Evaporative gas treatment method and evaporative gas treatment system

Abstract

To provide a method and a system that can treat residual gas without reducing the treatment efficiency of evaporation gas and efficiently treat the evaporation gas.SOLUTION: An evaporation gas treatment method uses an evaporation gas treatment system 1 that includes a drawing line 7, two adsorption vessels 9, a delivery pump 11, a cryogenic liquid delivery line 13, a heat exchanger 15, and a circulation line 17. The method comprises: an adsorption process of adsorbing an evaporation gas in each of the adsorption vessels 9; a desorption process of desorbing the evaporation gas and introducing the evaporation gas raised in pressure by desorption into the cryogenic liquid delivery line 13; and a residual gas process of discharging the residual gas into the circulation line 17. The evaporation gas is continuously drawn by alternating the adsorption process in the two adsorption vessels 9, and the adsorption process carried out in one adsorption vessel 9 while the desorption process and the residual gas process are carried out in the other adsorption vessel 9, thereby introducing the residual gas in the other adsorption vessel 9 via circulation line 17 into the one adsorption vessel 9 performing the adsorption process.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an evaporation gas processing method and an evaporation gas processing system for processing evaporation gas generated in a storage tank in which a low-temperature liquid such as liquefied natural gas is stored. [Background technology]

[0002] Natural gas (NG), the raw material for city gas production, is imported and stored in Japan as liquefied natural gas (LNG). Tanks insulated with insulating materials are used to store low-temperature liquids such as LNG, but when heat enters the tank, some of the low-temperature liquid evaporates, generating boil-off gas (BOG) inside the tank. If this boil-off gas increases the internal pressure of the tank, there is a risk of the tank being damaged and resulting gas leaks and explosions. To prevent this, it is necessary to remove the boil-off gas from the tank in some way.

[0003] The simplest method for removing evaporated gas from inside a tank is to release it outside the tank, but if the evaporated gas is flammable or toxic, such as in the case of natural gas, it is not desirable to release it into the atmosphere. In addition, if the evaporated gas is flammable, there is also a method called flare purging, but this is also undesirable from the viewpoint of efficient use of raw materials and air pollution. Therefore, as a method for effectively utilizing evaporated gas, it is common to introduce the evaporated gas recovered from the tank into the gas in the gas delivery pipeline, or into the LNG before vaporization in the gas delivery pipeline to re-liquefy it. In this case, since the pressure of the evaporated gas in the storage tank is lower than the pressure in the gas delivery pipeline, it is necessary to increase the pressure of the evaporated gas using a gas compressor or the like before introducing it into the gas delivery pipeline.

[0004] Patent Document 1 discloses a technology for efficiently treating evaporated gas, in which some of the liquefied gas in a tank is replenished into another tank (hereinafter referred to as the "cooling tank"), a container filled with an adsorbent (hereinafter referred to as the "adsorption vessel") is submerged in the cooling tank to cool the adsorbent, the evaporated gas is adsorbed onto the cooled adsorbent, and the adsorption vessel is then heated to desorb and pressurize the evaporated gas before introducing it into a gas delivery pipeline. The method of Patent Document 1 utilizes the property that the lower the temperature of the adsorbent, the greater the amount of gas adsorbed. After adsorbing the evaporated gas at a low temperature, the adsorption vessel is heated to desorb the evaporated gas and increase the pressure inside the vessel, allowing the evaporated gas to be sent to a gas delivery pipeline without having to increase the pressure using a gas compressor or the like. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 4885465 Summary of the Invention [Problem to be solved by the invention]

[0006] As described above, the method of Patent Document 1 involves cooling the adsorption vessel to adsorb and recover the evaporated gas, then heating the adsorption vessel to desorb the evaporated gas, and introducing the evaporated gas pressurized by the desorption (hereinafter referred to as "desorbed gas") into a gas delivery pipeline. In this case, as the amount of evaporated gas in the adsorption vessel decreases with the progress of desorption, the pressure of the desorbed gas gradually decreases accordingly. When the pressure of the desorbed gas falls below the pressure of the gas delivery pipeline, it becomes impossible to introduce the desorbed gas into the gas delivery pipeline, so the discharge of the desorbed gas is stopped when a predetermined amount has been discharged.

[0007] When the discharge of desorbed gas has been stopped, evaporated gas remains in the adsorption vessel at a pressure equivalent to that of the gas delivery pipeline (hereinafter referred to as "residual gas"). In order to recover evaporated gas from the LNG tank again, it is necessary to process the remaining gas in the adsorption vessel and reduce the pressure until it is equivalent to the internal pressure of the LNG tank.

[0008] In this regard, in Patent Document 1, the adsorption vessel is re-cooled by re-supplying LNG to the cooling tank, so that the residual gas is adsorbed into the adsorbent and reduced in pressure. However, when the adsorption vessel is re-cooled, the LNG supplied to the cooling tank evaporates and new evaporated gas is generated in the cooling tank, resulting in a problem in that the efficiency of evaporative gas processing is reduced.

[0009] The present invention has been made to solve such problems, and aims to provide an evaporative gas processing method and an evaporative gas processing system that can process residual gas without reducing the processing efficiency of the evaporative gas and can efficiently process the evaporative gas. [Means for solving the problem]

[0010] (1) The evaporation gas treatment method according to the present invention is a method for treating the evaporation gas using an evaporation gas treatment system including an extraction line for extracting the evaporation gas generated from a storage tank in which a cryogenic liquid is stored, two adsorption vessels containing an adsorbent for adsorbing the evaporation gas, an output pump for outputting the cryogenic liquid from the storage tank, a cryogenic liquid output line through which the cryogenic liquid output by the output pump flows, a heat exchanger provided in the cryogenic liquid output line for performing heat exchange using the cold heat of the cryogenic liquid, and a circulation line connected to the heat exchanger and the two adsorption vessels, for introducing the evaporation gas extracted from the extraction line and circulating the evaporated gas between one of the two adsorption vessels and the heat exchanger, wherein in each of the adsorption vessels, The system comprises an adsorption process in which the evaporated gas flowing through the adsorption vessel is adsorbed onto the adsorbent, a desorption process in which the evaporated gas adsorbed in the adsorption process is heated to desorb from the adsorbent and the evaporated gas pressurized by the desorption is introduced into the low-temperature liquid delivery line or into a system having a higher pressure than the pressure in the storage tank, and a residual gas process in which, after the desorption process, the residual gas remaining in the adsorption vessel is discharged into the circulation line to reduce the pressure inside the adsorption vessel. By alternately performing the adsorption processes in the two adsorption vessels, the evaporated gas is continuously extracted from the storage tank, and while the adsorption process is being performed in one adsorption vessel, the desorption process and the residual gas process are performed in the other adsorption vessel, so that the residual gas in the other adsorption vessel is introduced via the circulation line into the one adsorption vessel undergoing the adsorption process.

[0011] (2) Furthermore, the evaporative gas treatment system of the present invention treats evaporative gas generated from a storage tank in which a cryogenic liquid is stored, and is characterized in that it comprises an extraction line for extracting the evaporative gas generated from the storage tank, three or more adsorption vessels containing an adsorbent for adsorbing the evaporative gas, a delivery pump for delivering the cryogenic liquid from the storage tank, a cryogenic liquid delivery line through which the cryogenic liquid delivered by the delivery pump flows, a heat exchanger provided in the cryogenic liquid delivery line for heat exchange using the cold heat of the cryogenic liquid, and a circulation line connected to the heat exchanger and the three or more adsorption vessels, which introduces the evaporative gas extracted from the extraction line and circulates it between at least one of the three or more adsorption vessels and the heat exchanger.

[0012] (3) Furthermore, the evaporative gas processing method of the present invention is a method for processing evaporative gas using the evaporative gas processing system described in (2) above, which performs, in each of the adsorption vessels, an adsorption process in which the evaporative gas flowing through the circulation line is adsorbed by the adsorbent, a desorption process in which the evaporative gas adsorbed in the adsorption process is heated and desorbed from the adsorbent and the evaporative gas whose pressure has been increased by the desorption is introduced into the low-temperature liquid delivery line or a system having a higher pressure than the pressure in the storage tank, and a residual gas process in which, after the desorption process, the residual gas remaining in the adsorption vessel is discharged into the circulation line to reduce the pressure inside the adsorption vessel, characterized in that the adsorption processes are performed sequentially in the three or more adsorption vessels to continuously extract the evaporative gas from the storage tank, and while the residual gas process is performed in at least one adsorption vessel, the adsorption process is performed in one of the remaining adsorption vessels, so that the residual gas in one of the adsorption vessels is introduced via the circulation line to one of the two or more adsorption vessels undergoing the adsorption process. Effect of the Invention

[0013] In the present invention, adsorption treatment is performed alternately in two adsorption vessels, thereby continuously extracting evaporative gas from the storage tank, and while adsorption treatment is performed in one adsorption vessel, desorption treatment and residual gas treatment are performed in the other adsorption vessel, so that the residual gas in the other adsorption vessel is introduced via a circulation line into the one adsorption vessel undergoing adsorption treatment. This makes it possible to treat the residual gas without reducing the efficiency of evaporative gas treatment, and therefore enables efficient treatment of evaporative gas. [Brief description of the drawings]

[0014] [Figure 1] FIG. 1 is an explanatory diagram of an evaporated gas processing method according to a first embodiment of the present invention. [Diagram 2] FIG. 1 is an explanatory diagram of an evaporative gas processing system according to a first embodiment of the present invention. [Diagram 3] FIG. 3 is a diagram showing a state 1 in the evaporative gas processing system of FIG. 2. [Figure 4] 3 is a diagram showing a state 2 in the evaporative gas treatment system of FIG. 2. FIG. [Diagram 5] 3 is a diagram showing a state 3 in the evaporative gas processing system of FIG. 2. FIG. [Figure 6] 3 is a diagram showing a state 4 in the evaporative gas processing system of FIG. 2. FIG. [Figure 7] 3 is a diagram showing a state 5 in the evaporative gas processing system of FIG. 2. FIG. [Figure 8] FIG. 3 is an explanatory diagram for explaining a problem in the evaporative gas processing system of FIG. 2. [Figure 9] FIG. 11 is an explanatory diagram of an evaporative gas processing system according to a second embodiment of the present invention. [Figure 10] FIG. 6 is an explanatory diagram of an evaporated gas processing method according to a second embodiment of the present invention. [Figure 11] FIG. 10 is a diagram showing a state 1 in the evaporative gas processing system of FIG. [Figure 12] 10 is a diagram showing a state 2 in the evaporative gas processing system of FIG. 9. FIG. [Figure 13] 10 is a diagram showing a state 3 in the evaporative gas processing system of FIG. 9. FIG. [Figure 14] 10 is a diagram showing a state 4 in the evaporative gas processing system of FIG. 9. FIG. [Figure 15] 10 is a diagram showing a state 5 in the evaporative gas processing system of FIG. 9. FIG. [Figure 16] 10 is a diagram showing a state 6 in the evaporative gas processing system of FIG. 9. FIG. [Figure 17] 10 is a diagram showing a state 7 in the evaporative gas processing system of FIG. 9. FIG. [Figure 18] 10 is a diagram showing a state 8 in the evaporative gas processing system of FIG. 9. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] [Embodiment 1] The evaporative gas processing method according to this embodiment is a method for processing evaporative gas generated from a storage tank in which a low-temperature liquid is stored, using an evaporative gas processing system 1 as shown in Fig. 2. Before describing the evaporative gas processing method according to this embodiment, the evaporative gas processing system 1 according to this embodiment will first be specifically described below with reference to Fig. 2.

[0016] The evaporative gas treatment system 1 comprises an extraction line 7 for extracting evaporative gas generated from a storage tank 5 in which a low-temperature liquid 3 such as LNG is stored, two adsorption vessels 9 containing an adsorbent that adsorbs the evaporative gas, a delivery pump 11 for delivering the low-temperature liquid 3 from the storage tank 5, a low-temperature liquid delivery line 13 through which the low-temperature liquid 3 delivered by the delivery pump 11 flows, a heat exchanger 15 provided in the low-temperature liquid delivery line 13 for heat exchange using the cold energy of the low-temperature liquid 3, and a circulation line 17 connected to the heat exchanger 15 and the two adsorption vessels 9 and for introducing the evaporative gas extracted from the extraction line 7 and circulating it between one of the two adsorption vessels 9 and the heat exchanger 15.

[0017] <Extraction line> The extraction line 7 is a line for extracting, from the storage tank 5, the evaporated gas (generally referred to as "boil-off gas" or "BOG") generated by evaporation of the low-temperature liquid 3 stored in the storage tank 5, and is connected at one end to the storage tank 5 and at the other end to a circulation line 17. By opening an on-off valve V1 provided on the extraction line 7, the evaporated gas extracted from the storage tank 5 is introduced into the circulation line 17.

[0018] <Adsorption container> The adsorption vessel 9 contains an adsorbent for adsorbing the evaporated gas extracted from the extraction line 7 . The adsorption capacity of the adsorbent (such as activated carbon) contained in the adsorption vessel 9 increases at lower temperatures, so by keeping the adsorbent at a low temperature, the adsorption capacity of the adsorbent increases, making it possible to adsorb a large amount of evaporated gas. In addition, by providing a heat source to the adsorbent holding a large amount of evaporated gas to raise the temperature, the adsorption capacity of the adsorbent decreases, making it possible to release (desorb) the adsorbed evaporated gas. Hereinafter, the desorbed adsorbed evaporated gas is referred to as desorbed gas. In addition, since the evaporative gas processing system 1 of this embodiment includes two adsorption vessels 9, the adsorption vessels 9 will be referred to as adsorption vessel A and adsorption vessel B for the sake of identification hereinafter.

[0019] <Low temperature liquid delivery line> The low-temperature liquid delivery line 13 is a line that vaporizes the low-temperature liquid 3 delivered from the storage tank 5 and delivers it to the gas trunk line, and is equipped with a delivery pump 11, a gas-liquid mixer 19, a boost pump 21, a heat exchanger 15, a vaporizer 23, and a pressure regulating valve 25, all of which are provided in the storage tank 5. The cryogenic liquid 3 discharged from the storage tank 5 by the delivery pump 11 is introduced into the boost pump 21 via the gas-liquid mixer 19, and after being pressurized by the boost pump 21, is introduced into the vaporizer 23 via the heat exchanger 15, is heated and vaporized by the vaporizer 23, and is then sent to the gas trunk line via the pressure regulating valve 25. An example of the heat source for the vaporizer 23 is seawater.

[0020] The gas-liquid mixer 19 provided between the delivery pump 11 and the boost pump 21 mixes the gas desorbed from the adsorption vessel 9 with the cryogenic liquid 3 and condenses it. A second desorbed gas supply line 31b for introducing the desorbed gas into the gas-liquid mixer 19 is connected to the gas-liquid mixer 19. The second desorbed gas supply line 31b will be described later. The cryogenic liquid 3 discharged from the storage tank 5 is mixed with the desorbed gas supplied from the second desorbed gas supply line 31b by the gas-liquid mixer 19, and the desorbed gas is condensed, and then the mixture is introduced into the boost pump 21.

[0021] The heat exchanger 15 provided between the boost pump 21 and the vaporizer 23 performs heat exchange using the cold heat of the low-temperature liquid 3, and a circulation line 17 is connected to the heat exchanger 15. The cryogenic liquid 3, whose pressure has been boosted by the boost pump 21 and whose degree of supercooling has been increased, is introduced into the heat exchanger 15, and the evaporated gas flowing through the circulation line 17 is cooled by the cold energy of the cryogenic liquid 3.

[0022] The pressure regulating valve 25 provided downstream of the vaporizer 23 adjusts the pressure of the gas downstream of the vaporizer 23 in the cryogenic liquid delivery line 13 (hereinafter referred to as "vaporized gas"). As will be described in more detail later, this embodiment uses the vaporized gas downstream of the vaporizer 23 in the cryogenic liquid delivery line 13, and introduces evaporated gas (desorbed gas) pressurized to a pressure approximately the same as that of the vaporized gas into the cryogenic liquid 3 and vaporized gas in the cryogenic liquid delivery line 13. Although the desorbed gas is pressurized to the same level as the vaporized gas, the pressure of the desorbed gas decreases due to pressure loss in the adsorption vessel 9 and piping, and becomes lower than the pressure of the vaporized gas in the low-temperature liquid delivery line 13, so that the desorbed gas may not be introduced into the vaporized gas. For this reason, the vaporized gas is depressurized by the pressure regulating valve 25 so that the desorbed gas can be introduced into the vaporized gas.

[0023] However, since the gas main line has a predetermined required pressure, it is difficult to reduce the pressure below that pressure. Therefore, taking the above pressure loss into consideration, the cryogenic liquid 3 is boosted by the boost pump 21 to a pressure higher than the required pressure of the gas main line, and the required pressure of the gas main line is satisfied even if the pressure is reduced by the pressure regulating valve 25. Moreover, the pressure of the desorption gas may be increased by providing a pressure increasing device in the desorption gas supply line 31. In this case, the pressure regulating valve 25 may be omitted.

[0024] <Circulation Line> The circulation line 17 circulates the evaporated gas introduced from the withdrawal line 7 between either the adsorption vessel A or the adsorption vessel B and the heat exchanger 15 . The circulation line 17 branches out and is connected to adsorption vessels A and B, respectively. The circulation line 17 connected to adsorption vessel A is equipped with on-off valves V2 and V3, and the circulation line 17 connected to adsorption vessel B is equipped with on-off valves V4 and V5.

[0025] When circulating the evaporated gas between the adsorption vessel A and the heat exchanger 15, the on-off valves V2 and V3 are opened and the on-off valves V4 and V5 are closed. Similarly, when circulating the evaporated gas between the adsorption vessel B and the heat exchanger 15, the on-off valves V4 and V5 are opened and the on-off valves V2 and V3 are closed.

[0026] The evaporated gas extracted from the extraction line 7 is introduced upstream of a circulation blower 27 provided in the circulation line 17, and is supplied to the heat exchanger 15 by the circulation blower 27. The evaporated gas is cooled in the heat exchanger 15 by the cold energy of the cryogenic liquid 3 flowing in the cryogenic liquid delivery line 13, and is introduced into one of the adsorption vessels 9 (adsorption vessel A or adsorption vessel B).

[0027] The evaporated gas introduced into the adsorption vessel 9 is adsorbed by the adsorbent contained in the adsorption vessel 9. Since the evaporated gas is cooled by the heat exchanger 15 before being introduced into the adsorption vessel 9, the adsorbent is cooled by the cold heat of the evaporated gas, and the adsorption of the evaporated gas is promoted.

[0028] When the adsorbent adsorbs evaporated gas, heat of adsorption is generated. Heat of adsorption is the kinetic energy of the gas that is expressed as heat when the gas molecules flying around in space are fixed on the surface of the adsorbent. As adsorption progresses, the temperature inside the container rises due to this heat of adsorption, and the amount of adsorption decreases.

[0029] When the adsorption amount decreases to a certain extent, it becomes impossible to adsorb the entire amount of the evaporated gas introduced into the adsorption vessel 9, and so the unadsorbed evaporated gas is discharged again to the circulation line 17. The evaporated gas discharged from the adsorption vessel 9 to the circulation line 17 is mixed with the evaporated gas introduced from the extraction line 7, and is re-cooled in the heat exchanger 15 before being returned to the adsorption vessel 9. The cold energy of the re-cooled evaporated gas cools the adsorbent, again promoting the adsorption of the evaporated gas.

[0030] In this way, the presence of the circulation line 17 allows the inside of the adsorption vessel 9 to be continuously cooled, so that a high adsorption amount can be maintained and a large amount of evaporated gas can be adsorbed. In addition, since the evaporated gas is used as a refrigerant to cool the adsorbent using the cold energy of the low-temperature liquid 3, heat is transferred by direct contact with the adsorbent, and the response to temperature changes is good. This makes it possible to shorten the processing time of the adsorption process.

[0031] When the adsorbent adsorbs a predetermined amount of evaporated gas, the adsorption process is stopped and the process proceeds to a desorption process. As described above, the evaporated gas adsorbed by the adsorbent is desorbed by heating the adsorbent. In the evaporated gas processing system 1 of this embodiment, a gas supply line 29 as shown in FIG. 2 is provided as a heat source for heating, and the gas (vaporized gas) obtained by vaporizing the low-temperature liquid 3 is introduced into the adsorption vessel 9.

[0032] <Gas supply line> The gas supply line 29 supplies the gas obtained by vaporizing the cryogenic liquid 3 to one of the adsorption vessels 9, with one end being downstream of the vaporizer 23 in the cryogenic liquid delivery line 13 and the other end being branched and connected to the adsorption vessels A and B. An on-off valve V6 is provided on the cryogenic liquid delivery line 13 side of the gas supply line 29, and an on-off valve V7 is provided on the adsorption vessel A side of the branched portion, and an on-off valve V8 is provided on the adsorption vessel B side.

[0033] When vaporized gas is introduced into the adsorption vessel A, the on-off valves V6 and V7 are opened and the on-off valve V8 is closed. Similarly, when vaporized gas is introduced into the adsorption vessel B, the on-off valves V6 and V8 are opened and the on-off valve V7 is closed.

[0034] The vaporized gas downstream of vaporizer 23 is a high-temperature gas (e.g., 5°C), so when the vaporized gas is introduced from gas supply line 29 into adsorption vessel 9, the temperature inside the vessel rises and the evaporated gas adsorbed by the adsorbent is desorbed. Inside adsorption vessel 9, a large amount of evaporated gas is held by circulating the evaporated gas while cooling it, and when high-temperature vaporized gas is introduced therein, the large amount of adsorbed evaporated gas is desorbed, and a desorbed gas at high pressure can be obtained. In addition, since the vaporized gas, which is the heat source, is directly introduced into the adsorption vessel 9, heat is transferred by direct contact with the adsorbent, so that the response to temperature changes is good and the processing time of the desorption step can be kept short.

[0035] In order to effectively utilize the desorbed gas obtained by heating the adsorbent, the evaporative gas treatment system 1 of this embodiment is provided with a desorbed gas supply line 31 to introduce the desorbed gas into the low-temperature liquid delivery line 13.

[0036] <Desorption gas supply line> The desorption gas supply line 31 introduces the desorption gas discharged from the adsorption vessel 9 into the cryogenic liquid delivery line 13, and one end of the line branches off to be connected to the adsorption vessels A and B. The other end of the line also branches off, with one end connected to the downstream side of the vaporizer 23 in the cryogenic liquid delivery line 13 and the other connected to the gas-liquid mixer 19. The portion connected to the downstream side of the vaporizer 23 is referred to as a first desorption gas supply line 31a, and the portion connected to the gas-liquid mixer 19 is referred to as a second desorption gas supply line 31b. An on-off valve V9 is provided in the desorption gas supply line 31 at a portion connected to the adsorption vessel A, and an on-off valve V10 is provided in a portion connected to the adsorption vessel B. In addition, an on-off valve V11 is provided in the first desorption gas supply line 31a, and an on-off valve V12 is provided in the second desorption gas supply line 31b.

[0037] For example, when the desorbed gas of the adsorption vessel A is introduced into the vaporized gas downstream of the vaporizer 23 in the cryogenic liquid delivery line 13, the on-off valves V9 and V11 are opened and the on-off valves V10 and V12 are closed. When the desorbed gas of the adsorption vessel A is introduced into the gas-liquid mixer 19 in the cryogenic liquid delivery line 13, the on-off valves V9 and V12 are opened and the on-off valves V10 and V11 are closed. In this way, by switching the open / close state of the on-off valves V11 and V12, it is possible to switch whether the desorbed gas discharged from the adsorption vessel A is introduced into the gaseous cryogenic liquefied gas 3 (vaporized gas) downstream of the vaporizer 23 or into the liquid cryogenic liquefied gas 3 upstream of the vaporizer 23. By operating the on-off valve V10 instead of the on-off valve V9, the desorbed gas of the adsorption vessel B can be introduced into the cryogenic liquid delivery line 13 in the same manner as described above.

[0038] Whether the desorption gas is introduced downstream or upstream of the vaporizer 23 is selected depending on the pressure of the desorption gas. When the vaporization gas is introduced into the adsorption vessel 9 to desorb the evaporated gas as in this embodiment, the desorption gas is pressurized to approximately the same pressure as the vaporization gas, so the desorption gas is first introduced into the vaporization gas downstream of the vaporizer 23 via the first desorption gas supply line 31a.

[0039] As described above, the pressure of the desorbed gas decreases as the amount of evaporated gas adsorbed in the adsorption vessel 9 decreases, so when the pressure of the desorbed gas becomes lower than that of the vaporized gas, introduction of the desorbed gas into the vaporized gas is stopped and the desorbed gas is introduced into the gas-liquid mixer 19. At this time, the desorbed gas is at a higher pressure than the cryogenic liquid 3 flowing through the gas-liquid mixer 19, so the desorbed gas can be mixed into the cryogenic liquid 3 without the need for a pressure booster or the like.

[0040] The evaporative gas processing method of this embodiment, which is carried out using the evaporative gas processing system 1 configured as above, will be described with reference to FIG. As shown in FIG. 1, the evaporative gas processing method according to this embodiment performs the following steps in each of two adsorption vessels 9: an adsorption process in which the evaporative gas flowing through the circulation line 17 is adsorbed by an adsorbent; a desorption process in which the evaporative gas adsorbed in the adsorption process is heated to desorb from the adsorbent and the evaporative gas (desorbed gas) pressurized by the desorption is introduced into the low-temperature liquid delivery line 13; and a residual gas process in which, after the desorption process, the residual gas remaining in the adsorption vessel 9 is discharged into the circulation line 17 and the inside of the adsorption vessel 9 is depressurized. By alternately performing the adsorption processes in the two adsorption vessels 9, evaporative gas is continuously extracted from the storage tank 5, and while the adsorption process is being performed in one adsorption vessel 9, the desorption process and residual gas process are performed in the other adsorption vessel 9, so that the residual gas in the other adsorption vessel 9 is introduced via the circulation line 17 into the one adsorption vessel 9 undergoing the adsorption process. The evaporative gas processing method of Fig. 1 will be described below with reference to Fig. 3 to Fig. 7, which show the open and closed states of the on-off valves V1 to V12 of the evaporative gas processing system 1 of Fig. 2 during the process. Note that the on-off valves V1 to V12 in Fig. 3 to Fig. 7 are shown as outlined white when open and as filled in black when closed. Furthermore, only the conduits through which the cryogenic liquid 3 and each gas (vaporized gas, evaporated gas, desorbed gas) flow are shown in bold with the direction of flow indicated. Furthermore, the temperatures and pressures in the following description are merely examples and are not limited to those used in actual operation.

[0041] First, as shown in FIG. 3, the on-off valves V1 to V3 are opened, and the adsorption process is started using the adsorption vessel A (state 1). A low-temperature liquid (e.g., −163° C.) such as LNG in the storage tank 5 is delivered to the low-temperature liquid delivery line 13 by the delivery pump 11 at a pressure of, for example, about 0.5 to 1.5 MPa and introduced into the gas-liquid mixer 19. Since no desorbed gas is supplied to the gas-liquid mixer 19 in the state 1, the low-temperature liquid 3 passes through the gas-liquid mixer 19, is boosted to 4 MPa to 7 MPa by the boost pump 21, and is introduced into the heat exchanger 15. Furthermore, the evaporated gas (-120°C to -150°C, approximately 0.1 MPa) in the storage tank 5 is extracted through the extraction line 7 and introduced into the circulation line 17. The evaporated gas introduced into the circulation line 17 is sent to the heat exchanger 15 by the circulation blower 27, and undergoes heat exchange with the low-temperature liquid 3, where it is cooled to, for example, -160°C. The cryogenic liquid 3 that has exchanged heat with the evaporated gas is vaporized by the vaporizer 23 into gas (vaporized gas) and is sent to the gas trunk line.

[0042] The cooled evaporated gas is introduced into adsorption vessel A and comes into direct contact with the adsorbent contained in adsorption vessel A, where the evaporated gas is adsorbed onto the adsorbent and the adsorbent is cooled. The adsorption capacity improves by cooling, but after a certain amount of adsorption has progressed, the temperature inside adsorption vessel A rises due to the heat of adsorption, and the temperature of the evaporated gas inside the vessel also rises, reducing the cooling efficiency and gradually slowing down the improvement in adsorption capacity. The evaporated gas that has not been completely adsorbed by the adsorbent is sent back to the circulation line 17, where it merges with the evaporated gas introduced from the withdrawal line 7 and is cooled again in the heat exchanger 15. The cooled evaporated gas is introduced into the adsorption vessel A, where it cools the adsorbent and promotes adsorption again.

[0043] As described above, the adsorption amount in adsorption vessel A increases by continuing to cool the adsorbent while removing the generated heat of adsorption by heat exchanger 15. The adsorption process in adsorption vessel A is continued until the adsorption amount in adsorption vessel A reaches a specified amount. The adsorption amount can be calculated from the amount of change from the initial state of the pressure and temperature in adsorption vessel A, or the difference in the integrated flow meter values ​​installed on the inlet and outlet sides of adsorption vessel A.

[0044] When the adsorption amount in adsorption vessel A reaches a specified amount, as shown in Fig. 4, on-off valves V2 and V3 are closed to terminate the adsorption process in adsorption vessel A, and on-off valves V4 and V5 are opened to start the adsorption process in adsorption vessel B (as is the same as for adsorption vessel A, so the explanation is omitted). In addition, the desorption process of adsorption vessel A, which has completed the adsorption process, is started (state 2). In Fig. 4, on-off valves V6, V7, V9, V11, and V12 used in the desorption process of adsorption vessel A are all shown in the open state (white), but the operation of each on-off valve in the desorption process is performed as follows.

[0045] First, the on-off valves V6 and V7 are opened, and the vaporized gas (5°C, 4 MPa to 7 MPa) is introduced into the adsorption vessel A through the gas supply line 29. By introducing the vaporized gas, the adsorbent that has adsorbed the evaporated gas comes into direct contact with the high-temperature vaporized gas, heating the adsorbent. The evaporated gas adsorbed by the adsorbent is desorbed by heating, and the pressure of the desorbed gas in the vessel is increased by allowing the desorption to proceed within the vessel. The pressure of the desorbed gas can be adjusted to any value as necessary, but can be increased to, for example, about 7 MPa (same as the vaporized gas to be introduced).

[0046] When the pressure of the desorbed gas in the adsorption vessel A rises to a predetermined pressure (for example, equal to or higher than the required pressure of the gas trunk line), the on-off valves V9 and V11 are opened to introduce the desorbed gas into the cryogenic liquid delivery line 13 downstream of the vaporizer 23. The desorbed gas is pressurized inside the adsorption vessel A, but due to pressure losses in the adsorption vessel A and piping, the pressure becomes lower than the pressure (4 MPa to 7 MPa) of the vaporized gas flowing through the cryogenic liquid delivery line 13. Therefore, the vaporized gas is depressurized to within the required pressure range of the gas trunk line by the pressure regulating valve 25 provided in the cryogenic liquid delivery line 13 before the desorbed gas is introduced into the cryogenic liquid delivery line 13.

[0047] As the amount of desorbed gas desorbed from the adsorbent (desorption amount) increases, the amount of gas in the adsorption vessel A decreases, so that the pressure of the desorbed gas flowing through the desorption gas supply line 31 gradually decreases. When the desorption amount reaches a specified amount (for example, a value at which it is determined that the pressure of the desorbed gas is equal to or lower than the required pressure of the gas trunk line), the on-off valve V11 is closed and the on-off valve V12 is opened to introduce the desorbed gas into the gas-liquid mixer 19 provided upstream of the boost pump 21. Although the pressure of the desorbed gas at this time is lower than the required pressure of the gas trunk line, it is higher than the pressure (0.5 to 1.5 MPa) of the low-temperature liquid 3 flowing through the gas-liquid mixer 19, so that the gas and liquid can be mixed into the low-temperature liquid 3 without the need for a compressor or the like.

[0048] Although the above is an example in which the desorption process is started immediately after the adsorption process is completed, the desorption process may be performed at any timing depending on the demand situation of the gas main line, etc.

[0049] When the desorption amount in the adsorption vessel A reaches a specified amount (for example, a value at which it is determined that the pressure of the desorbed gas will be equal to or lower than the pressure of the low-temperature liquid 3 flowing through the gas-liquid mixer 19), as shown in FIG. 5, the on-off valves V6, V7, V9, and V12 are closed to terminate the desorption process, and the on-off valve V3 is opened to start processing the remaining gas (state 3).

[0050] When the desorption process is completed, desorbed gas at a pressure of about 0.5 to 1.5 MPa remains in the adsorption vessel A. By opening the on-off valve V3, the remaining gas is discharged from the high-pressure (0.5 to 1.5 MPa) adsorption vessel A to the low-pressure (approximately 0.1 MPa) circulation line, and the pressure inside the adsorption vessel A is reduced. At this time, since adsorption vessel B is performing adsorption processing via circulation line 17, the residual gas in adsorption vessel A discharged into circulation line 17 is transferred to adsorption vessel B together with the evaporated gas circulating through circulation line 17, and is adsorbed by the adsorbent in adsorption vessel B.

[0051] When the pressure inside adsorption vessel A drops to approximately the same level as the pressure in the circulation line, on-off valve V3 is closed to terminate the treatment of the remaining gas. Thereafter, when the adsorption amount in adsorption vessel B reaches a specified amount, on-off valves V4 and V5 are closed to terminate the adsorption treatment in adsorption vessel B, and on-off valves V2 and V3 are opened to start the adsorption treatment in adsorption vessel A, as shown in Fig. 6. In addition, the desorption treatment of adsorption vessel B, which has completed the adsorption treatment, is started (state 4). The desorption treatment of adsorption vessel B is performed by operating on-off valves V6, V8, and V10 to V12, but the operations are the same as those for adsorption vessel A, so a description thereof will be omitted.

[0052] 7, when the desorption process in adsorption vessel B is completed, the on-off valve V5 is opened to start the process of the remaining gas (state 5). As in the process of the remaining gas in adsorption vessel A, by opening the on-off valve V5, the remaining gas is discharged from the high-pressure (0.5 to 1.5 MPa) adsorption vessel B to the low-pressure (approximately 0.1 MPa) circulation line, and the pressure inside adsorption vessel B is reduced. At this time, since adsorption vessel A is performing adsorption processing via circulation line 17, the residual gas in adsorption vessel B discharged into circulation line 17 is transferred to adsorption vessel A together with the evaporated gas circulating through circulation line 17, and is adsorbed by the adsorbent in adsorption vessel A.

[0053] Thereafter, by repeating states 2 to 5, the adsorption process is alternately performed in the two adsorption vessels 9, and the evaporated gas can be continuously extracted from the storage tank 5. In addition, while adsorption treatment is being performed in one adsorption vessel 9, desorption treatment and residual gas treatment are performed in the other adsorption vessel 9, so that the residual gas in the other adsorption vessel 9 can be introduced via a circulation line into one of the adsorption vessels 9 undergoing adsorption treatment.

[0054] As described above, in the present embodiment, since no new evaporative gas is generated during residual gas processing as in the conventional example, the residual gas can be processed without reducing the efficiency of evaporative gas processing, and the evaporative gas can be processed efficiently.

[0055] [Embodiment 2] The above-described embodiment 1 is a method for treating evaporative gas using the evaporative gas treatment system 1 of Figure 2, and as a method for treating the residual gas in the adsorption vessel 9, the residual gas in the other adsorption vessel 9 is introduced via a circulation line into one of the adsorption vessels 9 undergoing adsorption treatment. In order to continuously treat evaporative gas using the evaporative gas treatment system 1 in Fig. 2, it is necessary to complete the desorption process and residual gas process in one adsorption vessel 9 while the other adsorption vessel 9 is performing the adsorption process, but continuous treatment of evaporative gas may be difficult depending on the start timing of the desorption process and the time required for each process. This point will be explained below with reference to Fig. 8.

[0056] FIG. 8(a) shows an example in which the desorption process is not performed immediately after the adsorption process is completed in the adsorption vessel A. As described above, the desorption process is started at any timing depending on the demand of the gas main line, etc. Therefore, as shown in Fig. 8(a), after the adsorption process of the adsorption vessel A is completed, the desorption process may start after a waiting time. The time required for the adsorption process, desorption process, and residual gas processing in the example shown in Figure 8(a) is the same as that in the example shown in Figure 1. However, because the start of the desorption process is delayed, the adsorption process in adsorption vessel B is completed before the processing of the residual gas in adsorption vessel A is completed. When the adsorption treatment in adsorption vessel B is completed, the residual gas in adsorption vessel A cannot be transferred to adsorption vessel B via circulation line 17, and the pressure inside adsorption vessel A cannot be sufficiently reduced.

[0057] As described above, in order to perform the adsorption process, the pressure inside the adsorption vessel must be sufficiently reduced. Therefore, in the example shown in Fig. 8(a), the adsorption vessel A cannot perform the adsorption process, and therefore the evaporated gas cannot be continuously treated.

[0058] Even if the desorption process is carried out immediately after the adsorption process is completed, the same problem as described above may occur depending on the time required for each process. FIG. 8(b) shows an example in which the time required for the adsorption process is less than (the time required for the desorption process+the time required for the remaining gas process). In the example of Figure 8(b), as in the example of Figure 8(a), the adsorption process in adsorption vessel B is completed before the residual gas process in adsorption vessel A is completed, so the pressure inside adsorption vessel A cannot be sufficiently reduced.

[0059] In this embodiment, an evaporative gas processing system and an evaporative gas processing method capable of processing evaporative gas regardless of the start timing of the desorption process and the required time of each process will be described. First, an evaporative gas processing system 33 of this embodiment is shown in FIG. 9, and its features will be described below.

[0060] The evaporative gas treatment system 1 in Fig. 2 is provided with two adsorption vessels 9, but the evaporative gas treatment system 33 shown in Fig. 9 is provided with three adsorption vessels 9. The newly added adsorption vessel 9 in this embodiment is referred to as adsorption vessel C.

[0061] In addition, on-off valves V13 and V14 are provided at the portion of the circulation line 17 branching off to the adsorption vessel C side, and on-off valves V15 and V16 are provided at the portions of the gas supply line 29 and the desorption gas supply line 31 branching off to the adsorption vessel C side, respectively. The other parts are similar to those of the evaporative gas processing system 1 in FIG. 2, so they are denoted by the same reference numerals as those in FIG. 2 and the description thereof will be omitted.

[0062] The evaporative gas processing method of this embodiment, which is carried out using the evaporative gas processing system 33 configured as above, will be described with reference to FIG. As shown in FIG. 10, the evaporative gas processing method according to this embodiment performs the following steps in each of the three adsorption vessels 9: an adsorption process in which the evaporative gas flowing through the circulation line 17 is adsorbed by the adsorbent; a desorption process in which the evaporative gas adsorbed in the adsorption process is heated to desorb from the adsorbent and the evaporative gas (desorbed gas) pressurized by the desorption is introduced into the low-temperature liquid delivery line 13; and a residual gas process in which, after the desorption process, the residual gas remaining in the adsorption vessels 9 is discharged into the circulation line 17 and the inside of the adsorption vessels 9 is depressurized. By sequentially performing the adsorption processes in the three adsorption vessels 9, the evaporative gas is continuously extracted from the storage tank 5, and while the residual gas process is being performed in one adsorption vessel 9, the adsorption process is performed in one of the other two adsorption vessels 9, so that the residual gas in one adsorption vessel 9 is introduced via the circulation line 17 to one of the two adsorption vessels 9 undergoing the adsorption process. The evaporative gas processing method of Fig. 10 will be described below with reference to Figs. 11 to 18 showing the open and closed states of the on-off valves V1 to V16 of the evaporative gas processing system 33 of Fig. 9 during the process. As in Figs. 3 to 7, the on-off valves V1 to V16 in Figs. 11 to 18 are shown in white when open and in black when closed. Furthermore, only the conduits through which the cryogenic liquid 3 and each gas (vaporized gas, evaporated gas, desorbed gas) flow are shown in bold with the direction of flow indicated.

[0063] 11, the on-off valves V1 to V3 are opened and the adsorption process is started using the adsorption vessel A (state 1). The adsorption process is the same as in the first embodiment, so a description thereof will be omitted.

[0064] When the adsorption amount in adsorption vessel A reaches a specified amount, as shown in Fig. 12, on-off valves V2 and V3 are closed to end the adsorption process in adsorption vessel A, and on-off valves V4 and V5 are opened to start the adsorption process in adsorption vessel B. In addition, the desorption process is started for adsorption vessel A, which has finished the adsorption process (state 2). The desorption process is also similar to that in embodiment 1, and therefore will not be described.

[0065] When the desorption amount in the adsorption vessel A reaches a specified amount (for example, a value at which it is determined that the pressure of the desorbed gas will be equal to or lower than the pressure of the low-temperature liquid 3 flowing through the gas-liquid mixer 19), as shown in FIG. 13, the on-off valves V6, V7, V9, and V12 are closed to terminate the desorption process, and the on-off valve V3 is opened to start processing the remaining gas (state 3).

[0066] When the desorption process is completed, desorbed gas at a pressure of about 1 MPa remains in adsorption vessel A. By opening on-off valve V3, the remaining gas is discharged from the high-pressure (1 MPa) adsorption vessel A to the low-pressure (0.1 MPa) circulation line, and the pressure inside adsorption vessel A is reduced. At this time, since adsorption vessel B is performing adsorption processing via circulation line 17, the residual gas in adsorption vessel A discharged into circulation line 17 is transferred to adsorption vessel B together with the evaporated gas circulating through circulation line 17, and is adsorbed by the adsorbent in adsorption vessel B.

[0067] 14, when the adsorption amount in adsorption vessel B reaches a specified amount, the on-off valves V4 and V5 are closed to terminate the adsorption process in adsorption vessel B, and the on-off valves V13 and V14 are opened to start the adsorption process in adsorption vessel C. In addition, the desorption process is started for adsorption vessel B, which has completed the adsorption process (state 4). As a result of adsorption vessel C starting the adsorption process instead of adsorption vessel B, the residual gas in adsorption vessel A that was discharged into the circulation line 17 is transferred to adsorption vessel C together with the evaporated gas circulating through the circulation line 17, and is adsorbed by the adsorbent in adsorption vessel C. When the pressure inside adsorption vessel A drops to about the same level as the pressure in the circulation line, on-off valve V3 is closed to terminate the residual gas treatment.

[0068] In this embodiment, similarly to the example in Fig. 8(b), the time required for adsorption treatment in adsorption vessel B < (time required for desorption treatment in adsorption vessel A + time required for residual gas treatment), but as described above, even if adsorption vessel B completes its adsorption treatment while residual gas treatment is being performed in adsorption vessel A, adsorption vessel C performs adsorption treatment next, so that the residual gas treatment in adsorption vessel A can be completed without problem. Therefore, the problems described in Figs. 8(a) and 8(b) do not occur.

[0069] When the desorption amount in the adsorption vessel B reaches a specified amount (for example, a value at which it is determined that the pressure of the desorbed gas is equal to or lower than the pressure of the low-temperature liquid 3 flowing through the gas-liquid mixer 19), the desorption process is terminated as shown in FIG. 15, and the on-off valve V5 is opened to start processing the remaining gas (state 5). At this time, since adsorption vessel C is performing adsorption processing, the residual gas in adsorption vessel B discharged into circulation line 17 is transported to adsorption vessel C together with the evaporated gas circulating through circulation line 17, and is adsorbed by the adsorbent in adsorption vessel C.

[0070] 16, when the adsorption amount in adsorption vessel C reaches a specified amount, on-off valves V13 and V14 are closed to terminate the adsorption process in adsorption vessel C, and on-off valves V2 and V3 are opened to start the adsorption process in adsorption vessel A. In addition, the desorption process is started for adsorption vessel C that has completed the adsorption process (state 6). As a result of adsorption vessel A starting the adsorption process instead of adsorption vessel C, the residual gas in adsorption vessel B that has been discharged into the circulation line 17 is transferred to adsorption vessel A together with the evaporated gas circulating through the circulation line 17, and is adsorbed by the adsorbent in adsorption vessel A. When the pressure inside adsorption vessel B drops to about the same level as the pressure in the circulation line, on-off valve V5 is closed to terminate the treatment of the residual gas.

[0071] When the desorption amount in the adsorption vessel C reaches a specified amount (for example, a value at which the pressure of the desorbed gas is judged to be equal to or lower than the pressure of the low-temperature liquid 3 flowing through the gas-liquid mixer 19), the desorption process is terminated and the on-off valve V14 is opened to start processing the remaining gas. The residual gas in adsorption vessel C is treated in the same manner as in adsorption vessels A and B, and as shown in Figures 17 and 18, the residual gas in adsorption vessel C is introduced into adsorption vessels A and B via circulation line 17 (state 7, state 8).

[0072] Thereafter, by repeating states 3 to 8, the adsorption process is alternately performed in the three adsorption vessels 9, so that the evaporated gas can be continuously extracted from the storage tank 5. In addition, while residual gas treatment is being performed in one of the adsorption vessels 9, adsorption treatment is being performed in one of the other two adsorption vessels 9, so that the residual gas in one of the adsorption vessels 9 can be introduced without any problems into one of the other two adsorption vessels 9 undergoing adsorption treatment.

[0073] Although the above describes the use of an evaporative gas treatment system 33 having three adsorption vessels 9, the present invention is not limited to this and may also use an evaporative gas treatment system having four or more adsorption vessels 9. By increasing the number of adsorption vessels 9, residual gas treatment can be performed without problems even when the adsorption treatment time of each adsorption vessel 9 is even shorter.

[0074] In addition, although the evaporative gas treatment systems 1 and 33 circulate the evaporative gas between one adsorption vessel and a heat exchanger during adsorption treatment, the present invention is not limited to this, and the evaporative gas may be circulated between two or more adsorption vessels and a heat exchanger. This will be described below using as an example a case in which the adsorption vessel A in Fig. 9 is composed of two adsorption vessels A1 and A2, the adsorption vessel B is composed of two adsorption vessels B1 and B2, and the adsorption vessel C is composed of two adsorption vessels C1 and C2, i.e., a case in which the evaporative gas treatment system 33 has a total of six adsorption vessels A1, A2, B1, B2, C1, and C2. In the above example, in state 1 shown in Fig. 11, the two adsorption vessels A1 and A2 perform adsorption treatment simultaneously, so that the evaporated gas flowing through the circulation line 17 circulates between the two adsorption vessels A1, A2 and the heat exchanger 15. Similarly, in state 2 shown in Fig. 12, while the two adsorption vessels A1 and A2 perform desorption treatment, the evaporated gas circulates through the circulation line 17 between the two adsorption vessels B1, B2 and the heat exchanger 15. In this way, the present invention also includes cases where two or more adsorption vessels perform adsorption treatment simultaneously.

[0075] In addition, although the first and second embodiments are examples in which vaporized gas is used as a heat source for heating the adsorbent, the adsorption vessel 9 may be heated from the outside using, for example, seawater or a heater, and in that case too, a desorbed gas at high pressure can be obtained. However, as described above, it is preferable to introduce the vaporized gas as a heat source into the adsorption vessel 9, since the vaporized gas can be heated by direct contact with the adsorbent, thereby shortening the processing time of the desorption step.

[0076] Moreover, in the first and second embodiments, the pressurized desorbed gas is introduced into the cryogenic liquid delivery line 13, but the introduction destination of the desorbed gas is not limited to this, and the desorbed gas may be introduced into another system having a higher pressure than the pressure in the storage tank 5. Examples of the high-pressure system other than the cryogenic liquid delivery line 13 include, in a case where multiple evaporative gas treatment systems are installed, a cryogenic liquid delivery line of another evaporative gas treatment system other than the evaporative gas treatment system that discharges the desorbed gas, a gas holder installed in or near a factory, or a liquid supply line to a tank truck that transports liquefied gas outside the factory.

[0077] In addition, in the first and second embodiments, the extraction line 7 is connected upstream of the circulation blower 27 in the circulation line 17 to introduce the evaporated gas. However, for example, the extraction line 7 may be connected to each of the adsorption vessels 9, and the evaporated gas may be introduced directly into the adsorption vessels 9. However, as described above, it is preferable to cool the evaporated gas by passing it through the heat exchanger 15 before it is introduced into the adsorption vessel 9, since this makes it possible to cool the adsorbent more efficiently.

[0078] Furthermore, the opening and closing operations of the on-off valves involved in the adsorption process, desorption process, and residual gas process in the first and second embodiments may be performed by automatic control. When the on-off valves are automatically controlled, the temperature and pressure of the adsorption vessel and the temperatures, pressures, and flow rates of the cryogenic liquid and gas in each line are detected and input to a control and calculation device, the adsorption amount, desorption amount, etc. are calculated based on the input values, and the on-off valves are automatically controlled based on the calculated adsorption amount, desorption amount, and each input value.

[0079] The on-off valve V11 may be a check valve that opens at a pressure equal to or higher than the required pressure of the gas main line. In this case, the on-off valve V11 automatically opens and closes at a set pressure, making it unnecessary to control the opening and closing of the valve. [Explanation of symbols]

[0080] 1 Evaporative gas treatment system (embodiment 1) 3. Cryogenic Liquids 5 storage tank 7 Extraction Line 9 Adsorption container 11 Delivery pump 13 Cryogenic liquid delivery line 15 Heat exchanger 17 Circulation Line 19 Gas-liquid mixer 21 Booster pump 23 Carburetor 25 Pressure Regulating Valve 27 Circulation Blower 29 Gas Supply Line 31 Desorption gas supply line 31a First desorption gas supply line 31b Second desorption gas supply line 33 Evaporative gas processing system (embodiment 2) V1~16 On-off valve

Claims

1. an extraction line for extracting evaporated gas generated from a storage tank in which the cryogenic liquid is stored; Two adsorption vessels each containing an adsorbent for adsorbing the evaporated gas; a pump for pumping the cryogenic liquid from the storage tank; a cryogenic liquid delivery line through which the cryogenic liquid delivered by the delivery pump flows; a heat exchanger provided in the cryogenic liquid delivery line for exchanging heat by utilizing the cold of the cryogenic liquid; an evaporation gas processing method for processing the evaporation gas using an evaporation gas processing system including a circulation line connected to the heat exchanger and the two adsorption vessels, the circulation line introducing the evaporation gas extracted from the extraction line and circulating the evaporation gas between one of the two adsorption vessels and the heat exchanger, In each of the adsorption vessels, an adsorption process in which the evaporated gas flowing through the circulation line is adsorbed by the adsorbent; a desorption process in which the evaporated gas adsorbed in the adsorption process is heated to desorb it from the adsorbent, and the evaporated gas whose pressure has been increased by the desorption is introduced into a system having a higher pressure than the pressure in the storage tank or into the low-temperature liquid delivery line; After the desorption process, a residual gas process is performed in which the residual gas remaining in the adsorption vessel is discharged to the circulation line and the inside of the adsorption vessel is depressurized, The method for treating evaporated gas comprises alternately performing the adsorption process in the two adsorption vessels to continuously extract evaporated gas from the storage tank, and while the adsorption process is being performed in one adsorption vessel, the desorption process and the residual gas process are being performed in the other adsorption vessel, so that the residual gas in the other adsorption vessel is introduced via the circulation line into the one adsorption vessel undergoing the adsorption process.

2. An evaporation gas processing system for processing evaporation gas generated from a storage tank in which a cryogenic liquid is stored, an extraction line for extracting evaporated gas generated from the storage tank; three or more adsorption vessels each containing an adsorbent for adsorbing the evaporated gas; a pump for pumping the cryogenic liquid from the storage tank; a cryogenic liquid delivery line through which the cryogenic liquid delivered by the delivery pump flows; a heat exchanger provided in the cryogenic liquid delivery line and configured to exchange heat by utilizing the cold heat of the cryogenic liquid, the heat exchanger being separate from the adsorption vessel; a circulation line connected to the heat exchanger and the three or more adsorption vessels, for introducing the evaporated gas extracted from the extraction line and circulating the evaporated gas between at least one of the three or more adsorption vessels and the heat exchanger, The evaporative gas treatment system is characterized in that the evaporative gas extracted from the extraction line is introduced into the side of the circulation line that is sent to the heat exchanger, cooled in the heat exchanger, and then introduced into the adsorption vessel to cool the adsorbent and be adsorbed by the adsorbent.

3. 3. An evaporative gas processing method for processing evaporative gas using the evaporative gas processing system according to claim 2, comprising the steps of: In each of the adsorption vessels, an adsorption process in which the evaporated gas flowing through the circulation line is adsorbed by the adsorbent; a desorption process in which the evaporated gas adsorbed in the adsorption process is heated to desorb it from the adsorbent, and the evaporated gas whose pressure has been increased by the desorption is introduced into a system having a higher pressure than the pressure in the storage tank or into the low-temperature liquid delivery line; After the desorption process, a residual gas process is performed in which the residual gas remaining in the adsorption vessel is discharged to the circulation line and the inside of the adsorption vessel is depressurized, An evaporative gas treatment method characterized in that the adsorption process is performed sequentially in the three or more adsorption vessels to continuously extract evaporative gas from the storage tank, and while the residual gas treatment is performed in at least one adsorption vessel, the adsorption process is performed in any of the remaining adsorption vessels, so that the residual gas in one of the adsorption vessels is introduced via the circulation line to any of the two or more adsorption vessels undergoing the adsorption process.

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