Exhaust Aftertreatment System Components And; Selective Catalytic Reduction (Scr) - Mack Granite GU Series Operator's Handbook Manual

Mack, EPA2010 Emissions Solution 245
Exhaust Aftertreatment System Components
and

Selective Catalytic Reduction (SCR)

Selective Catalytic Reduction (SCR) is an
emissions-reduction technology with the
ability to deliver near-zero emissions of
nitrogen oxides (NOx), a smog-causing
pollutant and greenhouse gas. SCR's
performance has been proved in millions
of miles of real-world trucks in other
countries, as well as in long-term field
tests in the U.S.
SCR reduces NOx emissions to very low
levels, while at the same time delivering
excellent fuel economy and reliability.
The system doesn't change the design
or of the basic engine. Rather, SCR is
an aftertreatment system which converts
NOx in the exhaust stream into harmless
gases. Modern diesels already use exhaust
System Operation
1 Diesel engine optimized for high
performance, low particle emissions
and low fuel consumption.
2 Aftertreatment DEF tank
3 The Aftertreatment Control Module
(ACM) continuously monitors and
adjusts the DEF injection rate.
4 DEF is injected into the exhaust gases
in between the Aftertreatment DPF (5)
and the SCR catalyst (6).
aftertreatment systems, called diesel
particulate filters, to control emissions of
another pollutant, soot (also known as
particulate matter or PM).
SCR works by injecting Diesel Exhaust
Fluid (DEF) into the exhaust. DEF is a
solution of ultra-pure water and urea. DEF
works with the heat of the exhaust and a
catalyst to convert NOx into nitrogen and
water vapor - two harmless and natural
components of the air we breathe. The
end result is cleaner air, excellent fuel
efficiency and a reliable emissions control
system for today's modern diesel engine.
5 Aftertreatment Diesel Particulate Filter
(DPF).
6 In the SCR catalyst, nitrogen oxides
are transformed into harmless nitrogen
gas and water.
7 The system notifies the driver when it
is time to refill tank with DEF.
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