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?
•How much is used?
•What if I run out?
•DEF storage, handling, quality, specifications
•Best packaging
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 other diesel 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.
Who Supports SCR…
Diesel engine manufacturers Cummins, Detroit
Diesel, Volvo, Mack, Hino, Isuzu and PACCAR are
supporting SCR technology.
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, NC•
², to develop and market trucks using
•
Navistar’s A-EGR technology.
The Basic SCR Emission Control System
Nitrogen
+
Engine
DPF
SCR
Water
DEF Injection
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 important
Then we’ll be able to cover more about DEF.
vaporizer
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.
vaporizer
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-flammable
No 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 Quality is 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.
DEF Specification: ISO 22241-1
Shelf Life
Clogs DEF
Injection Nozzle
Lacquer
Poisons
SCR Catalyst
Specification
Limits
Urea
Density at 77OF
Refractive Index at 77OF
Alkalinity (as ammonia)
Insolubles
Calcium
Magnesium
Aldehydes
Sodium
Potassium
Phosphates
Biuret
Aluminum
Iron
Copper
Zinc
Chromium
Nickel
31.8 – 33.2 wt%
9.05 – 9.09 lbs/gal
1.3814 – 1.3843
Max. 0.2 wt%
Max. 0.002 wt%
Max. 0.00005 wt%
Max. 0.00005 wt%
Max. 0.0005 wt%
Max. 0.00005 wt%
Max. 0.00005 wt%
Max. 0.00005 wt%
Max. 0.3 wt%
Max. 0.00005 wt%
Max. 0.00005 wt%
Max. 0.00002 wt%
Max. 0.00002 wt%
Max. 0.00002 wt%
Max. 0.00002 wt%
DEF Quality is 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 DEF
Or, 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
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.
Shelf Life as a Function of Temperature*
Constant Ambient Storage
Temperature
Minimum Shelf Life
In Months
Below 50°F
36
50 to 77°F
18
77 to 86°F
12
86 to 95°F
6
Above 95 °F
Check every batch before use
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
Incompatible Materials
Carbon Steel, Zinc coated carbon steels, mild iron
Non ferrous metals and alloys: copper, copper alloys, zinc, lead
Solders containing lead, silver, zinc, or copper
Aluminum, aluminum alloys
Magnesium, magnesium alloys
Plastics or metals coated with nickel
Materials Compatible with DEF
Compatible Materials
Stainless Steel 304, 304L, 316 or 316L
Titanium
Hastelloy c/c-276
Polyethylene, free of additives
Polypropylene, free of additives
Polyisobutylene, free of additives
Perfluoroalkoxyl alkane (PFA), free of additives
Polyfluoroethylene (PFE), free of additives
Polyvinylidenefluoride (PVDF), free of additives
Polytetrafluoroethylene (PTFE), free of additives
Copolymers of vinylidenefluoride and hexafluoropropylene, free of
additives
Compatible Hose & Nozzle Materials
Compatible Hoses
PVC Chemical Hose
EPDM Hose
Poly Hose
Compatible Nozzles
Stainless Steel Automatic Shut off nozzle
Plastic nozzle with non-automatic shut off.
Cleanliness of Surfaces
All 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 worldwide standard for DEF
Meets 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
CAM2 DEF
Available in: 1 or 2 gallon bottles, 55 gal drums, 275 gal totes