Man B&W L35MC6-TII, Project Manual

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MAN B&W 2.12
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MAN Diesel
MAN B&W MC/MCC engines 198 66 366.1
Emission Control
IMO NO
x
Emission Limits
All MC and MC-C engines are, as standard, deliv-
ered in compliance with the IMO speed depend-
ent NOx limit, measured according to ISO 8178
Test Cycles E2/E3 for Heavy Duty Diesel Engines.
NO
x
Reduction Methods
The NOx content in the exhaust gas can be re-
duced with primary and/or secondary reduction
methods.
The primary methods affect the combustion pro-
cess directly by reducing the maximum combus-
tion temperature, whereas the secondary me-
thods are means of reducing the emission level
without changing the engine performance, using
external equipment.
030% NO
x
Reduction
The MC and MC-C engines are as standard de-
livered to comply with IMO NOx emission limita-
tions, EoD: 4 06 060 Economy mode. Engine test
cycles E2 and E3 has to be ordered as an option:
4 06 060a and 060b, and various conditions can
be specified, options: 4 06 060f, 060g and 060h.
Compliance with other emission limits can be
specified as an option: 4 06 065.
Regardless of the emission limit specified, the en-
gines are matched for best economy in service.
For further information on engine operation op-
tions, see Extent of Delivery.
3050% NO
x
Reduction
Water emulsification of the heavy fuel oil is a well
proven primary method. The type of homogeni-
zer is either ultrasonic or mechanical, using water
from the freshwater generator and the water mist
catcher.
The pressure of the homogenised fuel has to be
increased to prevent the formation of steam and
cavitation. It may be necessary to modify some of
the engine components such as the fuel oil pres-
sure booster, fuel injection valves and the engine
control system.
Up to 9598% NO
x
Reduction
When operating at full load, this reduction can be
achieved by means of secondary methods, such
as the SCR (Selective Catalytic Reduction), which
involves an aftertreatment of the exhaust gas, see
Section 3.02. At lower load a 80-90% NO
x
reduc-
tion can be obtained, measured according to the
ISO 8178 E2/E3 Test Cycles.
Plants designed according to this method have
been in service since 1990 on five vessels, using
Haldor Topsøe catalysts and ammonia as the re-
ducing agent, urea can also be used.
The SCR unit can be located separately in the
engine room or horizontally on top of the engine.
The compact SCR reactor is mounted before
the turbocharger(s) in order to have the optimum
working temperature for the catalyst. However at-
tention have to be given to the type of HFO to be
used.
For further information about emission control,
please refer to our publication:
Exhaust Gas Emission Control Today and Tomor-
row
The publication is available at: www.mandiesel.com
under ‘Quicklinks’
→
‘Technical Papers’.