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MAN B&W 7.06
Water In Fuel Emulsification
The emulsification of water into the fuel oil reduces
the NO x em<strong>is</strong>sion with about % per % water
added to the fuel up to about 20% without modification
of the engine fuel injection equipment.
A Water In Fuel emulsion (WIF) mixed for th<strong>is</strong> purpose
and based on Heavy Fuel Oil (HFO) <strong>is</strong> stable
for a long time, whereas a WIF based on Marine
Diesel Oil <strong>is</strong> only stable for a short period of time
unless an emulsifying agent <strong>is</strong> applied.
As both the MAN B&W two�stroke main engine
and the MAN Diesel GenSets are designed to run
on emulsified HFO, it can be used for a common
system.
It <strong>is</strong> supposed below, that both the main engine
and GenSets are running on the same fuel, either
HFO or a homogen<strong>is</strong>ed HFO-based WIF.
Special arrangements are <strong>available</strong> on request for
a more soph<strong>is</strong>ticated system in which the GenSets
can run with or without a homogen<strong>is</strong>ed HFObased
WIF, if the main engine <strong>is</strong> running on that.
Please note that the fuel pump injection capacity
shall be confirmed for the main engine as well as
the GenSets for the selected percentage of water
in the WIF.
Temperature and pressure
When water <strong>is</strong> added by emulsification, the fuel
v<strong>is</strong>cosity increases. In order to keep the injection
v<strong>is</strong>cosity at 0- 5 cSt and still be able to operate
on up to 700 cSt fuel oil, the heating temperature
has to be increased to about 70 °C depending on
the water content.
The higher temperature calls for a higher pressure
to prevent cavitation and steam formation in the
system. The inlet pressure <strong>is</strong> thus set to 3 bar.
In order to avoid temperature chock when mixing
water into the fuel in the homogen<strong>is</strong>er, the water
inlet temperature <strong>is</strong> to be set to 70�90 °C.
Safety system
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In case the pressure in the fuel oil line drops, the
water homogen<strong>is</strong>ed into the Water In Fuel emulsion
will evaporate, damaging the emulsion and
creating supply problems. <strong>Th<strong>is</strong></strong> situation <strong>is</strong> avoided
by installing a third, air driven supply pump,
which keeps the pressure as long as air <strong>is</strong> left in
the tank ‘S’, see Fig. 7.06.0 .
Before the tank ‘S’ <strong>is</strong> empty, an alarm <strong>is</strong> given and
the drain valve <strong>is</strong> opened, which will drain off the
WIF and replace it with HFO or diesel oil from the
service tank.
The drain system <strong>is</strong> kept at atmospheric pressure,
so the water will evaporate when the hot emulsion
enters the safety tank. The safety tank shall be
designed accordingly.
Impact on the auxiliary systems
Please note that if the engine operates on Water
In Fuel emulsion (WIF), in order to reduce the NO x
em<strong>is</strong>sion, the exhaust gas temperature will decrease
due to the reduced air / exhaust gas ratio
and the increased specific heat of the exhaust gas.
Depending on the water content, th<strong>is</strong> will have an
impact on the calculation and design of the following
items:
• Freshwater generators
• Energy for production of freshwater
• Jacket water system
• Waste heat recovery system
• Exhaust gas boiler
• Storage tank for freshwater
For further information about emulsification of water
into the fuel and use of Water In Fuel emulsion
(WIF), please refer to our publication titled:
Exhaust Gas Em<strong>is</strong>sion Control Today and
Tomorrow
The publication <strong>is</strong> <strong>available</strong> at: www.mandiesel.com
under ‘Quicklinks’ → ‘Technical Papers
MAN B&W MC/MC-C, ME/ME-C/ME-GI/ME-B engines 198 38 82�8.3
MAN Diesel