Certification of complete system (engine
plus SCR system)
Certification of SCR catalyst and components will
be done in accordance to MEPC 198(62) for a
scaled, standardised SCR reactor and SCR com-
ponents based on product features and following
scaled parameters:
▪ Exhaust gas mass flow
▪ Exhaust gas composition (NO
x
, O
2
, CO
2
, H
2
O,
SO
2
)
▪ Exhaust gas temperature
▪ Catalyst modules (AV, SV or LV value)
▪ Reducing agent
▪ Desired NO
x
conversion rate
The On-board Confirmation Test required for a
scheme B certification will be done for the parent
engine plus SCR system for a group according to
IMO resolution MEPC 198(62).
SCR - Special notes
The selective catalytic reduction SCR uses ammo-
nia (NH
3
) to convert nitrogen oxides in the exhaust
gas to harmless nitrogen and water within a cata-
lyst. However, ammonia is a hazardous substance
which has to be handled carefully to avoid any dan-
gers for crews, passengers and the environment.
Therefore urea as a possible ammonia source is
used. Urea is harmless and, solved in water, it is
easy to transport and to handle. Today, aqueous
urea solutions of 32.5 % or 40 % are the choice for
SCR operation in mobile applications on land and at
sea.
Using urea, the reaction within the exhaust gas pipe
and the catalyst consists of two steps. In the begin-
ning, the urea decomposes in the hot exhaust gas
to ammonia and carbon dioxide using the available
water in the injected solution and the heat of the
exhaust gas:
(NH
2
)
2
CO + H
2
O -> 2NH
3
+ CO
2
[1]
The literal NOx-reduction takes place supported by
the catalyst, where ammonia reduces nitrogen
oxides to nitrogen and water.
4NO + 4NH
3
+ O
2
-> 4N
2
+ 6H
2
O [2]
The MAN Diesel & Turbo SCR system is available in
different sizes to cover the whole medium speed
engine portfolio. The SCR system consists of the
reactor, the mixing unit, the urea supply system, the
pump module, the dosing unit, the control unit and
the soot-blowing system.
After initial start-up of the engine, the SCR system
operates continuously in automatic mode. The
amount of urea injection into the SCR system
depends on the operating conditions of the engine.
Since the control unit of the SCR system is connec-
ted to the engine control system all engine related
informations are continuously and currently availa-
ble. This is one of the important benefits of the MAN
Diesel & Turbo SCR system.
The urea is sprayed into the mixing unit which is
part of the exhaust gas duct. Entering the reactor
the reducing agent starts to react with NO
x
coming
from the combustion. The amount of reducing
agent is controlled by the dosing unit, which is sup-
ported by a pump connected to an urea tank. It fur-
thermore regulates the compressed air flow for the
injector.
Each reactor is equipped with a soot blowing sys-
tem to prevent blocking of the SCR catalyst by
ashes and soot.
▪ Engine in standard configuration according sta-
ted emission level (see above).
▪ Engine attached equipment for control of the
temperature after turbine.
▪ Engine SaCoS software including functions for
control of temperature after turbine and for opti-
mising engine + SCR performance.
▪ IMO Tier III Certificate.
▪ MAN Diesel & Turbo will act as "Applicant"
within the meaning of the IMO.
▪ SCR reactor
▪ Catalyst modules
▪ Soot blowing system
▪ Dosing unit
▪ Mixing unit
▪ Urea injection lance
▪ Control unit SCR
MAN Diesel & Turbo
B1600 0
SCR (Selective Catalytic Reduction)
3700467-8.1
Page 2 (17)
V28/32S, L28/32S, L28/32H, L27/38S, L27/38, L23/30S, L23/30H, L21/31S,
L21/31, L16/24S, L16/24
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