A CONCEPT OF A MARINE POWER PLANT SUPPLIED WITH …

QUARTERLYISSN 1232-9312 3/2017 (106)

PROBLEMY EKSPLOATACJI

Journal of MachineC o n s t r u c t i o n and Maintenance

Andrzej ADAMKIEWICZ*, Mateusz PRZYBYŁA**

* Maritime University of Szczecin, Faculty of Marine Engineering, Poland [email protected]** Poltramp Yard S.A., Świnoujście, Poland [email protected]

A CONCEPT OF A MARINE POWER PLANT SUPPLIED WITH NATURAL GAS WITH A REDUCED CO2 EMISSION INDEX

Key words: marine power plant, CO2, Waste Heat Recovery System, EEDI, Ro-Pax vessel.

Abstract: This paper shows the background for the development of the Ro-Pax type ships in the Baltic Sea area as the Emission Control Area (ECA) that led the authors of the paper to use the Energy Efficiency Design Index (EEDI) as a measurement of meeting the requirements of the International Maritime Organization (IMO). For the studied concept of the marine power plant, dual fuel main engines manufactured by MAN B&W and adjusted for the requirements of ECA have been chosen. The mathematical model for the power plant that was used to perform calculations for various ranges of engine load was described. The value of the EEDI has been determined for the three studied possible kinds of fuel.

Koncepcja okrętowego układu energetycznego zasilanego gazem ziemnym o zredukowanym wskaźniku emisji CO2

Słowa kluczowe: napędy morskie, CO2, system odzyskiwania ciepła z odpadów, EEDI, statki typu Ro-Pax.

Streszczenie: W artykule pokazano tło rozwoju statków typu Ro-Pax w akwenie morza Bałtyckiego jako strefy objętej Emission Control Areas – ECA. Fakt ten skłonił autorów do wykorzystania Energy Efficiency Design Index – EEDI jako miary spełnienia wymagań International Maritime Organization – IMO. Przyczynił się on do opracowania niniejszego artykułu. Dla opracowywanej koncepcji układu energetycznego dobrano dwupaliwowe silniki główne firmy MAN B&W, dostosowując je do wymagań strefy ECA. Opisano model matematyczny układu energetycznego, w oparciu o który wykonano obliczenia w funkcji różnych zakresów obciążeń silników. Wartości współczynnika EEDI wyznaczono dla rozpatrywanych trzech moż-liwych rodzajów paliwa.

Introduction

Economic development of the countries fromtheBalticSea regiongenerates the need to build newships that will meet the requirements of the increasing transportation needs while abiding by environmentalprotection regulations.As a consequence of intensivedevelopment, the construction of the first in a seriesof ferriesof theRo-Pax typeorderedbyaPolishshipowner was started and one of a similar type has been purchasedandisinoperation.Suchshipsaredestinedto

operate in the ECA region with limits on the emission of sulphurandnitrogenoxides(SOxandNOx).Asignificantcontribution of marine transport into the global emission ofcarbondioxidemadeIMOintroduceEEDIin2013.According to the definition, the index is a quotient ofthe amount of the emitted carbon dioxide to the amount ofcargotransportedbytheshippernauticalmile.Theexpected value ofEEDI for a given type of shipmaybereachedinanumberofways, themosteffectiveofwhich is by employing waste heat recovery from theshipengineoperation.

p. 7�–82

76 Journal of Machine Construction and Maintenance | PROBLEMY EKSPLOATACJI | 3/2017

The complexity of processes of chemical treatment ofexhaustandwasteheatrecoveryaswellasthechancetouseLNG,apartfrommarinefuels,createsadecisionmaking problem at the designing stage. Those factsconvinced theauthors tomakeanattempt toworkoutaconceptofapowerplantforapassenger-vehiclevesselenabling the performance of a transportation task in the ECAregion.

1. Analysed vessel and power plant

Dimensionsandmainparametersofthepassenger-vehicle vessel described in paper [1] and listed inTable 1were used for initial calculations of the shippowerplant.Adecompositiondiagramofthedesignedpower plant together with marked state parameters of theworkingmediaofthewasteheatrecoverysystemisshowninFig.3.

Forthepropulsionsystemofthevessel,twodrivingunitswithmedium-speeddieselengineswereproposed.

Using a reductiongear and shafts, twopropellers aredriven with a regulated pitch. The ship power plantalso comprisesmachines and equipment servicing themainpower,enablingtherealizationofcycles,andthecontrolledtransferofpower.Holtrop’smethod[1,5]wasused for initial calculations of power in the conceptual design, aswell as characteristics of free propellers ofWageningen-CmodelsdevelopedbyMaritimeResearchInstitute Netherlands – MARIN (Maritime ResearchInstitute Netherlands) [4]. A system of non-linearequations in the range of [120–145 min–1] rotationalspeeds of the propeller was solved using an iterationmethod in order to determine the non-dimensional coefficients of advance, moment, and thrust of thepropeller. Optimum rotational speed was determinedat the moment when the maximum efficiency of theopenwater propeller,η0was reached.The determinedparametersofdrivingpropellersandtheassumedrangesofoperationalpowervaluesenabled thedeterminationof the nominal power of the continuous operation of the enginesofthemainpowerplant.

Table 1. Main parameters of the designed vessel

No. Unit Value Description No. Unit Value Description

Lpp [m] 179.2 Lengthbetweenpp. vs [m/s] 10.55Servicespeed

Kl [m] 184.7 Length on waterline [knt] 20.50

B [m] 29.5 Breadth z [–] 2 Number of propellers

T [m] 7.15 Designdraft P0.7R /D [–] 1.2 Pitch – diameter ratio

CB [–] 0.65 Blockcoefficient nP [1/min] 134 Propellerrevolutions

Δ [Mg] 25200 Mass displacement Z [–] 2 Number of engines

mDWT [Mg] 7471.5 Deadweight PcSR [kW] 8400 Power of each engine

Source:Ownelaborationonthebasisof[1].

2. Determination of the type of main engines

Possible dual fuel engines from the most popular manufacturers on the ship market, i.e. MANB&W 61/50DF andWärtsilä 46DF, were considered.The criterion of choice for the dual fuel engine was its specific heat consumption and themanufacturer’sdeclaration regarding meeting the IMO Tier IIIregulation.Whennaturalgasisused,thespecificheatconsumptionisdeterminedasthesumofspecificgasconsumption (calorific value of liquefied natural gas48,0MJ/kg) and that of the pilot dose of oil (WFO = =42,7MJ/kg):

� �

� �q q b W

q q kJ kWhfNG NG fPFO FO

NG fPFO

= + ( ) == + [ / ]

(1)

Inthecasewhenonlyoilisused,forthegiventhespecific fuel consumption listed by the manufacturer[6],therelationforthespecificheatconsumptionisasfollows:

�q b W kJ kWhfFO fFO FO= [ / ] (2)

Determination of specific heat consumption forthe studied engines of the main power system of the designedferryisshowninFig2.

Graphic representations of relations (1) and (2)indicated the most advantageous values of specificheat consumption of engines of the 51/60 DF typemanufacturedbyMANB&W.Thefunctiondescribingthe specific heat consumption of the stated enginereaches its minimal value for the range of load of

Journal of Machine Construction and Maintenance | PROBLEMY EKSPLOATACJI | 3/2017 7777

85–94%.Whenitissuppliedwithoil,therangeofoptimumoperationisnarrower,i.e.85–88%ofthenominalpower.

Theaboveandthevalueofenginenominalpowerclosetothemaximumcontinuouspowerweredecisivefor choosing the engines of the 9L51/60DF typemanufacturedbyMANB&Wastheenginesofthemainpower.

The proposed power system takes into account the installationofawasteheatrecoverysystem(Fig.3)forthedesignparametersofsecondaryenergycarriers,andtheywereidentifiedforachosenengine.Temperature,exhaust gas mass, and charging air fluxes presentedin Fig. 2 refer to the situations when the engines aresuppliedwithbothnaturalgasandoil.

Fig. 1. Specific heat consumption for the studied dual fuel main engines

Source:Ownelaborationonthebasisof[1].

Fig. 2. Temperature and exhaust gas mass and charging air fluxes as a function of load of the 9L51/60DF type engine manufactured by MAN B&W type 9L51/60DF

Source:Ownelaboration.


To exemplify the advantages of applying naturalgasas fueloverusingmarineoil,parametersofwasteheatrecoveryandEEDIwerecalculated.

3. Mathematical model of power plant with Waste Heat Recovery System

The mathematical model of the designed power plant was constructed for an operational state i.e. seavoyage.Mathematicaldescriptionwasconfinedtobasicfunctions needed to carry out the transportation task at theexpectedvalueofEEDI.

Theenergybalancecomprisesflowsofthechemicalenergy of fuel supplied to main and auxiliary engines:

i ME

AE

Fij

F MEk

F AE

jF ME ME

j

k

j k

j

Q Q Q

q P

= = =

=

∑ ∑ ∑

∑

= + =

= ⋅

� � �

�

1

2

1

2

1

2

jj k kk

F AE AEq P( ) + ⋅( )=∑

1

2

�

(3)

The totalflowof energydelivered to the engines(3)isthesumofenergyflowsdeliveredtothemainandauxiliary engines equivalent to the sum of multipliedspecific heat consumptions and effective power. Theeffective power of main and auxiliary engines isdescribed as follows:

i ME

AE

e ij

e MEk

AEj

k

j kP P P

= = =∑ ∑ ∑= +

1

2

1

2

(4)

Assuming the efficiencyofηS propulsion transfer anddetermining rotational efficiencyaccording to [5],fortheknowncoefficientsofadvanceKT and torque KQ theeffectivepowerofmainengineswascalculatedfromthe relation below:

je MEj

S jD j

S jD P

S R jP

P P Qj j

= = =

=

∑ ∑ ∑

∑

= = =

=

1

2

1

2

1

2

1

2

1 1

1 1

η η ω

η ηω�

jj j j jK n DQ P P( )2 5

(5)

Thecontributionofelectricalenergyflowdestinedfor servicing the engines of the main power wascalculated using an empiric relation given byMarineEnvironmentalProtectionCommittee[7]:

kAE k

je MEj

o PTI oP PP

= =

=∑ ∑ ∑= +

1

2

1

21

2

0 025,0,75

+ 250 (6)

Calculations of parameters of the Waste Heat RecoverySystemhavebeenconductedfortheproposedconfiguration,whichconsistsofthefollowing(Fig.3):double-pressure steam-operated exhaust gas boiler – low pressure(1)andhighpressure(4),chargedair–boilerfeeding water heat exchanger of the engine (2), highpressuresteamseparator(3),lowpressuresteamseparator(5),steamturbinedrivingship’ssynchronousgenerator(6),andsteamcondenser(7).Thecalculationshavebeenconducted for the combustion products generated in the workingprocessofMANB&W8L51/60DFfortheload

range of PPSR

MCR

= ÷( , , )0 5 1 0 .Forthecalculationprocess

thefollowinghavebeenassumed:– Thehighandlowpressurefeedwatermassflowis

equaltothecalculatedsteammassflow:

m m m m mSSHP

SHHP

FWHP

S WHP

HP= = = =/ ,

m m m m mSSLP

SHLP

FWLP

S WLP

LP= = = =/

– The high pressure and low pressure boiler feed water temperature is equal to the temperature of saturated steam:

t tFWHP

SSHP= , t tFW

LPSSLP=

– The exhaust gas temperature is higher than high and low pressure steam saturation temperature

t t Texh SSHP

3 = + ∆ , t t Texh SSLP

5 = + ∆ where ∆T K=10– The high and low pressure superheated steam

temperature is lower than exhaust temperature

t t T t t TSHHP

exh SHLP

exh= − = −1 3∆ ∆

where ∆T K=12– The temperature at the end of waste heat boiler

(assuming3.5%sulphurcontentinfueloil)shouldbe higher than or equal to

t C T Cexh4 145 160≥ ° + = °∆

where ∆T K=15– The temperature of water in the feed water tank is

constant and equals to tFW=70°C.Byapplying thefirst lawof thermodynamics and

assuming the power of feeding pumps to be negligible andefficiencyofexhaustboilerηB=1,thehighpressuresteammassfluxpossibletobegeneratedintheexhaustgas boiler was determined as follows:

��

mm c t t

i iHP

exh p t

t

exh exh

SHHP

FW

exh

=⋅ ⋅ −( )

+

−

+

3

1

1 3

��m c t t

i ikgs

air p t

t

air air

SHHP

FW

air⋅ ⋅ −( )

−

2

1

1 2

(7)

.

.

.

.

.

��

mm c t t

i iHP

exh p t

t

exh exh

SHHP

FW

exh

=⋅ ⋅ −( )

+

−

+

3

1

1 3

��m c t t

i ikgs

air p t

t

air air

SHHP

FW

air⋅ ⋅ −( )

−

2

1

1 2


The exhaust gas temperature was calculated behind the steam super heater using the following equation:

t tm i i

m cCexh exh

HP SHHP

SSLP

exh p t

t

exh

2 1

2

1= −

⋅ −( )⋅

°[ ]�

�(8)

The temperature of exhaust gases as it passes the HPevaporatorsectionwascalculatedasfollows:

t tm i i

m cCexh exh

HP SSHP

FWHP

exh p t

t

exh

3 22

3

2= −

⋅ −( )⋅

°�

�[ ] (9)

Under the abovementioned assumption on theequality ofmass fluxes of produced steam andwater,the temperature of the charged air of the engine was calculated behind the HP water heater as follows:

t tm c t t

m cCair air

FWHP

p t

t

FW FWHP

air p t

t

FW

air

2 1

22

1

2

1= −

⋅ ⋅ −( )⋅

°�

�[ ].(10)

Low pressure section parameters were calculated in asimilarmannerusingequations(7)–(10).

In the proposedWHRS configuration, the steamturbine is drivenby theproduced superheated steam,and assuming the pressure and dryness fraction to be x =0.86at theendof theexpansionprocess, thecorresponding enthalpy in the condenser icon, wasestimated.Theeffectivepowerofa two- stagesteamturbine PST was determined by means of the following relation:

P m i i m

i i

ST SHHP

SHHP

con SHLP

SHLP

con I ST M ST

= ⋅ −( ) + ⋅

⋅ −( ) ⋅ ⋅

[

]

� �

η η [ ]kW(11)

Finally, the electric power PSTel that is produced

by the ship’s synchronous generator driven by steamturbine was calculated using the following:

P P kWST ST Gel= ⋅ [ ]η (12)

Duetotheassumptionoftheequalrotationalspeedoftheshafts,nST = nG,onlythesynchronousgeneratorefficiencywas taken into account as nG= 0.95.

.

(13)

EEDIP b C P b C

j e ME j f ME j F ME j k e AE k f AE k=

⋅ ⋅( ) + ⋅ ⋅= =∑ ∑1

2

1

2FF AE k j STel j k f AE k F AE k

DWT s j

P b C

m v f

( ) − ( ) ⋅( ){ }⋅ ⋅

= =∑ ∑1

2

1

2

RRoRo cRoPaxf⋅

EEDIP b C P b C


⋅ ⋅( ) + ⋅ ⋅= =∑ ∑1

2

1


DWT s j

P b C

m v f

( ) − ( ) ⋅( ){ }⋅ ⋅

= =∑ ∑1

2

1

2

RRoRo cRoPaxf⋅

EEDIP b C P b C


⋅ ⋅( ) + ⋅ ⋅= =∑ ∑1

2

1


DWT s j

P b C

m v f

( ) − ( ) ⋅( ){ }⋅ ⋅

= =∑ ∑1

2

1

2

RRoRo cRoPaxf⋅

4. Energy Efficiency Design Index calculation for different types of marine fuel

The general mathematical relationship given byIMO for EEDI determination together with symbolspresentedinthemathematicalmodelareasfollows[7]:

Specificfuelconsumptionofauxiliaryengines,attheinitialdesignstage,wasassumedaccordingto[2]asthatforhalfofthenominalload.Thetypeofauxiliaryengines was assumed to be the same as that of the main enginesandspecificfuelconsumptionandheatwerereadfrom[6].Duetousingdualfueldieselenginesasboththemain and auxiliary engines, specific fuel consumptioninrelation(14)forrunningonLNGwasdeterminedasa specific natural gas consumption and that of a pilotdoseofoil according to [7].Thevaluedenotedas Cf was defined as a dimensionless conversion coefficientbetweenfuelconsumptionandcarbondioxideemission.The coefficient reaches different values depending onthe kind of applied fuel, i.e. for natural gas –CfNG = = 2,750gCO2 /g,andfortheheavyfuel–CfHFO = 3,114gCO2 /g,reachingamaximumvalueforthedistilledlow-sulphurvalue–CfMDO = 3,206gCO2 /g [7].

In relation (14), fjRoRo denotes a correction coefficient,takingintoaccounttheconstructionqualitiesofthevessel,describedbytheequationbelow:

f Fn LB

BT

LjRoRo P

PP PP= ⋅

⋅

⋅

∇

α

β γ δ

1 3/

−−1

(14)

Determination of the correction coefficient inrespecttodeadweightwasbasedonrelation(16),andregisteredtonnagewasestimatedusingexemplaryunit.

fm GT

cRoPaxDWT=

( )

−/

,

,

0 25

0 8

(15)

EEDIP b C P b C


⋅ ⋅( ) + ⋅ ⋅= =∑ ∑1

2

1


DWT s j

P b C

m v f

( ) − ( ) ⋅( ){ }⋅ ⋅

= =∑ ∑1

2

1

2

RRoRo cRoPaxf⋅


EEDIcalculationswereperformedforthreetypesof applied fuel:– Using liquefied natural gas (LNG) for running

dual fuel engines of the main power plant and the auxiliary engines applying the presented waste heat recoverysystem;

– Usingheavyfueloil(HFO)withasulphurcontentover3.5%ofthefuelmasswithchemicaltreatment

Fig. 3. Graphic representation of calculation procedures in a ship power plant

of the exhaust to reduce the amount of sulphur oxides and using waste heat from the main power engines;and,

– Usingmarineoilwithasulphurcontentbelow0.1%ofthefuelmassapplyingtheSCRreactortoobtainsatisfactory emission of nitrogen oxides from the consideredpowersystem.


5. Presentation of results

The calculatedWHRSparameters using relations(7)-(12) for the HP and the LP sections of the boiler

andforengine’sloadrange,PPSR

MCR

= 0 75. ,arepresented

Table 2. Waste Heat Recovery System parameter calculation results

Fuel typePPSR

MCRPSR texh1 texh2 tair1 tair2 ΣQexh

Qair Σ QrecmS WLP/

mS WHP/ PST PSTel ηrec

[–] [–] [MW] [°C] [°C] [°C] [°C] [MW] [MW] [MW] [kg/s] [kg/s] [MW] [MW] [–]HFO 0.75 6.30 276 272 207 184 1.86 0.34 2.21 0.182 0.651 0.44 0.43 0.193LNG 0.75 6.30 381 272 162 117 2.63 0.46 3.09 0.185 0.916 0.71 0.70 0.228


in Table 2. The presented values correspond to heatrecoveryfromoneofthetwomainengines.

Figure 4 presents the calculated total effectivepower and the power for the low and high pressure of theutilizationsteamturbine.

Fig. 4. Total effective power and effective power of low and high pressure utilization steam turbine operating in the waste heat recovery system


Fig. 5. A graph of EEDI limiting values determined for the studied optionsSource:Ownelaboration.

Figure 4 presents the calculated total effectivepower and the power for the low and high pressure of theutilizationsteamturbine.

The graph of limiting values of EEDI togetherwiththepointsdeterminedfromrelation(13)forthreeoptionsoftheusedfuelispresentedinFig5.


Conclusions

In the casewhen the engine is run onHFOwithasulphurcontentover3.5%,onthebasisof[3],itwasassumedthattheflowofexhaustgaseswouldbedirectedtowardsthede-sulphuringsystem.Thissolutiondoesnoteliminate the risk of the occurrence of low temperature corrosion,whichwouldcauseadropofenthalpyoftheburning products from the main engines, but wouldreachahighervalue fornaturalgas.TheconsequenceoftheabovewasalsoobservedinFig.5.Thedescribedoptionmeets only the regulation forSOx emissions in thestudiedECAregion.

UsinganSCRreactorintheexhaustsystemrequiresan appropriate temperature of exhaust for carrying out an effective process of their purification from NOx.That,according to [3],makes theapplicationofwasteheatrecoverysystemimpossibleinsuchaconfiguration.Applyingthelow-sulphurfuel,MGO,togetherwiththeSCRreactorgivesoffexpectedemissionsofSOx and NOx, with the values of the energy efficiency designcoefficientabovetheacceptablelevel(Fig.6).

Usingdual-fuelmainandauxiliaryenginesrunonnatural gas togetherwith theWHRS (Fig 3) gave offsatisfactoryemissionsofSOx,NOx, and the acceptable valueofEEDIforthestudiedareaofshipoperation.

Bibliography

1. AdamkiewiczA., Przybyła M.: Determination ofHull Parameters and Total Resistance of Ro-PaxVessel at the Preliminary Design Stage. SGEMConference,Bulgaria2017.

2. Ancic I., SestanA.,VladimirN.:Modification oftheEEDIforRo-RoPassengerShips. UniversityofZagreb,Croatia2016.

3. Changhee L.: Characteristics on the Waste HeatRecovery of the Economizer Applied with andwithout SCR Systems in a Propulsion DieselEngine. JournalofHeatandMassTransfer.2016,13,361–377.

4. Dang J., Ligteljn J.T., van den BoomH.J.J.: TheWageningen C- and D-Series Propellers. 12thInternationalConferenceonFastSeaTransportation,Amsterdam2013.

5. HoltropJ.,MennenG.G.J.,AnApproximatePowerPrediction Method, International ShipbuildingProgress,Netherland,1982.

6. MAN Diesel & Turbo: MAN 51/60DF, ProjectGuide – Marine, Four-stroke dual fuel enginescompliantwithIMOTierIII. Augsburg,2017.

7. Polski Rejestr Statków: Guidelines of EnergyEfficiencyofShips. Publicationno.103/P,Poland2016.

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A CONCEPT OF A MARINE POWER PLANT SUPPLIED WITH …