Tier III Compliance Low Speed Engines

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Tier III ComplianceLow Speed Engines



Contents

Introduction .................................................................................................3

NOx Compliance with EGR ...........................................................................3

Investigation of EGR NOx Reduction Potential ..........................................3

EGR Principle .........................................................................................4

EGR Experimental Test ........................................................................... 4

EGR Test Results ....................................................................................4

Parameter Variation Tests ........................................................................5

Heat Release With EGR ..........................................................................6

Combined EGR and WIF Test ..................................................................6

Cylinder Condition Running with EGR ......................................................8

EGR Service Test on Cont. Vessel ...........................................................8

Service Test Objective .............................................................................9

Design of a Retrofit EGR System .............................................................9

Fully Automated EGR System ............................................................... 11

Installation of EGR ................................................................................ 12

EGR in Service......................................................................................13

Results of EGR in Service ..................................................................... 13

EGR in the Future ................................................................................. 14

NOx Compliance with SCR .........................................................................15

SCR Technology ...................................................................................15

Objective ..............................................................................................15Content of the Development Work.........................................................16

Outcome of the Project .........................................................................17

Test Faci lities and Time Schedule ...... ...... ...... ...... ...... ...... ....... ...... ...... ... 18

Fulfilling IMO Sulphur Requirements in Fuel and/or SO2 in Exhaust Gas .. 18

SOx Compliance with Wet Scrubber ...........................................................19

Wet Scrubber Implementation on MAN B&W Engines ............................19

Full Scale Installation on DFDS Vessel Tor Ficaria ...................................20

Sea Water Scrubbing ............................................................................21

Fresh Water Scrubbing .........................................................................21

Results of Scrubber in Service ..............................................................22

Low Sulphur Fuel Operation .......................................................................23

Engine Challenges and Recommended Solutions ..................................23

Distillate Tests .......................................................................................24

Further Tests.........................................................................................25

Conclusion .................................................................................................26



MAN B&W Diesel

3 Tier III Compliance – Low Speed Engines

Tier III Compliance – Low Speed Engines

Introduction

Even though IMO Tier II regulations

have not yet come into force (keel laying

after 1 January 2011), clear develop-

ment and research targets for fulfilling

IMO Tier III (valid from 1 January 2016 in

ECA areas) must already now be fixed

and initiated.

A flexible and agile two-way strategy

on NOx emission reduction has been

chosen for our MAN B&W two-stroke

engines. MAN B&W two-stroke engines

will in due time, before 2016, have full

design specifications for engines oper-

ating with EGR (Exhaust Gas Recircula-

tion) and with SCR (Selective Catalyst

Reduction) available for a complete en-

gine programme.

This paper describes MAN Diesel & Tur-bo’s progress in the development of the

EGR system and shows performance

and emission results from both testbed

testing of EGR systems, details on ret-

rofitting of EGR system on a 7S50MC

engine on the container vessel Alexan-

der Maersk and the first service results

from the service testing. The paper also

outlines results from EGR/WIF (Water In

Fuel) combination tests and underlines

the advantages of utilising the flexibility

of electronically controlled engines and

turbochargers in combination with EGR

and WIF systems. Also the potential for

utilising both EGR and/or WIF for ob-

taining Tier II compliance with improved

engine efficiency is explained.

Furthermore, this paper describes our

efforts in connection with making a de-

tailed specification of SCR applicationon the high pressure side of the turbo-

chargers for two-stroke engines.

As for NOx emission, MAN Diesel &

Turbo has chosen a flexible and agile

two-way approach for MAN B&W two-

stroke engines with regard to fulfilling

future SOx emission legisation. This pa-

per outlines the efforts for improving the

capability of our engines for low sulphur

fuel operation and describes the results

from both testbed and service testing

of wet scrubbers for SOx

and PM (Par-

ticulate Matter) reduction. The descrip-

tion includes comments to water treat-

ment methods for both closed loop (FW

(Fresh Water)) and open loop operation

(SW (Sea Water)), energy consumption

of scrubber system and consumption

of neutralising agents.

NOx Compliance with EGR

Investigation of EGR NOx Reduction

Potential The potential of using Exhaust Gas Re-

circulation (EGR) for NOx reduction on

HFO burning large two-stroke marine

diesel engines has been investigated

by MAN Diesel & Turbo for the last 10

years.

The EGR system on MAN B&W’s

4T50ME-X two-stroke diesel test en-

gine in Copenhagen is based on recir-

culation of exhaust gas on the engine

side of the turbocharger, see Fig. 1.

Part of the exhaust gas is bypassed

from the exhaust gas receiver to the

scavenge air system, downstream of

the turbocharger compressor side, and

thus recirculated. An electrical, high

pressure blower forces the exhaust

gas (3.3 bar) through a wet scrubber

(wet gas cleaner) to the higher pres-

surised scavenge air receiver (3.7 bar).

The scrubber cleans the exhaust gas

by removing SOx and PM (Particulate

Matters) and cools the gas by humidi-

fication before reintroduction to the

combustion chamber. The charge air

coolers cool the mixture of recirculated

exhaust gas and scavenge air down tothe scavenge air temperature set point.

Fig. 1 shows a principal sketch of

the tested EGR application on the

4T50ME-X. The system comprises a

single step, high pressure blower, an

exhaust gas wet scrubber, a control

Water

pump

Turbocharger

Scrubber

Clean

Brine out

Scavenge

Air cooler

Water

Treatment

System

Sludge

outEGR

Blower

EGR

Valve

Fig. 1: EGR principal layout of 4T50ME-X




valve, a water treatment system and a

PLC-based control unit for controlling

the water treatment system. A NaOH

dosing system neutralises the scrubber

water keeping the sulphur removal in

the scrubber at a certain level accord-

ing to the decided sulphur removal ef-

ficiency.

EGR Principle

The basic concept of the technology is

that the higher heat capacity and the

lower oxygen content of the recircu-

lated exhaust gas lower the peak com-

bustion temperature in the combustion

chamber significantly, which suppress-

es the formation of thermal NOx.

EGR Experimental Test

In May 2009, the EGR was tested to

full extent on the MAN B&W 4T50ME- X 7MW test engine in Copenhagen

in the so-called Extreme EGR test

programme. In the Extreme test pro-

gramme, a combination of an EGR and

WIF (Water In Fuel) emulsion test was

included in order to disclose the syn-

ergy effects between these two NOx

reducing measures.

Around 50 different tests running with

EGR alone and with a combination of

EGR and WIF were carried out on the

4T50ME-X test engine, using either

MDO or HFO for targeting the following

objectives:

Investigate the “maximum” NOx re-

duction with EGR

Determine the performance condi-

tions when Tier II and III NOx cycle

values are obtained by using EGR Parameter variation for investigation

of optimal SFOC and CO emission

values when using EGR

Investigate low load performance

with EGR.

The main focus point has been to find

the necessary EGR rates for fulfilling the

Tier III emission legislat ion and at the

same time securing minimum effect on

the combustion efficiency, and thereby

the minimum SFOC penalty. Further-

more, the test also concentrated on se-

curing minimum penalty on other emis-

sion parameters as CO (highly related

to SFOC), HC and particulate matter.

The EGR tests were also performed at

NOx Tier II level in order to investigate

the potential in SFOC benefits com-

pared to a non-EGR Tier II engine.

EGR Test Results

The achieved NOx cycle value with EGR

confirmed that the IMO Tier III level (3.4

g/kWh) was obtainable with EGR as the

only remedy to reduce NOx, even with

the engine in a normal Tier I configura-

tion as reference.

The tests also confirmed that signifi-

cantly improved SFOC can be obtained

at the Tier II emission level with an en-

gine using EGR, rather than with an en-

gine using normal Tier II tuning meas-

ures, especially at part load.

Fig. 3 summarises the results from the

EGR test, with the EGR rate given by

the oxygen content in the scavenge

air and, as it can be seen, Tier III level

emissions of 3.4 g/kWh as cycle value

and 5.1 g/kWh at NTE (Not To Exceed)

limit at all load points are obtained at

scavenge air oxygen contents of 15.5to 18%.

Fig. 2: EGR system on 4T50ME-X



MAN B&W Diesel


Parameter Variation Tests

The main results from the parameter

variation test can be seen in Table 1. The variation was performed with con-

stant wet O2 concentration in the scav-

enge air, except for the max. EGR test

(visual smoke limit) and for the Tier III

setup case were the chosen O2 con-

16.8% oxygen in scavenge air), with

only a minimum influence on the NOx

emission. Combining these measuresand increasing the EGR rate secures

compliance with the NOx Tier III level

with a minimum penalty on the SFOC

and CO emission.

0

4

8

12

16

20

24

14 15 16 17 18 19 20 21 22

S p e c i fi c N O

x ( g

/ k W h )

Oxygen conc. in Scav.Rec (wet, vol %)

100% load

75% load

50% load

25% load

NTE NOx

IMO Tier III cycle value

Fig. 3: NO x emission as a function of oxygen content in the scavenge air

Test results from parameter variation test at 75% load

NOx

[g/kWh]

dSFOC

[g/kWh]

CO

[g/kWh]

Pmax

[barabs]

EGR rate

[%]

O2 Scav.air

[vol. %]

No EGR 17.8 0 0.65 152 0 -

Max. EGR 2.3 +4.9 4.17 151 39 16.0

EGR ref 3.7 +3.0 2.57 151 36 16.8

Incr. pcomp /pscav 4.0 +2.5 2.18 156 36 16.8

Incr. Phyd 4.2 +2.8 1.83 151 37 16.6

Incr. pscav 3.6 +1.9 2.12 156 37 16.6

Incr. Tscav 3.9 +3,6 2.82 156 34 16.8

Tier III setup 3.4 +0.6 1.34 157 41 16.2

Table 1

centration was targeting the Tier III NOx

level.

As Table 1 clearly indicates, increased

pcomp/pscav, increased pscav and in-

creased injection pressure (Incr. Phyd)

have a positive influence on the SFOC

at a relatively high EGR rate (16.6-




Heat Release With EGR

Applying EGR generally means a reduc-

tion in the maximum combustion rate

due to local lack of oxygen. At the same

time, the burn duration is generally in-

creased, see Fig. 4, giving a typical ex-

ample from the literature on the EGR

influence on a high speed diesel en-

gine (heavy truck engine). The reduced

maximum combustion rate and the in-

creased burning time result in increased

SFOC, increased formation of particu-

late matter and high CO formation.

Combined EGR and WIF Test

The test results at 75% load from com-

bined WIF and EGR tests are summa-

rised in Table 2. The water content in

the fuel is shown as added water to the

fuel volume. As can be seen from the

figures using WIF in combination with

EGR is a very effective way of reducing

CO emissions in agreement with small

engine results. At the highest applied

water content using EGR (WIF 50% and

EGR 37%), the CO emission is reduced

by a factor of almost 5 compared to

0.00

-5 0 5 10 15 20 25 30 35 40 45 50 55 50 65 70

0.01

0.02 H H R ( 1 / d

e g )

0.03

0.04

0.05

0.061600 bar, SOI = 3, no EGR

1600 bar, SOI = EGR = 20%

0.00

-5 0 5 10 15 20 25 30 35 40 45 50 55 50 65 70

0.10

0.20

( - )

Crank angle

0.300.40

0.50

0.60

0.70

0.80

0.96

1.00

Fig. 4: Influence of EGR on heat release and cumulative heat release of a Heavy

Duty DI-Diesel Engine equipped with a Common Rail Injection System running

at 1,460 rpm, MEP=18.7 bar (100% load) taken from SAE 2001-01-3497

0.00

0 5 10 15 20 25 30 35 40 45 50 55 50 65 70

0.01

0.02 H H R ( 1 / d

e g )

0.03

0.04

0.05

0.06

0.07 Phyd = 200 bar, EGR = 0%

Phyd = 200 bar, EGR = 29%

0 5 10 15 20 25 30 35 40 45 50

( - )

Crank angle

0.10

0.20

0.300.40

0.50

0.60

0.70

0.80

0.96

1.00

Fig. 5: Heat release and cumultative heat release on 4T50ME-X with

(29%) and without EGR

On the slow running 4T50ME-X engine,

the same measurements were made as

given above for the typical high speed

engine, and the result is shown in Fig.

5. The influence of 29% EGR is nearly

not noticeable, the negative effect on

SFOC, CO and PM is accordingly also

much less (nearly zero) than for the high

speed four-stroke engine.

The slight negative effect on heat relase

is fully compensated by increasing in-

jection pressures as shown in Fig. 6.



MAN B&W Diesel


the tests using only EGR and the CO

emission is even lower than the refer-

ence case (0% WIF 0% EGR). Even with

more moderate amounts of water (WIF

28% and EGR 37%), the CO emissionis equal to that of the reference case.

Thus, indeed it is possible to combine

WIF and EGR in order to reduce their

individual drawbacks. The drawback of

WIF on SFOC is, however, significant

and a further optimisation of the injec-

tion system for the WIF systems must

be performed in order to obtain accept-

able SFOC penalties.

Fig. 6: Heat release rate and cumulative heat release at 75% load with and without EGR

0.000 5 10 15 20 25 30 35 40 45 50 55 50 65 70

0.01

0.02 H H R ( 1 / d e g )

Crank angle

0.03

0.04

0.05

0.06

0.07Phyd = 200 bar, EGR = 0%



0 5 10 15 20 25 30 35 40 45 50

( - )

Crank angle

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.96

1.00

Test results, EGR and WIF combinations at 75% engine load

Ref. EGR

Tier III

EGR

Tier II

50% WIF

(added)

50% WIF

(added) + EGR

28% WIF

(added)

28% WIF

(added) + EGR

EGR rate % 0 37 18 0 37 0 37

WIF % 0 0 0 50 50 28 28

NOx g/kWh 17.4 3.4 12.3 10.4 1.3 13.5 2.0

CO g/kWh 0.7 1.4 0.4 0.24 0.30 0.25 0.67SFOC % 0 0.3 -2.6 2.4 3.9 0.4 2.5

Table 2

In general, the EGR testing confirms

that CO emissions increase and un-

burnt hydrocarbon emissions decrease

with increasing EGR ratios. For WIF, the

opposite is experienced, i.e. increasedemissions of hydrocarbons, but signifi-

cantly reduced CO emissions.

While EGR has the potential to reduce

the NOx emissions below the Tier III

limit, it seems to be out of reach for

WIF alone, since too high water con-

tents are required and simply because

the SFOC penalty will become too high.

By combining the two methods, ex-

tremely low NOx emissions (down to

0.2 g/kWh) have been realised while the

emissions of CO and unburned hydro-

carbons remained at the low levels usu-ally observed from large two-stroke die-

sel engines. The NOx reduction achieved

during these tests is well above 90%, in

some cases above 98%, and accord-

ingly a competitor to the SCR system

with regard to making the “zero emis-

sion” two-stroke diesel engine.




Cylinder Condition Running with EGR

Running with EGR on two-stroke die-

sel engines burning HFO, changes the

chemical composition of the scavenge

air entering the combustion chamber.

The O2 content is decreased, the CO2

and CO (running without WIF) content

is increased, the SOx (SO2 and SO3 )

content is increased, to some extent

depending on the scrubbing efficiency,

the HC amount is increased, the PM

mass is increased and the H2O con-

tent is increased. Of all these species

the SOx (in the form of sulphuric acid)

and the H2O are considered potential to

have the most important impact on the

cylinder condition if present in the form

of free droplets.

The presence of water droplets enter-

ing the combustion chamber must bereduced to a minimum by securing opti-

mal efficiency of the water mist catcher

system, and the presence of SOx must

be controlled by addition of NaOH to

the scrubber water.

The cyl inder condition was investigated

before and after completion of more

than 100 hours of extreme EGR test-

ing, and the conclusion was that there

were no negative effects to see when

inspecting the liner, piston and piston

rings, see Fig. 7.

EGR Service Test on Cont. Vessel

From August 2008 until March 2010,

MAN Diesel & Turbo has developed and

manufactured the very first Exhaust Gas

Recirculation (EGR) system for a two-

stroke diesel engine and installed it on

a container vessel in service.

In partnership with A. P. Moller-Maersk,

the EGR prototype system has been

Fig. 7: Cylinder condition before and after >100 hours’ testing

Fig. 8: A. P. Moller-Maersk container vessel Alexander Maersk

installed on the vessel Alexander Mae-

rsk. The vessel was built in 1998, and

is a 1,092 TEU container vessel cur-rently sailing between Southern Europe

and Northern Africa. The main engine

is a Hitachi B&W 7S50MC Mk 6, with

a Specified Maximum Continuous rat-

ing of 10,126 kW at 127 rpm, originally

equipped with two turbochargers. In or-der to optimise engine performance for

the prototype EGR test, modifications in

the engine room are carried out to the

Before - cylinder 1

Before - cylinder 4

After - cyl inder 1

After - cyl inder 1



MAN B&W Diesel


existing main engine scavenge air cool-

ers, and the turbochargers:

The two existing turbochargers are

replaced with one high effiency tur-

bocharger with variable turbine areas

A new charge air inlet pipe

The exist ing exhaust gas receiver tur-

bocharger outlet pipes are blanked

off, and a new exhaust outlet pipe is

installed

The existing turbocharger exhaust

outlet pipe is modified to fit the new

turbocharger

Strengthening of the existing turbo-

charger foundation.

The EGR system is designed for mini-

mum 20% recirculation of the exhaust

gas corresponding to minimum 50%

reduction of emitted NOx compared to

the basis emission level.

Service Test Objective

The main objective of the service test is

to investigate the engine impact of run-

ning with EGR, i.e. cylinder condition,

exhaust system condition and EGR

system condition. Besides perform-

ance, settings and controlling software

need to be tested “in situ” in order to

tune the controlling system to the best

possible performance.

Design of a Retrofit EGR System

The first retrofit EGR system is specifi-

cally designed for installation on Alex-

ander Maersk, using know-how ob-

tained during years of testing on the

4T50ME-X test engine in Copenhagen.

The fi rst stage was to establish the en-

gine performance on Alexander Mae-

rsk, followed by a simulation of the EGR

process. The next stage was to specify

the EGR components.

The main EGR components are: scrub-

ber, cooler, water mist catcher, blower,

shut-down valve, change-over valve,

water treatment plant, NaOH dosing

Shut down valveScrubber

Prescrubber

Blower

SeaWMC

FW

Cooler

Sludge

tank

Water

cleaning

P o l i s h i n g

Scrubber pump

NaOH

tank

NaOH

pump

Buffer

tank

Change over valve

Discharge

control

valve

On/off

valve

Stop

valve

Exhaust outlet

Mix

Cooler

WMC

Fig. 9: EGR system layout on Alexander Maersk




system and water cleaning unit. Be-

sides, there is a controlling system for

controlling the amount of recirculatedexhaust gas, the scavenge air pressure,

the dosing amount of NaOH, the circu-

lated scrubber water amount and the

scrubber water discharge amount.

As the water flows through the scrub-

ber it will become acidic due to the sul-

phur content in the exhaust gas which

dissolves in the water. A NaOH dosing

system is therefore a part of the EGR

system.

A signif icant amount of Particulate Mat-

ter (PM) will become suspended in the

scrubber water, which will eventually

cause failure in the components in the

WTP. It is therefore necessary to have

a Water Cleaning Unit (WCU) which can

remove PM from the scrubber water,

and discharge the PM as concentrated

sludge into the sludge tank on the ves-sel. The WCU is designed for cleaning

the scrubber water to such an extent

Fig. 10: Design of EGR unit Fig. 11: Design of new turbocharger with variable geometry and charge air

pipe

Fig. 12: Design of EGR arrangement on Alexander Maersk

that it can be discharged into open sea

in compliance with IMO scrubber water

discharge criteria when excess of wa-

ter gain from the combustion processis present.



MAN B&W Diesel


Fully Automated EGR System

In order to make the EGR system easy

to operate for the ship crew and to en-

sure correct and fast reactions to engine

load variations, a fully automated EGR

control system has been developed.

A standard MAN Diesel & Turbo MPC

controller is used as the main controller,

and as a secondary system, a Siemens

PLC is used for controlling the water

system.

The EGR Control Unit controls:

The EGR ratio (the ratio between re-

circulated exhaust gas and the scav-

enge air). The EGR ratio is measured

by the O2 concentration in the scav-

enge air and is controlled by adjust-

ing the blower speed and the position

of the change-over valve.

The scavenge air pressure (pscav).

The scavenge air pressure is adjust-

ed to a specified value as a function

of load and EGR rate. The scavenge

air pressure is controlled by adjusting

the variable nozzle ring on the turbine

inlet with the MC-SCU controlling

unit.

Fig. 13: Scrubber WCU (Water Cleaning Unit) from Bollfilter

WTP (HMI) MOP (HMI)

WTP CS

Water treatment

Plant

EGRCU

C O

V

a l v e

S D V a l v e

B l ow e r

V T

P s c a v m e a s

R P M ,I n d e x

O2 m e a s

SCU

Engine

Engine control room Engine room

EGR control system

EGR System

The WTP PLC controls the following:

EGR cooler water flow

scrubber water flow scrubber water discharge amount

pH value of the scrubber water

water cleaning unit.

Fig. 14: EGR SW architecture Fig. 15: EGR user interface on the Main Operating Panel

The timing of start-up and shut-

down of the WTP (Water Treatment

Plant) is controlled through a genericinterface.

A separate control system for the WTP

has also been developed by MAN Die-

sel & Turbo, based on a standard PLC

controller.




Installation of EGR

In July 2009, Alexander Maersk docked

at Lisnave shipyard for 30 days, during

which all the large EGR components

were installed and the majority of the

installation work completed.

The EGR unit is installed on the mid-

dle platform, adjacent to the exhaust

receiver on the main engine. A hole is

cut in the exhaust receiver and a gas

pipe mounted inside to divert the ex-

haust through the EGR system. The

recirculated exhaust is then reintro-

duced to the Main Engine (ME) before

the scavenge air coolers, by means of

a specially designed charge air pipe.

The two original standard efficiency tur-

bochargers are removed and a single

high efficiency turbocharger with vari-

able turbine geometry installed in theirplace, so the new charge air pipe also

distributes the compressed scavenge

air between the two existing charge air

cooler housings. The charge air cooler

elements have also been replaced by

special nano-coating elements to pre-

vent corrosion that may occur due to

the condensation of sulphuric acid,

caused by possible carry-over of SOx.

Fig. 16: EGR unit installed on Alexander Maersk

Fig. 17: Turbocharger with variale geometry Fig. 18: EGR blower at testbed

A significant amount of pipe work for

the WTP has been carried out in or-der to provide feed water for the EGR

scrubber. The largest component of the

WTP is the buffer tank, which ensures a

constant water flow to the EGR scrub-

ber. The scrubber pump is located be-

neath the buffer tank and supplies wa-

ter to both the EGR scrubber and the

EGR pre-scrubber (cooling the exhaust

gas). Dirty scrubber water then drains

from the bottom of the EGR scrubberto the buffer tank through a steam trap

to separate any remaining exhaust gas.

A separate pump circulates dirty wa-

ter in the buffer tank through the Wa-

ter Cleaning Unit, where the water is

cleaned for PM and returned to the

buffer tank. When required the cleaned



MAN B&W Diesel


water can be discharged overboard,

or sent to the vessel’s dirty bilge tank,

by means of a three-way valve. Addi-

tional connections to the vessel include,

a fresh water supply directly into the

buffer tank and seawater for the EGR

cooler.

EGR in Service

Commissioning of the EGR system

on Alexander Maersk was carried

out in March 2010. All gas and water

pipe work is pressure-tested, the sys-

tem functionality has been established

and an initial service test of 500 hrs is

planned to evaluate the performance of

the EGR system. An additional 3,000

hrs in service is then planned for further

evaluation of the EGR. An important

part of the service test is to assess the

effect of EGR on a main engine over aperiod of time with the engine running

on Heavy Fuel Oil (HFO). Therefore,

there will be regular inspections on the

main engine by MAN Diesel & Turbo to

investigate and observe the conditions

of the cylinder impact, if any, of EGR on

the two-stroke marine engine.

Results of EGR in Service

The commissioning of the EGR system

on Alexander Maersk started in late

March 2010 and continued in April with

a scheduled full scale performance and

emission and water treatment system

test. Until now, the preliminary results

from the commissioning test have con-

firmed our expectations with confirmed

satisfactory performance of:

EGR scrubber

EGR blower EGR water mist catcher.

Fig. 19: Scrubber and EGR water mist catcher after a few hours service test

The performance of the water treatment

system could not be confirmed as this

system failed at a very early stage in the

commissioning. However, the cause of

failure is recognised and will be rectified

in mid-April 2010.

Fig. 19 shows the condition of the EGR

scrubber element and reversing cham-

ber after EGR cooler, both confirming

perfect condition after few hours of EGR

operation with heavily contaminated

scrubber water (water treatment system

out of operation).




EGR in the Future

The EGR test results obtained on the

4T50ME-X test engine show that EGR

is a promising IMO Tier III candidate

for the large two-stroke diesel engines,

especially for electronically controlled

engines equipped with turbochargers

having variable turbine areas, where

suitable control of excess air ratio

(scavenge air pressure and compres-

sion ratio) and injection pressure and

pattern (combustion process) can se-

cure minimum penalty on CO2 (SFOC)

and other emission parameters like CO

and HC (Hydro Carbons). Implementa-

tion of high-ratio EGR on mechanically

controlled engines needs further inves-

tigation if acceptable penalties on other

emission components than NOx have to

be secured.

Investigation of the EGR blower per-

formance and efficiency will be contin-

ued in a cooporation between our tur-

bocharger department and low speed

department. A new EGR blower design

based on the standard TCA/TCR turbo-

charger compressor design with an ef-

ficiency of approx 80% will be tested at

the end of 2010.

Further integraton of the EGR system

into the engine design is a future chal-

lenge which already today is taken into

consideration, as can be seen in Fig.

20.

Fig. 20: Future concept of an EGR Tier III two-stroke diesel engine



MAN B&W Diesel


N O

40% urea solution

CO (NH2 )

2• 5(H

2O)

Exhaust gasNO

2

N2

NH3

H2O

SCR

Reactor

4NO + 4NH3

+ O2

= 4N2

+ 6H20

6NO2

+ 8NH3

= 7N2

+ 12H20

NN

N N

N

N

N N

N

N

N

N

O

O

OO

H

H

H

H

H

H

H

H

H

H

Fig. 21: Principles of the SCR system

NOx Compliance with SCR

SCR Technology

An alternative way of meeting the IMO

Tier III NOx limits is to install a SCR reac-

tor. In the reactor, NOx is reduced cata-

lytically by a suitable reducing agent to

nitrogen and water, see Fig. 21.

Compared to other NOx reducing tech-

nologies, the SCR technology has the

advantage that it is a proven technol-

ogy. SCR reactors have been used in

power plant applications since the late

seventies, and MAN Diesel & Turbo was

involved in one of the first marine appli-

cations in 1989. However, whereas the

technology involves mature and robust

power plant applications, the technol-

ogy still needs to be matured for daily

and continuous marine operation on

HFO. Therefore, MAN Diesel & Turbo isinvolved in a targeted development of

this technology together with a catalyst

manufacturer and engine builder.

Objective

The SCR project was initiated together

with external partners in 2009, and the

purpose of the project is to develop

SCR solutions for the entire MAN Diesel

& Turbo two-stroke engine programme.

This means that SCR solutions will be

available for both MC, ME and ME-B

engines in due time for Tier III. Cur-

rently, it has been decided to target the

development at high-pressure (between

engine and turbocharger) SCR and op-

eration on heavy fuel oils (HFO). This is

illustrated in Fig. 22.

The objective for MAN Diesel & Turbo

Low Speed is to have a specification fora Tier III engine available by the end of

2012. For the catalyst manufacturer, the

Fig. 22: Arrangement of a high-pressure SCR solution

main objective is to obtain a specifica-tion for an SCR reactor, which matches

large two-stroke diesel engines.




Content of the Development Work

The application of high pressure SCR

(normally used on two-stroke engines)

is more tedious than similar installations

of low pressure SCR after the turbo-

chargers (normally used on four-stroke

engines). Due to the high turbocharger

efficiency application and the high en-

ergy efficiency of two-stroke diesel en-

gines, the exhaust gas temperatures

after the turbocharger are lower com-

pared to the temperatures obtained

on four-stroke diesel engines. For two-

stroke diesel engines, temperatures are

typically in the range from 230 to 260°C

after the turbocharger. Normally, the

SCR inlet gas temperature should ide-

ally be around 350°C when the engine

is operated on HFO. Currently, this tem-

perature condition has called for a solu-

tion where the SCR is situated on thehigh pressure side of the turbine. De-

pendent on the engine load, this makes

it possible to obtain SCR inlet tempera-

tures, which are between 50 and 200°C

higher than the temperatures which can

be obtained as SCR inlet temperatures

with SCR placed after the turbocharger,

see Fig. 23.

The SCR has a significant heat capac-

ity and because the SCR is fitted before

the turbocharger this constitutes a chal-

lenge in terms of control and regulation.

Due to the heat capacity, it is neces-

sary to bypass some of the exhaust

gas directly to the turbocharger during

engine start-up and possibly also under

extreme acceleration in order to ensure

sufficient energy input to the turbine.

For the same reason, it may be neces-

sary to bypass the turbine during de-acceleration of the engine as the energy

level of the exhaust gas from the SCR

is too high.

500

450

400

350

300

250

200

150

100

50

20 30 40 50 60 70 80 90 100

Turbine Inlet Temp (normal)

Engine Massflow (normal)

SCR Requirement ???

6S50ME-C8 9960kW

Power %

D e g C & k

g / s e c * 1 0

Fig. 23: Measured turbine inlet temperatures

500

450

400

350

300

250

200

150

100

5020 30 40 50 60 70 80 90 100

Turbine Inlet Temp (normal)

Engine Massflow (normal)

Turbine Inlet Temp (WHR)

Engine Massflow (WHR)

Turbine Inlet Temp (SCR)

Engine Massflow (SCR)

SCR Requirement ???

6S50ME-C8 9960kW

Power %

D e g C &

k g / s e c *

1 0

Fig. 24: Manipulation of exhaust gas temperature by turbine bypass



MAN B&W Diesel


Despite this arrangement, the required

exhaust gas temperature for trouble-

free SCR operation may not be ob-

tained. This is especially a problem at

lower loads where the temperature is

well below 300°C, see Fig. 23. As a

countermeasure for the too low exhaust

gas temperature, it will be possible to

increase the exhaust gas temperature

by utilising a turbine bypass possible in

combination with variable turbocharg-

ers. This measure decreases the air

flow through the engine and thus in-

creases the exhaust gas temperature.

The preliminary calculations shown in

Fig. 24 reveal that it is possible to tailor

the desired exhaust gas temperature for

a broad range of load points. However,

the figure also clearly shows that the

exhaust gas temperature in the lowest

IMO load point remains a challenge.

The exhaust gas temperature is not the

only issue, which is addressed in this

project. In previous SCR installations,

clogging of the catalyst has caused ma-

jor operational problems. Clogging is

mainly caused by the presence of sul-

phur which together with ammonia and

calcium forms ammonium sulphates

and gypsum, respectively, see Fig. 25.

This phenomenon may be further ac-

celerated due to the vanadium in the

HFO, which facilitates oxidation of SO2

to SO3.

These problems may be avoided by an

increased exhaust gas temperature, but

it needs to be confirmed by actual tests.

Furthermore, it has also been found that

the purity of the urea is a main key for

Fig. 25: Catalyst blocked by various sulphates

trouble-free SCR operation. Certain im-

purities may cause polymerisation of the

urea, which eventually causes blockage

of the catalyst elements.

Outcome of the Project

The previous sections illustrate that sev-

eral parameters related to the operation

of marine SCR remain unknown, or less

well understood, despite the extensive

industrial application of SCR since the

late seventies. However, the collabo-

ration between the engine designer,

engine builder and SCR manufacturer

constitutes a strong partnership, which

will make it possible to overcome these

challenges. In due time for Tier III, MAN

Diesel & Turbo will provide the following

to its licensees.

Software specifications for the by-

pass system

Hardware specifications for the by-

pass system

Detailed requirement specifications

for an SCR reactor.

MAN Diesel & Turbo will not provide

Detailed design related to the SCR

system.




Test Facilities and Time Schedule

To ensure a proper and targeted de-

velopment of the entire SCR system,

a widespread test programme is in the

making. This involves fundamental high

pressure SCR tests on a 1,000 kW two-

stroke test engine, and on an 8,000 kW

production engine on testbed. In par-

allel, service tests are planned to take

place from the middle of 2011 on an

8,000 kW two-stroke diesel engine. The

time schedule is summarised in Fig. 26.

described. The description includes

comments to water treatment methods

for both closed loop (FW (Fresh Water))

and open loop operation (SW (Sea Wa-

ter)), energy consumption of scrubber

system and consumption of neutralising

agents.

Design & Build

experimental

SCR system

Collect

Experiences

Selection

of

ship for

prototype

installation

Design of SCR

system for

marine

application

Installation

of

prototype

in a ship

In service

experiments

Evaluation

of

SCR

performance

Fundamental

SCR

experiments

Fundmental

control

experiments

on

production

engine

Final

implement of

choosen

control and

SCR solution

2009 2010

2010

2011

2011 2012

SCR investigations

SCR sevice test on marine installation

Fig. 26: Development schedule for the SCR project

Fulfilling IMO Sulphur Requirements

in Fuel and/or SO2 in Exhaust Gas

As for NOx emission, MAN Diesel &

Turbo has chosen a flexible and ag-

ile two-way approach for MAN B&W

two-stroke engines with regard to SOx

emission fulfilling future regulations. In

the following, the efforts for improving

the capability of our engines for low

sulphur fuel operation and the results

from both testbed and service test-

ing of wet scrubbers for SOx and PM

(Particulate Matter) will be outlined and



MAN B&W Diesel


SOx Compliance with Wet Scrubber

Wet Scrubber Implementation on

MAN B&W Engines

Scrubber test on 1 MW four-stroke engine at

MAN Diesel & Turbo at the Holeby plant

In 2008, a test programme for exhaust

gas scrubbers was commenced in the

MAN Diesel Holeby plant. The test pro-

gramme was run in cooperation with

Aalborg Industr ies and MAN Diesel &

Turbo.

The test series comprised a total of 126

different tests on a four-stroke 1 MW

HFO burning MAN Holeby GenSet en-

gine.

A number of running scenarios and

cleaning principles were investigated,

the primary being Salt Water scrubbing,

Fresh Water scrubbing with NaOH addi-tion, Straight flow, Jet and Venturi solu-

tions.

At the same time, a separate test pro-

gramme was carried out on water treat-

ment solutions by Alfa Laval in Sweden.

The main purpose was to test the ca-

pabilities of the Alfa Laval Eco Streamer

system.

The test series in Holeby yielded very

promising results – a more than 98%

SO2 reduction and a reduction of up to

78% PM was reached.

Based on the good results from the

scrubber tests, it was decided to carry

out a full scale test on a larger two-

stroke engine and the search started for

a test vessel.

Fig. 27: Holeby test plant

The main advantages of wet scrubbing

are:

SO2 reduction at least 98%

PM reductions up to 78%

Substantial fuel savings – especially

after July 2010 – compared to run-

ning low sulphur or distillate fuels

which are mandatory within ECA

Lower global CO2

footprint com-

pared to distillate fuels which require

significant energy consumption at re-

fineries.

During the prototype testing period,

talks were initiated between MAN Die-

sel & Turbo, Aalborg Industries and the

Danish shipowners DFDS.

Due to the fact that DFDS’s core traf-

fic is almost 100% inside the ECA ar-

eas with the consequent restrictions

in SOx emissions, the company had

for some time been looking at different

SOx cleaning solutions. After discuss-

ing the test results from Holeby, it was

decided to carry out a full scale testing

of the scrubber system on a DFDS Ro-

Ro vessel.




Full Scale Installation on DFDS

Vessel Tor Ficaria

The vessel chosen for the full scale in-

stallation is a 32,389 GT Ro-Ro vessel

built in 2006 by Flensburger Schiffbau

Gesellschaft in Germany.

The vessel is equipped with a 20 MW

MAN B&W 9L60MC-C main engine,

giving her a service speed of 22.5 knots

and the vessel is trading a fixed North

Sea route between Gothenburg in Swe-

den and Immingham, the UK.

The 20 MW installat ion will be the big-

gest scrubber in the world on a seago-

ing vessel.

The installation of the main scrubber

components was carried out during a

docking in June/July of 2009. The fi-nal installation work of pumps, coolers,

piping systems and electrical systems

has been carried out in service during

the fall/winter of 2009 and was finished

by the end of February 2010. Commis-

sioning and initial testing of the system

will follow immediately after finishing the

installation.

The system chosen for DFDS is capa-

ble of running as an open loop pure Sea

Water (SW) scrubber as well as a closed

loop Fresh Water (FW) scrubber.

The system will run as a pure SW scrub-

ber during normal sea passage. When

entering coastal areas, ports or an

estuary, the system will automatically

be switched over to a closed loop FW

scrubbing.

By-pass

Steam or

Jacket water

Demister

Sea Water

Overboard

Engine

exhaust

gas

Jetscrubber

By-pass

Engine

exhaust

gas

Fresh WaterNaOH

Sea Water

Demister

Water polishing / sludge tank

Steam or

Jacket water

Fig. 28: Running in Sea Water mode

Fig. 29: Running in Fresh Water mode



MAN B&W Diesel


Fig. 30: Installation of scrubber at yard

Sea Water Scrubbing

Sea water scrubbing is intended as the

main running mode. Sea water is sup-

plied via the vessel’s normal cooling wa-

ter pumps, through a booster pump for

a one time passage through the scrub-

ber. The amount of sea water through

the scrubber ensures sufficient reaction

to the sea salts and sufficient dilution

to allow the scrubber water to be dis-

charged directly into the sea without

further cleaning. All values and criteria

for wash water discharge with regard to

PH values and PAH are fulfilled.

To ensure sufficient Sea Water, as much

as 900 m3/hr has to be pumped (at 20

MW engine power). However, as the

engine is normally running only around

80% MCR, the sea water pump is con-

trolled through a frequency converter,adapting the pump power to the engine

power and thus saving KW power.

The maximum fuel penalty for running

the scrubber system in sea water mode

is expected to be around 1% main en-

gine power.

Fresh Water Scrubbing

When entering coastal areas or ports

where no discharge is allowed, the sys-

tem will be switched over to fresh water

scrubbing. The switch will be carried

out automatically by a push button re-

quest from ECR or BC.

When running in fresh water mode,

99% of the fresh water is recirculated in

a closed loop from a special fresh wa-

ter/dosage tank through the scrubber,

using the same booster pump as used

by the SW mode. Thus, only a fraction

of the water will have to be cleaned anddischarged.

Due to the addition of NaOH as a SO2

neutralising agent to the scrubber fresh

water, a significantly lower amount of

water is needed. It is expected that a

fresh water maximum of 200 m3 /hr (at

MCR) is sufficient. As this is only around

one fifth of the needed sea water power,

this will of course significantly reduce

the necessary power costs to run the

system.

To be able to neutralise the SO2, NaOH

is added via a small dosage pump into

the dosage tank. If running on HFO, fuel

with a 3% SO2 content, calculations

confirmed by the prototype tests, will

show a needed NaOH consumption of

approximately 10-12 kg/MWh.

Since the FW mode is used only dur-

ing harbour or coastal sailing, the mainengine power will be low and the sail-

ing time will be short, further reducing

the NaOH consumption. A typical arrival

to port will be maximum two hours and

maximum 2-3 MW engine power, giv-

ing a total consumption of around 50 kg

NaOH.

During FW running, no water is dis-

charged from the vessel. As the running

time is short the circulated amount of

fresh water is fully capable of consum-

ing the PAH and SO2 extracted from

the exhaust gas. When leaving port and

switching back to SW mode, the now

polluted fresh water in the fresh water

system tank will be cleaned through a

filtration unit working independently of

the scrubber system.




Results of Scrubber in Service

The commissioning of the full scale

scrubber installation on Tor Ficaria

started, as for the EGR system, in late

March 2010 and will continue in April

and May 2010 with a planned per-

formance on SO2 and PM (Particulate

Matter) reduction capabilities in both

closed loop and open loop operation

in the last week of April. Unfortunately,

obtained results from the performance

test cannot be reported on in this pa-

per. However, it can be reported that all

sub-system commissioning has been

completed with satisfactory results.

Fig. 31: Tor Ficaria



MAN B&W Diesel


Low Sulphur Fuel Operation

Today, the average sulphur content of

fuel oil used for marine diesel engines

is 2.7%. This will change as the Sulphur

Emission Controlled Areas (SECAs) are

well implemented and widened.

The authorit ies have reduced the SOx

content in the exhaust gas by introduc-

ing limits on the content of sulphur in

the oil used. However, also cleaning

of the exhaust gas by scrubbers is al-

lowed.

An overview of the limits on the sulphur

content in the oil in different areas and

the upcoming changes are shown in

Fig. 32.

Due to these regulations, more engines

will have to operate on low sulphur fuelin the coming years.

Engine Challenges and

Recommended Solutions

Our two-stroke engines are optimised

to operate on heavy fuel with a high sul-

phur content. Thus, the low sulphur fueltypes hold challenges to our engines.

The main challenges are:

Global: 4.5 → 3.5 → 0.5

SECA: 1.5 → 1.0 → 0.1

CARB MGO: 1.5 → 1.5 → 0.1(DMA)

CARBO MDO: 2.0 → 0.5 → 0.1(DMB)

Global

SECA

CARBPhase 1

CARB

Phase 2

2000 2005 2010 2015 2020 2025

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

S u l p h u r %

S u l p h u r %

S u l p h u r %

Year Year Year

July

2009

July

2010

Jan

2012

Fig. 32: Limits on the sulphur content in fuel SECA: Sulphur Emission Controlled Areas. Today: Baltic

Sea, English Channel Coming: Mediterranean, 200 nautical miles zone at US cost CARB: Californian Air

Resources Board: 24 nautical miles of the Californian baseline

Table 3

Main Fuel Characteristics

Fuel type Fuel characteristics Engine challenges Recommended solutions

HFO High sulphur

High viscosity

Optimised Standard

LSHFO Low sulphur

High viscosity

Cylinder condition 40 BN cylinder oil

Piston rings with cermet coating

Distillates Low sulphurLow viscosity Low lubricity

Cylinder conditionFuel atomisation

Fuel pump seizure?

40 BN cylinder oilPiston rings with cermet coating

Fuel viscosity > 2 cSt before engine inlet

Test rel iable ser vice before ente ring high-risk

areas, e.g. ports

to secure cylinder condition with a

very low level of acid corrosion

to avoid scuffing and ensure reliable

fuel system operation at very low vis-

cosities to avoid scuffing in the fuel system at

very low lubricities.

Low sulphur

The decrease in sulphur in the fuel re-

duces the corrosive wear in the cylinder

liners. This might lead to liner polishing

followed by heavy scuffing.




Fig. 33: Seizures on K90MC plunges after 24 hrs at 60°C, i.e. 1.6 cSt

Low Viscosity

Distillates consist of shorter chains of

hydrocarbons. That is why the viscosity

of distillates is very low. When viscosity

gets very low, leakages in the fuel sys-

tem will by nature increase and the fuel

pumps will have difficult conditions for

building up the necessary pressure to

overcome opening pressures in the fuel

valves, especially at very low loads ( low

fuel amounts) with very low rpm. In this

connection, electronically controlled en-

gines, will have a significant advantage

compared to mechanically controlled

engines, as the influence of engine rpm

on fuel injection is eliminated on elec-

tronically controlled engines.

Furthermore, the viscosity of the fuel oil

has a significant influence on the oil film

thickness between the plunger and thebarrel in the fuel pump, and low viscosi-

ty fuel oils will accordingly be promoting

scuffing behaviour between the plunger

and the barrel.

Low Lubricity

When processing very low sulphur fuel,

the hydrocarbons in the fuel are also

changed. This is the reason why low

sulphur fuels (<0.05% S) have lower lu-

bricity – further sulphur itself promotes

lubricity. The low lubricity is accordingly

expected to increase scuffing behaviour

of all fuel system components where

metal surfaces slide up against other

metal surfaces. However, tests strongly

indicate that viscosity has a much high-

er influence on scuffing conditions than

lubricity.

The main fuel characteristics, enginechallenges and our recommended solu-

tions are illustrated in Table 3.

Distillate Tests

To test our standard equipment ability

to run on the distillates supplied to the

market today, we have been running

tests with a very low viscosity fuel. The

fuel was an automotive diesel contain-

ing automotive lubricity additives and

small amounts of bio fuel.

The tests were run in our in-house test

rigs, with standard fuel equipment from

engine types K90MC-C and S50ME-C.

Testing standard fuel equipment on low vis-

cosity and lubricity fuel oils

The tests showed that our S50ME-Ctest rig was able to establish a suitable

fuel pressure for injection and atomisa-

tion at very low injection amounts down

to a fuel viscosity of 1.1 cSt, whereas

the K90MC-C test rig was only able to

do the same at a fuel viscocity of 2.2

cSt. This confirmed our evaluation that

ME-C engines have a higher capability

of low load operation on low viscos-

ity fuels than our standard fuel system

equipped MC/MC-C engine types.

The above measurement results also

clearly indicate that further develop-

ment of fuel equipment capable of han-

dling low viscosity fuels are required.

This development is already initiated

with development of fuel pump plung-ers and barrels with special coatings,

entering service in the middle of 2010.



MAN B&W Diesel


Fig. 34: Test rig

Seizure testing

In order to confirm the ability of our

standard fuel system equipment to op-

erate on low viscosity fuels, we have

made subsequent tests on both our

S50ME-C test rig and our K90MC-C

test rig.

The tests start at approx. 3 cSt fuel oil

viscosity and the test rig is operated

100 hours at this viscosity. After 100

hours' testing the viscosity is loweed by

increasing the fuel oil temperature. The

100-hour testing is repeated. The tests

are repeated until seizure between the

plunger and barrel is obtained.

The tests showed that our S50ME-C

test rig was able to run without seizures

on fuel with 1.2 cSt for 100 hours (at

this point we were not able to lower vis-cosity any further due to a lack of fur-

ther heating capability). The 90MC test

rig was able to run without seizures on

fuel with 1.6 cSt for 24 hours. These re-

sults correspond well to the fact that the

MC-fuel pump experiences larger side

forces while running.

As the test was performed on automo-

tive diesel containing automotive lubric-

ity additives and small amounts of bio

fuel, it does not fully test our equipment

ability to run on virgin low viscosity, low

lubricity fuels. However, the tests con-

firm the robustness in our equipment

running on the fuels available on the

market today.

Further Tests

As the market will shift towards running

on more distillates, we might see pure

marine distillates on the market. These

fuels might be without in-land, automo-

tive lubricity additives or bio fuels. To be

able to run on this type of fuel, we are

planning a new test on a low viscosity,

low sulphur, low lubricity type of fuel.




Conclusion

This paper has illustrated that MAN Die-

sel & Turbo takes the Tier III challenge

very seriously, and is securing that suit-

able solutions can and will be available

in due time before the IMO legislation

on emissions is enforced.

The near future will require further de-

velopment testing of EGR systems,

SCR systems and fuel system com-

ponents for very low sulphur fuels but,

even more importantly and challenging,

these systems will also require further

full scale testing in service. Securing

the possibility of full scale testing of full

scale systems on newbuildings to come

in the near future will call for our licen-

sees’ full cooperation and assistance to

find and convince yards and owners to

participate in the testing efforts.



C o p y r i gh t © MA N D i e s e l & T ur b o· S u b j e

c t t om o d i f i c a t i oni n t h e i n t e r e s t of t e c h ni c a l pr o gr e s s .·

5 5 1 0 - 0 0 8 8 - 0 0 p pr J ul 2 0 1 0 P r i n t e d i nD

e nm a r k

MAN Diesel & Turbo Teglholmsgade 41, 2450 Copenhagen

Denmark

Phone +45 33 85 11 00

Fax +45 33 85 10 30

[email protected]

www.mandieselturbo.com

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