CN205137051U - Liquefied natural gas tank - Google Patents

Abstract

The utility model proposes a liquefied natural gas storage tank. The liquefied natural gas storage tank includes: a tank body and one or more BOG recovery devices outside the tank body, and the BOG recovery devices are respectively connected to provide cooling heat exchangers (such as refrigerators, cryogenic medium, etc.) and storage tanks. The heat-insulated sealed cavity is used to further insulate the liquefaction chamber, and the BOG is liquefied into LNG by relying on the cooling capacity provided by the heat exchanger at a lower temperature than BOG, which is collected by the liquid collection tray and returned to the tank through the vacuum return pipe. The structure is compact, the installation is convenient, the cooling efficiency is high, and the BOG zero discharge of the storage tank is realized.

Description

LNG storage tank

technical field

The utility model relates to a liquefied natural gas storage tank, in particular to a BOG recovery device for a liquefied natural gas storage tank.

Background technique

In recent years, with the increasingly serious environmental pollution, clean energy has become more and more popular. However, LNG inevitably absorbs heat in the process of production, storage and transportation, and produces boil-off gas (BOG). The resulting loss is relatively large, not only in To a certain extent, it pollutes the environment, creates potential safety hazards, and causes waste of resources. Therefore, the recycling of BOG is particularly important.

At present, there are two ways to deal with BOG reliquefaction: one is to directly install the condensing device on the top of the storage tank, and directly liquefy the BOG gas in the storage tank, such as the "LNG" with the patent number ZL201320230481.6 (publication number: CN203298560U). BOG liquefaction system in the storage tank", but the device in this patent is not easy to install, the structure is not flexible enough, and it is easy to leak heat. The other is to return BOG to cryogenic storage tanks after reliquefaction. In the latter treatment method, the reliquefaction of BOG mainly uses the liquefaction recovery device. In order to achieve the maximum heat transfer of the liquefaction recovery device and achieve the maximum heat transfer effect, the heat insulation structure is very important. For example, the application number is 201410020565.6 (publication number is CN103759497A) "Installation structure of small skid-mounted liquefied natural gas evaporated gas reliquefaction recovery device" shows that it is easy to protect without vacuum insulation, so it is easy to cause heat loss and unsatisfactory refrigeration effect. Another example is the structure shown in the patent No. 201320237880.5 (CN203249465U) "a BOG reliquefaction device", which realizes reliquefaction by pressurizing BOG gas, circulating compression and refrigeration, but the structure is complicated and has low cooling capacity. Based on the problems of the prior art, it is urgent to invent an efficient and convenient BOG recovery device for LNG storage tanks.

Utility model content

The purpose of the utility model is to provide a liquefied natural gas storage tank, on which a BOG recovery device with compact structure, convenient installation and high refrigeration efficiency is arranged.

In order to solve the above technical problems, the utility model adopts the following technical solution: a liquefied natural gas storage tank, including a tank body and at least one BOG recovery device installed outside the tank body, and the BOG recovery devices are respectively connected to heat exchanger and the tank; the BOG recovery device includes an outer shell, the inner space of the outer shell forms a heat-insulated sealed cavity, and a liquefied shell is arranged in the heat-insulated sealed cavity, and the inside of the liquefied shell is A liquefaction chamber; at least one communication pipe is connected between the liquefaction shell and the tank, and the communication pipe communicates the liquefaction chamber with the inner space of the tank; the gas phase medium in the tank passes through the The communication pipe is transported to the liquefaction chamber, and the gas-phase medium is converted into a liquid-phase medium in the liquefaction chamber and then transported to the tank through the communication pipe.

In a preferred solution, the end of the heat exchanger is provided with a condensation pan that is in close contact with the end, and the condensation pan is located at the upper end of the liquefaction shell and is fixedly connected thereto.

In a preferred solution, the end of the heat exchanger protrudes into the heat-insulating sealed chamber so that the condensation pan is located in the heat-insulated sealed chamber.

In a preferred solution, the number of the communication pipe is one, the upper end of the communication pipe is connected to the bottom of the liquefaction shell, and the lower end of the communication pipe extends into the tank.

In a preferred solution, the number of the communication pipes is more than two, including: the gas-phase medium in the tank enters into the liquefaction chamber and the liquid-phase medium condensed in the liquefaction chamber flows back to the return line inside the tank.

In a preferred solution, a liquid collection tray is provided inside the liquefaction housing; the top of the liquid collection tray has an opening, and the opening faces the end of the heat exchanger, and a through hole is provided at the bottom of the liquid collection tray. The return pipe is connected to the bottom through hole of the liquid collecting tray.

In a preferred solution, there is a gap between the side wall of the liquid collecting pan and the liquefaction shell, the upper end of the air inlet pipe extends into the gap, the liquid collecting pan is funnel-shaped, and the The open end of the inlet pipe faces the side wall of the funnel-shaped liquid collecting pan, so as to form an upward flow guide for the gas phase medium through the side wall of the liquid collecting pan.

In a preferred solution, a vacuum tube is provided between the outer casing and the tank body, and the communication pipe passes through the vacuum tube and is connected between the outer casing and the tank body.

In a preferred solution, the outer shell is sealed and connected with the heat exchanger.

In a preferred solution, the heat-insulating sealed chamber is a vacuum chamber or a vacuum-insulated chamber filled with heat-insulating materials.

In a preferred solution, a heat exchange flange is provided on the end of the heat exchanger, and a connection flange is provided on the top of the liquefaction shell; the heat exchange flange and the connection flange are sealed and connected by welding; Wherein, the connecting flange is made of stainless steel, and the heat exchange flange is made of copper or aluminum.

In a preferred solution, a plurality of threaded pipes are also included, and the threaded pipes pass through the liquefaction chamber and are connected to the ends of the heat exchanger.

In a preferred solution, the BOG recovery device is arranged on the outer top of the tank body.

It can be seen from the above-mentioned technical scheme that the advantages and positive effects of this utility model are: the utility model relies on a heat exchanger to provide a cold source, adopts a multi-layer heat-insulated and sealed liquefaction chamber, and a vacuum-insulated inlet pipe and return pipe. The BOG is liquefied into LNG inside, and after being collected by the liquid collection tray, it is returned to the tank through the vacuum return pipe. The overall structure is compact, the installation is convenient, and the refrigeration efficiency is high, realizing zero discharge of BOG in the storage tank.

Description of drawings

Fig. 1 is a schematic structural diagram of a BOG recovery device in Embodiment 1.

Fig. 2 is a schematic diagram of the second structure of the BOG recovery device in the first embodiment.

Fig. 3 is a schematic diagram of the third structure of the BOG recovery device in the first embodiment.

Fig. 4 is a schematic structural view of the BOG recovery device in the second embodiment.

Fig. 5 is another structural schematic diagram of the BOG recovery device in the second embodiment.

Reference signs are explained as follows: 3. heat exchanger; 4. first connecting flange; 5. bolt; 6. threaded pipe; 21. outer shell; cavity; 25, liquid collection tray; 26, intake pipe; 27, return pipe; 28, vacuum pipe; 29, connecting pipe; 211, metal head; 31, heat exchanger end; 32, heat exchange flange; 33, Second connecting flange.

detailed description

Typical implementations embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the utility model can have various changes in different embodiments, all of which do not depart from the scope of the utility model, and the description and illustrations therein are used as illustrations in nature, not for To limit the utility model.

The structure, function and principle of the liquefied natural gas storage tank of the present invention will be described in detail below in conjunction with a preferred embodiment.

Embodiment one

Referring to Fig. 1 and Fig. 2, the liquefied natural gas storage tank of this embodiment includes: a tank body (not shown in the figure) and one or more BOG recovery devices arranged on the top of the outside of the tank body, and the BOG recovery devices are respectively connected to provide cooling capacity The heat exchanger 3 and the tank body; wherein, the heat exchanger 3 includes a heat exchanger end 31, which is the cold finger of the heat exchanger and has a heat exchange contact surface.

Further, the BOG recovery device can also be arranged at other positions except the top outside of the tank body, which is not limited here.

In actual use, the heat exchanger 3 may be a refrigerator, a low-temperature medium or other equipment that can be connected to an external cold source to reduce its own temperature, which is not limited here.

The BOG recovery device includes an outer casing 21 and a liquefaction casing 23 , the inner space of the outer casing 21 constitutes a heat-insulating sealed chamber 22 , the liquefaction casing 23 is arranged in the heat-insulated sealed chamber 22 , and the inside of the liquefaction casing 23 is a liquefaction chamber 24 . A communication pipeline is connected between the liquefaction shell 23 and the tank body, and the communication pipeline connects the liquefaction chamber 24 with the inner space of the tank body; After being converted into a liquid medium, it is transported into the tank through a communication pipeline.

In this embodiment, the communication pipeline includes an air inlet pipe 26 and a return pipe 27, the air inlet pipe 26 is used for the gas phase medium in the tank to be transported to the liquefaction chamber 24 through the air inlet pipe 26, and the return pipe 27 is used for the gas phase medium in the liquefaction chamber 24 After being converted into a liquid phase medium, it is transported into the tank through the return pipe 27.

Further, two vacuum tubes 28 are also arranged between the outer shell 21 and the tank body, and the air inlet pipe 26 and the return pipe 27 pass through the two vacuum tubes 28 respectively and are connected between the outer shell 21 and the tank body, thereby reducing heat transfer and improving the efficiency of the medium. Insulation effect in the intake duct 26 and return duct 27 .

In actual use, the number of the intake pipe 26 and the return pipe 27 may be more than one, which is not limited here.

In order to cooperate with heat exchangers 3 of different structures, the outer shell 21 may include two structures: the first is a cylindrical structure with an open top, and the second is a structure with a cap on the upper end. Two perforations are defined on the bottom of the outer casing 21 for the intake pipe 26 and the return pipe 27 to pass through.

As shown in Figures 1 and 2, when the outer casing 21 is of the first structure, the upper part of the outer casing 21 and the heat exchanger 3 are sealed and connected through the first connecting flange 4, and then fastened by bolts 5 to make the outer casing 21 and the heat exchanger 3 are strengthened and fastened; the opening position of the outer casing 21 is hermetically connected with the first connecting flange 4 to form a heat-insulating sealed cavity 22 . Of course, in addition to connecting the upper part of the outer casing 21 and the heat exchanger 3 in a flanged manner, the sealing connection may also be performed in a welded manner.

As shown in Figure 3, when the outer shell 21 is of the second structure, the upper opening position of the outer shell 21 can be sealed by a metal seal 211, and the heat exchanger end 31 extends through the through hole on the metal seal 211. Into the outer casing 21 and the liquefaction casing 23.

The heat-insulation sealing cavity 22 is a vacuum cavity, and the outer casing 21 and the heat-insulation sealing cavity 22 form multiple heat insulations, which improves the heat insulation effect.

In other embodiments, the heat-insulating sealed cavity 22 may also be a heat-insulated cavity filled with heat-insulating material, which is not limited here.

The upper end of the liquefaction shell 23 has an opening, and the heat exchanger end 31 is connected to the opening position of the upper end of the liquefaction shell 23. The specific connection method is: the heat exchanger end 31 is provided with a heat exchange flange 32, The top opening of 23 is provided with a second connecting flange 33; the heat exchange flange 32 and the second connecting flange 33 are connected by welding and sealing. Preferably, according to the material of the flange, a brazing sealing connection can also be used to ensure the Strength and sealing effect, also reduces connection thickness and weight. In addition, the heat exchanger end 31 is connected downwards with a plurality of threaded pipes 6 , and each threaded pipe 6 runs through the liquefaction shell 23 and the heat exchange flange 32 . On the other hand, the threaded pipe 6 is also used to pass through the liquefaction chamber 24 to transfer the cold source of the heat exchanger end 31 to the liquefaction chamber 24, increasing the heat exchange area of the liquefaction chamber 24, and greatly enhancing the heat transfer Effect.

Further, the heat exchange flange 32 and the second connecting flange 33 can also be an integral structure (see Figure 5), the structure is simpler, and the sealing effect is increased; the second connecting flange 33 can be made of stainless steel, and the connecting flange 33 can be made of stainless steel. The liquefaction housing 23 can also be made of stainless steel, and the same material makes the two easy to connect, which plays a role in enhancing the sealing effect.

It should be noted that: when there is a better fixed connection between the heat exchange flange 32 and the heat exchanger head 31, the threaded pipe 6 can be omitted, and the structure is simpler; the heat exchange flange 32 can be made of copper , aluminum, gold or silver and other high thermal conductivity materials, these materials can greatly improve the heat transfer efficiency.

A liquid collection tray 25 is arranged inside the liquefaction shell 23, and its top has an opening, and the opening faces the end of the heat exchanger 3, a through hole is arranged at the bottom of the liquid collection tray 25, and a return pipe 27 is connected to the bottom of the liquid collection tray 25 at the through hole. There is a gap between the side wall of the liquid collecting tray 25 and the liquefaction shell 23, and the upper end of the air inlet pipe 26 extends into the gap. The side wall of the liquid collecting tray 25 forms an upward flow guide for the gas phase medium through the side wall of the liquid collecting pan 25.

The upper end of the return pipe 27 is connected to the bottom of the liquid collecting pan 25 and the funnel-shaped structure of the liquid collecting pan 25, which is convenient for collecting the liquid phase medium; In the gap between them, the side wall of the funnel-shaped liquid collection tray 25 is used to better guide the airflow, which greatly improves the condensation efficiency.

In addition, the heat exchanger head 31 is also provided with a condensation pan (not shown in the figure) that is in close contact with the heat exchanger end 31. The condensation pan is located at the upper opening of the liquefaction shell 23 and is fixedly connected to it. The opening of the liquid pan 25 is opposite to the condensation pan, which is convenient for collecting the liquid phase medium condensed by the condensation pan. Preferably, the bottom of the condensing pan is provided with heat exchange fins, which can increase the heat transfer area and improve heat exchange. In this embodiment, the heat exchanger head 31 protrudes into the heat-insulating sealed cavity 22 so that the condensation pan is located in the heat-insulated sealed cavity 22 to improve the heat-insulating effect.

In actual use, if the heat insulation effect allows, the heat exchanger head 31 can also be placed only at the upper opening of the heat insulation sealed cavity 22 , which is not limited here.

In other embodiments, the liquid collecting pan 25 can also be omitted (see FIG. 3 ), and the liquid phase medium in the liquefaction chamber 24 can flow back into the tank by its own weight or pressurized by the air inlet pipe 26 .

The principle of BOG recovery in this embodiment is: the gas phase medium in the tank is transported to the liquefaction chamber 24 through the inlet pipe 26, and the inclined side wall of the funnel-shaped liquid collection plate 25 guides the gas phase medium to the upper part of the liquefaction chamber 24, where it condenses on the condensation plate The gas phase medium is condensed into liquid phase medium on the condensing pan under the action of the action of the gas phase medium, and then it is collected by the liquid collection pan 25 and transported into the tank by the return pipe 27. In this embodiment, the air inlet pipe 26, the return pipe 27 and the liquefaction chamber through which the medium passes all adopt high-efficiency heat insulation measures, which reduce heat conduction, convection, and radiation with the outside world, and reduce heat conduction.

Embodiment two

Referring to Fig. 4 and Fig. 5, the difference between this embodiment and the first embodiment is that the quantity of the communication pipe 29 in the BOG recovery device is one, and the upper end of the communication pipe 29 is connected to the bottom of the liquefaction shell 23, and the communication pipe The lower end of 29 stretches into the tank body. The communication pipe 29 guides both the gas-phase medium from the inside of the tank to the liquefaction chamber 24 and the liquid-phase medium from the liquefaction chamber 24 to the tank.

In actual use, since the number of communication pipes 29 in this embodiment is one, communication pipes with different thicknesses can be used according to the amount of gas phase medium produced by the tank, which is not limited here.

In addition, the liquid collecting tray 25 is omitted in the BOG recovery device, so that the overall weight of the BOG recovery device is lighter and the structure is simpler.

To sum up, the utility model liquefied natural gas storage tank has a compact overall structure, is convenient to install, has good heat insulation effect in the BOG refrigeration process, and greatly improves heat exchange efficiency.

While the present invention has been described with reference to exemplary embodiments, it is understood that the words which have been used are words of description and illustration, rather than limitation. Since the invention can be embodied in various forms without departing from the spirit or essence of the invention, it should be understood that the above-described embodiments are not limited to any of the foregoing details, but should be broadly defined within the spirit and scope of the appended claims. Therefore, all changes and modifications that fall within the scope of the claims or their equivalents should be covered by the appended claims.

Claims (13)

1. A liquefied natural gas storage tank, comprising a tank body and at least one BOG recovery device arranged outside the tank body, characterized in that the BOG recovery device is respectively connected to a heat exchanger capable of providing cold energy and the tank body ; The BOG recovery device includes an outer shell, the inner space of the outer shell forms a heat-insulating sealed cavity, and a liquefaction shell is arranged in the heat-insulated sealed cavity, and the inside of the liquefied shell is a liquefaction cavity; At least one communication pipe is connected between the liquefaction shell and the tank body, and the communication pipe communicates the liquefaction chamber with the inner space of the tank body; the gas phase medium in the tank body passes through the communication pipe transported to the liquefaction chamber, and the gas phase medium is converted into a liquid phase medium in the liquefaction chamber and transported to the tank through the communication pipe. 2. The liquefied natural gas storage tank according to claim 1, characterized in that, the end of the heat exchanger is provided with a condensation pan that is in close contact with the end, and the condensation pan is located at the upper end of the liquefaction shell and fixedly connected to it. 3 . The liquefied natural gas storage tank according to claim 2 , wherein the end of the heat exchanger protrudes into the heat-insulating sealed chamber so that the condensation pan is located in the heat-insulated sealed chamber. 4 . 4. The liquefied natural gas storage tank according to claim 1, wherein the number of the communication pipes is one, the upper end of the communication pipe is connected to the bottom of the liquefaction shell, and the lower end of the communication pipe is into the tank. 5. The liquefied natural gas storage tank according to claim 1, characterized in that, the number of said communication pipes is more than two, including: an air inlet pipe for the gas phase medium in the tank to enter the liquefaction chamber and a supply pipe The liquid phase medium condensed in the liquefaction chamber flows back to the return pipe in the tank. 6. The liquefied natural gas storage tank according to claim 5, wherein a liquid collection pan is arranged inside the liquefaction housing; the top of the liquid collection pan has an opening, and the opening faces the end of the heat exchanger , the bottom of the liquid collection tray is provided with a through hole, and the return pipe is connected to the bottom through hole of the liquid collection tray. 7. The liquefied natural gas storage tank according to claim 6, wherein there is a gap between the side wall of the liquid collecting pan and the liquefaction shell, and the upper end of the air inlet pipe extends into the gap , the liquid collecting pan is funnel-shaped, and the open end of the inlet pipe faces the side wall of the funnel-shaped liquid collecting pan, so as to form an upward flow guide for the gas phase medium through the side wall of the liquid collecting pan. 8. The liquefied natural gas storage tank according to claim 1, wherein a vacuum tube is provided between the outer casing and the tank body, and the communication pipe passes through the vacuum tube and is connected between the outer casing and the tank body between. 9 . The liquefied natural gas storage tank according to claim 1 , wherein the outer casing is in sealing connection with the heat exchanger. 10. The liquefied natural gas storage tank according to claim 1, wherein the heat-insulated sealed chamber is a vacuum chamber or a vacuum-insulated chamber filled with heat-insulating materials. 11. The liquefied natural gas storage tank according to claim 1, wherein a heat exchange flange is provided on the end of the heat exchanger, and a connecting flange is provided on the top of the liquefaction shell; The heat flange and the connecting flange are sealed and connected by welding; wherein, the connecting flange is made of stainless steel, and the heat exchange flange is made of copper or aluminum. 12 . The liquefied natural gas storage tank according to claim 1 , further comprising a plurality of threaded pipes, and the threaded pipes pass through the liquefaction chamber and are connected to ends of the heat exchanger. 13 . 13. The liquefied natural gas storage tank according to claim 1, wherein the BOG recovery device is arranged on the outer top of the tank body.