Compact SCR™ For Diesel Engines
Selective Catalytic Reduction (SCR) is the most effective technique for reducing oxides of nitrogen (NO x) from diesel engines and most other pollution sources. SCR has been used for more than 30 years on large stationary pollution sources such as power plants. Until recently, however, the size, weight, and cost of SCR systems them impractical for small–scale and mobile applications.
Some heavy–duty trucks and European diesel passenger cars are now being sold with SCR systems (e.g. Mercedes "Blue–Tec®"), but these systems are available on a limited range of models and are tightly integrated with the engine controllers.
EF&EE's Compact SCR™ systems uses the same new technology originally developed for heavy–duty diesel truck engines to meet Euro 5 and U.S. 2010 emission standards. Compared to the old–style SCR systems designed for stationary sources, EF&EE Compact SCR™ systems are about 1/5th the size and weight. Unlike the SCR systems sold with new engines, EF&EE's Compact SCR™ sytems are designed as "bolt–on" retrofits, independent of the engine controller. This makes them practical for retrofit — either to existing engines or to new engines not factory–produced with SCR.
EFFECTIVE
Compact SCR™ systems can be spec'd to reduce NOx emissions from existing diesels by 90 to 98%, depending on the exhaust temperature. The Compact SCR™ catalyst is also a highly–effective diesel oxidation (DOX) catalyst. Diesel PM emissions are typically reduced by 40 to 60%, total HC by 80%, and CO by more than 90%. Even larger PM reductions can be obtained by combining Compact SCR™ with diesel particulate filters (DPFs).
Cost–Effective
EF&EE's Compact SCR™ systems are designed for ruggedness and reliability. Economies of mass production in the key components make it highly cost–effective, even in small–scale applications. In most cases, a Compact SCR™ retrofit will enable an older diesel to meet current emission standards, thus avoiding the cost of repowering or replacement.
The reductant used in Compact SCR™ systems is "diesel exhaust fluid" (DEF) — a non–hazardous solution of urea in water. This material is now widely available at truck stops and through fuel distributors. Urea is a non–toxic chemical, and is widely used as fertilizer. The volume of DEF required is typically 2% to 6% of the diesel fuel consumption.
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 M/V GEMINI and performance improvement with EF&EE SCR.  |
Compact SCR™ Applications
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Compact SCR™ in Harborcraft
New construction —The ferries Gemini, Pisces, Scorpio, and Taurus are all equipped with Compact SCR™ systems on their 1410 horsepower main engines. All four boats were ordered by the Water Emergency Transit Authority (WETA) for service in San Francisco Bay. To mitigate the environmental impact of the new ferry services, the WETA specification required cruise emissions from the new boats to be 85% below Tier 2 levels. Acceptance testing showed the actual emissions to be 96% below Tier 2, and within EPA Tier 4 emission limits. NOx was reduced by 97% and PM by about 60% compared to engine–out emissions.
Retrofit — Under an agreement with the National Park Service, Compact SCR™ systems have been retrofit to the main and generator engines in two passenger ferries plying between San Francisco and Alcatraz Island. The first vessel, Alcatraz Flyer, returned to service in February, 2008, and has accumulated more than 4,000 operating hours to date. The second, Alcatraz Clipper, re–entered service in September, 2008, and has accumulated more than 3,000 operating hours.
The Alcatraz ferries are equipped with two 625 hp main engines each. The Compact SCR™ catalyst assemblies for these engines are 44 x 51 x 16 inches, and weigh about 350 pounds. They easily fit in the existing engine room.
 
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Acceptance
Testing data |
M.V. Pisces |
M.V. Gemini |
M.V. Scorpio |
| Emissions (g/kWh) |
Emissions (g/kWh) |
Emissions (g/kWh) |
| 85% Power Cruise |
Port Main |
Stbd Main |
Port Main |
Stbd Main |
Port Main |
Stbd Main |
| NOx (Measured) |
0.18 |
0.28 |
0.01 |
0.18 |
0.24 |
0.28 |
| Particulate Matter (Measured) |
0.023 |
0.022 |
0.048 |
0.021 |
0.023 |
0.026 |
| CO (Measured) |
0.02 |
0.03 |
0.04 |
0.10 |
0.09 |
0.08 |
| Hydrocarbons (Estimated) |
0.02 |
0.02 |
0.02 |
0.02 |
0.02 |
0.02 |
| Total NOx+PM+HC w/ SCR |
0.22 |
0.32 |
0.08 |
0.22 |
0.29 |
0.33 |
| NOx+PM+HC WETA Contract Requirements |
1.11 |
| NOx+PM+HC EPA Tier 2 Emission Standards |
7.4 |
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Compact SCR™ installation in M/V Alcatraz Clipper
CARB rules and funding opportunities — The Carl Moyer Program and similar grants have paid for repowering many California vessels. Adding Compact SCR™ to a repower grant proposal can double or triple the emission reductions, improving the cost–effectiveness and increasing the maximum grant available.
A new CARB rule makes repowering and/or emission control retrofits mandatory for most harbor craft between 2011 and 2016. To be eligible for grant funding, these retrofits must be completed three years before the deadline. Compact SCR™ systems are available today to allow many existing engines to meet this rule.
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Compact SCR™ in Locomotives
High shock and vibration, limited space, and extended periods of engine idling make railway locomotives one of the most challenging applications for SCR.
In February 2009, Metrolink No. 865 became the first SCR–equipped locomotive in North America. A specially–designed, shock–mounted Compact SCR™ catalyst assembly replaced the silencer on the locomotive's 3000 hp EMD 12–710G3 diesel engine. The Compact SCR™ control system monitors throttle notch setting, and tractive power output, and adjusts the reductant injection rate accordingly.
The prototype system operated successfully for several months before suffering cracks in the catalyst monoliths. A redesigned catalyst assembly was installed in June, 2010, and has accumulated more than 1,000 operating hours and eliminated more than 2 tons of NOx with no sign of catalyst deterioration.
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The 24 Catalyst Manifold for LA Metrolink Locomotive #865; Installed February, 2009.
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Compact SCR™ in Mobile Equipment
  New CARB regulations on construction machinery and cargo-handling equipment will require most of these machines to be replaced or retrofit with emission controls. Compact SCR™ technology has been demonstrated successfully in on-road tractor trailers, and in generating sets like those used on rubber-tired gantry cranes. A system combining Compact SCR™ with a diesel particulate filter for a D9 bulldozer is under development.
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| EMD 12-710G3 Emissions |
Emissions - g/BHP-hr |
| PM |
CO |
NOx |
HC |
| Line Haul Cycle |
| Baseline |
0.290 |
0.97 |
9.00 |
0.06 |
| Compact SCR |
0.115 |
0.17 |
2.64 |
<0 |
| Reduction |
61% |
82% |
71% |
100% |
| Switch Cycle |
| Baseline |
0.273 |
1.78 |
11.80 |
0.06 |
| Compact SCR |
0.116 |
0.12 |
4.60 |
<0 |
| Reduction |
57% |
93% |
61% |
100% |
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