Cold energy stepped utilization system and method in natural gas pressure regulating station

Abstract

The invention relates to the technical field of LNG cold energy utilization, in particular to a cold energy stepped utilization system and method in a natural gas pressure regulating station. The cold energy stepped utilization system in the natural gas pressure regulating station comprises an LNG storage tank, a cold box, an LNG reheating heat exchanger, a sub high-temperature water supply system, a sub refrigerant conveying system, a natural gas pipe network, a sub low-temperature water return system and a sub refrigerant reheating system, and the outlet end of the LNG storage tank communicates with the first inlet end of the cold box. According to the system, through the arranged cold box, a refrigerant in the LNG storage tank can be heated for the first time, liquid-phase LNG is changed into gas-phase LNG, through the arranged LNG reheating heat exchanger, LNG can be heated for the second time, the sub refrigerant reheating system exchanges heat with the sub high-temperature water supply system, the temperature of the cold box and the temperature of the refrigerant in the LNG reheating heat exchanger are increased, and the heat exchange effect is improved; as the heating process is stepped, the gasification effect is better, and more energy is saved by exchanging heat with the sub high-temperature water supply system.

Description

Technical Field

[0001] The present invention relates to the technical field of LNG cold energy utilization, and in particular to a cold energy step utilization system and method in a natural gas pressure regulating station. Background Art

[0002] The demand for gas in cities has obvious fluctuation characteristics, but the gas produced by gas fields every day is basically unchanged. Therefore, effective peak-shaving measures are usually taken to alleviate the problem of uneven gas efficiency.

[0003] As an effective way to implement gas peak load regulation, LNG is widely used by natural gas pressure regulating stations. Liquefied natural gas (LNG) is a form of natural gas that is liquefied with methane as the main component. Its volume is reduced by 620 times, and its storage and transportation methods are flexible and convenient for transportation. At present, LNG has become the main supplementary gas source and peak load emergency gas source for cities that use pipeline natural gas for gas supply. The LNG peak load regulation station starts working when the city's natural gas consumption is at its peak, starts the LNG gasifier, and gasifies the LNG and sends it into the pipeline network. When the city's natural gas consumption is at its low point, the LNG peak load regulation station does not work, and the natural gas in the pipeline network does not enter the LNG peak load regulation station.

[0004] The implementation of gas peak shaving with liquefied natural gas (LNG) involves the gasification of LNG. Usually, LNG is heated by an air vaporizer to make it gasified. Since LNG contains a large amount of cold energy, the air vaporizer heats LNG to make it gasified. During the gasification process, a large amount of "white smoke" appears around the air vaporizer in the natural gas peak shaving station, which not only affects the operation and maintenance vision in the natural gas pressure regulating station, but also causes ice on the outside of the air vaporizer, affecting the gasification effect, and causing a large waste of cold energy, which is not conducive to energy saving. Summary of the invention

[0005] (I) The problem to be solved by the present invention is: how to avoid affecting the gasification effect and causing a large amount of waste of cold energy, thereby facilitating energy saving.

[0006] (II) Technical solution

[0007] The present invention provides a cold energy step-by-step utilization system in a natural gas pressure regulating station, comprising an LNG storage tank, a cold box, an LNG recuperation heat exchanger, a sub-high-temperature water supply system, a sub-refrigerant delivery system, a natural gas pipeline network, a sub-low-temperature water return system, and a sub-refrigerant recuperation system;

[0008] The outlet end of the LNG storage tank is connected to the first inlet end of the cold box, the first outlet end of the cold box is connected to the first inlet end of the LNG recuperation heat exchanger, and the first outlet end of the LNG recuperation heat exchanger is connected to the natural gas pipeline network;

[0009] The inlet end of the sub-refrigerant recovery system is connected to the second outlet end of the cold box, the outlet end of the sub-refrigerant recovery system is connected to the second inlet end of the LNG recovery heat exchanger, and the second outlet end of the LNG recovery heat exchanger and the outlet end of the sub-refrigerant delivery system are both connected to the second inlet end of the cold box;

[0010] The high-temperature water of the sub-high-temperature water supply system is transported to the sub-low-temperature return water system after heat exchange through the sub-refrigerant reheating system. The sub-low-temperature return water system is used to transport the low-temperature water formed after heat exchange of the high-temperature water to the sub-high-temperature water supply system.

[0011] According to one embodiment of the present invention, the sub-refrigerant delivery system includes a refrigerant pipe network and a second refrigerant pipe;

[0012] The sub-refrigerant recovery system includes a refrigerant transport device, the second outlet end of the cold box is connected to the inlet end of the second refrigerant pipe through the refrigerant transport device, the outlet end of the second refrigerant pipe is connected to the refrigerant pipe network, and the refrigerant pipe network is connected to the second inlet end of the cold box.

[0013] According to one embodiment of the present invention, the sub-high-temperature water supply system includes a high-temperature air-conditioning water pipeline and an air-conditioning water network, the sub-low-temperature water return system includes a low-temperature air-conditioning water pipeline, and the sub-refrigerant reheating system also includes a first heat exchanger;

[0014] The refrigerant transport device comprises a refrigerant buffer tank, a booster pump, and a first three-way valve which are connected in sequence;

[0015] The inlet end of the refrigerant buffer tank is connected to the second outlet end of the cold box through a first refrigerant pipe;

[0016] The refrigerant buffer tank has a gas outlet end, and the gas outlet end is connected to the second inlet end of the cold box through a refrigerant gas pipeline;

[0017] The first outlet end of the first three-way valve is connected through the inlet end of the second refrigerant pipe, the second outlet end of the first three-way valve is connected to the first inlet end of the first heat exchanger through the third refrigerant pipe, and the first outlet end of the first heat exchanger is connected to the second inlet end of the LNG recuperation heat exchanger;

[0018] The outlet end of the high-temperature air-conditioning water pipeline is connected to the second inlet end of the first heat exchanger, and the second outlet end of the first heat exchanger is connected to the low-temperature air-conditioning water pipeline;

[0019] The outlet end of the low-temperature air-conditioning water pipeline and the inlet end of the high-temperature air-conditioning water pipeline are both connected to the air-conditioning water network;

[0020] The first refrigerant pipe, the second refrigerant pipe and the third refrigerant pipe are all provided with a first ball valve.

[0021] According to one embodiment of the present invention, the high-temperature air-conditioning water pipeline includes a first air-conditioning water pipeline, a water tank, a water pump and a second three-way valve;

[0022] The inlet end of the first air conditioning water pipe is connected to the outlet end of the water tank, and the outlet end thereof is connected to the inlet end of the water pump, and the outlet end of the water pump is connected to the first inlet end of the second three-way valve;

[0023] The second inlet end of the second three-way valve is connected to the purified water pipe network, and the outlet end thereof is connected to the second inlet end of the first heat exchanger.

[0024] According to one embodiment of the present invention, the sub-refrigerant reheating system further includes a second heat exchanger, the sub-high-temperature water supply system further includes a circulating water network and a high-temperature circulating water pipeline, and the sub-low-temperature water return system further includes a low-temperature circulating water pipeline;

[0025] The first outlet end of the first heat exchanger is connected to the first inlet end of the second heat exchanger, and the first outlet end of the second heat exchanger is connected to the second inlet end of the LNG recuperation heat exchanger;

[0026] The inlet end of the high-temperature circulating water pipeline and the outlet end of the low-temperature circulating water pipeline are both connected to the circulating water network;

[0027] The outlet end of the high-temperature circulating water pipeline is connected to the second inlet end of the second heat exchanger, and the inlet end of the low-temperature circulating water pipeline is connected to the second outlet end of the second heat exchanger.

[0028] According to one embodiment of the present invention, the cold energy step utilization system further includes a first LNG pipeline, a second LNG pipeline, a first natural gas pipeline, a second natural gas pipeline, a first regulating valve and a temperature controller;

[0029] The outlet end of the LNG storage tank is connected to the inlet end of the first regulating valve through the first LNG pipeline, and the outlet end of the first regulating valve is connected to the first inlet end of the cold box through the outlet end of the second LNG pipeline;

[0030] The first outlet end of the cold box is connected to the first inlet end of the LNG recuperation heat exchanger through the first natural gas pipeline;

[0031] The first outlet end of the LNG recuperation heat exchanger is connected to the inlet end of the temperature controller through the second natural gas pipeline, and the outlet end of the temperature controller is connected to the natural gas pipeline network through the second connecting pipe;

[0032] The first LNG pipeline, the second LNG pipeline, the first natural gas pipeline, and the second natural gas pipeline are all provided with a second ball valve.

[0033] According to one embodiment of the present invention, the cold energy step-by-step utilization system further includes a first temperature meter and a controller;

[0034] The first temperature meter is arranged on the first natural gas pipeline, and the first temperature meter and the first regulating valve are both electrically connected to the controller;

[0035] The second connecting pipe and the second natural gas pipeline are both provided with a second thermometer.

[0036] A method for stepwise utilization of cold energy in a natural gas pressure regulating station comprises the following steps:

[0037] S1: Open all the first ball valves, the second ball valves, the first three-way valves, the second three-way valves and the first regulating valve. The sub-refrigerant delivery system inputs hot gaseous refrigerant into the cold box. The LNG in the LNG storage tank passes through the cold box and performs the first heat exchange with the hot gaseous refrigerant in the cold box. The liquefied natural gas is converted from liquid phase to gas phase and then enters the LNG reheating heat exchanger.

[0038] S2: LNG continues to be heated up for a second time in the LNG recuperation heat exchanger until the temperature measured by the second thermometer located on the second connecting pipe reaches a predetermined temperature and then enters the natural gas pipeline network;

[0039] The refrigerant in the cold box is transported to the refrigerant buffer tank. The gaseous refrigerant on the top of the refrigerant buffer tank is discharged from the gas outlet of the refrigerant buffer tank, passes through the refrigerant gas pipeline and merges with the hot gaseous refrigerant in the LNG recuperation heat exchanger after releasing the cold energy, and returns to the cold box for heat exchange with LNG.

[0040] The liquid refrigerant at the bottom of the refrigerant buffer tank is transported to the first three-way valve by the booster pump and then divided into two paths: one path is transported to the refrigerant network through the first outlet end of the first three-way valve and the second refrigerant pipe, and the other path is transported to the refrigerant network through the second outlet end of the first three-way valve and the first heat exchanger and the second heat exchanger respectively, and then heated up and transported to the LNG reheat exchanger to continue to exchange heat with LNG.

[0041] According to one embodiment of the present invention, in step S1, when the first thermometer detects that the temperature of LNG passing through the first natural gas pipeline is too low after heat exchange in the cold box, the flow rate of LNG passing through the cold box is reduced by reducing the opening of the first regulating valve.

[0042] According to one embodiment of the present invention, in step S2, when the air-conditioning water loss in the high-temperature air-conditioning water pipeline is large, the second three-way valve is adjusted to replenish purified water to the high-temperature air-conditioning water pipeline through the purified water pipeline network.

[0043] Beneficial effects of the present invention:

[0044] By setting up the cold box, the refrigerant in the LNG storage tank can be heated for the first time, so that the liquid phase LNG is changed into the gas phase. By setting up the LNG recuperation heat exchanger, the LNG can be heated for the second time. By setting up the sub-refrigerant recuperation system, heat can be exchanged with the sub-high-temperature water supply system to increase the temperature of the refrigerant in the cold box and the LNG recuperation heat exchanger, and improve the heat exchange effect. Because the heating process is step-by-step, replacing the traditional air vaporizer, a large amount of "white smoke" will not appear around the LNG recuperation heat exchanger and the cold box in the natural gas peak-shaving station during the gasification process, and it will not affect the operation and maintenance vision in the natural gas pressure regulating station. The outer surface of the LNG recuperation heat exchanger and the cold box is not easy to freeze, and the gasification effect is better. In addition, heat is exchanged with the sub-high-temperature water supply system. The high-temperature water in the sub-high-temperature water supply system transfers heat to the refrigerant, and the temperature of the high-temperature water is reduced to form low-temperature water, which flows into the sub-low-temperature return water system and is transported back to the sub-high-temperature water supply system through the low-temperature return water system. The cold energy is fully and reasonably utilized, and a large amount of cold energy is not wasted, which is more energy-saving. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0046] Figure 1 A schematic diagram of a system for cascaded utilization of cold energy in a natural gas pressure regulating station provided in an embodiment of the present invention.

[0047] Icons: 1. LNG storage tank; 2. Cold box; 3. LNG recuperation heat exchanger; 4. Refrigerant buffer tank; 5. Booster pump; 6. First heat exchanger; 7. Second heat exchanger; 8. Water tank; 10. Temperature controller; 11. Natural gas pipeline network; 12. Refrigerant pipeline network; 13. Air conditioning water pipeline network; 14. Purified water pipeline network; 15. Circulating water pipeline network; 16. First three-way valve; 17. First refrigerant pipe; 18. Second refrigerant pipe; 19. Third refrigerant pipe; 20. Low-temperature air conditioning water pipeline; 21. First air-conditioning water pipeline; 22. Second three-way valve; 23. High-temperature circulating water pipeline; 24. Low-temperature circulating water pipeline; 25. First LNG pipeline; 26. First regulating valve; 27. Second LNG pipeline; 28. First natural gas pipeline; 29. ​​Second natural gas pipeline; 30. Second connecting pipe; 31. First thermometer; 32. First ball valve; 33. Second ball valve; 34. Second thermometer; 35. Water pump; 36. Refrigerant gas pipeline; 37. Flange. DETAILED DESCRIPTION

[0048] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0049] Embodiment 1:

[0050] like Figure 1 As shown, an embodiment of the present invention provides a cold energy step utilization system in a natural gas pressure regulating station, including an LNG storage tank 1, a cold box 2, an LNG recuperation heat exchanger 3, a sub-high-temperature water supply system, a sub-refrigerant transportation system, a natural gas pipeline network 11, a sub-low-temperature return water system, and a sub-refrigerant recuperation system;

[0051] The outlet end of the LNG storage tank 1 is connected to the first inlet end of the cold box 2, the first outlet end of the cold box 2 is connected to the first inlet end of the LNG recuperation heat exchanger 3, and the first outlet end of the LNG recuperation heat exchanger 3 is connected to the natural gas pipeline network 11;

[0052] The inlet end of the sub-refrigerant reheating system is connected to the second outlet end of the cold box 2, the outlet end of the sub-refrigerant reheating system is connected to the second inlet end of the LNG reheating heat exchanger 3, and the second outlet end of the LNG reheating heat exchanger 3 and the outlet end of the sub-refrigerant delivery system are both connected to the second inlet end of the cold box 2;

[0053] The high-temperature water of the sub-high-temperature water supply system is transported to the sub-low-temperature return water system after heat exchange through the sub-refrigerant reheating system. The sub-low-temperature return water system is used to transport the low-temperature water formed after heat exchange of the high-temperature water to the sub-high-temperature water supply system.

[0054] By setting up the cold box 2, the refrigerant in the LNG storage tank 1 can be heated for the first time, so that the liquid phase LNG is changed into the gas phase. By setting up the LNG recuperation heat exchanger 3, the LNG can be heated for the second time. By setting up the sub-refrigerant recuperation system, heat can be exchanged with the sub-high-temperature water supply system to increase the temperature of the refrigerant in the cold box 2 and the LNG recuperation heat exchanger 3, and improve the heat exchange effect. Because the heating process is step-by-step, replacing the traditional air vaporizer, a large amount of "white smoke" will not appear around the LNG recuperation heat exchanger 3 and the cold box 2 in the natural gas peak-shaving station during the gasification process, and it will not affect the operation and maintenance field of view in the natural gas pressure regulating station. The outer surface of the LNG recuperation heat exchanger 3 and the cold box 2 is not easy to freeze, and the gasification effect is better. In addition, heat is exchanged with the sub-high-temperature water supply system. The high-temperature water in the sub-high-temperature water supply system transfers heat to the refrigerant, and the temperature of the high-temperature water is reduced to form low-temperature water, which flows into the sub-low-temperature return water system and is transported back to the sub-high-temperature water supply system through the low-temperature return water system. The cold energy is fully and reasonably utilized, and a large amount of cold energy is not wasted, which is more energy-saving.

[0055] In addition, there is currently a method of heating and gasifying the LNG in the LNG storage tank 1 by using a seawater heater. Compared with this method, this embodiment has lower geographical requirements, does not need to be built in coastal areas, and is more practical.

[0056] According to one embodiment of the present invention, the sub-refrigerant delivery system includes a refrigerant pipe network 12 and a second refrigerant pipe 18;

[0057] The sub-refrigerant reheating system includes a refrigerant transport device, the second outlet end of the cold box 2 is connected to the inlet end of the second refrigerant pipe 18 through the refrigerant transport device, the outlet end of the second refrigerant pipe 18 is connected to the refrigerant pipe network 12, and the refrigerant pipe network 12 is connected to the second inlet end of the cold box 2.

[0058] The first outlet end of the refrigerant transport device is connected to the second refrigerant pipe 18 , and the second outlet end of the refrigerant transport device is connected to the first inlet end of the first heat exchanger 6 .

[0059] Through the second refrigerant pipe 18 and the refrigerant transportation device, the refrigerant after absorbing cold energy can be heat exchanged with the refrigerant in the refrigerant network 12 (the refrigerant at the user end outside the station), and then transported to the second inlet end of the cold box 2 for heat exchange with LNG, which has higher heat exchange efficiency.

[0060] According to one embodiment of the present invention, the sub-high-temperature water supply system includes a high-temperature air-conditioning water pipeline and an air-conditioning water network 13, the sub-low-temperature water return system includes a low-temperature air-conditioning water pipeline 20, and the sub-refrigerant reheating system also includes a first heat exchanger 6;

[0061] The refrigerant transport device includes a refrigerant buffer tank 4, a booster pump 5, and a first three-way valve 16 which are connected in sequence;

[0062] The inlet end of the refrigerant buffer tank 4 is connected to the second outlet end of the cold box 2 through the first refrigerant pipe 17;

[0063] The refrigerant buffer tank 4 has a gas outlet end, which is connected to the second inlet end of the cold box 2 through a refrigerant gas pipeline 36;

[0064] The first outlet end of the first three-way valve 16 is connected to the inlet end of the second refrigerant pipe 18, the second outlet end of the first three-way valve 16 is connected to the first inlet end of the first heat exchanger 6 through the third refrigerant pipe 19, and the first outlet end of the first heat exchanger 6 is connected to the second inlet end of the LNG recuperation heat exchanger 3;

[0065] The outlet end of the high-temperature air-conditioning water pipeline is connected to the second inlet end of the first heat exchanger 6, and the second outlet end of the first heat exchanger 6 is connected to the low-temperature air-conditioning water pipeline 20;

[0066] The outlet end of the low-temperature air-conditioning water pipeline 20 and the inlet end of the high-temperature air-conditioning water pipeline are both connected to the air-conditioning water network 13;

[0067] The first refrigerant pipe 17 , the second refrigerant pipe 18 , and the third refrigerant pipe 19 are each provided with a first ball valve 32 .

[0068] According to one embodiment of the present invention, the high temperature air conditioning water pipeline includes a first air conditioning water pipeline 21, a water tank 8, a water pump 35 and a second three-way valve 22;

[0069] The inlet end of the first air conditioning water pipe 21 is connected to the outlet end of the water tank 8, and the outlet end thereof is connected to the inlet end of the water pump 35, and the outlet end of the water pump 35 is connected to the first inlet end of the second three-way valve 22;

[0070] A second inlet end of the second three-way valve 22 is connected to the purified water pipe network 14 , and an outlet end thereof is connected to a second inlet end of the first heat exchanger 6 .

[0071] The high-temperature air-conditioning water pipeline set up can cool the high-temperature water generated by the air conditioner, and its heat is exchanged with the refrigerant in the sub-refrigerant recovery system through the first heat exchanger 6, so that the temperature of the refrigerant is increased and then enters the LNG recovery heat exchanger 3, which can better heat the refrigerant and achieve a better gasification effect. LNG transfers cold energy to the refrigerant, and the refrigerant carries the cold energy to the high-temperature air-conditioning water pipeline that needs to be cooled, and the reciprocating circulation is used, which is more energy-saving.

[0072] The cold energy step-by-step utilization system in the natural gas pressure regulating station also includes a controller, and the first ball valve 32, the second ball valve 33, the first three-way valve 16, the second three-way valve 22, the first regulating valve 26, the second regulating valve, the third regulating valve, the first thermometer 31, the second thermometer 34, the water pump 35, the booster pump 5, the third thermometer and the fourth thermometer are all electrically connected to the controller.

[0073] Furthermore, a second regulating valve and a third thermometer are provided on the first refrigerant pipe 17. The third thermometer is located between the second regulating valve and the second outlet end of the cold box 2. When the third thermometer detects that the temperature of the refrigerant is too high, it sends a signal to the controller. The controller controls the second regulating valve to reduce its opening so as to achieve better heat exchange.

[0074] The first three-way valve 16 can be used to change the flow rate of heat exchange through the refrigerant network 12, and the second three-way valve 22 can be used to determine the flow rate involved in the purified water network 14. In addition, the first three-way valve 16 and the second three-way valve 22 can also use ordinary three-way valves, which do not play a regulating role and are only used for diversion.

[0075] According to one embodiment of the present invention, the sub-refrigerant reheating system further includes a second heat exchanger 7, the sub-high-temperature water supply system further includes a circulating water network 15 and a high-temperature circulating water pipeline 23, and the sub-low-temperature water return system further includes a low-temperature circulating water pipeline 24;

[0076] The first outlet end of the first heat exchanger 6 is connected to the first inlet end of the second heat exchanger 7, and the first outlet end of the second heat exchanger 7 is connected to the second inlet end of the LNG recuperation heat exchanger 3;

[0077] The inlet end of the high-temperature circulating water pipeline 23 and the outlet end of the low-temperature circulating water pipeline 24 are both connected to the circulating water network 15;

[0078] The outlet end of the high-temperature circulating water pipeline 23 is connected to the second inlet end of the second heat exchanger 7 , and the inlet end of the low-temperature circulating water pipeline 24 is connected to the second outlet end of the second heat exchanger 7 .

[0079] By applying the circulating water network 15 within the factory to the gasification process of LNG, the high-temperature water in the circulating water network 15 within the factory can be cooled and reused, which can not only meet the cooling needs of the high-temperature circulating water, but also heat the refrigerant, making its temperature in the LNG reheat exchanger 3 higher, and the effect of heating the LNG is better.

[0080] Furthermore, the first outlet end of the second heat exchanger 7 is connected to the LNG recuperation heat exchanger 3 through a fourth refrigerant pipe, a fourth thermometer is provided on the fourth refrigerant pipe, and a third regulating valve is provided on the high-temperature circulating water pipeline 23. When the temperature in the fourth thermometer shows that the temperature of the refrigerant is low, the fourth thermometer transmits a signal to the controller, and the controller increases the opening of the third regulating valve, so that the flow rate of high-temperature water in the high-temperature circulating water pipeline 23 is greater, and then more heat enters the second heat exchanger 7 to exchange heat with the refrigerant, thereby increasing the refrigerant temperature.

[0081] According to one embodiment of the present invention, the cold energy step utilization system further includes a first LNG pipeline 25, a second LNG pipeline 27, a first natural gas pipeline 28, a second natural gas pipeline 29, a first regulating valve 26 and a temperature controller 10;

[0082] The outlet end of the LNG storage tank 1 is connected to the inlet end of the first regulating valve 26 through the first LNG pipeline 25, and the outlet end of the first regulating valve 26 is connected to the first inlet end of the cold box 2 through the outlet end of the second LNG pipeline 27;

[0083] The first outlet end of the cold box 2 is connected to the first inlet end of the LNG recuperation heat exchanger 3 through the first natural gas pipeline 28;

[0084] The first outlet end of the LNG recuperation heat exchanger 3 is connected to the inlet end of the temperature controller 10 through the second natural gas pipeline 29, and the outlet end of the temperature controller 10 is connected to the natural gas pipeline network 11 through the second connecting pipe 30;

[0085] The first LNG pipeline 25 , the second LNG pipeline 27 , the first natural gas pipeline 28 , and the second natural gas pipeline 29 are all provided with a second ball valve 33 .

[0086] By providing the second ball valve 33 on the second LNG pipeline 27 and the first natural gas pipeline 28, the heating time of this part of LNG in the cold box 2 can be controlled, so that the LNG heating effect can be more controllable.

[0087] The temperature controller 10 is an air vaporizer or a seawater heater. When the cold box 2 and the LNG recuperation heat exchanger 3 are damaged, the temperature controller 10 can be turned on to heat them.

[0088] According to one embodiment of the present invention, the cold energy step-by-step utilization system further includes a first temperature meter 31;

[0089] The first thermometer 31 is disposed on the first natural gas pipeline 28 , and the first thermometer 31 and the first regulating valve 26 are both electrically connected to the controller;

[0090] The second connecting pipe 30 and the second natural gas pipeline 29 are both provided with a second thermometer 34 .

[0091] It should be noted that when the temperature of the LNG displayed by the first thermometer 31 is too low, the first thermometer 31 sends a signal to the controller, and the controller reduces the opening of the first regulating valve 26, thereby reducing the amount of LNG entering the cold box 2 for heat exchange. Under the same refrigerant temperature, the smaller the flow rate of LNG in the cold box 2, the higher the temperature of the LNG after heat exchange in the cold box 2.

[0092] It should be noted that the natural gas pipeline network 11 is the urban natural gas pipeline network outside the natural gas peak-shaving station, the refrigerant pipeline network 12 is the user-end refrigerant pipeline network outside the natural gas peak-shaving station, the circulating water pipeline network 15 is the whole plant circulating water within the natural gas peak-shaving station, the air-conditioning water pipeline network 13 is the user-end life air-conditioning water pipeline network outside the natural gas peak-shaving station, and the purified water pipeline network 14 is the municipal purified water pipeline network.

[0093] The second heat exchanger 7 , the first heat exchanger 6 , the LNG recuperation heat exchanger 3 , the LNG storage tank 1 , the refrigerant buffer tank 4 , the water tank 8 and the temperature controller 10 are all connected to the cold energy cascade utilization system in the entire natural gas pressure regulating station through the flange 37 .

[0094] The first inlet end to the first outlet end of the cold box 2 is a heat exchange pipeline, and the second inlet end to the second outlet end is another heat exchange pipeline. The structural principles of the first heat exchanger 6, the second heat exchanger 7 and the LNG recuperation heat exchanger 3 are the same as those of the cold box 2 and will not be elaborated herein.

[0095] Embodiment 2:

[0096] A method for stepwise utilization of cold energy in a natural gas pressure regulating station comprises the following steps:

[0097] S1: Open all the first ball valves 32, the second ball valves 33, the first three-way valves 16, the second three-way valves 22 and the first regulating valve 26, and the sub-refrigerant delivery system inputs hot gaseous refrigerant into the cold box 2. The LNG in the LNG storage tank 1 passes through the cold box 2 and performs the first heat exchange with the hot gaseous refrigerant in the cold box 2. The liquefied natural gas is converted from liquid phase to gas phase and then enters the LNG recuperation heat exchanger 3;

[0098] S2: LNG continues to be heated up for a second time in the LNG recuperation heat exchanger 3 until the temperature measured by the second thermometer 34 located on the second connecting pipe 30 reaches a predetermined temperature and then enters the natural gas pipeline network 11;

[0099] The refrigerant in the cold box 2 is transported to the refrigerant buffer tank 4. The gaseous propane at the top of the refrigerant buffer tank 4 is discharged from the gas outlet of the refrigerant buffer tank 4, passes through the refrigerant gas pipeline 36 and merges with the hot gaseous refrigerant in the LNG recuperation heat exchanger 3 after releasing the cold energy, and returns to the cold box 2 to exchange heat with the LNG.

[0100] After the liquid refrigerant at the bottom of the refrigerant buffer tank 4 is transported to the first three-way valve 16 by the booster pump 5, it is divided into two paths: one path is transported to the refrigerant network 12 through the first outlet end of the first three-way valve 16 and the second refrigerant pipe 18; the other path is transported to the refrigerant network 12 through the second outlet end of the first three-way valve 16 and the first heat exchanger 6 and the second heat exchanger 7 respectively, and then heat-exchanged with the high-temperature air-conditioning water in the high-temperature air-conditioning water pipeline and the high-temperature circulating water in the high-temperature circulating water pipeline 23, and then heated and transported to the LNG reheat exchanger 3 to continue to exchange heat with LNG.

[0101] According to one embodiment of the present invention, in step S1, when the first thermometer 31 detects that the temperature of LNG passing through the first natural gas pipeline 28 is too low after heat exchange in the cold box 2, the flow rate of LNG passing through the cold box 2 is reduced by reducing the opening of the first regulating valve 26.

[0102] According to one embodiment of the present invention, in step S2, when the air conditioning water loss in the high-temperature air conditioning water pipeline is large, the second three-way valve 22 is adjusted to replenish purified water to the high-temperature air conditioning water pipeline through the purified water pipeline network 14.

[0103] Furthermore, in the natural gas pressure regulating station, LNG is used to implement gas peak regulation during the peak gas consumption period. The flow of LNG from the LNG storage tank 1 is controlled by the first ball valve 32. After the first ball valve 32 is adjusted, the pressure is 0.6MPa(g) and the temperature is -160°C. The LNG enters the cold box 2 for heat exchange with the refrigerant. After the heat exchange, the LNG absorbs heat and undergoes a phase change, from liquid phase to gas phase. The temperature is exchanged to -40°C and the pressure is 0.58MPa(g). The gas phase natural gas is then sent to the LNG recuperation heat exchanger 3 for heat exchange with the reheated hot refrigerant to 5°C and a pressure of 0.38MPa(g). The reheated natural gas is further heated by the temperature controller 10 and sent to the urban natural gas pipeline network.

[0104] Propane is used as the refrigerant for the cascade utilization of cold energy. The hot gaseous refrigerant after the refrigerant network 12 releases the cold energy is -20℃ and the pressure is 0.144MPa(g). It enters the cold box 2 through the sub-refrigerant transportation system to exchange heat with LNG. After the heat exchange, the hot gaseous refrigerant absorbs cold and undergoes a phase change, condensing from gas to liquid. The temperature of the cold liquid refrigerant is -35℃ and the pressure is 0.04MPa(g). The cooled refrigerant propane is sent to the refrigerant buffer tank 4. The gaseous propane at the top of the refrigerant buffer tank 4 and the hot gaseous refrigerant after the cold energy is released are combined. It returns to the cold box 2 through the refrigerant gas pipeline 36 to exchange heat with LNG. The liquid propane at the bottom of the refrigerant buffer tank 4 is pressurized to 0.8MPa(g) by the booster pump 5 and then divided into two paths. One path of cooled refrigerant liquid propane is directly sent to the refrigerant pipeline 12, and heat is exchanged in the refrigerant pipeline network at the user end outside the station. The refrigerant releases cold energy and is converted from cold liquid to hot gas. The hot gas refrigerant after releasing the cold energy returns to the cold box 2 to exchange heat with LNG, completing a cycle of refrigerant cold energy absorption-refrigerant transportation-refrigerant cold energy release-refrigerant gas return.

[0105] The other cooled refrigerant liquid propane is sent to the first heat exchanger 6, and the refrigerant liquid flow rate is controlled according to the cold amount of the air conditioning water pipe network 13. The cooled refrigerant liquid propane exchanges heat with the high-temperature air conditioning water pipe in the first heat exchanger 6, and the hot gaseous refrigerant propane with a pressure of 0.35MPa(g) after releasing the cold energy enters the second heat exchanger 7 to continue heat exchange to 15°C, and then exchanges heat with natural gas to -28°C in the LNG recuperation heat exchanger 3, and then merges with the hot gaseous refrigerant after releasing the cold energy and returns to the cold box 2 to exchange heat with LNG, completing a cycle of refrigerant cold energy absorption-refrigerant cold energy release-refrigerant gas return.

[0106] The high-temperature circulating water that exchanges heat with the refrigerant in the second heat exchanger 7 uses the whole plant's circulating water (circulating water network 15) as return water. The high-temperature circulating water in the high-temperature circulating water pipeline 23 is cooled to a reasonable temperature by the coldness of the refrigerant and then returned to the circulating water network 15 through the low-temperature circulating water pipeline 24, saving energy consumption of the circulating water network 15. The cooling amount of the circulating water return is controlled according to the reheating temperature of the refrigerant.

[0107] Among them, the high-temperature air-conditioning water after releasing the cold energy in the air-conditioning water network 13 exchanges heat with the cold liquid refrigerant propane in the first heat exchanger 6, and the air-conditioning water is cooled to 15°C. The cooled air-conditioning water is sent to the air-conditioning water network 13 for cooling air-conditioning for life, and enters the air-conditioning water network 13 through the low-temperature air-conditioning water pipeline 20 to release the cold energy for air-conditioning refrigeration. The high-temperature air-conditioning water after releasing the cold energy returns to the water tank 8 in the factory area. The high-temperature air-conditioning water at the bottom of the water tank 8 is pressurized to 0.6MPa(g) by the water pump 35 and then sent to the first heat exchanger 6, completing a cycle. The high-temperature chilled water (air-conditioning water) can be supplemented with the high-temperature chilled water of the air-conditioning water network 13 through the purified water in the purified water network 14.

[0108] In the description of the present invention, it should be noted that the terms "upper", "lower", etc., indicating the 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 that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0109] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be a connection between the inside of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, in the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0110] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A cold energy step utilization system in a natural gas pressure regulating station, characterized in that: It comprises an LNG storage tank (1), a cold box (2), an LNG recuperation heat exchanger (3), a sub-high-temperature water supply system, a sub-refrigerant delivery system, a natural gas pipeline network (11), a sub-low-temperature water return system and a sub-refrigerant recuperation system; The outlet end of the LNG storage tank (1) is connected to the first inlet end of the cold box (2), the first outlet end of the cold box (2) is connected to the first inlet end of the LNG recuperation heat exchanger (3), and the first outlet end of the LNG recuperation heat exchanger (3) is connected to the natural gas pipeline network (11); The inlet end of the sub-refrigerant recovery system is connected to the second outlet end of the cold box (2), the outlet end of the sub-refrigerant recovery system is connected to the second inlet end of the LNG recovery heat exchanger (3), and the second outlet end of the LNG recovery heat exchanger (3) and the outlet end of the sub-refrigerant delivery system are both connected to the second inlet end of the cold box (2); The high-temperature water of the sub-high-temperature water supply system is transported to the sub-low-temperature return water system after heat exchange through the sub-refrigerant reheating system. The sub-low-temperature return water system is used to transport the low-temperature water formed after heat exchange of the high-temperature water to the sub-high-temperature water supply system.

2. A system for stepwise utilization of cold energy in a natural gas pressure regulating station according to claim 1, characterized in that: The sub-refrigerant delivery system comprises a refrigerant pipe network (12) and a second refrigerant pipe (18); The sub-refrigerant reheating system includes a refrigerant transport device, the second outlet end of the cold box (2) is connected to the inlet end of the second refrigerant pipe (18) through the refrigerant transport device, the outlet end of the second refrigerant pipe (18) is connected to the refrigerant pipe network (12), and the refrigerant pipe network (12) is connected to the second inlet end of the cold box (2).

3. A cold energy step utilization system in a natural gas pressure regulating station according to claim 2, characterized in that: The sub-high-temperature water supply system includes a high-temperature air-conditioning water pipeline and an air-conditioning water network (13), the sub-low-temperature water return system includes a low-temperature air-conditioning water pipeline (20), and the sub-refrigerant reheating system also includes a first heat exchanger (6); The refrigerant transport device comprises a refrigerant buffer tank (4), a booster pump (5), and a first three-way valve (16) which are connected in sequence; The inlet end of the refrigerant buffer tank (4) is connected to the second outlet end of the cold box (2) through a first refrigerant pipe (17); The refrigerant buffer tank (4) has a gas outlet end, and the gas outlet end is connected to the second inlet end of the cold box (2) through a refrigerant gas pipeline (36); The first outlet end of the first three-way valve (16) is connected to the inlet end of the second refrigerant pipe (18), the second outlet end of the first three-way valve (16) is connected to the first inlet end of the first heat exchanger (6) through the third refrigerant pipe (19), and the first outlet end of the first heat exchanger (6) is connected to the second inlet end of the LNG recuperation heat exchanger (3); The outlet end of the high-temperature air-conditioning water pipeline is connected to the second inlet end of the first heat exchanger (6), and the second outlet end of the first heat exchanger (6) is connected to the low-temperature air-conditioning water pipeline (20); The outlet end of the low-temperature air-conditioning water pipeline (20) and the inlet end of the high-temperature air-conditioning water pipeline are both connected to the air-conditioning water pipeline network (13); The first refrigerant pipe (17), the second refrigerant pipe (18) and the third refrigerant pipe (19) are all provided with a first ball valve (32).

4. A system for stepwise utilization of cold energy in a natural gas pressure regulating station according to claim 3, characterized in that: The high-temperature air-conditioning water pipeline comprises a first air-conditioning water pipeline (21), a water tank (8), a water pump (35) and a second three-way valve (22); The inlet end of the first air-conditioning water pipe (21) is connected to the outlet end of the water tank (8), and the outlet end thereof is connected to the inlet end of the water pump (35), and the outlet end of the water pump (35) is connected to the first inlet end of the second three-way valve (22); The second inlet end of the second three-way valve (22) is connected to the purified water pipe network (14), and the outlet end thereof is connected to the second inlet end of the first heat exchanger (6).

5. A system for stepwise utilization of cold energy in a natural gas pressure regulating station according to claim 4, characterized in that: The sub-refrigerant reheating system further includes a second heat exchanger (7), the sub-high-temperature water supply system further includes a circulating water network (15) and a high-temperature circulating water pipeline (23), and the sub-low-temperature water return system further includes a low-temperature circulating water pipeline (24); The first outlet end of the first heat exchanger (6) is connected to the first inlet end of the second heat exchanger (7), and the first outlet end of the second heat exchanger (7) is connected to the second inlet end of the LNG recuperation heat exchanger (3); The inlet end of the high-temperature circulating water pipeline (23) and the outlet end of the low-temperature circulating water pipeline (24) are both connected to the circulating water network (15); The outlet end of the high-temperature circulating water pipeline (23) is connected to the second inlet end of the second heat exchanger (7), and the inlet end of the low-temperature circulating water pipeline (24) is connected to the second outlet end of the second heat exchanger (7).

6. The cold energy step utilization system in a natural gas pressure regulating station according to claim 1 is characterized in that: The cold energy step-by-step utilization system further comprises a first LNG pipeline (25), a second LNG pipeline (27), a first natural gas pipeline (28), a second natural gas pipeline (29), a first regulating valve (26) and a temperature controller (10); The outlet end of the LNG storage tank (1) is connected to the inlet end of the first regulating valve (26) through the first LNG pipeline (25), and the outlet end of the first regulating valve (26) is connected to the first inlet end of the cold box (2) through the outlet end of the second LNG pipeline (27); The first outlet end of the cold box (2) is connected to the first inlet end of the LNG recuperation heat exchanger (3) through the first natural gas pipeline (28); The first outlet end of the LNG recuperation heat exchanger (3) is connected to the inlet end of the temperature controller (10) through the second natural gas pipeline (29), and the outlet end of the temperature controller (10) is connected to the natural gas pipeline network (11) through a second connecting pipe (30); The first LNG pipeline (25), the second LNG pipeline (27), the first natural gas pipeline (28), and the second natural gas pipeline (29) are all provided with a second ball valve (33).

7. A system for stepwise utilization of cold energy in a natural gas pressure regulating station according to claim 6, characterized in that: The cold energy step-by-step utilization system further includes a first temperature meter (31) and a controller; The first temperature meter (31) is arranged on the first natural gas pipeline (28), and the first temperature meter (31) and the first regulating valve (26) are both electrically connected to the controller; The second connecting pipe (30) and the second natural gas pipeline (29) are both provided with a second thermometer (34).

8. A method for stepwise utilization of cold energy in a natural gas pressure regulating station, characterized in that: The following steps are involved: S1: All the first ball valves (32), the second ball valves (33), the first three-way valves (16), the second three-way valves (22) and the first regulating valve (26) are opened, and the sub-refrigerant delivery system inputs hot gaseous refrigerant into the cold box (2), and the LNG in the LNG storage tank (1) passes through the cold box (2) and performs the first heat exchange with the hot gaseous refrigerant in the cold box (2), and the liquefied natural gas is converted from liquid phase to gas phase and then enters the LNG reheating heat exchanger (3); S2: the LNG continues to be heated for a second time in the LNG recuperation heat exchanger (3) until the temperature measured by the second temperature gauge (34) located on the second connecting pipe (30) reaches a predetermined temperature and then enters the natural gas pipeline network (11); The refrigerant in the cold box (2) is transported to the refrigerant buffer tank (4), the gaseous refrigerant at the top of the refrigerant buffer tank (4) is discharged from the gas outlet of the refrigerant buffer tank (4), passes through the refrigerant gas pipeline (36) and merges with the hot gaseous refrigerant in the LNG recuperation heat exchanger (3) after releasing the cold energy, and returns to the cold box (2) to exchange heat with the LNG; After the liquid refrigerant at the bottom of the refrigerant buffer tank (4) is transported to the first three-way valve (16) by the booster pump (5), it is divided into two paths: one path is transported to the refrigerant network (12) through the first outlet end of the first three-way valve (16) and the second refrigerant pipe (18); the other path is transported to the refrigerant network (12) through the second outlet end of the first three-way valve (16) and the first heat exchanger (6) and the second heat exchanger (7) respectively, and then heat-exchanged with the high-temperature air-conditioning water in the high-temperature air-conditioning water pipeline and the high-temperature circulating water in the high-temperature circulating water pipeline (23) to be heated and transported to the LNG reheat exchanger (3) to continue to exchange heat with LNG.

9. A method for stepwise utilization of cold energy in a natural gas pressure regulating station according to claim 8, characterized in that: In step S1, when the first thermometer (31) detects that the temperature of the LNG passing through the first natural gas pipeline (28) is too low after heat exchange in the cold box (2), the flow rate of the LNG passing through the cold box (2) is reduced by reducing the opening of the first regulating valve (26).

10. A method for stepwise utilization of cold energy in a natural gas pressure regulating station according to claim 8, characterized in that: In step S2, when the loss of air-conditioning water in the high-temperature air-conditioning water pipeline is large, the second three-way valve (22) is adjusted to replenish purified water to the high-temperature air-conditioning water pipeline through the purified water pipeline network (14).

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