DEVICE AND METHOD FOR FILLING A TANK

The present invention relates to a device and a method of filling fuel tanks.

The invention more particularly relates to a device for filling a vehicle tank with a liquefied gas fuel at a cryogenic temperature, in particular for filling of cryogenic tanks of liquid hydrogen under pressure, the device comprising a reservoir storage source of gaseous fuel in a liquid state at a cryogenic temperature, a tapping line liquid fuel comprising a pump, the tapping line comprising an upstream end connected to the source reservoir and a downstream end comprising a fitting for connection to a tank to be filled,

The and fuel gas including hydrogen can be stored in different forms: as a pressurized gas (for example to 700bar) or in liquid form (pressurized or non-pressurized).

Storage of hydrogen liquid to a pressurized cryogenic temperature (cryogenic compressed hydrogen), for example, at a pressure of 350bar, allows increased density of stored fuel with respect to a non-pressurized storage in liquid form. This technology has however the disadvantage of requiring a highly efficient heat insulation. Furthermore, this technology requires processing the unavoidable vapors produced by the vaporization of a portion of the liquid in the entire system.

To perform the storage vessel, the temperature of the fluid is to be controlled and must not exceed a temperature threshold (e.g. 50K).

The filling stations compressed hydrogen cryogenic commonly use a pump to draw liquid from a reservoir cryogenic source.

Before making a filling the pump and pipes of the circuit are to be cooled. This is carried out by circulating the fluid or by pumping fluid which is returned directly in the source tank. Cold The operation generates a spray of liquid. The product gas is returned to the source reservoir and increases the pressure thereof. Even when the pump and the circuit are at the required temperature, of the liquid vaporizes during operation of the pump. The amount of liquid vaporized varies in particular according to the thermal performance of the pump and the circuitry and the efficiency of the pump. The gas thus generated is transferred to the reservoir causing its pressure build-up. In cases of excessive pressure a portion of the gas is to be released to the outside, for example via a safety valve. In addition to the economic consequences, rejection of fuel gas into the atmosphere Security problems.

In standby mode (between refilling), the pump and the fluid channels are is maintained at cryogenic temperature, is brought to ambient temperature. Furthermore, the heat input on the source reservoir produce gas by vaporization of a part of its liquid to a determined rate. The gas for vaporization product gradually increases the pressure in the source reservoir.

When it is desired to perform a filling of liquid under pressure (for example hydrogen cryogenic compressed) the temperature of the pumped liquid provided to the tank to be filled must be less than a predetermined threshold pressure and greater than a predetermined threshold. The temperature available at the output of the pump is strongly dependent of the efficiency of the pump and the operating conditions of the device.

An object of the present invention is to overcome all or part of the disadvantages of the prior art raised above.

To this end, the filling apparatus according to the invention, further according to the generic definition that gives the preamble above, is essentially characterized in that the draw-off pipe comprising, downstream of the pump, a portion of bypass passing within the source reservoir and comprising a heat exchanger immersed in heat exchange for carrying the pumped liquid and the liquid stored in the source reservoir, the tapping line comprising a valve arrangement (s) bypass configured to control the relative proportions of the pumped fluid does not passing and passing in the branch-off portion, to control the temperature of the withdrawn liquid being filled and that the filling device comprises a cryo-cooler connected to the source reservoir to selectively liquefying the gas present in the source tank, in particular of the vapors produced by the heat exchanger of the leg portion and those generated by the stake and keeping cold of the pump.

Furthermore, embodiments of the invention may include one or more of the following features:

-the downstream end of the tapping line includes a sensor for measuring the temperature of the liquid, the filling device comprising an electronic control system connected to the temperature sensor and, on the other hand, to the valve arrangement (s) bypass, the electronic logic is configured to receive the temperature information measured by the temperature sensor and, on the other hand, controlling the bypass valve (s), to control the temperature of the liquid to the downstream end of the tapping line at a value determined on mitigating the distribution of the pumped liquid passing between the channels and which fail to enter the branch-off portion,

-the device comprises upstream a return line having a first end connected to an outlet of the pump and a second end connected to the source reservoir to form a loop fluid return pumped to the source reservoir provide cold of the pump and/or in order to return the reservoir source of the vaporized gas in the pump,

-the source tank comprises an inner wall interposed between the immersed heat exchanger and the suction port of the pump, to avoid or limit the disturbance of the NPSH to the suction of the pump,

-the device comprises a return line provided with a downstream valve, the return line downstream having a first end connected to the downstream end of the tapping line and a second end connected to the source reservoir,

-the second end of the cold line of the pump is split into two parallel lines connected respectively to the top and bottom of the source reservoir, the two parallel lines being provided with respective valves,

-the electronic logic is configured to receive information from pressure measured by the pressure sensor and, on the other hand, control the switching on or off of the cryo-cooler, to regulate the tank pressure source,

-the cryocooler thermodynamic cycle technology supports a Stirling, Gifford [...], Brayton or Vuilleumier.

The invention also relates to a method for filling a vehicle tank with a liquefied gas fuel at a cryogenic temperature, especially liquid hydrogen, by means of a filling device according to any of the features above or below, wherein the reservoir contains a gaseous fuel source in a liquid state at a cryogenic temperature between 20.2 30.4 K and K and a pressure of between 1 and 9 bar absolute and in that the exit temperature of the fluid downstream of the pump is maintained at a predetermined target temperature between 21K and 50K, by controlling the relative proportions of fluid pumped passing and passing does not in the branch-off portion.

In other possible features:

-when the pressure in the source tank reaches a determined high value between 6 and 9 bar absolute bar absolute and preferably equal to absolute 6bar, at least a portion of the pumped liquid is cooled in the heat exchanger immersed in the leg portion,

-the method comprises a step of regulating the pressure and/or temperature in the source tank to maintain the pressure of the fluid at the inlet of the pump to a predetermined value above the saturation vapor pressure of said fluid,

-the method comprises a step of starting a filling comprising a switch-on of the pump and, at least in the range of thirty minutes preceding the operating the pump, the pressure within the tank source is increased by a value comprised between 0.5 and 1 bar absolute bar absolute to temporarily increase the pressure head above the saturation vapor pressure of the fluid,

-the increase of pressure for temporarily increasing the margin of pressure above the saturation vapor pressure of the fluid is performed by taking fluid from the reservoir source, by heating the fluid is removed from and in the feeding back in the source tank,

-at the end of filling of the tank, the pump is stopped and at least a portion of the gas generated by vaporization of the liquid in the source tank is reliquefied by the cryocooler,

-at least a portion of the vaporized liquid in the filling device is returned to the source reservoir,

-the filling device comprises a sensor for measuring the pressure in the source tank and in that the cryocooler is controlled to perform a liquefaction of the tank vapor source in response to a predetermined pressure level measured by the pressure sensor,

-the cryocooler is turned on only when the pump is switched off, to limit the electrical power of the device.

The invention may also relate any device or alternative method comprising any combination of the above features or below.

Other features and advantages shall become apparent from the following description, made with reference to the drawing represents, in single partial schematic and the structure and operation of a possible exemplary embodiment of a filling apparatus according to the invention.

The example filling device shown includes a reservoir 16 source that stores fuel gas, for example hydrogen in a liquid state at a cryogenic temperature. Source The reservoir 16 contains a quantity of liquid in equilibrium with a vapor phase. The fluid is in the tank at a temperature of from 30.6 20.2 K and K and a pressure of for example between 1 and 9 bar absolute.

The device comprises a duct tapping 9 (preferably thermally insulated) comprising a pump 8. The conduit tapping 9 comprises an upstream end connected at the bottom of the tank source 16 and a downstream end comprising a fitting 11 to be selectively connected to a reservoir 15 to be filled.

The device typically includes a conduit 6 upstream return having a first end connected to a degassing outlet of the pump 8 and a second end connected to the reservoir source 16 to form a loop-back pumped fluid to the reservoir source 16 provide cold of the pump 8 and/or in order to return the reservoir 16 source of the vaporized gas in the pump 8. As shown, the second end of the duct 6 for cold of the pump 8 can be split into two parallel lines connected respectively to the top and bottom of the reservoir 16 source, the two parallel lines being provided with respective valves 160,26 respectively to allow return of gas and liquid source to the reservoir 16, while optimizing controlling pressure in the reservoir 16 source

180 A isolation valve may be provided upstream of the pump 8.

In one advantageous feature, the pipe tapping 9 comprises, downstream of the pump 8, a leg portion passing within the reservoir 16 and source comprising a submerged heat exchanger 3 for heat exchange liquid being pumped and the liquid stored in the tank source 16.

Furthermore, a system of valves 13 and 14 is provided on the bypass line tapping 9 to control the relative proportions of the pumped fluid passing and passing in the portion does not bypass 3. That is, the liquid through downstream within the tapping 9 and provided to the tank 15 consists of the sum of the fractions of fluid which has flowed in the two parallel branches (respectively in the reservoir 16 source and out of the reservoir 16 source). The distribution of the fluid in the exchanger 3 and/or submerged out of the tank 16 permits control of the temperature downstream of the conduit 9 withdrawal or cooling as necessary, any portion of the fluid pumped by heat exchange with the liquid stored in the tank source 16.

As shown, the distribution may be produced by two valves 13 and 14 controlled bypass located respectively on two parallel branches. Of course, alternatively a three-way valve or any other system of distribution may be contemplated.

Furthermore, the downstream end of the bleed line 9 may include a sensor 19 for measuring the temperature of the liquid and the filling device can include logic 20 electronic control connected to the temperature sensor 19 and, on the other hand, the system to bypass valves 13 and 14.

Preferably, the electronic logic 20 is configured to receive the temperature information measured by the temperature sensor 19 and, on the other hand, controlling the bypass valves 13 and 14 to control the temperature of the liquid to the downstream end of the pipe 9 to a predetermined value.

As shown, a sensor 29 for measuring the pressure in the downstream portion of the conduit 9 bleed may also be provided and can be connected to the control logic 20.

For cooling of the pipe tapping 9 prior to pumping and to not losing gas, the device may also include a downstream return line 18 provided with a valve 28. The 18 downstream return line having a first end connected to the downstream end of the bleed line 9 and a second end connected to the source tank 16. Finally, a valve 39 isolation may be provided at the downstream end of the bleed line 9, before the connecting part 11.

In one advantageous feature, the device also comprises a cryo-cooler 5 source connected to the reservoir 16 for liquefying gas in the source tank 16. The cryo-cooler 5, for example mounted on top of the source reservoir 16, may include a condenser of Stirling technology, Gifford McMahon, Vuilleumier or Brayton. The cryo-cooler 5 includes a gas inlet and an outlet to be liquefied of liquefied gas which are connected to the storage volume of the container source 16. Alternatively, the cryo-cooler 5 can be installed directly in the reservoir 16 source.

As shown, a sensor 50 in pressure in the tank source 16 can be connected to the cryo-cooler 5 and/or to the electronic logic 20 to control the cryocooler 5 based on the level of pressure measured in the source reservoir 16. By [...] a portion of the gas phase decrease the pressure in the source tank 16.

The reservoir 16 source may also include a safety valve 36-releasing pressure gases (in the event of failure of the device described below or above).

An example of use will now be described schematically.

When the device is awaiting (between refilling spaced e.g. a day), the pump 8 and its extraction circuit are at room temperature. The fluid is to the equilibrium between a vapor phase and a liquid phase at a temperature corresponding to the saturation temperature of the fluid.

Before making a filling, the valve isolation 180 upstream of the pump 8 is open (to cool the pump and its circuit) conventionally by re-circulating the liquid pumped into the tank 16 source via line 6 for cold.

When the pump 8 is at the required temperature (temperature at or near the temperature of the liquid phase in the vessel source 16, the filling operation can begin. The required temperature is measured, for example by temperature sensors 80,81 and 82 arranged at the inlet and/or outlets of the pump 8. The pump 8 can then be started.

The temperature of the liquid to the downstream outlet of the pump 8 is dependent in particular isentropic efficiency of the pump 8.

For example, for a pump 8 generating increasing pressure of 300 [...] (bar absolute), the inventors have calculated that, when liquid hydrogen at a temperature of 21.7K is pumped by a pump 8 having an isentropic efficiency of 80%, the pressurized fluid reaches a temperature of about K 41,8 to the outlet of the pump 8 (temperature rise of about 20K).

Preferably, the electronic logic 20 receives the information from the sensors 80, 81, 82 measurement temperature of the cold of the pump 8 to control the efficiency of the pump 8. The sensors 80, 81, 82 can be arranged respectively, at the inlet of the pump 8, at the downstream outlet of the pump 8 and at the upstream output of the pump 8 in the return line 6.

A temperature sensor 81 located at the downstream outlet of the pump 8 makes it possible to control the temperature of the fluid pumped into the line tapping 9, in particular for detecting losses pump 8.

In some circumstances, the filling of a tank 15 requires a liquid having a predetermined temperature, e.g. 50K.

In start of pumping a liquid temperature of not more than 50K is obtained downstream of the conduit 9 tapping.

The vaporized gas in the circuit (in the pump 8 in particular) is returned to the tank source 16. This causes an increase in pressure and temperature within the reservoir source 16. In the event of an increase of temperature and excessive pressure this can disrupt not only the tapping operation but also the temperature of the liquid provided to the tank 15 filled.

The inventors have determined that, when the pressure of the source reservoir exceed a predetermined level, for example 4.2 [...] (bar absolute), the temperature provided to the tank 15 to fill may exceed 50K downstream of the conduit 9 tapping with a pump 80% isentropic efficiency.

In order to prevent this, the control logic 20 can control the opening of the bypass valve 14 to force a portion of the pumped liquid to pass through the exchanger 3 lowered into the tank source 16. The fluid cooled in the exchanger immersed 3 is mixed downstream with the relatively hotter fluid which has not passed in the exchanger immersed 3.

Measurement 19 the temperature of the fluid may allow the control logic 20 control the degree of opening of the bypass valves 13 and 14 to control said downstream temperature.

In particular, the temperature of the gas can be controlled and maintained within a range between the temperature of the liquid in the tank source 16 most a few degrees K (for example one or two degrees) and, on the other hand the temperature of the liquid to the outlet of the pump 8.

At the end of the pump (for example when the measured pressure 29 on the pipe 9 discharge reaches a predetermined value), the pump 8 can be stopped.

The valve 160 of the line which returns the cold gas from the pump 8 to the reservoir 16 can be closed when all the gas present in the circuit have been evacuated to the reservoir source 16.

While simple in structure and inexpensive, the device according to the invention thus allows to efficiently control the temperature of the fluid that fills the tank 15, without consideration of the efficiency of the pump 8.

Indeed, the user can in particular sets (e.g. via the control logic 20) the temperature of the fluid that fills the tank 15.

The device is also capable of securing the operation of the pump (to avoid cavitation).

The height of an absolute net charge to the suction of the pump NPSH ("NPSH" for "Net Positive Suction Height" in English) is the value of available pressure to the inlet of the pump above the value of saturation vapor pressure of said liquid. To avoid cavitation, the available NPSH is to be at least equal to the required NPSH of the pump (specified by the manufacturer of the pump 8).

The NPSH is a function:

-the level of pressure in the reservoir 16 source,

-the value of the saturation vapor pressure of the fluid,

-of the load losses in the drawing circuit to the inlet of the pump 8 (line 181),

pressure-the height of the liquid between, on the one hand, the upper surface of the liquid in the reservoir 16 and, on the other hand, the inlet of the pump 8.

In the case of hydrogen, due to its low density, the influence of the pressure head is negligible (in particular for horizontal tanks). The proper feed (NPSH required less than available NPSH) of the pump is into the liquid is cooled to the inlet of the pump, that is to increase the available NPSH.

Advantageously, this may be done by slightly increasing reservoir pressure and selectively 16. Indeed, with an increase in the pressure in the reservoir 16 source, before the liquid/gas mixture returns to a new state of balanced to a new equilibrium temperature defining a new saturation pressure, the temperature of the liquid is momentarily less than its saturation temperature.

Therefore, before startup of the pump 8, preferably the pressure in the reservoir 16 source is increased. For example, the pressure increase is carried out up to a pressure value function of the required NPSH of the pump 8 and thermo hydraulic performance of the suction line 181. Preferably the pressure increase is performed in the previous time a filling (and preferably in the thirty minutes prior to an filling).

This pressure increase may be accomplished using the generated vapor when cold of the pump 8 (see the description above). In the case where the pump 8 is already cooled, the pressure increase may be formed, for example by taking fluid from the reservoir source 16, by heating the fluid and then feeding back in the source tank 16. This heating can be carried out in a heating exchanger arranged for example in a bypass of the conduit 6 260 and accessible via a return valve.

By minimizing the load losses and the heat input in the circuit, can be minimized the pressure level necessary to reach a sufficient NPSH required by the pump 8.

While simple in structure and inexpensive, the device allows thereby ensuring a sufficient NPSH for the pump 8.

Depressurizing the reservoir 16 A source followed by a pressurizing is an efficient way of performing priming of the pump 8. However, this can result in a substantially producing vaporized gas (gas " [...] -off" in English).

Advantageously, the device comprises a cryo-cooler 5 which is provided for (re) liquefying a portion of the gas phase in the tank source 16.

This lowers the pressure and thus the temperature within the reservoir source 16. This makes it the reservoir source 16 ready for a filling operation with a sufficient NPSH, without excessive production of vaporized gas.

The gas liquefaction provides an additional advantage. Indeed, the liquefaction can avoid releasing and lose pressure gases.

The fluid in the reservoir 16 source receives heat energy from the outside and in particular, of the extraction circuit, such as the immersed exchanger 3. The caloric input causes sprays of fluid and thus a pressure increase. The cryo-cooler 5 eliminates the atmosphere to relieve excess of the product gas.

Preferably, at least one partition 4 is provided within the tank to prevent vaporization bubbles formed at the immersed exchanger 3 from migrating to the orifice feeding the pump 8. As shown, this partition 4 may extend for example from the bottom of the tank 16 source and a portion of the internal height of the tank 16. The partition 4 (or the walls are there are more than one) are interposed between the immersed exchanger 3 and the orifice of the reservoir 16 source connected to the inlet of the pump 8.

Furthermore, this partition 4 can be made of a material with a high thermal conduction coefficient (and can be pierced by location), to form further heat exchanger for rendering the temperature within the reservoir source 16. The or these heat exchangers constituted by the wall or walls 4 may, for example, avoid temperature stratification within the reservoir source 16. The or the partitions 4 can also slow the pressure rise within the reservoir 16.