Apparatus and method for compressing boil-off gas

Abstract

Device (100) for compressing exhaust evaporation gas (1) of a cryogenically stored gas (LG), the device (100) comprising a container (10) for cryogenically stored gas (LG) with an outlet (11) for discharging an exhaust evaporation gas (1) of the cryogenically stored gas (LG) that can be provided in the container (10), a compressor (20) with at least one compressor stage (21), and a heat exchanger (30) for carrying out a heat exchange between the exhaust evaporation gas (1) and an exhaust evaporation gas (3) compressed in the first compressor stage (21), wherein the heat exchanger (30) has a first inlet (31) for receiving the exhaust evaporation gas (1), a first outlet (32) for discharging a heated exhaust evaporation gas (2) to the first compressor stage (21), a second inlet (33) for receiving the exhaust evaporation gas compressed in the first compressor stage (21) (3), and a second outlet (34) for discharging a cooled and compressed exhaust gas (4) to a downstream process,in particular to a second compressor stage (22) of the compressor (20), which is designed to further compress the exhaust evaporation gas (4) compressed in the first compressor stage (21) and cooled in the heat exchanger (30) in order to provide a further compressed exhaust evaporation gas (5).

Description

[0001] The present invention relates to a device and a method for compressing evaporation gas of a cryogenically stored gas.

[0002] Facilities that process or consume large quantities of gas are typically supplied with liquefied gas stored at cryogenic temperatures, as this is easier to transport and deliver than large quantities of compressed gas. However, the use of liquid gas maintained at low temperatures presents the problem that, even when properly stored in a suitable storage vessel, the gas will warm up and vaporize due to heat from the environment, leading to a continuous increase in the pressure in the storage vessel. To ensure that the gas pressure in the storage vessels does not exceed the respective pressure specifications, the vaporized gas, also known as boil-off gas (BOG), must either be vented from the storage vessels or utilized.Typically, the pressure of the evaporation gas accumulating in the storage tanks is increased in suitable devices before the evaporation gas is fed to a consumer.

[0003] Since the temperature of the exhaust steam gas is usually still very low, the materials that come into contact with the exhaust steam gas must be high-strength, ductile, and fatigue-resistant, even at temperatures as low as -196 °C or lower. This limits the choice of suitable materials and is associated with higher material costs. For this reason, the state-of-the-art devices for compressing exhaust steam gas, which are used, for example, in natural gas and hydrogen compressor stations, typically operate with gas inlet temperatures that are in the range of ambient temperature or down to around -40 °C or even -160 °C, and are therefore significantly warmer than -196 °C. The gas inlet temperature into the compressor is adjusted using preheating systems. The energy required to increase the temperature of the exhaust steam gas in the preheating systems is obtained, for example, by extracting heat from the environment or using an electrical preheating device.However, such devices have the disadvantage that they are energy-intensive and waste the cold contained in the exhaust gas.

[0004] Based on the cited prior art, the present invention is based on the object of mitigating or even eliminating these and other disadvantages of the prior art and providing a device of the type mentioned above, which is characterized by higher compression and energy efficiency, enables lower complexity and thus greater operational readiness, and in which the use of cost-intensive materials, which are particularly stable at low temperatures, in particular at temperatures below approximately -196 °C, can be dispensed with. It is a further object of the present invention to provide a method for compressing evaporation gas from a cryogenically stored gas, which has higher compression and energy efficiency than the methods known from the prior art and does not require the use of expensive low-temperature-resistant materials.

[0005] This object is achieved by a device and a method according to the independent patent claims. Advantageous embodiments and further developments are the subject of the dependent claims.

[0006] A device according to the invention for compressing exhaust vapor gas of a cryogenically stored gas comprises a container for cryogenically stored gas, which has an outlet for discharging an exhaust vapor gas of the cryogenically stored gas that can be provided in the container. The device further comprises a compressor with at least one compressor stage, preferably at least two compressor stages, and a heat exchanger for performing a heat exchange between the exhaust vapor gas and an exhaust vapor gas compressed in the first compressor stage. The heat exchanger has a first inlet for receiving the exhaust vapor gas, a first outlet for discharging a heated exhaust vapor gas to the first compressor stage, a second inlet for receiving the exhaust vapor gas compressed in the first compressor stage, and a second outlet for discharging a cooled and compressed exhaust vapor gas to a downstream process, in particular to a consumer.In the case of a multi-stage compressor, the downstream process may, in particular, be the second compressor stage of the compressor. The second compressor stage is designed to further compress the exhaust gas compressed in the first compressor stage and cooled in the heat exchanger, thus providing a further compressed exhaust gas.

[0007] In contrast to prior art devices for compressing exhaust steam gas, such a device is characterized by the fact that it operates purely internally within the compressor. In other words, the cold of the exhaust steam gas and the heat generated during compression in the first compressor stage are not transferred to other processes but are used exclusively for gas cooling in the compressor system. Because the cold of the exhaust steam gas is transferred to the gas pre-compressed in the first compressor stage rather than to preheaters, the available process cooling is not wasted, and the energy efficiency of the compressor system is optimized.On the other hand, the efficiency of the device is also increased because the procurement and operation of a preheater with an external heat source is eliminated, and the energy for preheating the exhaust gas does not have to be expended separately, as it is provided by the first compressor stage. The aforementioned measures enable an increase in energy efficiency of up to 20% compared to prior art devices in which the exhaust gas is preheated before compression. A further advantage of such a device is that the compressor, and in particular the first compressor stage, is not exposed to the low temperatures of the exhaust gas.This is particularly relevant for gases whose boiling point is lower than that of nitrogen, since the materials commonly used in compressors cannot withstand temperatures below approximately -196 °C or are very expensive. These very expensive materials, which also function at very cold exhaust gas temperatures, can thus be omitted from the design of compressors.

[0008] The container for cryogenically stored gas, the heat exchanger, and the at least one compressor stage, preferably the at least two compressor stages, of the compressor are fluidically connected to one another, so that exhaust vapor gas from the container can be fed to the first compressor stage via the heat exchanger. In particular, the first compressor stage and the heat exchanger are fluidically connected to one another such that the exhaust vapor gas compressed in the first compressor stage can be fed directly to the second inlet of the heat exchanger. The exhaust vapor gas compressed in the first compressor stage can then be fed to the downstream process, in particular the second compressor stage, via the heat exchanger. One or more further compressor stages of the same compressor or of a further compressor can be connected to the second compressor stage.In the context of the present invention, a "further compressor stage" is understood to mean a compressor stage which is designed to increase the pressure of the gas supplied to it.

[0009] In one embodiment of the device, the container is suitable for the cryogenic storage of gas selected from the group consisting of hydrogen, nitrogen, helium, neon, krypton, argon, liquefied natural gas, oxygen, and mixtures thereof. In a preferred embodiment, the cryogenically stored gas is selected from the group consisting of hydrogen, helium, neon, and mixtures thereof. Due to the very low boiling points of hydrogen (-252 °C), helium (-269 °C), and neon (-246 °C) at atmospheric pressure, the advantages of the device according to the invention are particularly evident when used with these gases, since the use of the usually required, low-temperature-resistant and expensive materials, particularly for the compressor, can be dispensed with.

[0010] The cryogenically stored gas is particularly preferably hydrogen.

[0011] In one embodiment of the device, the heat exchanger is a countercurrent heat exchanger. Due to the flow in opposite directions, there is always a temperature gradient between the material flows, i.e., between the exhaust steam gas and the exhaust steam gas compressed in the first compressor stage, so that almost the entire amount of heat can be transferred from one material flow, i.e., the exhaust steam gas compressed in the first compressor stage, to the other, i.e., the exhaust steam gas. Countercurrent heat exchange is therefore significantly more effective, more cost-effective, and, due to the associated energy savings, also more environmentally friendly than cocurrent heat exchange.

[0012] The heat exchanger is preferably a diffusion-welded counterflow heat exchanger. Diffusion-welded heat exchangers (printed circuit heat exchangers; PCHEs) are characterized by a robust heat transfer core without connections, seals, or solder joints, which enables very close proximity of the material flows and thus an exceptionally high heat transfer rate with correspondingly high efficiencies. Due to these properties, diffusion-welded heat exchangers can be cooled down within a relatively short time, which is particularly advantageous during start-up of the process described in more detail below. Furthermore, diffusion-welded heat exchangers are characterized by a very broad performance window compared to conventional shell-and-tube heat exchangers and significantly greater resistance to temperature fluctuations and the effects of thermal fatigue.The latter leads to a reduction in the overall costs associated with repair and maintenance.

[0013] For occupational safety reasons, the temperature of the gas exiting the heat exchanger should not be lower than the temperature at which nitrogen and / or oxygen condense. Rapid cooling of the heat exchanger is therefore advantageous, as it shortens the time until the process can begin.

[0014] In one embodiment of the device, a first valve is arranged downstream of the first outlet of the heat exchanger and upstream of the first compressor stage. This first valve is configured to supply the heated exhaust evaporation gas to the second compressor stage. The parallel connection of the first and second compressor stages makes it possible, for example, to service the first compressor stage without having to temporarily store or dispose of the exhaust evaporation gas still accumulating in the vessel.

[0015] In particular, the first valve can be arranged in the line fluidically connecting the second outlet of the heat exchanger and the second compressor stage. The first valve is fluidically connected to the first outlet of the heat exchanger via a first line branching off from the line connecting the first outlet of the heat exchanger to the first compressor stage.

[0016] In one embodiment of the device, the first outlet of the heat exchanger is or can be fluidly connected to the vessel via a bypass line arranged downstream of the first compressor stage and / or downstream of the second compressor stage. Such a bypass line makes it possible to return compressed exhaust evaporation gas to the vessel without using compressed exhaust evaporation gas in the first and / or second compressor stage to heat fresh exhaust evaporation gas from the vessel in the heat exchanger. This is particularly advantageous when starting up the process described in more detail below.

[0017] In one embodiment of the device, the first outlet of the heat exchanger is or can be fluidly connected to the container via a bypass line arranged downstream of the first compressor stage and / or downstream of the second compressor stage, wherein a second valve is arranged downstream of the first compressor stage and upstream of the second inlet of the heat exchanger. This second valve is configured to feed the exhaust evaporation gas compressed in the first compressor stage to the bypass line instead of to the second inlet of the heat exchanger. Such a bypass line makes it possible to return compressed exhaust evaporation gas to the container without exhaust evaporation gas compressed in the first and / or second compressor stage being used to heat fresh exhaust evaporation gas from the container in the heat exchanger. This is particularly advantageous when starting up the method described in more detail below.Preferably, the exhaust gas compressed in the first compressor stage is fed into the bypass line downstream of the second compressor stage via a line which opens downstream of the second compressor stage.

[0018] In embodiments of the device, the bypass line can have a reliquefaction device for previously compressed evaporation gas. The reliquefaction device allows evaporation gas to be returned to the container in cryogenic form if it is not taken up by a consumer after compression. The reliquefaction device can, in particular, be a throttle valve.

[0019] In one embodiment of the device, the container for cryogenically stored gas is a mobile cryogenic tank, a storage tank of a liquefaction plant, or a storage tank of a transshipment terminal.

[0020] In one embodiment of the device, the compressor further comprises at least one further compressor stage, which is or can be fluidly connected to the first compressor stage and / or the second compressor stage. The further compressor stage is configured to compress the exhaust evaporation gas compressed in the first compressor stage and cooled in the heat exchanger. This makes it possible to take the second compressor stage out of operation, for example for maintenance purposes. Additionally or alternatively, the further compressor stage is configured to further compress the exhaust evaporation gas further compressed in the second compressor stage in order to provide an even more compressed exhaust evaporation gas.The presence of an additional compressor stage increases the operational flexibility of the device, as it can provide an even more compressed exhaust gas, for example depending on the pressure requirements of different consumers.

[0021] The problem is further solved by a method for compressing the evaporation gas of a cryogenically stored gas. The method comprises the following steps: a) compressing exhaust evaporation gas, which accrues in a container with cryogenically stored gas, in a first compressor stage of a compressor, preferably in a first compressor stage of a multi-stage compressor with at least two compressor stages; b) cooling the exhaust evaporation gas compressed in the first compressor stage in a heat exchanger; and c) discharging the exhaust evaporation gas compressed in the first compressor stage and cooled in step b) to a downstream process. In particular, in the downstream process, the exhaust evaporation gas compressed in the first compressor stage and cooled in step b) can be compressed in a second compressor stage of the multi-stage compressor in order to obtain a further compressed exhaust evaporation gas.

[0022] According to the process according to the invention, the exhaust evaporation gas is heated in the heat exchanger prior to its compression in step a) by heat exchange with the exhaust evaporation gas compressed in the first compressor stage to obtain a heated exhaust evaporation gas. In step b), the exhaust evaporation gas compressed in the first compressor stage is cooled in the heat exchanger by heat exchange with the exhaust evaporation gas that accrues in the vessel and is to be compressed in the first compressor stage.

[0023] With this method, the advantages already disclosed for the device disclosed herein can be achieved.

[0024] The method according to the invention can be carried out in particular with a device as described herein, whereby the advantages described for the corresponding device are additionally achieved.

[0025] In one embodiment of the process, the cryogenically stored gas is selected from the group consisting of hydrogen, nitrogen, helium, neon, krypton, argon, liquefied natural gas, oxygen, and mixtures thereof. Preferably, the cryogenically stored gas is selected from the group consisting of hydrogen, helium, neon, and mixtures thereof. Particularly preferably, the cryogenically stored gas is hydrogen. Here, too, the advantages of the process according to the invention are particularly evident with low-boiling gases, which would normally require the use of particularly low-temperature-stable and expensive materials, especially for the compressor.

[0026] In one embodiment of the method, the heat exchange between the exhaust steam gas and the exhaust steam gas compressed in the first compressor stage takes place according to the countercurrent principle. Preferably, the heat exchange between the exhaust steam gas and the exhaust steam gas compressed in the first compressor stage takes place using a diffusion-welded heat exchanger. This allows the advantages described in connection with the corresponding embodiments of the device disclosed herein to be achieved.

[0027] For occupational safety reasons, the exhaust gas should be heated to temperatures higher than the temperatures at which nitrogen and / or oxygen condense. Since heat is generated during gas compression, and higher temperatures can also have a detrimental effect on compressor efficiency and the materials used in the compressor, compression of the coolest gas possible should be attempted.

[0028] In one embodiment of the process, the exhaust gas accumulating in the vessel has a temperature between -272 °C and -160 °C. The exhaust gas heated by heat exchange has a temperature between -196 °C and -120 °C before its compression in step a), i.e. before its compression in the first compression stage of the multi-stage compressor. In this temperature range, the use of particularly low-temperature-stable and therefore expensive materials in the compressor can be dispensed with. The nevertheless low temperature range is also advantageous for the compression of an exhaust gas, as it improves the efficiency of the compression process and helps to manage the heat generated during compression. This is crucial for achieving higher compression ratios and reducing thermal stress on the compressor components, which can extend their service life.

[0029] In particular, an embodiment of the method is disclosed in which the exhaust gas heated by heat exchange has a temperature between -180 °C and -140 °C before its compression in the first compressor stage of the single- or multi-stage compressor. This temperature range is particularly preferred, especially in the case where the cryogenically stored gas is hydrogen, since it eliminates the use of expensive materials and, on the other hand, maintains the high efficiency of the first compressor stage.

[0030] In one embodiment of the process, the exhaust gas compressed in the first compressor stage and cooled in the heat exchanger in step b) is provided to the second compressor stage at a temperature between -170 °C and -60 °C. Efficient compression can be achieved by the second compressor stage in this temperature range.

[0031] In one embodiment of the process, the further compressed exhaust gas, i.e., the exhaust gas obtained from the second compressor stage, is further compressed in at least one additional compressor stage. As already described above for the corresponding embodiment of the device described herein, this increases the flexibility of the process and provides exhaust gas with the final pressure required by the respective customer.

[0032] Typical final pressures required by typical customers for compressed steam gas are: between 30 bar and 100 bar, in particular around 60 bar, for pipeline injection; between 350 bar and 800 bar for trailer filling; between 16 bar and 25 bar for refineries; between 20 bar and 200 bar for ammonia synthesis; between 6 bar and 65 bar for fuel gas supply, in particular for liquid hydrogen gensets or fuel cell gas turbines.

[0033] In one embodiment of the method, the exhaust steam gas is used for a predetermined time to cool the heat exchanger before the exhaust steam gas is used in step b) to cool the exhaust steam gas compressed in the first compressor stage. In other words, in this embodiment, the exhaust steam gas flows through the heat exchanger and is subsequently compressed in the first compressor unit without the exhaust steam gas compressed in the first compressor unit being fed to the heat exchanger for the purpose of heat exchange with the exhaust steam gas, specifically for a predetermined time. This allows the heat exchanger to be cooled particularly quickly to the desired low temperature.

[0034] The predetermined time may be the time until a predetermined temperature is reached at a first inlet of the heat exchanger for receiving the exhaust evaporation gas. Alternatively or additionally, the predetermined time may be the time until a predetermined temperature, in particular a temperature between -196°C and -120°C, is reached at a first outlet of the heat exchanger for discharging the heated exhaust evaporation gas to the first compressor stage. This ensures that the temperature of the exhaust evaporation gas supplied to the first compressor stage is compatible with the materials used in the first compressor stage of the compressor.

[0035] In one embodiment of the process, the exhaust gas is liquefied in a reliquefaction device and returned to the vessel after being compressed in at least one of the two compression stages of the compressor. Recycling the exhaust gas is particularly advantageous when no consumer is available for the compressed exhaust gas.

[0036] The present invention is described below by way of example with reference to the accompanying figures. Unless otherwise stated, the same reference numerals refer to components of the same design. Herein: Figure 1a Schematic representation of a device for compressing exhaust evaporation gas according to an embodiment of the present invention; Figure 1b Schematic representation of a device for compressing exhaust evaporation gas according to a further embodiment of the present invention; Figure 2 Schematic representation of a device for compressing exhaust evaporation gas according to a further embodiment of the present invention; Figure 3a Schematic representation of the material flows during the start-up phase of a method for compressing exhaust evaporation gas according to an embodiment of the present invention; Figure 3b Schematic representation of the material flows of the method from Figure 3a after the start-up phase; Figure 4aSchematic representation of the material flows during the start-up phase of a process for compressing exhaust gas according to a further embodiment of the present invention; Figure 4bSchematic representation of the material flows of the process from Figure 4aafter the start-up phase; Figure 5: Flow diagram of possible material flows in processes according to embodiments of the present invention.

[0037] Figure 1a is a schematic representation of an embodiment of an apparatus for compressing evaporation gas of a cryogenically stored gas. As in Figure 1aAs shown, the device 100 comprises a container 10 for cryogenically stored gas LG. In the container 10, exhaust vapor gas 1 of the cryogen provided in the container is produced, which can leave the container 10 via outlet 11 of the container 10. The device 100 further comprises a compressor 20 with a compressor stage 21 and a heat exchanger 30, wherein the heat exchanger 30 is designed to carry out a heat exchange between the exhaust vapor gas 1 and the exhaust vapor gas 3 compressed in the first compressor stage 21. For this purpose, the container 10 is fluidly connected via the outlet 11 to a first inlet 31 of the heat exchanger 30. The first inlet 31 of the heat exchanger 30 is correspondingly designed to receive the exhaust vapor gas 1 and is in turn fluidly connected to a first outlet 32 ​​of the heat exchanger 30.The first outlet 32 ​​of the heat exchanger 30 is fluidically connected to the first compressor stage 21 and is designed to discharge the exhaust evaporation gas 2, which has flowed through the heat exchanger 30, to the first compressor stage 21. The first compressor stage 21 is in turn fluidically connected to a second inlet 33 of the heat exchanger 30, which is designed to receive the exhaust evaporation gas 3 compressed in the first compressor stage 21. The second inlet 33 of the heat exchanger 30 is correspondingly designed to receive the exhaust evaporation gas 3 compressed in the first compressor unit 21 and is in turn fluidically connected to a second outlet 34 of the heat exchanger 30. The second outlet 34 of the heat exchanger 30 is in turn fluidically connected to a consumer 80 arranged downstream of the heat exchanger 30, i.e.a downstream process, wherein a further heat exchanger 60 can optionally be arranged between the second outlet 34 of the heat exchanger 30 and the consumer 80 in order to further temper, i.e. to cool or heat, the exhaust evaporation gas 4 compressed in the first compressor stage 21 and cooled in the heat exchanger 30 before it is discharged to a consumer 80. The gas cryogenically stored in the container 10 can in particular be hydrogen. The pressure of the exhaust evaporation gas 1 in the head space of the container 10 can be between 1.01 and 20 bara, in particular approximately 8 bara.

[0038] Figure 1b is a schematic representation of another example of an apparatus for compressing evaporation gas from a cryogenically stored gas. As in Figure 1bAs shown, the device 100 comprises a container 10 for cryogenically stored gas LG. In the container 10, exhaust evaporation gas 1 of the cryogen provided in the container is produced, which can leave the container 10 via outlet 11 of the container 10. The device 100 further comprises a compressor 20 with at least two compressor stages 21, 22 and a heat exchanger 30. The container 10 is fluidly connected to a first inlet 31 of the heat exchanger via the outlet 11. The first inlet 31 of the heat exchanger 30 is designed to receive the exhaust evaporation gas 1 and is in turn fluidly connected to a first outlet 32 ​​of the heat exchanger 30. The first outlet 32 ​​of the heat exchanger 30 is fluidly connected to the first compressor stage 21 and is designed to discharge the exhaust evaporation gas 2, which has flowed through the heat exchanger 30, to the first compressor stage 21.The first compressor stage 21 is in turn fluidically connected to a second inlet 33 of the heat exchanger 30, which is designed to receive the exhaust steam gas 3 compressed in the first compressor stage 21. The second inlet 33 of the heat exchanger 30 is correspondingly designed to receive the exhaust steam gas 3 compressed in the first compressor unit 21 and is in turn fluidically connected to a second outlet 34 of the heat exchanger 30. The second outlet 34 of the heat exchanger 30 is in turn fluidically connected to the second compressor stage 22 and is designed to deliver the exhaust steam gas 4, which has flowed through the heat exchanger 30, to the second compressor stage 22. The heat exchanger 30 is thus designed to carry out a heat exchange between the exhaust steam gas 1 and the exhaust steam gas 3 compressed in the first compressor stage 21.The second compressor stage 22 is configured to further compress the exhaust evaporation gas 4 compressed in the first compressor stage 21 and cooled in the heat exchanger 30, in order to provide a further compressed exhaust evaporation gas 5. A further heat exchanger 60 can optionally be arranged downstream of the second compressor stage 22 in order to temperature-control the exhaust evaporation gas 5 further compressed in the second compressor stage 22 before it is discharged to a consumer 80. The gas cryogenically stored in the container 10 can be, in particular, hydrogen. The pressure of the exhaust evaporation gas 1 in the headspace of the container 10 can be between 1.01 and 20 bara, in particular approximately 8 bara.

[0039] Figure 2 is a schematic representation of an example of another apparatus for compressing evaporation gas of a cryogenically stored gas. As in Figure 2 As shown, the device 100 comprises, in addition to the elements already described in connection with the Figure 1illustrated embodiment and their description also applies analogously to the embodiments shown in Figure 2illustrated embodiment applies, further comprises a further compressor stage 23, which adjoins the second compressor stage 22 and is configured to further compress the exhaust evaporation gas 5 further compressed in the second compressor stage 22, in order to provide an even further compressed exhaust evaporation gas 6. The further compressor stage 23 can - as indicated in Figure 2 by the dashed group with the reference number 20 - be part of the compressor, which also comprises the first and second compressor stages 21 and 22, respectively. Alternatively, however, it is also conceivable for the further compressor stage 23 to be part of a further compressor 20'. Downstream of the further compressor stage 23, a further heat exchanger 70 can optionally be arranged in order to cool or heat the exhaust evaporation gas 6 further compressed in the further compressor stage 23 before it is discharged to a consumer 80. The Figure 2The illustrated embodiment of the device 100 further comprises a reliquefaction device 50, which is arranged in a bypass line 40 and is designed to liquefy previously compressed evaporation gas. The bypass line 40 is fluidically connected to the container 10 in order to be able to return gaseous evaporation gas 7 or evaporation gas 7 reliquefied in the reliquefaction device 50 to the container 10. In the illustrated embodiment, the bypass line 40 branches off after the heat exchanger 70 arranged downstream of the further compressor stage 23. As still in Figure 4 will be described in more detail, it is also conceivable that the bypass line branches off the exhaust steam gas flow at another point of the device 100, in particular after the heat exchanger 60 arranged downstream of the second compressor stage 22 and upstream of the optionally present further compressor stage 23.

[0040] Figure 3ais a schematic representation of the material flows during the start-up phase of a process for compressing exhaust gas according to an embodiment of the present invention. To carry out the process described in Figure 3a In the method described, a device 100 is used which, in addition to the devices already described in connection with the Figure 1b elements described in the embodiment shown, the description of which also applies analogously to the Figure 3aillustrated embodiment applies, further comprises a first valve 41, a second valve 42, a first line 43 branching off upstream of the first compressor stage 21 and a line 44 opening downstream of the second compressor stage 22. The first valve 41 is arranged downstream of the first outlet 32 ​​of the heat exchanger 30 and upstream of the first compressor stage 21 and is designed to supply heated exhaust gas from the heat exchanger 30 to the first compressor stage 21 and / or the second compressor stage 22. In the Figure 3aIn the device shown, the first valve 41 is arranged in the line which fluidically connects the second outlet 34 of the heat exchanger and the second compressor stage 22, and is fluidically connected to the first outlet 32 ​​of the heat exchanger 30 via a first line 43 which branches off from the line connecting the first outlet 32 ​​of the heat exchanger 30 to the first compressor stage 21. The second valve 42 is arranged downstream of the first compressor stage 21, more precisely in the line fluidically connecting the first compressor stage 21 to the second inlet 33 of the heat exchanger. The second valve 42 is further fluidically connected to the device 100 via a second line 44 which opens downstream of the second compressor stage 22. The Figure 3aThe device 100 used in the process shown further comprises an optional bypass line 90 with a valve 91 arranged therein, with which the likewise optional heat exchanger 60 can be bridged. This allows flash gas in the tank to be minimized if the outlet temperature of the exhaust evaporation gas compressed in the first and second compressor stages 21, 22 is lower than the temperature of the heat exchanger cooling medium in heat exchanger 60. The material flows present when starting up the process, ie the path of the exhaust evaporation gas 1 through the device 100, are shown in Figure 3ashown in bold. The start-up of the process represents a state which exists before the start of the actual process for compressing exhaust steam gas. In this case, exhaust steam gas 1 accumulating in the container 10 is passed through the heat exchanger 30 via the first inlet 31 and is heated only due to the temperature difference between the cold exhaust steam gas and the heat exchanger which is at a warmer temperature, i.e. without heat exchange against exhaust steam gas compressed in the first compressor stage 21, as is the case after start-up of the process in normal operation of the device and the process. In addition to this heating of the exhaust steam gas, a cooling of the heat exchanger 30 takes place. The valve position of the first valve 41 is such that the exhaust steam gas is subsequently compressed in the first compressor stage 21 and in the second compressor stage 22.In principle, however, it is also conceivable for the valve position of the first valve 41 to be such that the exhaust evaporation gas is only fed to the first compressor stage. A person skilled in the art will understand that, by suitable adjustments to the positioning of the first valve in the device 100, it is also possible in principle to feed the exhaust evaporation gas only to the second compressor stage 22. The valve position of the second valve 42 is such that exhaust evaporation gas compressed in the first compressor stage is not conducted to the second inlet 33 of the heat exchanger 30, but via the second line 44 to a point after the second compressor stage 22, where the exhaust evaporation gas compressed in the first compressor stage flows into the line connecting the second compressor stage 22 to the heat exchanger 60 contained in this embodiment. As can be seen from the diagram in . Figure 3aAs can be seen from the material flow shown in bold, the exhaust steam gas compressed in the two compressor stages 21, 22 is fed via the bypass line 90, valve 91 and the bypass line 40 to the reliquefaction device 50. This results in recycling of the exhaust steam gas 1 from the container 10 back into the container 10 and / or into a Figure 3a additional containers not shown for cryogenic storage of liquefied petroleum gas or gas.

[0041] Figure 3b is a schematic representation of the material flows of the process from Figure 3a after the start-up phase, ie as it is the case after the process has started up in the normal operation of the device and the process. Unless otherwise stated below, the description of the Figure 3b elements shown again to the analogous description in the Figure 1b and 3a Compared to the Figure 3aThe valve position of the first valve 41 is determined in the manner described in Figure 3bdescribed method is changed such that the line connecting the first outlet 32 ​​of the heat exchanger 30 and the first compressor stage 21 is no longer fluidically connected to the second compressor stage 22. The valve position of the second valve 42 is changed such that the exhaust evaporation gas compressed in the first compressor stage 21 is fed to the heat exchanger 30 via its second inlet 33. Thus, exhaust evaporation gas 1 accumulating in the container 10 is now fed to the heat exchanger 30 via its first inlet 31 and heated by heat exchange with the exhaust evaporation gas compressed in the first compressor stage 21 in order to obtain a heated exhaust evaporation gas. On the other hand, the cooling of the exhaust evaporation gas compressed in the first compressor stage 21 in the heat exchanger 30 takes place by heat exchange with the exhaust evaporation gas 1, which accrues in the container 10 and is to be compressed in the first compressor stage 21.The exhaust steam gas compressed in the first compressor stage 21 and cooled against exhaust steam gas 1 from the vessel 10 leaves the heat exchanger via its second outlet 34 and is fed to the second compressor stage 22 in order to obtain a further compressed exhaust steam gas. Downstream of the second compressor stage 22, the further compressed exhaust steam gas is optionally cooled in heat exchanger 60 before it is made available to a consumer 80 of a downstream process. Alternatively, the even further compressed exhaust steam gas can be fed via the bypass line 40 to the reliquefaction device 50, which can in particular be a throttle valve. The cryogen recycled in this way is returned to the vessel 10 from which it originates. Alternatively or additionally, it is also conceivable for the liquefied exhaust steam gas to be fed into a . Figure 3b another container, not shown, for cryogenic storage of gas.

[0042] Figure 4a is a schematic representation of the material flows during the start-up phase of a process for compressing exhaust gas according to an embodiment of the present invention. To carry out the process described in Figure 4a In the method described, a device 100 is used which, in addition to the devices already described in connection with the Figure 2 elements described in the embodiment shown, the description of which also applies analogously to the Figure 4aillustrated embodiment applies, further comprises a first valve 41, a second valve 42, a first line 43 branching off upstream of the first compressor stage 21 and a line 44 opening downstream of the second compressor stage 22. The first valve 41 is arranged downstream of the first outlet 32 ​​of the heat exchanger 30 and upstream of the first compressor stage 21 and is designed to supply heated exhaust gas from the heat exchanger 30 to the first compressor stage 21 and / or the second compressor stage 22. In the Figure 4aIn the device shown, the first valve 41 is arranged in the line which fluidically connects the second outlet 34 of the heat exchanger and the second compressor stage 22, and is fluidically connected to the first outlet 32 ​​of the heat exchanger 30 via a first line 43 which branches off from the line connecting the first outlet 32 ​​of the heat exchanger 30 to the first compressor stage 21. The second valve 42 is arranged downstream of the first compressor stage 21, more precisely in the line fluidically connecting the first compressor stage 21 to the second inlet 33 of the heat exchanger. The second valve 42 is further fluidically connected to the bypass line 40 via a second line 44 which opens into the device 100 downstream of the second compressor stage 22. The material flows present when starting up the process, iethe path of the exhaust evaporation gas 1 through the device 100, are shown in bold in Figure 4a for improved clarity. The start-up of the process represents a state which exists before the start of the actual process for compressing exhaust evaporation gas. In this case, exhaust evaporation gas 1 accumulating in the container 10 is passed through the heat exchanger 30 via the first inlet 31 and is heated only due to the temperature difference between the cold exhaust evaporation gas and the heat exchanger which is at a warmer temperature, i.e. without heat exchange against exhaust evaporation gas compressed in the first compressor stage 21, as is the case after start-up of the process in normal operation of the device and the process. In addition to this heating of the exhaust evaporation gas, a cooling of the heat exchanger 30 takes place. The valve position of the first valve 41 is such that the exhaust evaporation gas is subsequently compressed in the first compressor stage 21 and in the second compressor stage 22.In principle, however, it is also conceivable for the valve position of the first valve 41 to be such that the exhaust evaporation gas is only fed to the first compressor stage. A person skilled in the art will understand that, by suitable adjustments to the positioning of the first valve in the device 100, it is also possible in principle to feed the exhaust evaporation gas only to the second compressor stage 22. The valve position of the second valve 42 is such that exhaust evaporation gas compressed in the first compressor stage is not conducted to the second inlet 33 of the heat exchanger 30, but via the second line 44 to a point after the second compressor stage 22, where the exhaust evaporation gas compressed in the first compressor stage flows into the line connecting the second compressor stage 22 to the heat exchanger 60. The valve position required to carry out the process described in . Figure 4aThe device 100 used in the method illustrated further comprises an optional bypass line 90 with a valve 91 arranged therein for bypassing the likewise optional heat exchanger 60 of the device 100. Downstream of the second compressor stage 22 or the heat exchanger 60, further compression optionally takes place in the further compressor stage 23 and then cooling in the heat exchanger 70. The device 100 can have a further bypass line 92 with a valve 93 arranged therein for bypassing the optional heat exchanger 70. By bypassing the heat exchangers 60 and 70, flash gas in the tank can be minimized if the outlet temperature of the exhaust gas compressed in the first and second compressor stages 21, 22 or in the third compressor stage 23 is lower than the temperature of the heat exchanger cooling medium in the heat exchanger 60 or in the heat exchanger 70.The exhaust evaporation gas is then fed to the reliquefaction device 50 via the bypass line 40. Thus, the exhaust evaporation gas 1 is recycled from the container 10 back into the container 10 and / or into a . Figure 4a additional containers not shown for cryogenic storage of liquefied petroleum gas or gas.

[0043] Figure 4b is a schematic representation of the material flows of the process from Figure 4a after the start-up phase, ie as it is the case after the process has started up in the normal operation of the device and the process. Unless otherwise stated below, the description of the Figure 4b elements shown again to the analogous description in the Figure 2 and 4a Compared to the Figure 4a The valve position of the first valve 41 is determined in the manner described in Figure 3bdescribed method is changed such that the line connecting the first outlet 32 ​​of the heat exchanger 30 and the first compressor stage 21 is no longer fluidically connected to the second compressor stage 22. The valve position of the second valve 42 is changed such that the exhaust evaporation gas compressed in the first compressor stage 21 is fed to the heat exchanger 30 via its second inlet 33. Thus, exhaust evaporation gas 1 accumulating in the container 10 is now fed to the heat exchanger 30 via its first inlet 31 and heated by heat exchange with the exhaust evaporation gas compressed in the first compressor stage 21 in order to obtain a heated exhaust evaporation gas. On the other hand, the cooling of the exhaust evaporation gas compressed in the first compressor stage 21 in the heat exchanger 30 takes place by heat exchange with the exhaust evaporation gas 1, which accrues in the container 10 and is to be compressed in the first compressor stage 21.The exhaust steam gas compressed in the first compressor stage 21 and cooled against exhaust steam gas 1 from the vessel 10 leaves the heat exchanger via its second outlet 34 and is fed to the second compressor stage 22 to obtain a further compressed exhaust steam gas. Downstream of the second compressor stage 22, the further compressed exhaust steam gas is optionally cooled in heat exchanger 60 and optionally further compressed in the further compressor stage 23 to obtain an even further compressed exhaust steam gas. The even further compressed exhaust steam gas can optionally be cooled in a heat exchanger 70 arranged downstream of the further compressor stage 23 before being made available to a consumer 80. Alternatively, the even further compressed exhaust steam gas can be fed via the bypass line 40 to the reliquefaction device 50, which can in particular be a throttle valve.The cryogen thus recycled is returned to the container 10 from which it originates. Alternatively or additionally, it is also conceivable that the liquefied evaporation gas is fed into a . Figure 4b another container, not shown, for cryogenic storage of gas.

[0044] Figure 5 is a flow diagram showing possible material flows that are conceivable in processes according to embodiments of the present invention. In particular, Figure 5The terminology used for the evaporation gas in the device or in and / or after the various process steps should be clarified again: Evaporation gas, which is produced by the evaporation of cryogenically stored gases LG due to the supply of ambient heat in the container 10, is referred to as "evaporation gas 1" up to the first outlet of the heat exchanger 30. Evaporation gas leaving the heat exchanger 30 via its first outlet is referred to herein as "heated evaporation gas 2" until the first compression of the evaporation gas in the first compressor stage 21 or - if the heated evaporation gas 2 is fed to the second compressor stage 22 instead of the first compressor stage 21, as described herein for some embodiments - in the second compressor stage 22. The evaporation gas obtained by compressing the heated evaporation gas 2 in the first compressor stage 21 is referred to as "compressed evaporation gas 3".If the heated exhaust steam gas 2 is fed to the second compressor stage 22 instead of the first compressor stage 21, the exhaust steam gas compressed in the second compressor stage 22 is referred to as "compressed exhaust steam gas 3" for easier differentiation from the exhaust steam gas 3 compressed in the first compressor stage. It is conceivable that the compressed exhaust steam gas 3 thus obtained is compressed in a further compressor stage 23, different from the second compressor stage 22, to form "further compressed exhaust steam gas 5" or is cooled in a reliquefaction device 50 to obtain "liquefied exhaust steam gas 7". Exhaust steam gas compressed in the first compressor stage 21, which leaves the heat exchanger 30 via its second outlet, is referred to herein as "cooled and compressed exhaust steam gas 4".The cooled and compressed exhaust steam gas 4 is fed to the second compressor stage 22 and, after being compressed by the second compressor stage 22, is referred to as "further compressed exhaust steam gas 5." It is also conceivable that the cooled and compressed exhaust steam gas 4 is fed to a further compressor stage 23 instead of the second compressor stage, for example, during maintenance work on the second compressor stage 22. If the cooled and compressed exhaust steam gas 4 is fed to a further compressor stage 23 instead of the second compressor stage 22, the exhaust steam gas compressed in the further compressor stage is referred to as "further compressed exhaust steam gas 5" to make it easier to distinguish from the exhaust steam gas 5 further compressed in the second compressor stage 22.The further compressed exhaust vapor gas 5, 5' can be made available to a consumer 80 or cooled in a reliquefaction device 50 to obtain "liquefied exhaust vapor gas 7" for return to the vessel 10. Optionally, the further compressed exhaust vapor gas 5, 5' can first be fed to a further compressor stage 23. In this case, after being compressed by the further compressor stage 23, it is referred to as "even further compressed exhaust vapor gas 6". In addition, the return of the exhaust vapor gas, in the gaseous state, to the vessel 10 can take place from the outlet of each of the described compressor stages 21, 22, 23, which is shown in FIG. 1 for improved clarity. Figure 5 is not shown separately.

Claims

1. A device (100) for compressing evaporation gas (1) of a cryogenically stored gas (LG), the device (100) comprising: - a container (10) for cryogenically stored gas (LG), the container (10) comprising an outlet (11) for discharging an evaporation gas (1) of the cryogenically stored gas (LG) that can be provided in the container (10); - a compressor (20) with at least one compressor stage (21), preferably with at least two compressor stages (21; 22); - a heat exchanger (30) for carrying out a heat exchange between the evaporation gas (1) and an evaporation gas (3) compressed in the first compressor stage (21);- wherein the heat exchanger (30) has a first inlet (31) for receiving the exhaust evaporation gas (1), a first outlet (32) for discharging a heated exhaust evaporation gas (2) to the first compressor stage (21), a second inlet (33) for receiving the exhaust evaporation gas (3) compressed in the first compressor stage (21), and a second outlet (34) for discharging a cooled and compressed exhaust evaporation gas (4) to a downstream process, in particular to a second compressor stage (22) of the compressor (20), wherein the second compressor stage (22) is configured to further compress the exhaust evaporation gas (4) compressed in the first compressor stage (21) and cooled in the heat exchanger (30) in order to provide a further compressed exhaust evaporation gas (5); 2. Device according to claim 1, wherein the cryogenically stored gas (LG) is selected from the group consisting of hydrogen, nitrogen, helium, neon, krypton, argon, liquefied natural gas, oxygen and mixtures thereof, wherein the cryogenically stored gas (LG) is preferably selected from the group consisting of hydrogen, helium, neon and mixtures thereof, wherein the cryogenically stored gas (LG) is particularly preferably hydrogen.

3. Device according to claim 1 or 2, wherein the heat exchanger is a counterflow heat exchanger, preferably a diffusion-welded counterflow heat exchanger.

4. Device according to one of the preceding claims, wherein a first valve (41) is arranged downstream of the first outlet (32) of the heat exchanger (30) and upstream of the first compressor stage (21), with which the heated exhaust evaporation gas (2) can be fed to the second compressor stage (22), wherein the first valve 41 can be arranged in particular in the line fluidically connecting the second outlet (34) of the heat exchanger (30) and the second compressor stage (22) and is fluidically connected to the first outlet (32) of the heat exchanger (30) via a first line (43), which branches off from the line connecting the first outlet (32) of the heat exchanger (30) to the first compressor stage (21).

5. Device according to one of the preceding claims, wherein the first outlet (32) of the heat exchanger (30) is or can be fluidically connected to the container (10) via a bypass line (40) arranged downstream of the first compressor stage (21) and / or downstream of the second compressor stage (22).

6. Device according to claim 5, wherein a second valve (42) is arranged downstream of the first compressor stage (21) and upstream of the second inlet (33) of the heat exchanger (30), with which second valve the exhaust evaporation gas (3) compressed in the first compressor stage (21) can be fed to the bypass line (40) instead of the second inlet (33) of the heat exchanger (30), in particular via a second line (44) opening downstream of the second compressor stage (22).

7. Device according to claim 5 or 6, wherein the bypass line (40) has a reliquefaction device (50) for previously compressed exhaust evaporation gas (3, 5, 6), in particular a throttle valve.

8. Device according to one of the preceding claims, wherein the container (10) for cryogenically stored gas (LG) is a mobile cryogenic tank, a storage tank of a liquefaction plant, or a storage tank of a transshipment terminal.

9. A method for compressing exhaust evaporation gas (1) of a cryogenically stored gas (LG), in particular carried out using a device according to one of claims 1 to 8, the method comprising the steps of: a) compressing exhaust evaporation gas (1), which accrues in a container (10) with cryogenically stored gas (LG), in a first compressor stage (21) of a compressor (20), preferably a compressor (20) comprising at least two compressor stages (21, 22); b) cooling the exhaust evaporation gas (3) compressed in the first compressor stage (21) in a heat exchanger (30); and c) delivering the exhaust evaporation gas (4) compressed in the first compressor stage (21) and cooled in step b) to a downstream process, in particular to a second compressor stage (22) of the compressor (20) to obtain a further compressed exhaust evaporation gas (5);wherein the exhaust evaporation gas (1) is heated in the heat exchanger (30) before its compression in step a) by heat exchange with the exhaust evaporation gas (3) compressed in the first compressor stage (21) in order to obtain a heated exhaust evaporation gas (2), and wherein in step b) the cooling of the exhaust evaporation gas (3) compressed in the first compressor stage (21) takes place in the heat exchanger (30) by heat exchange with the exhaust evaporation gas (1) which arises in the container (10) and is to be compressed in the first compressor stage (21); 10. The method according to claim 9, wherein the cryogenically stored gas (LG) is selected from the group consisting of hydrogen, nitrogen, helium, neon, krypton, argon, liquefied natural gas, oxygen and mixtures thereof, wherein the cryogenically stored gas (LG) is preferably selected from the group consisting of hydrogen, helium, neon and mixtures thereof, wherein the cryogenically stored gas (LG) is particularly preferably hydrogen.

11. The method according to claim 9 or 10, wherein the heat exchange between the exhaust steam gas (1) and the exhaust steam gas (3) compressed in the first compressor stage (21) takes place according to the countercurrent principle, preferably using a diffusion-welded heat exchanger.

12. The method according to any one of claims 9 to 11, wherein the evaporation gas (1) accumulating in the container (10) has a temperature between -272 °C and -160 °C, and wherein the evaporation gas (1) heated by heat exchange has a temperature between -196 °C and -120 °C, in particular a temperature between -180 °C and -140 °C, before its compression in step a).

13. The method according to any one of claims 9 to 12, wherein the exhaust gas (4) compressed in the first compressor stage (21) and cooled in step b) is provided to the second compressor stage (22) at a temperature between -170 °C and -60 °C.

14. The method according to any one of claims 9 to 13, wherein the exhaust evaporation gas (1) is used for a predetermined time, in particular until a predetermined temperature is reached at a first inlet (31) of the heat exchanger (30) for receiving the exhaust evaporation gas (1) and / or at a first outlet (32) of the heat exchanger (30) for discharging the heated exhaust evaporation gas (2) to the first compressor stage (21), for cooling the heat exchanger (30) before it is used in step b) for cooling the exhaust evaporation gas (3) compressed in the first compressor stage (21).

15. Method according to one of claims 9 to 14, wherein the exhaust evaporation gas (3; 5) compressed in at least one of the two compressor stages (21; 22) is re-liquefied and returned to the container (10).

Images