LNG (Liquefied Natural Gas) station filling system utilizing low-temperature oil-free compressor

Abstract

According to the LNG station filling system utilizing the low-temperature oil-free compressor, the problems that an existing filling system is large in occupied area, high in oil removal difficulty, large in compressor power consumption and the like are solved through the low-temperature oil-free compressor, gas in the storage tank and flash steam generated in the filling process are collected, and the gas in the storage tank and the flash steam generated in the filling process are collected through the low-temperature oil-free compressor. The high-pressure gas enters the low-temperature oil-free compressor to be pressurized after being subjected to heat regeneration through the heat regenerator and then enters the heat regenerator to be cooled, the cooled high-pressure gas is conveyed to different low-temperature storage tanks according to whether the filling unit works or not, when the filling unit works, the cooled high-pressure gas is gathered into the low-temperature storage tank B (2), the high-pressure gas is fed in a pressed mode, and the filling system is promoted to work. When the filling unit does not work, the liquefied gas flows into the low-temperature storage tank A (1), liquefaction is completed after shock cooling, liquid supplement in the storage tank is achieved, the liquefied gas storage and transportation cost can be effectively reduced, the energy utilization rate is increased, the filling efficiency is improved, and the system can be applied to existing liquefied natural gas stations or other liquefied gas filling.

Description

Technical Field

[0001] The utility model belongs to the technical field of low-temperature refrigeration, and specifically relates to an LNG station filling system utilizing a low-temperature oil-free compressor. Background Art

[0002] Liquefied natural gas is recognized as the cleanest fossil energy on earth and an important pillar industry of the national economy. It has a wide range of uses, is capital-intensive and technology-intensive, and has a high degree of industrial relevance. It plays an important role in stabilizing economic growth, improving people's lives, and ensuring national defense security. With the abundance of global liquefied natural gas (LNG) resources, the stability of liquid supply has increased, and the economic benefits of liquid have gradually emerged. In order to adapt to the general trend of automobile energy transformation, while being more environmentally friendly, energy-saving and emission-reducing, China has vigorously promoted natural gas vehicles. The emission pollution of natural gas vehicles is significantly lower than that of gasoline vehicles, and they are very flexible and economical.

[0003] LNG is a boiling liquid stored in large quantities in insulated storage tanks. Any heat transferred to the storage tanks will cause some of the liquid to evaporate into gas. When the existing pressure of LNG drops below its boiling point, part of the liquid evaporates after passing through the valve. This is flash gas (BOG). The existing LNG vacuum insulated storage tanks cannot achieve absolute vacuum insulation at the current technological level, and will slowly exchange heat with the outside, forming BOG gas in the tanks. During the LNG filling process, due to the non-standard filling operation procedures of the LNG station by the gas station staff and long downtime, the amount of BOG increases. If it is discharged directly into the atmosphere, it is neither economical nor conducive to environmental protection, and it will also cause certain safety hazards.

[0004] In order to solve the above problems, compressing BOG and then liquefying it to keep the pressure and temperature inside the storage tank stable is currently the most scientific and economical way to deal with BOG. ​​It is of great significance to add BOG processing links to the LNG filling system.

[0005] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present application, and therefore may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0006] In order to provide a basic understanding of some aspects of the disclosed embodiments, a brief summary is given below. The summary is not an extensive review, nor is it intended to identify key, important components or delineate the scope of protection of these embodiments, but rather serves as a prelude to the detailed description that follows.

[0007] The utility model aims to provide an LNG station filling system using a low-temperature oil-free compressor. The system overcomes the problems of large footprint, high oil removal difficulty, and high compressor power consumption in the existing filling system through the low-temperature oil-free compressor. The system collects the gas in the storage tank and the flash gas generated in the filling process, which is reheated by the regenerator and enters the low-temperature oil-free compressor for pressurization. After pressurization, the gas is further cooled by the regenerator. The cooled gas is transmitted to different low-temperature storage tanks through a three-way valve according to whether the filling unit is working. The liquefaction is completed after sudden cooling, and the compressed delivery of liquefied gas is realized. The system can effectively reduce the storage and transportation costs of liquefied gas, increase energy utilization, and improve filling efficiency.

[0008] In order to achieve the above purpose, the utility model proposes the following technical scheme: the system comprises a cryogenic storage tank A (1), a cryogenic storage tank B (2), a switch (3), a liquid phase flow meter (4), a gas filling machine (5), a gas filling gun (6), a user vehicle (7), a return air gun (8), a gas phase flow meter (9), a heat regenerator (10), a cryogenic oil-free compressor (11), a three-way valve (12), and a one-way valve (13), and is divided into three units: a storage unit, a filling unit, and a cooling and pressurizing unit. The storage unit comprises a cryogenic storage tank A (1) and a cryogenic storage tank B (2). The liquid in the cryogenic storage tank B (2) is connected to the filling unit through a pipe at the lower end of the storage tank, and the gas is connected to the cooling and pressurizing unit through a pipe at the upper end of the storage tank. A switch (3) is installed on the upper end pipes of the cryogenic storage tank A (1) and the cryogenic storage tank B (2) for balancing the gas pressure of the two tanks. The lower end of the cryogenic storage tank A (1) is provided with a transmission pipe for supplying gas to the cryogenic storage tank B. (2) replenishing liquid, with a one-way valve (13) arranged in the middle; the filling unit includes a gas filling machine (5), a gas filling gun (6), a user vehicle (7), and a return gas gun (8); the flash gas generated during the filling process is collected by the return gas gun (8) and then connected to the cooling and pressurizing unit; the cooling and pressurizing unit includes a regenerator (10) and a low-temperature oil-free compressor (11); the regenerator (10) recovers the gas in the collected storage tank and the flash gas generated during the filling process and heats it up; the heated gas enters the low-temperature oil-free compressor (11) for compression, and the temperature and pressure are further increased; the compressed high-pressure gas enters the cooling channel of the regenerator (10) for heat exchange and cooling, and is divided into two paths by a three-way valve (12); when the filling unit is working, it enters the upper end of the low-temperature storage tank B (2), pressurizes the high-pressure gas and promotes the operation of the filling system; when the filling unit is not working, it enters the lower end of the low-temperature storage tank A (1) to complete the liquid replenishment in the storage tank.

[0009] An LNG station filling system using a low-temperature oil-free compressor is characterized in that: the filling system also includes the following steps.

[0010] Step 1: The gas is heated. The gas in the cryogenic storage tank A (1) and the cryogenic storage tank B (2) and the flash gas collected by the gas return gun (8) are heated through the regenerator (10). The gas in the transportation process passes through the one-way valve (13) and the gas flow meter (9).

[0011] Step 2: gas pressure boosting and transportation. The gas heated by the regenerator (10) is pressurized by a low-temperature oil-free compressor (11), and the temperature and pressure are further increased.

[0012] Step three, gas cooling and transportation. The high-pressure gas pressurized by the low-temperature oil-free compressor (11) is cooled through the cooling channel of the regenerator (10). When the filling unit is working, it enters the upper end of the low-temperature storage tank B (2), pressurizes the high-pressure gas and promotes the operation of the filling unit; when the filling unit is not working, it is collected at the lower end of the low-temperature storage tank A (1) to replenish liquid in the storage tank.

[0013] The utility model has the following advantages.

[0014] The utility model discloses an LNG station filling system using a low-temperature oil-free compressor. The flash gas generated during the filling process is mixed with the gas collected in the storage tank and then uniformly enters the regenerator heating flow channel to utilize the gas compressed by the oil-free compressor for heat recovery and heating, thereby reducing energy loss.

[0015] The utility model discloses an LNG station filling system using a low-temperature oil-free compressor. After the gas compressed by the oil-free compressor enters the cooling flow channel of the regenerator, the flash gas generated during the filling process and the mixed gas collected in the storage tank are used for cooling and lowering the temperature. The cold energy is reused to achieve the purpose of energy saving.

[0016] The utility model is an LNG station filling system using a low-temperature oil-free compressor. The high-pressure gas compressed by the low-temperature oil-free compressor is introduced into a low-temperature storage tank B (2) when the filling unit is working. At the same time, the high pressure is used to promote the filling unit to work. When the filling unit is not working, the high pressure is introduced into a low-temperature storage tank A (1). After liquefaction, BOG is recycled and utilized, which reduces energy waste and emission losses during the gas filling process. The system and method can also be applied to the filling process of other liquefied gases.

[0017] The utility model discloses an LNG station filling system using a low-temperature oil-free compressor, in which a one-way valve is added to two low-temperature storage tanks to ensure the correct delivery direction of gas and liquid, and a switch is provided to balance the pressure between the two low-temperature storage tanks, thereby improving the safety in the process of storing liquid and collecting gas.

[0018] The utility model discloses an LNG station filling system using a low-temperature oil-free compressor, in which the compressor used is a low-temperature oil-free compressor, which is supported by gas bearings. In the entire filling system, the system is completely oil-free, has no oil removal problem and no oil return device, and is very clean.

[0019] The utility model discloses an LNG station filling system using a low-temperature oil-free compressor. The working gas temperature of the low-temperature oil-free compressor is much lower than the working gas temperature of the normal temperature compressor. There is no need to heat the low-temperature gas to normal temperature for compression, and the system occupies a small area.

[0020] The utility model discloses an LNG station filling system using a low-temperature oil-free compressor. When the low-temperature oil-free compressor works under low-temperature gas conditions, the power consumption of the compressor is reduced, the efficiency is increased, and it is very energy-saving.

[0021] The above general description and the following description are exemplary and explanatory only and are not intended to limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the implementation methods of the utility model or the technical solutions of the prior art, the drawings required for use in the implementation methods or the prior art descriptions are briefly introduced below; obviously, the drawings in the following description are merely exemplary, and for ordinary technicians in this field, other implementation drawings can be derived based on the provided drawings without creative work.

[0023] Figure 1 This is a schematic diagram of an LNG station filling system using a cryogenic oil-free compressor provided in Example 1 of the utility model.

[0024] Figure numerals: cryogenic storage tank A-1, cryogenic storage tank B-2, switch-3, liquid flow meter-4, gas filling machine-5, gas filling gun-6, user vehicle-7, return air gun-8, gas flow meter-9, regenerator-10, cryogenic oil-free compressor-11, three-way valve-12, check valve-13.

[0025] Figure 2 This is a schematic diagram of a heat regenerator in an LNG station filling system using a low-temperature oil-free compressor provided in Example 1 of the utility model.

[0026] Reference numerals: low-pressure gas inlet 101 , low-pressure gas outlet 102 , high-pressure gas inlet 103 , high-pressure gas outlet 104 . DETAILED DESCRIPTION

[0027] In order to be able to understand the characteristics and technical contents of the embodiments of the present disclosure in more detail, the implementation of the embodiments of the present disclosure is described in detail below in conjunction with the accompanying drawings. The attached drawings are for reference only and are not used to limit the embodiments of the present disclosure. In the following technical description, for the convenience of explanation, a full understanding of the disclosed embodiments is provided through multiple details. However, one or more embodiments can still be implemented without these details. In other cases, in order to simplify the drawings, well-known structures and devices can be simplified for display. Based on the embodiments in the utility model, other embodiments obtained by ordinary technicians in this field without making creative work all belong to the protection scope of the utility model.

[0028] Example 1.

[0029] like Figure 1-2 The LNG station filling system using a cryogenic oil-free compressor is shown, the system comprising a cryogenic storage tank A (1), a cryogenic storage tank B (2), a switch (3), a liquid phase flow meter (4), a gas dispenser (5), a gas filling gun (6), a user vehicle (7), a return air gun (8), a gas phase flow meter (9), a regenerator (10), a cryogenic oil-free compressor (11), a three-way valve (12), and a one-way valve (13), and is divided into a storage unit, a filling unit, and a cooling and pressurizing unit. The storage unit comprises a cryogenic storage tank A (1) and a cryogenic storage tank B (2). The liquid in the cryogenic storage tank B (2) is connected to the filling unit through a pipeline at the lower end of the storage tank, and the gas is connected to the cooling and pressurizing unit through a pipeline at the upper end of the storage tank. A switch (3) is installed on the upper end pipelines of the cryogenic storage tank A (1) and the cryogenic storage tank B (2) for balancing the gas pressure of the two tanks. The lower end of the cryogenic storage tank A (1) is provided with a transmission pipeline for supplying gas to the cryogenic storage tank B (2 ) to replenish liquid, with a one-way valve (13) arranged in the middle; the filling unit includes a gas filling machine (5), a gas filling gun (6), a user vehicle (7), and a return gas gun (8); the flash gas generated during the filling process is collected by the return gas gun (8) and connected to the cooling and pressurizing unit; the cooling and pressurizing unit includes a regenerator (10) and a low-temperature oil-free compressor (11); the regenerator (10) recovers the gas in the collected storage tank and the flash gas generated during the filling process and heats it up; the heated gas enters the low-temperature oil-free compressor (11) for compression, and the temperature and pressure are further increased; the compressed high-pressure gas enters the cooling channel of the regenerator (10) for heat exchange and cooling, and is divided into two paths by a three-way valve (12); when the filling unit is working, it enters the upper end of the low-temperature storage tank B (2), pressurizes the high-pressure gas and promotes the operation of the filling system; when the filling unit is not working, it enters the lower end of the low-temperature storage tank A (1) to complete the liquid replenishment in the storage tank.

[0030] The lower end of the cryogenic storage tank B (2) is connected to a gas filling machine (5) through a pipeline, and a switch (3) and a liquid flow meter (4) are arranged in the middle; the lower end of the cryogenic storage tank A (1) is connected to the cryogenic storage tank B (2) through a pipeline for replenishing liquid in the cryogenic storage tank A (2), and a one-way valve (13) is arranged in the middle; the upper ends of the cryogenic storage tank A (1) and the cryogenic storage tank B (2) are connected through a pipeline, and a switch (3) is arranged in the pipeline for balancing the pressure of the two tanks.

[0031] The collected gases in the cryogenic storage tank A (1) and the cryogenic storage tank B (2) are connected to the cooling and pressurizing unit through pipelines at the upper ends of the storage tanks, respectively. A one-way valve (13) is provided in the pipeline. After the gases are combined, they enter the regenerator (10) through a gas phase flow meter (9) and a switch (3).

[0032] The regenerator (10) has a heating channel and a cooling channel. The heating channel is used to heat the gas collected in the low-temperature storage tank and the flash gas generated during the filling process, and the cooling channel cools the high-pressure gas compressed by the low-temperature oil-free compressor (11).

[0033] After the gas enters the low-temperature oil-free compressor (11) for compression, its temperature and pressure further increase, and after becoming high-pressure gas, it enters the cooling channel of the regenerator (10) for cooling.

[0034] The high-pressure gas after heat exchange and temperature reduction through the cooling channel of the regenerator (10) is divided into two paths through the three-way valve (12). When the filling unit is working, it enters the upper end of the low-temperature storage tank B (2) to pressurize the high-pressure gas and promote the operation of the filling unit. When the filling unit is not working, it enters the lower end of the low-temperature storage tank A (1) to complete the liquid replenishment in the storage tank.

[0035] The low-temperature oil-free compressor (11) is supported by gas bearings, and is completely oil-free during the compression process, without the problem of oil removal and without the need for an oil return device.

[0036] The low-temperature oil-free compressor (11) can operate under low-temperature conditions, and the temperature of the compressible gas is lower than that of a normal-temperature compressor, without the need to heat up the low-temperature gas.

[0037] The low-temperature oil-free compressor (11) consumes less power when operating with low-temperature gas.

[0038] The above description and the accompanying drawings sufficiently illustrate the embodiments of the present disclosure to enable those skilled in the art to practice them. Other embodiments may include structural and other changes. The embodiments represent only possible variations. Unless explicitly required, individual components and functions are optional, and the order of operations may vary. Portions and features of some embodiments may be included in or replace portions and features of other embodiments. The embodiments of the present disclosure are not limited to the structures described above and shown in the accompanying drawings, and various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. An LNG station filling system using a cryogenic oil-free compressor, characterized in that: The system comprises a cryogenic storage tank A (1), a cryogenic storage tank B (2), a switch (3), a liquid phase flow meter (4), a gas filling machine (5), a gas filling gun (6), a user vehicle (7), a return air gun (8), a gas phase flow meter (9), a heat regenerator (10), a cryogenic oil-free compressor (11), a three-way valve (12), and a one-way valve (13), and is divided into a storage unit, a filling unit, and a cooling and pressurizing unit. The storage unit comprises a cryogenic storage tank A (1) and a cryogenic storage tank B (2). The liquid in the cryogenic storage tank B (2) is connected to the filling unit through a pipe at the lower end of the storage tank, and the gas is connected to the cooling and pressurizing unit through a pipe at the upper end of the storage tank. A switch (3) is installed on the upper end pipes of the cryogenic storage tank A (1) and the cryogenic storage tank B (2) for balancing the gas pressure of the two tanks. A transmission pipe is provided at the lower end of the cryogenic storage tank A (1) for replenishing liquid to the cryogenic storage tank B (2), and a one-way valve is provided in the middle. The filling unit includes a gas filling machine (5), a gas filling gun (6), a user vehicle (7), and a gas return gun (8). The flash gas generated during the filling process is collected by the gas return gun (8) and then connected to the cooling and pressurizing unit; the cooling and pressurizing unit includes a regenerator (10) and a low-temperature oil-free compressor (11). The regenerator (10) recovers the gas in the collected storage tank and the flash gas generated during the filling process and heats it up. The heated gas enters the low-temperature oil-free compressor (11) for compression, and the temperature and pressure are further increased. The compressed high-pressure gas enters the cooling channel of the regenerator (10) for heat exchange and cooling. It is divided into two paths through a three-way valve (12). When the filling unit is working, it enters the upper end of the low-temperature storage tank B (2) to pressurize the high-pressure gas and promote the operation of the filling system. When the filling unit is not working, it enters the lower end of the low-temperature storage tank A (1) to complete the liquid replenishment in the storage tank.

2. The LNG station filling system using a cryogenic oil-free compressor as claimed in claim 1, characterized in that: The lower end of the cryogenic storage tank B (2) is connected to a gas filling machine (5) through a pipeline, and a switch (3) and a liquid flow meter (4) are arranged in the middle; the lower end of the cryogenic storage tank A (1) is connected to the cryogenic storage tank B (2) through a pipeline for replenishing liquid in the cryogenic storage tank B (2), and a one-way valve (13) is arranged in the middle; the upper ends of the cryogenic storage tank A (1) and the cryogenic storage tank B (2) are connected through a pipeline, and a switch (3) is arranged in the pipeline for balancing the pressure of the two tanks.

3. The LNG station filling system using a cryogenic oil-free compressor as claimed in claim 1, characterized in that: The collected gases in the cryogenic storage tank A (1) and the cryogenic storage tank B (2) are connected to the cooling and pressurizing unit through pipelines at the upper ends of the storage tanks, respectively. A one-way valve (13) is provided in the pipeline. After the gases are combined, they enter the regenerator (10) through a gas phase flow meter (9) and a switch (3).

4. The LNG station filling system using a cryogenic oil-free compressor as claimed in claim 3, characterized in that: The regenerator (10) has a heating channel and a cooling channel. The heating channel is used to heat the gas collected in the low-temperature storage tank and the flash gas generated during the filling process, and the cooling channel cools the high-pressure gas compressed by the low-temperature oil-free compressor (11).

5. The LNG station filling system using a cryogenic oil-free compressor as claimed in claim 3, characterized in that: The temperature and pressure of the gas further increase after entering the low-temperature oil-free compressor (11) for compression, and the gas becomes high-pressure gas and enters the cooling channel of the regenerator (10) for cooling.

6. The LNG station filling system using a cryogenic oil-free compressor as claimed in claim 5, characterized in that: The high-pressure gas after heat exchange and temperature reduction through the cooling channel of the regenerator (10) is divided into two paths through a three-way valve (12).

7. The LNG station filling system using a cryogenic oil-free compressor as claimed in claim 1, characterized in that: The low-temperature oil-free compressor (11) is supported by gas bearings, and is completely oil-free during the compression process, without any oil removal problems and without the need for an oil return device.

8. The LNG station filling system using a cryogenic oil-free compressor as claimed in claim 7, characterized in that: The low-temperature oil-free compressor (11) can operate under low-temperature conditions, and the temperature of the compressible gas is lower than that of a normal-temperature compressor, without the need to heat up the low-temperature gas.

9. The LNG station filling system using a cryogenic oil-free compressor as claimed in claim 8, characterized in that: The low-temperature oil-free compressor (11) reduces power consumption under the working condition of low-temperature gas.

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