United States
Environmental Protection
Agency
Air and Energy Engineering
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA/600/S7-86/014 May 1986
£EPA Project Summary
Environmental Assessment
of a Reciprocating Engine
Retrofitted with Selective
Catalytic Reduction
C. Castaldini and L. R. Waterland
This report describes emission results
obtained from field testing of a gas-fired
lean-burn reciprocating internal combus-
tion engine retrofitted with a selective
catalytic reduction (SCR) system for NOX
reduction. Two series of tests were per-
formed: a comprehensive test program to
characterize catalyst inlet and outlet ex-
haust gas composition at a catalyst NOX
reduction performance target of greater
than or equal to 80 percent; and a 15-day
exhaust monitoring program to measure
the catalyst performance under typical
engine operating conditions.
Emission measurements during the
comprehensive test program included con-
tinuous monitoring of flue gas emissions;
source assessment sampling system
(SASS) sampling of the exhaust gas with
subsequent laboratory analysis of samples
to give solid paniculate emissions, total
organics in two boiling point ranges, com-
pound category information within these
ranges, and specific quantitation of the
semivolatile organic priority pollutants;
VOST sampling for volatile organic emis-
sions at the catalyst outlet; modified EPA
Method 6 sampling systems for NH3 and
total cyanides; and exhaust gas grab sam-
ples for N2O analysis by gas chromato-
graphy. Emission measurements during
the 15-day monitoring program were
limited to continuous monitoring of ex-
haust gas species.
Comprehensive test results indicated
that during the 1-day test the NOX reduc-
tion performance of the catalyst was
maintained relatively constant at 81 per-
cent. NOX emissions at the catalyst inlet
ranged from 2,200 to 2,600 ppm, as
measured at 11.2 percent O2 (2,400 ppm
average). At the catalyst outlet, NOX rang-
ed from 330 to 560 ppm, also at about
11.2 percent O2 (445 ppm average).
CO emissions averaged 245 ppm at the
catalyst inlet and 225 ppm at the outlet.
Hydrocarbon emission data were not
available for the comprehensive tests;
however, emission results obtained during
the extended emission testing indicated
emissions in the range of about 1,500 to
1,800 ppm at both the inlet and outlet.
Total organic (C6 + ) emissions were ap-
parently reduced across the catalyst from
4.9 to 1.5 mg/dscm (20 to 6.2 mg/bhp-
hr). Emissions of two polynuclear aromatic
hydrocarbon (PAH) species, naphthalene
and phenanthrene, and a nftrophenol were
quantitated. Again, catalyst inlet levels
were higher than outlet levels. Outlet PAH
emissions were at or below 0.4 /ig/dscm
(about 1.6 pg/bhp-hr).
During the extended 15-day perform-
ance test, the NOX reduction performance
was also maintained relatively constant at
about 80 percent. Only occasionally and
briefly did NOX reduction fall below 80
percent. These brief low catalyst perform-
ance periods were attributed to engine
load surges and an occasional malfunction
in the NH3 injection flowrate.
This Project Summary was developed
by EPA's Air and Energy Engineering Re-
search Laboratory, Research Triangle Park,
NC, to announce key findings of the re-
search project that is fully documented in
two separate volumes of the same title
(see Project Report ordering information
at back).
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Introduction
In California, the South Coast Air Quali-
ty Management District (SCAQMD) con-
tinues to be in nonattainment of both
federal and state NO2 standards. Station-
ary reciprocating internal combustion en-
gines (ICEs) are estimated to contribute
about 14 percent of the NOX (about 59
Mg/day (65 tons/day)) from all stationary
sources and 5.1 percent of total NOX
emissions in the basin. In 1979, the
California Air Resources Board (CARS)
proposed a control strategy for ICEs that
called for retrofit of these sources with
nonselective and selective gas treatment
catalysts (NSCR and SCR, respectively).
The proposed SCAQMD rule 1110 called
for demonstration of 90 percent NOX
reduction or an emissions limit of 0.28
u.g/J (0.75 g/bhp-hr) of heat output.
Following this proposed rule, there has
been a sustained R&D effort to demon-
strate the capability of commercially
available NSCR and SCR catalysts and
identify problems in their application. In
September 1984, a modified version of
this rule was adopted by SCAQMD calling
for 80 percent NOX reduction demonstra-
tion with subsequent 70 percent reduction
from existing lean-burn engines. The re-
trofit schedule calls for 80 percent of all
existing lean-burn engines with capacity
greater than 500 hp in the South Coast Air
Basin to be controlled by December 31,
1987. The remaining lean-burn engines (all
above 50 hp) are to be controlled by
December 31, 1994.
This report describes the results of com-
prehensive emission tests and 15-day ex-
tended monitoring tests of a lean-burn
reciprocating engine retrofitted with an
SCR system. Emissions were measured at
both the inlet and outlet of the catalyst to
quantitate both NOX reduction perfor-
mance and the impact of the catalyst on
other pollutants.
The tests were performed on an Inger-
soll-Rand 412 KVS (2,000-hp) four-stroke,
turbocharged gas compressor engine
owned and operated by Southern Califor-
nia Gas Company (SoCal). In April 1984,
the engine was retrofitted with an Engle-
hard SCR catalyst system. A similar sys-
tem was previously tested on a slipstream
of the engine and found capable of 90 per-
cent NOX reduction. The catalyst, based
on a proprietary metal oxide formulation,
has an upper temperature limit of 427 °C
(800 °F). The slipstream tests by SoCal
had shown that 90 percent NOX reduction
was achieved using an NH3/NO injection
rate of 1.0 (molar ratio) and an exhaust
temperature of about 400°C (750°F).
Summary and Conclusions
Engine Operation
The test program called for the evalua-
tion of NOX reduction performance of the
catalyst and its effect on organic and in-
organic gaseous pollutants during 1 day
of comprehensive tests with the engine
NH3 injection rate adjusted for NOX re-
duction of greater than 80 percent at con-
stant power output. In addition, the test
program called for a continuous 15-day
emission monitoring program to evaluate
the NOX control capability with the engine
operating under typical conditions with
varying load and NH3 injection rate.
Table 1 summarizes engine operating
characteristics during the comprehensive
tests. Engine load was maintained relative-
ly constant, at about 1,270 kW (1,700 hp),
throughout this portion of the test pro-
gram. Brake-specific fuel consumption
was 9.4 MJ/kWh (6,600 Btu/bhp-hr) bas-
ed on fuel lower heating value. This is at
the low end of representative four-stroke
turbocharged engines. The NH3 injection
rate ranged from about 4.4 to 4.9 l/s (565
to 620 scfh), representing an NH3/NO
molar ratio of about 1.0. The NH3 injec-
tion rate was controlled by a feedback
system which monitored NOX at the en-
gine outlet and set NH3 injection rate to
maintain a target NOX reduction of 80
percent.
Note that, prior to the test period, pro-
blems were experienced with the NH3
control system, specifically the NOX
analyzer and the NH3 control valve.
Emission Measurements and
Results — Comprehensive Tests
The sampling and analysis procedures
used in this test conformed to a modified
EPA Level 1 protocol. The exhaust gas
measurements included the following at
both the catalyst inlet and outlet:
• Continuous monitoring for O2, C02,
CO, NO/NOX, NH3, and TUHC.
• SASS sampling.
• VOST sampling for volatile organics.
• Modified EPA Method 6 train sampl-
ing for NH3 and total cyanide.
• Gas grab sample for N2O
determination.
The analysis protocol included:
• Analyzing SASS train samples for
Table 1. Engine Operation — Comprehensive Tests
Parameter Range
Average
Ambient
Dry bulb temperature, °C (°F)
Wet bulb temperature, °C (°F>
Relative humidity, percent
Barometric pressure, kPa (in. fig)
Engine Operation
Engine load, kWt ibhpf
Fuel flow, m3/h (scfh)
Heat input, MW (mi/lion Btu/hrf>
Specific fuel consumption, kJ/kWh
(Btu/bhp-hr^
Air manifold pressure, kPa (psig)
Air manifold temperature, °C (°F)
Engine speed, rpm
Exhaust manifold temperature, °C (°F)
Catalyst/NH3 System
Catalyst inlet temperature, °C (°F)
Catalyst outlet temperature, °C (°F)
NH3 flowrate, l/s (scfh)
Gas Compressor
Suction pressure, MPa (psig)
Interstage pressure, MPa (psig)
Discharge pressure, MPa (psig)
Suction temperature, °C (°F)
Interstage temperature, °C (°F)
Discharge temperature, °C (°F)
22 to 33 (72 to 92)
19 to 21 (67 to 72)
45 to 55
25 to 28 (3.6 to 4.0)
68 to 70 (154 to 158)
320 to 333
380 to 382 (716 to 720)
390 to 400 (740 to 750)
344 to 382 (652 to 720)
4.44 to 4.88 (565 to 620)
26 to 35 (78 to 95)
88 to 93 (180 to 200)
107 to 118 (225 to 245)
29 (84)
20 (68)
50
96.2 (28.5)
1270 (1700)
327 (11,550)
3.29 (11.2)
9390 (6610)
26.5 (3.85)
69 (156)
325
380 (718)
396 (745)
362 (683)
4.64 (590)
4.02 (583)
7.86 (1,140)
18.87 (2,898)
29 (85)
91 (195)
113 (235)
aEngine load obtained from engine performance curves.
bHeat input based on low heating value (LHV) of natural gas. Specific fuel
consumption based on LHV of fuel.
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total organic content in two boiling
point ranges: 100 to 300 °C by total
chromatographable organics (ICO)
analysis, and greater than 300 °C by
gravimetry (GRAV).
• Analyzing the SASS train sorbent
module extract for 58 semivolatile
organic species including many of the
PAH compounds.
• Performing infrared (IR) spectrometry
analysis of organic sample extracts.
• Analyzing VOST traps for 34 volatile
organic priority pollutant species.
Table 2 summarizes emissions mea-
sured at the engine muffler outlet (catalyst
inlet) and the catalyst outlet. Continuous
monitored emissions (O2, C02, CO,
NO/NOX, and TUHC) were measured up-
stream of the NH3 injection, located
upstream at the engine muffler. Emissions
are presented in milligrams per dry stan-
dard cubic meter, nanograms per Joule
heat input, and milligrams per brake
horsepower-hour shaft output.
As shown in Table 2, NOX emissions
were reduced 81 percent on the average,
from 2,760 to 513 ng/J (19.2 to 3.57
g/bhp-hr). Actually, NOX reductions did
not vary significantly from this average
throughout the test, indicating a relatively
constant NOX reduction performance of
the catalytic system.
NH3 emissions measured at the cata-
lyst outlet with an extractive sampling
system averaged 39 ng/J (0.27 g/bhp-hr),
corresponding to a volumetric gas concen-
tration of 93 ppm. NH3 emissions, also
measured at this location by a continuous
monitoring system, confirmed these re-
sults. Total cyanide increased significantly
across the catalyst to a concentration of
2.4 mg/dscm at the catalyst outlet. Both
TCO and GRAV organics were apparently
reduced by the catalyst by about 46 and
82 percent, respectively. This performance
coincides with relatively low CO levels that
were also measured at the catalyst outlet.
Solid paniculate emissions were not de-
tectable within the accuracy of the analy-
tical procedure.
Table 3 summarizes the emissions of
volatile and semivolatile organic com-
pounds detected by GC/MS analyses of
VOST traps and SASS sorbent extract
samples. Volatile organics were measured
only at the catalyst outlet. These data
show benzene and toluene as the principal
compounds with concentrations of about
900 and 250 (jg/dscm, respectively, at the
catalyst outlet. Other volatiles detected
were xylenes, chlorobenzenes, and ethyl-
benzenes with concentrations below 100
ug/dscm. Naphthalene and 2-nitrophenol
were the major semivolatile organics
detected at the catalyst inlet. Their con-
centrations of 8.4 and 5.3 ug/dscm,
respectively, were reduced at the outlet to
undetectable levels (^0.4 ug/dscm).
Emission Measurements and
Results — 15-Day Monitoring
The sampling and analysis protocol for
this portion of the test program consisted
of continuous monitoring of inlet and out-
let exhaust gas for 02, C02, CO, NO/NOX,
NH3/ and TUHC with certification of NOX
analyzer readings using EPA Method 7.
Since both engine power output and NH3
injection rate were not restricted to spe-
cified ranges, the data obtained can be
considered reflective of typical operating
practice. Figures 1 through 6 summarize
emission results. Each data point in these
figures represents an hourly average. The
data indicate relatively steady engine
operation with exhaust O2 levels at about
11 percent and CO2 at about 5.5 percent.
NOX emissions ranged between 1,200
and 1,600 ppm corrected to 15 percent
O2 at the inlet and about 100 to 400 ppm
at 15 percent 02 at the catalyst outlet.
NOX reduction efficiency translates to
nearly constant 80 percent as shown in
Figure 3. The two data points indicating
reduced or no NOX reduction were gen-
erally caused by an occasional loss of
NH3 flow or a surge in engine load. These
Table 2. Summary of Exhaust Gas Emissions
Catalyst inlet3
Catalyst outlet3
Specie mg/dscm ng/J mg/bhp-hr mg/dscm ng/J mg/bhp-hr
NOX (as NO2)
CO
NH3b
Total cyanide (as C/W
N2O°
Total chromatographable
organics (C7 to C16)
Total GRA V organics
(C16+l
4,630
287
0.007
180
1.7
3.2
2,760
171
0.004
108
1.0
1.9
19,200
1,190
0.03
750
7.0
13
860
265
65
2.4
79
0.9
0.6
513
158
39
1.4
47
0.54
0.34
3,570
1,100
270
10
327
3.7
2.4
aAverage exhaust gas O2 and C02 were 11.2 and 5.5 percent, respectively, at both
catalyst inlet and outlet.
bNH3 emissions at the engine outlet were not measured by wet chemical analysis.
°N2O emissions were measured after the comprehensive test period. Catalyst inlet and outlet
NOX during these tests were similar to levels measured during the comprehensive tests.
Table 3. Volatile and Semivolatile Organic Emissions
Compound Catalyst Inlet
fag/dscm]
Catalyst Outlet
(ng/dscm)
Volatile organics:3
Benzene
Chlorobenzene
Chloroethane
1,1,dich/oroethane
Ethylbenzene
Tetrachloroethane
Toluene
Acetone
Total xylenes
Semivolatile organics:
Naphthalene
Phenanthrene
2-Nitrophenol
Di-n-butyl phthalate0
Bis(2-ethylhexyl)phthalatec
NAb
8.4
0.4
5.3
3.1
1.9
915
61
1.8
1.5
20
2.4
247
17
85
0.4
<0.4
<0.4
5.5
1.0
a Volatile organic emissions measured only at the catalyst outlet. Values
presented are blank corrected average of two measurements.
bNA = Not available. No measurements for volatile organics performed
at the catalyst inlet.
0Suspected contaminants, commonly found in laboratory blanks.
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72-
10-
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i
CM
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O
I
q>
i
WO-i
80-
60-
40-
20-
O
O
O
rn
-
<§>
10
024 6 8
Test Day
Figure 3. Catalyst NO* reduction efficiency for the extended monitoring period.
12
14
500 -i
400-
300-
Q.
10
I
i
;: 200-
o
a 100-
o
Figure 4. Catalyst outlet NH3 emissions for the extended continuous monitoring period.
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5,000
g 4,000
c
fc.
Q)
|o 3,000
<5
E
g.
O 2,000-
1
fe 2,000-
0.
JO
ro
| 1.500-
<^>
\
* 1.000-
1
500-
0
O Inlet TUHC
A Outlet TUHC
*'£
§^//s !
1 i i 1 i i i
9 2 4 6 8 10 12 14
Test Day
Figure 6. Exhaust hydrocarbon levels for the extended continuous monitoring period.
6
U. S. GOVERNMENT PRINTING OFFICE:! 986/646-116/20845
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C. CastaldiniandL. Water/and are withAcurex 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 a Reciprocating Flame Retrofitted with Selective Catalytic Reduction:"
"Volume I. Technical Results," (Order No. PB 86-183 779/AS; Cost: $ 11.95)
"VolumeII. Data Supplement,"(OrderNo. PB86-183 787/AS; Cost: $11.95)
The above documents will be available only from: (cost subject to change)
National Technical Information Service
5285 Port Royal Road
Springfield, VA 22161
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
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
Official Business
Penalty for Private Use $300
EPA/600/S7-86/014
...".iN."" 36
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CHICAGO
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