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MEMORANDUM

DATE: June 20, 2005

SUBJECT: NO~X~ Control Technologies for Stationary Diesel ICE

FROM: Tanya Parise, Alpha-Gamma Technologies, Inc.

TO: Sims Roy, EPA OAQPS ESD Combustion Group

The purpose of this memorandum is to present information on different
types of nitrogen oxides (NOx) controls that can be applied to
stationary internal combustion engines (ICE) operating on diesel fuel.

**Introduction**

Several control technologies capable of reducing NOx emissions from
stationary ICE are discussed within this memorandum. Add-on or
post-combustion controls (also referred to as secondary methods of
control) for NOx are control methods designed to treat the exhaust
emissions from stationary ICE once NOx emissions have formed. On-engine
or in-cylinder controls (also referred to as primary methods of control)
for NOx are control methods designed to minimize the amount of NOx
formed. Control methods that are commercially available and control
technologies that are under development are discussed. Table 1 presents
a summary of the NOx emissions reductions that can be achieved for the
control methods discussed in this paper.

**Commercially Available**

**Add-On Control**

[Selective Catalytic Reduction]{.underline}

Selective catalytic reduction (SCR) has been on the market and proven
reliable for over 15 years. However, it has not been widely used for
engines. Miratech, Johnson Matthey, Engelhard, RJM, Wartsila and
Catalyst Products are some manufacturers that make SCR. Selective
catalytic reduction is often used in combination with an oxidation
catalyst and is the only commercially proven secondary NOx reduction
method for lean burn gas and diesel engines. The following requirements
and difficulties are associated with applying SCR:

Table 1. Summary of NOx Controls for Stationary Diesel ICE

+--------+------+-----------+------------+----------+----------------+
| **C    | *    | **A       | **Cost**   | **Other  | **Concerns/**  |
| ontrol | *NOx | pplicable |            | P        |                |
| Me     | Red  | Engines** |            | ollutant | **             |
| thod** | ucti |           |            | Redu     | Requirements** |
|        | on** |           |            | ctions** |                |
|        |      |           |            |          |                |
|        | **(  |           |            | **(%)**  |                |
|        | %)** |           |            |          |                |
+--------+------+-----------+------------+----------+----------------+
| **     |      |           |            |          |                |
| Commer |      |           |            |          |                |
| cially |      |           |            |          |                |
| Ava    |      |           |            |          |                |
| ilable |      |           |            |          |                |
| Add-On |      |           |            |          |                |
| Cont   |      |           |            |          |                |
| rols** |      |           |            |          |                |
+--------+------+-----------+------------+----------+----------------+
| Sel    | \>90 | Lean      | \$121/hp   | PM:      | Ammonia slip a |
| ective |      | Burn,     | (c         | 0-30,    | concern.       |
| Cat    |      | Diesel,   | apital)^1^ | HC:      | Requires \<500 |
| alytic |      | and       |            | 50-90,   | ppm sulfur     |
| Red    |      | Dual-Fuel | \$36/hp    |          | fuel.          |
| uction |      |           | (          | CO:      |                |
|        |      |           | annual)^1^ | 50-90    |                |
|        |      |           |            | (with    |                |
|        |      |           |            | o        |                |
|        |      |           |            | xidation |                |
|        |      |           |            | c        |                |
|        |      |           |            | atalyst) |                |
+--------+------+-----------+------------+----------+----------------+
| NOxT   | 9    | Diesel    |            | PM:      | Trace ammonia  |
| ech^®^ | 0-95 | and Lean  |            | 60-80,   | of \<2-5 ppmv. |
|        |      | Burn      |            | VOC: 90, |                |
|        |      | Natural   |            | CO:      |                |
|        |      | Gas       |            | 50-70    |                |
+--------+------+-----------+------------+----------+----------------+
| **     |      |           |            |          |                |
| Commer |      |           |            |          |                |
| cially |      |           |            |          |                |
| Ava    |      |           |            |          |                |
| ilable |      |           |            |          |                |
| On-    |      |           |            |          |                |
| Engine |      |           |            |          |                |
| Cont   |      |           |            |          |                |
| rols** |      |           |            |          |                |
+--------+------+-----------+------------+----------+----------------+
| C      | 40   | Diesel^2^ |            | CO: 80,  |                |
| eramic |      |           |            | NMHC: 60 |                |
| C      |      |           |            |          |                |
| oating |      |           |            |          |                |
+--------+------+-----------+------------+----------+----------------+
| Igniti | 0-40 | All       | \$12,00    | CO and   | Combustion     |
| on/Inj | (RB) | Engines   | 0-\$25,000 | HC:      | instability,   |
| ection |      |           | (c         | Little   | loss of power, |
| Timing | 0-20 |           | apital)^3^ | effect   | impacts        |
| Retard | (LB) |           |            | for SI   | exhaust valve  |
|        |      |           | \$6,30     | engines, | life and       |
|        | 1    |           | 0-\$81,000 | no       | turbocharger   |
|        | 5-30 |           | (annual)   | definite | performance.   |
|        | (CI) |           |            | trend in | Increase in    |
|        |      |           |            | diesel,  | brake-specific |
|        |      |           |            | and      | fuel           |
|        |      |           |            | slight   | consumption.   |
|        |      |           |            | increase |                |
|        |      |           |            | in       |                |
|        |      |           |            | du       |                |
|        |      |           |            | al-fuel. |                |
+--------+------+-----------+------------+----------+----------------+
| Water  | 2    | All       |            | No HAP   |                |
| Inj    | 5-35 | E         |            | R        |                |
| ection |      | ngines^4^ |            | eduction |                |
+--------+------+-----------+------------+----------+----------------+
| E      | 4    | All       |            | No HAP   |                |
| xhaust | 8-80 | Engines   |            | R        |                |
| Gas    |      |           |            | eduction |                |
| R      |      |           |            |          |                |
| ecircu |      |           |            |          |                |
| lation |      |           |            |          |                |
+--------+------+-----------+------------+----------+----------------+
| *      |      |           |            |          |                |
| *Under |      |           |            |          |                |
| D      |      |           |            |          |                |
| evelop |      |           |            |          |                |
| ment** |      |           |            |          |                |
+--------+------+-----------+------------+----------+----------------+
| NOx    | \>9  | Diesel    |            | PM:      | Sulfur         |
| Ad     | 0^5^ | and       |            | 10-30,   | degradation    |
| sorber |      | Gasoline  |            | HC: 90,  | and catalyst   |
|        |      |           |            | CO:      | durability.    |
|        |      | (EMx™:    |            | 90^6^    |                |
|        |      | Natural   |            |          | Requires \<15  |
|        |      | Gas and   |            |          | ppm sulfur     |
|        |      | Diesel)   |            |          | fuel.          |
+--------+------+-----------+------------+----------+----------------+
| Ozone  | 8    | All       |            |          | Typically      |
| Inj    | 5-95 | Engines   |            |          | includes a     |
| ection |      |           |            |          | heat recovery  |
|        |      |           |            |          | steam          |
|        |      |           |            |          | generator and  |
|        |      |           |            |          | economizer.    |
+--------+------+-----------+------------+----------+----------------+
| Lean   | \    | Lean Burn |            | CO: 60,  |                |
| NOx    | <30^ | and       |            | NMHC: 60 |                |
| Ca     | 7,8^ | Diesel    |            |          |                |
| talyst |      |           |            |          |                |
+--------+------+-----------+------------+----------+----------------+

^1^Based on averaging cost information from NESCAUM and from Diesel &
Gas Turbine Worldwide.

^2^Tests are underway to determine the effect on gas fired engines.

^3^Costs are based on installing an ignition system, however in certain
cases the ignition system is standard equipment and no purchased
equipment is required. In this case, capital costs are expected to be
\$4,000 or less.

^4^Note that in Table 4 of the NJ SOTA Manual for RICE, water injection
is listed as not applicable to SI lean burn engines.

^5^Note that in information from EC/R's update to EPA's ACT, EMx™ has
been shown to reduce NOx by 95 percent from lean burn engines and 98.9
percent from diesel engines.

^6^Note that according to EC/R's update to EPA's ACT, SCONOx^®^ has been
shown to reduce CO and VOC by up to 95 percent in lean burn engine
exhaust.

^7^Note that information from the Manufacturers of Emission Controls
Association stated that one stationary diesel engine has been equipped
with a lean NOx catalyst and NOx emissions are being reduced by 80
percent.

^8^Note that in Table 5 of the NJ SOTA Manual for RICE, the NOx
efficiency for CI diesel and dual-fuel engines is listed as greater than
90 percent.

-   Requires sulfur levels of less than 500 parts per million (ppm),

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-   Fuel penalty: urea consumption approximately 4 percent of fuel use,

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-   Infrastructure,

-   Requires engine integration: NOx sensor or engine NOx map,

-   Ammonia slip, and

-   Possible vanadium emissions.

*Emissions Reductions*

Selective catalytic reduction is capable of achieving greater than 90
percent reduction for NOx, a 0-30 percent reduction for particulate
matter (PM), a 50-90 percent reduction for hydrocarbons (HC), and a
50-90 percent reduction for carbon monoxide (CO) (with oxidation
catalyst).

*Costs*

Information from the Northeast States for Coordinated Air Use Management
(NESCAUM) and from Diesel & Gas Turbine Worldwide was used to estimate
the costs associated with the purchase, installation, and operation of
SCR on an engine. The information from NESCAUM was based on a 1,030
horsepower (hp) diesel engine equipped with SCR at the National Steel
and Shipbuilding Company in San Diego, California. The total capital
cost including installation for this system was about \$179,000. The
total annual cost was about \$44,000. The information from Diesel & Gas
Turbine Worldwide indicated that the total capital cost including
installation for an SCR system applied to a 2,336 hp engine, achieving a
90 percent reduction in NOx emissions, was \$160,000 with annual costs
of about \$67,000. The cost information from both sources was averaged
together to obtain average costs per hp. Capital costs associated with
SCR were estimated to be \$121/hp with an annual cost estimated to be
\$36/hp. Costs include capital recovery, operation and maintenance, fuel
penalty, and urea. An oxidation catalyst and a NOx continuous emissions
monitoring system (CEMS) can help to reduce ammonia slip. The capital
cost for a NOx CEMS is \$158,000 with an annual cost of \$43,000.

Cost information is available from EC/R's update on NOx control
technologies report which was obtained from a vendor who calculated
costs for two scenarios involving 2,600 hp natural gas fired SI engines.
For the first scenario, three engines each operating 400 hours were
used. For the first scenario, capital costs were calculated at
\$187,000. For the second scenario, one engine operated 2,000 hours per
year. The capital cost for this scenario was calculated at \$68,000.
Capital costs include catalyst, urea control, injectors, engine map,
startup assistance, reagent tank, and installation. The annual costs for
the first scenario were calculated at \$48,200 based on capital recovery
(equipment life of 7 years and 10 percent interest rate) and reagent
costs. The annual costs for the second scenario using the same
assumptions, except that an equipment life of 5 years was used, were
calculated at \$35,680. Note that these costs do not include all cost
elements typically included by EPA. For example, no indirect
installation costs are included in the capital costs. Also, operating
and maintenance costs are not included in the annual costs.

The RJM Corporation, a provider of emission control technologies, was
contacted to obtain cost information about their SCR products. This
company provided SCR technology to a number of diesel fired engines in
the country. The product RJM installs on diesel engines for NOx control
is the RJM ARIS™ SCR Technology. The capital costs for the SCR system
for a 2,336 hp diesel engine range from \$140,000 to \$160,000 depending
on the amount of control (50 to 90 percent NOx reduction). The cost
effectiveness for the RJM SCR varies depending on number of hours of
operation and amount of control desired. For 90 percent NOx control from
a 2,336 hp diesel engine the cost effectiveness is \$3,130 per ton of
NOx removed based on 1,000 hours of operation and ranges to \$738 per
ton of NOx removed based on 8,000 hours of operation. For 75 percent NOx
control from a 2,336 hp diesel engine the cost effectiveness is \$3,422
per ton of NOx removed based on 1,000 hours of operation and ranges to
\$775 per ton of NOx removed based on 8,000 hours of operation.

Caterpillar indicated that its SCR system is capable of reducing NOx
emissions by 90 percent from diesel engines, or down to a level of about
0.7 grams per horsepower-hour (g/hp-hr) from a 7.0 g/hp-hr engine. The
cost for a 1.7 megawatt (MW) (2,278 hp) diesel genset package with SCR
is \$228,000, or \$130/ekw. Caterpillar indicated that this cost
includes the SCR itself for \$133,000, plus the urea tank, control
system, connections, and packaging for \$95,000. Caterpillar also
provided some information on an SCR installation at EXAR, a
semiconductor manufacturer in Freemont, California. At this facility,
SCR had been installed on Caterpillar gas engines to meet 2003
California rules on NOx emissions, according to Caterpillar. The total
SCR and related capital costs were \$450,000, or \$473/ekw, for a plant
totaling 950 ekw in size, according to Caterpillar. These costs include
building modifications, civil works, fixed piping and assembly.
According to Ralph Renee (facilities manager at EXAR), the actual SCR
cost was about \$230/ekw. Maintenance costs at this facility were
estimated at about \$0.01/ekw-hr, with the assumption of a urea price of
\$2-5 per gallon. According to Caterpillar, \$0.01/ekw-hr would probably
cover the total SCR system over time.

*Experience*

Information from EPA's Alternative Control Techniques (ACT) Document
identified a total of 23 SCR installations with lean burn engines in the
United States. A total of nine SCR installations with diesel engines and
27 installations with dual-fuel engines were identified in the United
States. Note that EPA's ACT was published in 1993.

More recent information from EC/R's report (published in 2000), which
was a partial update of EPA's 1993 ACT indicated that at least 44
engines have had SCR installed since 1991. Of these, 38 are compression
ignited (CI) engines, of which 31 are fired with diesel fuel, four are
fired with distillate fuel oil (#2), one is fired with residual fuel oil
(#6), and one dual-fuel engine is fired with diesel and natural gas. The
remaining seven engines are lean burn spark ignited (SI) engines burning
natural gas.

Information was received from catalyst vendor Miratech. Miratech
indicated that there are basically no problems applying SCR to either CI
or SI engines. The vendor stated that worldwide it has expertise with
more than 1,000 SCR installations on engines and within the United
States 70-80 SCR installations on engines.

Information regarding SCR was requested from catalyst vendor Engelhard.
Engelhard referred the request to Stephen Frasch, an independent
consultant and distributor of emission control systems who has used
Engelhard products for the last 10 years and who is also hired by
Engelhard for installation and warranty work in the western United
States. Stephen indicated that they have successfully installed SCR
systems on both diesel and lean burn natural gas engines and that they
have met 0.15 g/bhp-hr for NOx for both fuel types with 10 ppm or less
ammonia slip. According to Stephen, there are over 100 SCR installations
on engines across the United States. Stephen projects to install 10 or
more SCR systems in 2004.

[NOxTech^®^ Emission Control System]{.underline}

According to EC/R's report, NOxTech Inc. has developed the NOxTech^®^
emission control system, which involves chemically treating exhaust
gases with a nonhazardous liquid chemical. The system can be applied to
both diesel and lean burn natural gas fired engines. It replaces the
exhaust silencer on engines with a reaction chamber. At temperatures
between 1,400 to 1,500°F the non-catalytic chemical reagent is injected
into the exhaust. Nitrogen, water vapor, and CO are formed from the
reaction between NOx and the injected reagent. There is no toxic waste
associated with this process, however, there are trace ammonia emissions
of less than 2-5 ppm by volume. The NOxTech^®^ system is fully
automated, installation requires no major modifications, and the system
can be installed in 2 to 3 weeks. To achieve the temperatures required
for the reactions associated with the NOxTech^®^ system, the exhaust gas
must be heated. A heat exchanger is placed downstream from the reactor
to reclaim and reuse this heat energy. According to information on
NOxTech Inc's website, the system can be applied to both retrofit and
new engines. The system is a muffler-size device made of sheet metal and
other readily available materials and parts, which can be installed
easily.

*Emissions Reductions*

Information in EC/R's report indicated that according to NOxTech Inc.,
the emission control system has been proven to remove 90-95 percent of
NOx emissions, 60-80 percent of PM, 90 percent VOC, and 50-70 percent of
CO from the exhaust of the 4,000 hp diesel powered generator on Catalina
Island. According to NOxTech Inc, emissions of gaseous organic, PM, and
CO can be reduced by greater than 80 percent.

*Costs*

According to literature available from NOxTech Inc. website, NOxTech^®^
system capital costs are about \$50-150/bhp-hr for diesel engines. The
company also states on their website that NOxTech^®^ treatment costs are
not expected to exceed about \$1,000/ton of NO~2~ equivalent NOx
reduction. The company claims that the NOxTech^®^ system can provide the
end use a 50 percent cost reduction in comparison with SCR systems.

*Experience*

According to EC/R's report, the NOxTech^®^ system is operating on
several diesel generators owned by Southern California Edison. At its
Catalina Island facility, NOxTech^®^ is used on 2.5 MW (3,350 hp) and
3.8 MW (5,092 hp) diesel electric generators. At its Pebbly Beach
generating station, NOxTech^®^ is used on 1.5 MW (2,010 hp) and 2.8 MW
(3,752 hp) diesel generators.

**On-Engine Control Methods**

[Ceramic Coating]{.underline}

Ceramic engine coatings have been used for several years in stationary
and mobile diesel engines to reduce PM emissions. Ceramic engine
coatings improve combustion by reflecting heat away from coated
components back into the combustion gas path.

*Emissions Reductions*

According to the Manufacturers of Emission Controls Association (MECA),
testing indicated that ceramic engine coating combined with an oxidation
catalyst may reduce NOx emissions from a diesel engine, by allowing the
engine timing to be retarded, by 40 percent. According to MECA,
reductions of 60 and 80 percent for non-methane hydrocarbons (NMHC) and
CO, respectively, are possible with an oxidation catalyst and engine
coatings. One manufacturer of ceramic coatings for diesel engines stated
that significant HC and CO reductions can be achieved, however, an
estimate of the percent reductions are not available. More tests are
underway to better determine the effect of ceramic engine coatings on
diesel as well as gas fired engines.

*Experience*

According to MECA's report regarding emission control technology for
stationary internal combustion engines from 1997, ceramic engine
coatings have been used for almost 5 years in well over 200 stationary
and mobile diesel engines.

[Ignition/Injection Timing Retard]{.underline}

Ignition timing retard can be applied to all new or existing rich and
lean burn engines. This method delays initiation of combustion to later
in the power cycle, leading to a volume increase of the combustion
chamber and a reduced residence time. This may lead to reduced NOx
formation. The extent to which the ignition timing can be retarded to
reduce NOx emissions varies with each engine. Ignition timing increases
exhaust temperatures, which may adversely impact exhaust valve life and
turbocharger performance, and extreme levels of ignition timing retard
may result in combustion instability and a loss of power. Brake-specific
fuel consumption (BSFC) increases.

Injection timing retard applied to CI engines reduces NOx emissions by
the same principles as those for SI engines. Injection timing can be
adjusted on all new or existing CI engines. Retarding the injection
timing leads to the fuel igniting entirely during expansion rather than
igniting initially during compression and then mostly igniting during
expansion. Lower combustion temperature and lower thermal NOx is the
result, however, this also causes increased fuel consumption. In
addition, certain engines may experience problems with high CO and soot
emissions as a result of these changes.

Ignition and injection timing retard modifications can be performed with
a very low capital cost and may also require a few hours of mechanics
time. Some additional hardware or testing is often recommended,
resulting in a total cost of a few thousand dollars. Similar NOx
reductions as those obtained with injection timing retard can be
achieved with ignition timing retard. However, SI engines are typically
more sensitive to timing retard than CI engines, and more operational
problems are associated with SI engines when applied. Therefore, the
level of NOx reduction achievable for SI engines can be more limited
than for CI engines.

Injection timing retard adjustment is not possible on all engines.
Excessive timing retard results in combustion instability and engine
misfire. The BSFC also increases with increasing levels of injection
timing retard for both diesel and dual-fuel engines.

*Emissions Reductions*

The NOx reductions from applying ignition timing retard range from no
reduction to 40 percent for rich burn engines and 0-20 percent reduction
for lean burn engines. Ignition timing retard has little effect on CO
and HC emissions. For CI engines, retarding the injection timing by
about 4 degrees can reduce NOx by 15-30 percent, however achievable NOx
reductions are engine-specific. There is no definite trend for CO and HC
emissions for moderate levels of ignition retard in diesel engines and
there is a slight increase in these emissions in dual-fuel engines.

*Costs*

Costs for ignition and injection timing retard were provided in EPA's
ACT from 1993. For rich burn engines, the capital costs associated with
ignition timing retard range from \$12,000 to \$25,000 with annual costs
ranging from \$6,300 to \$80,000. For lean burn engines, the capital
costs are similar, estimated to range from \$12,000 to \$24,000, with
annual costs ranging from \$7,200 to \$81,000. To obtain and maintain
effective NOx reduction with changes in engine load and ambient
conditions, it is required that the engine be equipped with an
electronic ignition control system to automatically adjust the ignition
timing. In certain cases, the ignition system is standard equipment, in
which case no purchased equipment is required, and capital costs are
expected to be about \$4,000 or less. Annual costs associated with
ignition timing retard are due to an increase in maintenance due to the
electronic ignition control system, an increase in BSFC, emission
compliance testing, and capital recovery.

For diesel engines, injection timing retard is estimated to have capital
costs ranging from \$12,000 to \$24,000 and annual costs ranging from
\$6,200 to \$78,000, based on varying engine sizes between 80-8,000 hp
operating 8,000 hours per year. For dual-fuel engines, the capital costs
range from \$12,000 to \$24,000, with annual costs ranging from \$10,000
to \$57,000, based on engines from 700 to 8,000 hp in size operating
8,000 hours per year. It is anticipated that injection timing retard
will require an automated electronic control system similar to ignition
timing adjustment for SI engines. Capital costs are estimated on the
same basis as ignition timing retard for SI engines. Similarly, annual
costs for injection timing retard are estimated using the same
methodology that was used for SI engines for ignition timing retard.

The Status Report on NOx Controls developed by NESCAUM presented a case
study based on Tennessee Gas Pipeline's facility in Mercer,
Pennsylvania. Ignition timing retard was retrofitted at this facility on
six 1,100 hp Cooper GMV-10 2-stroke natural gas fired engines to meet
Pennsylvania reasonably available control technology (RACT)
requirements. The cost of the retrofit, including commissioning was
\$4,000 per engine. The annual cost associated with this project was
estimated at about \$21,200.

[Water Injection]{.underline}

Water injection as a control method can be used on any engine, but has
been applied primarily to diesel engines for the reduction of NOx. Only
a few engines have been retrofitted to utilize water injection. However,
several engine manufacturers have recently offered such control systems
as techniques on their new engines. Water vapor acts as a heat sink to
reduce peak temperatures, thereby reducing NOx formation.

*Emissions Reductions*

The SOTA Manual for RICE developed by the State of New Jersey Department
of Environmental Protection stated that NOx reductions of 25-35 percent
can be achieved with water injection.

[Exhaust Gas Recirculation]{.underline}

Exhaust gas recirculation can be used on all engine types. It has been
widely used on gasoline and diesel motor vehicle engines for NOx
reduction. This method of control reduces NOx emissions by decreasing
peak combustion temperatures through two mechanisms: dilution and
increased heat absorption.

*Emissions Reductions*

The SOTA Manual for RICE from the State of New Jersey stated that NOx
reductions of 48-80 percent can be achieved with EGR on diesel engines.

**Under Development**

**Add-On Controls**

[NOx Adsorber]{.underline}

A NOx adsorber is a catalyst technology for removing NOx in a lean
exhaust environment for diesel and gasoline fired engines. The
technology is currently on the market for mobile gasoline fired engines,
but still in the research and development phase for diesel. It is
expected to be on the US market 2007 at the earliest. NOx adsorbers
consist of ceramic monolith containing parallel channels, coated with
precious metal catalysts. During lean operation, NOx is stored in the
form of nitrates produced by reactions between the NOx and catalyst. At
regular intervals, a momentary reducing condition (switching to rich
burn) is produced inside the monolith by injecting reductant, causing
the nitrates to decompose to nitrogen.

*Emissions Reductions*

A NOx adsorber is capable of achieving greater than 90 percent NOx
reduction, 10-30 percent reduction of PM, 90 percent reduction of HC,
and 90 percent reduction of CO. Ultra low sulfur diesel fuel (\<15 ppm)
is required to achieve these reductions. This is the technology that the
Office of Transportation and Air Quality (OTAQ) is relying on for
nonroad diesel engines to meet the Tier 4 standards. The following
requirements and difficulties are associated with NOx adsorbers:

-   Requires sulfur levels of less than 15 ppm,

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-   Sulfur degradation and catalyst durability,

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-   Requires engine integration,

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-   Requires a means for supplemental fuel injection,

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-   Currently have no information on fuel penalty, performance penalty
    or costs,

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-   Tremendous system complexity & packaging, and

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-   Costs of precious metals.

*Costs*

Based on information from the regulatory impact analysis for nonroad
diesel engines for NOx adsorber system costs, EPA developed NOx adsorber
costs for stationary CI engines. These costs were presented in the
memorandum entitled "Control Costs for NOx Adsorbers and CDPF for CI
Engines," included in the rulemaking docket (Docket ID No.
OAR-2005-0029). The EPA estimated average total annual control costs for
NOx adsorbers at \$1/hp and capital control costs of \$7/hp. For
example, for a 1,000 hp engine, annual capital control costs are
estimated at \$1,000 per engine, with capital control costs of \$7,000
per engine.

*Experience*

The EMx™ (SCONOx^®^) system was developed by Goal Line Technologies (now
Emerachem) and uses a single catalyst to remove NOx, CO, and VOC
emissions. The system was originally applied to gas turbines, but has
now been developed for use on natural gas and diesel fired engines. The
EMx^TM^ process uses no hazardous materials and all utilities required
to operate the system (natural gas, steam, water, ambient air, and
electricity) are often available at the site. At temperatures between
300 and 700°F, nitrogen dioxide (NO~2~) is absorbed onto the catalyst
surface through the use of a potassium carbonate coating, which reacts
with the NO~2~ to form potassium nitrites. Maximum NOx absorption is
maintained by periodic regeneration of the EMx^TM^ catalyst. The
catalyst is regenerated by passing a controlled mixture of regeneration
gases across the catalyst surface in the absence of oxygen. Water and
elemental nitrogen are formed by the reaction between the regeneration
gases and nitrites. The regeneration gas contains CO~2~ which reacts
with potassium nitrites to form potassium carbonate, the absorber
coating that was on the catalyst surface prior to the oxidation process.

Information from EC/R's report indicated that the vendor tested the
EMx^TM^ system which showed that NOx, CO, and VOC were reduced by up to
95 percent in lean burn engine exhaust. Three EMx^TM^ systems were
purchased for natural gas fired engines and were scheduled to go on line
in May 2000. Preliminary testing of the EMx^TM^ system conducted by
Cummins Engine Company for use on mobile and stationary diesel engines
showed that NOx emissions were reduced by 98.9 percent down to 0.4
g/bhp-hr. Three EMx^TM^ for diesel fired units have been sold but have
not yet been commissioned.

[Ozone Injection]{.underline}

Ozone injection can be applied to all engine types. This control
technique oxidizes NOx to nitrous pentoxide (N~2~O~5~). A water or
caustic scrubber is used to remove the N~2~O~5~ that is highly water
soluble. A heat recovery steam generator and economizer are typically
used to reduce the temperature below 350°F. Temperatures below 350°F
inhibit ozone disassociation and ensure that the efficiency of the NOx
oxidation is optimal.

According to the Status Report on NOx Controls, technologies such as
electro-catalytic oxidation and ozone injection are emerging and offer
the potential for high NOx emission reduction, as well as reduction of
emissions of other pollutants. However, because there is much less
experience with these technologies, available cost information is
limited.

*Emissions Reductions*

The SOTA Manual for RICE from the State of New Jersey stated that NOx
reductions of 85-95 are achievable with ozone injection.

[Lean NOx Catalyst]{.underline}

Lean NOx catalysts are being developed to reduce NOx emissions in the
oxygen-rich exhaust of lean burn engines, particularly diesel engines.
There are two types of lean NOx catalysts; "active" and "passive" lean
NOx catalysts. The "active" lean NOx catalyst injects a reductant that
converts NOx contained in the exhaust gases into nitrogen and oxygen.
Diesel fuel is typically used as the reductant. The presence of the
reductant provides locally oxygen poor conditions which allows NOx
emissions to be reduced by the catalyst.

*Emissions Reductions*

According to OTAQ, active lean NOx catalysts can achieve NOx reductions
up to 30 percent. The passive lean NOx catalyst does not employ
reductant injection. It is therefore more limited in its ability to
reduce NOx emissions. Passive lean NOx catalysts are able to reduce NOx
emissions less than 10 percent. OTAQ noted in its report that lean NOx
catalysts cannot provide the significant NOx reductions necessary for
compliance with the proposed Tier 4 standards.

Information from the Manufacturers of Emission Controls Association's
status report on emission control technology for stationary engines,
indicated that one stationary diesel engine was equipped with a lean NOx
catalyst and NOx emissions were being reduced by 80 percent, CO by 60
percent, and NMHC emissions by 60 percent.

According to the SOTA Manual for RICE from the State of New Jersey, lean
NOx catalysts are capable of achieving NOx reductions of 90 percent or
greater for CI diesel and dual fuel engines.

**References**

1\. Status Report on NOx Controls for Gas Turbines, Cement Kilns,
Industrial Boilers, Internal Combustion Engines. Technologies & Cost
Effectiveness. Northeast States for Coordinated Air Use Management.
December 2000.

2\. Alternative Control Techniques Document \-- NOx Emissions from
Stationary Reciprocating Internal Combustion Engines. Report.
EPA-453/R-93-032. July 1993.

3\. Steve Strong, Miratech to Tanya Ali, Alpha-Gamma Technologies.
Email. Questions Regarding SCR and NSCR for Stationary IC Engines.
January 28, 2004.

4\. Draft Regulatory Impact Analysis: Control of Emissions from Nonroad
Diesel Engines. Assessment and Standards Division, Office of
Transportation and Air Quality, U.S. Environmental Protection Agency.
EPA420-R-03-008. April 2003.

5\. State of the Art (SOTA) Manual for Reciprocating Internal Combustion
Engines. Effective Date: 2003. State of New Jersey Department of
Environmental Protection.

6\. Steve Strong, Miratech to Tanya Ali, Alpha-Gamma Technologies.
Email. Questions Regarding SCR and NSCR for Stationary IC Engines.
February 13, 2004.

7\. Emission Control Technology for Stationary Internal Combustion
Engines. Status Report. Manufacturers of Emission Controls Association.
July 1997.

8\. Stationary Reciprocating Internal Combustion Engines Updated
Information on NOx Emissions and Control Techniques. Revised Final
Report. EC/R Incorporated. September 1, 2000.

9\. Tanya Ali, Alpha-Gamma Technologies to Stephen Frasch, Stephen
Frasch Consulting. Telecon. Information Regarding SCR and NSCR for
Stationary Engines. February 4, 2004.

10\. Stephen Frasch, Stephen Frasch Consulting to Tanya Ali, Alpha-Gamma
Technologies. Email. IC Engine SCR and NSCR. February 9, 2004.

11\. Stationary Diesel Engines in the Northeast: An Initial Assessment
of the Regional Population, Control Technology Options and Air Quality
Policy Issues. Northeastern States for Coordinated Air Use Management.
June 2003.

12\. SCR Economics for Diesel Engines. Diesel & Gas Turbine Worldwide.
July-August 2001.

13\. NOxTech Inc. March 17, 2004.

14\. Nick Huff, Miratech to Jennifer Snyder, Alpha-Gamma Technologies.
Email. SCR Questions for RICE MACT. October 23, 2003.

15\. Stationary Reciprocating Internal Combustion Engines Technical
Support Document for NOx SIP Call. Doug Grano and Bill Neuffer, EPA,
October 2003.

17\. Interstate Ozone Transport: Response to Court Decisions on the NOx
SIP Call, NOx SIP Call Technical Amendments, and Section 126 Rules;
Final Rule. 40 CFR Parts 51, 78, and 97. 69 FR 21604, April 21, 2004.

18\. Gordon Gerber, Caterpillar to Melanie Taylor, Alpha-Gamma
Technologies. Email. Cost of Caterpillar SCR System. April 22, 2004.

19\. Exhaust Emission Controls Available to Reduce Emissions from
Nonroad Diesel Engines. Manufacturers of Emission Controls Association.
April 2003.

20\. Caterpillar Engine Research Diesel & Emissions Technology. 2002.