CN107449220A - The re-liquefied recovery systems of BOG and the re-liquefied recovery process of BOG - Google Patents

Abstract

The present invention relates to LNG Technology field, more particularly to a kind of re-liquefied recovery systems of BOG and the re-liquefied recovery process of BOG.The re-liquefied recovery systems of BOG, including LNG storage tank, BOG pressurizing packs and refrigeration machine.LNG storage tank, for storing LNG liquid.BOG pressurizing packs, it is connected by BOG outgoing lines with LNG storage tank to export BOG, and suitable for being pressurized to BOG.Refrigeration machine, the refrigeration machine input are connected by pipeline with BOG pressurizing packs, and the output end of refrigeration machine is connected by LNG incoming lines with LNG storage tank, and suitable for BOG liquefaction is imported into LNG storage tank to pass through LNG incoming lines after LNG.

Description

BOG reliquefaction recovery system and BOG reliquefaction recovery process

technical field

The invention relates to the technical field of liquefied natural gas, in particular to a BOG reliquefaction recovery system and a BOG reliquefaction recovery process.

Background technique

Liquefied natural gas (LNG) is a high-quality clean energy. Its main component is methane, which has high combustion calorific value and slight environmental pollution. With the increasing call for improving environmental quality, LNG has been paid more and more attention by people, and has been widely used in residential life, automobile fuel, power generation and other various industrial applications. In recent years, the automobile industry is facing severe challenges of world energy issues and environmental protection issues. LNG as an automobile fuel has been valued and promoted by many countries in the world. Compared with gasoline, diesel and compressed natural gas, LNG is environmentally friendly, economical and safe LNG vehicles have become a new development trend in the natural gas vehicle industry.

In order to meet the refueling needs of LNG vehicles, the number of LNG refueling stations is increasing. By the end of 2014, there were about 2,000 LNG refueling stations in operation nationwide, and more LNG refueling stations are under construction and planning. In 2020, about 5,000 LNG refueling stations will be built nationwide.

However, during the process of LNG filling and unloading, due to the loss of cooling capacity due to the huge temperature difference between the ambient temperature and the low-temperature LNG, the LNG is continuously heated and produces boil-off gas (BOG). According to the available data, the BOG of LNG filling stations are usually directly emptied, without recycling, resulting in huge waste and pollution.

Comparative analysis of existing related patent technologies, such as CN105927848A, CN106195617A, CN104132239B and CN103759497B, the recycling methods disclosed in these patents are complicated in process, and all need to add an additional LNG storage container, which undoubtedly increases the total cost of LNG storage tanks in LNG filling stations. The volume is contrary to the standard NB/T 1001-2011 "Technical Specifications for Liquefied Natural Gas (LNG) Vehicle Filling Stations". In addition, most of the cold output of the refrigerator adopts natural convection heat exchange between BOG and heat exchanger, and forms a local low-pressure area through reliquefaction into LNG, thereby forming a "pressure difference" to drive the flow of BOG. The heat exchange efficiency of this method is Low, it is difficult to match the cooling output, and it is easy to cause frost or ice on the heat exchanger. These problems directly lead to low recovery efficiency of BOG and complicated system flow, which limits its application in LNG vehicle filling stations.

Contents of the invention

The first object of the present invention is to provide a BOG reliquefaction recovery system to solve the technical problems of small footprint, simple process and high liquefaction efficiency.

The second object of the present invention is to provide a BOG reliquefaction recovery process to solve the technical problems of simple flow and high liquefaction efficiency.

The BOG reliquefaction recovery system of the present invention is realized like this:

A BOG reliquefaction recovery system, comprising:

LNG storage tank, used to store LNG liquid;

The BOG pressurization component is connected to the LNG storage tank through the BOG export pipeline to export BOG, and is suitable for pressurizing the BOG;

Refrigerator, the input end of the refrigerator is connected to the BOG booster assembly through a pipeline, and the output end of the refrigerator is connected to the LNG storage tank through the LNG import pipeline, and is suitable for liquefying BOG into LNG and then passing through the LNG import pipeline Import LNG storage tanks.

Further, the BOG export pipeline includes a gas intake pipe suitable for horizontally inserting into the LNG storage tank from the side head of the LNG storage tank; and

The LNG introduction pipeline includes a return pipe suitable for obliquely inserting into the LNG storage tank from the side head of the LNG storage tank;

The end of the liquid return pipe located outside the LNG storage tank is higher than the end located inside the LNG storage tank.

Further, the LNG introduction pipeline is arranged obliquely, and the end connected to the refrigerator is higher than the end connected to the LNG storage tank; and

The inclination angle of the pipeline before the liquid return pipe on the LNG introduction pipeline relative to the bottom end surface of the LNG storage tank is larger than the inclination angle of the liquid return pipe relative to the bottom end surface of the LNG storage tank.

Further, the length of the air intake pipe placed in the LNG storage tank is greater than the length of the liquid return pipe placed in the LNG storage tank.

Further, the BOG outlet pipeline is provided with a gas outlet low-temperature cut-off valve; and

The LNG introduction pipeline is provided with a liquid inlet low-temperature cut-off valve.

Further, a low-temperature regulating valve is provided on the pipeline connecting the BOG pressurization component and the refrigerator.

Further, the outlet end of the cold end heat exchanger of the refrigerator is higher than the top end of the LNG storage tank.

Further optionally, the BOG booster assembly includes a low-temperature blower.

Further optionally, the BOG pressurization assembly includes a connected normal temperature fan and a heat exchanger;

The heat exchanger has a first flow channel and a second flow channel; wherein

One end of the first flow channel is connected to the LNG storage tank through the BOG export pipeline, and the other end is connected to the inlet of the normal temperature fan;

One end of the second flow channel is connected to the outlet of the normal temperature fan, and the other end is connected to the input end of the refrigerator through the pipe.

The BOG reliquefaction recovery process of the present invention is realized like this:

A BOG reliquefaction recovery process adopts the BOG reliquefaction recovery system, and includes:

Step S1, pressurizing the low-temperature BOG taken from the LNG storage tank;

Step S2, liquefying the pressurized BOG in a low-temperature state into LNG;

In step S3, the LNG formed after liquefaction is introduced into an LNG storage tank for reuse.

The beneficial effects of the present invention are: the BOG reliquefaction recovery system and the BOG reliquefaction recovery process of the present invention adopt a refrigerator to provide cooling capacity, and the method of liquefaction and recovery of BOG is not limited by external conditions such as regions, the system flow is simple, and the gaseous After BOG treatment, liquid LNG is formed for recycling and reuse, which has high economic benefits. Since the BOG discharged from the LNG storage tank is reused to cool itself and finally returned to the LNG storage tank, the recovery rate of BOG can be improved; a large amount of BOG can be avoided from escaping into the air and polluting the environment.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Fig. 1 is the structural diagram of the BOG reliquefaction recovery system of embodiment 1 of the present invention;

Fig. 2 is a structural diagram of a BOG reliquefaction recovery system in Example 2 of the present invention.

In the figure: LNG storage tank 1, LNG liquid 2, gas intake pipe 3, liquid return pipe 4, low-temperature cut-off valve at gas outlet 5, low-temperature fan 6, low-temperature regulating valve 7, refrigerator 8, low-temperature cut-off valve at liquid inlet 9, replacement Heater 10, normal temperature fan 11, BOG export pipeline 12, LNG import pipeline 13.

detailed description

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments It is some embodiments of the present invention, but not all of them. Based on the implementation manners in the present invention, all other implementation manners obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Accordingly, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the invention. Based on the implementation manners in the present invention, all other implementation manners obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.

Example 1:

As shown in FIG. 1 and FIG. 2 , the present invention provides a BOG reliquefaction recovery system suitable for LNG filling stations, including: LNG storage tank 1 , BOG booster assembly and refrigerator 8 .

The LNG storage tank 1 is used for storing LNG liquid 2 . The LNG cryogenic storage tank of this embodiment is a vacuum insulated cryogenic pressure vessel with a double-layer horizontal structure. The inner vessel forms a vacuum interlayer for storing low-temperature LNG liquid 2 , and the outer vessel is a protective layer. In addition, two gas phase pipes are drawn from the gas phase space on the upper part of the storage tank, one is used as the BOG gas intake pipe 3 and the other is used as the LNG liquid return pipe 4 .

The BOG pressurization component is connected with the LNG storage tank 1 through the BOG export pipeline 12 to export BOG, and is suitable for pressurizing the BOG. The BOG pressurization assembly of this embodiment includes a low-temperature blower 6 .

Refrigerator 8, the input end of the refrigerator 8 is connected to the low-temperature fan 6 of the BOG pressurization assembly through a pipeline, and the output end of the refrigerator 8 is connected to the LNG storage tank 1 through the LNG introduction pipeline 13, and is suitable for liquefying BOG into The LNG is then introduced into the LNG storage tank 1 through the LNG introduction pipeline 13 .

The refrigerator 8 and the BOG fan are arranged close to the LNG storage tank 1, and the minimum distance is greater than 2 meters, which can be set to 2 meters, so as to meet the relevant industry standards and ensure the recovery efficiency of BOG.

Specifically, the BOG export pipeline 12 includes a gas intake pipe 3 suitable for horizontally inserting into the LNG storage tank 1 from the side head of the LNG storage tank 1. In terms of vertical insertion, it is possible to avoid inserting the BOG export pipeline 12 into the liquid phase tissue in the LNG storage tank 1, thereby improving the efficiency of absorbing gaseous BOG from the gas phase tissue. And the LNG introduction pipeline 13 includes a liquid return pipe 4 that is suitable for being obliquely inserted into the LNG storage tank 1 from the side head of the LNG storage tank 1; The end on the inside of tank 1.

Preferably, the LNG introduction pipeline 13 is arranged obliquely, and the end connected to the refrigerator 8 is higher than the end connected to the LNG storage tank 1. The inclined design is used to use gravity to improve the introduction of reliquefied LNG. The smoothness of the LNG storage tank 1 and the use of gravity reduce the use of many pumps in the prior art, and are more energy-saving and environmentally friendly.

Preferably, the inclination angle of the pipeline before the liquid return pipe 4 on the LNG introduction pipeline 13 relative to the bottom end surface of the LNG storage tank 1 is greater than the inclination angle of the liquid return pipe 4 relative to the bottom end surface of the LNG storage tank 1, This design is to ensure that the reliquefied LNG liquid 2 can smoothly flow out from the cold end heat exchanger 10 of the refrigerator 8, and the inclination angle of the liquid return pipe 4 relative to the bottom end surface of the LNG storage tank 1 should not be too large. It is to prevent the liquid return pipe 4 from being placed into the liquid phase tissue of the LNG storage tank 1 if the inclination angle is too large, thereby preventing the LNG in the LNG storage tank 1 from blocking the port of the liquid return pipe 4 and causing resistance in the liquid return process, further It is ensured that the reliquefied LNG liquid 2 can smoothly flow into the LNG storage tank 1 .

Preferably, the length of the gas intake pipe 3 placed in the LNG storage tank 1 is greater than the length of the liquid return pipe 4 placed in the LNG storage tank 1, so that the liquid return pipe 4 is closer to the inner wall of the LNG storage tank 1, so that the liquid can flow along the wall Flow down to reduce evaporation, and the length of the air taking pipe 3 is longer than the liquid return pipe 4, which can avoid affecting the liquid return.

More specifically, the BOG export pipeline 12 is provided with a gas outlet low-temperature cut-off valve 5 ; and the LNG introduction pipeline 13 is provided with a liquid inlet low-temperature stop valve 9 .

The refrigerator 8 in this embodiment adopts, for example but not limited to, any one of a mixed working medium throttling refrigerator, a G-M refrigerator, a pulse tube refrigerator, a Stirling refrigerator or a thermoacoustic refrigerator.

A low-temperature regulating valve 7 is provided on the pipeline connecting the low-temperature fan 6 of the BOG supercharging component and the refrigerator 8 .

The outlet end of the cold-end heat exchanger 10 of the refrigerator 8 is higher than the top of the LNG storage tank 1, specifically, the height difference between the outlet end of the cold-end heat exchanger 10 of the refrigerator 8 and the top of the LNG storage tank 1 The height difference is designed to be at least 0.5 meters to ensure that the reliquefied LNG liquid 2 can flow out of the cold end heat exchanger 10 of the refrigerator 8 and flow into the LNG storage tank 1 smoothly.

The specific implementation of the BOG reliquefaction recovery system of this embodiment is that the BOG gas in the gas phase space in the LNG storage tank 1 is sucked into the low-temperature blower 6 through the gas intake pipe 3 and the low-temperature cut-off valve 5 at the gas outlet, and is pressurized by the low-temperature blower 6 Afterwards, it is discharged into the cold-end heat exchanger 10 of the refrigerator 8 through the low-temperature regulating valve 7, and the BOG is forced to convect heat in the cold-end heat exchanger 10 of the refrigerator 8. The BOG absorbs the cooling capacity provided by the refrigerator 8 and is liquefied into LNG , LNG is introduced along the inclined LNG pipeline 13, under the joint action of gravity and pressure difference, along the outlet of the cold end heat exchanger 10 of the refrigerator 8, the low-temperature cut-off valve 9 of the liquid inlet, and the inclined liquid return pipe 4 back to the LNG storage tank 1.

Example 2:

On the basis of Embodiment 1, the BOG reliquefaction recovery system of this embodiment has roughly the same structure as the BOG reliquefaction recovery system of Embodiment 1. Heater 10. The normal temperature fan 11 controls the flow through frequency conversion.

The heat exchanger 10 has a first flow channel and a second flow channel; wherein one end of the first flow channel is connected to the LNG storage tank 1 through the BOG export pipeline 12, and the other end is connected to the inlet of the normal temperature fan 11; one end of the second flow channel is connected to the The outlet of the normal temperature fan 11 is connected, and the other end is connected with the input end of the refrigerator 8 through a pipeline.

The specific implementation of the BOG reliquefaction recovery system in this embodiment is that the BOG gas in the gas phase space in the LNG storage tank 1 is sucked into the normal temperature blower 11 through the gas intake pipe 3 and the low temperature cut-off valve 5 at the gas outlet, and before the BOG enters the normal temperature blower 11, The temperature in the heat exchanger 10 is restored to normal temperature. After being pressurized by the normal temperature fan 11, the temperature is lowered through the heat exchanger 10 first, and then discharged into the cold end heat exchanger 10 of the refrigerator 8 through the low temperature regulating valve 7. The forced convection heat exchange is carried out in the cold end heat exchanger 10 of the refrigerator 8, and the BOG absorbs the cold energy provided by the refrigerator 8, and then liquefies it into LNG. , flow back into the LNG storage tank 1 along the outlet of the cold end heat exchanger 10 of the refrigerator 8 , the low-temperature cut-off valve 9 of the liquid inlet, and the inclined liquid return pipe 4 .

Example 3:

On the basis of Example 1 or Example 2, this example provides a BOG reliquefaction recovery process, using the BOG reliquefaction recovery system of Example 1 or Example 2, and including:

Step S1, pressurizing the low-temperature BOG taken from the LNG storage tank 1;

Step S2, liquefying the pressurized BOG in a low-temperature state into LNG;

In step S3, the LNG formed after liquefaction is introduced into the LNG storage tank 1 for reuse.

In the BOG reliquefaction recovery process of this embodiment, gaseous BOG is processed to form liquid LNG for recycling and reuse, which has high economic benefits. Since the BOG discharged from the LNG storage tank 1 is reused to cool itself and finally returned to the LNG storage tank 1, the recovery rate of BOG can be improved, a large amount of BOG can be prevented from escaping into the air to pollute the environment, and the "zero discharge of BOG" can be realized. ".

Inspired by the above-mentioned ideal embodiment according to the present invention, through the above-mentioned description content, relevant workers can make various changes and modifications within the scope of not departing from the technical idea of the present invention. The technical scope of the present invention is not limited to the content in the specification, but must be determined according to the scope of the claims.

In the description of the present invention, it should be understood that the terms indicating orientation or positional relationship are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying No device or element must have a particular orientation, be constructed, and operate in a particular orientation, and therefore should not be construed as limiting the invention.

In the present invention, unless otherwise clearly specified and limited, terms such as "installation", "connection", "connection" and "fixation" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection , or integrated; it can be mechanically connected or electrically connected; it can be directly connected or indirectly connected through an intermediary, and it can be the internal communication of two components or the interaction relationship between two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention according to specific situations.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship that is usually placed when the product of the invention is used, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying References to devices or elements must have a particular orientation, be constructed, and operate in a particular orientation and therefore should not be construed as limiting the invention. In addition, the terms "first", "second", "third", etc. are only used for distinguishing descriptions, and should not be construed as indicating or implying relative importance.

In addition, the terms "horizontal", "vertical", "overhanging" and the like do not mean that the components are absolutely horizontal or overhanging, but may be slightly inclined. For example, "horizontal" only means that its direction is more horizontal than "vertical", and it does not mean that the structure must be completely horizontal, but can be slightly inclined.

In the present invention, unless otherwise clearly specified and limited, the first feature above or below the second feature may include that the first and second features are in direct contact, and may also include that the first and second features are not in direct contact but is through additional feature contacts between them. Moreover, the first feature on, above and above the second feature includes the first feature directly above and obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. The first feature being below, below and below the second feature includes the first feature being directly below and obliquely below the second feature, or simply means that the first feature has a lower level than the second feature.

Claims (10)

1. A BOG reliquefaction recovery system is characterized in that, comprising: LNG storage tank, used to store LNG liquid; The BOG pressurization component is connected to the LNG storage tank through the BOG export pipeline to export BOG, and is suitable for pressurizing the BOG; Refrigerator, the input end of the refrigerator is connected to the BOG booster assembly through a pipeline, and the output end of the refrigerator is connected to the LNG storage tank through the LNG import pipeline, and is suitable for liquefying BOG into LNG and then passing through the LNG import pipeline Import LNG storage tanks. 2. The BOG reliquefaction recovery system according to claim 1, wherein the BOG export pipeline includes a gas intake pipe suitable for horizontally inserting into the LNG storage tank from the side head of the LNG storage tank; as well as The LNG introduction pipeline includes a return pipe suitable for obliquely inserting into the LNG storage tank from the side head of the LNG storage tank; The end of the liquid return pipe located outside the LNG storage tank is higher than the end located inside the LNG storage tank. 3. The BOG reliquefaction recovery system according to claim 2, wherein the LNG introduction pipeline is arranged obliquely, and the end connected to the refrigerator is higher than the end connected to the LNG storage tank; as well as The inclination angle of the pipeline before the liquid return pipe on the LNG introduction pipeline relative to the bottom end surface of the LNG storage tank is larger than the inclination angle of the liquid return pipe relative to the bottom end surface of the LNG storage tank. 4. The BOG reliquefaction recovery system according to any one of claims 2 or 3, characterized in that the length of the air intake pipe placed in the LNG storage tank is greater than the length of the liquid return pipe placed in the LNG storage tank. 5. The BOG reliquefaction recovery system according to claim 1, characterized in that, the BOG export pipeline is provided with a gas outlet low-temperature cut-off valve; and The LNG introduction pipeline is provided with a liquid inlet low-temperature cut-off valve. 6. The BOG reliquefaction recovery system according to claim 1, characterized in that a low temperature regulating valve is provided on the pipeline connecting the BOG pressurization component and the refrigerator. 7. The BOG reliquefaction recovery system according to claim 1, wherein the outlet end of the cold end heat exchanger of the refrigerator is higher than the top end of the LNG storage tank. 8. The BOG reliquefaction recovery system according to claim 1, wherein the BOG pressurization component comprises a low-temperature blower. 9. The BOG reliquefaction recovery system according to claim 1, characterized in that, the BOG pressurization assembly includes a connected normal temperature fan and a heat exchanger; The heat exchanger has a first flow channel and a second flow channel; wherein One end of the first flow channel is connected to the LNG storage tank through the BOG export pipeline, and the other end is connected to the inlet of the normal temperature fan; One end of the second flow channel is connected to the outlet of the normal temperature fan, and the other end is connected to the input end of the refrigerator through the pipe. 10. A BOG reliquefaction recovery process, characterized in that the BOG reliquefaction recovery system according to any one of claims 1 to 9 is adopted, and includes: Step S1, pressurizing the low-temperature BOG taken from the LNG storage tank; Step S2, liquefying the pressurized BOG in a low-temperature state into LNG; In step S3, the LNG formed after liquefaction is introduced into an LNG storage tank for reuse.