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GER-4213
GE Power Systems
Support for Elimination of Oxidation
Catalyst Requirements
for
GE PG7241FA DLN Combustion Turbines
Brahim Richani, Ph.D.
Manager, Environmental and Acoustic Engineering
GE Power Systems
Joel Chalfin
Manager, GT/CC Environmental Compliance
GE Power Systems
White Paper (August 2001)
SUPPORT FOR ELIMINATION OF OXIDATION CATALYST REQUIREMENTS
FOR GE PG7241FA DLN COMBUSTION TURBINES
Applicability emissions reduction benefits under normal
operating conditions.
This position paper applies to GE PG7241FA
combustion turbines with DLN combustors fir- The comparison with existing installations
ing natural gas and located in all attainment using CO catalysts appears to be the primary
areas and ozone non-attainment areas. For all factor influencing regulatory agencies to insist
other GE heavy-duty frame machines, owners on the installation of oxidation catalysts on all
are advised to contact their GE Power Systems combustion turbine units. However, two addi-
sales representative for information regarding tional factors are also considered in this paper;
oxidation catalysts and related requirements. the impetus for expedited permitting, and the
anticipated federal regulation for hazardous air
Abstract pollutant (HAP) emissions from combustion
Emissions regulatory requirements have turbines.
become more stringent for combustion tur- The objective of this paper is to demonstrate
bines (CTs), generally requiring installation of that the installation of an oxidation catalyst to
post-combustion controls regardless of uncon- achieve lower CO levels from GE PG7241FA
trolled emission levels, plant location, costs, DLN combustion turbines sited in CO attain-
process feasibility, or resulting environmental ment areas and ozone non-attainment areas
impacts. Federal and state regulatory agencies should not be required by state, local, and/or
have sought to justify post-combustion controls federal regulatory agencies. The addition of
primarily on the grounds that some existing oxidation catalysts to these units results in min-
installations are currently using oxidation cata- imal CO emissions reduction, adds unnecessary
lysts for carbon monoxide (CO) control. costs, and produces negative environmental
However, a “one-size-fits-all” approach, where impacts.
all units are required to install a particular tech-
nology without consideration of individualized 1.0 Introduction
factors, is in direct conflict with the Clean Air State and federal regulatory agencies are requir-
Act (CAA) Best Available Control Technology ing oxidation catalysts as BACT on combustion
(BACT) analysis procedures and requirements. turbines in an attempt to achieve lower CO
The BACT analysis for CO (or any criteria pol- emissions. Such requirements are making it dif-
lutant) must weigh a variety of factors including ficult for owners to avoid the installation of oxi-
energy, environmental and economic impacts. dation catalysts as add-on controls, regardless of
Dry Low NOx (DLN) combustors for GE the uncontrolled CO emissions levels. The reg-
PG7241FA combustion turbines are now ulatory-mandated BACT process is being cir-
demonstrating uncontrolled CO emissions in a cumvented and U.S. EPA’s own BACT guidance
range so low that the requirement to add an is being ignored. The Clean Air Act clearly
oxidation catalyst on these units will only serve requires that a BACT determination be con-
to reduce efficiency and output; produce nega- ducted on a “case-by-case” basis; however it
tive environmental impacts; and, in light of the appears that in many cases the regulatory agen-
measured data, will not yield detectable CO cies are influencing applicants’ control technol-
GER-4213 s GE Power Systems White Paper s August 2001 Page 1
SUPPORT FOR ELIMINATION OF OXIDATION CATALYST REQUIREMENTS
FOR GE PG7241FA DLN COMBUSTION TURBINES
ogy choices and their BACT determination 2.0 Existing Installations
based on the following factors:
A review of existing CT installations located in
s Existing installations of various manufactur- attainment areas which are using oxidation cat-
ers’ units that are using CO catalysts (i.e., alysts indicates that uncontrolled CO emission
“presumptive BACT”) levels from these units are much higher than
s Applicants’ demands for an expedited per- the demonstrated emission levels from GE’s
mitting process PG7241FA DLN combustion turbines. The
existing installations reviewed have uncon-
s Currently nonexistent, but anticipated,
trolled CO emission rates in the range of 15 to
Maximum Achievable Control Technology
25 ppmvd, while GE’s PG7241FA DLNs have
(MACT) requirements for HAPS
demonstrated uncontrolled CO levels of less
Consequently, the regulatory agencies appear than 5 ppmvd. When post-combustion control,
to be excluding other important factors in their such as an oxidation catalyst, is added to the
BACT determinations, such as: higher emitting units, the resulting CO level
achieved and permitted is approximately
s Cost effectiveness and feasibility of control
5 ppmvd. This emission rate is consistently
s Evaluation of collateral environmental achieved by the GE PG7241FA DLN units, with-
impacts out any add-on controls.
s Evaluation of expected CO emissions on In ozone non-attainment areas, an additional
public health consideration is Volatile Organic Compounds
GE PG7241FA DLN natural gas-fired combus- (VOC) emissions. Oxidation catalysts can be
tion turbines have consistently demonstrated used to reduce VOC emissions from CTs.
uncontrolled CO emissions below 9 parts per However, GE PG7241FA DLN units produce no
million by volume dry (ppmvd) at base load. A measurable quantities of VOC emissions, and
requirement to add an oxidation catalyst to a the guaranteed VOC emission rate of GE
GE PG7241FA DLN combustion turbine with 7241FA is consistent with the lowest achievable
single digit CO emissions will reduce efficiency emission rate (LAER) without any add-on con-
and output, and produce negative environmen- trols.
tal consequences while yielding insignificant
(<1 ppm) reduction in CO emissions under Given these facts, it seems clear that recent EPA
normal operating conditions. For areas desig- BACT decisions requiring add-on controls for
nated as attainment for carbon monoxide, it CO emissions on GE PG7241FA DLN units have
becomes critical that the BACT analysis for CO been made without undertaking a case-by-case
includes environmental, cost effectiveness, and BACT analysis as required by the CAA. In addi-
potential health impacts. The following pro- tion, it appears that EPA’s determination has, in
vides justification of why BACT determinations many cases, ignored the results of cost-effective-
for CO emissions for GE’s PG7241FA DLN units ness analyses and collateral environmental
should result in a conclusion of “No Add-on impacts. These will be discussed in the following
Controls.” sections.
GER-4213 s GE Power Systems White Paper s August 2001 Page 2
SUPPORT FOR ELIMINATION OF OXIDATION CATALYST REQUIREMENTS
FOR GE PG7241FA DLN COMBUSTION TURBINES
3.0 Expedited Permitting Process On August 21, 2001, EPA issued a memoran-
dum indicating, “HAP emissions from lean pre-
The demand to increase electric power supply mix stationary combustion turbines are equiva-
availability in the U.S. is at an all-time high. In lent or lower than HAP emissions from diffu-
2001, some states experienced rotating power sion flame stationary combustion turbines
blackouts (e.g., CA) and others (e.g., NY) were equipped with oxidation catalyst systems. Thus,
expected to follow suit because of the increased lean premix combustion is a comparable tech-
energy demand and the limited number of new nology to oxidation catalyst systems.”
power plants permitted and built in the dereg-
Additionally, GE has tested and provided EPA
ulated market. As a result of the need for
with formaldehyde emissions data using
immediate energy supplies, incomplete or inad-
California Air Resources Board (CARB)
equate BACT analyses are conducted in order
Method 430 from two GE PG7241FA DLN nat-
to expedite the permitting process. The result is
ural gas-fired turbines. The test results demon-
that BACT has essentially become an automatic
strate that the uncontrolled formaldehyde emis-
requirement for an oxidation catalyst for CO
sions when blank corrected (corrected for the
emissions reduction for future projects.
background levels associated with the sampling
train) are typically below 25 ppbvd @ 15% O2.
4.0 Upcoming MACT Requirements Therefore, based on the blank corrected meas-
for HAPS urements, GE’s PG7241FA DLN units may not
Some state and local regulatory agencies are be subject to the upcoming MACT regulation
using the soon-to-be-proposed U.S. EPA and an oxidation catalyst would not be required
Maximum Achievable Control Technology stan- for MACT compliance.
dard intended for the reduction of hazardous
5.0 Cost Effectiveness
air pollutants (primarily formaldehyde) from
combustion turbines as the basis for requiring Inconsistent implementation of BACT across
oxidation catalysts. As of August 2001, when this EPA regions will occur if cost of control and the
paper was drafted, the MACT rule for combus- resulting cost-effectiveness levels are not evalu-
tion turbines had not yet been proposed. ated. As indicated in Table 1, dollars-per-ton
However, EPA has provided some information cost effectiveness analyses as low as $2,055 per
on what the rule would require through indus- ton (Newington Energy in New Hampshire)
try meetings and communications. According have resulted in a decision that no oxidation
to the EPA, all new combustion turbines will catalyst is required for CO from gas combustors
likely be required to install an oxidation catalyst with emissions of 15 ppmvd. These figures con-
to reduce hazardous air pollutants (HAPs), flict directly with a recent (2000) decision by
unless a formaldehyde emission level of less EPA Region II that $6,000 per ton (Heritage
than 25 parts per billion by volume, dry Station, 7H project in Oswego, NY) is consid-
(ppbvd) corrected to 15% O2 is achieved. For ered cost effective for CO control in attainment
combustion turbines achieving less than 25 areas. The lack of uniform EPA guidance
ppbvd @ 15% O2 of formaldehyde, the MACT regarding cost effectiveness determinations is
requirement is expected to be “No Additional causing inconsistencies in BACT determina-
Control.” tions across the country.
GER-4213 s GE Power Systems White Paper s August 2001 Page 3
SUPPORT FOR ELIMINATION OF OXIDATION CATALYST REQUIREMENTS
FOR GE PG7241FA DLN COMBUSTION TURBINES
Catalytic Cost
Final CO
Final CO
Catalytic BACT
BACT
Oxidation Effective- Based on
Oxidation based on
Source/State Model Type of
Type of System
System ness
Cost Eff. Natural
Natural Issuance
Source/State Model Operation
Operation Required
Required ($/ton)
($/ton) Gas
Gas Issuance
Westbrook PG7241FA Combined No >$3,000 15 ppmv Draft findings of
Draft Findings of
Pwr/ME Cycle Fact and Order
(12/98)
Newington PG7241FA Combined No $2,055 15 ppmv 4/99
Energy/NH Cycle
EMI Tiverton/RI PG7241FA Combined No $7,400 12 ppmv 2/98
Cycle
RockGen Energy/ PG7241FA Simple No $15,780 12 ppmv 1/99
WI Cycle
SEI/WI PG7241FA Simple No $14,000 12 ppmv 2/99
Cycle
Tenaska Georgia PG7241FA Simple No $2,300 15 ppmv 12/98
Ptnrs/GA Cycle
PeopleGas and
People Gas and PG7241FA Combined No $3,043 0.03
0.03 1/99
Light, McDonnell and Simple $17,000 lb/mmBtu
lb/mm Btu
Energy/IL Cycle
Table 1. Cost Effectiveness Levels for Recently Permitted Sites
GE’s data collected to date on GE PG7241FA To demonstrate that GE’s PG7241FA DLN units
DLN combustion turbines indicate CO levels should not require add-on controls for BACT
below 2 ppmvd at various loads. (See Figure 1). determinations, cost effectiveness calculations
These data suggest that the addition of are presented in Figure 2.
oxidation catalysts to GE’s PG7241FA DLN These cost estimates are based on 1st Quarter,
units will result in less than 1 ppm CO reduc- 2001, gathered information from two leading
tion on an average basis. Such reductions will catalyst manufacturers (Englehard & Johnson
yield unjustifiably high cost per ton of CO con- Matthey). As shown in Figure 2, the requirement
trolled. for an oxidation catalyst would not be cost effec-
GE PG7241FA CT Units
2.0
1.8 # of Data Sets
Included for:
Max
1.6 50% 7
60% 1
1.4 75% 9
80% 4
1.2 85% 6
CO, ppm
90% 2
Baseload 12
1.0
0.8
0.6
Slope = 0.09
0.4
Min
0.2
0
50 60 70 80 90 100
Load Size (Percent)
Figure 1. Average Raw CO Emissions vs. Load Size (Percent)
GER-4213 s GE Power Systems White Paper s August 2001 Page 4
SUPPORT FOR ELIMINATION OF OXIDATION CATALYST REQUIREMENTS
FOR GE PG7241FA DLN COMBUSTION TURBINES
tive for units with (uncontrolled) CO levels erations, GE is offering CO guarantees of 5
slightly less than 7 ppmvd, based on the $6,000 ppmvd for the GE PG7241FA DLN on a case-by-
per ton identified by EPA-Region II. case basis following a detailed evaluation of the
situation—thus validating its position that oxi-
GE’s CO guarantee is meant to accommodate
dation catalysts are not economically justified
operating conditions at all permitted ambient
for CO emissions reduction for the GE
conditions and has a small margin to account
PG7241FA DLN units while firing natural gas.
for measurement error and machine and fuel
variations. Generally for CO, extremely cold
ambient conditions, concurrent with part load 6.0 Other Environmental Impacts
combustion turbine operations, will represent Use of oxidation catalysts to control CO emis-
the worst-case emissions. GE’s PG7241FA DLN sions from GE PG7241FA DLN combustion tur-
turbine is one of the lowest emitting operating bines produces collateral impacts that are envi-
combustion turbines in simple cycle and com- ronmentally detrimental. A BACT analysis, by its
bined cycle systems. Consequently, GE’s analysis definition, must include consideration of collat-
shows that the CO emission levels from these eral environmental impacts. The EPA must con-
combustion turbines can be tuned to be below sider the severity and resulting expense of these
5 ppmvd. For any emission level below 5 ppmvd, impacts when requiring controls for combustion
the cost effectiveness will be greater than $8,000 turbines like GE’s PG7241FA DLN machines. In
per ton of CO removed. Based on these consid- this case, nitric oxide (NO) and sulfur dioxide
GE PG7241FA CT Units
$20,000
Total Annual Cost estimates based on OAQPS Control
Cost Manual - Fifth Edition (EPA 453/b-96-001) -
$18,000 Chapter 2, Cost Estimating Methodology with the
following exceptions:
$16,000
Contingencies equal 0.1 x (Total Direct
Cost + Total Indirect Cost) instead of
$14,000 0.03 x Purchased Equipment Cost
Based on GE Data
$/ton CO removed
$12,000
Performance Test Cost equals $5,000
in all cases instead of 0.01 x Purchased
$10,000 Equipment Cost because the Performance
Test Cost is not dependent on Catalyst Cost
$8,000
$6,000 EPA Region II BACT Guidance
$4,000
$2,000
$0
0 5 10 15 20 25
CO, ppm
Figure 2. Cost Effectiveness of Oxidation Catalysts
GER-4213 s GE Power Systems White Paper s August 2001 Page 5
SUPPORT FOR ELIMINATION OF OXIDATION CATALYST REQUIREMENTS
FOR GE PG7241FA DLN COMBUSTION TURBINES
(SO2) present in the exhaust will be oxidized by level CO impacts.” The health risks study was
add-on catalysts to nitrogen dioxide (NO2) and based on analysis of a CO emission rate of 9
sulfur trioxide (SO3), both of which promote the ppmvd, which, as stated previously, is signifi-
formation of acid rain. In addition, if applied in cantly higher than the uncontrolled emissions
combination with selective catalytic reduction from GE's PG7241FA DLN combustion turbines
(SCR) for the control of nitrogen oxides (NOx), firing natural gas.
ammonium salts formed as a result of ammonia The following excerpt from page 23 of the RAM
(NH3) slip and SO3 will result in additional gen- TRAC report summarizes the important con-
eration of PM10 (particulate matter less than 10 clusion that CO catalysts do nothing to improve
microns in diameter) and accelerated corrosion public health:
of the heat recovery steam generator (HRSG).
“…Risks posed to public health are quantified
The EPA identified this issue in its August 4,
in this report to be zero, with or without CO cat-
2000, draft guidance “Consideration of
alysts. Indeed, this report reveals that ground
Collateral Environmental Impacts Associated
level impacts of combined cycle natural gas tur-
with the Use of SCR on Dry Low NOx Combined
bines as modeled by GE are far from impacts
Cycle Gas Turbines,” by John S. Sietz, Director,
which would be required to elicit adverse public
Office of Air Quality Planning and Standards
health effects. Modeled turbine impacts would
(OAQPS). Finally, additional carbon dioxide
have to be increased by over an order of magni-
(CO2) will be generated due to the output and
tude to elicit adverse effects associated herein
efficiency losses associated with the pressure
with acute or chronic exposure to CO.”
drop of the catalyst.
In summary, the CO ground level concentra-
7.0 CO as a Public Health Concern tions (GLCs) resultant from the use of the GE
PG7241FA DLN are insignificant when com-
According to a health risks study conducted by
pared to the National Ambient Air Quality
toxicologist R.A. Michaels in a May 2001 report
Standards (NAAQS). The NAAQS are refer-
(“Carbon Monoxide Catalysis: Assessment of Need to
enced in Appendix A.
Mitigate Public Health Risks Posed by Acute and
Chronic Exposure to CO Emitted by Combined Cycle
8.0 Other Considerations
Natural Gas Turbines”; R.A. Michaels, Ph.D.,
C.E.P., RAM TRAC Corporation, May 21, 2001), Use of an oxidation catalyst reduces system effi-
“Ground level CO concentrations arising from ciency and output. System inefficiencies and
combined cycle natural gas turbines were found output losses, in turn, will result in an increase
to be below conservative standards and guide- in emissions. Due to the increase in pressure
lines limiting human exposure to airborne CO. drop associated with the oxidation catalyst in
CO also was found to be below concentrations the exhaust gas path, output (MW) will
posing acute or chronic exposure risks to pub- decrease and heat rate (Btu/kWh) will
lic health.” These findings support the conclu- increase. Since combustion turbines are recog-
sion in the report that “public health concerns do nized as the least polluting combustion sources
not justify requiring natural gas power generators to to generate electricity, any attempt to make up
be equipped with CO catalysis to reduce ground the energy losses will increase emissions.
GER-4213 s GE Power Systems White Paper s August 2001 Page 6
SUPPORT FOR ELIMINATION OF OXIDATION CATALYST REQUIREMENTS
FOR GE PG7241FA DLN COMBUSTION TURBINES
The installation and use of an oxidation catalyst ments are potentially harmful to humans and
will increase the cost of the electricity (COE) the environment. In addition, spent catalyst ele-
produced. With oxidation catalyst requirements ments are considered hazardous waste, thus
on a new PG7241FA DLN combustion turbine, transferring an air emission issue into a long-
the added capital and operating costs of the term solid waste disposal problem. When
catalyst will be absorbed and paid for by the applied in combination with SCR, additional
consumer. Fewer new combined cycle plants salt formation will occur. Ammonia salts
will be built due to the high COE resulting from cleaned from HRSGs are also wastes, which will
increased capital cost and operation and main- need to be disposed of accordingly.
tenance costs; and thus less electricity will be
generated from new plants. Therefore, total CO 9.0 Summary
emissions will not decrease as rapidly, as a result
In summary, the use of an oxidation catalyst to
of the addition of new plants. Emissions of acid
control CO emissions from GE’s PG7241FA
rain pollutants and fine particulate matter,
DLN combustion turbines will result in insignif-
NOx, SO2, CO2, and mercury emissions will
remain at current levels due to continued oper- icant (< 1 ppm) reduction of CO and will not
ation of existing coal plants. substantially reduce ambient CO levels since
minimal CO is emitted under normal operating
The use of an oxidation catalyst creates heavy
conditions. The application of an oxidation cat-
metal wastes. Oxidation catalyst materials con-
tain heavy metal oxides such as platinum and alyst on GE PG7241FA DLN combustion tur-
palladium, which are considered hazardous bines firing natural gas in simple cycle and com-
substances by the EPA. Handling, maintenance, bined cycle plants cannot be justified on a cost
cleaning, and disposal of the spent catalyst ele- (per ton of CO removed) basis.
GER-4213 s GE Power Systems White Paper s August 2001 Page 7
SUPPORT FOR ELIMINATION OF OXIDATION CATALYST REQUIREMENTS
FOR GE PG7241FA DLN COMBUSTION TURBINES
Appendix A. Summary of National Ambient Air Quality Standards (NAAQS)1
Averaging NAAQS (mg/m3 )
Pollutant Time Primary Secondary ppm
Carbon monoxide 8-hour 10,000 None 9
1-hour 40,000 None 35
Lead Calendar quarter 1.5 Same as primary –
Nitrogen dioxide Annual 100 Same as primary 0.053
Ozone 2 1-hour 235 Same as primary 0.12
PM-10 Annual 50 Same as primary –
24-hour 150 Same as primary –
PM-2.5 Annual 15 Same as primary –
24-hour 65 Same as primary –
Sulfur dioxide Annual 80 None 0.03
24-hour 365 None 0.14
3-hour None 1300 0.50
1 National standards, other than those based on annual averages, are not to be exceeded more than once a year (except
where noted).
2 The ozone standard is attained when the expected number of days per calendar year in which the maximum hourly
average concentration is above the standard is equal to or less than one.
Source: Code of Federal Regulations, 40 CFR 50.4-50.12.
List of Tables
Table 1. Cost Effectiveness Levels for Recently Permitted Sites
List of Figures
Figure 1. Average Raw CO Emissions vs. Load Size (Percent)
Figure 2. Cost Effectiveness of Oxidation Catalysts
GER-4213 s GE Power Systems White Paper s August 2001 Page 8
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