EMISSIONS AND TIER 4 EMISSIONS & IT4


After-Treatment Systems


The good news for nonroad engine manufacturers is this: Car and light duty truck manufacturers complied with EPA regulations years earlier and developed technologies that have been tested in nonroad engines. These after-treatment systems take the diesel engine exhaust that has already been created by the engine and clean it further by using one or a combination of the following:


• Catalytic oxidation • Heat • Filtering • Diesel exhaust fl uid (DEF)


These after-treatment devices use fi ltering, heat, and catalytic oxidation to lower emissions in diesel engine exhaust. They’re commonly combined with one another in a single canister. Together they lower many emissions but, most importantly, they reduce particulate matter.


DOC/DPF Systems


The diesel oxidation catalysts (DOC) Engine exhaust is transformed by the DOC to reduce particulate matter. The DOC is a special catalyst that reacts with engine exhaust upon contact. The reaction transforms particulate matter emissions in the exhaust into harmless substances such as water and carbon dioxide. See Figure 1.


The DPF (diesel particulate fi lter) Engine exhaust is fi ltered by the DPF to reduce particulate matter. The DPF is a special “ceramic wall fl ow” fi ltration system that further separates particulate matter from the engine exhaust. See Figure 2.


DPF regeneration To keep the DPF clean and working effi ciently, the high temperature of the exhaust itself is used to burn accumulated particulate matter off of the DPF. This DPF cleaning process is called “regeneration.” See Figure 3.


Selective catalyst reduction (SCR) Engine exhaust is transformed by SCR to


reduce nitrogen oxides (NOx). SCR uses an ammonia and water-based liquid called diesel exhaust fl uid (DEF). Combining exhaust with DEF causes it to react with a SCR catalyst. This reaction turns harmful


NOx into harmless nitrogen and water vapor. See Figure 4.


Visit www.MyWorkSaver.com/Tier 4 for additional information on emissions and iT4 requirements.


EXHAUST


Diesel Exhaust Fluid (DEF)


DEF & NOx react with the catalyst forming non-harmful nitrogen and water vapors


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DIESEL OXIDATION CATALYSTS AND DIESEL PARTICULATE FILTERS


DOC/DPF — Diesel Oxidation Catalyst/Diesel Particulate Filters DOC/DPF — Diesel Oxidation Catalyst/Diesel Particulate Filters Fig. 1


Diesel exhaust from engine combustion flows out of engine


Cleaner diesel exhaust with lower particulate matter concentration comes OUT


EXHAUST


Containing Diesel Particulate Matter


Heavier particulate matter concentration goes IN


Fig. 2


Heavier particulate matter concentration goes IN


Barriers exist to ensure exhaust passes through fi lter walls.


Wall fl ow fi lter (pictured right) Dirty exhaust (brown arrows) passes through fi lter walls. Particulate matter is left behind and cleaner exhaust (blue arrows) exits.


Particulate matter is captured in the Diesel Particulate Filter (pictured above).


DPF Regeneration Fig. 3


To keep the DPF clean and working effi ciently, the high temperature of the exhaust itself is used to burn accumulated PM off of the DPF. This DPF cleaning process is called “regeneration.”


SCR — Selective Catalyst Reduction System SCR — Selective Catalyst Reduction System Fig. 4


Diesel exhaust from engine combustion flows out of engine


Cleaner diesel exhaust with lower NOx


comes OUT


Diesel exhaust lower particulate matter concentration OUT


Diesel exhaust heavier particulate matter concentration IN


Lower particulate matter concentration comes OUT


DEF mixes with exhaust and flows into catalyst


DPF DOC


DOC


DPF


DEF T


ank


SRCTLS


C AAYT


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