fuel flexibility done right (english)

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


K80ME-GI-S9K80ME-LGI-S9




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 -


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.


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


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%


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


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


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


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


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


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’


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


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


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


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


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.


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.


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


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

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