fuel flexibility done right (english)
TRANSCRIPT
Fuel Flexibility Done RightMAN B&W ME-GI-S and MAN B&W ME-LGI-S for stationary applications
Contents
Abstract .......................................................................................................5
Definition of Fuel Gases for Dual Fuel Applications: .......................................5
What is gas in terms of physics? ............................................................5
Natural gas (NG) .....................................................................................5
Liquefied natural gas (LNG) .....................................................................6
Ethane (C2H6) ..........................................................................................6
Liquefied petroleum gas (LPG) ................................................................6
Methanol (CH3OH) ..................................................................................7
Dimethyl ether (DME) ..............................................................................7
Gas engines .................................................................................................7
Development history of MAN B&W ME-GI-S engines for
dual fuel applications ..............................................................................8
Technical description of the gas injection concept (ME-GI-S) ....................... 10
Safety features ...................................................................................... 12
High-pressure, double-wall piping ......................................................... 12
Fuel gas and fuel handling for ME-GI-S ................................................. 13
Description of the Liquid Gas Injection Concept (ME-LGI-S) ........................ 19
Liquid fuel gas and fuel handling for ME-LGI-S ...................................... 20
Liquid fuel gas supply system (LFSS) ..................................................... 20
The low flashpoint fuel valve train (LFFVT) ............................................. 21
Purge return system (PRS) .................................................................... 21
Maintenance Work ..................................................................................... 21
Maintenance of ME-GI-S or ME-LGI-S engines ...................................... 21
Maintenance work at the power plant .................................................... 21
Retrofit ....................................................................................................... 22
Conclusion ................................................................................................. 22
References................................................................................................. 23
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 5
Fuel Flexibility Done RightMAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications
Abstract
This paper deals with the latest devel-
opments of the MAN B&W ME-GI-S
and ME-LGI-S dual fuel two-stroke low
speed diesel engines and associated
fuel gas supply systems.
The discussion about and the require-
ment for lowering CO2, NOx, SOx and
particulate emissions have increased
operators’ and owners’ interest in in-
vestigating future fuel alternatives. The
MAN B&W ME-GI-S and ME-LGI-S
engines offer the opportunity of utilis-
ing such alternatives, also for stationary
application.
The gaseous/liquid fuel flexibility makes
the MAN B&W ME-GI-S and ME-LGI-S
engines an obvious choice for projects
where the engine is connected to inter-
ruptible gas supply systems or where a
switch/mixing ratio among various fuels
is required for various reasons. Fig. 1
shows the engine programme for ME-
GI-S and ME-LGI-S engines.
Definition of Fuel Gases for Dual Fuel Applications:
It is important to understand the basic
definitions of the various fuel types that
can be burned in engines of our de-
sign. MAN B&W two-stroke low speed
diesel engines are designed to provide
optimum fuel flexibility and are an ideal
source of power, whether operating on
fuel gas, liquid fuel gas, liquid fuel or liq-
uid biofuel.
What is gas in terms of physics?
Gas is one of the four fundamental
states of matter (the others being solid,
liquid, and plasma). A gas is a sample
of matter that confines to the shape of
a container in which it is held and ac-
quires a uniform density inside the con-
tainer. If not confined into a container,
gaseous matter, also known as vapour,
will disperse into space. The term gas
is also used in reference to the state,
or conditions, of matter having similar
properties.
The atoms or molecules of matter in
the gaseous state move freely among
each other, and are, in most instances,
packed more loosely than the mole-
cules of the same substance in solid or
liquid state. A sample of gaseous matter
can be compressed. The most typical
examples of gases are oxygen at room
temperature (approximately 20°C), hy-
drogen at room temperature and water
at standard atmospheric pressure, at a
temperature above 100°C.
In the following section, a non-exhaus-
tive list of various gas types are de-
scribed in detail.
Natural gas (NG)
Raw natural gas is defined as gas ob-
tained from a natural underground
reservoir. It generally contains a large
quantity of methane along with heavier
hydrocarbons such as ethane, propane,
isobutene, normal butane, etc. Also, in
the raw state it often contains a consid-
erable amount of non-hydrocarbons,
such as nitrogen, hydrogen sulphide
and carbon dioxide. These properties
Speed r/min50-60 Hz
Engine type
102.9-103.4
102.9-103.4
102.9-109.1
102.9-103.4
107.1-109.1
150
176.5-180
211.8-214.3
Engine power MW
0 10 20 30 40 50 60 70 80 90 100
K98ME-GI-SK98ME-LGI-S
K90ME-GI-SK90ME-LGI-S9
K90ME-GI-SK90ME-LGI-S
K80ME-GI-S9K80ME-LGI-S9
K80ME-GI-SK80ME-LGI-S
K60ME-GI-SK60ME-LGI-S
K50ME-GI-SK50ME-LGI-S
L35ME-GI-SL35ME-LGI-S
Fig. 1: Engine programme, MAN B&W ME-GI-S and LGI-S
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications6
indicate some traces of compounds
like helium, carbonyl sulphide and vari-
ous n~captans. Raw natural gas is also
saturated with water.
Table 1 gives some examples of analy-
ses of various types of raw natural gas.
Natural gas sold for commercial use is
quite different in composition from the
raw gas given in Table 1.
Table 2 lists the typical composition of
natural gas sold directly as an industrial
fuel.
Natural gas sold as industrial fuel is
not specified by its chemical composi-
tion, but rather by the series of specific
properties that must be met, like heat-
ing value, dew point, water, H2S, CO2
and O2 content as well as the Wobbe
index. A typical lower heating value of
natural gas is 46 MJ/kg.
Liquefied natural gas (LNG)
Liquefied natural gas (LNG) is a natural
gas (predominantly methane, CH4) that
has been converted to liquid form for
ease of storage or transport.
The gas is first extracted and trans-
ported to a processing plant where it is
purified by removing any condensates,
such as water, oil, mud and other gas-
es, like for example CO2 and H2S. The
gas is then cooled down in stages un-
til liquefies – it has now become LNG.
LNG is stored in storage tanks and can
be loaded and shipped.
LNG typically contains more than
90% methane. It also contains small
amounts of ethane, propane, butane,
some heavier alkanes and nitrogen.
LNG is principally used when trans-
porting natural gas to markets. When
reaching the final destination it is ex-
panded (re-gassified) and distributed
as natural gas into pipelines to local
distribution companies or independent
power plants.
The heating value of LNG depends on
the source of gas that is used and the
process that is used to liquefy it. A typi-
cal lower heating value of LNG is 49
MJ/kg. In this paper, natural gas and
LNG is designated as fuel gas.
Ethane (C2H6)
At standard temperatures and pres-
sures, ethane is a colourless, odourless
gas. Ethane is isolated on an industrial
scale from natural gas, and as a by-
product of petroleum refining. Its chief
use is as petrochemical feedstock for
ethylene production. A typical lower
heating value of ethane is 47 MJ/kg. In
this paper we will designate ethane gas
as fuel gas.
Liquefied petroleum gas (LPG)
Liquefied petroleum gas, also called
LPG, GPL, LP Gas, liquid petroleum
gas or simply propane or butane, is a
flammable mixture of hydrocarbon gas-
es primarily used as a fuel in heating
appliances and vehicles. When specifi-
cally used as a fuel in vehicles it is often
referred to as autogas.
Varieties of LPG bought and sold in-
clude propane (C3), butane (C4) and
most commonly, mixtures consisting of
Geological era Mesozoic mole % Paleozoic mole %
Nitrogen N2 0.32 0.94
Hydrogen sulphide H2S 4.37 17.89
Carbon dioxide CO2 2.41 3.49
Methane C1 85.34 56.53
Ethane C2 4.50 7.69
Propane C3 1.50 3.38
Isobutane iC4 0.25 0.87
n-Butane nC4 0.48 1.73
Isopentane iC5 0.15 0.71
n-Pentane nC5 0.21 0.76
Hexane C6 0.47+ 1.48
Heptane ++ C7++ - 4.53
Table 1
Table 2
From a field plant mole % From a straddle plant mole %
N2 0.30 0.35
C1 91.63 98.60
C2 5.72 1.05
C3 1.63 -
iC4 0.29 -
nC4 0.31 -
iC5 0.12 -
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 7
both propane and butane. Propylene,
butylenes and other hydrocarbons are
usually also present in small concentra-
tions. A powerful odorant, ethanethiol,
is added so that leaks can easily be
detected.
LPG is prepared by refining petroleum
or »wet« natural gas, and is almost en-
tirely derived from fossil fuel sources,
being manufactured during the refin-
ing of petroleum (crude oil) or extracted
from petroleum or natural gas streams
as they emerge from the ground.
As its boiling point is below room tem-
perature, LPG will evaporate quickly
at normal temperatures and pressures
and is usually supplied in pressurised
steel vessels. Unlike natural gas, LPG
is heavier than air and, therefore, it
will flow along floors and tend to set-
tle in low spots, such as basements. A
typical lower heating value of LPG is 46
MJ/kg.
In this paper we will designate LPG as
liquid fuel gas.
Methanol (CH3OH)
Methanol, also known as methyl alco-
hol, wood alcohol, wood naphtha or
wood spirits, is a chemical with the for-
mula CH3OH (often abbreviated MeOH).
Methanol acquired the name »wood al-
cohol« because it was once produced
chiefly as a byproduct of the destruc-
tive distillation of wood. Modern metha-
nol is produced in a catalytic industrial
process directly from carbon monoxide,
carbon dioxide and hydrogen.
Methanol is the simplest alcohol, and
is a light, volatile, colourless, flamma-
ble liquid with a distinctive odour very
similar to, but slightly sweeter than that
of ethanol (drinking alcohol). It is also
used for producing biodiesel.
Methanol burns in oxygen, including
open air, forming carbon dioxide and
water:
2 CH3OH + 3 O2 → 2 CO2 + 4 H2O
Methanol is one of the most traded
chemical commodities in the world,
with an estimated global demand of
around 27 to 29 million metric tons. In
recent years, the production capac-
ity has expanded considerably with
new plants coming on-stream in South
America, China and the Middle East,
the latter based on access to abundant
supplies of methane gas.
Apart from water, typical impurities
include acetone and ethanol. When
methanol is delivered by ships or tank-
ers used to transport other substances,
contamination by the previous cargo
must be expected. A typical lower heat-
ing value of methanol is 20 MJ/kg.
In this paper we will designate metha-
nol as liquid fuel gas.
Dimethyl ether (DME)
Dimethyl ether (DME), also known as
methoxymethane, is the organic com-
pound with the formula CH3OCH3. The
simplest ether is a colourless gas that
is a useful precursor to other organic
compounds and an aerosol propellant.
The simplicity of this short carbon chain
compound leads by combustion to very
low emission of NOx, and CO, as well
as being sulphur-free resulting in no
SOx emissions. A typical lower heating
value of DME is 29 MJ/kg.
In this paper, we will designate DME as
liquid fuel gas.
For other gases please consult
MAN Diesel & Turbo, Copenhagen.
Gas engines
A gas in this paper and context is a
hydrocarbon, or a mixture of hydrocar-
bons and other gases, like He, N2 or
CO, which at normal ambient pressure
and temperature is in a gaseous state
and has a defined flashpoint tempera-
ture. The physical properties of the gas
mixture determines whether it is suit-
able for either an ME-GI-S or an ME-
LGI-S engine. The selection of gas is
to be determined in the initial phase of
a project.
� If the gas can be compressed to ap-
proximately 300 or 400 bar at 45
+/– 10°C and behave as a single
phase, gas state (i.e. compressible),
it is suitable for ME-GI-S. Gaseous
fuels like natural gas and LNG are
suitable for operation at a high gas
pressure at engine inlet. We will ap-
ply designation fuel gas(es) for these
gas types.
� If the gas (or mixture) can be com-
pressed to approx. 35 bar at 25 to
55°C, and it is in a liquid state (i.e. al-
most incompressible), it is well-suit-
ed for an ME-LGI-S engine. Liquid
gas fuels in the form of LPG, DME
and methanol are suitable for opera-
tion at low gas pressure at engine
inlet. It is important to note that the
required pressure and temperature
of the low pressure fuel system vary
slightly with the fuel selected. We will
use the designation liquid fuel gas.
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications8
Liquid fuels like HFO, diesel, crude bio-
fuel and crude oil are suitable as pilot
oil, see Table 5 and 6 on page 17. It is
important to note that the MAN B&W
two-stroke low speed diesel engines
have accumulated millions of operating
hours on these liquid fuel types.
Development history of
MAN B&W ME-GI-S engines for
dual fuel applications
The MC-S engine family has been on
the market since 1982. The statio nary
installations running on liquid fuels
cover any engine output from 4.5 MW
to over 50 MW per unit, whether heavy
fuel or biofuel.
In 1987, the first testing of the GI prin-
ciples was carried out on one cylinder
of a 6L35MC engine in Japan and Den-
mark. At this opportunity, combustion
of synthetic gases with LCV down to 11
MJ/Nm3 was also tested, ref. Table 3.
In 1992, the GI systems were installed
on a 16V28/32GI stationary medium
speed engine at a combined heat and
power (CHP) plant at Hundested in
Denmark, where it has been in service
for more than 40,000 running hours,
see Fig. 2.
The MC/ME/ME-B engine types are
well-proven products in the marine
market and can be used for stationary
application as well. Our paper: ‘Two-
stroke Low Speed Diesel Engines for
Independent Power Producers and
Captive Power Plants’ describes these
engine types in more detail. The GI so-
lution was developed in parallel and
was first tested in the early 1990s. In
1994, the first MAN B&W two-stroke
low speed GI engine, a 12K80MC-GI-S,
was put into service on a power plant at
Chiba, Tokyo, Japan. So far, the Chiba
engine has operated as a peak load
plant for almost 20,000 hours on high-
pressure gas, see Fig. 3.
At the same time, in 1994, all major
classification societies approved the GI
concept for stationary and marine ap-
plications.Fig. 2: 16V28/32-GI, Hundested, Denmark
Gaseous fuels burned in MAN B&W two-stroke low speed diesel engines
Composition Units Natural gas types VOC fuel types
CH4 vol. % 88.5 91.1 26.1 - - -
C2H6 vol. % 4.6 4.7 2.5 1.1 6.3 -
C3H8 vol. % 5.4 1.7 0.1 65.5 - -
C4H10 vol. % 1.5 1.4 - 23.9 5.0 6.1
C5+ vol. % 6.5 88.7 93.9
CO2 vol % - 0.5 64.0 - - -
N2 vol % - 0.6 7.30 - - -
Molar mass Kg/kmol 18.83 17.98 35.20
Lower calorific value kJ/kg 49,170 48,390 7,050
Lower calorific value kJ/Nm3 41,460 38,930 11,120
Density
At 25°C/ 1 bar abs Kg/m3 0.76 0.73 1.43
Table 3
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 9
Fig. 3: 12K80MC-GI-S Chiba Plant
12K80MC-GI-S
Bore 800 mm
Stroke 2300 mm
Output 40 MW
Fuels (main/pilot):
M Natural gas
P Marine diesel oil
Main data 1994 - 1999
Average reliability 97%
Average availability 97%
Average load factor 71%
Average efficiency gross
46.1%
Average efficiency net 42.6%
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications10
Technical description of the gas in-jection concept (ME-GI-S)
Technically, there is only a small differ-
ence between conventional fuel and
gas-burning engines. The combustion
principle in either case follows the die-
sel cycle principle.
On conventional fuel engines, the inject-
ed fuel ignites because the temperature
of the compressed air in the cylinder is
above the auto-ignition temperature of
the fuel. The auto-ignition temperature
of liquid fuel is approx. 210-230°C.
The auto-ignition temperature of pure
gases, i.e. metane and ethane, is in the
range of approximately 470 to 540°C.
This means that a small amount of pilot
fuel has to be injected into the cylinder
before gas injection because gas does
not auto-ignite at the temperature pre-
vailing in the combustion chamber at
the time of the injection.
The engine output and load response
remain unchanged compared with op-
eration on liquid fuel. It is important to
know that the gross efficiency also re-
mains unchanged.
The gas supply line on the engine prop-
er is designed with ventilated double-
wall piping and HC (hydrocarbon) sen-
sors for safety shutdown.
The GI control and safety systems are
add-on systems to the normal engine
systems. It is a precondition that the
engines are of the electronic control de-
sign, i.e. ME. MAN B&W two-stroke low
speed diesel engines of the ME design
are the preferred solution in the marine
market when placing orders for ships.
Apart from these systems on the en-
gine, the engine and auxiliaries will
comprise some new units. The most
important ones, apart from the gas
supply system, are listed below:
� Ventilation system for venting the
space between the inner and outer
pipe of the double-wall piping
� Sealing oil system delivering sealing
oil to the gas valves separating con-
trol oil and gas
� Inert gas system enabling inert gas
purging of the gas system
� Control and safety system com-
prising a hydrocarbon analyser for
checking the hydrocarbon content of
the air in the double-wall gas pipes.
The control and safety systems are de-
signed to “fail to safe conditions”. All
failures detected during gas fuel run-
ning, including failures of the control
system itself, will result in a gas fuel
stop/shutdown and a change-over to
100% pilot fuel operation. Blow-out
and gas-freeing purging of the high-
pressure gas pipes and of the com-
plete gas supply system will follow. The
change-over to fuel oil mode is always
done without any power loss on the en-
gine.
The gas from the fuel gas supply flows
through the main pipe via chain pipes
to each cylinder’s gas valve block sys-
tem and accumulator. These chain
pipes perform an important task:
� The double-wall chain pipes act as
flexible connections between the stiff
main pipe system and the engine
structure, safeguarding against extra
stresses in the main and chain pipes
caused by the inevitable differences
in thermal expansion of the gas pipe
system and the engine structure.
Hydraulic oil inlet
Cylinder cover
Gas fuel supply
Sealing oil inlet
Gas leakage detection
Connection to theventilated pipe system
Fig. 5: Gas injection valve – ME-GI engine
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 11
The buffer tank, containing about 20
times the injection amount per stroke
at MCR, i.e. 100% load, performs two
important tasks:
� It supplies the gas amount for injec-
tion at a slight, but predetermined,
pressure drop
� It forms an important part of the
safety system.
Since the gas supply piping is of the
common rail design, the gas injection
valve must be controlled by an aux-
iliary control oil system. In principle,
this consists of the ME hydraulic con-
trol oil system and an ELGI (ELectrical
Gas Injection) valve, supplying high-
pressure control oil to the gas injection
valve, thereby controlling the timing and
opening of the gas valve.
As already mentioned, dual fuel opera-
tion requires injection of both pilot fuel
and gas fuel into the combustion cham-
ber. Different types of valves are used
for this purpose. Three valves per cylin-
der are fitted for gas injection and three
for pilot fuel for engines with bore sizes
larger than 60 cm. The media required
for both liquid fuel and fuel gas opera-
tion are as follows:
� Fuel gas supply
� Liquid fuel supply (pilot oil)
� Control oil supply for actuation of gas
injection valves
� Sealing oil supply.
The gas injection valve design is shown
in Fig. 5. This valve complies with tra-
ditional design principles of the com-
pact design. Fuel gas is admitted to the
gas injection valve through bores in the
cylinder cover. To prevent a gas leak-
age between the cylinder cover/gas
injection valve and the valve housing/
spindle guide, sealing rings made of
temperature and gas resistant material
have been installed. Any gas leakage
through the gas sealing rings will be led
through bores in the gas injection valve
to the space between the inner and the
outer shield pipe of the double-wall gas
piping system. Any leakage will be de-
tected by HC sensors.
The gas acts continuously on the valve
spindle at a max. pressure of about
300 bar. To prevent gas from entering
the control oil actuation system via the
clearance around the spindle, the spin-
dle is sealed by sealing oil at a pressure
higher than the gas pressure (25-50 bar
higher).
The pilot oil valve is a standard ME fuel
oil valve without any changes, except
for the nozzle. HFO, MGO, MDO, crude
oil and crude biofuel can be used as pi-
lot oil. The fuel oil pressure is constantly
monitored by the GI safety system in
order to detect any malfunction of the
fuel oil valve.
The fuel oil valve design allows opera-
tion solely on fuel oil up to MCR and
10% overload once for every consecu-
tive 12 hours. The gas engine can be
run on fuel oil at 100% load, switching
from gas to fuel at any time without
stopping the engine.
As can be seen in Fig. 6 (GI injection
system), the ME-GI injection system for
Fig. 6: ME-GI injection system for 50 bore and smaller
Proximity position sensor
300 bar hydraulic oil. Common with exhaust valve actuator
Inje
ctio
n
FIVA valve
Low pressure fuel supply
Fuel return
Fuel injection valve
To Silencer
Valve Closed
PurgeGasAccu
Gas Block
Fuel actuationWindow Valve
Gas injection valves
GasPress
ELWI
ELWI
ELGI
ELGI
Time
Blow off
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications12
50-bore engines and smaller consists
of fuel oil valves, fuel gas valves, ELGI
for opening and closing of the fuel gas
valves, a FIVA (fuel injection valve ac-
tuator) valve to control – via the fuel oil
valve – the fuel oil injection profile and
last, but not least, the ELWI (ELectrical
WIndow and gas shutdown valve) valve
to control the position of the window
valve as an extra safety feature to pre-
vent gas leakages and ensure a dou-
ble valve block towards the combus-
tion chamber. Furthermore, it consists
of the conventional fuel oil pressure
booster, which supplies pilot oil in the
dual fuel operation mode.
The fuel oil pressure booster is equipped
with a pressure sensor to measure the
pilot oil pressure on the high pressure
side. As mentioned earlier, this sensor
monitors the functioning of the fuel oil
valve. If any deviation from a normal in-
jection is found, the GI safety system
will not allow opening for the control oil
via the ELGI valve. In this event no gas
injection will take place.
Safety features
Under normal operation where no mal-
functioning of the fuel oil valve is found,
the fuel gas valve is opened at the cor-
rect crank angle position, and fuel gas
is injected. The fuel gas is supplied
directly into an ongoing combustion.
Consequently, the risk of having un-
burnt gas eventually slipping past the
piston rings and into the scavenge air
receiver is considered to be very low.
Monitoring the scavenge air receiver
pressure and combustion condition
safeguards against such a situation.
In the event of a too high combustion
pressure, the gas mode is stopped and
the engine returns to burning liquid fuel
oil only.
The purpose is to be warned at an early
stage if any gas leaks occur across the
gas injection valves. The window valve
has a double safety function securing
that gas injection into the combustion
chamber is only possible at the correct
injection timing. In the event of a gas
failure, it can also block the gas from
entering the combustion chamber,
thereby ensuring that only a very small
amount of gas will enter.
The pressure sensor is located between
the window valve and the gas injection
valve. The small gas volume in the cyl-
inder cover on each cylinder will reveal
the gas pressure during one cycle. By
this system, any abnormal gas flow will
be detected immediately, whether due
to seized gas injection valves, leaking
gas valves or blocked gas valves. The
gas supply is discontinued and the gas
lines are purged with inert gas. Also in
this event, the engine continues run-
ning only on liquid fuel oil without any
power loss.
High-pressure, double-wall piping
The chain gas pipes are designed with
double walls, with the outer shielding
pipe designed so as to prevent fuel gas
outflow to the machinery spaces in the
event of rupture of the inner gas pipe.
The intervening space, including also
the space around the valves, flanges,
etc., is equipped with separate me-
chanical ventilation with a capacity of
approx. 30 air changes per hour. The
pressure in the intervening space is be-
low that of the engine hall with the (ex-
tractor) fan motors placed outside the
ventilation ducts. The ventilation inlet
air is taken from a non-hazardous area.
Gas pipes are arranged in such a way
that air is sucked into the double-
walled piping system from around the
Fig. 7: Branching of gas piping system
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 13
pipe inlet. Next the air is led to the in-
dividual gas valve control blocks and
then returned back into the chain pipes
and into the atmosphere.
Ventilation air is exhausted to a firesafe
place. The double-wall piping system is
designed so that every part is ventilat-
ed, see Fig. 7 and 8. All joints connect-
ed with sealings to a high-pressure gas
volume are ventilated. Any gas leakage
will therefore be led to the ventilated
part of the double-wall piping system
and detected by the HC sensors.
The gas pipes on the engine proper are
designed for 50% higher pressure than
the normal working pressure, and are
supported so as to avoid mechanical vi-
brations. The pipes are pressure-tested
at 1.5 times the working pressure.
The chain pipe design, see Fig. 7, be-
tween the individual cylinders ensures
adequate flexibility to cope with the
thermal expansion of the engine from
cold to hot condition. The gas pipe sys-
tem is also designed to avoid excessive
gas pressure fluctuations during opera-
tion.
For the purpose of purging the system
after gas use, the gas pipes are con-
nected to an inert gas system with an in-
ert gas pressure of approximately 9 bar.
In the event of a gas failure, the high-
pressure pipe system is depressurised
before automatic purging. During a nor-
mal gas stop, the automatic purging is
to be started after a period of up to 30
minutes. Time is therefore available for a
quick re-start in gas mode.
Fuel gas and fuel handling for ME-
GI-S
The MAN B&W ME-GI-S engine is ca-
pable of running on both 100% liquid
fuel oil and on any ratio of gas and fuel/
pilot oil at a ratio of 97-3%, see Fig. 9.
In case of fuel gases with very low en-
ergy content, a larger amount of pilot oil
might be required.
Fig. 8: Gas valve control block
Hydraulically actuated purge/blow-off valve
Window valve
Gas outlet
Gas areasVentilation air channel
Fig. 9: MAN B&W two-stroke dual fuel low speed diesel, fuel type mode
100% load
Fuel
Fuel100%
Fuel100%
Fuel-oil-only mode
100% load10%3%
�%Total�%Pilot
Fuel
Maximum-gas-amount mode
*Automatic switchover between gas and pilot oil or fuel injection at 10% load
Gas
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications14
Therefore, the power plant is usually to
be equipped with a full size fuel oil sup-
ply system, see Fig. 10, and a fuel gas
supply system, see Fig. 11.
The fuel gas supply station must be
capable of fulfilling the requirements
specified in Fig. 12.
Fig. 10: Fuel oil system
Fig. 11: ME-GI-S engine and gas handling
Full flow filter 50 µm
Automatic de-aerating valve
From centrifuges
Circulating pumps
Dieseloil
servicetank
Ventingtank
F.O. drain tank
Overflow valve
PreheaterSupply pumps
Main engine
Heavy fueloil service
tank
To draintank
To F.W. coolingpump suction
300 bar and 45°C
To engine
ME-GI-S engineOxidiser
Relique-faction* LNG
HPcompressor
CryogenicHP pump
HPvaporiser
HPcompressor
LNG NGRelique-faction*
I II IIIOxidiser
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 15
Fig. 12: Gas supply station, guiding specification
0
50
100
150
200
250
300
350
0% 20% 40% 60% 80% 100%
Gas
supp
ly p
ress
ure
set p
oint
(bar
)
Engine load (% MCR)
Gas supply pressure set point range
Control of gas delivery pressureGeneral Data for Gas Delivery Condition:
Pressure:
Nominal at 100% load 300 bar
Max. value for design 315 bar
Set point tolerance (dynamic) ± 5 bar
Set point tolerance (static) ± 1%
Temperature:
45°C ± 10°C
Quality:
Condensate free, without oil/water droplets or mist, similar to the PNEUROP recommendation 6611 ‘Air Turbines’
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications16
The sizing and power consumption of
the compressor station or the LNG cry-
ogenic pump mainly depend on the gas
pressure at the plant inlet and the lower
calorific value (LCV) of the fuel gas, see
Fig. 13. Table 4 lists the guiding gas
specifications.
As pilot oil, any commercial available
liquid mineral or biofuel can be used,
ref. Tables 5 and 6.
The fuel gas supply system is suggest-
ed to comprise two compressors for a
single engine installation. Each com-
pressor must have 100% capacity for
redundancy.
0
50
100
150
200
250
300
350
400
450
500
1 10 100
Gas pressure at compressor station inlet (bar abs.)
0
1
2
3
4
5
6
7
Pressure at compressor outlet
LCV 30MJ/Nm3 LCV 20MJ/Nm3 LCV 10MJ/Nm3
2 3 4 5 6 8 20 30 40 50 60 80
kW compressor power (per 1000kg CH4 per hour) Compressor power / Generator output (%)
LCV 40MJ/Nm3
Fig. 13: Guiding gas compressor power demand for natural gas and compressed natural gas
Two-stroke guiding gas specification for MAN B&W two-stroke low speed diesel
engines 1)
Designation
Lower heat value
MJ/kg
Minimum 38 if maximum gas fuel is to be obtained, below 38 higher pilot fuel oil amount might be re-quired
Gas methane number No limit
Methane content (% volume) No limit
Hydrogen sulphide (H2S) (% volume) Max. 0.05
Hydrogen (H2) (% volume) No limit
Water and hydrocarbon condensates (% volume) 0
Ammonia (mg/Nm3) Max. 25
Chlorine + flourines (mg/Nm3) Max. 50
Particles or solid content (mg/Nm3) Max. 50
Particles or solid size (μm) Max. 5
Gas inlet temperature (°C) 45
Gas pressure According to MAN Diesel & Turbo specification
Table 4
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 17
1 1) Max. values at plant entry prior to treatment on site2) Pre-heating down to 15 cSt at engine inlet flange is to be ensured3) Lodin, phosphorus and sulphur content according to agreement with
emissioni control maker4) TBO of engine fuel systems to be adjusted according to actual value
and experience
Two-stroke guiding liquid fuel specification for MAN B&W two-stroke low speed
diesel engines 1)
Designation Diesel engines ISO8217:2010(E) rmk700
Density at 15°C kg/m3 1010
Kinematic viscosity at 50°C cSt 700.0
Flash point °C ≥ 60
Carbon residue % (mm) 20
Ash % (mm) 0.150
Water % (mm) 0.50
Sulphur % (mm) 5.0
Vanadium mg/kg 450
Aluminium + Silicon mg/kg 60
API gravity (min) °API *
Sodium mg/kg 100
Calcium ppm (mm) 200
Lead ppm (mm) 10
Free from ULO calsim > 30 and zink > 15 mg/kg – or – calsium > 30 and phosphorus >15 mg/kg
Table 5
Two-stroke guiding biofuel specification for MAN B&W two-stroke low speed diesel
engines 1)
Designation
Density at 15°C kg/m3 1010
Kinematic viscosity at 100°C 2) cSt 55
Flash point º C > 60
Carbon residue % (m/m) 22
Ash % (m/m) 0.15
Water % (m/m) 1.0
Sulphur 3) % (m/m) 5.0
Vanadium ppm (m/m) 600
Aluminium + silicon mg/kg 80
Sodium plus potassium ppm (m/m) 200
Calcium ppm (m/m) 200
Lead ppm (m/m) 10
TAN (total acid number) mg KOH/g 4) < 25
SAN (strong acid number) mg KOH/g 0
Table 6
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications18
For multiple engine plants operating on
NG or CNG, we suggest the installa-
tion of one compressor per engine, all
feeding a common gas supply line, see
Fig. 14.
For operation on LNG, where a fuel
gas pressure of 300 bar is required, the
technology method is to pressurise the
LNG and evaporate while maintaining
the pressure. Technical solutions are
available from a number of suppliers. In
such a case, the power consumption is
estimated to be approximately 0.5% of
the engine power. The requirement for
redundancy is to be decided together
with the end-user. A glycol water sys-
tem is required for heating the LNG in
the vaporiser, see Fig. 15.
p set
Shut off valve V1
ME-GI
ME-GI
Compressor
Compressor
Gas supply
from pipe line
Pressureregulation valve
Control range 150 to 265 bar g
Vent
p set
Control range 150 to 265 bar g
Fig. 14: Multiple engine installation
Fig. 15: High-pressure cryogenic pump
LNG tank
HT2
Waste heat
Water glycol circuit
Pilot fuel Gas
HT1
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 19
Description of the Liquid Gas Injection Concept (ME-LGI-S)
The details of high-pressure gas injec-
tion have been dealt with in the previ-
ous sections of this paper. This chapter
focuses on liquid fuel gases such as
LPG, DME and methanol, which can be
injected into the combustion chamber
in liquid form. Just like the conventional
operation on an ME-GI-S engine, these
gases are combusted according to the
diesel cycle principle described previ-
ously.
In order to be able to combust liquid
fuel gases, MAN Diesel & Turbo has de-
veloped the fuel booster injection valve
(FBIV), see Fig. 16, which is applied on
the ME-LGI-S engine design.
The FBIV integrates our fuel oil booster
design and our slide injection valve de-
sign. Both designs are well-proven in
the marine market for MAN B&W two-
stroke low speed diesel engines for
propulsion purposes. By application of
this design, the total inertia of the fuel
injection system reduces and improves
the response time of the FBIV. Tests in
service on engines for marine applica-
tion have demonstrated an improved
control of the injection profiles.
When operating on LPG or metha-
nol, each of the cylinder covers will
be equipped with FBIVs designed for
each of the selected liquid fuel gases.
An LGI block will be mounted on the
cylinder cover. This block contains a
control valve for either LPG or metha-
nol for fuel injection, a sealing booster
actuation valve, a forced suction valve
and an LGI purge valve. All pipes for hy-
draulic oil and liquid fuel gases are dou-
ble walled. The double-walled pipes for
LPG, methanol or DME are vented with
ventilation air.
The FBIVs are to be cooled, and their
running surfaces must be lubricated.
For this purpose, a combined sealing
and cooling oil system delivering a 50
bar system oil pressure has been inte-
grated on the engine, and the system
both lubricates all running surfaces and
controls that the temperature in the
booster valve is lower than max. 60°C.
The design principle is show in Fig. 16.
The sealing oil pressure is gener-
ated internally in the FBIV in order to
avoid contamination of the hydraulic oil
when operating the valve. The sealing
oil has further advantages as it avoids
LPG, methanol or DME from entering
the umbrella system and further down
into the drain oil system. The cooling
oil and sealing oil system is fully inte-
grated in the engine design, including
equipment for continuous monitoring of
LPG, methanol or DME contamination
in the oil system. If LPG or methanol
is detected in the system, the engine
will switch to fuel oil mode, and the
liquid fuel gas will be purged from the
engine. At the same time, the cooling
oil pump supply side will be switched
to clean system oil, and the oil circuit
will be flushed with clean oil. Then, the
clean oil will be collected together with
the contaminated oil in the cooling oil
tank, and the system will only be able to
continue operation when no liquid fuel
gas is detected in the tank.
To ensure the correct temperature of
the FBIV, the system oil is cooled in a
heat exchanger connected to, for ex-
ample, the low-temperature cooling
system.
When the liquid fuel gas is injected, the
combustion condition is monitored with
PMI sensors located in each of the cyl-
inder covers. Three combustion condi-
tions are monitored: the compression
Fig. 16: Cross section of fuel booster injection valve (FBIV)
Surfaces requiring lubrication/sealing Lubricating/sealing oil booster piston
Cooling oil inlet
Control oilPlungerNozzle
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications20
pressures, the combustion pressures
and the expansion pressures.
The pressurised liquid fuel gas is de-
livered to the engine inlet via double-
walled pipes ventilated with dry air
taken from the starting air system. A
ventilation system fitted at the outlet
sucks in the air. All liquid fuel gas sup-
ply equipment is designed with double
walls, as any leakage into the atmos-
phere will develop into vapour. This is
monitored by HC sensors located close
to the outlet of the double wall piping
system. If the LPG, methanol or DME
vapour content in the ventilation sys-
tem gets too high, the safety system
will shut down operation on LPG or
methanol and return to operate on fuel
oil only. This switch is done smoothly
and without any power loss.
A control and safety system for either
LPG, methanol or DME is integrated on
the engine. The main operating panel
(MOP) is equipped with a user-friendly
interface for liquid fuel gas operation.
Via this panel, the LGI system monitors
and indicates the relevant pressure,
temperatures and the position of the
different valves.
Liquid fuel gas and fuel handling for
ME-LGI-S
This section describes the specific aux-
iliary systems for the ME-LGI-S engine.
In addition to the systems described
here, the normal auxiliary systems for
the electronically controlled ME con-
cept will also be required, and since the
ME-LGI is a dual fuel concept, a stand-
ard supply system for operation on
fuel oil is also needed. Fig. 17 gives an
overview of the external LGI-S system.
In the ME-LGI-S system principle over-
view diagram, the liquid fuel gas service
tank is shown as a ventilated tank.
Liquid fuel gas supply system
(LFSS)
The engine is using temperature-con-
ditioned LPG, methanol or DME at a
predetermined supply pressure and
varying flow depending on the engine
load. The LFSS will have to supply this
fuel to the engine while complying with
the requirements described regarding
temperature, flow, pressure and ramp-
up capabilities. A different system lay-
out could be chosen for this task. In
the following, a circulation solution is
described as an example only.
The LFSS applies the same principle as
an ordinary liquid fuel oil supply system.
LPG, methanol or DME is taken from a
service tank containing liquid fuel gas
Air supply7 bar
Purgingnitrogen
Cooling oilsystem
Purge returnsystem
Supply pressure andtemperature accordingto specification
Fuel valve trainLiquid fuel
gas
Liquid fuel gas service tank
Liquid fuel gas tank
Standard piping
Double-walled piping, ventilated
Double-walled piping
Liquid Fuel Gas Supply System
Vent
Fig. 17: ME-LGI-S system overview.
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 21
and boosted to a pressure close to the
supply pressure. The liquid fuel gas is
then circulated by the circulation pump,
and the pressure is raised to the engine
supply pressure for either LPG, metha-
nol or DME. The delivery pressure must
ensure that the liquid fuel gas stays liq-
uid, and that no cavitation occurs at the
temperatures that the liquid fuel gas is
exposed to until injection into the FBIV.
The flow of liquid fuel oil in the circu-
lation circuit should be higher than the
liquid fuel oil consumption of the engine
at all times. A typical circulation factor
is 2-3 times the liquid fuel oil consump-
tion. To ensure the liquid fuel delivery
temperature, a heater/cooler is placed
in the circulation circuit. It is recom-
mended to connect this through a sec-
ondary cooling circuit to the LT cooling
system.
The low flashpoint fuel valve train
(LFFVT)
The LFFVT connects the LFSS with
the engine through a master fuel valve
(MFV) arranged in a double block and
bleed configuration. For purging pur-
poses, the valve train is also connected
to a nitrogen source.
Typically, the LFFVT will be placed out-
side the engine hall to avoid the need
for double safety barriers. From the
LFFVT, the fuel is fed to the engine in
a double-walled ventilated pipe through
the engine hall.
Purge return system (PRS)
As mentioned, the ME-LGI-S concept
involves LPG, methanol or DME on
the engine proper. Because of the low
flashpoint, there are operation scenari-
os where the liquid fuel gas piping will
have to be emptied and purged with
nitrogen. For the ME-LGI-S, the liquid
fuel gas piping on the engine and in the
engine hall is to be arranged so that it
can be purged and, thereby, return the
gas to the fuel gas service tank. After
the LPG, methanol or DME has been
returned to the service tank, full purg-
ing with nitrogen is to be conducted
through the double-walled piping sys-
tem.
Maintenance WorkMaintenance of ME-GI-S or ME-
LGI-S engines
Proper maintenance planning is essen-
tial to satisfy the requirements of the
power plant operation. Also with the
ME-GI-S and ME-LGI-S engine com-
ponents, operation and maintenance
are straightforward processes for the
skilled and experienced operating
crew, at least if the maintenance jobs
are duly planned, prepared and con-
trolled. In general, superintendents and
operating crew must be well-educated,
skilled and dedicated professionals.
MAN Diesel & Turbo offers education
programmes to chief engineers that
will keep them updated with the latest
information on maintenance and tech-
nology. Requests for education pro-
grammes can be sent to MAN Diesel &
Turbo in Copenhagen.
Maintenance work at the power
plant
When an ME-GI-S engine is stopped,
the high-pressure gas pipes will be
pressure released and purged with ni-
trogen to ensure that the engine is gas
free and available for all kinds of main-
tenance works.
For an ME-LGI-S engine, if liquid
fuel gas operation is expected to be
stopped for a certain period, e.g. dur-
ing minor maintenance work at the
power plant, the procedure for switch-
ing to gas standby mode is to be fol-
lowed. However, the LFSS is switched
off when the procedure has been com-
pleted. Major servicing work involving
lifting equipment over the supply lines
is not recommended in this mode. The
reason is that the liquid fuel gas sup-
ply lines in both the engine hall and
on the engine proper are expected to
contain amounts of LPG or methanol.
In the event of a complete shutdown
of the liquid gas system, e.g. for major
maintenance work at the power plant,
all piping must be emptied of LPG or
methanol in the LFSS and then the ven-
tilation can be turned off.
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications22
Retrofit
For engines of the MC-S design already
operating on HFO/biofuel, it is techni-
cally possible to carry out conversion to
dual fuel operation for either ME-GI-S
or ME-LGI-S. The engine components
shown in Fig. 18 will be affected by a
retrofit, and a suitable fuel gas supply
should be installed. It is important to
note that requests for retrofit solutions
must be sent to MAN Diesel & Turbo on
an ad hoc basis.
Conclusion
The two-stroke MAN B&W ME-GI-S or
ME-LGI-S engines are applicable any-
where where fuel efficient, reliable and
flexible power production is required.
Besides traditional fuels, such as heavy
fuel and natural gas, biofuels, synthetic
biofuels and synthetic biogases from,
e.g., vegetable garbage or pyrolyses
processes can be applied.
Exhaust reciever
ELGI valve
Double wall gas pipes
FIVA
Cylinder cover
Valve block
Fig. 18: Areas affected in retrofit situations
Fuel Flexibility Done Right – MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 23
References
Paper: Service Experience of Mitsui
Gas Injection Diesel Engines, Mitsui-
MAN B&W 12K80MC-Gi-S and Mitsui
8L42MB-G, Cimac Copenhagen 1998
Paper: Service Experience of the
World´s First Large-Bore Gas-Injection
Engine, ISME Tokyo 2000
Paper: ME Engines - The New Genera-
tion of Diesel Engines, P412 Oct 2003
Paper: Guidelines for Fuels and Lubes
Purchasing, 5510-0041-00ppr Feb
2009
Two-stroke Low Speed Diesel Engines
– for Independent Power Producers
and Captive Power Plants, 5510-0067-
00ppr May 2009
Paper: Stationary MAN B&W ME-GI-
S, Engines for Dual Fuel Applications,
5510-0097-00ppr Aug 2010.
Paper: ME-GI Dual Fuel MAN B&W En-
gines, A Technical Operational and Cost
–effective Solution for Ships fuelled by
Gas, 5510-0063-05ppr Oct 2013
Paper: Using Methanol Fuel in the MAN
B&W ME-LGI Series, 5510-0172-00ppr
Aug 2014
MAN Diesel & TurboTeglholmsgade 412450 Copenhagen SV, DenmarkPhone +45 33 85 11 00Fax +45 33 85 10 [email protected]
MAN Diesel & Turbo – a member of the MAN Group
All data provided in this document is non-binding. This data serves informational purposes only and is especially not guaranteed in any way. Depending on the subsequent specific individual projects, the relevant data may be subject to changes and will be assessed and determined individually for each project. This will depend on the particular characteristics of each individual project, especially specific site and operational conditions. Copyright © MAN Diesel & Turbo. 5510-0169-00ppr Sep 2014 Printed in Denmark