FR3052228A1 - COMPOSITE TANK FOR STORING GAS UNDER PRESSURE - Google Patents

Abstract

Composite tank for storing pressurized gas, in particular hydrogen, comprising an inner envelope (2) sealed and an outer envelope (3) of mechanical reinforcement composite material arranged around at least a portion of the inner envelope (2) and comprising a thermosetting or thermoplastic resin, wherein the resin constituting the outer casing (3) comprises at least one additive (4) for increasing the thermal conductivity of said outer casing, characterized in that the additive comprises carbon-based particles having a thickness of between 0.5 and 10 nanometers and a length of between 0.5 nanometers and 10 micrometers.

Description

The invention relates to a composite tank for storing gas under pressure. The invention relates more particularly to a composite tank for the storage of pressurized gas, in particular hydrogen, comprising a sealed inner envelope and an outer mechanical reinforcing outer layer of composite material arranged around at least a part of the envelope. internal and comprising a thermosetting or thermoplastic resin, wherein the resin constituting the outer casing comprises at least one additive for increasing the thermal conductivity of said outer casing.

The tanks or composite bottles (type IV in particular) include an inner casing (plastic liner or very thin metal) ensuring gas tightness. This inner envelope is coated with a composite reinforcement (fibers embedded in a resin). In the case of a plastic liner, two modes of failure are possible in case of fire (when no thermal fuse is installed or in case of fuse failure): - bursting of the tank (if the degradation of the reinforcement composite is too fast there loss of mechanical properties while the liner still provides sealing), - a leakage of gas by the body (if the liner melts while the composite reinforcement still withstands the internal pressure).

Composite bottles are generally tested in a "bonfire" type of fire (for example according to standard NF EN 12245 in the case of transportable composite bottles).

Most bottles tested at their service pressure burst, leakage through the body occurring only below a certain pressure threshold.

Several solutions have been devised to avoid this bursting and favor the second mode of failure (controlled leakage).

A known solution is to use a thermal fuse (TPRD) which melts when the temperature increases and opens a passage to drain the gas. Another known solution uses elements delaying the exposure to fire: metal formwork, intumescent paints ... (see for example W02004020544A2).

Another solution is to provide a bottle structure that transmits the heat of the fire to the liner (see FR3028916A1). This solution makes the structure of the tank more complex and expensive.

JP11230347A2 and EP1328754A disclose tanks comprising heat loads for dissipating heat. These solutions are however unsuitable to reduce the risk of explosion.

An object of the present invention is to overcome all or part of the disadvantages of the prior art noted above. For this purpose, the reservoir according to the invention, moreover, in accordance with the generic definition given in the preamble above, is essentially characterized in that the additive comprises particles based on carbon having a thickness of between , 5 and 10 nanometers and a length of between 0.5 nanometer and 10 micrometers.

Furthermore, embodiments of the invention may include one or more of the following features: the additive comprises graphene particles and in particular graphene nanofiles, the additive comprises carbon nanotubes; Carbon-based particles are uniformly distributed in the resin, the carbon-based particles are distributed in the resin with distinct concentrations according to the thickness of the outer shell, the resin constituting the outer shell comprises mass proportion of particles based on carbon of between 0.1% and 10%, the sealed inner envelope is composed of plastic material, the outer mechanical reinforcing envelope comprises a thermosetting or thermoplastic resin in which fibers are embedded. reinforcement comprising at least one of: carbon fibers, fiberglass basalt fibers, - the wrapper e internal waterproof is composed of polyethylene material or polyamide. The invention may also relate to any alternative device or method comprising any combination of the above or below features. Other features and advantages will appear on reading the following description, with reference to the figures in which: - Figure 1 shows a schematic and partial sectional view of an exemplary possible embodiment of the reservoir according to the FIG. 2 illustrates an enlarged detail of the section of the tank of FIG. 1.

The composite tank 1 of pressurized gas shown by way of non-limiting example comprises an inner shell 2 ("liner"), for example of generally cylindrical shape, defining a gas storage volume. The inner envelope 2 is for example made of plastic, in particular a polymer (for example polyethylene, polyamide or any other suitable material). The inner casing 2 preferably has an opening at one of its ends.

An outer casing 3 of mechanical reinforcement is disposed on the outer surface of the inner casing 2. The protective envelope 3 comprises, for example, one or less of: an epoxy resin or a vinylester or thermoplastic resin, a mixture of a resin mentioned with carbon or glass fibers, basalt or fillers of carbon black. This outer casing 3 is for example applied to the inner casing 2 by filament winding.

This outer envelope 3 of mechanical reinforcement has for example a thickness of between 1 and 90 mm and preferably between 2 and 60 mm. The thickness may vary in particular depending on the operating pressure or the diameter of the tank.

Optionally, an intermediate layer (not shown) (polyamide or other optionally filled with fibers) may be provided between the inner shell 2 and the outer shell 3.

According to an advantageous characteristic, the resin of the outer shell 3 contains additives for increasing the thermal conductivity of the final composite (in the direction transverse to the fibers). According to this structure, the thermal conductivity through the thickness is increased and the heat is propagated more rapidly through the composite reinforcement. The additive comprises, for example, carbon-based particles having a thickness of between 0.5 and 10 nm. and a length of between 0.5 nanometers and 10 micrometers. These particles may advantageously be made of graphene. This makes it possible in particular to increase by a factor of two to ten the thermal conductivity through the thickness of the outer envelope reinforcement 3 and therefore the composite with respect to the conventional tanks Therefore, when the tank 1 is exposed to a fire of type "bonfire" and initially at a pressure lower than its maximum operating pressure, the only possible behavior is leakage by the body (even without fuse or other protective equipment). Indeed, tests or simulations have demonstrated that this increase in the thermal conductivity of the composite reinforcement ensures the transfer of heat through the thickness that melts the inner shell 2 while the outer shell 3 is always capable of supporting the maximum operating pressure of the tank 1. The pressurized gas contained in the tank 1 can then escape through the composite.

This greatly increases safety: although uncontrolled, leakage through the body induces much smaller safety distances than a burst or a flashlight from a fuse (TPRD).

An additional effect of this structure is the greater ability of the tank to evacuate heat to the filling (or cold during a racking). This makes it possible to increase the filling / emptying rates of the tank without affecting the safety of the tank 1.

In addition, the addition of these additives in the resin makes it possible to limit the exothermic reaction (limit the temperature) during polymerization of the resin by evacuating the calories. The incorporation of these additives also prevents potential damage to the resin during its crosslinking by reducing the amount of cracks and are porosity rate. Due to less cracking of the part produced, the damage to the outer casing 3 is limited (for example during an impact). The outer casing 3 thus has a lower permeation and a lower aging rate. effect of environmental conditions.

Likewise, thanks to the additives, it is possible to vary the electrical resistivity of the outer shell 3 (of conductor insulating behavior). The integration of these additives improves, for the resin (especially epoxy), the coefficient of stress intensity of 70% compared to conventional tanks. This stress intensity coefficient is the level from which a stress propagates in the structure (the crack propagation phenomenon is well known for epoxy resins). This makes it possible to limit damage, especially mechanical damage.

In the case of a thermoplastic resin (of the polyamide 6 type for example), this presence of additives improves the tensile rigidity of the outer shell 3 by up to 50% relative to the known structures (in particular with 10% of graphene mass in the resin of the outer shell 3).

These improvements in the mechanical performance of the outer casing 3 delay (in the case of a bonfire) the degradation of the structure of the tank 1. This allows time to allow the heat to propagate to the inner casing 2 to melt it without bursting.

The structure of the invention therefore improves both the rate at which the heat propagates towards the internal envelope 2 (with a view to its melting) and the mechanical performance of the reservoir.

The additives or fillers used may be graphene nano sheets ("GNP" for "Graphene Nano Platelets") or carbon nanotubes ("CNT" for "Carbon Nano Tubes", that is to say a winding of a graphene sheet on itself).

The GNP graphene nano sheets preferably have a thickness of between 0.5 and a few nanometers. The carbon nanotubes have diameters of preferably between 0.5 and 10 nm and a length of up to a few micrometers.

The distribution of the additives is preferably uniform in the resin.

This is for example implemented via a plasma process (for example made by the company "Haydale") to functionalize graphene and obtain a better homogeneity of the mixture with the resin.

The concentration of additives in the resin is preferably between 0.1% and 10% (mass proportion of additives, also called fillers, in the resin). It is possible to use an identical concentration throughout the winding of the outer shell 3 or different concentrations depending on the thickness.

It may also be possible to provide such additives in the inner casing 2 as well.

These additives are thermally conductive fillers but also increase the mechanical properties of the outer shell 3 (breaking stress, rigidity and propagation of defects).

The synergy of these two properties improves the fire resistance of the tank and thus the safety of the users.

Claims (9)

Composite tank for storing pressurized gas, in particular hydrogen, comprising a sealed inner envelope (2) and an outer mechanical reinforcing outer shell (3) arranged around at least a part of the composite inner casing (2) and comprising a thermosetting or thermoplastic resin, wherein the resin constituting the outer casing (3) comprises at least one additive (4) for increasing the thermal conductivity of said outer casing, characterized in that additive comprises carbon-based particles having a thickness of between 0.5 and 10 nanometers and a length of between 0.5 nanometers and 10 micrometers. 2. Tank according to claim 1, characterized in that the additive comprises graphene particles and in particular nano-sheets of graphene. 3. Tank according to claim 1 or 2, characterized in that the additive comprises carbon nanotubes. 4. Tank according to any one of claims 1 to 3, characterized in that the carbon-based particles are distributed uniformly in the resin. 5. Tank according to any one of claims 1 to 3, characterized in that the carbon-based particles are distributed in the resin with distinct concentrations according to the thickness of the outer casing (3). 6. Tank according to any one of claims 1 to 5, characterized in that the resin constituting the outer casing (3) comprises a mass proportion of particles based on carbon of between 0.1% and 10%. 7. Tank according to any one of claims 1 to 6, characterized in that the inner casing (2) sealed is made of plastic. 8. Tank according to any one of claims 1 to 7, characterized in that the outer casing (3) of mechanical reinforcement comprises a thermosetting or thermoplastic resin in which are embedded reinforcing fibers comprising at least one of: carbon fibers, fiberglass basalt fibers. 9. Tank according to any one of claims 1 to 8, characterized in that the inner casing (2) sealed is made of polyethylene material or polyamide.