Patent Description:
More specifically, the invention relates to a tank of the above type (see for example <CIT>), designed and manufactured in particular to allow the containment of light gases at high pressure, such as hydrogen or helium, but which can be used for any application in which it is necessary to obtain a very high held with equally high safety.

In the following, the description will be directed to tanks or containers for high-pressure hydrogen, but it is clear that the description should not be considered limited to this specific use.

One of the major critical issues in the storage of hydrogen gas is the potential embrittlement effect it can cause due to diffusion into the metallic material. This phenomenon can also be related to the pressure level considered for storage.

In particular, carbon and low-alloy steels are currently common structural materials for high-pressure hydrogen storage tanks. The equipment made with these materials, subjected to multiple pressure cycles, is subject to failures due to the mechanism of the so-called hydrogen embrittlement even at room operating temperature.

This phenomenon occurs above all in high-strength steels and less so in low-alloy steels, under hydrogen pressure, and it is amplified if the equipment is subjected to several cycles.

One solution would be to provide a protection inside the tank, to be applied to the metal part to prevent this potential phenomenon, i.e., the application on the internal surface of a suitable polymer, which, at the same time, has the property of significantly reducing the permeation of the hydrogen in the metal support, thus substantially reducing the phenomenon of hydrogen embrittlement, low aging tendency, good cohesion with the metal support and substantial influence of hydrogen on chemical and physical characteristics.

Currently, there are containers or tanks for hydrogen made of aluminum alloys, which are able to contain hydrogen at a pressure of <NUM> bar.

However, these containers do not have sufficient sealing performance for the storage of large volumes of hydrogen, and for long times, with large dimensions, so as to ensure full and continuous availability.

In addition to the above, the tanks according to the prior art do not allow the location of a possible leak, such that, once it has been detected that the tank has leak problems, lengthy and costly checks must be carried out to determine the location of the leak. For this purpose, very expensive devices present on the market are also used. Also, in the event of a leak, the tank often has to be disassembled from where it is. These operations are time-consuming as well as expensive.

It is evident how the industry feels the possibility of having containers capable of containing light gases such as hydrogen or helium, at high pressure.

In light of the above, it is, therefore, an object of the present invention to propose a tank for light gases, as well as for other fluids, in which a high seal is required, which has containment performances superior to those of common tanks according to the prior art.

It is also an object of the present invention to propose a tank that can be safe, allowing rapid detection of any gas leaks or losses in general also considering a possible accumulation system.

It is, therefore, specific object of the present invention a tank for containing fluids and gases, such as hydrogen and the like, comprising a wall, having an external face, facing the outside of the tank, and an internal face, facing the inside of the tank, wherein said wall is arranged on said frame, a first internal lining layer, made of aluminum or other corrosion-resistant material, a support frame, placed between said wall and said first internal lining layer, wherein said wall is arranged on said support frame, and one or more dispersion nets, arranged integrated in said support frame, wherein said one or more dispersion networks disperse the gas contained in the tank in case of leaks between said wall and said first internal lining layer.

Always according to the invention, said support frame may comprise a plurality of strips arranged to form a framework, which identifies a plurality of spacings, and said each dispersion net may be arranged in a respective spacing.

Still according to the invention, said wall may comprise a plurality of housings, and said support frame may comprise a plurality of strips, arranged in said housings.

Advantageously according to the invention, said wall may have one or more through holes or channels, for the gas to escape in case of a leak from the tank.

Further according to the invention, said through holes may have a thread in correspondence with said external face, to which it is possible to connect and fix devices, sensors, control systems, and the like.

Preferably according to the invention, said tank may comprise a second internal lining layer made of polymeric material, such as polyethylene, coupled to said internal face.

Always according to the invention, said dispersion net may be of the "waved mesh" type, and are made of steel, aluminum, or aluminum alloy.

Still according to the invention, said lining material may be a polymer, such as polyethylene, one of the polymers used as a protective lining to prevent or limit the penetration of hydrogen.

It is further object of the present invention a leak detection system, comprising a tank as defined above, a pressure sensor, and a plurality of connecting pipes, wherein each connecting pipe connects said pressure sensor to a through channel, wherein in case of a gas leak occurs near one of said through channels, said gas would be preliminarily diffused through said dispersion net, before reaching said pressure sensor by means of the closest connection pipe, and wherein, based on the connection pipe of which said pressure sensor detects a pressure increase, the area of said tank in which there is a leak can be determined.

It is also object of the present invention a method of lining a tank for a gas, such as hydrogen, urea, and the like, as defined above, comprising the following steps: A. making said housings said through holes or channels on a flat sheet, for making said wall, wherein said sheet is made of aluminum or aluminum alloy; B. performing a calendering and/or forming operation on said sheet, to obtain the shape of the tank; C. applying said frame on said wall, arranging said strips in respective housings; D. applying said dispersion nets on said frame; applying said first internal lining; E. applying said second internal lining made of polymeric material.

Always according to the invention, said step F of applying said second internal lining comprises the following steps: introducing a lining material powder into a tank; applying the lining material on said first internal lining layer; and fixing the lining material to the first internal lining layer of said tank.

Still according to the invention, said step of applying the lining material may comprise the sub-steps of: heating the tank and the lining material contained until it becomes liquid at a first temperature and for a first time interval; moving said tank, so that the lining material adheres to the first internal lining of said tank; cooling said tank, bringing said tank to a second temperature, for a second time interval; and moving said tank.

Advantageously according to the invention, said heating step may take place at a temperature of about <NUM> for a time interval, preferably of about <NUM> minutes.

Further according to the invention, said cooling step may take place at a temperature of about <NUM> for a time interval preferably of about <NUM> minutes.

Preferably according to the invention, said fixing step may comprise the sub-steps of: introducing a gas, such as air and the like, at a first fixing pressure, and at a first fixing temperature; and inserting a gas, such as air and the like, at a second fixing pressure, and at a second fixing temperature lower than said first fixing temperature.

Always according to the invention, said first fixing pressure may be about <NUM> bars and said first fixing temperature is about <NUM>, and said second fixing pressure may be about <NUM> bars and said second fixing temperature is about <NUM>.

In the various figures, similar parts will be indicated with the same reference numbers.

In order to eliminate the threat of hydrogen embrittlement, high-pressure hydrogen contained in a tank can be prevented from contacting the steel pressure tank by installing an aluminum alloy liner that has good permeation resistance of the hydrogen and creates an escape path avoiding the build-up of pressure between the lining and the wall of the tank subjected to high pressure.

With reference to <FIG>, <FIG>, a section of a tank <NUM> for containing hydrogen can be observed, which has various layers. In particular, the layered structure of the same tank <NUM> can be observed, in which the wall <NUM> of the tank <NUM> is provided, a plurality of dispersion nets <NUM>, a support frame <NUM>, a first internal lining layer <NUM>, and a second internal lining layer <NUM>.

The wall <NUM> of the tank <NUM> has an external face <NUM>, which determines the external surface of the tank <NUM>, and an internal face <NUM>, which has housings <NUM>, the function of which will be better described below.

Said housings <NUM> are made as grooves on the inner surface of the wall <NUM>. In some embodiments, these grooves are made by grinding, by means of suitable tools. However, the housings <NUM> can also be made with different methods.

The wall <NUM> of the tank <NUM> is preferably made of carbon steel or a low-alloy material with high resistance, so as to make the tank <NUM> lighter and in any case provided with a high seal.

Through holes or channels <NUM> are provided on the wall <NUM>, arranged spaced preferably but not necessarily evenly over the entire surface of the tank <NUM>. Furthermore, in correspondence with the external face <NUM>, said through holes <NUM> have a thread <NUM>, at which it is possible to connect and secure devices, sensors, or control systems in general. The function of these through channels <NUM> will be discussed below.

The dispersion net <NUM> is interposed between the wall <NUM> and the first internal lining layer <NUM>. Furthermore, each dispersion net <NUM> is delimited by the support frame <NUM> and is integrated therein.

In the embodiment under examination, the dispersion nets <NUM> are of the "waved mesh" type, and are preferably made of steel, or, in further other embodiments, of aluminum. The dispersion nets <NUM> also have the function of avoiding deformation of the first internal lining layer <NUM> made of aluminum or other corrosion-resistant material.

The dispersion net <NUM> allows for facilitating a superficial diffusion of gas leaks, such as hydrogen and the like, in case of leaks.

The support frame <NUM> is made up of a framework of strips <NUM>, which are arranged in said housings <NUM>. The strips identify spacings <NUM> between them.

Said support frame <NUM> is preferably made of aluminum or aluminum alloy. The support frame <NUM> allows the correct coupling between the wall <NUM> of the tank <NUM> and the first internal lining layer <NUM> made of aluminum or other corrosion-resistant material.

The first internal lining layer <NUM> of the tank <NUM> is made of aluminum or aluminum alloy, and consists of a plurality of panels <NUM>, arranged side by side so as to cover the entire internal surface of the tank <NUM>.

The first internal lining layer <NUM> allows a high seal, to allow the use of the tank <NUM> not only for the containment of hydrogen but also for the containment of different types of gas, the mixtures/compounds of the production of urea. In this case, the selected material of the first internal lining layer <NUM> and of the support frame <NUM> would be resistant to the above compounds.

The second lining <NUM> is made of hydrogen-resistant polymeric material such as polyethylene (PE), but other polymeric materials may also be used in other embodiments.

Thanks to the through channels <NUM>, the tank <NUM> can be equipped with suitable control systems. In particular, with reference to <FIG>, it can be observed, schematically, the connection of a leak detection system <NUM>, comprising several sensors <NUM> according to the application and two connection pipes <NUM>. Each of the two connection pipes <NUM> connects the pressure sensor <NUM> to a through channel <NUM>. In the case under examination, only two connection pipes <NUM> are shown and therefore only two through channels <NUM>, but it must be considered that more than two or a multiplicity of connection pipes <NUM> can also be provided, with the respective through channels <NUM>.

In the event that a gas leak occurs, for example, hydrogen, in the vicinity of one of the through channels <NUM>, it would first be diffused through the dispersion net <NUM>, to then reach the pressure sensor through the closest connection pipes <NUM>, closest to the pressure sensor <NUM>. The gas diffusion function of the dispersion net <NUM> makes it possible to avoid excessive gas concentrations for safety reasons.

Based on which connecting pipe the pressure sensor <NUM> detects an increase in pressure on the respective pipe <NUM>, it is possible to determine more precisely the area in which there is a leak. In this way, it is possible to repair the tank <NUM> and in particular the linings, with greater rapidity and precision.

Internally, as mentioned, a second internal lining layer <NUM> is provided, coupled to the first internal lining layer <NUM> made of aluminum or other corrosion-resistant material.

In the embodiment described, the second internal lining layer <NUM> is a hydrogen-resistant polymer, such as polyethylene (PE).

For the realization of the tank <NUM>, the following steps are carried out:.

In relation to the last application step of the second internal lining layer <NUM> in hydrogen-resistant polymeric material, reference is made to <FIG>, <FIG>, <FIG>, <FIG>, which show the tank <NUM> to be internally lined.

The wall <NUM> of the tank <NUM> comprises a delimiting volume V by means of said internal face <NUM>. The tank <NUM> also comprises a first opening <NUM> and a second opening <NUM>, opposite to said first opening <NUM>, closed with a respective closing nozzle <NUM> and <NUM>.

Each closing nozzle <NUM> and <NUM> has an internal surface, respectively indicated with the reference numerals <NUM> and <NUM>, and comprises a fixing flange <NUM> and <NUM>, respectively, for fixing, with suitable screws, to a respective lip of the tank <NUM>.

To arrange the second lining <NUM> inside the tank <NUM>, the latter is opened by removing the first closure nozzle <NUM>, so that it can be inserted into the internal volume V of the lining material powder, which, as mentioned, in general it is a polymer, through the first opening <NUM>. In the present embodiment, the lining material used is a polymer P, such as polyethylene (PE), as the lining material.

Subsequently, the tank <NUM> is closed and sealed again by means of the same closing nozzle <NUM>, by screwing the tightening screws again to the lip of the tank <NUM>.

In a subsequent step, the tank <NUM> is subjected to heating and it is subjected to hot air at a temperature of <NUM>.

At the same time, the tank <NUM> is rotated on itself. This rotation can be achieved by means of a support unit <NUM>, shown in the figure by way of example. Said support unit <NUM> comprises a support unit <NUM> rotatable around a first rotation axis B, and a gripping structure <NUM>, having two arms <NUM>, at the ends of which a respective joint <NUM> is provided. Said support unit <NUM> comprises also two anchoring members <NUM>, each having a first end rotatably coupled to a respective joint <NUM> of the arm <NUM>, and a second end, fixed to said tank <NUM>. The anchoring members <NUM> are configured, in use, to rotate the tank <NUM> around a second rotation axis C, not parallel to the rotation axis B.

In the cooking step, the polymer melts, reaching the liquid state. Furthermore, the liquid polymer P adheres to the first internal lining layer <NUM> of the tank <NUM>, thanks to a rotary movement along two degrees of freedom. This allows an optimal adhesion of the polymer P to the walls of the tank <NUM>.

The cooking or heating time can be around <NUM> minutes.

The hot air to heat tank <NUM> is generated by hot air emitters and has a temperature of about <NUM> (not shown in the figure).

Subsequently, the tank <NUM> is cooled (see <FIG>) and is kept in rotation, while cold air is blown on it. In this way, the solidification of the polymer P and an optimal adhesion of the same to the first internal lining layer <NUM> of the wall <NUM> and to the internal surfaces of the closure nozzles <NUM> and <NUM> are obtained.

In a cooling time of approximately <NUM> minutes, the coating with the polymer P of the first internal lining layer <NUM> of the tank <NUM> is completed.

Subsequently, in order to allow optimal adhesion of the lining polymer P, as mentioned in the first internal lining layer <NUM> of the tank <NUM>, air is introduced at a controlled pressure (i.e., greater than atmospheric pressure).

For this purpose, with reference to <FIG>, a pressure control system <NUM> inside tank <NUM> is installed on the tank <NUM>.

In particular, the pressure control system <NUM> comprises a pressure regulator <NUM>, which is arranged on an access channel of the first closing nozzle <NUM>, and a safety valve <NUM>, which is arranged on the access channel of the second closing nozzle <NUM>.

In other embodiments, said pressure regulator <NUM> and said safety valve <NUM> can also be arranged in different positions.

As can be seen in <FIG>, through the pressure regulator <NUM>, hot compressed air is introduced into the volume V, at a temperature of about <NUM>° and a pressure of <NUM> bar. The high-pressure hot air has the effect of "softening" the lining on the first inner lining layer <NUM> of the tank <NUM>, as well as on the inner surfaces of the first <NUM> and the second <NUM> closing nozzle.

In this way, there is the effect of making the lining polymer P adhere in a uniform manner, even in concave, convex, or interstitial parts of the aforementioned surfaces, in an optimal way, eliminating or limiting the formation of bubbles or uncoated areas, making the second internal lining <NUM> uniform.

The safety valve <NUM> allows any excess air to be vented to maintain the pressure at a specified threshold, which is lower than the pressure value with which the air is introduced through said pressure regulator <NUM>.

In particular, in a preferred embodiment, the pressure regulator <NUM> allows the entry of hot air at a pressure of <NUM> bar, while the safety valve <NUM> is calibrated by a maximum threshold of <NUM> bar for safety.

Subsequently, referring to <FIG>, air enters through the pressure regulator <NUM> at room temperature, therefore typically between <NUM> and <NUM>, at a pressure of <NUM> bar, always calibrating the safety valve at <NUM> bar.

This step of introduction of air at room temperature, therefore colder than the previous step, and at a pressure greater than atmospheric pressure, allows the second internal lining <NUM> to cool down in polymer P, allowing for optimal adhesion. In other words, the second internal lining <NUM> is "kept in adherence" on the first internal lining layer <NUM> of the tank <NUM> and on the internal surface of the closing nozzles <NUM> and <NUM>, to avoid any new formation of bubbles or imperfections in the internal second lining layer <NUM>.

Subsequently, the closing nozzles <NUM> and <NUM> are removed by unscrewing the screws of the flanges.

The proposed lining system has several advantages. Indeed, hydrogen, while being an extremely efficient and environmentally friendly energy resource, presents some significant challenges when it comes to its transportation. The solution according to the invention, thanks to the structure considered and the materials used, can be applied to both gas pipelines and pipes, making the transport of hydrogen safer and more efficient.

Pipeline steels play a significant role in the transport of hydrogen. These materials, while extremely strong and durable, can be vulnerable to corrosion and wear, especially when used to transport gases such as hydrogen and/or mixtures of hydrogen and methane. The lining system according to the invention can be applied directly to the steel pipes, providing an additional protective barrier that can considerably extend their life span and keep their performance intact.

Another aspect to consider concerns the safety of pipeline operations. The handling and transport of hydrogen can involve significant risks, due both to the nature of the gas itself and to the complex operating conditions. The lining solution according to the invention, through its sophisticated design and material selection, can help improve the safety of pipeline operations, reducing the risk of leaks and failures while ensuring a constant and uninterrupted hydrogen flow.

Furthermore, the lining solution according to the invention can be used to eliminate or delay the effects of hydrogen on pipelines. Hydrogen, in fact, can cause the embrittlement of the steel and the growth of cracks, phenomena that can compromise the structure of the pipes or tanks, and lead to malfunctions or breakdowns. The proposed lining can act as a protective barrier, preventing pressurized hydrogen from coming into direct contact with the steel and thereby causing structural damage. In this way, the solution according to the invention can not only extend the life of the pipes, but can also contribute to maintaining the efficiency and reliability of the hydrogen transport system.

An advantage of the present invention is that of proposing a tank internally lined in aluminum and polymer, for maximum protection, which allows to withstand a high pressure, even for very light gases such as hydrogen or helium, and allow the detection of any gas leaks.

A further advantage of the present invention is that of limiting possible concentrations of gas in the event of leaks.

Claim 1:
Tank (<NUM>) for containing fluids and gases, such as hydrogen and the like, comprising
a wall (<NUM>), having an external face (<NUM>), facing the outside of the tank (<NUM>), and an internal face (<NUM>), facing the inside of the tank (<NUM>),
a first internal lining layer (<NUM>), made of aluminum or other corrosion-resistant material,
a support frame (<NUM>), placed between said wall (<NUM>) and said first internal lining layer (<NUM>), wherein said wall (<NUM>) is arranged on said support frame (<NUM>), characterized by
one or more dispersion nets (<NUM>), arranged integrated in said support frame (<NUM>), wherein said one or more dispersion networks (<NUM>) disperse the gas contained in the tank (<NUM>) in case of leaks between said wall (<NUM>) and said first internal lining layer (<NUM>).