System for converting a product

Abstract

The present invention relates to a system for processing a product, the product being in a gaseous state at a pressure of 1 bar and a temperature of 283 K, the system comprising: at least one liquid product reservoir (8); a main circuit (10) for extracting a main product in liquid form from said liquid product reservoir (8); a recovery circuit (12) comprising at least one thermal compressor (13) configured to at least partially compress the gas by increasing the temperature of the gas or an intermediate agent such as a metal hydride by means of a low temperature source and a high temperature source, and a transfer means for transferring a recovery product resulting from evaporation in a liquid product reservoir (8) to one of the at least one thermal compressor (13), wherein the low temperature source of at least one of the thermal compressors (13) is configured to receive low temperature energy from the main circuit (10). The present invention also relates to a process for converting the product.

Description

[Technical Field]

[0001] SYSTEMS AND PROCESSES FOR THE CONVERSION OF LIQUID PRODUCTS TO GAS PRODUCTS FIELD OF THE INVENTION The present invention relates to systems and processes for the conversion of liquid products, particularly liquid dihydrogen.

[0002] With the strong growth in low-carbon solutions for mobility and the transport of goods and passengers, dihydrogen appears to be a promising fuel. When used in vehicles with a fuel cell and electric motor, it could potentially replace the use of fossil fuels or the batteries commonly used to power the electric motor.

[0003] Due to its low density in gas form, dihydrogen is sometimes stored in liquid form to save space. In some cases, it must then be evaporated and compressed to pressures of around 350 or 700 bar before it can be used as a fuel.

[0004] To remain in a liquid state at atmospheric pressure, hydrogen must be maintained at a temperature below 20 K. Because this temperature is significantly lower than ambient temperature, some of the liquid hydrogen will inevitably evaporate, a phenomenon known as "boil-off."

[0005] The hydrogen resulting from boil-off is produced in small quantities at low pressures, making it difficult to recover economically. In most cases, this hydrogen is released into the atmosphere, where it is lost. These losses can amount to up to 1% of the amount of liquid hydrogen stored per day. Therefore, there is particular interest in finding solutions to recover this hydrogen.

[0006] WO 2005068847 and WO 2015036708 propose evaporation recovery systems, where the energy consumed is optimized by a heat exchanger placed in the evaporation circuit. However, these systems consume too much energy.

[0007] One object of the present invention is to propose a system for processing a product, said product being in gaseous state at a pressure of 1 bar and a temperature of 283 K, in which the gaseous products resulting from the boil-off are recovered by optimizing the energy and / or material consumption.

[0008] The object of the present invention is to at least partially meet the aforementioned objectives by proposing a conversion system that allows the gaseous product resulting from the boil-off to be compressed using the cryogenic energy stored in the product that is liquefied at low temperature. To this end, the invention proposes a system for converting a product, said product being in the gaseous state at a pressure of 1 bar and a temperature of 283 K, said system comprising: at least one liquid product reservoir; a main circuit configured to extract a main product in liquid form from a liquid product reservoir; a recovery circuit comprising at least one thermal compressor configured to at least partially compress a gas or an intermediate agent such as a metal hydride by raising the temperature of the gas by means of a low temperature source and a high temperature source, and transfer means for transferring a recovered product resulting from evaporation in a liquid product reservoir to one of the at least one thermal compressor, wherein the low temperature source of at least one of the thermal compressors is configured to receive low temperature energy from the main circuit.

[0009] Thanks to these measures, the recovered products resulting from the boil-off phenomenon can be compressed to pressure levels that make them recoverable with low energy consumption.

[0010] Further features include: the main circuit may comprise at least one evaporator and transfer means for transferring the main product in liquid state from the liquid product reservoir to one of said at least one evaporator, thereby utilizing the cryogenic energy released by the main product as it evaporates; the cold source of at least one of the at least one thermocompressor may comprise a cold circuit configured to pass a heat transfer fluid thermally connected to the evaporator, which is a simple and effective mode for realizing the invention; the cold source of at least one of the at least one thermocompressor may comprise a cold circuit configured to pass the main product, thereby optimizing the use of cold energy stored in the liquefied main product; at least one high temperature source of the at least one thermal compressor can be thermally connected to ambient air, which is an energy-efficient high temperature source; -The recovery circuit is at least one first thermocompressor, the cold source of which is configured to receive cold energy from said main circuit and the hot source of which is thermally connected to ambient air; and at least one second thermal compressor downstream of the at least one first thermal compressor with respect to the transfer of the second gaseous product, the cold source of which is configured to receive cold energy from the main circuit or from ambient air, and the hot source of which is thermally connected to a waste hot source or an electric heating source; - allows achieving a high level of compression of the recovered product while optimizing energy consumption, At least one thermocompressor may be a multi-stage type thermocompressor comprising an upstream source, a target and at least one group of reservoirs each comprising at least two reservoirs, said multi-stage type thermocompressor comprising means for heating and cooling the contents of each reservoir connected respectively to a hot source and a cold source, each group comprising: - transfer means for transferring gas directly from said upstream source to each reservoir and directly from each reservoir to said target; - bidirectional transfer means for each reservoir of the group, allowing direct gas transfer between this reservoir and at least one other reservoir of the group; In this way, the gas that is the recovered product in the context of the present invention can be compressed to high pressures by thermal compression, thus avoiding the problems of noise and wear of mechanical parts while enabling an energy-efficient process. the multi-stage thermocompressor can include two groups of reservoirs, thus optimizing its operation and in particular allowing the supply of the multi-stage thermocompressor and the continuous production of compressed gas; the multi-stage thermocompressor may include at least three, preferably at least four, reservoirs in each group, allowing the gas to be subjected to multiple pressure stages, thereby achieving a greater pressure rise for a given temperature difference; the high temperature source can be a waste high temperature source, such as a biomass dihydrogen production plant or an electrolyzer, whereby the heat generated can be recovered, thus reducing the energy costs consumed by the thermal compressor, whether it is a multi-stage thermal compressor or another type of thermal compressor; -All reservoirs in the same group can have the same volume, simplifying the multi-stage thermal compressor.

[0011] The present invention also relates to a process for converting a product placed in a liquid product reservoir, the product being in a gaseous state at a pressure of 1 bar and a temperature of 283 K, the process comprising the steps of: -In the main circuit, - extracting a liquid primary product from said liquid product reservoir; In the recovery circuit, - vaporizing the liquid product in the liquid product reservoir to obtain a gaseous recovery product; - transferring said recovered product to at least one thermal compressor; at least partially compressing the recovered product in the at least one thermal compressor by increasing the temperature of the recovered product or an intermediate agent such as a metal hydride using a low temperature source and a high temperature source, the low temperature source receiving low temperature energy from the main circuit.

[0012] Thanks to these measures, the recovered products resulting from the boil-off phenomenon can be compressed to pressure levels that make them recoverable with low energy consumption.

[0013] Further features include: the process may further comprise, in the main circuit, after the extraction step, a step of evaporation of the main product, which makes it possible to use the low-temperature energy released by the main product during evaporation; the temperature of the liquid product in the liquid product reservoir can be below 123 K, allowing air gas to be used in the process according to the invention; the pressure of the gaseous product downstream of said at least one thermal compressor can be equal to or greater than 300 bar, e.g. suitable for use in the mobility sector; Said compression of the recovered product can be carried out at least in part by a cyclic process of thermal compression of the gas that is the recovered product in the context of the present invention, in which several reservoirs of a group are in contact with one reservoir or a series of hotter reservoirs to carry out cycles of increasing pressure and then decreasing pressure to increase the pressure of other colder reservoirs. A multi-stage type thermal compressor can be used in a cyclic process for thermally compressing gas in several reservoirs of at least one group of said thermal compressor, each cycle comprising the following steps for each reservoir of each group: - cooling gas stored in a reservoir and transferring gas from a source to the reservoir; - transferring gas from a donor reservoir to said reservoir, said donor reservoir being the reservoir with the lowest gas pressure among the reservoirs of said group whose gas is at a higher pressure and temperature than said gas, until the pressures of said reservoir and said donor reservoir are equal, repeating this step, if necessary, as long as there is another reservoir in said group whose gas is at a higher pressure and temperature than said gas; - heating a gas stored in a reservoir and transferring the gas from the reservoir to a destination; - transferring the gas from said reservoir to a receiving reservoir, said receiving reservoir being the reservoir with the highest gas pressure among the reservoirs of said group whose gas is at a lower pressure and temperature than the gas in said reservoir, until the pressures of said reservoir and said receiving reservoir are equal, repeating this step, if necessary, as long as there is another reservoir in said group whose gas is at a lower pressure and temperature than the gas in said reservoir, the steps of cooling gas stored in the reservoir and transferring gas from an upstream source to the reservoir are performed sequentially for each reservoir in the group; Gases can be compressed to high pressures by thermal compression, avoiding problems with noise and wear on mechanical parts. This process is particularly energy efficient because the heat used to increase the pressure in one reservoir can be used to compress the contents of other reservoirs as the pressure drops, allowing for cascading compression. the thermal compression process in the multi-stage thermal compressor can be carried out in two groups of reservoirs, so that the steps of cooling the gas stored in one reservoir and transferring the gas from the upstream source can be carried out sequentially to one of the reservoirs in one group and then to one of the reservoirs in the other group, thus optimizing the process and, in particular, allowing the continuous production of gas to be fed and compressed to the multi-stage thermal compressor; During the step of transferring gas from a donor reservoir of the same group that has a higher gas pressure and temperature to said reservoir, the transferred gas can be cooled in order to reduce the temperature rise of the contents of said reservoir, thereby maintaining a temperature difference between the reservoir whose pressure is increasing and the reservoir whose pressure is decreasing, which makes it possible to optimize the compression of the gas in said reservoir; each group of reservoirs may contain at least three, preferably at least four reservoirs, and each of the two transfer steps may be repeated at least two, preferably at least three times, exposing the gas to several pressure stages, making it possible to achieve a higher pressure rise for a given temperature difference; The thermal compression process, whether or not a multi-stage type thermal compressor is used, can further comprise a gas compression step in a metal hydride compressor after the first thermal compression, which makes it possible to combine a first compression offering the advantages of a thermal compressor with a subsequent thermochemical compression in case the amount of cryogenic energy provided by the main circuit is not sufficient to achieve the desired compression level. during the step of cooling the gas stored in the first reservoir, it is possible to extract heat from said first reservoir and use it in the step of reheating the gas stored in the second reservoir, thus optimizing the energy consumption of the process; At least two steps can be performed simultaneously, the first step involving gas transfer between a first entity and a second entity, these two entities being an upstream source and a reservoir, two reservoirs, or a reservoir and a target, and the second step involving gas transfer between a third entity and a fourth entity, these two entities being an upstream source and a reservoir, two reservoirs, or a reservoir and a target, the first, second, third, and fourth entities being four separate entities, allowing the cycle to be optimized, with several different stages occurring simultaneously or in the same group in several different reservoirs of a multi-stage thermal compressor. The process of transferring gas from an upstream source to a first reservoir can be performed simultaneously with the process of transferring gas from a second reservoir to a receiving reservoir or target, thereby optimizing the cycle by running different processes simultaneously in different reservoirs, or even in the same group, of a multi-stage thermocompressor. [Brief explanation of the drawings]

[0014] The present invention will be better understood from the following detailed description when read in conjunction with the accompanying drawings.

[0015] [Figure 1]FIG. 1 is a schematic diagram of a conversion system according to the present invention, which comprises a thermocompressor, the low-temperature source of which comprises a low-temperature circuit through which a heat transfer liquid flows, the low-temperature energy of the heat transfer liquid comes from the main circuit, and the high-temperature source of the thermocompressor is thermally connected to the ambient air. [Figure 2] FIG. 2 is a schematic diagram of a processing system according to the present invention including a thermocompressor, the cold source of which includes a cold circuit through which the main product flows in gaseous form, and the hot source of which is thermally connected to ambient air. [Figure 3] FIG. 3 is a schematic diagram of a treatment system according to the invention, comprising a thermocompressor, the cold source of which comprises a low temperature circuit in which the main product circulates in an evaporator, and the hot source of which is thermally connected to ambient air. [Figure 4] FIG. 4 is a schematic diagram of a conversion system according to the invention, comprising a thermocompressor, a cold source comprising a cold circuit through which a heat transfer liquid flows, and a hot source having a temperature higher than the ambient air. [Figure 5] FIG. 5 is a schematic diagram of a conversion system according to the present invention, comprising a first thermal compressor and a second thermal compressor, wherein the low temperature source of the first thermal compressor comprises a low temperature circuit, a heat transfer liquid flows through the low temperature circuit, the low temperature energy of the heat transfer liquid comes from the main circuit, the high temperature source of the first thermal compressor is thermally connected to the ambient air, the high temperature source of the second thermal compressor is thermally connected to the ambient air, and the high temperature source of the second thermal compressor is hotter than the ambient air. [Figure 6] FIG. 6 is a schematic diagram of a conversion system according to the present invention, comprising a first thermal compressor whose low-temperature source includes a low-temperature circuit through which a heat transfer liquid flows, whose low-temperature energy comes from a main circuit, and whose high-temperature source is thermally connected to ambient air, and a second thermal compressor whose low-temperature source includes a low-temperature circuit through which a heat transfer liquid flows, and whose high-temperature source is hotter than the ambient air. [Figure 7] FIG. 7 is a schematic diagram of a multi-stage thermocompressor according to one embodiment of the present invention; [Figure 8] FIG. 8 is a schematic diagram of the steps involved in the hot gas compression process as illustrated in FIG. [Figure 9] FIG. 9 is a schematic diagram of the first stage of a process for thermally compressing a gas in a multi-stage thermal compressor according to a preferred embodiment of the present invention. [Figure 10] FIG. 10 is a schematic diagram of the steps that complete the process that begins in FIG.

[0016] The conversion systems described in this invention, some of which are shown in Figures 1 to 6, allow for the conversion of a liquid product into a compressed gaseous product, which is in the gaseous state at a pressure of 1 bar and a temperature of 283 K.

[0017] The product in connection with the present invention is preferably dihydrogen, but it can also be any other product, such as, for example, oxygen, nitrogen, methane, helium or natural gas.

[0018] Systems according to the present invention comprise at least one liquid product reservoir 8 and, in some embodiments, may comprise at least one compressed gas product reservoir 9 .

[0019] In the liquid product reservoir 8 the temperature is preferably below 123 K, for example between 15 and 100 K, and the pressure is preferably between 1 and 10 bar, for example 1 bar.

[0020] In the gas product reservoir the temperature is preferably between 260K and 310K and the pressure is greater than or equal to 2 bar, preferably greater than 300 bar.

[0021] The system according to the invention also includes a main circuit 10 arranged to pass a first portion of the product initially stored in the liquid product reservoir 8, called the main product.

[0022] The main circuit 10 may include at least one evaporator 11 .

[0023] In the present invention, the term "evaporator" refers to any physical entity in which the primary product can be evaporated, i.e., can change from a liquid state to a gaseous state. Thus, the evaporator 11 may be a device dedicated to evaporation, or it may simply be a pipe or any location where conditions exist such that the primary product, initially in a liquid state, transitions to a gaseous state.

[0024] When the system according to the invention comprises an evaporator 11, a single evaporator 11 can be used or several evaporators 11 can be arranged in parallel.

[0025] The main circuit 10 includes transfer means for extracting the main product in liquid form from the liquid product reservoir 8, and in some embodiments to the evaporator 11. In this case, the transfer may be direct, or the main product may pass through other devices between the liquid product reservoir 8 and the evaporator 11, such as a cryogenic pump. Thus, the main circuit 10 is configured to extract the main product in liquid form from the liquid product reservoir 8. The main circuit 10 may also include transfer means for transferring the main product to the gaseous product reservoir 9, for example, for transferring the gaseous main product from the evaporator 11 to the gaseous product reservoir 9. In this case, the transfer may be direct, or the main product may pass through other devices between the evaporator 11 and the gaseous product reservoir 9.

[0026] The system according to the invention also includes a recovery circuit 12 configured to pass a second portion of the product initially stored in the liquid product reservoir 8, called the recovered product. The recovered product is the result of the "boil-off" phenomenon, that is, a product that spontaneously evaporates as a result of the heating performed in the liquid product reservoir 8. All or only a portion of the product resulting from the "boil-off" evaporation can be sent to the recovery circuit 12 and constitute the recovered product.

[0027] The recovery circuit 12 includes at least one thermal compressor 13 .

[0028] In the context of the present invention, the term "thermocompressor" refers to any device that can compress a gas at least in part by increasing the temperature of the gas or by increasing the temperature of an intermediate agent such as a metal hydride. To generate this temperature increase, the thermocompressor 13 uses a cold source and a hot source.

[0029] According to a preferred embodiment of the present invention, at least one thermal compressor 13 is of the multi-stage type as described below. In embodiments having several thermal compressors 13, some or all of the thermal compressors 13 may be of the multi-stage type.

[0030] A single thermocompressor 13 can be used, or multiple thermocompressors 13 can be arranged in series to operate several compression stages and / or can be operated in parallel.

[0031] Recovery circuit 12 includes transfer means for transferring the gaseous recovery product from liquid product reservoir 8 to thermal compressor 13. This transfer may be direct, or other devices may be used to transfer the recovery product between liquid product reservoir 8 and thermal compressor 13. Recovery circuit 12 is therefore configured to extract the gaseous recovery product from liquid product reservoir 8. Recovery circuit 12 may also include transfer means for transferring the compressed recovery product from thermal compressor 13 to gaseous product reservoir 9. This transfer may be direct, or other devices may be used to convey the recovery product between thermal compressor 13 and gaseous product reservoir 9.

[0032] If the system according to the present invention includes a single gas product reservoir 9, the main circuit 10 and the recovery circuit 12 can transfer the main product and the recovery product to this single gas product reservoir 9. On the other hand, if the system according to the present invention includes multiple gas product reservoirs 9, the main circuit 10 and the recovery circuit 12 can transfer the main product and the recovery product to the same gas product reservoir 9 or to separate gas product reservoirs 9.

[0033] In other embodiments, the system according to the invention may comprise a single gas product reservoir 9 downstream of only one of the main circuit or the recovery circuit, or the system according to the invention may not comprise a gas product reservoir 9 at all. Indeed, once compressed in at least one thermal compressor 13, the recovery product may undergo further processing or may be used without prior storage. The main product may also undergo further processing or may be used without prior storage after losing some of its cryogenic energy from the liquid product reservoir 8.

[0034] In the present invention, at least one cold source of the thermocompressor 13 is arranged to receive cold energy from the main circuit 10, which initially carries the main product in liquid form at low temperatures, for example below 123 K. The cold energy stored in the liquid main product is advantageously reused.

[0035] In a first embodiment of the invention shown in Figures 1 and 4 to 6, low temperature energy is extracted from the main circuit 10 in an evaporator 11, taking advantage of the fact that low temperature energy comes out of the main product during evaporation. The low temperature source of at least one thermocompressor 13 can then comprise a low temperature circuit 14 configured to pass a heat transfer fluid different from the main product. The low temperature circuit 14 is then thermally connected to the at least one evaporator 11 and transfers the low temperature energy from this evaporator 11 to the heat transfer fluid. The heat transfer fluid is then sent to the thermocompressor 13 to form the low temperature source.

[0036] The heat transfer fluid may be of the glycol type. It is preferably a silicone-based fluid which has the advantage of remaining in a liquid state up to a temperature of about 163K.

[0037] In a second embodiment, the low-temperature source for at least one thermocompressor 13 comprises a low-temperature circuit 14 configured to pass the main product. As shown in FIG. 3, low-temperature energy can then be extracted from the main circuit 10 by an evaporator 11, which is located as close as possible to the thermocompressor 13 so that the low-temperature energy is transferred directly from the main product to the thermocompressor 13. In this case, the evaporator 11 performs the function of the low-temperature circuit 14, and the low-temperature energy released by the evaporation of the main product directly constitutes the low-temperature source for at least one thermocompressor 13 without using a heat transfer fluid separated from the main product. This may have the disadvantage that the main product is two-phase in the low-temperature source, making it more complicated to manage the heat exchange with the thermocompressor 13. In another embodiment shown in FIG. 2, low-temperature energy is extracted from the main circuit 10 downstream of the evaporator 11 when the main product is in a gaseous state. In another embodiment, low-temperature energy is extracted from the main circuit 10 upstream of the evaporator 11 or without the evaporator 11 when the main product is in a liquid state.

[0038] The main product is preferably such that it is in a liquid state at temperatures below 163 K. Heat transfer fluids commonly used by those skilled in the art cannot go below this temperature in their liquid state. Therefore, the use of the main product as a low temperature source for the thermocompressor 13 allows operation at lower temperatures without an intermediate heat transfer fluid, which improves the efficiency of the thermocompressor 13.

[0039] In certain embodiments, the pressure in the liquid product reservoir 8 can be increased, for example, to a value of 10 bar. The need to ensure high insulation quality in order to minimize the amount of gas formed in the liquid product reservoir 8 as a result of the boil-off phenomenon is not compatible with very high-pressure reservoirs. However, a value of 10 bar can be achieved. In this way, the recovered product can be recovered in the recovery circuit 12 at a higher pressure and therefore enters the first thermal compressor 13 at a higher pressure. This results in a higher outlet pressure from the thermal compressor 13.

[0040] The hot source of at least one thermocompressor 13 can be thermally connected to the ambient air, for example by using a convector to facilitate heat exchange. This hot source consumes little energy and has a sufficient temperature difference with the cold source coming from the main circuit 10 to provide the desired compression in the thermocompressor 13.

[0041] Using a 163 K heat transfer fluid and two multi-stage thermal compressors 13 arranged one downstream of the other as described below, with each thermal compressor 13 using the main circuit 10 as the cold source and ambient air as the thermally connected hot source, compression ratios of the order of 20 can be achieved. For example, if the recovered product pressure at the inlet to the first thermal compressor 13 is 10 bar, an outlet pressure of approximately 200 bar can be obtained from the second thermal compressor 13. Depending on the application, particularly the recovered product flow rate and desired outlet pressure level of at least one thermal compressor 13, a single thermal compressor 13 may be sufficient, or more than two thermal compressors 13 may be arranged in series.

[0042] Alternatively, if a hotter hot source is required to obtain a larger temperature difference with the cold source and therefore a larger pressure ratio between the inlet and outlet of the thermal compressor 13, the hot source of at least one thermal compressor 13 can be connected to a waste hot source, an electric heater, or any other hot source known to those skilled in the art and suitable for a thermal compressor, as shown in Figures 4 to 6, which optimizes the energy consumption of the system.

[0043] Finally, the high temperature source of at least one thermocompressor can be connected to a catalytic combustion device for a portion of the boil-off product that evaporates inside the liquid product reservoir 8. In this case, only a portion of the boil-off product is sent to the recovery circuit 12, and another portion of the boil-off product is sent to the catalytic combustion device.

[0044] These designs can achieve higher pressures of 350 or 700 bar depending on the application, such as those required in service stations. However, to achieve these pressures, it is necessary to use a multi-stage thermal compressor 13, increasing the number of reservoirs used in the compressor, and therefore the number of stages and the complexity of the associated process.

[0045] According to a particular mode of the invention shown in Figure 5, the system according to the invention comprises at least two thermocompressors 13 in series, the cold source of the first thermocompressor configured to receive cold energy from the main circuit 10, and the hot source of the second thermocompressor 13 configured to be warmer than the ambient air. The cold source of the second thermocompressor 13 can then be thermally connected to the ambient air. This cold source consumes little energy and can have a sufficient temperature difference with the hot source to achieve the desired compression in the second thermocompressor 13.

[0046] Taking the example above, if the first thermocompressor 13 has an inlet pressure of 10 bar and an outlet pressure of 200 bar, the second thermocompressor 13 can be configured with a pressure ratio of 1.75 or 3.5 to obtain outlet pressures of 350 bar and 700 bar respectively, while maintaining attractive energy efficiency.

[0047] Such values ​​are given as examples and do not limit the scope of the invention: a person skilled in the art will know how to configure the system to best meet the needs of each application.

[0048] In another particular embodiment of the invention shown in FIG. 6, the system according to the invention comprises at least two thermal compressors 13 in series, each of which allows the recovered product to pass through a compression stage. a first thermocompressor 13 having a cold source arranged to receive cold energy from the main circuit 10 and a hot source thermally connected to the ambient air; a second thermal compressor 13 located downstream of the first thermal compressor, which has a low temperature source configured to receive low temperature energy from the main circuit 10 and a high temperature source thermally connected to a waste high temperature source, an electric heater or a device for catalytic combustion of a portion of the boil-off product evaporating in the liquid product reservoir 8;

[0049] This arrangement of two thermal compressors 13 in series (FIGS. 5 and 6) is particularly advantageous when the amount of low-temperature energy coming from the main circuit 10 and the difference with the ambient air temperature is insufficient to compress the recovered product to the required pressure level. This results in a first stage of compression in the first thermal compressor 13, which is insufficient but consumes little energy. The second thermal compressor 13 consumes more energy due to its high-temperature source, but allows the pre-compression stage performed by the first thermal compressor to start from a higher inlet pressure, thereby raising the recovered product to the required pressure level.

[0050] If the two thermocompressors 13 are configured such that their cryogenic source receives cryogenic energy from the main circuit 10 (FIG. 6), the system can include a first cryogenic circuit 14 associated with the first thermocompressor 13, circulating a heat transfer fluid at a temperature between 163 K and 180 K, and a second cryogenic circuit 14 associated with the second thermocompressor 13, circulating a heat transfer fluid at a temperature between 163 K and 233 K. When the main product leaves the liquid product reservoir 8 at a temperature between 0 K and 163 K, the heat transfer fluid, which cannot drop below 163 K, can only capture a portion of the cryogenic energy stored in the main product. The use of the second cryogenic circuit allows a greater proportion of this cryogenic energy to be utilized. Thus, the presence of two cryogenic circuits 14 optimizes the use of the cryogenic energy released by the main product in the main circuit 10. Depending on the application, the system according to the present invention can include three or more thermocompressors 13 in series, each connected to a cryogenic circuit 14, to maximize this advantage.

[0051] The treatment system according to the invention can be used in a process for treating a product located in a liquid product reservoir 8. This process comprises the following steps: In the main circuit 10, - extracting the main product in liquid form from said liquid product reservoir 8; - optionally evaporating the main product 10; - transferring said main gas product to the main gas product reservoir 9, if necessary; in the recovery circuit 12, - evaporating the liquid product in said liquid product reservoir 8 to obtain a gaseous recovery product; - transferring the recovered product to a thermal compressor 13; - at least partially compressing the recovered product in the thermocompressor 13 by increasing the temperature of the recovered product or an intermediate agent such as a metal hydride by means of a low temperature source and a high temperature source receiving low temperature energy from the main circuit 10; - transferring the recovered product compressed by said thermal compressor 13 to said main gas product reservoir 9 or to said gas product recovery reservoir 9, as required.

[0052] As described above, in the present invention, it is advantageous to use a multi-stage type thermal compressor 13 as shown in FIGS.

[0053] In this application, the term "multi-stage thermal compressor" is used exclusively to describe a thermal compressor of the type described below and shown in Figures 7-10. The multi-stage thermal compressor 13 shown in Figure 7 includes an upstream source 1, a target 2, and one or more groups of reservoirs 3.

[0054] The multi-stage thermal compressor 13 converts gas at pressure P from an upstream source 1 at pressure P ターゲット In the present invention, the gas compressed by the multi-stage thermal compressor 13 is the recovered product.

[0055] The reservoirs 3 are capable of storing a fixed volume of the gas in question in a sealed manner. Within a group, the reservoirs 3 are preferably all of the same volume, for example 50 litres.

[0056] The multi-stage thermal compressor 13 includes a means 4 for heating and a means 5 for cooling the contents of each reservoir 3. The heating means 4 recovers heat energy or calories from a high-temperature source, and the cooling means 5 recovers low-temperature energy or calories from a low-temperature source. For example, the heating means 4 and the cooling means 5 bring a heat transfer fluid into contact with the contents of each reservoir 3. If the heat transfer fluid is hotter or colder than the contents of the reservoir 3, the heat transfer fluid can be used to heat or cool the contents, respectively.

[0057] Furthermore, the heating means 4 may be an electrical resistor immersed in the reservoir.

[0058] The high temperature source of the multi-stage thermocompressor 13, or any other type of thermocompressor 13 used in the present invention, can be connected to an electrolyzer or a biomass dihydrogen production unit. Thus, if the gas is dihydrogen, the heat generated to produce this dihydrogen can be recovered in the thermocompressor 13. Depending on the location where the multi-stage thermocompressor 13 is installed, other locally available waste high temperature sources can be used as the high temperature source to reduce the cost of the energy consumed. This can be, for example, a waste collection site or other industrial site where heat is generated.

[0059] The multi-stage thermal compressor 13 further comprises transfer means 6a for transferring gas directly from the upstream source 1 to each reservoir 3 of the group, and transfer means 6b for transferring gas directly from each reservoir 3 of the group to the target 2. In this specification, direct transfer refers to transfer without passing through another reservoir 3 of the same group or another group, or without passing through an upstream source 1 or target 2.

[0060] Finally, the multi-stage thermal compressor 13 includes bidirectional transfer means (7) for transferring gas directly from each reservoir in a group to other reservoirs in the same group. In this specification, direct transfer refers to transfer without passing through another reservoir 3 in the same group or another group, or without passing through an upstream source 1 or target 2. Thus, considering any pair of reservoirs 3 in the same group, gas can be transferred directly in both directions between these two reservoirs 3.

[0061] The multi-stage thermocompressor 13 involves a cyclic process for thermocompressing gas in a plurality of reservoirs 3 in at least one group. Each cycle comprises, for each reservoir 3a in each group, the following steps: - Cooling the gas stored in the reservoir 3a to a low temperature T1 and transferring gas to said reservoir 3a from an upstream source 1. At the end of this step, the reservoir 3a contains gas at pressure P0 and temperature T1. - Transfer gas from another donor reservoir 3 to the reservoir 3a. The donor reservoir 3 is the reservoir with the lowest gas pressure among the reservoirs 3 of the same group, whose gas has a higher pressure and temperature than the gas stored in the reservoir 3a. When the bidirectional transfer means 7 is opened between the reservoir 3a and the donor reservoir 3, the transfer is automatically carried out until the pressures of the reservoir 3a and the donor reservoir 3 become equal. During this step, the gas stored in the reservoir 3a is compressed. At the end of the first execution of this step, the reservoir 3a stores gas at a pressure P1 and a temperature T1. This step may be repeated several times, as long as there is another reservoir 3 of the group whose gas has a higher pressure and temperature than the gas stored in the reservoir 3a. For example, this step may be repeated twice if the group includes three reservoirs 3, or three times if the group includes four reservoirs 3. Each time this step is repeated, the pressure of the reservoir 3a increases by one step. At the end of this step, the reservoir 3a is at pressure P K and store gas at temperature T1 (K is equal to the number of times the transfer step is repeated). The gas stored in the reservoir 3a is heated to a high temperature T2, allowing the creation of a final pressure stage, from which the gas is transferred to the destination 2. At the end of this stage, the reservoir 3a is at a pressure P K+1 and gas at temperature T2. Pressure P K+1 is the pressure P target is close to or equal to - Transfer of gas from this reservoir 3a to another receiving reservoir 3, which is the reservoir with the highest gas pressure among the reservoirs 3 of the same group, where the gas has a lower pressure and temperature than the gas in this reservoir 3a. The transfer is carried out automatically when the two-way transfer means 7 is opened between the reservoir 3a and the receiving reservoir 3, until the pressures in this reservoir 3a and the receiving reservoir 3 are equal. At the end of the first execution of this step, the reservoir 3a is at P K 3a。 At the end of this step, and for each iteration until the end, reservoir 3a stores gas at a pressure and temperature T2 close to or equal to P1. This step may be repeated several times, as long as there is another reservoir 3 in the group whose gas is at a lower pressure and temperature than the gas in reservoir 3a. This step may be repeated, for example, twice if the group includes three reservoirs 3, or three times if the group includes four reservoirs 3. With each iteration of this step, reservoir 3a can increase the pressure of another reservoir 3 in the same group by one step. At the end of this step, and for each iteration until the end, reservoir 3a stores gas at a pressure and temperature T2 close to or equal to P1.

[0062] If all reservoirs 3 in a group have the same volume, the amount of gas in the reservoirs 3 can also be determined at each stage as follows: - at the end of the cooling and transfer steps of the upstream source 1, the reservoir 3a contains n 0 moles of gas, at the end of one transfer step from the donor reservoir 3 to said reservoir 3a, said reservoir 3a contains n1 moles of gas, At the end of all transfer steps from one or more donor reservoirs 3 to said reservoir 3a, said reservoir 3a has n K Store moles of gas, At the end of the heating step and transfer to destination 2, reservoir 3a contains n K-1 Store moles of gas, At the end of one transfer step from the reservoir 3a to the receiving reservoir 3, the reservoir 3a contains n K-2 Store moles of gas, At the end of all transfer steps from the reservoir 3a to one or more receiving reservoirs, the reservoir 3a has n -1 Store moles of gas.

[0063] The process of cooling the gas stored in the reservoir and transferring the gas from the upstream source 1 to said reservoir 3a is carried out simultaneously and consecutively for each reservoir 3 of the group, rather than for several reservoirs 3. In this way, the reservoirs 3 of the group undergo this process in turn, each following the same cycle at the same time, but with a time difference relative to the other reservoirs.

[0064] In this process, the gas is thermally compressed by opening the transfer means between the two reservoirs 3, where the gas is most compressed, allowing the pressure of the gas in the other reservoir 3 to increase. The reservoir 3 receiving the gas is in a cold state, while the reservoir 3 delivering the gas is in a hot state. This means that if the two reservoirs 3 contain an equal number of moles of gas, the hot reservoir 3 will have a higher pressure and can supply gas, increasing the pressure of the cold reservoir 3. Thus, during each cycle, each reservoir 3 experiences a pressure increase in the cold state, followed by a pressure decrease in the hot state. Therefore, during each cycle a reservoir 3 undergoes only one heating and cooling.

[0065] During the process of transferring gas from another reservoir 3 of the same group, which has a higher gas pressure and temperature, to the reservoir 3, it is preferable to cool the transferred gas. This maintains the temperature of the reservoir 3 receiving the hot gas at a low temperature, thereby maintaining the temperature difference with the other hot reservoirs 3. The transferred gas can be cooled before reaching the reservoir 3, for example, in the bidirectional transfer means 7 between the two reservoirs 3. Alternatively, the transferred gas can be cooled after arriving at the reservoir 3, for example, by cooling the entire contents of the reservoir 3 using the cooling means 5. In a preferred embodiment of the present invention, the contents of the reservoir 3 cooled to the low temperature T1 are kept at the low temperature T1 until the reheating process. Similarly, the contents of the reservoir 3 reheated to the high temperature T2 are preferably kept at the high temperature T2 until the cooling process. This ensures that the temperature difference between T1 and T2 can always be utilized when connecting the high temperature reservoir 3 to the low temperature reservoir 3 to increase the pressure of the latter.

[0066] To optimize the process cycle of the multi-stage thermal compressor 13, at least two process steps can be performed simultaneously. The first step involves gas transfer between a first entity and a second entity, where these two entities are an upstream source 1 and a reservoir 3, two reservoirs 3, or a reservoir 3 and a target 2, and the second step involves gas transfer between a third entity and a fourth entity, where these two entities are an upstream source 1 and a reservoir 3, two reservoirs 3, or a reservoir 3 and a target 2. The first, second, third, and fourth entities are four separate entities.

[0067] For example, in a preferred embodiment of the present invention, the process of transferring gas from the upstream source 1 to the first reservoir 3a-3h is performed simultaneously with the process of transferring gas from the second reservoir 3a-3h to the receiving reservoir 3 or target 2. Thus, while some reservoirs 3 of the multi-stage thermal compressor 13 are performing a particular process step, other reservoirs 3 are performing other process steps, saving time.

[0068] In a preferred embodiment of the present invention, in order to optimize the energy consumption of the process using the multi-stage thermal compressor 13, it is possible to use the heat extracted from the first reservoirs 3a-3h in the process of reheating the gas stored in the second reservoirs 3a-3h during the process of cooling the gas stored in said first reservoirs 3a-3h. For example, a heat transfer fluid can be circulated from the first reservoirs 3a-3h to the second reservoirs 3a-3h.

[0069] A group of reservoirs 3 includes at least two reservoirs 3, e.g., three, and preferably four reservoirs 3. The selection of the number of reservoirs 3 is made as a function of the number of stages required to compress the gas from the pressure P0 of the upstream source 1 to the desired pressure Ptarget2 of the target 2, along with other parameters of the multi-stage thermal compressor 13. Other parameters to be adjusted include the volume of the reservoirs 3 and the temperatures T1 and T2 to which the reservoirs 3 are heated and cooled. It is advantageous to have an even number of reservoirs 3 in a group. This ensures that, for each process step, each reservoir 3 performs one of the process steps.

[0070] The multi-stage thermocompressor 13 can include a single group of reservoirs 3, or preferably two groups of reservoirs 3. In fact, the total number of steps in the above-described cycle, including the repetition of the second and fourth steps, is equal to twice the number of reservoirs 3 in the group. Therefore, if the multi-stage thermocompressor 13 includes a single group, only half of the steps can be performed simultaneously by one of the reservoirs 3. In particular, the gas transfer step from the upstream source 1 to the target 2 is not performed by a single unit in each stage of the cycle. Therefore, it may be possible to have two groups operating in parallel, such that in each stage of the cycle, gas is transferred from the upstream source 1 to one of the reservoirs 3 of the multi-stage thermocompressor 13 and from one of the reservoirs 3 of the multi-stage thermocompressor 13 to the target 2. The number of reservoirs in each group may be different, but to obtain the above-described advantages for the two groups, both groups must have either an even or odd number of reservoirs.

[0071] In certain embodiments of the multi-stage thermocompressor 13, additional reservoirs 3 may be provided to allow for multiple heating and cooling stages. This is useful when the heating and cooling stages take longer than the transfer stage. Typically, when such stages take twice as long as the transfer stage, it may be useful to perform the heating and cooling in two stages.

[0072] According to another specific design of the multi-stage thermal compressor 13, a plant can be provided that initially operates between a first upstream source pressure P0 and a target pressure P1. Then, in a second stage, a portion of the gas can be extracted at pressure P1 and used as a source at pressure P1. The plant then increases the pressure to P2. This can continue as long as necessary until the target pressure is finally reached.

[0073] To optimize energy consumption, the temperature of the cold source, and therefore the temperature of the cooling T1, can be as low as possible, i.e., ambient temperature or the lowest cold source temperature available at the location of use.

[0074] A multi-stage thermocompressor 13 is particularly advantageous for small installations, for example with a gas output at the target 2 between 1 kg and 100 kg per hour.

[0075] Figure 8 shows an example of a multi-stage thermal compressor 13 equipped with two groups of reservoirs 3a and 3b. The volumes of the reservoirs 3a and 3b are equal. In Figure 8, arrows indicate gas flow. After gas transfer is completed, the state of each reservoir is recorded.

[0076] This cycle involves the following four stages: -Process A: - Heat the gas stored in reservoir 3a to temperature T2 and transfer part of this gas to destination 2. At the end of this step, reservoir 3a is at pressure P2 = P target , as well as n0 moles of gas at temperature T2. - Cool the gas in reservoir 3b to temperature T1 and transfer gas from upstream source 1 to reservoir 3b. At the end of this step, reservoir 3b contains n0 moles of gas at pressure P0 and temperature T1. -Step B: - The two-way transfer means 7 is opened between the reservoirs 3a and 3b to transfer gas from the reservoir 3a to the reservoir 3b. At the end of this step, the reservoir 3a is at a pressure P1 and a temperature T2. -1 moles of gas, and reservoir 3b stores n1 moles of gas at pressure P1 and temperature T1.

[0077] Steps C and D are identical to steps A and B, except that reservoirs 3a and 3b are swapped. At the end of step D, the cycle can start again at step A.

[0078] 9 and 10 show an example in which the multi-stage thermal compressor 13 includes two groups of four reservoirs: 3a to 3d and 3e to 3h. The volumes of reservoirs 3a to 3d are equal. The volumes of reservoirs 3e to 3h are equal. In FIGS. 9 and 10, arrows indicate gas flow. After gas transfer is completed, the state of each reservoir is recorded.

[0079] This cycle consists of eight steps A to H. The cycle that the reservoir 3a follows will now be described. Step A: Cool the gas in the reservoir 3a to a temperature T1 and transfer the gas from the upstream source 1 to the reservoir 3a. At the end of this step, the reservoir 3a contains n0 moles of gas at a pressure P0 and a temperature T1. Step B: The two-way transfer means 7 is opened between the reservoir 3a and the reservoir 3b, allowing the gas to be transferred from the reservoir 3b to the reservoir 3a. At the end of this step, the reservoir 3a contains n1 moles of gas at pressure P1 and temperature T1. Step C: The two-way transfer means 7 is opened between the reservoir 3a and the reservoir 3d, allowing the gas to be transferred from the reservoir 3d to the reservoir 3a. At the end of this step, the reservoir 3a contains n2 moles of gas at pressure P2 and temperature T1. Step D: The two-way transfer means 7 is opened between the reservoir 3a and the reservoir 3c, allowing the gas to be transferred from the reservoir 3c to the reservoir 3a. At the end of this step, the reservoir 3a contains n3 moles of gas at a pressure P3 and a temperature T1. Step E: The gas stored in the reservoir 3a is heated to a temperature T2 and a portion of this gas is transferred to the destination 2. At the end of this step, the reservoir 3a is at a pressure P4=P ターゲット , as well as n2 moles of gas at temperature T2. Step F: The two-way transfer means 7 is opened between the reservoir 3a and the reservoir 3b, allowing the gas to be transferred from the reservoir 3a to the reservoir 3b. At the end of this step, the reservoir 3a contains n1 moles of gas at a pressure P3 and a temperature T2. Step G: The two-way transfer means 7 is opened between the reservoir 3a and the reservoir 3d, allowing the gas to be transferred from the reservoir 3a to the reservoir 3d. At the end of this step, the reservoir 3a contains n0 moles of gas at a pressure P2 and a temperature T2. Step H: The two-way transfer means 7 is opened between the reservoir 3a and the reservoir 3c, allowing the gas to transfer from the reservoir 3a to the reservoir 3c. At the end of this step, the reservoir 3a is at a pressure P1 and a temperature T2. -1 Store moles of gas. At the end of step H, the cycle can start again at step A.

[0080] Naturally, reservoirs 3a to 3h all follow the cycle described above, interacting with the associated reservoir 3 at each transfer step. - Reservoir 3b begins the cycle at step C. - Reservoir 3c starts the cycle at step G. Reservoir 3d begins the cycle at step E. Reservoir 3e begins the cycle at step B. - Reservoir 3f starts the cycle at step D. - Reservoir 3g begins the cycle at step H. Reservoir 3h begins the cycle at step F.

[0081] The presence of two groups in the multi-stage thermal compressor 13 means that during each stage of the cycle, a reservoir 3 receives gas from the upstream source 1 and a reservoir 3 delivers gas to the target 2. For example, if in step A, reservoir 3d of the first group of reservoirs 3 delivers gas to the target 2, then in step B, reservoir 3h of the second group of reservoirs 3, and in step C, reservoir 3c of the first group of reservoirs 3, etc. Meanwhile, in step A, reservoir 3a of the first group of reservoirs 3 receives gas from the upstream source 1, then in step B, reservoir 3e of the second group of reservoirs 3, and in step C, reservoir 3b of the first group of reservoirs 3, etc.

[0082] Considering this example, by carrying out the heating and cooling steps over two transfer periods, ten reservoirs 3 are provided instead of eight. The ten reservoirs then form a single group, and each reservoir 3 can be connected to three other reservoirs 3 of the ten by bidirectional transfer means. Of course, each reservoir 3 must be connected to a source and a destination by transfer means.

[0083] Although the above description is based on specific embodiments, this does not in any way limit the scope of the invention, which may be modified, inter alia, by the substitution of technical equivalents or by different combinations of all or part of the features developed above.

Claims

1. 1. A system for processing a product, the product being in a gaseous state at a pressure of 1 bar and a temperature of 283 K, the system comprising: at least one liquid product reservoir (8), a main circuit (10) adapted to extract a main product in liquid form from said liquid product reservoir (8); a recovery circuit (12) comprising at least one thermal compressor (13) configured to at least partially compress the gas by increasing the temperature of said gas or an intermediate agent such as a metal hydride by means of a low temperature source and a high temperature source, and a transfer means for transferring a recovery product resulting from evaporation in said liquid product reservoir (8) to one of said at least one thermal compressor (13), wherein the low temperature source of at least one of said thermal compressors (13) is configured to receive low temperature energy from said main circuit (10).

2. 2. The system for processing a product according to claim 1, wherein the main circuit (10) comprises at least one evaporator (11) and a transfer means for transferring a main product in liquid state from the liquid product reservoir (8) to one of the at least one evaporator (11).

3. 3. The system of claim 2, wherein the low temperature source of at least one of the at least one thermal compressors comprises a low temperature circuit configured to have a heat transfer fluid passing therethrough that is thermally connected to the evaporator.

4. The system according to any one of claims 1 to 3, wherein the cold source of at least one of the at least one thermal compressor (13) comprises a cold circuit (14) configured through which the main product passes.

5. The system according to any one of claims 1 to 4, wherein the high temperature source of at least one of the at least one thermal compressor (13) is thermally connected to ambient air.

6. The recovery circuit includes: at least one first thermal compressor (13), the cold source of which is arranged to receive cold energy from said main circuit (10) and the hot source of which is thermally connected to the ambient air; A system according to any one of claims 1 to 5, comprising, downstream of the at least one first thermal compressor (13) with respect to the movement of the second gas product, at least one second thermal compressor (13), the low temperature source of which is configured to receive low temperature energy from the main circuit (10) or from the ambient air and the high temperature source of which is thermally connected to a waste high temperature source or to an electric heating source.

7. At least one of said at least one thermocompressor (13) is a multi-stage type thermocompressor (13) comprising an upstream source (1), a target (2) and at least one group of reservoirs (3) each comprising at least two reservoirs (3), said thermocompressor (13) further comprising means (4) for heating and means (5) for cooling the contents of each reservoir (3), said means (4) for heating being connected to said hot source and said cold means (5) for cooling being connected to said cold source, each group comprising: - transfer means (6a, 6b) for transferring gas directly from said upstream source (1) to each reservoir (3) and from each reservoir (3) directly to said target (2); A system according to any one of claims 1 to 6, further comprising, for each reservoir (3) of the group, bidirectional transfer means (7) enabling direct transfer of gas between said reservoir (3) and at least one other reservoir (3) of the group.

8. A process for converting a product located in a liquid product reservoir (8), said product being in gaseous state at a pressure of 1 bar and a temperature of 283 K, said process comprising the following steps: In the main circuit (10), - Extracting the main product in liquid form from said liquid product reservoir (8); in the recovery circuit (12), - vaporizing the liquid product in said liquid product reservoir (8) to obtain a gaseous recovery product; - transferring said recovered product to at least one hot compressor (13); - at least partially compressing the recovered product by increasing the temperature of the recovered product or an intermediate agent such as a metal hydride in the at least one hot compressor (13) by means of a low temperature source and a high temperature source, the low temperature source receiving low temperature energy from the main circuit (10).

9. 9. The process according to claim 8, further comprising, in the main circuit (10), after the extraction step, a step of evaporation of the main product.

10. The process according to any one of claims 8 to 9, wherein the temperature of the liquid product in the liquid product reservoir (8) is below 123K.

11. The process according to any one of claims 8 to 10, wherein the pressure of the gaseous product downstream of the at least one thermal compressor (13) is equal to or greater than 300 bar.

12. The compression of the recovered product is at least partially performed by a cyclic process of thermal compression of gas in a plurality of reservoirs (3), each cycle comprising, for each reservoir (3a-3h) of the plurality of reservoirs (3), the following steps: - cooling the gas stored in said reservoirs (3a-3h) and transferring gas from an upstream source (1) to said reservoirs (3a-3h); - transferring gas from a donor reservoir (3) to said reservoirs (3a-3h), said donor reservoir (3) being at a higher pressure and temperature than said reservoir (3a-3h) and said gas of the same group, preferably said donor reservoir (3) being the reservoir with the lowest gas pressure among said reservoirs (3) of said group whose gas is at a higher pressure and temperature than the gas in said reservoirs (3a-3h), until the pressures of said reservoirs (3a-3h) and said donor reservoir (3) are equal, and repeating this step, if necessary, as long as there is a donor reservoir (3) of said group whose gas is at a higher pressure and temperature than the gas in said reservoirs (3a-3h); - heating the gas stored in the reservoirs (3a-3h) and transferring the gas from the reservoirs (3a-3h) to the target (2); - transferring the gas from said reservoir (3a-3h) to a receiving reservoir (3) which has a lower pressure and temperature than the gas from said reservoir (3a-3h), preferably said receiving reservoir (3) being the reservoir with the highest gas pressure among said reservoirs (3) of said group whose gas has a lower pressure and temperature than the gas in said reservoir (3a-3h) until the pressures in said reservoir (3a-3h) and in said receiving reservoir (3) are equal, and repeating this step, if necessary, as long as there is another reservoir (3) in said group whose gas has a lower pressure and temperature than the gas in said reservoir (3a-3h), 12. The process according to any one of claims 8 to 11, wherein the steps of cooling the gas stored in the reservoirs (3a-3h) and transferring gas from the upstream source (1) to the reservoirs (3a-3h) are carried out successively for each reservoir (3) of the group.

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