WO2023274559A1

WO2023274559A1 - Arrangement and method in liquid hydrogen fuel supply system

Info

Publication number: WO2023274559A1
Application number: PCT/EP2021/068378
Authority: WO
Inventors: Alessandro SCOCCHI; Emanuele D'URSO; Piero ZOGLIA; Andreas SNELLMAN; Malgorzata KOCZUR
Original assignee: Wärtsilä Finland Oy
Priority date: 2021-07-02
Filing date: 2021-07-02
Publication date: 2023-01-05

Abstract

A fuel tank arrangement in a liquid hydrogen fuel supply system (1), the fuel tank arrangement comprising: - a tank (10) for storing liquid hydrogen fuel, the tank (10) is formed of an inner tank shell (10a), an outer tank shell (10b) and a heat insulation (10c) therebetween, - an inlet line (11) for supplying fuel to the tank (10), - a liquid outlet line (12b) for supplying liquid fuel from the liquid space of the tank (10), - a gas outlet line (12a) for supplying gaseous fuel from the gas space of the tank (10), - a main gas evaporator (152) connected to the liquid outlet line (12b) for evaporating liquid fuel into gaseous form and supplying gaseous fuel for a consumer (8), - a tank connection space shell (101) together with a part of the outer tank shell (10b) enclosing a tank connection space (100) wherein lead-throughs to the tank (10), inlet line (11) connected thereto, outlet lines (12a, 12b) connected thereto, the main gas evaporator (152) and ventilation lines (102) are located, - the tank connection space shell (101) is formed of an inner shell (101a), an outer shell (101 b) and an inert gas space (101 c) therebetween, an inert gas supply (130) for supplying inert gas is connected to the inert gas space (101c). The invention relates also to a method in monitoring gas-tightness or potential leakages in the fuel tank arrangement.

Description

Arrangement and method in liquid hydrogen fuel supply system

Technical field

[001] The present invention relates to a fuel tank arrangement in a liquid hydro- gen fuel supply system according to the preamble of claim 1. The present inven tion relates also to a method in monitoring gas-tightness or potential leakages in a fuel tank arrangement according to the preamble of claim 10.

[002] More specifically the present invention relates a fuel tank arrangement in a liquid hydrogen fuel supply system, the fuel tank arrangement comprising: - a tank for storing liquid hydrogen fuel, the tank is formed of an inner tank shell, an outer tank shell and a heat insulation therebetween,

- an inlet line for supplying fuel to the tank,

- a liquid outlet line for supplying liquid fuel from the liquid space of the tank,

- a gas outlet line for supplying gaseous fuel from the gas space of the tank, - a main gas evaporator connected to the liquid outlet line for evaporating liquid fuel into gaseous form and supplying gaseous fuel for a consumer,

- a tank connection space shell together with a part of the outer tank shell en closing a tank connection space wherein lead-throughs to the tank, inlet line con nected thereto, outlet lines connected thereto, the main gas evaporator and ven- tilation lines are located.

[003] More specifically the method of present invention relates to a method in monitoring gas-tightness or potential leakages in a fuel tank arrangement of the present invention. Background art

[004] Natural gas as a fuel for internal combustion engines in marine vessels, power plants and such, has become more common because of the environmen tal reasons since the combustion results are less harmful than for example those resulted in combustion of heavy or light fuel oil. However, also gaseous fossil fuels are generally harmful to the environment and therefore any leakage to the atmosphere is undesired. That is why all equipment for handling and regulating gas fuel is subjected to stringent safety regulations. In a transformation from fos sil fuels to renewable fuels one possible next step is hydrogen. The same or even more demanding regulations apply if the gaseous fuel is hydrogen instead of liq- uified natural gas (LNG) because hydrogen has even lower boiling temperature than the LNG. Hydrogen has also small molecular size making it prone to leak.

[005] Hydrogen is one of the most potential alternative fuels for future needs. Hydrogen can be used in a mixture of fuels in an internal combustion piston en gine. For example, with LNG it can be used up to a certain share of the total fuel mixture. Alternatively, hydrogen can be used as the only fuel for a fuel cell. A fuel cell is an electrochemical cell that converts the chemical energy of a fuel, such as hydrogen and an oxidizing agent into electricity through a pair of oxidation- reduction (redox) reactions. Fuel cell systems are different from most batteries in requiring a continuous source of fuel and oxygen to sustain the chemical reac- tion. In that sense the requirements of hydrogen based power systems are closer to the LNG-fuel systems than a battery-based system.

[006] In a basic configuration of a liquid hydrogen fuel (LH2) fuel tank arrange ment, a tank is formed of an inner tank shell, an outer tank shell and a heat insu lation therebetween. At an end of the tank a tank connection space is arranged. Naturally, the tank connection space may as well be located at a side of the LH2- fuel tank, and not necessarily as an extension of the shell of the tank but also at a distance from the shell of the tank, i.e. as a separate chamber at a side or at an end of the LH2- fuel tank. A tank connection space shell together with a part of the tank wall encloses the tank connection space wherein lead-throughs to the tank, inlet line or inlet lines and valves connected thereto, outlet lines and valves connected thereto, a main gas evaporator and ventilation lines and correspond ing valves are located. The tank connection space is, preferably, but not neces sarily, provided with heat insulation. However, for various reasons both the tank and the tank connection space used for storing and handling liquid hydrogen re- quire specific attention. Firstly, hydrogen storage and processing in general imply high risk of fire and explosion due to, on the one hand, the wide range of mixture giving explosive atmosphere and, on the other hand, the low ignition energy typ ical to hydrogen. Secondly, the detection of hydrogen leak into the ambient space is relatively slow. All line connections to the tank, tank lead throughs, valves and other equipment are potential origins of leakage and that is why these are re quired to enclose to the tank connection space. The tank connection space shell forms the enclosure of the tank connection space. [007] For reference, publication WO 2020/182308 A1 presents a fuel tank ar rangement of a marine vessel, the tank arrangement comprising a liquid hydro gen fuel tank, a tank connection space arranged in communication with the liquid hydrogen fuel tank, the tank connection space being provided with a vent mast having a lower end and an upper end, and an interior, the interior of the vent mast forming a ventilation outlet line for discharging gas from the tank connection space, an emergency pressure relief valve coupled via a safety valve line to the gas space of the fuel tank, wherein a first hydrogen outlet line provided in the vent mast is separate from the ventilation outlet line, the first hydrogen outlet line extending from the lower end of the vent mast to the upper end thereof and being arranged in flow communication with the emergency pressure relief valve.

[008] One of aspects that needs to be taken in to account is the very low boiling temperature of liquified gaseous fuels. With liquid hydrogen (LH2) that is -252,87 °C and that affects in design of the LH2 fuel supply system. As normal atmos phere temperatures are significantly above the boiling temperature of LH2 and meaning that the liquid fuel would boil and transit to gas phase very quickly when in connection with any non-cryogenic components such as fuel supply system parts, pipes, valves, etc. in atmosphere temperature. For economical and practi cal reasons the cryogenic conditions are limited to the minimum, such as to the tank and to the proximity of the tank, such as to a tank connection space. The tank is surrounded by valves so that any connection such as a fuel supply line to or from the tank is equipped with a valve.

[009] An object of the invention is to provide a fuel tank arrangement in a liquid hydrogen fuel supply system in which the performance is considerably improved compared to the prior art solutions. Another object is to provide a method in mon itoring gas-tightness or potential leakages in a fuel tank arrangement. Disclosure of the Invention

[0010] Objects of the invention can be met substantially as is disclosed in the independent claims and in the other claims describing more details of different embodiments of the invention.

[0011] According to an embodiment of the invention a fuel tank arrangement is provided in a liquid hydrogen fuel supply system, the fuel tank arrangement com prising:

- a tank for storing liquid hydrogen fuel, the tank is formed of an inner tank shell, an outer tank shell and a heat insulation therebetween,

- an inlet line for supplying fuel to the tank,

- a gas outlet line for supplying gaseous fuel from the gas space of the tank,

- a main gas evaporator connected to the liquid outlet line for evaporating liquid fuel into gaseous form and supplying gaseous fuel for a consumer,

- a tank connection space shell together with a part of the outer tank shell en closing a tank connection space wherein lead-throughs to the tank, inlet line con nected thereto, outlet lines connected thereto, the main gas evaporator and ven tilation lines are located, - the tank connection space shell is formed of an inner shell, an outer shell and an inert gas space therebetween, an inert gas supply for supplying inert gas is connected to the inert gas space.

[0012] This provides an effect that liquid or gaseous hydrogen lines, possible valves and other equipment connected to the tank are secured and possibly leak- ing fuel cannot end up to a place where it can cause danger or even explode. By such an arrangement the performance is considerably improved and still the con struction can be made at an economically reasonable cost. First there are the lines, valves and other equipment that are designed for use in demanding cryo genic conditions, then there is the tank connection space forming the second barrier to stop the possibly leaking hydrogen and then there is the inert gas space as a third barrier. The inert gas supply for supplying inert gas to the inert gas space further enables effective preventing of leakages to ambient space. Any leakage may be detected already in the tank connection space but the latest in the inert gas space.

[0013] According to an embodiment the inert gas supply is configured to pres surize the inert gas space. By having a pressure difference between the tank connection space and the inert gas space it is possible to prevent the leakages from a space to another. An over pressure in one space or chamber prevents leakage from lower pressure space to higher pressure space.

[0014] According to an embodiment the fuel tank arrangement comprises an in ert gas supply configured to pressurize the tank connection space. Preferably between the tank connection space and the inert gas space pressure difference is maintained such that the pressure of the inert gas space is higher than the pressure in the tank connection space. By this pressure difference a potential leakage would be detected already in the tank connection space and there would be still one barrier left before ambient space. The tank connection space pres- sure is preferably maintained in a proximity to the atmosphere pressure. The tank connection space shell construction needs to fulfil in most cases pressure vessel specifications, but it is not required to maintain any higher pressure that practical.

[0015] According to an embodiment both the tank connection space and the inert gas space are monitored such that in a case of temperature change both can be ventilated with inert gas and substitute the possible gaseous fuel in said spaces.

[0016] According to an embodiment the inert gas space between the inner shell and the outer shell has a ventilation line connected to atmosphere. In a case of leakage inert gas can be supplied to the inert gas space and substitute the hy drogen that is flowing out through the ventilation line to the atmosphere. Prefer- ably the ventilation connection is located at a top elevation position of the inert gas space. As the specific weight of hydrogen in gaseous phase is very light, at least lighter that the inert gas, preferably nitrogen, those gases will not mix very easily but they stay separate. Hydrogen as being the lightest will stay on top (in a gravity direction) of the nitrogen and according to the embodiment of the inven- tion, ventilation connection such as ventilation mast located at a top elevation will automatically remove first the leaked hydrogen from the inert gas space. Prefer ably the same principle is utilized in the tank connection space, a ventilation connection is located at a top elevation position of the tank connection space. Thus, in a case of leakage of fuel gas is detected a specific weight separation is used in venting the tank connection space and/or the inert gas space, such that the inert gas being heavier in specific weight than the fuel gas, and the inert gas is led to the bottom of said space and the lighter fuel gas is substituted to the ventilation connection located at the top elevation position of said spaces.

[0017] According to embodiments of the invention the fuel tank arrangement comprises pressure and/or temperature gauges configured to monitor pressure and/or temperature in the inert gas space. Similarly, the fuel tank arrangement comprises pressure and/or temperature gauges configured to monitor pressure and/or temperature in the tank connection space. If liquid or gaseous hydrogen would leak from the lines, valves or other equipment, it would be most practical way to detect the incident as a change of temperature and/or pressure. Thus, an embodiment of the invention is a method in monitoring gas-tightness or potential leakages in a fuel tank arrangement, in which the inert gas space and/or the tank connection space pressure and/or temperature is being monitored, and in steady state conditions a change in temperature and/or pressure is considered to indi cate a leakage. Thus, the monitoring can be done in the tank connection space or in the inert gas space or in both spaces, preferred is the monitoring in both spaces because it gives the fastest detection of any abnormal behaviour of the liquid hydrogen fuel supply system. Behaviour of the hydrogen at the liquid hy drogen fuel supply system depends on the position of a possible leakage. In a closed space gas temperature and pressure are dependent on each other, in a constant volume the gas pressure and temperature follow approximately equa- tion: pi/Ti=p₂/T₂. If the leakage is in part where liquid hydrogen is involved, the temperature will first most likely decrease and so will the pressure. If the leakage occurs after an evaporator where the liquid hydrogen has been evaporated and warmed, the temperature and pressure will most likely raise. In a steady state condition the temperature and pressure in the tank connection space and/or inert gas space would stay constant and then a change in the pressure and/or tem perature would be relatively easy to detect. However, if the conditions are non steady state i.e. the conditions are anyway changing due to start up, shut down or some other mode change of the system, it would necessary to predict the “normal” behaviour of the fuel system and detect any deviation from the “normal” to determine if leakage preventing actions are needed. According to an embodi ment both the tank connection space and the inert gas space are monitored such that in a case of temperature change both can be ventilated with inert gas and substitute the possible gaseous fuel in said spaces. [0018] The exemplary embodiments of the invention presented in this patent ap plication are not to be interpreted to pose limitations to the applicability of the appended claims. The verb "to comprise" is used in this patent application as an open limitation that does not exclude the existence of also unrecited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. An operator “and/or” is used in this patent application to express multiple possibilities to combine features, A and/or B means that there may be A alone, B alone or A and B together present in the configuration. The novel features which are considered as characteristic of the invention are set forth in particular in the appended claims.

Brief Description of Drawings

[0019] In the following, the invention will be described with reference to the ac companying exemplary, schematic drawings, in which

Figure 1 illustrates a fuel tank arrangement in a liquid hydrogen fuel supply sys- tern according to an embodiment of the invention,

Figure 2 illustrates a fuel tank arrangement in a liquid hydrogen fuel supply sys tem according to another embodiment of the invention.

Detailed Description of Drawings

[0020] Figure 1 depicts schematically a fuel tank arrangement in a liquid hydro gen fuel supply system 1, the fuel tank arrangement comprising:

- a tank 10 for storing liquid hydrogen fuel, the tank 10 is formed of an inner tank shell 10a, an outer tank shell 10b and a heat insulation 10c therebetween,

- an inlet line 11 for supplying fuel to the tank 10,

- a liquid outlet line 12b for supplying liquid fuel from the liquid space of the tank

10,

- a gas outlet line 12a for supplying gaseous fuel from the gas space of the tank

10,

- a main gas evaporator 152 connected to the liquid outlet line 12b for evaporating liquid fuel into gaseous form and supplying gaseous fuel for a consumer 8,

- a tank connection space shell 101 together with a part of the outer tank shell 10b enclosing a tank connection space 100 wherein lead-throughs to the tank, inlet line 11 connected thereto, outlet lines 12a, 12b connected thereto, the main gas evaporator 152 and ventilation lines 102 are located,

- the tank connection space shell 101 is formed of an inner shell 101a, an outer shell 101b and an inert gas space 101c therebetween, an inert gas supply 130 for supplying inert gas is connected to the inert gas space 101c.

[0021] The embodiment of Fig. 1 gives a schematic overview of a fuel tank ar rangement in a liquid hydrogen fuel supply system 1. A tank 10 is provided for storing liquid hydrogen fuel, the tank 10 is formed of an inner tank shell 10a, an outer tank shell 10b and a heat insulation 10c therebetween. The fuel is supplied to the tank 10 from a source connectable to a bunkering station connection B, through an inlet line 11 for supplying fuel to the tank 10. The Inlet line is provided with a valve 111 and valve 112 that is opened for filling and closed when filling is ready. In the embodiment of Fig 1 the tank 10 end of the inlet line 11 is branched 11a, 11b and the branches are provided with valves 11a1, 11 b1 for selectable open and close the inlet line 11 end to a liquid space of the tank 10 or to a gas space of the tank 10. As the actual level of liquid fuel and gas space is constantly changing due to consumption and filling, the ends 11a, 11b of the inlet line 11 are preferably placed somewhere near the top of the tank 10 and the bottom of the tank 10. The same applies to outlet lines 12a, 12b from the tank.

[0022] The embodiment of Fig. 1 presents further a liquid outlet line 12b for sup plying liquid fuel from the liquid space of the tank 10. A pump 153 may be used for providing the liquid fuel further. A gas outlet line 12a is for supplying gaseous fuel from the gas space of the tank 10. Liquid hydrogen is very prone in forming gas in the tank, so called boil-off gas, and that is also useful to be able to lead to a consumer 8, such as an engine or a fuel cell system and corresponding sys tems. A main gas evaporator 152 is connected to the liquid outlet line 12b for evaporating liquid fuel into gaseous form and supplying gaseous fuel for a con sumer 8. It is also possible to use the boil-off gas from the gas space of the tank for the gas consumer 8. In this case the gas outlet line 12a may also be con nected to a compressor Compjn for pressurizing the gas and then led back from Comp_out to the consumer 8. In case the pressure in the tank gas space is tem- porarily sufficiently high for the gas consumer, gas outlet line 12ac is used for bypassing the main gas evaporator 152. In this case a heater 154, that is opti mised for heating the cold boil-off gas, can be used for heating the gas to a suf ficient temperature for the gas consumer 8. The main gas evaporator 152 and the heater 154 have been connected in parallel for the heating fluid flow (HJn, H_out) in Figure 1 , but the heating fluid flow could also be connected in series between the heat exchangers since only one of them is being used for evaporat ing or heating hydrogen at a time.

[0023] A tank connection space shell 101 together with a part of the outer tank shell 10b encloses a tank connection space 100 wherein lead-throughs to the tank 10, inlet line 11 and valves 112, 11a1, 11 b1 connected thereto, outlet lines 12a, 12b and valves 121, 122, 126, 81 connected thereto, the main gas evapo rator 152 and ventilation lines 102, and corresponding valves are located. The above listed parts do not form a comprehensive list of equipment located in the tank connection space but gives an idea of the purpose of tank connection space. Some parts such as valves may be located in a separate compartment having similar construction and functions as the present arrangement. Practically all lead-throughs to and from the tank 10, line-to-valve, line-to-line -connections, valves, and other gas containing machine parts are possible origins for leakages. The fuel tank arrangement may be in a marine vessel or in a land-based system where there are practically always vibrations when in use. Liquified hydrogen has a considerable temperature difference to a normal temperature in atmosphere. Those vibrations and temperature changes may cause loose connections, joints and seals, therefore the tank connection space is required to provide safe loca tion for those equipment.

[0024] The tank connection space shell 101 is formed of an inner shell 101a, an outer shell 101b and an inert gas space 101c therebetween, an inert gas supply 130 for supplying inert gas is connected to the inert gas space 101c. The tank connection space shell is a double wall vessel construction with gas filled space between the inner shell and the outer shell. Preferably the inert gas supply 130 is configured to pressurize the inert gas space 101c. Most suitably the pressure in the inert gas space 101c is higher than the pressure in the tank connection space 100 and higher than the pressure outside the tank connection space shell 101, which helps to detect any possible leakages and restrict those to tank con nection space 100 if the leakage would be there. As there is an inert gas supply 130 connected, the inert gas space 101c between the inner shell 101a and the outer shell 101b has also a ventilation line 103 connected to atmosphere. This means that the inert gas space 101c can be actively ventilated, inert gas can be led into the inert gas space so it can blow out possible leaked fuel gases. As schematically shown in Fig. 1, the ventilation connection 103 is located at a top elevation position of the inert gas space 101c and the ventilation connection 103 can be opened when needed, thus being provided with a control valve (not shown). [0025] The fuel tank arrangement comprises pressure and/or temperature gauges 116 configured to monitor pressure and/or temperature in the inert gas space 101c. As explained earlier in this description, the temperature and pres sure monitoring in the inert gas space 101c are among the easiest ways to detect possible leakages. Liquid hydrogen, tank boil-off hydrogen and evaporated hy- drogen after a main gas evaporator has its own characteristic in temperature and pressure behaviour and it may be detected be relatively simple means. In de signing such a monitoring system one needs to consider to cryogenic suitability of temperature and/or pressure gauges. Alternatively some chemical composition detection can also be used, but temperature and pressure measure ments are at the moment seen as preferred embodiments for leakage detection. The same applies in the tank connection space, preferably the fuel tank arrange ment comprises pressure and/or temperature gauges 116 configured to monitor pressure and/or temperature in the tank connection space 100.

[0026] According to an embodiment the fuel tank arrangement comprises an in ert gas supply 130 configured to pressurize the tank connection space 100. Since most of the potential leaking sources are located in the tank connection space, it is good practice to replace normal air containing oxygen with an inert gas in the tank connection space. Normal air having about 21% of oxygen mixed with leak ing hydrogen produces rapidly an explosive mixture. The preferred inert gas is nitrogen.

[0027] In Fig. 1 it is presented an embodiment where a service hatch 104 is provided through the outer shell 101b and the inner shell 101a to the tank con- nection space 100. The equipment located in the tank connection space 100 needs service, maintenance and some parts may need to change time to time and therefore the service hatch 104 needs to be arranged to provide access to the tank connection space 100. The service hatch 104 has a dual hatch construc tion having an inner hatch 104a on the inner shell 101a and an outer hatch 104b on the outer shell 101b. Between the inner hatch 104a and the outer hatch 104b is a hatch space 104c that is isolated by gas tight wall from the inert gas space 101c. However, as the service hatch 104 itself is one possible location for leak ages, it needs to be designed accordingly. The hatch space 104c has an inerting system similar to the inert gas space 101c. Preferably the service hatch 104 is provided with a leak protection system comprising an inert gas substitution 130 and venting system 105 in the hatch space 104c between the inner hatch 104a and the outer hatch 104b. For reference, one suitable design is introduced in publication WO2017/042424 A1.

[0028] The above explained arrangement is subject to a method in monitoring gas-tightness or potential leakages in a fuel tank arrangement. The inert gas space 101c pressure and/or temperature is being monitored, and in steady state conditions a change in temperature and/or pressure is considered to indicate a leakage. A steady state condition means a situation, when the running parameters of the system have been stable for a while, for example engine load and temperature are constant. This is the case for example in a marine vessel when the vessel has left the harbour and entered into a constant cruise speed operation. Correspondently, the method in monitoring gas-tightness or potential leakages in a fuel tank arrangement comprises that the tank connection space 100 pressure and/or temperature is being monitored, and in steady state condi tions a change in temperature and/or pressure is considered to indicate a leak age. Preferably both the tank connection space 100 and the inert gas space 101c are being monitored, but in some case just monitoring either one may be suffi- cient.

[0029] According to an embodiment, between the tank connection space 100 and the inert gas space 101c pressure difference is maintained such that the pressure of the inert gas space 101c is higher than the pressure in the tank con nection space 100. With the present arrangement, no excessive pressures are needed in the tank connection space, preferably the tank connection space 100 pressure is maintained in a proximity to the atmosphere pressure. According to an embodiment of the method, both the tank connection space 100 and the inert gas space 101c are monitored such that in a case of temperature change both can be ventilated with inert gas and substitute the possible gaseous fuel in said spaces 100, 101c. In a case where leakage of fuel gas is detected, a specific weight separation is used in venting the tank connection space 100 and/or the inert gas space 101c, such that the inert gas being heavier in specific weight than the fuel gas, and the inert gas is led to the bottom of said space 100, 101c and the lighter fuel gas is substituted to the ventilation 102, 103 connection to atmos- phere located at the top elevation position of said spaces 100, 101c. The venti lation 103 from the inert gas space 101c comprises a pressure relief valve that opens if pressure in the space 101c exceeds a certain value. The ventilation 102 comprises lines with pressure relief valves from the tank 10 gas phase, and from the tank connection space 100. The ventilation connection 102 can also be opened when needed, thus being provided with a control valve. Ventilations 102,

103 may be arranged for example as disclosed in a publication W02020/182308A1. [0030] In Fig. 2 it is presented basically an arrangement similar to the embodi ment of Fig. 1. The main difference is in the fuel supply for consumer, at an outlet side of the tank 10. There it is provided a pressure build-up evaporator 151 that evaporates liquid hydrogen and supplies it as gas back to the tank 10 (or alter- natively to the consumer 8. The principle is to use pressurized tank 10 instead of pump 153 as in embodiment of Fig. 1. Flow from pressure build-up evaporator 151 to tank or to main gas evaporator 152 or by-pass of pressure build-up evap orator 151 are controlled by selecting open/closed positions of valves 122, 123 and 128. Evaporation heat is taken from a heat source HJn as in embodiment of Fig. 1, the heat source may be consumer or some other external heat source such as electric heater or corresponding.

[0031] Figure 2 depicts schematically a fuel tank arrangement in a liquid hydro gen fuel supply system 1, the fuel tank arrangement comprising:

- an inlet line 11 for supplying fuel to the tank 10,

10, - a gas outlet line 12a for supplying gaseous fuel from the gas space of the tank

10,

- a pressure build-up evaporator 151 connected to the liquid outlet line 12b for evaporating liquid fuel into gaseous form and supplying gaseous fuel to the tank 10 for increasing pressure in the tank 10 - a main gas evaporator 152 connected to the liquid outlet line 12b for evaporating liquid fuel into gaseous form and supplying gaseous fuel for a consumer 8,

- a tank connection space shell 101 together with a part of the outer tank shell 10b enclosing a tank connection space 100 wherein lead-throughs to the tank, inlet line 11 and valves 112, 11a1, 11 b1 connected thereto, outlet lines 12a, 12b and valves 121, 122, 123, 126, 128 and 81 connected thereto, the main gas evaporator 152, pressure build-up evaporator 151 and ventilation lines 102, and corresponding valves are located,

[0032] In Fig. 2 the features relating to temperature and/or pressure monitoring and features relating to inert gas supply 130 for inert gas space 101c / tank con- nection space 100 are the same as already disclosed in connection to Figure 1.

[0033] While the invention has been described herein by way of examples in connection with what are, at present, considered to be the most preferred em bodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various combinations or modifications of its features, and several other applications included within the scope of the in vention, as defined in the appended claims. The details mentioned in connection with any embodiment above may be used in connection with another embodi ment when such combination is technically feasible. Part list

1 fuel supply system 10 tank 10a inner tank shell 10b outer tank shell 10c insulation

100 tank connection space

101 tank connection space shell 101a inner shell

101b outer shell 101c inert gas space

102 tank connection space ventilation line

103 inert gas space ventilation line

104 service hatch 104a inner hatch

104b outer hatch 104c hatch space 105 hatch ventilation line

11 inlet line

11a inlet line to gas space

11 a1 valve

11b inlet line to liquid space

I I b1 valve

I II first valve

112 second valve

116 pressure and/or temperature gauge

12a gas outlet line

12ac gas outlet line

12b liquid outlet line

121, 122, 123, 126, 128 valve

130 source of inert gas

151 pressure build-up evaporator

152 main gas evaporator

153 fuel pump

154 heater

8 gas consumer

B bunkering station connection

Claims

1. A fuel tank arrangement in a liquid hydrogen fuel supply system (1), the fuel tank arrangement comprising:

- a tank (10) for storing liquid hydrogen fuel, the tank (10) is formed of an inner tank shell (10a), an outer tank shell (10b) and a heat insulation (10c) there between,

- an inlet line (11) for supplying fuel to the tank (10),

- a liquid outlet line (12b) for supplying liquid fuel from the liquid space of the tank

(10),

- a gas outlet line (12a) for supplying gaseous fuel from the gas space of the tank

(10),

- a main gas evaporator (152) connected to the liquid outlet line (12b) for evapo rating liquid fuel into gaseous form and supplying gaseous fuel for a consumer (8),

- a tank connection space shell (101) together with a part of the outer tank shell (10b) enclosing a tank connection space (100) wherein lead-throughs to the tank (10), inlet line (11) connected thereto, outlet lines (12a, 12b) connected thereto, the main gas evaporator (152) and ventilation lines (102) are located, characterized in that

- the tank connection space shell (101) is formed of an inner shell (101a), an outer shell (101b) and an inert gas space (101c) therebetween, an inert gas sup ply (130) for supplying inert gas is connected to the inert gas space (101c).

2. The fuel tank arrangement according to claim 1 , characterized in that the inert gas supply (130) is configured to pressurize the inert gas space (101c).

3. The fuel tank arrangement according to claim 1 or claim 2, characterized in that the inert gas space (101c) between the inner shell (101a) and the outer shell (101b) has a ventilation line (103) connected to atmosphere.

4. The fuel tank arrangement according to claim 3, characterized in that the ventilation connection (103) is located at a top elevation position of the inert gas space (101c).

5. The fuel tank arrangement according to claim 1 , characterized in that the fuel tank arrangement comprises pressure and/or temperature gauges (116) con figured to monitor pressure and/or temperature in the inert gas space (101c).

6. The fuel tank arrangement according to claim 1 , characterized in that the fuel tank arrangement comprises pressure and/or temperature gauges (116) con figured to monitor pressure and/or temperature in the tank connection space (100).

7. The fuel tank arrangement according to claim 1 , characterized in that the fuel tank arrangement comprises an inert gas supply (130) configured to pres surize the tank connection space (100).

8. The fuel tank arrangement according to claim 1, characterized in that a service hatch (104) is provided through the outer shell (101b) and the inner shell

(101a) to the tank connection space (100), the service hatch (104) has a dual hatch construction having an inner hatch (104a) and an outer hatch (104b).

9. The fuel tank arrangement according to claim 7, characterized in that the service hatch (104) is provided with a leak protection system comprising an inert gas substitution (130) and venting system (105) in a hatch space (104c) between the inner hatch (104a) and the outer hatch (104b).

10. A method in monitoring gas-tightness or potential leakages in a fuel tank arrangement according to anyone of the preceding claims, characterized in that the inert gas space (101c) pressure and/or temperature is being monitored, and in steady state conditions a change in temperature and/or pressure is considered to indicate a leakage.

11. The method in monitoring gas-tightness or potential leakages in a fuel tank arrangement according to anyone of the preceding claims, characterized in that the tank connection space (100) pressure and/or temperature is being monitored, and in steady state conditions a change in temperature and/or pres sure is considered to indicate a leakage.

12. The method in monitoring gas-tightness or potential leakages in a fuel tank arrangement according to claims 10 and/or 11.

13. The method in a fuel tank arrangement according to any of the preceding claims, characterized in that between the tank connection space (100) and the inert gas space (101c) pressure difference is maintained such that the pressure of the inert gas space (101c) is higher than the pressure in the tank connection space (100).

14. The method in a fuel tank arrangement according to any of the preceding claims, characterized in that the tank connection space (100) pressure is main tained in a proximity to the atmosphere pressure.

15. The method in a fuel tank arrangement according to any of the preceding claims, characterized in that both the tank connection space (100) and the inert gas space (101c) are monitored such that in a case of temperature change both can be ventilated with inert gas and substitute the possible gaseous fuel in said spaces (100, 101c).

16. The method in a fuel tank arrangement according to any of the preceding claims, characterized in that in case of leakage of fuel gas is detected a specific weight separation is used in venting the tank connection space (100) and/or the inert gas space (101c), such that the inert gas being heavier in specific weight than the fuel gas, and the inert gas is led to the bottom of said space (100, 101c) and the lighter fuel gas is substituted to the ventilation (102, 103) connection located at the top elevation position of said spaces (100, 101c).