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Selective Catalytic Reduction (SCR)
Diesel Exhaust Fluid (DEF)
CAT, CATERPILLAR, their respective logos,
"Caterpillar Yellow," the "Power Edge" trade dress as
well as corporate and product identity used herein, are
trademarks of Caterpillar and may not be used withoutpermission.
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GENERATIONS AHEAD 2
Overview
Selective Catalytic Reduction (SCR) Definition
SCR System Components
Diesel Exhaust Fluid (DEF)
Pump Electronics Tank Unit (PETU) DEF Injector
Mixing Tube
SCR Catalyst
Ammonia Oxidation Catalyst (AMOX) Diesel Exhaust Fluid (DEF)
Difference between Urea and DEF
Importance
Purchasing Options Packaging Options
Storage Considerations
Handling Information
Summary
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GENERATIONS AHEAD 3
What is Selective Catalytic Reduction (SCR)?
Selective Catalytic Reduction (SCR) is the process by which oxides of nitrogen (NOx)
contained in diesel exhaust are reduced to nitrogen (N2) and water (H2O)
Selective Catalytic Reduction
Selective: targets NOx in diesel exhaust
Catalytic: requires a catalyst
Reduction: NOx is reduced to nitrogen (N2)
Requires Diesel Exhaust Fluid (DEF) a urea based solution
The Cat SCR System functions transparently to the operator
SCR reduces NOx emissions up to 93%
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GENERATIONS AHEAD 4
Why is Selective Catalytic Reduction (SCR) being used with Cat Engines?(130 560 kW)
SCR is an effective and efficient way to further reduce NOx emission levels from Tier 4 Interim/ EU Stage IIIB emission standards to Tier 4 Final / EU Stage IV emission standards
Significant reduction in NOx
achieved with the addit ion of
SCR System
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GENERATIONS AHEAD 5
Brief Selective Catalyt ic Reduction (SCR) History
SCR is already being implemented in a variety of applications
Current Applications
Gas Turbines
Stationary Installations
Electric Power
On-Highway Trucks (European models beginning in 2006, U.S. models beginning in 2010)
European Combined Heat & Power (CHP) Installations
To conform with Tier 4 Final / EU Stage IV emission standards, Cat Engines in the
130-560 kW power range will add a Selective Catalytic Reduction (SCR) System to
the Clean Emissions Module (CEM), a component utilized to meet Tier 4 Interim / EU
Stage IIIB emission standards
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Cat Tier 4 Final / EU Stage IV Aftertreatment Strategy
Tier 4 Final / EU Stage IV = Tier 4 Interim / EU Stage IIIB + SCR System
No chassis
redesign required
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Selective Catalytic Reduction (SCR) System Components
Diesel Exhaust Fluid (DEF)
Pump Electronics Tank Unit (PETU)
DEF Injector
Mixing Tube SCR Catalyst
Ammonia Oxidation Catalyst (AMOX)
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GENERATIONS AHEAD 8
Diesel Exhaust Fluid (DEF)
DEF is a urea based solution
Composition
67.5% de-ionized water
32.5% urea
Urea
Under heat, decomposes to ammonia(NH3) and carbon dioxide (CO2)
Ammonia (NH3) reacts with NOx in the
presence of a catalyst
DEF is required for the SelectiveCatalyt ic Reduction (SCR) System
to function
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GENERATIONS AHEAD 9
Pump Electronics Tank Unit (PETU)
Components
Tank for onboard storage of DEF
Pump to supply DEF to the SCR
System Heated lines to prevent freezing
Coolant Diverter Valve to supply
coolant to the DEF Injector
Separate Electronic Control Module(ECM) controls DEF dosing
By regulation, the DEF tank is
designed with a minimum of a 1:1 fillratio with the fuel tank
No more than 1 tank of DEF is consumed with 1 tank of fuel
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GENERATIONS AHEAD 10
PETU Components
Fill Adapter and Cap
DEF-out to injector
Heated DEF lines
Coolant Diverter
Valve
Tank
Power Relays
DEF Controller
Voltage Line Protection
Module
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GENERATIONS AHEAD 11
PETU (Tank Removed)
DEF Pump Assembly
DEF Pickup
DEF Level Sensor
DEF Temperature
Sensor
DEF Tank Heater
DEF-out to injector
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GENERATIONS AHEAD 12
PETU Pump Assembly
DEF Filter Assembly
(5000 hr service interval)
Pump Assembly
DEF Filter Kit
(5000 hr service interval)
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GENERATIONS AHEAD 13
DEF
Coolant
SupplyCoolant
Return
Electrical
Connector
DEF Injector
DEF is supplied to the SCR System in the Mixing Tube via the DEF Injector(regulated by the Pump Electronics Tank Unit)
An internal coolant supply keeps the injector tip cool
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GENERATIONS AHEAD 14
Mixing Tube
DEF is injected into the exhaust
stream in the Mixing Tube
Heat from the exhaust evaporates the
de-ionized water from the DEF,instantaneously decomposing the
urea, releasing ammonia (NH3) and
carbon dioxide (CO2)
The ammonia (NH3) uniformly mixes
with the NOx contained in the exhaustin the Mixing Tube
Mixing Tube
DEF + Heat Ammonia + Carbon Dioxide
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GENERATIONS AHEAD 15
Selective Catalytic Reduction (SCR) Catalyst
The ammonia (NH3) and NOx mixture
in the exhaust stream enters the SCR
Catalyst from the Mixing Tube
The mixture passes over a Copper
Zeolite Catalyst
The SCR Catalyst causes a chemicalreaction between the ammonia (NH3)
and NOx
The final products are nitrogen (N2)
gas and water vapor (H2O) Up to 93% of NOx emissions
converted
Mixture enters the SCR
Catalyst here
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GENERATIONS AHEAD 16
Ammonia Oxidation Catalyst (AMOX)
To prevent excess ammonia from
being emitted (ammonia slip), the SCR
System uses an AMOX to convert any
unused ammonia from the DEF tonitrogen (N2) and water (H2O)
A small amount of excess DEF is
injected into the SCR System to
ensure NOx conversion; the AMOXoxidizes any excess ammonia (NH3)
from the DEF that did not react with
the NOx
Final component in the Tier 4 Final /
Stage IV Aftertreatment system
Exhaust stream passes
through AMOX
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GENERATIONS AHEAD 17
Selective Catalytic Reduction (SCR) / Diesel Exhaust Fluid (DEF)
Operator Interactions
Function of the SCR System is transparent to the operator
The only action required of the operator is to ensure the DEF tank is refilled
every time the fuel tank is refilled
PETU Filter Assembly / Filter Kit requires replacement every 5000 hours
If the Aftertreatment System is tampered with or the DEF level / quality is
insufficient, the engine will de-rate and eventually shut down if corrective
action is not taken
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GENERATIONS AHEAD 18
Diesel Exhaust Fluid (DEF)
Difference between Urea and DEF
Importance
Purchasing Options
Packaging Options
Storage Considerations
Handling Information
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GENERATIONS AHEAD 19
What is the difference between Urea and Diesel Exhaust Fluid (DEF)?
Urea is a white, nitrogen containing compound that is solid at room
temperature
When heated, releases ammonia (NH3)
Often used as an agricultural fertilizer
Diesel Exhaust Fluid (DEF) is chemical grade urea in solution form which
is liquid at room temperature Composed of 32.5% urea and 67.5% de-ionized water
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GENERATIONS AHEAD 20
Why do I need to use Diesel Exhaust Fluid (DEF)?
Urea contained in DEF decomposes
under elevated temperature into
ammonia (NH3) and carbon dioxide
(CO2) --- See Step 1
Ammonia (NH3) is the reductant which
reduces NOx contained in diesel
exhaust into nitrogen (N2) and water
(H2O) in the presence of the SCRCatalyst --- See Step 2
Without DEF, the SCR System will not
function --- Step 1 & 2 could not occur!
Urea is contained in
Diesel Exhaust Fluid
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GENERATIONS AHEAD 21
Where can I purchase Diesel Exhaust Fluid (DEF)?
DEF can be purchased at a variety of locations:
Cat dealers
Retail locations such as on-highway truck fueling stations and automotive partsstores
Bulk delivery from DEF producers or fuel distributors
Any commercial DEF that meets the ISO 22241 specification is allowed for use in CatSCR equipped engines
For more information regarding availability of DEF, visit:
U.S. Europe
http://www.discoverdef.com http://www.findadblue.com
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GENERATIONS AHEAD 22
Can Agricultural Grade Urea be used instead of Diesel Exhaust Fluid (DEF)?
Urea which is used primarily as a fertilizer in the agriculture industry contains
numerous organic and inorganic contaminants. These contaminants must be tightly
controlled for agricultural grade urea to be used in place of Diesel Exhaust Fluid
(DEF). Because of the high risk of contaminants which could damage the SCRSystem, Caterpillardoes not allow the use of agricultural grade urea in Cat SCR
Systems.
Granular Agricultural Grade Urea
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GENERATIONS AHEAD 23
What quantities of Diesel Exhaust Fluid (DEF) are available for
purchase?
Cat dealer packaging options include:
2.5 gallon bottles for single use
applications
264 gallon tote for multiple useapplications
DEF quantities are available in various
commercial categories including:
Single use: 1 gallon, 3 gallon, and 5
gallon containers
Semi-bulk: 100-250 gallon bins or
plastic totes
Small bulk: 250-500 gallon tanks
264 gallon tote
2.5 gallon bottle
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GENERATIONS AHEAD 24
Storing Diesel Exhaust Fluid (DEF)
Inversely
Related
-DEF has a shelf li fe
-Increases in temperature increases the
rate of degradation
-DEF is corrosive to some metals
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GENERATIONS AHEAD 25
Shelf Li fe
Exposure to
Sunlight
Storage
Temperature
How is Diesel Exhaust Fluid (DEF) Shelf Life affected by temperature?
Diesel Exhaust Fluid (DEF) is
inherently biodegradable
Increased storage temperature
decreases shelf life
Increased exposure to sunlight
decreases shelf life
DEF has a freezing point of 12F
The rate of decay significantly
accelerates when stored in
temperatures above 90F
Optimal temperature for storage is
15F - 77F
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GENERATIONS AHEAD 26
Acceptable Containment Materials
DEF can be stored in the following materials:
304, 304L, 316L series Stainless Steel
400, 409, 439 series Stainless Steel
Highly alloyed austenitic Cr-Ni and Cr-Ni-Mo steels
Titanium
Polyethylene,
Polypropylene
Polyisobutylene
Perfluoroalkoxyl alkane (PFA)
Polyfluroethylene (PFE)
Polyvinylidenefluoride (PVDF)
Polytetrafluroethylene (PTFE) free of additives
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GENERATIONS AHEAD 27
Unacceptable Containment Materials
DEF cannot be stored in the following materials:
Unalloyed steel
Galvanized steel
Aluminum / Aluminum alloys
Magnesium / Aluminum alloys
Copper
Brass Metals and plastics coated with nickel
Nonferrous metals and alloys (copper, copper alloys, zinc, and lead)
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GENERATIONS AHEAD 28
Diesel Exhaust Fluid (DEF) Handling Information
Corrosive to steels and some metals
Spills must be cleaned up immediately
to avoid damage
Avoid contact with skin
Physical Properties
Colorless
Slight pungent ammonia odor
Chemical Properties
Highly reactive with oxidizers such as
bleach
For Safety Information, refer to the
Material Safety Data Sheet (MSDS)
DEF Corrosion on steel
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GENERATIONS AHEAD 29
Diesel Exhaust Fluid (DEF) Disposal
As per the Material Safety Data Sheet (MSDS) for the ChemTool Brand
DEF available at Cat dealers:
The product, if disposed of AS SUPPLIED, is NOT specifically listed as an EPARCRA hazardous waste nor does it have the characteristics of an unlisted RCRA
hazardous waste as defined in 40 CFR 261. Use and/or alterations to the product
such as mixing with other materials may significantly change the characteristics
of the material and alter the RCRA classification and proper disposal method.
Under RCRA it is the responsibility of the user of the product to determine at the
time of disposal, whether the product meets RCRA criteria for a hazardous
waste.
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GENERATIONS AHEAD 30
Key Points
1. Selective Catalyst Reduction (SCR) is transparent to the operator
2. The only action required of the operator is to ensure the DEF tank is refilled
at the same time as the fuel tank
3. DEF is required for the SCR system to function
4. Engine de-rate and eventual shutdown will occur in the event of: insufficientor poor quality DEF supply, as well as tampering with, disabling or removingany of the SCR System Components
5. DEF has a shelf life and should be stored between 15F 77F
6. DEF is corrosive and must be stored in a compatible containment material