About SCR and DEF. Diesel Exhaust Fluid. About SCR and DEF. Diesel Exhaust Fluid. What this presentation will cover… EPA 2010 mandates for diesel engines Who is impacted? What are the solutions and who is providing them? What is SCR and how does it work? What is DEF? How is it used?
Diesel Exhaust Fluid
Diesel Exhaust Fluid
The Problem…The EPA has mandated that as of January 1, 2010, newly manufactured engines for all Class 6, 7, 8 diesel trucks shall reduce the emission of oxides of nitrogen (NOx) by more than 90% from 2007 levels, that is, to near zero levels. All otherdiesel engines must be compliant by 2015, including off-highway, railroad and marine.
The Dominant Solution…This has required the development of new emission control systems. Approximately 80% of diesel vehicles to be produced will use SCR.
What is SCR…SCR is an acronym for Selective Catalytic Reduction, an Emission Control System in the exhaust system downstream from the engine and DPF (Diesel Particulate Filter).SCR Emission Control Systems consist of a catalyst, a reducing agent (DEF), and a dosing system which injects a mist of the reducing agent DEF into the hot exhaust.
The competing solution is A-EGR.A-EGR is an acronym for Advanced Exhaust Gas Recirculation. EGR is currently used with diesel engines, but, to reduce NOx to 2010 levels, it must be used more aggressively. This system does not use DEF.At this time, Navistar/ International Trucks is the only North American engine manufacturer using this solution and is projected to account for less than 20% of the market. Caterpillar and Navistar have also formed a joint venture, NC², to develop and market trucks using Navistar’s A-EGR technology.
A mist of DEF is vaporized in the heat of the exhaust forming ammonia and carbon dioxide, which then reacts with the SCR system catalyst and NOx emissions, converting NOx to nitrogen and water, which are harmless.
What is DEF…DEF is Diesel Exhaust Fluid, the consumable reducing agent used in Selective Catalytic Reduction systems.DEF is a clear, non-toxic liquid, specifically a high purity 32.5% Aqueous Urea Solution.SCR is the system which uses DEF to reduce NOx (nitrogen oxides) to near zero levels in order to meet the 2010 EPA mandates.
Let’s look at the SCR system in greater detail…The next several slides will give details as to:· How SCR works· Why we use an Aqueous Urea Solution, that is, water mixed with urea· How it’s monitored and controlled· Why quality and purity are so importantThen we’ll be able to cover more about DEF.
DEF is a high purity 32.5% Aqueous Urea Solution. Urea is a compound of nitrogen that turns into ammonia when heated. A mist of DEF is injected into the hot exhaust through a vaporizer or evaporator downstream of the engine and diesel particulate filter. The DEF mist vaporizes, forming ammonia and carbon dioxide.
NOx (exhaust byproduct we want to eliminate), ammonia and carbon dioxide then react with the SCR catalyst to convert virtually all NOx emissions to nitrogen and water. Sensors and a controller monitor for quantity and quality, and adjust the operation of the system.
SCR catalytic converter
There is good experience with SCR.· This process was invented in 1957 and first placed in commercial use in 1978 to reduce NOx emissions from fossil fuel plants.· It has been in use in Europe for about 3 years.· It has been field tested by manufacturers such as Mack Trucks for more than 4 years.
Experience shows that SCR Systems, among other benefits, will improve fuel economy by 3 to 5%, reducing operating costs below current levels, even including the cost of DEF.
DEF in more detail…DEF – Diesel Exhaust Fluid – is a high purity solution of 32.5% automotive grade urea and 67.5% de-ionized (demineralized) water. Urea (a nitrogen compound) turns to ammonia when heated. It is used in lower grades for other purposes, such as fertilizer.DEF is… · non-toxic · non-hazardous · non-polluting · non-flammableNo special handling is required
Why a 32.5% solution? It provides the lowest freeze point, and both the urea and water will freeze and thaw at the same rate, maintaining the concentration for optimum SCR system performance.If DEF freezes it may be thawed without degradation.
DEF Qualityis critical…Automotive grade urea must be used. Lower grade urea will foul system components and poison the SCR catalyst.67.5% of the solution is water, which must be high purity, de-ionized water, with specifications for mineral (solids) content.The specification standard for DEF is ISO 22241.
Clogs DEF Injection Nozzle
DEF Qualityis critical.DEF cannot be “thinned” to a lower concentration, the controller will pump more DEF and then reduce engine power if sufficient levels of urea are not present.If high purity de-ionized water is not used, SCR system components will foul, especially the vaporizer (or evaporator), which is the most susceptible part. This will reduce performance and force premature service.Then the truck will only run in “limp-home” mode.
If you run out of DEF…You cannot substitute any other fluid, including water.If you run out of DEFOr, if the DEF solution is altered…Initially, engine power is reduced and truck speed will top out at 55mph. If not cured, after a while truck speed reduces to 5mph.Then the truck will only run in “limp-home” mode.
DEF Tank · Holds approx 18 to 20 gallons of DEF
· Is plastic so it won’t corrode
· Can expand if DEF freezes (7% expansion)
· Has a temperature sensor and heater · Has a blue cap and a 19mm opening · Diesel tank has a 22mm opening · A diesel fuel nozzle won’t fit into a DEF tank
DEF Consumption…DEF will be consumed at a rate of about 2 gallons for every 100 gallons of diesel fuel (averaged among engine manufacturers).Actual usage will vary with driving conditions and engine performance.Example: Class 8 truck traveling 120,000 miles/year with a 20 gal reservoir will require ~20 refills/yr = 400 gals. It is estimated 16 to 50 million gallons will be needed in 2010 alone, the 1st year of compliance.
DEF Storage…DEF freezes at 12°F, but freezing will not degrade DEF. It can be used again, once it thaws.DEF truck tanks and lines are equipped with heater systems so DEF will flow, even at startup in cold weather.DEF should be stored in closed containers at temperatures between 10 and 86°F. Above 86°F, shelf life may begin to degrade to less than a year.
Additional factors in addition to Temperature are:
· Initial alkalinity
· Vented versus non-vented containers
*Reference: ISO 22241-3 document
DEF Containers and Transport…DEF is highly corrosive, such as to aluminum, copper, brass and zinc.DEF must be stored in approved containers such as HDPE plastic or stainless steel. Containers should not be clear or semi-transparent, they let in sunlight which will degrade DEF more quickly. CAM2 DEF containers are white to block sunlight and not heat up as quickly if exposed to the sun.
Materials Incompatible with DEF
Cleanliness of SurfacesAll surfaces in direct contact with DEF need to be free of foreign matter such as: · Fuel · Grease · Oil · Detergent · Dust · Any other substance
What this all means is… · for ease of filling · to avoid running out of DEF · to maintain the shelf-life, quality and purity of DEF The best delivery methods are white plastic bottles; plastic drums and totes.2 gallon bottles make more sense than 1 gal as tanks hold approx 20 gal, 2 gallons needed to re-start a dry system.
Summary· 2 competing solutions for 2010 EPA mandate: A-EGR and SCR –Selective Catalytic Reduction· SCR is the dominant solution, more than 80% of heavy duty trucks made after Jan 1, 2010 will require DEF· About 2 gallons of DEF is required for every 100 gal diesel fuel· DEF quality is critical for operation and service life· ISO 22241 spec is international standard for DEF.· Truck power reduced with low quality or no DEF· DEF is corrosive; needs clean delivery· Best supplied in plastic bottles, drums and totes
CAM2 DEF…Meets ISO 22241 specifications, the established world-wide standard for DEFMeets or exceeds SCR manufacturer’s performance requirements (Cummins, Detroit Diesel, Volvo, Mack, Hino, Isuzu, PACCAR)CAM2 DEF Meets All Applicable Standards and Specifications for use in all SCR Emission Control Systems
Available in: 1 or 2 gallon bottles, 55 gal drums, 275 gal totes