Whru Installation

Summary ...........................................................................
..........................5
Introduction ......................................................................
...........................5
Description of the Waste Heat Recovery
Systems .........................................6
Power concept and
arrangement ............................................................6
Power turbine and generator
(PTG) .........................................................7
Steam turbine and generator
(STG) .........................................................7
Steam turbine, power turbine, and generator (ST-
PT) ...............................8
Main engine and WHRS system
control .................................................10
Installation
aspects ...........................................................................
....11
Power turbine WHRS
solution ...............................................................12
Steam turbine WHRS
solution ...............................................................12
Full steam and power turbine WHRS
solution ........................................12
Main Engine Performance
Data ..................................................................15
Main engine tuning for
WHRS ...............................................................15
Exhaust gas bypass with power
turbine .................................................15
Exhaust gas bypass without power
turbine ............................................15
Exhaust gas boiler and steam
systems ..................................................16
Single-pressure steam
system ..............................................................16
Dual-pressure steam
system ......................................................................17
Steam and water diagram – ME WHRS element ....................................18
Main engine steam production power (SPP) guarantee ..........................19
Obtainable Electric Power of the
WHRS ......................................................20
Power and steam turbine generator output – dual pressure ...................20
Payback time for waste heat recovery
system .......................................22
Emission Effects of using
WHRS .................................................................25
WHRS Effect on Ship’s
EEDI .......................................................................26
Conclusion ........................................................................
.........................28
Reference .........................................................................
.........................28
Nomenclature /
abbreviations .....................................................................
29
The increasing interest in emission re-
duction, ship operating costs reduction
and the newly adapted IMO EEDI rules
calls for measures that ensure optimal
utilisation of the fuel used for main en-
gines on board ships.
Main engine exhaust gas energy is by

far the most attractive among the waste
heat sources of a ship because of the
heat flow and temperature. It is possi-
ble to generate an electrical output of
up to 11% of the main engine power
by utilising this exhaust gas energy in
a waste heat recovery system compris-
ing both steam and power turbines,
and combined with utilising scavenge
air energy for exhaust boiler feed-water
heating.
This paper describes the technology

behind waste heat recovery and the
potential for ship-owners to lower fuel
costs, cut emissions, and the effect on
the EEDI of the ship.
Introduction
Following the trend of a required higher
overall ship efficiency since the first oil
crisis in 1973, the efficiency of main en-
gines has increased, and today the fuel
energy efficiency is about 50%. This
high efficiency has, among other things,
led to low SFOC values, but also a cor-
respondingly lower exhaust gas tem-
perature after the turbochargers.
Even though a main engine fuel energy

efficiency of 50% is relatively high, the
primary objective for the ship-owner is
still to lower ship operational costs fur-
ther, as the total fuel consumption of
the ship is still the main target. This may
lead to a further reduction of CO2 emis-
sions – a task, which is getting even

more important with the new IMO EEDI
rules in place from 2013.
The primary source of waste heat of a

main engine is the exhaust gas heat dis-
sipation, which accounts for about half
of the total waste heat, i.e. about 25%
of the total fuel energy. In the standard
high-efficiency engine version, the ex-
haust gas temperature is relatively low
after the turbocharger, and just high
enough for producing the necessary
steam for the heating purposes of the
ship by means of a standard exhaust
gas fired boiler of the smoke tube de-
sign.
However, the MAN B&W two-stroke

ME main engine tuned for WHRS will
increase the possibilities of producing
electricity from the exhaust gas. The
result will be an improvement in total ef-
ficiency but a slight reduction of the ef-
ficiency of the main engine will be seen.
Fig.1 shows a comparison of engine

heat balances, with and without WHRS.
The figure shows that for the engine in
combination with WHRS the total effi-
ciency will increase to about 55%.
The IMO EEDI formula allows for con-

sidering adding WHRS into the ship,
analyse EEDI effects and EEDI settings.
As an even lower CO2 emission level
can be achieved by installing a waste
heat recovery system the EEDI, which
is a measure for CO2 emissions, will
also be lowered.

Whru Installation

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Summary ...........................................................................

Main engine exhaust gas energy is by

This paper describes the technology

Even though a main engine fuel energy

sions – a task, which is getting even

The primary source of waste heat of a

However, the MAN B&W two-stroke

Fig.1 shows a comparison of engine

The IMO EEDI formula allows for con-

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