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Such cases may apply or engines such

helping to keep the economiser cleaner with IN SERVICE both in a Siemens shat motor/generator to as the Wrtsil RT-fex82C, RT-fex82T andless soot deposition. assist in ship propulsion, and in shipboard RT-fex84T-D types.

The rst installation o this new high-eciency services. A portion o the steam rom the The waste heat recovery plant is similar to

CASE STUDY WHR plant entered service in the 7500 exhaust economiser is utilised in shipboard the higher-output described above but energyThe economic benets o the high-eciency TEU container ship Gudrun Mrsk o the heating services. is usually only recovered rom an exhaust-

WHR system can be illustrated by the case A.P. Moller-Maersk Group in June 2005. It The calculated output o the turbogenerator gas economiser to generate steam or a

o a container ship powered by a 12-cylinder successully conrmed the benets o the new set is based upon ISO standard reerence turbine-driven generator. I necessary, heat is

Wrtsil RT-fex96C engine. In the case, the WHR plant concept. During sea trials and in conditions which include an ambient also recovered rom the engines scavenge

engine would operate at an average o 85% operation, the perormance o the WHR plant temperature o 25C. During the sea trials o air and jacket cooling water or eedwater

RT-fex engines has the additional benet o HIGH-EFFICIENCY WHR to the ships main switchboard and employed

HIGH-EFFICIENCY WHR: CASE STUDYBasis ship:

Main engine: Wrtsil 12RT-fex96C

CMCR power,kW: 80,080

Annual operating hours: 6500

Average engine load,%: 85

Total electrical load,kW: 5350

Auxiliary engines,kWe: 4 x 3000

Bunker uel price,US$/tonne: 250

Cylinder lubricating oil price,US$/tonne: 1500

Annual engine operating costs basis ship with WHR

Fuel costs,US$: 18,449,000 16,359,000

Maintenance costs,US$: 486,000 333,000

Lubricating oil costs,US$: 602,000 559,000

Total,US$: 19,537,000 17,287,000

at US$ 400/tonne uel: 3,482,000Annual savings,US$ at US$ 250/tonne uel: 2,250,000

Investment cost,US$ 9,500,000

PAYBACK TIME LESS THAN 5 YEARS

The turbogeneratorset o the GudrunMr sk-class containerships. (Photo:Peter BrotherhoodLtd)

Schematico a simpliedhigh-eciency WHR plant as might be employedwith a Wrtsil 7RT-fex84T-D

engine ora large tankerwith the turbogeneratorsupplyingall ships service electricity while the shipis at sea.

G

G

G

Single-pressureexhaust gas

economiser

Single-pressuresteam turbine

Turbochargers

Main engine

Ship service steam

Ship service electricity

Aux. engines

load or about 6500 hours a year on bunkers exceeded expectations. the rst ship, this perormance was exceeded heating. The economiser also operates at a

costing US$ 250/tonne, with an average total Similar WHR plants are also now in normal as such output was already achieved at the single steam pressure. However the quantity

electrical load o 5350kW, including reeer operation in the complete class o six 7500 TEU ambient temperature o 14C. o energy recovered rom the exhaust gases is

containers. The annual operating costs or sister ships. The WHR plant or these vessels The vessels are also each equipped increased by adapting the engine to the lower

the main and auxiliary engines, including uel, was developed in a joint eort headed and with three eight-cylinder Wrtsil 32 diesel air intake temperatures that are available

maintenance and lubricating oil, would be integrated by Odense Steel Shipyard Ltd in generating sets having a combined electrical by drawing intake air rom outside the ship

US$ 19.54 million without a WHR plant and cooperation with Wrtsil,Siemens AG,Peter output o 11.2 MWe. The high-eciency WHR (ambient air) instead o rom the ships engine

US$ 17.29 million with a high-eciency WHR Brotherhood Ltd and Aalborg Industries Ltd. plant enables each ship to be tted with one room. The engine turbochargers are matched

plant. The ships are each propelled by a Wrtsil ewer diesel generating sets than it would or the lower air intake temperatures thereby

There would thus be annual savings o US$ 12RT-fex96C low-speed common-rail engine otherwise have. increasing the exhaust energy.

2.25 million. I the bunker price increased with a maximum continuous power output The high-eciency WHR concept has been As todays high-eciency turbochargers

rom US$ 250 to US$ 400/tonne, then the o 68,640 kW at 102 rpm. Exhaust gases taken a step urther in the new 11,000 TEU have surplus capacity at the engines upper

annual savings would increase to about US$ pass through an dual-pressure exhaust- container ships o the A.P. Moller-Maersk Group. load range when matched or ambient air

3.48 million. gas economiser rom Aalborg Industries The rst o this class, the Emma Mrsk, was intake, less exhaust gas fow is necessary or

The complete high-eciency WHR to generate superheated steam which is delivered in September 2006 rom Odense the turbochargers. Thus about 89% o the

plant and its installation would call or an utilised in a 6 MWe turbogenerator set rom Steel Shipyard. She has since been joined by a engines exhaust gas fow can bypass the

investment cost o about US$ 9.5 million. This Peter Brotherhood. The turbogenerator sets number o sister ships. turbochargers to give a urther increase in

would thus have an expected payback time o incorporate both a multi-stage dual-pressure The ships are each powered by a 14-cylinder recoverable exhaust gas energy.

less than ve years. steam turbine and an exhaust-gas power Wrtsil RT-fex96C common-rail engine. The overall result o this concept is that the

turbine. The generated electricity is supplied These are the worlds rst 14-cylinder in-line quantity o energy recoverable in an exhaust-

engines and also the worlds most powerul gas economiser is increased without aecting

electronically-controlled engines with an MCR the air fow through the engine. There is

power o 80,080 kW each at 102 rpm. This thus no increase in the thermal loading o

propulsion power is augmented by two shat the engine and there is no adverse eect on

motors in each vessel. engine reliability.

The main engines are each associated with For example, a high-eciency WHR plant

a high-eciency WHR plant incorporating a associated with a 29,400 kW seven-cylinder year, with corresponding savings in all types o in uel consumption, and thereby reducing CO2

turbogenerator set having a nominal output o Wrtsil RT-fex84T-D engine in a VLCC (very air emissions, especially CO2. emissions by engine developments alone. Yet

8.5 MWe. This operates in conjunction with each large crude oil carrier) could deliver 1645 major improvements can be gained by using

ships ve diesel generating sets that have a kWe at engine ull load under ISO conditions CONCLUSION proven technology and hardware through

combined output o 20.7 MWe. with 9% exhaust gas bypass using a single- The high-eciency waste heat recovery applying the high-eciency WHR plant. It is pressure steam system. As such a vessel plant concept is attracting much attention thus a practical path orward.

SOLELY FOR SHIPS would need only 10001100 kWe or ship rom shipowners interested in saving uel The combination o a Wrtsil RT-fex engine SERVICE ELECTRICITY services while at sea, the tanker could operate costs and reducing CO

2emissions. It must be with high-eciency WHR plant is a major

A simplied version o the high-eciency WHR without running its auxiliary engines while remembered that modern large, low-speed contribution to reducing the environmental

system described above is oered or ships that at sea under a wide range o ship speeds. It engines are very highly developed and there is impact o shipping.

require the recovered energy to be only sucient would save more than 1400 tonnes o uel a little potential or achieving signicant savings

to cover all shipboard electricity demand while

the ship is at sea.

This avoids the running o auxiliary engines

while at sea with the corresponding savings in

uel, maintenance and spare parts costs, as well

as reductions in exhaust gas emissions.

WRTSIL is aregisteredtrademark. Copyright2007 WrtsilCorporation.

WARTSILA.COM

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In any case, the resulting payback time

would depend upon the installation design

and bunker uel prices but should in general

be about ve years which is commercially

attractive. Increasing uel prices make such

plants more attractive. A WHR plant thus leads

to considerable nancial benets over a ships

lie.

The new concept developed by Wrtsil

ollows the well-established arrangement o

passing the exhaust gases o the ships main

engine through an exhaust-gas economiser to

generate steam or a turbine-driven generator.

drum. The economiser outlet temperature

is not less then 160C to avoid sulphur

corrosion in the economiser outlet. Saturated

steam is drawn rom the HP st eam drum or

ship service heating.

In a rst stage, the eed water is heated

rom the engines jacket cooling water to a

temperature o 85C. Only the eed water or

the high-pressure section is urther heated

in the engines scavenge air cooler to about

150C to 170C. The scavenge air cooler is

designed such that the eed water heating

section can run dry with the total scavenge

heat dissipated in the scavenge air cooler.

STEAM TURBINE

A dual-pressure steam turbine running

Fuel input 100%

Shaft power 49.3%

Exhaust gas

25.4%

vera e iciency .

Scavenge air

cooling water

14.1%

Jacket water

6.3%

Lubricating oil

4.3%

Radiation

0.6%

Fuel input 100%

(171 g/kWh)

Shaft power 49.0%

Exhaust gas

12.6%

Scavenge air

cooling water

12.9%

Jacket water

6.2%

Lubricating oil

4.2%

Radiation

0.6%

(172 g/kWh)

v era e iciency . , ain = .

Electrical power 5.9%

Condenser

8.6%

Evenwith the high,50%eciency o modernlow-speedengines there is still50% o uelinput energy not

beingput to productive use. The possibilities are illustratedby this comparison o Sankey diagrams or

Wrtsil 12RT-fex96C engines without heat recovery (let)and withthe high-eciency waste heat recovery

plant (right)showing inthis case an11.4% gainin overalleciency withWHR.

35C

45C

35C

Let:Engine roomair suction.Right: Ambient airsuction rom

outside the ships engine room.

0

2000

4000

6000

8000

50 60 70 80 90 100Engine load, %

Tur ogeneraor oupu, e

Power turbine

Steam turbine

Combined output

10000

Energy recovered(kWe) by the turbogeneratorset in a high-eciency WHR plant ona 12RT-fex96C engine

withDelta Tuning(or improvedpart-load uelsavings) andambient suction.

M

G

G

G

G

Main engine

Exhaust gas

economiser Ship service steam

Ship service power

Aux. engines

Exhaustturbine

Motor/generator

T urbo c h arg ers

G

Steamturbine

Schematico a high-eciency waste heat recovery plant typicalor large containerships withthe

turbogeneratorsupplying bothassisted propulsionand ships service power.The shat motorcan also

serve as a shat generatoror addedfexibility inoperation.

LPevaporator

LPsuperheater

HPevaporator

HPsuperheater

Steamturbine

166C

12 bar

36

9.0 bar(g) / 260C

3.5 bar(g) / 190C

3.8 bar(g)150.3C

HPserviceste

9.5 bar(g)182C

G

Exhaustturbine

Condenser

HP

LP

Process diagramor the high-eciency waste heat recovery plant.

rematched to return the thermal load o the

engine back down to what prevails or the

intake temperature at 45C. When considering

such a tuning to reach an increased exhaust

gas temperature, it is important that the

thermal load o the adapted engine is no

greater than that o the usual engine so as not

to jeopardise engine reliability.

Even with a certain quantity o exhaust

gas branched o or the power turbine

and thereore not then available or the

turbocharger, the thermal loading o

the engine remains the same as or the

Modern, high-eciency turbochargers also

have a small surplus in eciency capability

in the upper load range. This allows a certain

exhaust gas fow to be branched o beore

the turbocharger to drive a gas turbine, or

as it is called in this application an exhaust

power turbine. With normal engine tuning it is

not worth taking advantage o this possibility.

However, the rematched turbochargers

or ambient suction allow even more

exhaust gas to be branched o under ISO

conditions compared with the conventional

tuning with maximum 45C suction air

temperature. Thereore, the rematched engine

supercharging system gives an increased

exhaust gas energy and allows a good amount

o exhaust gas to be branched o beore the

However, the quantity o energy recovered conventional engine. This is possible because turbocharger thereby allowing a worthwhile at about 6750 rev/min is used. The high-

rom the exhaust gases is maximised by the special turbocharger matching in heat recovery potential to be achieved. The change in engine suction also has alternator system. pressure side works at about 8.09.0 bar(g)

adapting the engine to the lower air intake combination with the exhaust power turbine Heat is also recovered rom the engines the benet o reducing the electrical power In the rematched system, about 10% inlet pressure. This requires three turbine

temperatures that are available by drawing allows ull utilisation o the available eciency scavenge air and jacket cooling water or required or engine-room ventilation with o the engines exhaust gas fow can be stages at a condenser pressure o 0.065

intake air rom outside the ship (ambient air) o the turbocharger, and also because o the eedwater heating. The scavenge air coolers consequent uel cost savings. In the case o employed to drive an exhaust power turbine bar. With an economiser outlet temperature

instead o rom the ships engine room. ambient suction tuning. are designed in such a way that the boiler a container ship with a 12RT-fex96C engine, which is incorporated in the turbogenerator o 160C, a low-pressure steam pressure at

Usually marine engines are designed or This adapted tuning, however, incurs eed water can be heated close to the the total power or ventilation ans may be cut set. the turbine inlet o 3.03.5 bar(g) pressure is

intake temperatures o up to 45C or tropical a penalty in a slightly increased uel evaporation temperature. rom 400 to 200 kW. considered. This requires six turbine stages at

conditions with turbochargers drawing intake consumption at ISO reerence conditions. The overall result o the new concept is ECONOMISER a condenser pressure o 0.065 bar. A speed-

air rom the engine room. I instead the intake But the gain in recovered energy more then that the quantity o energy recoverable in an WHR PLANT CONFIGURATION The exhaust gas economiser consists o a reduction gear between steam turbine and air is drawn rom outside the engine room compensates or the loss in eciency rom exhaust-gas economiser and in the exhaust The high-eciency WHR plant consists o a high-pressure part with HP evaporator and generator reduces the turbine speed to 1800

through an air intake duct, the maximum the higher uel consumption. The engine power turbine is increased without aecting dual-pressure economiser, a multiple-stage superheating section and a low-pressure part rev/min generator speed.

intake temperature can be assumed to be no needs to be equipped with an air waste gate the air fow through the engine. There is dual-pressure steam turbine, an exhaust with LP evaporator and superheating section.

more than 35C. to ensure that the maximum cylinder pressure thus no increase in the thermal loading o power turbine, an alternator driven by both the The pressure in the high-pressure steam EXHAUST POWER TURBINE

In such a case, the lower air intake stays within permissible limits at very low the engine and there is no adverse eect on steam turbine and the power turbine, a eed drum is at about 9.5 bar(g) pressure, and The power turbine uses a part o the exhaust

temperature allows the turbochargers to be ambient temperature. engine reliability. water pre-heating system and a shat motor/ about 3.8 bar(g) in the low-pressure steam gas stream (about 10%) rom the diesel