SCR (Selective Catalytic Reduction) is an advanced active emissions control technology system that injects a liquid-reductant agent into the exhaust stream of a diesel engine through a specific catalyst. Automotive-grade urea, often known as Diesel Exhaust Fluid, is commonly used as a reductant (DEF). The DEF initiates a chemical reaction that transforms nitrogen oxides to nitrogen, water, and trace amounts of carbon dioxide (CO2), which is then ejected through the vehicle tailpipe.
SCR technology allows for nitrogen oxide (NOx) reduction processes to occur in an oxidizing environment. It’s named “selective” because it uses ammonia as a reductant within a catalyst system to minimize NOx levels. The reducing agent is DEF, which combines with NOx to turn the pollutants into nitrogen, water, and trace amounts of CO2. The DEF in the exhaust stream can be rapidly broken down to produce oxidizing ammonia. SCR technology alone can reduce NOx emissions by up to 90%.
*This schematic does not represent the approach taken by all manufacturers to attain near-zero emissions.
Why is SCR important?
One of the most cost-effective and fuel-efficient systems for reducing diesel engine emissions is SCR technology. After January 1, 2010, all heavy-duty diesel truck engines must meet the current EPA emissions requirements, which are among the strictest in the world, decreasing particulate matter (PM) and nitrogen oxides (NOx) to near-zero levels. SCR may reduce NOx emissions by up to 90% while also lowering HC and CO emissions by 50% to 90% and PM emissions by 30 to 50%. SCR systems can also be used in conjunction with a diesel particulate filter to reduce PM emissions even further. Some SCR-equipped truck operators in the commercial trucking industry are claiming fuel economy gains of 3-4 percent. Off-road equipment, such as construction and agricultural machinery, must also comply with the EPA’s Tier 4 emissions regulations, which require equal reductions in NOx, PM, and other pollutants. SCR is one technology that can assist off-road vehicles in meeting these rigorous emissions regulations.
Where is SCR used?
SCR has been used to reduce stationary source emissions for decades. SCR technology has also been installed on maritime vessels around the world, including cargo ships, ferries, and tugboats. SCR is being recognized as an emissions control technology that is particularly helpful in meeting the U.S. EPA 2010 diesel engine emission standards for heavy-duty vehicles and the Tier 4 emissions standard for engines found in off-road equipment due to its superior return in both economic and environmental benefits. SCR systems are increasingly being found in diesel passenger automobiles.
What are the special considerations of using SCR?
The necessity to replace Diesel Exhaust Fluid (DEF) on a regular basis is a distinctive feature of a vehicle or machine with an SCR system. DEF is stored in an onboard tank that must be replenished by the operator on a regular basis depending on vehicle activity. DEF refill periods for light-duty cars are usually around the time of a recommended oil change, however DEF replenishment for heavy-duty vehicles and off-road machines and equipment varies based on operating circumstances, hours used, miles traveled, load factors, and other factors.
DEF is an essential component of the emissions control system and must be kept in the tank at all times to ensure the vehicle’s or equipment’s ongoing operation. The driver or operator is alerted by a sequence of rising visual and aural signs when the DEF supply is low. The starting system may be locked out the next time the vehicle is used if the tank reaches a particular level near empty, preventing the car from being started without sufficient DEF. To fulfill the demands of a developing SCR technology industry, a nationwide DEF distribution system has rapidly evolved.
DEF tanks are usually found in the spare tire region of passenger cars, while a DEF tank is usually found alongside the diesel fuel saddle tank on tractor trailers. To prevent DEF from freezing at temperatures below 12 degrees Fahrenheit, proper storage is essential, and most vehicle DEF dispensing systems contain warming mechanisms.
What is the Future for SCR Technology?
Through the “Cleaner Trucks Initiative,” the US Environmental Protection Agency (EPA) announced plans to achieve more stringent tailpipe emission limits for commercial vehicles that are close to zero. SCR systems will need to be refined and improved in order to achieve closer-to-zero emissions. Dosing events, compact designs, and the integration of SCR systems into commercial vehicles will all help to reduce emissions.
What is DEF?
DEF (Diesel Exhaust Fluid) is a non-toxic fluid made up of purified water and aqueous urea of automotive grade. DEF comes in a range of packaging and dispensing options. Bulk, totes, bottles, and jugs are just a few of the storage options available. DEF is thoroughly tested by the American Petroleum Institute to verify that it fulfills industry-wide quality requirements.
DEF can be purchased at a variety of sites, including truck stops, truck dealerships, and engine wholesalers, which can be found using one of the links below. Depending on the truck’s application, DEF tanks range in size from 5 to 22 gallons. To ensure that only DEF is placed into the tank, the DEF tank fill aperture is designed to accommodate a DEF fill nozzle. The DEF tank aperture is too small for a diesel fuel nozzle. The DEF tank also has a blue lid to distinguish it from the diesel tank.
Why do I need DEF?
Most engine manufacturers are using selective catalytic reduction (SCR), which requires DEF to work, to fulfill stringent NOx emission limits beginning in 2010 for commercial vehicle engines and commencing in 2014 for most off-road engines. SCR-equipped engines have exhibited a five percent gain in fuel efficiency. Typically, you’ll need three times the amount of DEF as you do fuel.
Need DEF? Check out the DEF Locator below to find it near you!
DEF is readily accessible in truck stops, auto parts stores, and other retail places across the country in bulk dispensers and smaller portable containers. DEF is also delivered to private garages or fuel station pumps by bulk tanker.
How does an SCR work diesel?
SCR (Selective Catalytic Reduction) systems are used to minimize dangerous Nitrous Oxide (NOx) emissions from diesel cars. It works by pumping automotive-grade urea, or Diesel Exhaust Fluid (DEF), into the exhaust stream of a diesel engine through a specifically designed catalyst.
The NOx is converted to nitrogen, water, and very minute amounts of CO2 through a chemical process triggered by the Diesel Exhaust Fluid. SCR technology can reduce NOx emissions by up to 90%.
Why is SCR important?
One of the most cost-effective and fuel-efficient systems for reducing diesel engine emissions is SCR technology. Its efficiency allows diesel engines to be adjusted and optimized for optimal fuel efficiency, while SCR systems treat the engine-out exhaust effectively.
Heavy-duty commercial trucks are the most common application of SCR technology in the United States.
After January 1, 2010, all heavy-duty diesel truck engines must meet the current EPA emissions requirements, which are among the strictest in the world, decreasing particulate matter (PM) and nitrogen oxides (NOx) to near-zero levels. SCR may reduce NOx emissions by up to 90% while also lowering HC and CO emissions by 50% to 90% and PM emissions by 30 to 50%.
Some SCR-equipped truck operators in the commercial trucking industry are claiming fuel economy gains of 3-5 percent. Off-road equipment, such as construction and agricultural machinery, must also comply with the EPA’s Tier 4 emissions regulations, which require equal reductions in NOx, PM, and other pollutants. SCR is also employed in off-road engines and equipment in a variety of applications.
Where is SCR used?
For decades, SCR has been utilized to minimize stationary source emissions from a variety of industrial processes. SCR technology has also been installed on maritime vessels around the world, including cargo ships, ferries, and tugboats. SCR is being recognized as an emissions control technology that is particularly helpful in meeting the U.S. EPA 2010 diesel engine emission standards for heavy-duty vehicles and the Tier 4 emissions standard for engines found in off-road equipment due to its superior return in both economic and environmental benefits. SCR systems are increasingly being found in diesel passenger automobiles.
What are the special considerations of using SCR?
The necessity to replace Diesel Exhaust Fluid (DEF) on a regular basis is a distinctive feature of a vehicle or machine with an SCR system. DEF is stored in an onboard tank that must be refilled on a regular basis by the operator. Vehicle operation determines DEF consumption rates. DEF consumption will rise as a result of more aggressive driving at faster speeds or when hauling large loads. DEF refill intervals are usually about the time of a recommended oil change or other regular vehicle maintenance for most light-duty cars. DEF replenishment for heavy-duty vehicles and off-road machines and equipment varies based on operating circumstances, hours driven, miles traveled, load factors, and other factors.
DEF is an essential component of the emissions control system and must be kept in the tank at all times to ensure the vehicle’s or equipment’s ongoing operation. The driver or operator is alerted by a sequence of rising visual and aural signs when the DEF supply is low. The vehicle starting system may be shut out the next time the vehicle is used if the tank hits a particular level near empty, preventing the vehicle from being started without sufficient DEF.
What is DEF?
To fulfill the demands of a developing SCR technology industry, a nationwide DEF distribution system has rapidly evolved. DEF has been widely accessible for purchase since 2010, including at fuel stations, convenience stores, auto parts stores, Wal-Mart, and petroleum retailers, as well as truck stops, truck dealerships, and engine wholesalers. Vehicle DEF tanks typically range in size from 6 to 23 gallons, depending on the type of vehicle. To ensure that only DEF is placed into the tank, the DEF tank fill aperture is designed to accommodate a DEF fill nozzle. The DEF tank aperture is too small for a diesel fuel nozzle.
Most heavy-duty truck manufacturers estimated the operating expenses of new SCR-equipped vehicles on a DEF price of $3 per gallon; however, DEF prices fluctuate to supply and demand market conditions and are predicted to fall as the DEF supply network expands.
How does a reduction catalyst work?
To minimize hazardous pollutants, catalytic converters use reduction and oxidation (redox) reactions.
They use a platinum and rhodium-based reduction catalyst. By removing nitrogen atoms from nitrogen oxide molecules, it aids in the reduction of nitrogen oxides (NOx) (NO and NO2). This allows for the formation of oxygen gas from free oxygen (O2). The nitrogen atoms bound to the catalyst then react with one another. Nitrogen gas is produced as a result of this process (N2).
What is an SCR in a diesel engine?
SCR is an exhaust after treatment device that reduces NOx emissions by controlling particulate matter (PM) production and keeping it below permitted limits. Aqueous urea solution (AUS 32) is dispersed into the exhaust stream using SCR. In the presence of a catalyst, ammonia from AUS32 interacts with NOx to create innocuous by-products such as nitrogen and water vapor. As a result, clean gases are produced. SCR technology is more suited to heavy-duty applications (e.g. long haul heavy trucks & tractors, intercity bus etc.)
What is a SCR System?
The Selective Catalytic Reduction (SCR) system is a high-tech NOx-reduction exhaust aftertreatment system. The engine limits the amount of PM produced by increasing the combustion temperature and keeping it within the acceptable range. While doing so, NOx levels rise, which is then reduced outdoors utilizing a catalytic reduction process. Aqueous urea solution (AUS 32) is dispersed into the exhaust stream using SCR. In the presence of a catalyst, ammonia from AUS32 interacts with NOx to create innocuous by-products such as nitrogen and water vapor. As a result, clean gases are produced.
How is a SCR engine beneficial?
Because of its higher combustion efficiency, the SCR system provides more power and better fuel economy. Engines with clean combustion are more reliable. A reliable solution for dealing with poor gasoline quality that gives the client a longer engine life. It allows for longer maintenance intervals. AUS 32 – The SCR system requires a dosing pump to inject an aqueous urea solution (AUS 32). Diesel Exhaust Fluid (DEF) is the name given to the solution in North America, AdBlue is the name given to it in Europe, and AUS 32 is the name given to it in India. The solution is appropriate for usage in Indian climates.
What is SCR catalyst made of?
The active catalytic components of SCR catalysts are mainly oxides of base metals (such as vanadium, molybdenum, and tungsten), zeolites, or various precious metals, and the catalysts are manufactured from various porous ceramic materials utilized as a support, such as titanium oxide. Another catalyst based on activated carbon that can remove NOx at low temperatures has also been developed. Each catalyst component has its own set of benefits and drawbacks.
Base metal catalysts, such as vanadium and tungsten, are less expensive and perform well in the temperature ranges most typically used in industrial and utility boiler applications. The usage of a diesel particulate filter with forced regeneration in automotive SCR applications necessitates a high level of thermal durability. They also have a strong oxidation catalytic potential.
What is SCR delete?
One of the best things you can do to extend the life of your diesel pickup truck is to eliminate the SCR system. Improve the Ford Powerstroke, Ram Cummins, and GM Duramax’s durability and dependability by removing one of the weakest connections. By removing the SCR, you will no longer need to use Diesel Exhaust Fluid (DEF). The SCR and DPF must both be eliminated at the same time, and this must be done using a DPF delete tuner.
What is SCR efficiency?
Emission Limits/Reductions Achievable: NOx reduction efficiencies of 70 to 90 percent are possible using SCR (ICAC, 2000). Higher cuts are feasible, but they are usually not cost-effective.
What is ammonia slip in SCR?
SCR (Selective Catalytic Reduction) is a technique for reducing NOx emissions by converting NOx to nitrogen (N2) and water (H20) through a reaction between NOx and ammonia (NH3). De-NOx is a term used to describe this reaction. Ammonia Slip is the term for this surplus NH3.
How is SOx and NOx formed?
Because of the sulphur concentration in the fuel, SOx or sulphur oxides are generated during the combustion process in the engine. More information can be found here.
The methods and technology used to minimize sulphur emissions from marine engines are listed below.
8. Low-sulfur fuel oil: This is the most expensive but widely utilized means of complying with Annex VI of MARPOL when entering an emission controlled area, or ECA.
9. Exhaust Gas Scrubber Technology: The engine’s exhaust gas is transported through a scrubber tower, which is then sprayed with a liquid. The scrubbing liquid is made up of fresh water and caustic soda (NaOH), which decreases SOx by 95%. The cleaning water is subsequently dumped overboard after passing through a water treatment effluent emulsion breaking plant.
10.Cylinder Lubrication: Good cylinder lubrication, combined with efficient control systems like Pulse or Alpha lubrication, can neutralize sulphur in the fuel and reduce SOx emissions from the engine.
Are there any other ways or technologies for reducing SOx and NOx emissions from marine diesel engines that you are aware of? Please let us know.
