WinGD X72DF, Руководство по установке

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Marine Installation Manual 2021-08 7-2
7 Engine Emissions
7.1 Exhaust gas emissions
X72DF
7.1.2 Selective catalytic reduction
Selective Catalytic Reduction (SCR) systems are used on board ships to ensure
that the exhaust gas emissions comply with the Tier III NO
x
regulations stipu -
lated by the IMO.
SCR technology is based on the reduction of nitrogen oxides (NO
x
) by means of
a reducing agent (typically ammonia, generated from urea) at the surface of a cat -
alyst situated in a reactor. If urea is selected as the reducing agent, then it must
comply with the ISO 18611-1:2014 standard. Urea according to this specification
is an aqueous solution with 40% urea by mass fraction and it has a density in the
range of 1.1 kg/l at 20 °C. The urea consumption figures are provided by the
GTD application. The urea tank sizing must be in accordance with the intended
operating profile.
The drawings relevant for the SCR system (DG 9726) are provided on the
WinGD webpage under the following link:
MIDS
Low-pressure SCR
The SCR reactor is located on the low-pressure side, after the turbine.
For low-pressure SCR applications, WinGD has developed a 2-stroke engine in
-
terface specification that complies with the known low-pressure SCR system pro -
viders. Low-pressure SCR is typically larger in volume than high-pressure SCR,
but more flexible in installation position, as any after-turbocharger position is ac
-
ceptable.
Figure 7 - 2 Low-pressure SCR — Arrangement
NOTE An SCR system can only be used when operating in diesel mode and
not in Fuel Sharing Mode (FSM). For clarification of the fuel operating
modes, please see section 1.3 Fuel operating modes,

1 - 6 .
SM-0253
Exhaust receiver
Scavenge air receiver
SCR
1
13
8
9
6
10
12
11
5
4
3
7
2
1 Exhaust receiver
2 Turbocharger
3 SAC
4 Scavenge air receiver
5 Auxiliary blower
6 SCR
7 Burner 8 Decomposition unit
9 Urea dosing unit
10 Reactor inlet valve
11 Reactor outlet valve
12 SCR bypass valve
13 Turbine bypass valve