United States
Environmental Protection
Agency
Industrial Environmental
Research Laboratory
Research Triangle Park NC 27711
Research and Development
EPA-600/S7-84-073 Aug. 1984
Project Summary
Environmental Assessment of a
Reciprocating Engine Retrofitted
with Nonselective Catalytic
Reduction
C. Castaldini and L.R. Waterland
This report describes emission results
obtained from field testing of a rich-
burn reciprocating internal combustion
(1C) engine retrofitted with a nonselec-
tive catalytic reduction (NSCR) system
for NOx reduction. Two series of tests
were performed: a comprehensive test
program to characterize catalyst inlet
and outlet organic and inorganic emis-
sions at optimum catalyst NO* reduc-
tion performance; and a 15-day exhaust
emission monitoring program to mea-
sure the catalyst performance under
typical engine operating conditions.
Emission measurements during the
comprehensive test program included:
(1) continuous monitoring of flue gas
emissions; (2) source assessment
sampling system (SASS) sampling of the
exhaust gas with subsequent laboratory
analysis of samples to give solid
particulate emissions, total organics in
two boiling point ranges, compound
category information within these
ranges, specific quantitation of the
semivolatile organic priority pollutants,
and exhaust gas concentrations of 73
trace elements; (3) Modified Method
6 sampling for NH3 and total cyanides;
and (4) exhaust gas grab sampling from
N2O analysis by gas chromatography.
Emission measurements during the 15-
day monitoring program were limited to
continuous monitoring of exhaust gas
species.
Comprehensive test results indicated
that over the 1 -day test period the NOx
reduction performance of the catalyst
ranged between 54 and 81 percent with
an average of 70 percent. NO, emis-
sions at the catalyst inlet ranged
between 1,650 and 1,850 ppm as
measured at 0.1 percent O2 (1,700 ppm
average). At the catalyst outlet NO*
ranged between 300 and 800 ppm, also
at 0.1 percent O2 (550 ppm average).
Catalyst inlet CO concentrations
averaged 14,600 ppm as measured and
total unburned hydrocarbons (TUHC)
averaged 215 ppm. High catalyst inlet
combustible concentrations are neces-
sary to ensure sufficient reducing agent
to allow the catalytic NO* reduction
reactions to occur. This required that
the engine operate with an air/fuel ratio
(A/F) near or slightly below the stoi-
chiometric A/F of 16.35 (dry weight
basis). TUHC concentrations were re-
duced to 125 ppm, and CO levels were
reduced to an average of 13,200 ppm
by the catalyst. Total organic (C6+)
emissions were also reduced by the
catalyst from 15.5 to 2.1 mg/dscm (36
to 4.7 mg/Bhp-hr) in parallel with
corresponding TUHC and CO reduc-
tions. Emissions of 14 polynuclear
aromatic hydrocarbon (PAH) species
were quantitated in both catalyst inlet
and outlet exhaust. Again, inlet levels
were generally higher than outlet levels,
except for naphthalene and phenol
emissions, which increased.
During the 15-day performance test,
the NO. reduction performance was
mostly in the 0 to 40 percent range.
Only occasionally did NO, reduction
exceed 90 percent. During the periods
of higher reduction performance, CO
and TU HC emissions at the inlet were as
high as 1 and 0.1 percent, respectively.
-------
This Project Summary was developed
by EPA's Industrial Environmental
Research Laboratory, Research Tri-
angle 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
In California, the South Coast Air
Quality Management District (SCAQMD)
continues to be in nonattainment of both
federal and state N02 standards. Station-
ary reciprocating 1C engines are estimated
to contribute about 14 percent of the NOX
(about 59 mg/day (64 tons/day)) from all
stationary sources and 5.1 percent of
total NO* emissions in the basin. In 1979,
the California Air Resources Board
(CARB) proposed a control strategy for 1C
engines in the SCAQMD that called for
retrofit of these sources with nonselective
and selective gas treatment catalysts
(NSCR and SCR, respectively). The
proposed SCAQMD rule 1110 calls for
demonstration of 90 percent reduction or
an emissions limit of 0.28 /ug/J (0.75
g/Bhp-hr) of heat output. Following this
proposed rule, there has been a sustained
R&D effort to demonstrate the capability
of commercially available NSCR and SCR
catalysts and identify problems in their
application.
This report gives results of comprehen-
sive emission tests and long-term catalyst
performance tests of a rich-burn recipro-
cating engine retrofitted with an NSCR
system. Emissions were measured at
both inlet (muffler outlet) and outlet of the
catalyst to quantitate both NO* reduction
performance and the impact of the
catalyst on other inorganic and organic
pollutants.
The tests were performed on a Wau-
kesha 610 kW (818-hp) L7042 GU four-
stroke naturally aspirated electric gener-
ator engine owned and operated by
Southern California Gas Company (SoCal).
In November 1982, the engine was retro-
fitted with a DuPont PR-5 NSCR catalyst
having about 6,000 operating hours on
another SoCal engine. This catalyst was
previously tested and found capable of 90
percent NO* reduction on the larger
compressor engine. The PR-5 catalyst is
based on a platinum/rhodium formulation
and has an upper temperature limit of
1,450°F (788°C). Previous tests by SoCal
had shown that 90 percent NQX reduction
was achieved over a narrow A/F range,
with A/F rich enough that catalyst inlet
CO and TUHC concentrations exceeded
4,000 and 1,000 ppm respectively. This
A/F is richer than the engine would
normally be operated, resulting in a fuel
penalty of 11 percent.
Summary and Conclusions
Engine Operation
The tests called for evaluating NOX
reduction performance of the catalyst and
its effect on organic and inorganic
pollutants during 1 day of comprehensive
tests with the engine A/F adjusted for
optimum NOX reduction at constant
power output. In addition, the program
called for continuous 15-day emission
monitoring to evaluate the long-term NOX
control capability with the engine operat-
ing under typical conditions with varying
load and A/F.
Table 1 summarizes engine operating
characteristics during the comprehen-
sive tests. Engine load was maintained
relatively constant throughout this
portion of the test program. Generator
output varied from 415 to 455 kWe,
corresponding to about 450 - 490 kW
(600 - 660 bhp) engine shaft output.
Brake specific fuel consumption was 12.3
MJ/kWh (8,660 Btu/bhp-hr) based on
fuel lower heating value. This represents a
loss in fuel efficiency of about 15 percent,
based on the manufacturer's specifica-
tion for full load operation.
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 at both the catalyst inlet
and outlet included:
• Continuous monitoring for Oa, COa,
CO, NO/NOX, and TUHC
• SASS sampling
• Modified Method 6 train sampling for
NH3 and total cyanide
• Gas grab sample for NzO determina-
tion
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. Hg)
Engine Operation
Generator output, kWa
Engine load, kW, (bhp)*
Fuel flow, m3/hr (scfh)
Heat input, MW (JO6 Btu/hrf
Specific fuel consumption, kJ/kWhr
(Btu/bhp-hrl0
Air manifold pressure
• L, kPa (in. Hg vac)
• Ft, kPa (in. Hg vac)
Speed, rpm
Catalyst inlet temperature. °C <°F)
Catalyst output temperature, °C (°F)
Gas Analysis, percent volume^
26 to 29 (79 to 85)
20 to 22 (68 to 71)
415 to 455
448 to 492 (601 to 660)
14 to 16(4.1 to 4.6)
14 to 16(4.1 to 4.8)
900 to 910
533 to 536 (991 to 997)
534 to 561
(994 to 1.042)
29 (84)
22(71)
52
96.4(28.55)
425
459 (616)
156 (5.569)
1.56 (5.33)
12.300(8,660)
15 (4.4)
15 (4.5)
905
535 (995)
552 (1,025)
02
N2
CO2
CHt
C2Ha
CaHa
iso-CtHio
h-CtHio
iso-CsHi2
h-CsHi2
Ce+
HHV. MJ/m3 (Btu/ft3f
LHV. MJ/m3 (Btu/ft3)"
"Horsepower not a measured value — calculated from generator output times
0.073
1.119
0.890
90.119
6.294
1.247
0.094
0.106
0.029
0.029
0.003
39.9 (1.072)
36.0(968)
1.45.
bBased on low heating value.
cBased on data supplied by SoCal.
"Calulated heating value.
-------
The analysis protocol included:
• Analyzing SASS train samples for 73
trace elements using spark source
mass spectrometry (SSMS), supple-
mented by atomic absorption spec-
trometry (AAS)
• Analyzing SASS train samples for
total organic content in two boiling
point ranges: 100° to 300°C by total
chromatographable organics (TCO)
analyses, and greater than 300°C by
gravimetry (GRAV)
• Analyzing the SASS train sorbent
module for 58 semivolatile organic
species including many of the PAH
compounds
• Performing infrared (IR) spectrometry
analysis of organic sample extracts
• Performing liquid chromatography
(LC) separation of selected sample
extracts with subsequent TCO, GRAV,
and IR analysis of LC fractions
• Performing mutagenicityandtoxicity
health effects bioassays of SASS
samples
Table 2. Summary of Exhaust Gas Emissions
Table 2 summarizes emissions mea-
sured at the engine muffler outlet
(catalyst inlet) and the catalyst outlet.
Emissions are presented in milligrams
per dry standard cubic meter (mg/dscm),
nanograms per Joule heat input (ng/J),
and milligrams per brake horsepower-
hour shaft output (mg/bhp-hr). As a
measure of the relative potential signifi-
cance of the emissions, an occupational
exposure guideline concentration for
each species is also noted in the table.
The guideline noted is generally either
the time-weighted-average Threshold
Limit Value (TLV) or the 8-hr time-
weighted-average exposure limit estab-
lished by the Occupational Safety and
Health Administration (OSHA). These are
noted only to aid in ranking the potential
significance of pollutant species emis-
sions. Conclusions regarding the absolute
risk associated with emission levels
compared to occupational exposure
guidelines are not, and should not, be
drawn. With respect to ranking, however,
species emitted at levels several orders of
magnitude higher than their occupational
exposure guidelines might warrant
further consideration. Species emitted at
levels significantly lower than their
occupational exposure guidelines could
be considered of little potential concern.
Only species emitted at levels exceeding
10 percent of their occupational exposure
guidelines are noted in Table 2.
As shown in the table, NO* emissions
were reduced about 70 percent on the
average from 770 to 250 ng/J (7.8 to 2.5
g/bhp-hr). Actually, NO* reduction
ranged from about 50 to 80 percent. This
variation was probably caused by small
perturbations in engine load accompanied
by small changes in A/F. This degree of
NO, reduction is not sufficient to meet
SCAQMD proposed NO* reduction rules
of 90 percent or 280 ng/J heat output
(0.75 g/bhp-hr).
Both ammonia and total cyanide
increased significantly across the cata-
lyst. Catalyst outlet ammonia levels
Catalyst inlet"
Specie
mg/dscm ng/J
mg/bhp-hr
Catalyst outlet*
mg/dscm ng/J
mg/bhp-hr
Occupational
exposure
guideline0
(mg/m3)
Criteria and other
gaseous pollutants and
total organic emissions
CO 5,350 1,210 1.22x10* 4,840 1.03O 10,400
NO*(asNOz) 3,410 770 7,790 1,180 250 2,530
NHa 23 5.2 53 390 82 820
Total cyanide 0.022 0.005 0.057 10 2.2 22
(as CN>
/V2O° 270 60 600 170 36 360
Solid paniculate 1.3 0.30 3.0 1.4 0.30 3.0
Total chromatographable
organics (C7 to CW 8.1 1.8 19 1.8 0.40 4.1
Total GRAV organics 7.4 1.7 17 0.30 0.055 0.56
55
6.0
18
5.0
10"
Trace elements
Barium, Ba
Calcium, Ca
Chromium, Cr
Copper, Cu
Iron, Fe
Nickel. Ni
Phosphorus, P
Potassium, K
Silicon. Si
Silver, Ag
Sodium, Na
Zinc, Zn
0.049
0.450
0.0007
0.015
0.039
0.0008
0.005
0.17
0.12
0.0015
150
0.024
0.011
0.10
1.5x 10~*
0.0035
0.0090
1.8x 10'*
0.0012
0.040
0.028
3.4 x 10'*
34
0.0055
0.11
1.1
0.0015
0.035
0.091
0.0018
0.012
0.41
0.28
0.0034
340
0.056
0.064
0.16
0.78
1.2
0.41
0.69
0.03
0.36
1.4
0.22
160
0.46
0.014
0.034
0.17
0.25
0.088
0.15
0.0064
0.076
0.31
0.046
35
0.089
0.14
0.34
1.7
2.5
0.88
1.5
0.064
0.76
3.1
0.46
350
0.89
0.50
2.0
0.050
0.10'
1.0
0.10
0.10
2.0a
10
0.010
2.0*
1.0
"Average exhaust gas O2 and CO2 were 0.1 and 10.2 percent at both inlet and outlet.
''Time-weighted average Threshold Limit Value (TLV), unless noted.
c/VzO emissions were measured during low catalyst NOf reduction efficiency following completion of the comprehensive tests. N20 emissions are
averages of two tests during which /VOX emissions were about 2,700 ppm.
d—denotes no occupational exposure guideline applicable.
eFor nuisance particulate.
'8-hr time-weighted average OSHA exposure limit.
^Ceiling limit.
-------
exceeded inlet levels by an order of
magnitude, 23 to 390 mg/dscm (31 to
490 ppm). Although much lower than
ammonia, total cyanides showed a much
greater percentage increase across the
catalyst, from 0.022 to 10 mg/dscm.
These results agree with previous studies
on the effect of NSCR catalyst on NH3and
CN emissions. Solid particulate showed
no noticeable change due to the catalyst.
In line with a reduction in combustible
emissions (TUHC—as CH4—and CO).
TCO was reduced by the catalyst by about
75 percent, and GRAV organics were
reduced by about 95 percent.
Table 2 shows that several trace
elements (chromium, copper, nickel,
silver, and sodium) were present in the
engine exhaust at levels exceeding their
respective occupational exposure guide-
lines. Except for sodium, these elements
were present at levels exceeding their
respective guidelines only at the catalyst
outlet, which suggests that the catalyst
system itself introduces some of each
element. Both ammonia and cyanide
were present in the catalyst outlet
exhaust at levels exceeding their guide-
lines. CO emissions were at levels almost
90 times its occupational exposure
guideline, and NO, emissions at the
catalyst outlet were at levels almost 200
times its guideline.
Table 3 summarizes the PAH and other
organic compounds detected by GC/MS
analysis of the catalyst inlet and outlet
sample extracts. Consistent with the
overall reduction in total combustible
emissions, these compounds were pres-
ent at significantly lower concentrations
in the catalyst outlet exhaust than in the
•inlet exhaust. Interestingly, all three-ring
fused aromatics were destroyed by
passage through the reactor. Levels of
phenol and naphthalene, one- and two-
ring aromatics, instead were increased at
the outlet, suggesting that these lower
molecular weight aromatics were being
formed from higher ring number com-
pounds.
Bioassay tests were performed on the
organic module extract (XAD-2 and
organic module condensate) from both
SASS trains (inlet and outlet). Only health
effects tests were performed: the Ames
mutagenicity assay and the CHO cyto-
toxicity assay. Table 4 summarizes the
results of these assays. The data suggest
that the XAD-2 extract from the inlet was
of high mutagenicity and moderate to high
toxicity. The catalyst outlet XAD-2 extract
was of moderate mutagenicity and
toxicity. These are typical bioassay
responses for combustion source XAD-2
extract.
Table3. PAH and Other Organic Species Emission Summary
Semivolatile and
nonvolatile organics
Inlet'
Outlet**
Acenapthene
A cenaphthylene
Benz(a)anthracene
Benzofluoranthenes
Bis(2-chloroethyl)ether
Bis(2-ethylhexyl)phthalate
Butyl benzyl phthalate
Chrysene
Fluoranthene
Fluorene
Naphthalene
Phenanthrene
Phenol
Pyrene
16.5
62.3
5.1
1.9
2.1
54.9
0.7
1.9
0.5
17.9
80 percent) cannot
be maintained without tight control of
A/F within a narrow range. This range
spans A/F near or below stoichiometry.
The data suggest that corresponding CO
and TUHC engine emissions required for
optimum catalytic performance are in
excess of 3,000 ppm and 400 ppm,
respectively, at 15 percent O2. Long-term
(15-day) continuous monitoring indicates
the inability of the engine tested to be
maintained at the necessary conditions of
A/F, CO, and TUHC to achieve controlled
NO, emissions at or below the proposed
SCAQMD level. The catalystwas found to
significantly reduce all combustible
emissions including most PAH. This
agrees with the oxidation reaction
process of the NSCR reactor. Significant
-------
5-
3-
D Inlet O2
A Outlet Oz
increases in NHs and total cyanide
emissions were recorded, confirming
anticipated and previously discovered
trends. Exhaust levels of many inorganic
trace elements also increased across the
catalyst. Major elements of potential
concern are chromium, copper, nickel,
silver, and sodium.
17
579
Figure 1. Exhaust Oz during the 15-day continuous monitoring period.
11 13 15
June 1983
19
21
O
O
15
14'
13-
12-
11.
lo-
D Inlet CO*
A Outlet CO2
11
17
13 15
June 1983
Figure 2. Exhaust COz during the 15-day continuous monitoring period.
19
21
-------
6000
5000
4000
-a
o
s?
«o
3000
,9.
2000
1000
O Inlet CO
A Ot/r/ef CO
573
Figure 3. CO emissions during the 15-day continuous monitoring period.
11 13 15
June 1983
17 19 21
1200
1000-
^
soo-
1600-
*"
400-
200-
n
D Inlet TUHC
A Outlet TUHC
73 75
73S3
77
A
27
figure 4. TUHC emissions during the 15-day continuous monitoring period.
-------
1400
1200
1000
800-
10
I
O
600.
400-
200
D Inlet NO*
A Outlet NO,
11 13 15
June 1983
17
19
21
Figure 5. NO* emissions during the 15-day continuous monitoring period.
*USGPO: 1984-759-102-10656
-------
C. Cast aldini and L R. Water land are withAcurex Corporation, Mountain View,
CA 94039.
Robert E. Hall is the EPA Project Officer (see below).
The complete report consists of two volumes, entitled "Environmental Assess-
ment of a Reciprocating Engine Retrofitted with Nonselective Catalytic
Reduction:"
"Volume I. Technical Results," (Order No. PB 84-224 351; Cost: $13.00)
"Volume II. Data Supplement." (Order No. PB 84-224 369; Cost: $ 13.00)
The reports above 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:
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
Official Business
Penalty for Private Use $300
------- |