Technical field
[0001] The invention relates to a marine boiler for transferring heat from exhaust gas to
a medium onboard a ship, and its design. The invention also relates to a method of
operating such a marine boiler.
Background art
[0002] Boilers are well-known and used in many different heat exchange applications. For
example, a marine boiler may be arranged on a ship after an exhaust gas source in
the form of one or more main engines for propelling the ship, and possibly one or
more auxiliary engines, to recover heat from exhaust gas produced by the engines.
Such a marine boiler is often referred to as a heat recovery marine boiler. In such
a marine boiler, a medium, typically water, conveyed through the marine boiler is
heated by means of heat from the engine exhaust gas conveyed through the marine boiler
whereby typically hot water and steam is produced. Hot water and steam leaving the
marine boiler is used for different purposes onboard the ship.
[0003] Out on the open sea where the ship may move at a relatively high speed and the main
engines may be operated at a relatively high engine load, hot water and steam in amounts
sufficient to fulfill the needs onboard the ship may be produced by means of the exhaust
gas generated by the engines. When the ship moves at relatively low speed or does
not move at all, which may be the case when the ship is at a port or in a sensitive
area, the main engines are typically operated at a relatively low engine load or not
at all. Then, insufficient amounts of hot water and steam may be produced by means
of the exhaust gas generated by the engines. To secure sufficient production of hot
water and steam also when the main engines are operated at low or zero engine load,
the marine boiler may comprise a burner arranged to be fed with, and burn, oil and/or
gas to generate combustion gas for production of hot water and steam. A problem is
that the exhaust gas from the engines as well as the combustion gas from the burner
typically contain pollutions. Pollutions are harmful to the environment and especially
undesirable at ports and in sensitive areas.
Summary
[0004] An object of the present invention is to provide a marine boiler and a method of
operating a marine boiler that at least partly solves the problem above. The basic
concept of the invention is to provide the marine boiler with external energy for
production of hot water and steam. The marine boiler and the method for achieving
the object above is defined in the appended claims and discussed below.
[0005] A marine boiler according to the invention is arranged for transferring heat from
exhaust gas or flue gas or combustion gas to a medium onboard a ship. The marine boiler
comprises an exhaust gas inlet for receiving exhaust gas from a first exhaust gas
source, a first exhaust gas outlet for discharging exhaust gas from said first exhaust
gas source, and means for conveying exhaust gas from the first exhaust gas source
from said exhaust gas inlet to said first exhaust gas outlet. The marine boiler further
comprises a medium inlet for receiving the medium, a medium outlet for discharging
the medium, and means for conveying the medium from said medium inlet to said medium
outlet. Also, the marine boiler comprises a circumferential wall inside or within
which exhaust gas from the first exhaust gas source and the medium are arranged to
be conveyed. The marine boiler is characterized in that it further comprises an electric
heater for heating said medium by means of electricity supplied from a power source.
The power source is separate from said first exhaust gas source.
[0006] Thus, according to the present invention, a certain medium volume is heated by the
exhaust gas from the first exhaust gas source or the electric heater or by a combination
thereof.
[0007] The medium to be heated can be any suitable medium, for example water. The medium
may, or may not, change phases, such as go from liquid to gaseous phase, partly or
completely, on its way through the marine boiler. For example, the medium inlet may
be arranged to receive the medium at least partly in liquid phase, e.g. in the form
of water, while the medium outlet may be arranged to discharge the medium at least
partly in gaseous phase, e.g. in the form of steam.
[0008] Herein, the expression "conveying from an inlet to an outlet" and similar means "conveying
in a direction from an inlet to an outlet" and not necessarily all the way from the
inlet and all the way to the outlet. Thus, said means for conveying exhaust gas and
said means for conveying the medium may, but need not, extend all the way between
the respective inlets and outlets.
[0009] The circumferential wall can have any suitable shape, such as the shape of a tube
with circular, oval, polygonal, rectangular, etc. , cross-section. The circumferential
wall may further have any suitable design, such as be solid or hollow, and/or have
a uniform or non-uniform thickness. As an example, the circumferential wall may be
a so-called panel wall comprising a number of parallel tubes connected by means of
solid wall portions. A cooling medium may be fed through these tubes for cooling exhaust
gas conveyed through the marine boiler.
[0010] The components of the marine boiler could be made of any suitable material, for example
carbon steel, stainless steel or aluminum.
[0011] The electric heater may have any suitable design. As an example, the electric heater
may be an electrode heater. The marine boiler may comprise one or more additional
electric heaters for heating said medium, possibly by means of electricity supplied
from said power source.
[0012] The power source for supplying electricity to the electric heater may be of any suitable
design. As an example, the power source may be arranged to supply electricity produced
from any suitable fuel, solar power, wind power, water power, nuclear power, or any
combination thereof.
[0013] In that the power source is separate from the first exhaust gas source, the electric
heater may be supplied with electricity even when the first exhaust gas source is
not operating so as to enable sufficient production of steam and hot water. The power
source may be a "clean" power source such that operation of the electric heater, which
typically takes place when the ship is at a harbor or in a sensitive area, cause release
of little or no pollutions.
[0014] The power source may be separate from any exhaust gas source, such as any main or
auxiliary engine, onboard the ship. Accordingly, the power source may discharge no
exhaust gas.
[0015] The power source for supplying the electric heater with electricity could be arranged
onboard the ship. However, according to one embodiment of the invention said power
source is separate from the ship, for example onshore. Such an embodiment enables
minimizing of any pollutions caused by operation of the electric heater in the immediate
vicinity of the ship.
[0016] The first exhaust gas source may be of any suitable type, such as an auxiliary engine,
a burner or a turbine. However, according to one embodiment, the first exhaust gas
source comprises an engine, for example a diesel or a dual fuel main engine, for propelling
the ship. Such an embodiment may enable automatic generation of steam and hot water
when the ship is propelled.
[0017] The marine boiler may be so constructed that said means for conveying exhaust gas
from said exhaust gas inlet to said first exhaust gas outlet comprise a first bundle
of tubes, and said means for conveying the medium from said medium inlet to said medium
outlet comprise said circumferential wall of the marine boiler enclosing said first
bundle of tubes.
[0018] The tubes and the circumferential wall could be made of the same material to get
essentially the same temperature during operation of the marine boiler, which may
enable relatively low thermal stresses in the marine boiler.
[0019] The tubes may have any suitable design, such as be straight, curved or coil- or helix-shaped
and have a circular or oval or polygonal cross section, and the tubes may be similar
or different from each other. The tubes may be provided with surface-enlarging elements,
such as spiral fins, plate fins, or fins of any other suitable design.
[0020] The number of tubes may be two or more and they may extend along, and possibly also
parallel to, each other. A longitudinal center axis of the electric heater may extend
parallel or perpendicular to the tubes.
[0021] According to this embodiment, exhaust gas is fed through the marine boiler in tubes
surrounded by the medium to be heated which is enclosed by said circumferential wall
of the marine boiler, and heat exchange between exhaust gas and the medium is taking
place through walls of the tubes. Such a marine boiler may be referred to as a smoke
tube marine boiler.
[0022] Instead of being designed as a smoke tube marine boiler, the marine boiler may be
so constructed that said means for conveying the medium from said medium inlet to
said medium outlet comprise one or more tubes. Further, said means for conveying exhaust
gas from said exhaust gas inlet to said first exhaust gas outlet may comprise said
circumferential wall of the marine boiler enclosing said one or more tubes.
[0023] Also these one or more tubes may have any suitable design, such as be straight, curved
or coil- or helix-shaped and have a circular or oval or polygonal cross section, be
similar or different from each other, extend along, and possibly also parallel to
each other, and be provided with surface-enlarging elements of any suitable design.
Also here, a longitudinal center axis of the electric heater may extend parallel or
perpendicular to the tubes.
[0024] According to this embodiment, the medium to be heated is fed through the marine boiler
in tubes surrounded by exhaust gas from the first exhaust gas source, which exhaust
gas is enclosed by said circumferential wall of the marine boiler, and heat exchange
between exhaust gas and the medium is taking place through walls of the tubes. If
the medium is water, such a marine boiler may be referred to as a water tube marine
boiler.
[0025] The design of the marine boiler may be such that the electric heater is arranged
inside, or enclosed by, said circumferential wall. This design may enable a compact
and component effective marine boiler.
[0026] Alternatively, the design of the marine boiler may be such that the electric heater
is arranged in a container arranged outside said circumferential wall. Further, the
container may be in communication with said means for conveying the medium from said
medium inlet to said medium outlet to enable transfer of said medium between the container
and said means for conveying the medium from said medium inlet to said medium outlet.
As an example, the container and said means for conveying the medium from said medium
inlet to said medium outlet may communicate by means of one or more pipes extending
between the container and said means for conveying the medium from said medium inlet
to said medium outlet, for example one pipe for feeding the medium from said means
to the container and another pipe for feeding the medium from the container to said
means. In case the marine boiler comprises more than one electric heater, they may
be arranged in a common container or arranged in one container each. This plurality
of containers may be connected in parallel or in series.
[0027] As used herein, "communicating" and similar means "communicating directly or indirectly".
[0028] The inventive method of operating a marine boiler to transfer heat from exhaust gas
to a medium onboard a ship, comprises the step of conveying exhaust gas from a first
exhaust gas source from an exhaust gas inlet to a first exhaust gas outlet of the
marine boiler. The inventive method further comprises conveying the medium from a
medium inlet to a medium outlet of the marine boiler. The marine boiler comprises
a circumferential wall inside which exhaust gas from the first exhaust gas source
and the medium are arranged to be conveyed. The method is characterized in further
comprising the steps of supplying an electric heater with electricity from a power
source, which power source is separate from said first exhaust gas source, and heating
said medium by means of said electric heater.
[0029] The electric heater may be supplied with electricity when the first exhaust gas source
is operating, possibly at only a low load, or only when the first exhaust gas source
is idle, i.e. not operating.
[0030] The method may be such that said power source is provided separate from any exhaust
gas source onboard the ship.
[0031] The method may be such that said power source is provided separate from the ship,
for example onshore.
[0032] The method may be such that an engine for propelling the ship is provided as said
first exhaust gas source.
[0033] The electric heater may be provided inside said circumferential wall.
[0034] Alternatively, the electric heater may be provided in a container arranged outside
said circumferential wall, and the container may be provided in communication with
said means for conveying the medium from said medium inlet to said medium outlet.
[0035] The above discussed advantages of the different embodiments of the marine boiler
according to the invention are naturally transferable to the different embodiments
of the method according to the invention.
[0036] Still other objectives, features, aspects and advantages of the invention will appear
from the following detailed description as well as from the drawings.
Brief description of the drawings
[0037] The invention will now be described in more detail with reference to the appended
schematic drawings, in which
Fig. 1a schematically illustrates an engine, a marine boiler and an external power
source, partly in longitudinal cross section, according to a first embodiment,
Fig. 1b illustrates a schematic top view of the marine boiler according to the first
embodiment,
Fig. 2 schematically illustrates an engine, a marine boiler and an external power
source, partly in longitudinal cross section, according to a second embodiment,
Fig. 3a schematically illustrates an engine, a marine boiler and an external power
source, partly in longitudinal cross section, according to a third embodiment,
Fig. 3b illustrates a schematic transverse cross section, along line A-A in Fig. 3a,
of the marine boiler according to the third embodiment,
Fig. 4a schematically illustrates an engine, a marine boiler and an external power
source, partly in longitudinal cross section, according to a fourth embodiment,
Fig. 4b illustrates a schematic transverse cross section, along line B-B in Fig. 4a,
of the marine boiler according to the fourth embodiment,
Fig. 5 schematically illustrates an engine, a marine boiler and an external power
source, partly in longitudinal cross section, according to a fifth embodiment,
Fig. 6 schematically illustrates an engine, a marine boiler and an external power
source, partly in longitudinal cross section, according to a sixth embodiment, and
Fig. 7 schematically illustrates an engine, a marine boiler and an external power
source, partly in longitudinal cross section, according to a seventh embodiment.
Detailed description
[0038] In Figs. 1a and 1b a marine boiler 2 of smoke tube type is illustrated. The marine
boiler 2 is arranged onboard a ship (not illustrated) and connected to a first exhaust
gas source 4 in the form of a diesel engine 4a of the ship by a duct 6, which engine
4a is arranged for propelling the ship. Exhaust gas EG1 generated by the diesel engine
4a is fed through the duct 6 to the marine boiler 2 for exhaust gas heat recovery.
The marine boiler 2 comprises a carbon steel container 8, in turn comprising a lower
chamber or header 10, a housing 12 and an upper chamber or header 14 arranged in succession
in a vertical, longitudinal direction. The lower chamber 10 and the housing 12 both
have a circular cylindrical form and are integrally formed so as to have similar cross
sections and be concentrically arranged. The upper chamber 14 have a partly circular
cylindrical form and a smaller cross section than the lower chamber 10 and the housing
12.
[0039] The marine boiler 2 further comprises exhaust gas conveying means 16 in the form
of a first bundle of carbon steel tubes 18 extending inside the container 8 between
a lower tube plate 22 and an upper tube plate 24 of carbon steel, which plates form
lower and upper walls of the housing 12 separating the housing 12 from the lower and
upper chambers 10 and 14. The essentially similar tubes 18 are straight, have a circular
cross section and extend parallel to each other and to a longitudinal center axis
c of the housing 12. The tubes 18 are arranged to convey exhaust gas EG1 through the
container 8, which exhaust gas EG1 is received by the marine boiler 2 through an exhaust
gas inlet 26 extending into the lower chamber 10 and discharged by the marine boiler
2 through a first exhaust gas outlet 28 extending out of the upper chamber 14. When
the diesel engine 4a is running, exhaust gas EG1 is fed through the exhaust gas inlet
26, into the lower chamber 10, through the tubes 18, into the upper chamber 14 and
through the first exhaust gas outlet 28.
[0040] Further, the marine boiler 2 comprises a furnace 30 arranged inside the container
8 and a second bundle of carbon steel tubes 34 extending inside the housing 12 between
the furnace 30 and the upper tube plate 24 of the marine boiler. The essentially similar
tubes 34 are straight, have a circular cross section and extend parallel to each other
and to the longitudinal center axis c of the housing 12. The tubes 34 are arranged
to convey exhaust gas EG2 from a second exhaust gas source, in the form of an oil-fired
burner (not illustrated) arranged inside the furnace 30, through the housing 12 before
the exhaust gas EG2 leaves the marine boiler 2 through a second exhaust gas outlet
36 arranged at the upper tube plate 24.
[0041] The housing 12 of the marine boiler 2 is filled with a medium, here water, which
is fed into the housing 12 through a medium inlet 38. During operation of the engine
4, exhaust gas EG1 is fed through the tubes 18. Further, if the oil-fired burner is
running, exhaust gas EG2 is fed through the tubes 34. The water surrounds and flows
around the tubes 18, the tubes 34 and the furnace 30, and since the water is colder
than the exhaust gas EG1 and EG2, heat is transferred from the exhaust gas, through
walls of the tubes and the furnace, to the water which is heated and leaves the marine
boiler 2, in the form of a mixture of water and steam, through a medium outlet 40.
Thus, the housing 12, including a circumferential wall 42 thereof, serves as means
32 for conveying the medium from the medium inlet 38 to the medium outlet 40. Since
the housing 12, the tubes 18 and the tubes 34 are made of the same material and all
exposed to a common water volume, their temperatures will differ relatively little,
which will cause relatively limited thermal stress in the marine boiler.
[0042] The marine boiler 2 further comprises an electric heater 44 in the form of an electrode
heater, a cylindrical container 46, an inlet pipe 48 and an outlet pipe 50, which
pipes extend between, and fluidly connect, the housing 12 and the container 46. The
electric heater 44 extends into the cylindrical container 46, a longitudinal center
axis of the electric heater 44 extending essentially parallel to the longitudinal
center axis c of the housing 12 and a longitudinal center axis of the container 46.
The electric heater 44 is arranged to be connected to an external power source 52
arranged onshore, for example in a harbor, and supplied with electricity when the
ship is not moving and the engine 4a is not operated or operated at low load.
[0043] The cylindrical container 46 is filled with water, which is fed into the container
46 from the housing 12 through the inlet pipe 48. During operation of the electric
heater 44 heat is transferred from the electrical heater 44 to the water which is
heated and fed from the container 46 to the housing 12, in the form of a mixture of
water and steam, through the outlet pipe 50. The heated water leaves the marine boiler
2 through medium outlet 40. The water from the housing 12 is fed through the container
46 by natural circulation.
[0044] When the ship is out at sea, the engine 4a is typically in operation, and steam is
generated by means of exhaust gas EG1 from the engine 4a. If not an sufficient amount
of steam is generated by means of the exhaust gas EG1 from the engine 4a, the oil-fired
burner may also be operated for additional steam generation by means of exhaust gas
EG2 from the oil-fired burner. However, when the ship is idle in for example a harbor,
the engine 4a may not be operated since no propelling of the ship is to take place.
Further, neither the oil-fired burner may be operated so as to minimize the release
of harmful pollutions in the harbor. Nevertheless, steam may still be required, and
steam production may still be necessary, onboard the ship. Then, the electric heater
44 may be connected to the external power source 52 to produce the required steam,
with minimum release of pollutions in the harbor, by means of the electric heater
44.
[0045] Thus, in the marine boiler 2 hot water and steam can be generated by means of the
exhaust gas from the diesel engine, the exhaust gas from the oil-fired burner and
the electric heater. The electric heater is integrated with the rest of the boiler
in such a way as to not require a separate feed water system, steam space, steam pipe
or separate safety valves. Since no separate steam space is needed for the electric
heater it can be made relatively small with a relatively small foot print. This enables
a compact and cost effective marine boiler.
[0046] In Fig. 2 another marine boiler 54 of smoke tube type is illustrated. The marine
boiler 54 is very similar to the marine boiler 2 in Figs. 1a and 1b and hereinafter
the distinguishing features of the marine boiler 54 will be focused on. The marine
boiler 54 comprises a plurality, here three, electric heaters 44 arranged in the cylindrical
container 46. The electric heaters 44 extend into the cylindrical container 46, a
respective longitudinal center axis of the electric heaters 44 extending essentially
perpendicular to the longitudinal center axis c of the housing 12 and essentially
parallel to a longitudinal center axis of the container 46. The electric heaters 44
are arranged to be connected to an external power source 52 arranged onshore to be
supplied with electricity.
[0047] In Figs. 3a and 3b another marine boiler 56 of smoke tube type is illustrated. The
marine boiler 56 is very similar to the marine boiler 2 in Figs. 1a and 1b and hereinafter
the distinguishing features of the marine boiler 56 will be focused on. The marine
boiler 56 comprises a plurality, here two, electric heaters 44 but lacks the cylindrical
container 46, the inlet pipe 48 and the outlet pipe 50. Instead, the electrical heaters
44 extend into the housing 12 so as to be enclosed by the circumferential wall 42,
a longitudinal center axis of the electric heaters 44 extending essentially parallel
to the longitudinal center axis c of the housing 12. The electric heaters 44 are arranged
to be connected to an external power source 52 arranged onshore to be supplied with
electricity. Thus, the electric heaters 44 are surrounded by the same water volume
as the tubes 18 and 34 to which water volume heat is transferred during operation
of the electric heater 44.
[0048] In Figs. 4a and 4b another marine boiler 58 of smoke tube type is illustrated. The
marine boiler 58 is very similar to the marine boiler 56 in Figs. 3a and 3b and hereinafter
the distinguishing features of the marine boiler 58 will be focused on. The electric
heaters 44 extend into the housing 12, a respective longitudinal center axis of the
electric heaters 44 extending essentially perpendicular to the longitudinal center
axis c of the housing 12.
[0049] In Fig. 5 another marine boiler 60 of smoke tube type is illustrated. The marine
boiler 60 is very similar to the marine boiler 54 in Fig. 2 and hereinafter the distinguishing
features of the marine boiler 60 will be focused on. The marine boiler 60 comprises
a plurality, here two, electric heaters 44 arranged in a respective cylindrical container
62 and 64, respectively, which are in fluid serial connection via an intermediate
pipe 66. An inlet pipe 48 fluidly connects the housing 12 and the container 62 while
an outlet pipe 50 fluidly connects the container 64 and the housing 12.The electric
heaters 44 extend the respective cylindrical containers 62 and 64 with a respective
longitudinal center axis of the electric heaters 44 extending essentially perpendicular
to the longitudinal center axis c of the housing 12 and essentially parallel to a
respective longitudinal center axis of the containers 62 and 64, respectively.
[0050] In Fig. 6 another marine boiler 68 of smoke tube type is illustrated. The marine
boiler 68 is very similar to the marine boiler 60 in Fig. 5 and hereinafter the distinguishing
features of the marine boiler 68 will be focused on. The marine boiler 68 comprises
a plurality, here two, electric heaters 44 arranged in a respective cylindrical container
62 and 64, respectively, which are in fluid parallel connection via an inlet pipe
70 and an outlet pipe 72, which pipes branch so as to connect to both of the cylindrical
containers 62 and 64. The inlet pipe 70 fluidly connects the housing 12 and the containers
62 and 64 and the outlet pipe 72 fluidly connects the containers 62 and 64 and the
housing 12.
[0051] In Fig. 7 a marine boiler 74 of water tube type is illustrated. The marine boiler
74 is arranged onboard a ship (not illustrated) and connected to an first exhaust
gas source in the form of a diesel engine 4a of the ship by a duct 76, which engine
4a is arranged for propelling the ship. Exhaust gas EG1 generated by the diesel engine
4a is fed through the duct 76 to the marine boiler 74 for exhaust gas heat recovery.
The marine boiler 74 comprises a carbon steel container 78, in turn comprising a lower
chamber or header 80, a housing 82 and an upper chamber or header 84 arranged in succession
in a vertical, longitudinal direction. The lower chamber 80, the housing 82 and the
upper chamber 84 all have a circular cylindrical form and are integrally formed so
as to have similar cross sections and be concentrically arranged.
[0052] The marine boiler 74 further comprises a bundle of tubes 86, which extend between
a lower tube plate 88 and an upper tube plate 90, which plates form lower and upper
walls of the housing 82 separating the housing 82 from the lower and upper chambers
80 and 84. The tubes 86 form means 92 for conveying a medium, here water and steam,
through the housing 82, water being received by the marine boiler 74 through a medium
inlet 94 extending into the lower chamber 80, and steam and hot water being discharged
from the marine boiler 74 through a medium outlet 96 extending out of the upper chamber
84.
[0053] The housing 82 is arranged to convey exhaust gas EG1 through the marine boiler 74,
which exhaust gas EG1 is received by the marine boiler 74 through an exhaust gas inlet
98 extending into a lower portion of the housing 82 and discharged from the marine
boiler 74 through an exhaust gas outlet 100 extending out of an upper portion of the
housing 82. A circumferential wall 102 of the housing 82 serves as means 104 for conveying
the exhaust gas EG1 from the exhaust gas inlet 98 to the exhaust gas outlet 100.
[0054] During operation of the diesel engine 4a and the marine boiler 74, exhaust gas EG1
is fed through the housing 82. Inside the housing 82 exhaust gas EG1 surrounds and
flows around the tubes 86. Further, water is fed from the medium inlet 94 and into
the tubes 86, and since the water is colder than the exhaust gas EG1, heat is transferred
from the exhaust gas EG1, through walls of the tubes 86, to the water in the tubes
86 which is heated and leaves the marine boiler 74, in the form of steam or a mix
of water and steam, through the medium outlet 96.
[0055] The marine boiler 74 further comprises three electric heaters 44 in the form of electrode
heaters, a cylindrical container 46, an inlet pipe 106 and an outlet pipe 108, which
pipes extend between, and fluidly connect, the housing 82 and the container 46. The
electric heaters 44 extend into the cylindrical container 46, a respective longitudinal
center axis of the electric heaters 44 extending essentially perpendicular to a longitudinal
center axis c of the housing 82 and essentially parallel to a longitudinal center
axis of the container 46. The electric heaters 44 are arranged to be connected to
an external power source 52 arranged onshore, for example in a harbor, and supplied
with electricity when the ship is not moving and the engine 4a is not operated or
operated at low load.
[0056] The cylindrical container 46 is filled with water, which is fed into the container
46 from the housing 82 through the inlet pipe 106. During operation of the electric
heaters 44 heat is transferred from the electrical heaters 44 to the water which is
heated and fed from the container 46 to the housing 82, in the form of a mixture of
water and steam, through the outlet pipe 108. The heated water leaves the marine boiler
74 through medium outlet 96. The water from the housing 82 is fed through the container
46 by natural circulation.
[0057] When the ship is out at sea, the engine 4a is typically in operation, and steam is
generated by means of exhaust gas EG1 from the engine 4a. However, when the ship is
idle in for example a harbor, the engine 4a may not be operated since no propelling
of the ship is to take place. Nevertheless, steam may still be required, and steam
production may still be necessary, onboard the ship. Then, the electric heaters 44
may be connected to the external power source 52 to produce the required steam and
hot water, with minimum release of pollutions in the harbor, by means of the electric
heaters 44.
[0058] The above described embodiments of the present invention should only be seen as examples.
A person skilled in the art realizes that the embodiments discussed can be varied
and combined in a number of ways without deviating from the inventive conception.
[0059] For example, a boiler according to the invention could comprise any number of electric
heaters, i.e. one, two, three or more. In the case of more than one electric heater,
the electric heaters may be of the same type or different types.
[0060] The electric heater(s) of a boiler could be arranged within the housing or outside
the housing of the boiler, i.e. within the external container. In the case of a plurality
of electric heaters, a combination is possible, i.e. one or more of them could be
arranged within the housing and the rest of them could be arranged outside the housing.
[0061] Further, in the case of a plurality of electric heaters, all or some of them could
be arranged in a common external container or in a respective external container.
[0062] In the case of a plurality of external containers, these could be fluidly connected
in parallel, in series, or separately to the housing of the boiler. Any combination
thereof is also possible.
[0063] The electric heater(s) of a boiler could longitudinally extend in any suitable direction,
for example parallel or perpendicular to the longitudinal center axis c of the housing
of the boiler. In the case of a plurality of electric heaters, a combination is possible,
i.e. one or more of them could longitudinally extend parallel to the longitudinal
center axis c of the housing and the rest of them could longitudinally extend perpendicular
to the longitudinal center axis c of the housing.
[0064] In the case of a boiler comprising one or more external containers for accommodation
of one or more electric heaters, these one or more external containers could longitudinally
extend in any suitable direction, and the same direction or different directions,
such as parallel or perpendicular to the longitudinal center axis c of the housing
of the boiler.
[0065] Further, in the case of a boiler comprising one or more external containers for accommodation
of one or more electric heaters, these one or more external containers could have
any suitable design, and the same design or different designs. Thus, the external
container(s) need not be circular cylindrical but could have any suitable cross section,
such as a polygonal cross section.
[0066] Naturally, also other components of the boiler could have alternative designs than
illustrated in the drawings.
[0067] The components of the boiler need not be made of carbon steel but could be made of
other materials, such as aluminum or stainless steel.
[0068] Combinations of the above design alternatives are possible.
[0069] The power source for supplying the electric heater(s) with electricity need not be
arranged in a harbor but could be arranged somewhere else, on land or not. As an example,
the power source could be a "clean" power source, for example a solar power source,
arranged onboard the ship.
[0070] The marine boilers of smoke tube type need not comprise a furnace and tubes extending
from the furnace for conveying exhaust gas from a burner arranged inside the furnace.
Further, the marine boilers of smoke tube type need not be arranged to receive exhaust
gas from an engine. As an example, the marine boiler could be arranged to receive
exhaust gas from a first exhaust gas source in the form of a burner, which burner
possibly could be arranged inside a furnace, in turn arranged inside a container of
the marine boiler. With reference to Fig. 1, such a marine boiler would lack the exhaust
gas inlet 26, the lower chamber 10, the tubes 18, the upper chamber 14 and the exhaust
gas outlet 28.
[0071] It should be stressed that a description of details not relevant to the present invention
has been omitted and that the figures are just schematic and not drawn according to
scale. It should also be said that some of the figures have been more simplified than
others. Therefore, some components may be illustrated in one figure but left out in
another figure. Finally, as used herein, the prefixes "first", "second", "top", "bottom",
"upper", "lower", "horizontal", "vertical" etc. are used only to distinguish between
different components and pose no requirements as regards relative positioning or orientation.
1. A marine boiler (2, 54, 56, 58, 60, 68, 74) for transferring heat from exhaust gas
(EG1, EG2) to a medium onboard a ship, the marine boiler (2, 54, 56, 58, 60, 68, 74)
comprising an exhaust gas inlet (26, 98) for receiving exhaust gas (EG1) from a first
exhaust gas source (4), a first exhaust gas outlet (28, 100) for discharging exhaust
gas (EG1) from said first exhaust gas source (4), means (16, 104) for conveying exhaust
gas (EG1) from the first exhaust gas source (4) from said exhaust gas inlet (26, 98)
to said first exhaust gas outlet (28, 100), a medium inlet (38, 94) for receiving
the medium, a medium outlet (40, 96) for discharging the medium, means (32, 92) for
conveying the medium from said medium inlet (38, 94) to said medium outlet (40, 96),
and a circumferential wall (42, 102) inside which exhaust gas (EG1) from the first
exhaust gas source (4) and the medium are arranged to be conveyed, characterized in further comprising an electric heater (44) for heating said medium by means of electricity
supplied from a power source (52), which power source (52) is separate from said first
exhaust gas source (4).
2. A marine boiler (2, 54, 56, 58, 60, 68, 74) according to claim 1, wherein said power
source (52) is separate from any exhaust gas source onboard the ship.
3. A marine boiler (2, 54, 56, 58, 60, 68, 74) according to any of the preceding claims,
wherein said power source (52) is separate from the ship.
4. A marine boiler (2, 54, 56, 58, 60, 68, 74) according to any of the preceding claims,
wherein said power source (52) is arranged onshore.
5. A marine boiler (2, 54, 56, 58, 60, 68, 74) according to any of the preceding claims,
wherein said first exhaust gas source (4) comprises an engine (4a) for propelling
the ship.
6. A marine boiler (2, 54, 56, 58, 60, 68) according to any of the preceding claims,
wherein said means (16) for conveying exhaust gas (EG1) from said exhaust gas inlet
(26) to said first exhaust gas outlet (28) comprise a first bundle of tubes (18),
and said means (32) for conveying the medium from said medium inlet (38) to said medium
outlet (40) comprise said circumferential wall (42) of the marine boiler (2, 54, 56,
58, 60, 68) enclosing said first bundle of tubes (18).
7. A marine boiler (74) according to any of claims 1-5, wherein said means (92) for conveying
the medium from said medium inlet (94) to said medium outlet (96) comprise one or
more tubes (86), and said means (104) for conveying exhaust gas (EG1) from said exhaust
gas inlet (98) to said first exhaust gas outlet (100) comprise said circumferential
wall (102) of the marine boiler (74) enclosing said one or more tubes (86).
8. A marine boiler (56, 58) according to any of the preceding claims, wherein the electric
heater (44) is arranged inside said circumferential wall (42).
9. A marine boiler (2, 54, 60, 68, 74) according to any of claims 1-7, wherein the electric
heater (44) is arranged in a container (46, 62, 64) arranged outside said circumferential
wall (42, 102), which container (46, 62, 64) is in communication with said means (16,104)
for conveying the medium from said medium inlet (38, 94) to said medium outlet (40,
96).
10. A method of operating a marine boiler (2, 54, 56, 58, 60, 68, 74) to transfer heat
from exhaust gas (EG1, EG2) to a medium onboard a ship, comprising,
conveying exhaust gas (EG1) from a first exhaust gas source (4) from an exhaust gas
inlet (26, 98) to a first exhaust gas outlet (28, 100) of the marine boiler (2, 54,
56, 58, 60, 68, 74), and
conveying the medium from a medium inlet (38, 94) to a medium outlet (40, 96) of the
marine boiler (2, 54, 56, 58, 60, 68, 74), the marine boiler (2, 54, 56, 58, 60, 68,
74) comprising a circumferential wall (42, 102) inside which exhaust gas (EG1) from
the first exhaust gas source (4) and the medium are arranged to be conveyed,
characterized in further comprising,
supplying an electric heater (44) with electricity from a power source (52), which
power source (52) is separate from said first exhaust gas source (4), and heating
said medium by means of said electric heater (44).
11. A method according to claim 10, comprising providing said power source (52) separate
from any exhaust gas source onboard the ship.
12. A method according to any of claims 10-11, comprising providing said power source
(52) onshore.
13. A method according to any of claims 10-12, comprising providing an engine (4a) for
propelling the ship as said first exhaust gas source (4).
14. A method according to any of the claims 10-13, comprising providing the electric heater
(44) inside said circumferential wall (42, 102).
15. A method according to any of claims 10-13, comprising providing the electric heater
(44) in a container (46, 62, 64) arranged outside said circumferential wall (42, 102),
and providing the container (46, 62, 64) in communication with said means (16, 104)
for conveying the medium from said medium inlet (38, 94) to said medium outlet (40,
96).