Device and method for compressing boil-off gas

Abstract

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

Description

[0001] Device and method for compressing exhaust steam gases

[0002] The present invention relates to a device and a method for compressing evaporation gas of a cryogenically stored gas.

[0003] Facilities that process or consume large quantities of gas are usually supplied with liquefied petroleum gas stored at cryogenic temperatures because it is easier to transport and deliver than large quantities of compressed gas. However, the use of liquid gas kept at low temperatures has the problem that, even when properly stored in a suitable storage vessel, the gas warms up due to heat from the environment and vaporizes, leading to a continuous increase in 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, which is also referred to as boil-off gas or "BOG", must either be vented from the storage vessels or used.Usually, 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.

[0004] As the temperature of the exhaust steam gas is generally 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 colder. 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 work 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 in the compressor is adjusted using preheating systems. The energy required to increase the temperature of the exhaust steam gas in the preheating systems is provided, for example, by a heat pump.by extracting heat from the environment or using an electrical preheating device. However, such devices have the disadvantage of being energy-intensive and wasting the cold contained in the exhaust gas.

[0005] Starting from the cited prior art, the object of the present invention is to mitigate or even eliminate these and other disadvantages of the prior art and to provide a device of the type mentioned at the outset 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 can be dispensed with because they are particularly stable at low temperatures, in particular at temperatures below approximately -196 ° C. It is a further object of the present invention to specify a method for compressing evaporation gas from a cryogenically stored gas which, in comparison to the methods known from the prior art, has higher compression and energy efficiency and does not require the use of expensive low-temperature-resistant materials.

[0006] 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.

[0007] 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 made available 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 carrying out 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.

[0008] In contrast to prior art devices for compressing exhaust steam gas, such a device is characterized by the fact that refrigeration management is purely internal to 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 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 there is no need to purchase and operate a preheater with an external heat source and the energy for preheating the exhaust steam gas does not have to be used separately because it is provided by the first compressor stage. The measures mentioned above enable an increase in energy efficiency of up to 20% compared to prior art devices in which the exhaust steam gas is preheated before compression. A further advantage of such a device is that the compressor, and in particular the first compressor stage of the compressor, is not exposed to the low temperatures of the exhaust steam gas.This is particularly relevant for gases whose boiling point is lower than that of nitrogen, since the materials typically used in compressors cannot withstand temperatures below approximately -196 °C or are very expensive. These very expensive materials, which function even at very cold exhaust gas temperatures, can thus be dispensed with in the design of compressors.

[0009] 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 such 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.

[0010] 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 conventionally required, low-temperature-resistant and expensive materials, particularly for the compressor, can be dispensed with.

[0011] Particularly preferred is the cryogenically stored

[0012] Gas around hydrogen.

[0013] 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.

[0014] The heat exchanger is preferably a diffusion-welded counterflow heat exchanger. Fusion-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 extraordinarily high heat transfer rate with correspondingly high efficiencies. Due to these properties, fusion-welded heat exchangers can be cooled down within a relatively short time, which is particularly advantageous when starting up the process described in more detail below. In addition, fusion-welded heat exchangers are characterized by a very broad performance window compared to conventional tube bundle heat exchangers and a significantly higher 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.

[0015] 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 required to start the process.

[0016] 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 designed 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, for the first compressor stage to be serviced without the need to temporarily store or dispose of exhaust evaporation gas still accumulating in the vessel.

[0017] 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.

[0018] 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 exhaust evaporation gas compressed 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.

[0019] 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 designed to feed the exhaust steam gas compressed in the first compressor stage to the bypass line instead of the second inlet of the heat exchanger. Such a bypass line makes it possible to return compressed exhaust steam gas to the container without exhaust steam gas compressed in the first and / or second compressor stage being used to heat fresh exhaust steam 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 steam 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.

[0020] In embodiments of the device, the bypass line can have a reliquefaction device for previously compressed evaporation gas. The reliquefaction device makes it possible to return evaporation gas to the vessel in cryogenic form if it is not used by a consumer after compression. The reliquefaction device can, in particular, be a throttle valve.

[0021] 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.

[0022] 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 designed to compress the exhaust steam gas compressed in the first compressor stage and cooled in the heat exchanger. This makes it possible for the second compressor stage to be taken out of operation, for example for maintenance purposes. Additionally or alternatively, the further compressor stage is designed to further compress the exhaust steam gas further compressed in the second compressor stage in order to provide an even more compressed exhaust steam gas.The presence of an additional compressor stage increases the operational flexibility of the device, since it can be used to provide an even more compressed exhaust gas, for example depending on the pressure requirements of different users.

[0023] The object is further achieved by a method for compressing exhaust vapor gas of a cryogenically stored gas. The method comprises the steps of: a) compressing exhaust vapor gas which arises 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 vapor gas compressed in the first compressor stage in a heat exchanger; and c) passing the exhaust vapor gas compressed in the first compressor stage and cooled in step b) to a downstream process. In particular, in the downstream process the exhaust vapor 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 vapor gas.

[0024] According to the inventive method, 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, in order 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 which accrues in the container and is to be compressed in the first compressor stage.

[0025] With this method, the advantages already disclosed for the device disclosed herein can be achieved.

[0026] 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.

[0027] 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. The cryogenically stored gas is preferably selected from the group consisting of hydrogen, helium, neon, and mixtures thereof. The cryogenically stored gas is particularly preferably hydrogen. Here, too, the advantages of the process according to the invention become apparent, particularly with low-boiling gases, which would normally require the use of particularly low-temperature-stable and expensive materials, particularly for the compressor.

[0028] In one embodiment of the process, 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. The heat exchange between the exhaust steam gas and the exhaust steam gas compressed in the first compressor stage preferably takes place using a diffusion-welded heat exchanger. This makes it possible to achieve the advantages described in connection with the corresponding embodiments of the device disclosed herein. For reasons of occupational safety, the exhaust steam gas should be heated to temperatures which are higher than the temperatures at which nitrogen and / or oxygen condense. Since heat is generated when a gas is compressed and higher temperatures can also have a detrimental effect on the compressor efficiency and the materials used in the compressor, the aim should be to compress the coolest possible gas.

[0029] In one embodiment of the process, the evaporative gas accumulating in the vessel has a temperature of between -272 °C and -160 °C. The evaporative gas heated by heat exchange has a temperature of between -196 °C and -120 °C before it is compressed in step a), i.e. before it is compressed in the first compressor stage of the multi-stage compressor. In this temperature range, the use of particularly low-temperature-stable and therefore expensive materials in the compressor is not necessary. The nevertheless low temperature range is also advantageous for the compression of an evaporative gas because 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 the thermal load on the compressor components, which can extend their service life.

[0030] In particular, an embodiment of the method is disclosed in which the exhaust gas heated by heat exchange has a temperature of 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, in particular in the case that the cryogenically stored gas is hydrogen, since on the one hand it eliminates the use of expensive materials and on the other hand the efficiency of the first compressor stage remains high.

[0031] 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. In this temperature range, efficient compression can be achieved by the second compressor stage.

[0032] 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.

[0033] Typical final pressures required by typical users for compressed exhaust gas are: between 30 bar and 100 bar, in particular around 60 bar, for injection into pipelines; between 350 bar and 800 bar in 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 in fuel gas supply, in particular for liquid hydrogen gensets or fuel cell gas turbines.

[0034] 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.

[0035] 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 steam 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 steam gas to the first compressor stage. This ensures that the temperature of the exhaust steam gas supplied to the first compressor stage is compatible with the materials used in the first compressor stage of the compressor.

[0036] In one embodiment of the process, the exhaust gas is liquefied in a reliquefaction device and returned to the container after it has been 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.

[0037] The present invention is described below by way of example with reference to figures. Unless otherwise stated, the same reference numerals always designate components of the same embodiment. These show: Figure 1a: a schematic representation of a device for compressing exhaust gas according to an embodiment of the present invention;

[0038] Figure 1b Schematic representation of a device for compressing exhaust evaporation gas according to a further embodiment of the present invention;

[0039] Figure 2 Schematic representation of a device for compressing exhaust evaporation gas according to a further embodiment of the present invention;

[0040] Figure 3a Schematic representation of the material flows during

[0041] Start-up phase of a method for compressing exhaust gas according to an embodiment of the present invention;

[0042] Figure 3b Schematic representation of the material flows of the process from Figure 3a after the start-up phase;

[0043] Figure 4a Schematic representation of the material flows during the start-up phase of a process for compressing exhaust steam gas according to a further embodiment of the present invention;

[0044] Figure 4b Schematic representation of the material flows of the process from Figure 4a after the start-up phase;

[0045] Figure 5 Flow diagram of possible material flows in processes according to embodiments of the present invention.

[0046] Figure 1a is a schematic representation of an embodiment of a device for compressing exhaust vapor gas of a cryogenically stored gas. As shown in Figure 1a, the device 100 comprises a container 10 for cryogenically stored gas LG. Exhaust vapor gas 1 of the cryogen provided in the container arises in the container and 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 also 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.The first inlet 31 of the heat exchanger 30 is designed to receive the exhaust steam 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 deliver the exhaust steam gas 2, which has flowed through the heat exchanger 30, to the first compressor stage 21. The first compressor stage 21 is in turn fluidly 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 designed to receive the exhaust steam gas 3 compressed in the first compressor unit 21 and is in turn fluidly 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 released 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.

[0047] Figure 1b is a schematic representation of a further example of a device for compressing exhaust vapor gas of a cryogenically stored gas. As shown in Figure 1b, the device 100 comprises a container 10 for cryogenically stored gas LG. Exhaust vapor gas 1 of the cryogen provided in the container arises in the container and 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 via the outlet 11 to a first inlet 31 of the heat exchanger 30. The first inlet 31 of the heat exchanger 30 is designed accordingly 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 steam 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 fluidly connected to the second compressor stage 22 and is designed to discharge the exhaust 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 set up to further compress the exhaust steam gas 4 compressed in the first compressor stage 21 and cooled in the heat exchanger 30 in order to provide a further compressed exhaust steam gas 5. Downstream of the second compressor stage 22, a further heat exchanger 60 can optionally be arranged in order to temperature-control the exhaust steam gas 5 further compressed in the second compressor stage 22 before it is released to a consumer 80. The gas stored cryogenically in the container 10 can in particular be hydrogen. The pressure of the exhaust steam gas 1 in the head space of the container 10 can be between 1.01 and 20 bara, in particular approximately 8 bara.

[0048] Figure 2 is a schematic representation of an example of a further device for compressing exhaust evaporation gas of a cryogenically stored gas. As shown in Figure 2, the device 100 comprises, in addition to the elements which have already been described in connection with the embodiment shown in Figure 1 and whose description also applies analogously to the embodiment shown in Figure 2, a further compressor stage 23 which is connected to the second compressor stage 22 and is designed 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 group shown in dashed lines with the reference symbol 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'. A further heat exchanger 70 can optionally be arranged downstream of the further compressor stage 23 in order to cool or heat the exhaust steam gas 6 further compressed in the further compressor stage 23 before it is delivered to a consumer 80. The embodiment of the device 100 shown in Figure 2 further comprises a reliquefaction device 50 which is arranged in a bypass line 40 and is designed to liquefy previously compressed exhaust steam gas. The bypass line 40 is fluidically connected to the container 10 in order to be able to return gaseous exhaust steam gas 7 or exhaust steam 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.However, as will be described in more detail in Figure 4, it is also conceivable that the bypass line branches off the exhaust steam gas flow at another point in 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.

[0049] Figure 3a is a schematic representation of the material flows during the start-up phase of a method for compressing exhaust steam gas according to one embodiment of the present invention. To carry out the method shown in Figure 3a, a device 100 is used which, in addition to the elements already described in connection with the embodiment shown in Figure 1b, the description of which also applies analogously to the embodiment shown in Figure 3a, 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 steam gas from the heat exchanger 30 to the first compressor stage 21 and / or the second compressor stage 22. In the device shown in Figure 3a, 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 opening downstream of the second compressor stage 22. The device 100 used to carry out the process shown in Figure 3a 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 makes it possible to minimize flash gas in the tank 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 the heat exchanger 60. The material flows present when starting up the process, i.e. the path of the exhaust evaporation gas 1 through the device 100, are shown in bold in Figure 3a for improved clarity. The start-up of the process represents a condition 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 method. In addition to this heating of the exhaust steam gas, the heat exchanger 30 is cooled. 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 steam 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 in principle also possible to feed the exhaust steam gas only to the second compressor stage 22. The valve position of the second valve 42 is such that exhaust steam 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 steam gas compressed in the first compressor stage opens into the line connecting the second compressor stage 22 to the heat exchanger 60 included in this embodiment. As can be seen from the material flow shown in bold in Figure 3a, the exhaust steam gas compressed in the two compressor stages 21, 22 is fed to the reliquefaction device 50 via the bypass line 90, valve 91 and the bypass line 40.Thus, the evaporation gas 1 from the container 10 is recycled back into the container 10 and / or into another container not shown in Figure 3a for the cryogenic storage of liquefied gas or gas.

[0050] Figure 3b is a schematic representation of the material flows of the process from Figure 3a after the start-up phase, i.e. as is the case after start-up of the process in normal operation of the device and the process. Unless stated otherwise below, for the description of the elements shown in Figure 3b reference is again made to the analogous description in Figures 1b and 3a. In comparison to the process described in Figure 3a, the valve position of the first valve 41 in the process described in Figure 3b 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 steam gas compressed in the first compressor stage 21 is fed to the heat exchanger 30 via its second inlet 33.Thus, exhaust steam gas 1 accumulating in the tank 10 is now fed to the heat exchanger 30 via its first inlet 31 and heated by heat exchange with the exhaust steam gas compressed in the first compressor stage 21 in order to obtain a heated exhaust steam gas. On the other hand, the exhaust steam gas compressed in the first compressor stage 21 is cooled in the heat exchanger 30 by heat exchange with the exhaust steam gas 1 which accrues in the tank 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 tank 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 container 10 from which it originates. Alternatively or additionally, it is also conceivable for the liquefied exhaust steam gas to be fed into a further container (not shown in Figure 3b) for the cryogenic storage of gas.

[0051] 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 shown in Figure 4a, a device 100 is used which, in addition to the devices already described in

[0052] In connection with the embodiment shown in Figure 2, the description of which also applies analogously to the elements shown in

[0053] Figure 4a applies, further comprising 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 steam gas from the heat exchanger 30 to the first compressor stage 21 and / or the second compressor stage 22.4a, 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 which fluidically connects 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 the process is started up, i.e. h .The path of the exhaust evaporation gas 1 through the device 100 is shown in bold in Figure 4a for improved clarity. The start-up of the process represents a state that exists before the actual process for compressing exhaust evaporation gas begins. Exhaust evaporation gas 1 accumulating in the vessel 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 with the first compressor stage.

[0054] 21 compressed exhaust gas , as is the case after start-up of the process in the regular operation of the device and the method . In addition to this heating of the exhaust gas , a cooling of the heat exchanger 30 takes place . The valve position of the first valve 41 is such that the exhaust gas is subsequently in the first compressor stage 21 and in the second compressor stage

[0055] 22 is compressed. In principle, however, it is also conceivable for the valve position of the first valve 41 to be such that the exhaust steam 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 steam gas only to the second compressor stage 22. The valve position of the second valve 42 is such that exhaust steam 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 steam gas compressed in the first compressor stage flows into the line connecting the second compressor stage 22 to the heat exchanger 60.The device 100 used to carry out the method shown in Figure 4a 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 gas in the first and second compressor stages 21, 22 and 23, respectively, is below 0. of the exhaust steam gas compressed in the third compressor stage 23 is smaller than the temperature of the heat exchanger cooling medium in heat exchanger 60 or in heat exchanger 70.The exhaust gas is then fed to the reliquefaction device 50 via the bypass line 40. Thus, the exhaust gas 1 is recycled from the container 10 back into the container 10 and / or into another container (not shown in Figure 4a) for the cryogenic storage of liquefied gas or gas.

[0056] Figure 4b is a schematic representation of the material flows of the process from Figure 4a after the start-up phase, i.e. as is the case after start-up of the process in normal operation of the device and the process. Unless stated otherwise below, for the description of the elements shown in Figure 4b reference is again made to the analogous description in Figures 2 and 4a. In comparison to the process described in Figure 4a, the valve position of the first valve 41 in the process described in Figure 3b 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 steam gas compressed in the first compressor stage 21 is fed to the heat exchanger 30 via its second inlet 33.Thus, exhaust steam gas 1 accumulating in the tank 10 is now fed to the heat exchanger 30 via its first inlet 31 and heated by heat exchange with the exhaust steam gas compressed in the first compressor stage 21 in order to obtain a heated exhaust steam gas. On the other hand, the exhaust steam gas compressed in the first compressor stage 21 is cooled in the heat exchanger 30 by heat exchange with the exhaust steam gas 1 which accrues in the tank 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 tank 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 and optionally further compressed in the further compressor stage 23 in order to obtain an even more compressed exhaust steam gas. The even more compressed exhaust steam gas can optionally be cooled in a heat exchanger 70 arranged downstream of the further compressor stage 23 before it is made available to a consumer 80. Alternatively, the even more 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 container 10 from which it originates. Alternatively or additionally, it is also conceivable for the liquefied exhaust steam gas to be fed into a further container (not shown in Figure 4b) for the cryogenic storage of gas.

[0057] 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 5 is intended to clarify the terminology used for the evaporation gas in the device or in and / or after the various process steps: 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.Exhaust steam gas leaving the heat exchanger 30 via its first outlet is referred to herein as "heated exhaust steam gas 2" until the first compression of the exhaust steam gas in the first compressor stage 21 or - if the heated exhaust steam 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 exhaust steam gas obtained by compressing the heated exhaust steam gas 2 in the first compressor stage 21 is referred to as "compressed exhaust steam 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" to make it easier to distinguish it from the exhaust steam gas 3 compressed in the first compressor stage.It is conceivable that the compressed exhaust steam gas 3 ' obtained in this way is compressed in a further compressor stage 23 which is different from the second compressor stage 22 to form "further compressed exhaust steam gas 5 "' or is cooled in a reliquefaction device 50 in order 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 it from the exhaust steam gas 5 further compressed in the second compressor stage 22. The further compressed exhaust steam gas 5, 5' can be made available to a consumer 80 or cooled in a reliquefaction device 50 to obtain "liquefied exhaust steam gas 7" for return to the container 10. Optionally, the further compressed exhaust steam gas 5, 5' can be fed to a further compressor stage 23 beforehand. In this case, after it has been compressed by the further compressor stage 23, it is referred to as "even further compressed exhaust steam gas 6".In addition, the exhaust steam gas can be returned, in the gaseous aggregate state, to the container 10 from the outlet of each of the described compressor stages 21, 22, 23, which is not shown separately in Figure 5 for the sake of clarity.

Claims

Patent claims 1. 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 exhaust steam gas (1) and an exhaust steam 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 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).

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 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 at a transshipment terminal.

9. A method for compressing exhaust evaporation gas (1) of a cryogenically stored gas (LG), in particular carried out with a device according to one of claims 1 to 8, the method comprising the steps: a) compressing exhaust evaporation gas (1), which is obtained 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) Discharge of 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) by heat exchange with the exhaust evaporation gas (3) compressed in the first compressor stage (21) before its compression in step a) 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) produced in the container (10) has a temperature between -272 °C and -160 °C, and wherein the Heat exchange heated exhaust steam gas (1) before its compression in step a) has a temperature between -196 °C and -120 °C, in particular a temperature between -180 °C and -140 °C.

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. Method according to one of claims 9 to 13, wherein the exhaust evaporation gas (1) is heated 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) is used to cool the heat exchanger (30) before it is used in step b) to cool the exhaust steam gas (3) compressed in the first compressor stage (21).

15. The method according to any 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 reliquefied and returned to the container (10).

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