United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park, NC 27711
Research and Development
EPA/600/S7-86/005 May 1986
Project Summary
Environmental Assessment of
NH3 Injection for an
Industrial Package Boiler
C. Castaldini, R. DeRosier, and L R. Waterland
This report discusses emission results
from comprehensive flue gas sampling of
a gas- and oil-fired industrial boiler
equipped with Exxon's Thermal DeNO,
Ammonia Injection Process for NOX reduc-
tion. The objective of the tests was to
evaluate criteria and noncriteria pollutant
emissions in the flue gas during a baseline
(uncontrolled) and a low-NO, condition
with ammonia injection. The test boiler
was a 7.57 kg/s (60,000 Ib/hr) watertube
unit equipped with sidefire air and Ther-
mal DeNOx. Comprehensive emission
measurements included continuous
monitoring of flue gas emissions; source
assessment sampling system (SASS)
testing with subsequent laboratory
analysis of samples to give total flue gas
organics in two boiling point ranges,
specific quantitation of semivolatile
organic priority pollutant species, and flue
gas concentrations of 73 trace elements;
EPA Method 5/17 for solid and conden-
sible particulate emissions and ammonia
emissions; controlled condensation
system for SO2 and SO3; and N2O emis-
sion sampling.
Comparison of the baseline and con-
trolled emission results showed that am-
monia injection at a NH3/NO molar ratio of
2.52 gave a NO, reduction of 41 percent
from an uncontrolled level of 234 ppm to
a controlled level of 137 ppm (corrected
to 3 percent 02). NH3 emissions increased
from 11 ppm for the baseline to an average
of 430 ppm for ammonia injection. Nitrous
oxides, N2O, was reduced 68 percent from
a 50 ppm baseline level to a 17 ppm con-
trolled level. Total particulate emissions in-
creased by an order of magnitude from a
baseline of 17.7 ng/J (0.042 lb/10* Btu)
to a controlled level of 182 ng/J (0.43
lb/106 Btu). This increase is in part attri-
buted to formation of ammonia surfate and
bisulfate from residual ammonia and SO,.
Total organic emissions were at a mod-
erate level and showed a relative concen-
tration in the nonvolatile category (boiling
point greater than 300 °C). Organic emis-
sions were lower by a factor of five with
ammonia injection. Emissions of carbon
monoxide and trace inorganic elements
were not significantly affected by am-
monia injection.
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 docu-
mented in two separate volumes (see
Project Report ordering information at
back).
Introduction
Increasing stringency in stationary
source NO, emissions regulations has
created applications for advanced control
technologies. Over the past 5 years, the
Exxon Thermal DeNO, selective non-
catalytic reduction process has been in-
stalled in a number of process heaters and
boilers to augment NO, reduction from
combustion modification at a lower cost
than selective catalytic reduction. This
process reduces NO, through the gas-
phase reaction with ammonia in the
temperature range of 870 to 1,200 °C
(1,600 to 2,200 °F). NO, reduction as high
as 60 to 70 percent has been achieved in
some industrial applications. The reduc-
tion efficiency is affected by the NH3 feed
rate relative to NO, concentrations, by the
degree of flue gas thermal stratification in
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the ammonia injection section, and by the
flue gas residence time within the ap-
propriate temperature window. Potential
emission side-effects of the process in-
clude the presence of unreacted ammonia
in the flue gas and the formation of am-
monium sulfates for sources fired with
sulfur bearing fuels. Few data have been
reported on the effects of full-scale am-
monia injection on emissions of other
inorganic and organic species. This test
was undertaken to perform a comprehen-
sive emission characterization of the boiler
with and without ammonia injection to
supply data on overall emission impacts of
the process. This test was conducted as
part of the Combustion Modification
Environmental Assessment Program under
which similar tests have been performed
on 17 boilers, process heaters, and
engines.
Summary and Conclusions
Source Description
The boiler tested was a packaged
two-drum Zurn Keystone watertube unit
equipped with an economizer and a rated
capacity of 7.57 kg/s (60,000 Ib/hr) of
superheated steam at 2.51 MPa (350 psi)
and 260°C (500 °F). The boiler was
equipped with a single ammonia injection
grid to mix ammonia with the combustion
gases in the appropriate temperature win-
dow. Steam was used as the ammonia car-
rier. Hydrogen injection with the ammonia
was also available to lower the effective
temperature range for use at low load
operation.
Test Program
Two tests were performed: a baseline
uncontrolled run, and an ammonia injec-
tion controlled run. Boiler steam flowrate
was about 4.0 kg/s (32,000 Ib/hr) for both
tests, corresponding to a total steam in-
put of about 13 MW (45 million Btu/hr).
The boiler was fired with refinery gas and
residual oil. Refinery gas supplied 44 per-
cent of the total heat input. Ammonia in-
jection rates for the controlled test were
1.53 g/s (12.1 Ib/hr) corresponding to a
NH3/NO molar ratio of 2.5.
The program for emission measure-
ments at the two test conditions con-
formed to a modified EPA level 1 protocol.
In addition, NH3 flue gas emissions were
measured to calculate the amount of
unreacted NH3 being emitted under the
boiler and control system parameters
investigated. Flue gas was measured at
the stack downstream of the boiler econo-
mizer where the gas temperature was
about 188 °C (370 °F). Flue gas measure-
ments included:
• Continuous monitors for NO* CO,
CO2, and O2.
• Source assessment sampling system
(SASS) train sampling for organic and
inorganic pollutant species.
• EPA Method 5 with water impingers
and an EPA Method 17 backup for
solid and condensible particulate
mass emissions.
• Controlled condensation system
(CCS) for S02 and S03
• Grab sample for onsite analysis of
gaseous C, to Ce hydrocarbons by
gas chromatography.
• EPA Method 17 with HCI impinger
solutions for ammonia sampling.
In addition to this detailed test program,
short-term tests (varying NH3/NO molar
ratio, hydrogren injection, and oil/gas fuel
ratio) were performed. The objective of
these short-term tests was to map the per-
formance of the Thermal DeNO, Process
over a wide range of system and boiler
operating parameters. Measurements for
these short-term tests were confined to
continuous monitoring of O2 and NO«.
Emission Measurements and
Results
Results of the short-term performance
tests are summarized in Figure 1. Baseline
NOX emissions averaged 235 ppm at 3 per-
cent O2 for two oil/gas fuel mixtures in-
vestigated. The results show that NOX
reduction for a given NH3/NO ratio de-
pends on the fuel mixture. The system was
less effective at the oil/gas ratio of 56/44
percent than at the lower oil/gas ratio of
37/63 percent (closer to the typical opera-
tion of the unit and the design basis for
the NH3 injection grid installed). The ad-
dition of hydrogen did not improve system
performance at the lower oil/gas ratio, but
resulted in significant, further NO. reduc-
tion to levels below 100 ppm at the higher
oil/gas ratio. With the higher oil/gas ratio,
boiler convective section gas temperatures
are lower at the grid location, thereby
decreasing the effectiveness of NH3 alone.
For both fuel mixtures, the NO, reduc-
tion performance appears to peak at a
NH3/NO ratio of about 2.5 with little or no
additional reduction gained with further in-
crease in NH3 injection rate.
Table 1 summarizes criteria and other
gas species emissions measured during
the two comprehensive tests. NH3 injec-
tion, at a rate of 2.52, resulted in a 41 per-
cent N0» reduction. CO emissions showed
no significant change. Indications of higher
Legend
Boiler heat input =~13 MW (45 million Btu/hr)
Stack 02 = 2.5 to 2.8 percent
O 44 percent refinery gas
56 percent residual oil
63 percent refinery gas
37 percent residual oil
Hydrogen injection; numbers
specify Hi/NHy molar ratio
if known
Test point for detailed
emission measurements
1.0 1.5 2.0 2.5 3.0
NHs/NO (molar ratio, based in inlet NO)
Figure 1. Thermal De /V0« performance on the packaged industrial boiler.
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Table 1. Criteria and Other Gas Species Emissions
Pollutant
As measured by:
Continuous gas
analyses
O2, percent
CO 2, percent
NOX, ppm
f\f\ _ _ __
CO, ppm
Wet chemical
methods
SO2, ppm
SO3, ppm
NH-i, ppm
Offsite gas
chroma tography
N2O
Onsite gas
chroma tography
Cj, ppm
Co, ppm
C3, ppm
€4, ppm
Cg, ppm
C6, ppm
Corrected emissions ppm0
/VOX« 254
CO 30
SO2 NA
SO3f NA
NHji 11
N20 52
c,
C2
C3 2.5
C4
cs
C6
Total C1 to Ce 2.5
Paniculate mass Emissions:
Method 5/17 solid -
Method 5/17 -
con dGnsible
inorgdnic
Method 5/17 -
condensible
organic
Method 5/17 total —
SASS solid -
aNH3 emissions ranged from 3 to
bNH3 emissions ranged from 280
°Dry ppm at 3 percent O2
dOn heat input basis
eAs NO2
'As H2SO4
sArithmetic average
NA — Sample lost in transit
ND — Not detected
Test 1
(baseline!
2.6
11.7
239
Of
J/
NA
NA
11a
53
ND
ND
2.6
ND
ND
ND
ng/jo
115
9.0
NA
NA
2.0
25
1.3
—
_
1.3
4.6
10.0
2.9
17.7
2.2
25 ppm from
Test 2
(NH3 injection)
2.5
11.6
141
Oyf
-i4
82
13
44Ob
77
0.8
0.6
ND
6.2
5.1
5.0
lb/106 Btuf ppm ng/J lb/106 Btu
0.268 137 67 0.16
0.02 23 6.9 0.02
NA 80 55 0.13
NA 13 13 0.03
0.005 430 78 0.18
0.056 17 8.0 0.019
0.8 0.15 0.0003
0.6 0.21 0.0005
0.003 -
6.0 3.2 0.007
5.0 4.3 0.010
4.9 5.0 0.012
0.003 17.0 13.0 0.030
0.01 - 1.8 0.004
0.023 - 180 0.42
0.007 - 0.2 0.0004
0.042 - 182 0.43
0.005 - 2.6 0.006
three separate flue gas measurements
to 600 ppm from two separate flue gas measurements
gaseous hydrocarbons, especially in the C4
to C6 range, were recorded with ammonia
injection. This may have been due to
burner tip coking which required frequent
cleaning.
Baseline NH3 emissions ranged from 3
to 25 ppm, averaging 11 ppm (0.23 Ib/hr).
During NH3 injection, unreacted NH3 emis-
sions from two consecutive measure-
ments ranged between 200 and 600 ppm.
averaging 430 ppm (8.4 Ib/hr). A third
measurement resulted in NH3 concentra-
tions of 840 ppm (16.0 Ib/hr). This
measurement was considered erroneous
because it resulted in more NH3 emitted
than actually injected through the grid.
Analyses of the EPA Method 5 and 17 im-
pinger solutions indicated concentrations
of NH3 corresponding to a stack concen-
tration of about 6 ppm (0.12 Ib/hr) for
baseline and 360 ppm (7 Ib/hr) for the NH3
injection test. These results are in general
agreement with the ammonia emission
sampling system.
Nitrous oxide (N2O) averaged about 50
ppm during baseline, and dropped to 17
ppm during the second test. This 68 per-
cent reduction in N2O exceeds the 41
percent reduction in NOX.
Total paniculate matter during the NH3
injection test increased by more than one
order of magnitude. The largest contribu-
tion to this increase was from the in-
organic condensate matter collected in the
impinger section. This can be in part ex-
plained by ammonium sulfate and
bisulfate formed either in the stack or
through the particulate sampling system.
SASS samples were analyzed for or-
ganic content and inorganic trace
elements. Total chromatographable organ-
ics, hydrocarbons in the boiling range of
100° to 300 °C (210 to 570 °F), measured
0.023 ng/J (90 ^g/dscm) for the baseline
and 0.01 ng/J (40 /jg/dscm) for the NH3
injection test. Organics measured by
gravimetry (GRAV) analysis for hydrocar-
bons having boiling points greater than
300 °C (>570°F) were 0.29 ng/J (1,300
ng/dscm) for the baseline and 0.059 ng/J
(240 ug/dscm) for the NH3 injection test.
Infrared spectra of the gravimetric residue
suggest the presence of aliphatic hydro-
carbons and alcohols for both tests.
The XAD-2 extract of the baseline test.
which contained the highest organic con-
tent, was also subjected to liquid
chromatography separation. There were
no discernable peaks from fractions 2
through 4. These spectra indicate that, of
the 1.2 mg/dscm of organic matter in the
total sample, about 70 percent is aliphatic
hydrocarbons, 20 percent is alcohols, and
10 percent is carboxylic acids.
3
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Gas chromatography/mass spec-
trometry analysis of sample extracts was
performed to determine the presence and
concentration of 58 semivolatile organic
priority pollutants. Of these, the only ones
detected were naphthalene, phenanthrene,
and phenol in amounts corresponding to
flue gas concentrations generally <1
Kj/dscm.
Results of spark source mass spec-
trometry (SSMS) and atomic absorption
spectrometry (AAS) indicated that in-
organic trace elements were not affected
by NH3 injection. Major elements having
flue-gas concentrations exceeding 50
mg/dscm for both tests included: sulfur,
copper, nickel, silicon, titanium, vanadium,
zinc, potassium, cobalt, fluorine, and iron.
These emissions are most likely the result
of:
C. Castaldmi, R. DeRosier, andL. R Water/and are with Acurex Corp , Mountain
View. CA 94039.
Joseph A. McSorley is the EPA Project Officer (see below)
The complete report consists of two volumes, entitled "Environmental Assess-
ment of Nf-fa Injection for an Industrial Package Boiler."
"Volume I. Technical Results." (Order No. PB 86-159 852/AS; Cost: $16.95)
"Volume.ll. Data Supplement." (Order No. PB 86-182 409/AS; Cost: $22.95)
The above documents will be available only from: (cost subject to change)
National Technical Information Service
5285 Port Royal Road
Springfield. VA22161
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
• Inorganic elements in the fuel oil.
• Erosion of metal surfaces by the hot
combustion gases in the boiler
passes, including the NH3 injection
grid.
• Erosion of sampling equipment metal
parts.
Summary
Emissions from an industrial boiler fir-
ing refinery gas and residual oil were
tested with and without the Thermal
DeNOx ammonia injection process. N0«
reductions of 30 to 60 percent were ob-
served depending on the ammonia injec-
tion rate, the relative amount of gas and
oil fired, and the use of hydrogen injection
with the ammonia. The primary emission
effect on other species was the formation
of ammonium sulfate and the discharge of
unreacted ammonia.
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S7-86/005
0000329 PS
U S ENVIR PROTECTION AGENCY
CHICAGO
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