Natural gas supply station

Abstract

The present invention provides a natural gas supply station, including a storage tank, a vaporizer, a BOG reheater, and a multi-stage compressor. The vaporizer is connected to the storage tank and is used to vaporize liquefied natural gas to form gaseous natural gas; the BOG reheater is connected to the storage tank and is used to heat the evaporated gas in the storage tank so that the temperature of the evaporated gas rises to normal temperature; the multi-stage compressor includes at least two stages of compression mechanisms arranged in sequence from upstream to downstream; each compression mechanism has a cold source channel and a first medium channel capable of heat exchange, and the first medium channels of each compression mechanism are interconnected, the inlet of the first medium channel of the compression mechanism located in the first stage upstream is connected to the BOG reheater to receive the evaporated gas, and the outlet of the first medium channel of the compression mechanism located in the last stage downstream is connected to the outside world; the inlet of the cold source channel of each compressor is connected to the outlet of the vaporizer, and the outlet is connected to the outside world, so that the gaseous natural gas and the evaporated gas exchange heat, thereby cooling the evaporated gas after the compressor is pressurized.

Description

Technical Field

[0001] The present invention relates to the technical field of natural gas, and in particular to a natural gas supply station. Background Art

[0002] With the gradual rise of local small and medium-sized LNG storage stations, LNG (liquefied natural gas) has become the main way of urban fuel supply. In order to ensure safe storage, the temperature of LNG is usually much lower than the ambient temperature. Therefore, during the gas supply process, due to the temperature difference, different degrees of evaporation will occur in the natural gas supply station, thus generating BOG (boil-off gas). The generation of BOG will have a significant impact on the safe operation of the gas supply station, not only causing energy waste, but also increasing the cost investment of the gas supply station.

[0003] At present, most small and medium-sized LNG storage stations use multi-stage compressors to gradually compress BOG to a suitable pressure before delivering it to users to achieve BOG recovery. Among them, the compressor usually uses a normal temperature compressor, the process gas at the inlet is heated by air temperature and water bath, and the process gas at the outlet is forced air cooling or water cooling. However, the cost of the above recovery method is relatively high, which increases the cost of the LNG gas supply station. Summary of the invention

[0004] The object of the present invention is to provide a natural gas supply station to fully utilize the cold energy in the gas supply station and thus reduce energy consumption.

[0005] In order to solve the above technical problems, the present invention provides a natural gas supply station, including a storage tank, a vaporizer, a BOG reheater, and a multi-stage compressor;

[0006] The storage tank is used to store liquefied natural gas;

[0007] The vaporizer is connected to the storage tank and is used to vaporize the liquefied natural gas to form gaseous natural gas;

[0008] The BOG reheater is connected to the storage tank and is used to heat the boil-off gas in the storage tank so that the temperature of the boil-off gas rises to room temperature;

[0009] The multi-stage compressor includes at least two stages of compression mechanisms arranged in sequence from upstream to downstream; each stage of the compression mechanism has a cold source channel and a first medium channel capable of heat exchange, and the first medium channels of the compression mechanisms of each stage are interconnected, the inlet of the first medium channel of the compressor located in the first stage upstream is connected to the BOG reheater to receive the evaporated gas, and the outlet of the first medium channel of the compression mechanism located in the last stage downstream is connected to the outside; the inlet of the cold source channel of the compression mechanism of each stage is connected to the outlet of the vaporizer, and the outlet is connected to the outside, so that the gaseous natural gas and the evaporated gas exchange heat, thereby cooling the evaporated gas pressurized by the compressor.

[0010] In one embodiment, a BOG heat exchanger is further provided between the BOG reheater and the multi-stage compressor;

[0011] The BOG heat exchanger comprises a heat source channel and a second medium channel capable of performing heat exchange; the heat source channel is connected to the outlet of the cold source channel of the compression mechanism; the inlet of the second medium channel is connected to the BOG reheater, and the outlet is connected to the inlet of the first medium channel of the compression mechanism located upstream, so as to transport the evaporated gas into the first medium channel.

[0012] In one embodiment, a bypass pipe is further provided at the outlet of the cold source channel, the bypass pipe is arranged in parallel with the heat source channel of the BOG heat exchanger, and the outlet of the bypass pipe is connected to the outside.

[0013] In one embodiment, the bypass pipeline is provided with a first regulating valve with adjustable opening to adjust the flow rate of the gaseous natural gas entering the bypass pipeline.

[0014] In one embodiment, the bypass pipe is made of carbon steel or low-temperature steel.

[0015] In one embodiment, a second regulating valve with adjustable opening is provided between each compression mechanism and the vaporizer to regulate the gaseous natural gas entering the corresponding cold source channel.

[0016] In one embodiment, a NG reheater is further provided downstream of the vaporizer to heat the gaseous natural gas.

[0017] In one embodiment, the NG reheater is a water bath reheater.

[0018] In one embodiment, the pipes connecting the vaporizer and the compression mechanisms at each stage and the pipes connecting the compression mechanisms and the BOG heat exchanger are made of low-temperature steel or carbon steel.

[0019] In one embodiment, a control valve is provided between each stage of the compression mechanism and the vaporizer.

[0020] It can be seen from the above technical solution that the advantages and positive effects of the present invention are:

[0021] The natural gas supply station of the present invention uses NG after LNG vaporization as a cold source, and exchanges heat with BOG with a higher temperature after pressurization to reduce the temperature of BOG after pressurization, and finally realizes the recovery of BOG, making full use of the energy of the entire natural gas supply station, reducing the operating energy consumption of the compressor, thereby reducing the energy consumption of the entire natural gas supply station and saving costs. And because NG is a gas, even if it leaks, it has little effect on the performance of the compressor.

[0022] The natural gas supply station is suitable for long-term LNG gasification and transmission and BOG multi-stage compression. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of one embodiment of a natural gas supply station of the present invention.

[0024] The following are the descriptions of the reference numerals:

[0025] 1. Natural gas supply station; 11. Vaporizer; 12. NG recuperator; 13. BOG recuperator; 14. BOG heat exchanger; 15. First-stage compression mechanism; 16. Last-stage compression mechanism; 17. Bypass pipeline; 171. First regulating valve. DETAILED DESCRIPTION

[0026] Typical embodiments that embody the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different embodiments without departing from the scope of the present invention, and the descriptions and illustrations therein are essentially used for illustration purposes rather than for limiting the present invention.

[0027] In order to further illustrate the principle and structure of the present invention, preferred embodiments of the present invention are now described in detail with reference to the accompanying drawings.

[0028] The present invention provides a natural gas supply station for providing natural gas, which fully utilizes the coldness of NG (gaseous natural gas) to reduce the temperature of BOG, reduce the recovery cost of BOG, and further reduce the cost of the entire natural gas supply station.

[0029] See also Figure 1 The natural gas supply station 1 includes a storage tank (not shown in the figure), a vaporizer 11, an NG recuperator 12, a BOG recuperator 13 and a multi-stage compressor.

[0030] Storage tanks are used to store liquefied natural gas. The storage tanks have an inlet, a liquid outlet, and a gas outlet. The inlet is used to fill the liquefied natural gas, and the outlet is used to export the liquefied natural gas. The heat from the external environment intrudes into the storage tank, which will increase the temperature of the liquefied natural gas in the storage tank and form BOG.

[0031] The inlet of the vaporizer 11 is connected to the liquid outlet of the storage tank to receive liquefied natural gas, vaporize the liquefied natural gas to form NG (gaseous natural gas), and transport it to the outside to meet the demand for city gas.

[0032] Specifically, the vaporizer 11 is an air-temperature type vaporizer 11 .

[0033] The NG reheater 12 is disposed downstream of the vaporizer 11 and connected to the outlet of the vaporizer 11 to reheat the NG (gaseous natural gas) so that the NG meets the temperature requirement for external transportation. The outlet of the NG reheater 12 is connected to the outside to transport the NG.

[0034] Specifically, the NG recuperator 12 is a water bath type recuperator.

[0035] The BOG reheater 13 is connected to the gas outlet of the storage tank to receive the BOG in the storage tank and heat the BOG to room temperature.

[0036] The multi-stage compressor is arranged downstream of the BOG reheater 13, and is used to compress the BOG and increase the pressure of the BOG. ​​When the pressure of the BOG is increased to meet the external transmission conditions, the BOG can be output externally.

[0037] Specifically, in this embodiment, the multi-stage compressor includes a first-stage compression mechanism 15, an intermediate compression mechanism, and a final compression mechanism 16 arranged in sequence from upstream to downstream. That is, after the BOG is pressurized by the first-stage compression mechanism 15, it continues to enter the intermediate compression mechanism for re-pressurization, and then enters the final compression mechanism 16 for re-pressurization until the external transmission conditions are met. After the BOG is pressurized, the temperature rises and needs to be cooled.

[0038] In other embodiments, the number of intermediate compression mechanisms in the multi-stage compressor may be two, three or other numbers, or may include only a first-stage compression mechanism 15 and a final-stage compression mechanism 16, which may be specifically configured according to actual conditions.

[0039] Specifically, the first-stage compression mechanism 15, the intermediate compression mechanism and the final-stage compression mechanism 16 all have a cold source channel and a first medium channel capable of heat exchange, that is, the cold source in the cold source channel exchanges heat with the medium in the first medium channel, so that the cold source in the cold source channel cools the medium in the first medium channel.

[0040] The inlet of the first medium channel of the primary compression mechanism 15 is communicated with the outlet of the BOG recuperator 13 to receive BOG.

[0041] The inlet of the first medium passage of the intermediate compression mechanism is connected to the outlet of the first medium passage of the primary compression mechanism 15 to receive the BOG pressurized by the primary compression mechanism 15 .

[0042] The inlet of the first medium passage of the final compression mechanism 16 is connected to the outlet of the first medium passage of the intermediate compression mechanism to receive the BOG pressurized by the intermediate compression mechanism.

[0043] The inlet of the cold source channel of each compression mechanism is connected to the outlet of the vaporizer 11 to receive NG. That is, the cold source channels of each compression mechanism are arranged in parallel downstream of the vaporizer 11.

[0044] Specifically, a control valve is provided between each compression mechanism and the vaporizer 11 to control the connection or disconnection between the compression mechanism and the vaporizer 11 .

[0045] Furthermore, a second regulating valve with adjustable opening is provided between each control valve and the corresponding compression mechanism to regulate the NG entering each cold source channel.

[0046] Because the temperature of NG after LNG is gasified at air temperature is usually about 10°C lower than the ambient temperature, the temperature of the pressurized BOG is relatively high, and thus NG can be used as a cold source. NG is in the cold source channel, and the pressurized BOG is located in the first medium channel. NG cools the pressurized BOG with a relatively high temperature, thereby ensuring that the temperature of the BOG entering the next stage compression mechanism 15 is at room temperature.

[0047] Furthermore, a BOG heat exchanger 14 is provided between the BOG recuperator 13 and the primary compression mechanism 15 to reheat the BOG outputted from the BOG recuperator 13 to ensure that the BOG entering the primary compression mechanism 15 is at room temperature. When the ambient temperature is high, the temperature of the BOG outputted from the BOG recuperator 13 meets the requirement for entering the primary compression mechanism 15, and the BOG heat exchanger 14 is not required to reheat the BOG. ​​When the ambient temperature is cold, the BOG outputted from the BOG recuperator 13 still does not reach the required temperature, and the BOG heat exchanger 14 is required to reheat the BOG.

[0048] The BOG heat exchanger 14 has a heat source channel and a second medium channel capable of heat exchange, that is, the heat source in the heat source channel exchanges heat with the medium in the second medium channel, so that the heat source in the heat source channel heats the medium in the second medium channel.

[0049] The inlet of the heat source channel is connected to the outlet of the cold source channel of the compression mechanism to receive the NG in the cold source channel. At this time, the NG exchanges heat with the pressurized BOG with a higher temperature and has a higher temperature, so it can serve as a heat source.

[0050] The outlet of the heat source channel is connected to the outside, and outputs NG to the outside.

[0051] The inlet of the second medium channel is communicated with the outlet of the BOG recuperator 13 , and the outlet of the second medium channel is communicated with the primary compressor 15 .

[0052] When the temperature of BOG in the second medium channel is lower than normal temperature, NG in the heat source channel provides heat and exchanges heat with BOG in the second medium channel, so that BOG entering the primary compression mechanism 15 is at normal temperature. When BOG in the second medium channel can directly enter the primary compressor 15 without heating, NG can be directly output to the outside.

[0053] A bypass pipe 17 is also provided at the outlet of the cold source channel. The inlet of the bypass pipe 17 is connected to the outlet of the cold source channel, and the outlet is connected to the outside, so that the NG in the cold source channel can be directly transported to the outside. The bypass pipe 17 is arranged in parallel with the hot source channel.

[0054] That is, when the BOG outputted from the BOG reheater 13 does not need to be reheated, the NG in the cold source channel can be directly transported outward through the bypass pipe 17. When the BOG outputted from the BOG reheater 13 needs to be reheated, the NG in the cold source channel enters the hot source channel for heat exchange, and then outputs BOG meeting the temperature requirement.

[0055] Furthermore, a first regulating valve 171 with an adjustable opening is provided on the bypass pipeline 17 to adjust the flow rate of NG entering the bypass pipeline 17 .

[0056] The bypass pipe 17 is made of carbon steel or low-temperature steel.

[0057] In this embodiment, a branch pipeline is further provided in parallel with the BOG recuperator 13 , and the branch pipeline is located upstream of the BOG heat exchanger 14 .

[0058] A valve is provided on the branch pipeline to control the on-off of the branch pipeline.

[0059] The gas supply process of the natural gas supply station 1 when BOG is not generated is as follows: the control valve between the vaporizer 11 and each compression mechanism is closed, and the NG vaporized by the vaporizer 11 will not enter the compression mechanism, but will all enter the NG reheater 12 to be reheated and then output to the outside.

[0060] The natural gas supply station 1 recovers BOG after generating BOG as follows: the control valve between the vaporizer 11 and each compression mechanism is opened, and part of the NG vaporized by the vaporizer 11 enters the compression mechanism, and part enters the NG reheater 12 to be reheated and then output to the outside.

[0061] At this time, the BOG reheater 13 receives and heats the BOG, and then sends it to the BOG heat exchanger 14, where the NG in the heat source channel heats the BOG to room temperature, and then sends it to the first-stage compression mechanism 15, the intermediate compression mechanism and the final compression mechanism 16, where the BOG with a high temperature after pressurization is cooled by the NG in the cold source channel, so that the BOG entering each compressor is at room temperature. The BOG output by the final compression mechanism 16 is directly output to the outside, thereby realizing BOG recovery.

[0062] Since LNG vaporized at air temperature is used as a cold source to cool BOG and recover BOG, and since the NG temperature is usually 10°C lower than the ambient temperature, the pipes connecting the vaporizer 11 and the compressor and the pipes connecting the compressor and the BOG heat exchanger 14 are made of low-temperature steel or carbon steel. And the pipes do not need to be kept cold.

[0063] The natural gas supply station 1 in this embodiment uses NG after LNG vaporization as a cold source to reduce the temperature of the pressurized BOG, and the NG after absorbing heat can be used to heat the BOG that needs to be heated, making full use of the energy of the entire natural gas supply station 1, such as heat and cold, reducing the operating energy consumption of the compressor, reducing the energy consumption of the BOG reheater 13, thereby reducing the energy consumption of the entire natural gas supply station 1 and saving costs. And because NG is gas, even if it leaks, it has little effect on the performance of the compressor.

[0064] The natural gas supply station 1 is suitable for the working conditions of long-term LNG gasification and external transmission and BOG multi-stage compression.

[0065] It can be seen from the above technical solution that the advantages and positive effects of the present invention are:

[0066] The natural gas supply station of the present invention uses NG after LNG vaporization as a cold source, and exchanges heat with BOG with a higher temperature after pressurization to reduce the temperature of BOG after pressurization, and finally realizes the recovery of BOG, making full use of the energy of the entire natural gas supply station, reducing the operating energy consumption of the compressor, thereby reducing the energy consumption of the entire natural gas supply station and saving costs. And because NG is a gas, even if it leaks, it has little effect on the performance of the compressor.

[0067] The natural gas supply station is suitable for long-term LNG gasification and transmission and BOG multi-stage compression.

[0068] Although the present invention has been described with reference to several typical embodiments, it should be understood that the terms used are illustrative and exemplary, rather than restrictive. Since the present invention can be embodied in a variety of forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims, so all changes and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. A natural gas supply station, characterized in that: Including storage tanks, vaporizers, BOG reheaters, and multi-stage compressors; The storage tank is used to store liquefied natural gas; The vaporizer is connected to the storage tank and is used to vaporize the liquefied natural gas to form gaseous natural gas; The BOG reheater is connected to the storage tank and is used to heat the boil-off gas in the storage tank so that the temperature of the boil-off gas rises to room temperature; The multi-stage compressor comprises at least two stages of compression mechanisms arranged in sequence from upstream to downstream; each stage of the compression mechanism has a cold source channel and a first medium channel capable of heat exchange, and the first medium channels of the compression mechanisms of each stage are interconnected, the inlet of the first medium channel of the compressor located in the first stage upstream is connected to the BOG reheater to receive the evaporation gas, and the outlet of the first medium channel of the compression mechanism located in the last stage downstream is connected to the outside; the inlet of the cold source channel of the compression mechanism of each stage is connected to the outlet of the vaporizer, and the outlet is connected to the outside, so that the gaseous natural gas and the evaporation gas exchange heat, thereby cooling the evaporation gas pressurized by the compressor; A BOG heat exchanger is further provided between the BOG reheater and the multi-stage compressor, and the BOG heat exchanger has a heat source channel and a second medium channel capable of performing heat exchange; an inlet of the heat source channel is communicated with an outlet of a cold source channel of the compression mechanism, and an outlet of the heat source channel is communicated with the outside; an inlet of the second medium channel is communicated with the BOG reheater, and an outlet is communicated with an inlet of the first medium channel of the compression mechanism located upstream, so as to transport the evaporated gas into the first medium channel.

2. The natural gas supply station according to claim 1, characterized in that: A bypass pipe is also provided at the outlet of the cold source channel. The bypass pipe is arranged in parallel with the heat source channel of the BOG heat exchanger, and the outlet of the bypass pipe is communicated with the outside.

3. The natural gas supply station according to claim 2, characterized in that: The bypass pipeline is provided with a first regulating valve with adjustable opening to regulate the flow of the gaseous natural gas entering the bypass pipeline.

4. The natural gas supply station according to claim 2, characterized in that: The bypass pipeline is made of carbon steel or low-temperature steel.

5. The natural gas supply station according to claim 1, characterized in that: A second regulating valve with adjustable opening is provided between each of the compression mechanisms and the vaporizer to regulate the gaseous natural gas entering the corresponding cold source channel.

6. The natural gas supply station according to claim 1, characterized in that: An NG recuperator is further provided downstream of the vaporizer to heat the gaseous natural gas.

7. The natural gas supply station according to claim 6, characterized in that: The NG reheater is a water bath type reheater.

8. The natural gas supply station according to claim 1, characterized in that: The material of the pipeline connecting the vaporizer and the compression mechanism at each stage and the pipeline connecting the compression mechanism and the BOG heat exchanger is low-temperature steel or carbon steel.

9. The natural gas supply station according to claim 1, characterized in that: A control valve is provided between each stage of the compression mechanism and the vaporizer.

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