-NOx
burners were tested; hence, they cannot
be compared with their standard counter-
parts.
Conclusions and
Recommendations for Future
Testing
The following conclusions may be
drawn from the study:
1. The effectiveness of low-NOx burn-
ers depends on operating tech-
niques, especially excess air level
and air register settings.
2. By changing excess air and air
register settings, NO, emissions
were reduced at every site with
improved overall heater perform-
ance.
3. Commercially available low-NOx
burners may reduce the NO, emis-
sion factor by 32-77 percent below
the average emission factor for
standard burners on mechanical-
draft gas-fired heaters, depending
on operating techniques.
4. Because of the lack of a good data
base for oil-fired heaters with
standard burners, a meaningful
comparison of the performance of
low-NOx oil-fired burners versus
Table 4. NO Emissions from Process Heaters with Low-NOx Burners (1)
Fuel Type
Unit Type
Gas (Ref. or NG)
Distillate Oil
Residual Oil + Gas
Residual Oil
Natural Draft
,"9*,
58_j 77 21(105-212 ppm) 167-202.(303-366ppm) 207-284^(369-506ppm)
J J J
Forced Draft, co^/c* m? nnm>
AmbientAir 26-52-2(51-102 ppm)
Balanced Draft, _ -,.,n9 ,.-n , ,0 ,
AirPreheat 25-75^(50-148 ppm)
aRatio of heat input from oil to heat input from gas = 83/ J 7.
Table 5. Mean NOX Emissions from Process Heaters with Standard Burners
Fuel Type
Unit Type Gas (Ref. or NG)
Distillate Oil
Residual Oil + Gas
Residual Oil
Natural
60.6 (25 tests)
Mechanical
111 "J! (6tests)
J
89.6 22 (5 tests)
138 ^-(3 tests)
\J
Not Reported
(Bay Area
A.P.C.D.)
70.022 (64 tests)
\J
Not Reported
(AP-42)
95 (8 tests)
ng
198 (4 tests) - oil - firing only; type unspecified
'Ratio of heat input from oil to heat input from gas 60/40.
-------
standard oit-fired burners cannot
be made at this time.
5. It is recommended that further
testing include mechanical-draft
oil-fired heaters with and without
air preheat and equipped with
low-No, burners as well as natural-
draft gas-fired heaters equipped
with low-NO, burners.
6. Existing data on heaters with
standard burners have a number
of gaps (see Table 5); further
testing is required on standard
burners firing distillate oil (both
natural- and mechanical-draft)
and standard burners firing resid-
ual oil (natural-draft) for a more
valid comparison with Iow-N0x
burners.
7. Each test site in the program was
evaluated as to its potential for a
30-day test. Considerations in-
cluded:
Fuel type fired.
Ability to fire this fuel independ-
ently of other fuels.
Availability of the heater and
the desired fuel for 30-40 days.
Based on these considerations,
the following sites are proposed
as desirable for 30-day tests:
Site 1 - gas-fired, forced-draft
Site 2 - distillate-oil-fired,
natural-draft.
Site 4 - residual-oil-fired,
natural-draft.
Although Sites 6 through 10 are all
gas-fired mechanical-draft heaters, they
are not desirable sites for a 30-day test
because they are still experiencing
start-up problems; i.e., availability prob-
lems. Site 5, firing a combination of gas
and oil, does not satisfy the fuel specific-
ity requirement. Sites 3 and 4 are both
residual-oil-fired natural-draft heaters,
but Site 4 is a vertical cylindrical heater
similar to the other recommended sites.
Because of this similarity in design. Site
4 is the better choice.
The influence of heater design on NO,
emission between the three candidate
sites will thus be minimal. Since none of
the residual oil tests provided low NO*
levels, it may be desirable to try to find a
site which can achieve lowr NO, levels.
References
1. Hunter, S. C. et al., "Application of
Advanced Combustion Modifica-
2.
tions to Industrial Process Equip-
ment: Subscale Test Results,"
USEPA, Industrial Environmental
Research Laboratory, Research
Triangle Park, NC (Draft No. IERL-
RTP-1271).
Hunter, S. C. and Cherry, S. S.,
NOjL Emission from Petroleum
Industry Operations. API Publica-
tion No. 4311, American Petroleum
Institute, Washington, DC, October
1979.
R. J. Tidona, H. J. Buening, andJ. R. Hart are with KVB, Inc., Irvine, CA 92714.
Robert E. Hall is the EPA Project Officer (see below).
The complete report, entitled "Emissions from Refinery Process Heaters
Equipped with Low-NO* Burners,"(Order No. PB 82-231 838; Cost: $16.50,
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:
Industrial Environmental 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
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Fees Paid
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Agency
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Penalty for Private Use $300
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