Liquefied gas cold energy utilization system and method

Abstract

The invention provides a liquefied gas cold energy utilization system and method. The system comprises a liquefied gas storage device, a first pressure reducing valve, a gas-liquid separation device, a first-stage heat exchange device and a conveying header pipe. Liquid liquefied gas in the liquefied gas storage device is depressurized through a first depressurizing valve to realize partial flash evaporation; the gas-liquid separation device separates gaseous liquefied gas from liquid liquefied gas, and the gaseous liquefied gas directly enters the main pipe; liquid liquefied gas enters the first-stage heat exchange device, exchanges heat with a heat exchange medium and then is gasified to enter a main pipe; the main pipe converges gaseous liquefied gas and then conveys the gas liquefied gas to combustion equipment. Partial flash evaporation is achieved by controlling the pressure reduction process, stable gas supply of combustion equipment can be guaranteed while liquefied gas phase change heat absorption refrigeration is utilized, gradient utilization of energy is achieved, and the device is suitable for application scenes such as motor homes and long-distance trucks with liquefied gas as fuel.

Description

TECHNICAL FIELD

[0001] The present application relates to liquefied gas cold energy recovery, in particular to a liquefied gas cold energy utilization system and method. BACKGROUND

[0002] Liquefied petroleum gas (LPG) is a commonly used clean energy, and its core components are propane and butane, which can be stored in special steel cylinders at room temperature. When LPG gasifies, it will absorb environmental heat, and propane and butane can be used as refrigerants. However, existing bottled LPG is usually used as fuel, and there is no perfect cold energy recovery solution.

[0003] Existing cold energy recovery and utilization systems are usually designed around liquefied natural gas (LNG) (such as the solutions disclosed in patents CN114651148A, CN117190625A, and CN102967099A). The core component of LNG is methane, which usually needs to be cooled to -162℃ to form an ultralow-temperature liquid for transportation and is stored in a vacuum insulated tank. LNG is mainly used for energy supply in industrial scenarios such as ships and large storage tanks. The existing cold energy utilization system directly exchanges heat between low-temperature LNG and a cooling medium, so it relies on an ultralow-temperature environment and large insulation equipment, which is bulky and costly, and cannot be applied to small scenarios such as recreational vehicles and long-distance trucks that use liquefied gas as a power source.

[0004] Therefore, how to design a fuel supply and cold energy recovery integrated system suitable for small scenarios based on the characteristics of liquefied petroleum gas has become a problem to be solved. SUMMARY

[0005] The purpose of the present application is to provide a liquefied gas cold energy utilization system and method that is suitable for small scenarios and can ensure fuel supply and achieve cold energy recovery and utilization.

[0006] To achieve the above purpose, the technical solution adopted by the present application is as follows: a liquefied gas cold energy utilization system, comprising: a liquefied gas storage device, the internal pressure of which is maintained at 0.5-1.2 MPa, and the bottom of the liquefied gas storage device is provided with a liquid outlet; a first pressure reducing valve, the input end of which is connected to the liquid outlet of the liquefied gas storage device, for reducing the pressure of the liquefied gas to 0.2-0.45 MPa and flashing part of the liquefied gas; a gas-liquid separation device, the input end of which is connected to the output end of the first pressure reducing valve, the gas-liquid separation device is provided with a first gas phase outlet and a first liquid phase outlet, the first gas phase outlet is connected to a delivery main pipe, and the first liquid phase outlet is connected to a primary heat exchange device; The primary heat exchange device comprises a first medium pipeline for flowing through a heat exchange medium and a first liquefied gas pipeline for flowing through liquefied gas, a first heat exchange structure is arranged between the first medium pipeline and the first liquefied gas pipeline, the input end of the first liquefied gas pipeline is connected with the first liquid phase outlet of the gas-liquid separation device, and the output end of the first liquefied gas pipeline is communicated with the delivery main pipe; The delivery main pipe is connected to the first gas phase outlet of the gas-liquid separation device at one end and connected to the combustion equipment at the other end, and is used for converging the gaseous liquefied gas output by the gas-liquid separation device and the gaseous liquefied gas output by the primary heat exchange device, and delivering the converged gaseous liquefied gas to the combustion equipment.

[0007] In the above scheme, the "liquefied gas" refers to liquefied petroleum gas (LPG), and the core components are propane (R290) and butane (R600). Because propane and butane have the phase change characteristics of being easily pressurized and liquefied at room temperature, and the volume is greatly reduced after liquefaction, the pressure in the storage device (such as a steel cylinder) can be maintained at 0.5-1.2 MPa at room temperature environment, realizing high-density liquid storage, without the need for additional low-temperature refrigeration equipment, and adapting to the storage needs of house cars, long-distance trucks and other scenes.

[0008] The outlet of the existing liquefied gas cylinder is usually arranged at the top, and the liquefied gas is discharged under the action of pressure. During the discharge process, the liquefied gas will be naturally gasified due to the decrease of pressure, and thus can be used for combustion equipment such as a stove. The gasification in this process absorbs heat, but because the gasification process is dispersed, this part of cold energy is difficult to be effectively utilized.

[0009] In the present scheme, the liquid outlet is arranged at the bottom of the liquefied gas storage device, so that as long as there is still not completely gasified liquid liquefied gas in the storage device, the medium discharged from the bottom liquid outlet can be stably maintained in a liquid state.

[0010] The first pressure reducing valve is used to reduce the pressure from 0.5-1.2 MPa in the storage device to 0.2-0.45 MPa, so that the saturation temperature of propane and butane is reduced, and part of the liquefied gas absorbs heat and becomes a gas, which is a partial "flash evaporation". After flash evaporation, the liquefied gas forms a gas-liquid mixed state.

[0011] The partial flash evaporation has two effects, one is to reduce the temperature of the liquefied gas for the subsequent heat exchange, and the other is to ensure that a certain proportion of liquefied gas is continuously input to the combustion equipment to ensure stable combustion gas supply and reduce the influence of fluctuations in the primary heat exchange device.

[0012] The gas-liquid separation device is used to separate the liquefied gas in the gas-liquid mixed state to prevent liquid liquefied gas from entering the combustion equipment. The pressure inside the gas-liquid separation device is consistent with the outlet pressure of the first pressure reducing valve, and is also maintained at 0.2-0.45 MPa to control the flash evaporation ratio and ensure that most of the liquefied gas remains in a liquid state.

[0013] Due to the flash evaporation heat absorption, the temperature of the liquid liquefied gas in the gas-liquid separation device will be significantly reduced compared to the initial temperature. When the pressure decreases from 0.5 MPa to 0.2 MPa, the temperature decreases by about 20℃ to 25℃.

[0014] The liquid liquefied gas enters the subsequent primary heat exchange device and exchanges heat with the heat exchange medium to realize refrigeration. The heat exchange process includes both liquid temperature rise heat absorption and gasification heat absorption. The heat exchange medium can be water, air, etc. The primary heat exchange device can be integrated into the interior of a refrigerator, air conditioner, etc. At the same time, during the heat exchange process, the liquefied gas absorbs heat and gasifies, and then enters the delivery main pipe to be delivered to the combustion equipment together with the gaseous liquefied gas obtained by flash evaporation, thereby realizing both combustion gas supply and cold energy utilization.

[0015] In a further technical solution, the gas-liquid separation device is a horizontally placed cylindrical structure with a length-diameter ratio of 3-5, the first gas phase outlet is arranged at the top, the first liquid phase outlet is arranged at the bottom, and a liquid droplet isolation net is arranged at the first gas phase outlet to ensure that liquefied gas droplets do not enter the gaseous pipeline and prevent liquid liquefied gas from entering the combustion equipment to cause safety hazards. In order to avoid excessive flash evaporation and reduce cold energy loss, a thermal insulation layer is arranged on the outer wall of the gas-liquid separation device.

[0016] In a further technical solution, the first liquefied gas pipeline of the primary heat exchange device is a horizontally arranged gradually expanding tube bundle, the tube diameter ratio of the rear end to the front end of the first liquefied gas pipeline is 1.5:1, and the first heat exchange structure is an aluminum fin covering the first liquefied gas pipeline. Since the liquid liquefied gas will gradually gasify after heat absorption, gradually expanding the tube diameter can ensure that the pressure in the pipeline is stable and the flow rate is maintained within a reasonable range, avoiding impact on the delivery main pipe.

[0017] In a further technical solution, the system further comprises an intermediate separator, the output end of the first liquefied gas pipeline is connected to the input end of the intermediate separator, the intermediate separator is provided with a second gas phase outlet and a second liquid phase outlet, the second gas phase outlet is connected to the delivery main pipe, and the first liquefied gas pipeline communicates with the delivery main pipe through the second gas phase outlet of the intermediate separator. When the liquefied gas flow is large, the primary heat exchange device may not be able to gasify all the liquid liquefied gas, so the intermediate separator is arranged to separate the liquid and gaseous liquefied gas, ensuring that only gaseous liquefied gas enters the delivery main pipe.

[0018] Further technical solutions, the intermediate separator is a vertically placed cylindrical structure, the length-diameter ratio is 1-2, the second gas phase outlet is arranged at the top, the second liquid phase outlet is arranged at the bottom, the input end is arranged at the middle along the tangent direction, the second gas phase outlet is provided with a liquid droplet isolation net, and the outer wall of the intermediate separator is provided with a heat preservation layer. Since the output liquefied gas of the primary heat exchange device can be in a gas-liquid mixed state, the vertically arranged intermediate separator can separate the liquid and gaseous liquefied gas by using gravity. The heat preservation layer can prevent the liquid liquefied gas from further gasification in the intermediate separator by absorbing heat, thereby wasting cold energy.

[0019] Further technical solutions, the system further comprises: A second pressure reducing valve, the input end of which is connected with the second liquid phase outlet of the intermediate separator, for reducing the pressure of the liquefied gas to 0.1-0.2 MPa and promoting partial liquefied gas to flash evaporation; A secondary heat exchange device, comprising a second medium pipeline for circulating a heat exchange medium and a second liquefied gas pipeline for circulating liquefied gas, a second heat exchange structure being arranged between the second medium pipeline and the second liquefied gas pipeline, the input end of the second liquefied gas pipeline being connected with the output end of the second pressure reducing valve, and the output end being connected to the delivery main pipe.

[0020] By arranging the second pressure reducing valve and the secondary heat exchange device, the second partial flash evaporation can be carried out, and the liquefied gas that has not been gasified can be fully utilized, which is suitable for the case that the gas consumption of the combustion equipment is large, for example, a long-distance truck using liquefied gas as a power energy source, and the engine is used as a combustion equipment, and the liquefied gas needs to be continuously used. In this scenario, the liquefied gas consumption is large, and by using the primary heat exchange device and the secondary heat exchange device for staged pressure reduction and refrigeration, the cold energy of the liquefied gas can be fully utilized.

[0021] Further technical solutions, the second liquefied gas pipeline of the secondary heat exchange device comprises a plurality of branch pipes, the second heat exchange structure comprises heat exchange plates and corrugated fins, the corrugated fins are attached to the upper and lower surfaces of the heat exchange plates, the plurality of branch pipes pass through the inside of the heat exchange plates and form continuous flow channels, the input ends of the plurality of branch pipes are connected to the output end of the second pressure reducing valve, and the output ends are connected to the delivery main pipe after being connected in series. The ratio of the total pipe diameter of the plurality of branch pipes to the pipe diameter of the front end inlet is 2:1, and the heat exchange area of the second heat exchange structure is 2-4 m 2 .

[0022] In order to fully gasify the liquid liquefied gas, the secondary heat exchange device needs to be fully heat exchanged, so that as much liquefied gas as possible can be gasified by the structure of the heat exchange plates and the corrugated fins. Since the volume expands after gasification, the ratio of the total pipe diameter to the pipe diameter of the front end inlet is designed to be 2:1, so that the gas pressure in the pipe remains stable.

[0023] Further technical solutions, the system further comprises: The first nozzle pressure expansion device is connected to the intersection of the first gas phase outlet of the gas-liquid separation device, the second gas phase outlet of the intermediate separator and the delivery main pipe, and is used for stabilizing the pressure of the plurality of gas media after being merged. The second nozzle pressure expansion device is connected to the intersection of the second liquefied gas pipeline output end of the secondary heat exchange device and the delivery main pipe, and is used for increasing the pressure of the gaseous liquefied gas after the secondary heat exchange to the pressure adapted to the delivery main pipe.

[0024] Further technical solutions, the system further comprises a gas storage tank, the gas storage tank is connected between the delivery main pipe and the combustion equipment, the gas storage tank is provided with a pressure relief valve, and the opening pressure of the pressure relief valve is 0.6-0.8 MPa. By arranging the gas storage tank, the pressure and flow of the gaseous liquefied gas entering the combustion equipment can be ensured to be stable, and problems such as large and small combustion flame and flameout caused by gas fluctuation can be avoided, so that the operation stability of the combustion equipment is ensured. In addition, the gas storage tank can also mix the liquefied gas uniformly. Since the saturated vapor pressure of propane is higher than that of butane, the gas flashed out for the first time is mainly propane, and the gaseous output by the primary heat exchange device and the secondary heat exchange device is gradually increased. The liquefied gas can be fully mixed and uniform after entering the gas storage tank, which is beneficial to full combustion.

[0025] According to another aspect of the present application, a liquefied gas cold energy utilization method is also provided, comprising the following steps: S1: liquefied gas storage, storing the liquefied gas in a liquefied gas storage device with an internal pressure maintained at 0.5-1.2 MPa, and the bottom of the liquefied gas storage device is provided with a liquid outlet; S2: primary pressure reduction flash evaporation, reducing the pressure of the liquid liquefied gas output from the liquid outlet of the liquefied gas storage device to 0.2-0.45 MPa through a first pressure reduction valve, so as to cause part of the liquid liquefied gas to flash evaporate into gaseous state; S3: primary gas-liquid separation, introducing the gas-liquid mixed liquefied gas treated in step S2 into a gas-liquid separation device to separate the first gaseous liquefied gas and the first liquid liquefied gas, and the first gaseous liquefied gas is delivered to the delivery main pipe through the first gas phase outlet of the gas-liquid separation device; S4: primary heat exchange and cold energy extraction, introducing the first liquid liquefied gas separated in step S3 into the first liquefied gas pipeline of the primary heat exchange device, so that the first liquid liquefied gas exchanges heat with the heat exchange medium flowing in the first medium pipeline of the primary heat exchange device, and the first liquid liquefied gas gasifies to form the second gaseous liquefied gas after absorbing heat, and the second gaseous liquefied gas is delivered to the delivery main pipe through the first liquefied gas pipeline output end; S5: gaseous delivery and combustion, merging the first gaseous liquefied gas of step S3 and the second gaseous liquefied gas of step S4 through the delivery main pipe, and delivering the merged gaseous liquefied gas to the combustion equipment for combustion.

[0026] Further technical solutions, between step S4 and step S5, further comprising the following steps: S41: intermediate separation, the second gaseous liquefied gas (containing residual liquid liquefied gas that has not completely gasified) output by the first liquefied gas pipeline in step S4 is introduced into an intermediate separator to separate third gaseous liquefied gas and second liquid liquefied gas, and the third gaseous liquefied gas is transported to the delivery header through the second gas phase outlet of the intermediate separator; S42: secondary pressure reduction flash evaporation, the second liquid liquefied gas separated in step S41 is subjected to pressure reduction to 0.1-0.2 MPa through a second pressure reduction valve to cause part of the second liquid liquefied gas to flash evaporate into a gaseous state; S43: secondary heat exchange for cooling, the gas-liquid mixed liquefied gas after step S42 is introduced into the second liquefied gas pipeline of the secondary heat exchange device to cause the gas-liquid mixed liquefied gas to exchange heat with the heat exchange medium flowing in the second medium pipeline of the secondary heat exchange device, and the liquid liquefied gas that has not flash evaporated absorbs heat to completely gasify into fourth gaseous liquefied gas, which is transported to the delivery header through the output end of the second liquefied gas pipeline, and is delivered to the combustion equipment after being combined with the first gaseous liquefied gas and the third gaseous liquefied gas.

[0027] Further technical solutions, when the first gaseous liquefied gas is delivered to the delivery header in step S3 and the third gaseous liquefied gas is delivered to the delivery header in step S41, further comprising: the combined gas flow of the first gaseous liquefied gas and the third gaseous liquefied gas is subjected to pressure stabilization through a first nozzle pressure expansion device to maintain the pressure of the combined gas flow at 0.2-0.45 MPa; when the fourth gaseous liquefied gas is delivered to the delivery header in step S43, the pressure of the fourth gaseous liquefied gas is increased to 0.2-0.45 MPa through a second nozzle pressure expansion device to ensure that the pressure of all gaseous liquefied gas in the delivery header is consistent before being delivered to the combustion equipment; and before the gaseous liquefied gas is delivered to the combustion equipment, it is first introduced into a gas storage tank connected in series between the delivery header and the combustion equipment for temporary storage, and when the pressure in the gas storage tank exceeds 0.6-0.8 MPa, a pressure relief valve on the gas storage tank automatically opens to release pressure.

[0028] The working principle and beneficial effects of the technical solutions provided in the present application are as follows: The liquefied petroleum gas is stored in a storage device in a liquid state at 0.5-1.2 MPa, is discharged from the bottom, is subjected to pressure reduction to 0.2-0.45 MPa through a primary pressure reduction valve to realize partial flash evaporation, and the obtained gas-liquid mixture is separated into a gaseous state and a liquid state in a separation device; the gaseous liquefied gas is input into a header to ensure stable combustion of the combustion equipment, and the liquid liquefied gas is gasified after absorbing heat in a primary heat exchange device and is then combined into the header to realize utilization of cold energy. The device realizes partial flash evaporation through control of the pressure reduction process, can ensure stable gas supply of the combustion equipment while utilizing the phase change heat absorption refrigeration of the liquefied gas, realizes gradient utilization of energy, and is suitable for application scenarios such as motor homes and long-distance trucks. Attached Figure Description

[0029] Appendix Figure 1 This is a system structure diagram of Embodiment 1 of the present invention; Appendix Figure 2 This is a cross-sectional view of the gas-liquid separation device in Embodiment 1 of the present invention; Appendix Figure 3 This is a system structure diagram of Embodiment 2 of the present invention; Appendix Figure 4 This is a cross-sectional view of the intermediate separator in Embodiment 2 of the present invention; Appendix Figure 5 This is a cross-sectional view of the primary heat exchange device according to Embodiment 1 of the present invention; Appendix Figure 6 This is a system structure diagram of Embodiment 3 of the present invention; Appendix Figure 7 This is a system structure diagram of Embodiment 4 of the present invention; Appendix Figure 8 This is a top view of the two-stage heat exchange device in Embodiment 4 of the present invention; Appendix Figure 9 For the appendix Figure 8 Cross-sectional view of the secondary heat exchanger; Appendix Figure 10 This is a system structure diagram of Embodiment 5 of the present invention; In the attached diagrams: 1. Liquefied petroleum gas (LPG) storage device; 101. Liquid outlet pipe; 2. First pressure reducing valve; 3. Gas-liquid separation device; 31. First gas phase outlet; 32. First liquid phase outlet; 33. Baffle plate; 4. Primary heat exchanger; 41. First medium pipeline; 42. First LPG pipeline; 43. First heat exchange structure; 431. Aluminum fins; 5. Main delivery pipe; 6. Combustion equipment; 7. Intermediate separator; 72. Second gas phase outlet; 74. Second liquid phase outlet; 8. Second pressure reducing valve; 9. Second heat exchanger; 91. Second medium pipeline; 92. Second LPG pipeline; 93. Second heat exchange structure; 10. First nozzle diffuser; 11. Second nozzle diffuser; 12. Gas storage tank. Detailed Implementation

[0030] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0031] The terms "first," "second," etc., used in this article do not specifically refer to order or sequence, nor are they intended to limit this case; they are merely used to distinguish components or operations described using the same technical terms.

[0032] As used herein, the terms "connected" or "coupled" are used broadly and encompass both direct and indirect coupling or connection, and are intended to include interconnection between two members that are coupled together or interconnection between two members that are not so coupled together, unless otherwise specifically stated.

[0033] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having" or the like are open-ended terms that are intended to mean including, but not limited to.

[0034] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having" or the like are open-ended terms that are intended to mean including, but not limited to.

[0035] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having" or the like are open-ended terms that are intended to mean including, but not limited to. Embodiment One

[0036] The embodiment provides a liquefied gas cold energy utilization system suitable for a motor home scene, which can simultaneously realize liquefied gas combustion power supply and refrigerator cold storage room refrigeration. Figure 1 As shown in the figure, the system comprises a liquefied gas storage device 1, a first pressure reducing valve 2, a gas-liquid separation device 3, a primary heat exchange device 4, a delivery main pipe 5 and a combustion equipment 6.

[0037] The liquefied gas storage device 1 can adopt a conventional household LPG steel cylinder with a volume of 15L, which is filled with liquefied petroleum gas with a filling amount of 8kg. The pressure control component provided in the steel cylinder is used to stabilize the internal pressure of the liquefied gas storage device 1 at 0.8MPa, which can ensure that the liquefied gas remains in a liquid state at room temperature of 25℃. The bottom of the liquefied gas storage device 1 is connected with a liquid outlet pipe 101, and a manual stop valve is arranged on the liquid outlet pipe 101 to control the output of the liquid liquefied gas.

[0038] The first pressure reducing valve 2 is a pilot-operated pressure reducing valve, the input end of which is sealingly connected with the liquid outlet pipe 101 of the liquefied gas storage device 1 through an oil-resistant rubber pipe, and the output end of which is in communication with the input end of the gas-liquid separation device 3 through a stainless steel pipe. The pressure regulating range of the first pressure reducing valve 2 is set to 0.3MPa, and the pressure of the liquid liquefied gas output from the liquefied gas storage device 1 can be reduced from 0.8MPa to 0.3MPa during operation. Under this pressure drop, part of the liquid liquefied gas will flash into a gaseous state due to the sudden pressure drop, forming a gas-liquid mixed flow. The proportion of the gaseous state after flashing is about 12%, and the proportion of the liquid state is about 88%. The temperature after flashing is reduced to about -14℃.

[0039] As shown in Figure 2 , the gas-liquid separation device 3 is a horizontally placed cylindrical stainless steel container with a diameter of 200 mm, a length of 600 mm, a length-diameter ratio of 3, and a volume of about 18 L. The input end of the gas-liquid separation device 3 is in communication with the output end of the first pressure reducing valve 2; a first gas phase outlet 31 is provided at the top position thereof, and a first liquid phase outlet 32 is provided at the bottom position thereof.

[0040] By designing the gas-liquid separation device 3 as a horizontal container with a large length-diameter ratio, sufficient time can be ensured for the gas-liquid separation. In the present embodiment, a baffle plate 33 is further provided at the top of the inner wall of the gas-liquid separation device 3, which can be staggered in the horizontal direction to prolong the flow path of the gaseous liquefied gas, so that the liquid drops therein have sufficient time to fall, ensuring the effect of gas-liquid separation.

[0041] In possible embodiments, a stainless steel liquid drop isolation net can also be internally provided below the first gas phase outlet 31 to intercept the tiny liquid drops entrained in the gaseous state, avoiding the liquid liquefied gas from entering the delivery main pipe 5.

[0042] The internal pressure of the gas-liquid separation device 3 is consistent with the output pressure of the first pressure reducing valve 2. During operation, the gaseous liquefied gas generated by flashing is collected at the top of the gas-liquid separation device 3 and is output through the first gas phase outlet 31; the liquid liquefied gas that is not flashed is collected in the bottom liquid accumulation area and is output to the primary heat exchange device 4 through the first liquid phase outlet 32.

[0043] Preferably, the outer wall of the gas-liquid separation device 3 can also be wrapped with a heat preservation layer, such as a glass wool roll felt or a polyurethane foaming layer, to maintain the temperature inside, reduce the loss of cold energy, and improve the utilization efficiency of cold energy in the subsequent primary heat exchange device 4. At the same time, the heat preservation layer can also avoid the liquid liquefied gas in the gas-liquid separation device 3 from excessive gasification due to excessive heat absorption.

[0044] The primary heat exchange device 4 can be integrated in the back of the refrigerator compartment, including a first medium pipeline 41, a first liquefied gas pipeline 42, and a first heat exchange structure 43.

[0045] The first medium pipeline 41 can be arranged in the evaporator area of the refrigerator compartment, and the heat exchange medium flowing therein is air. The air is driven to flow through the first heat exchange structure 43 by the refrigerator fan, so as to realize heat exchange.

[0046] The first liquefied gas pipeline 42 is a horizontally arranged tube bundle with gradually increasing pipe diameters, and the specific structure is shown in Figure 5 , wherein the front end 42a has a pipe diameter d1 of 10 mm, and the rear end 42b has a pipe diameter d2 of 15 mm. The input end of the first liquefied gas pipeline 42 is connected with the first liquid phase outlet 32 of the gas-liquid separation device 3, and the output end thereof is in communication with the delivery main pipe 5.

[0047] The first heat exchange structure 43 comprises aluminum fins 431 wrapped around the outer wall of the first liquefied gas pipeline 42. The aluminum fins 431 can expand the heat exchange contact area and improve the heat transfer efficiency. In operation, the liquid liquefied gas output from the gas-liquid separation device 3 has a temperature of about -14°C, flows in the first liquefied gas pipeline 42, and exchanges heat with the air in the first medium pipeline 41. After absorbing the heat of the air, the liquid liquefied gas gradually vaporizes to form gaseous liquefied gas; at the same time, the temperature of the air decreases after heat exchange, realizing refrigeration of the refrigeration compartment, and the gaseous liquefied gas after vaporization is collected into the delivery main pipe 5 through the output end of the first liquefied gas pipeline 42.

[0048] One end of the delivery main pipe 5 is in communication with the first gaseous outlet 31 of the gas-liquid separation device 3 and the output end of the first liquefied gas pipeline 42 of the first heat exchange device 4 through a three-way joint, respectively, and the other end is connected with the air inlet of the combustion equipment 6. The delivery main pipe 5 functions to combine two routes of gaseous liquefied gas, form a stable gaseous flow after combination, and then deliver the gaseous flow to the combustion equipment 6.

[0049] In the embodiment, the combustion equipment 6 is a gas stove installed in a house car, and the combustion equipment 6 can also be a gas water heater, a gas stove, etc.

[0050] The operation process of the embodiment is as follows: The manual stop valve at the bottom of the liquefied gas storage device 1 is opened, the liquid liquefied gas enters the first pressure reducing valve 2 through the liquid outlet pipe 101; the first pressure reducing valve 2 reduces the pressure of the liquefied gas to 0.3 MPa, part of the liquefied gas flashes to gaseous state, and the gas-liquid mixture flows into the gas-liquid separation device 3; the gaseous state separated by the gas-liquid separation device 3 enters the delivery main pipe 5 through the first gaseous outlet 31, and the liquid state enters the first heat exchange device 4 through the first liquid outlet 32; in the first heat exchange device 4, the liquid liquefied gas absorbs heat to vaporize and flows into the delivery main pipe 5, and at the same time, the refrigeration compartment of the refrigerator is cooled; the delivery main pipe 5 combines two routes of gaseous liquefied gas, stably delivers the gaseous liquefied gas to the combustion equipment 6, and burns the gaseous liquefied gas.

[0051] The liquefied gas cold energy utilization system provided in the embodiment is suitable for a scene where the use amount of liquefied gas is not high, for example, can be arranged in the liquefied gas system of a house car, and can simultaneously provide fuel for the refrigerator and the gas stove by fully utilizing the cold energy of the liquefied gas. Embodiment Two

[0052] As shown in Figure 2 , 3 and Figure 4 , the embodiment is additionally provided with an intermediate separator 7, the output end of the first liquefied gas pipeline 42 is connected with the input end 71 of the intermediate separator 7, the intermediate separator 7 is provided with a second gaseous outlet 72 connected with the delivery main pipe 5, and the gaseous-liquid liquefied gas output from the first liquefied gas pipeline 42 is delivered to the delivery main pipe 5 through the second gaseous outlet 72 of the intermediate separator 7.

[0053] The intermediate separator 7 plays a role of buffering and further separation. When the flow of liquefied gas is large, the primary heat exchange device 4 can not be able to gasify all the liquid liquefied gas, so the intermediate separator 7 is arranged to separate the liquid and gaseous liquefied gas, and ensure that only gaseous liquefied gas enters the delivery header 5. In addition, when the flow of liquefied gas fluctuates greatly, such as when the storage device supplies liquid instantaneously, the intermediate separator 7 can temporarily store part of the gas-liquid mixture, so as to avoid the high-speed gas-liquid flow directly impacting the delivery header 5, and maintain the pressure in the header stable.

[0054] As shown in Figure 4 , the intermediate separator 7 is a vertically placed cylindrical container, and the input end 71 is connected along the tangent direction of the middle part of the container, so that the gas-liquid mixture output by the primary heat exchange device 4 flows spirally along the wall of the container, achieving a centrifugal separation effect. The top of the container is provided with a second gas phase outlet 72, which is in communication with the delivery header 5. In this embodiment, the intermediate separator 7 simultaneously plays a role of gas-liquid separation and temporary storage of a small amount of liquid liquefied gas, and the liquid liquefied gas remaining in the intermediate separator 7 will slowly absorb heat and gasify, and then enter the delivery header 5.

[0055] Preferably, a droplet isolation net 73 can be arranged at the top of the intermediate separator 7 to block the suspended droplets. In addition, a liquid discharge port can also be reserved at the bottom, which is normally closed and only used during maintenance. Embodiment Three

[0056] As shown in Figure 6 , this embodiment provides a liquefied gas cold energy utilization system with an intermediate separator 7 and a secondary heat exchange device 9. The system optimizes the structure of the intermediate separator 7 on the basis of the second embodiment, and adds a second pressure reducing valve 8 and a secondary heat exchange device 9, which is suitable for scenarios where the amount of gas used by the combustion equipment 6 is large and stable, such as long-distance trucks using liquefied gas as a power source, which use an engine as the combustion equipment 6 and need to continuously burn liquefied gas. In this scenario, the amount of liquefied gas used continuously is large, and the staged pressure reduction refrigeration by the primary heat exchange device 4 and the secondary heat exchange device 9 can fully utilize the cold energy of the liquefied gas.

[0057] Referring to Figure 4In this embodiment, the container bottom of the intermediate separator 7 is provided with a second liquid phase outlet 74, and a manual stop valve is arranged at the second liquid phase outlet 74, which is kept open during daily operation. In a possible embodiment, an electric valve can be arranged at the second liquid phase outlet 74, and the electric valve is opened or closed according to the ambient temperature monitored by the temperature sensor in the first refrigeration device. When the ambient temperature is high and the first refrigeration device needs to absorb a large amount of heat, the first heat exchange device 4 is sufficient to vaporize all the liquefied gas, and the electric valve does not need to be opened. When the ambient temperature is low and the first refrigeration device operates at low power, a large amount of liquefied gas in the first heat exchange device 4 is not vaporized, and the electric valve can be opened to start the second heat exchange device 9. In another possible embodiment, the opening degree of the electric valve can be determined according to the ambient temperature monitored by the temperature sensor in the second refrigeration device in combination with the ambient temperature monitored by the temperature sensor in the first refrigeration device. For example, when the ambient temperature monitored by the temperature sensor in the second refrigeration device is lower than a set threshold, the electric valve is controlled to be opened by 50%, and when the ambient temperature monitored by the temperature sensor in the second refrigeration device is higher than the set threshold, the electric valve is controlled to be opened by 100%.

[0058] The outer wall of the intermediate separator 7 is wrapped with a thermal insulation layer to reduce the loss of cold energy in the intermediate separator and avoid excessive vaporization of the internal liquid liquefied gas.

[0059] The second pressure reducing valve 8 in this embodiment is a pilot-operated pressure reducing valve, the input end of which is in sealed connection with the second liquid phase outlet 74 of the intermediate separator 7, and the output end of which is in communication with the input end of the second liquefied gas pipeline 92 of the second heat exchange device 9.

[0060] The second pressure reducing valve 8 can reduce the pressure of the liquid liquefied gas output from the second liquid phase outlet 74 of the intermediate separator 7 from 0.3 MPa to 0.15 MPa. Under this pressure drop, part of the liquid liquefied gas is flashed into a gaseous state to form a gas-liquid mixed flow. The temperature of the gas-liquid mixed flow after flashing is about -30°C.

[0061] The second heat exchange device 9 can be integrated in an air conditioner to realize the functions of refrigeration or dehumidification. The second heat exchange device 9 includes a second medium pipeline 91, a second liquefied gas pipeline 92, and a second heat exchange structure 93. The heat exchange medium flowing in the second medium pipeline 91 is air, which is driven by an air conditioner built-in fan to flow through the second heat exchange structure 93 to realize heat exchange.

[0062] As Figure 9As shown, the second liquefied gas pipeline 92 includes three branches, the input end 92a of the three branches is connected with the output end of the second pressure reducing valve 8, and the output end 92b is connected to the delivery main pipe 5. The ratio of the pipe diameter of the output end 92b to the input end 92a of the second liquefied gas pipeline 92 is 2.5:1. The expansion of the pipe diameter ensures the stability of the pressure and flow rate in the second liquefied gas pipeline 92, and prevents the pressure in the pipeline from suddenly increasing due to gasification.

[0063] As shown, Figure 8 The second heat exchange structure 93 is composed of heat exchange plates 93a and corrugated fins 93b. The heat exchange plates 93a can be aluminum alloy plates, and the corrugated fins 93b can be aluminum alloy fins. A plurality of corrugated fins 93b are parallelly attached to the upper and lower surfaces of the heat exchange plates 93a and are fixed by welding. Three branches uniformly pass through the inside of the heat exchange plates 93a and are brazed and sealed with the heat exchange plates, forming a continuous flow channel, which ensures that the liquefied gas in the branches can fully contact the heat exchange plates 93a.

[0064] During operation, the gas-liquid mixture output by the primary heat exchange device 4 enters the intermediate separator 7. The gaseous liquefied gas is gathered at the top under the action of centrifugal force and gravity, enters the delivery main pipe 5 through the second gas phase outlet 72, and the liquid liquefied gas is collected at the bottom and flows into the second pressure reducing valve 8 through the second liquid phase outlet 74.

[0065] After being reduced in pressure by the second pressure reducing valve 8, part of the liquid liquefied gas flashes into a gaseous state. The gas-liquid mixture enters the second liquefied gas pipeline 92 of the secondary heat exchange device 9. The gas-liquid mixture in the branches exchanges heat with the air in the second medium pipeline 91. The liquid liquefied gas gradually fully gasifies after absorbing the heat of the air. The gaseous liquefied gas after gasification converges at the output end and enters the delivery main pipe 5. After being combined with the gaseous liquefied gas from the gas-liquid separation device 3 and the gaseous liquefied gas from the intermediate separator 7, it is delivered to the combustion equipment 6 for combustion.

[0066] By setting the second pressure reducing valve 8 and the secondary heat exchange device 9, the liquid liquefied gas that has not been gasified in the intermediate separator 7 can be partially flashed and heat-exchanged and gasified a second time. The un-gasified liquefied gas is fully utilized to meet the large gas demand of the combustion equipment 6. At the same time, the combination of multiple branches and corrugated fins in the secondary heat exchange device 9 expands the contact area between the liquefied gas and the heat exchange medium, ensuring that the liquefied gas is fully heat-exchanged and gasified, and preventing the liquid liquefied gas from entering the delivery main pipe.

[0067] The liquefied gas cold energy utilization system provided in the embodiment is suitable for long-distance freight trucks that use liquefied gas as fuel. The engine of such a truck consumes liquefied gas continuously, so it is very suitable for using the system to fully utilize the cold energy to provide refrigeration for the vehicle cabin air conditioner, vehicle refrigerator, and other equipment. Example Four

[0068] AsFigure 7 As shown, compared with Embodiment 3, this embodiment adds a first nozzle diffuser 10 and a second nozzle diffuser 11 to be suitable for scenarios with long delivery pipeline paths.

[0069] The first nozzle diffuser 10 is connected to the junction of the first gas phase outlet of the gas-liquid separator 3, the second gas phase outlet 72 of the intermediate separator 7, and the main conveying pipe 5. It is used to stabilize the pressure after the multiple gaseous media converge. The gaseous liquefied gas output from the gas-liquid separator 3 undergoes depressurization flash evaporation, reducing its pressure to 0.2~0.45 MPa. The pressure at the second gas phase outlet 72 of the intermediate separator 7 is also maintained within the 0.2~0.45 MPa range. The first nozzle diffuser 10 merges these two gaseous liquefied gas streams and diffuses them to 0.5~1.2 MPa through a conical pipe structure to meet the conveying requirements of the longer-path main conveying pipe 5.

[0070] The second nozzle diffuser 11 is connected to the junction of the output end of the second liquefied gas pipeline 92 of the secondary heat exchanger 9 and the main delivery pipe 5. It is used to increase the pressure of the gaseous liquefied gas after the secondary heat exchange to the appropriate pressure of the main pipe. After flash evaporation and heat absorption, the pressure of the gaseous liquefied gas output from the secondary heat exchanger 9 drops to 0.1~0.2MPa. The second nozzle diffuser 11 can pressurize this part of the gaseous liquefied gas and input it into the main pipe, while also preventing the gaseous gas in the main pipe from flowing back into the secondary heat exchanger 9.

[0071] By setting up the first nozzle diffuser 10 and the second nozzle diffuser 11, the pressure zones after the first pressure reduction flash evaporation and the second pressure reduction flash evaporation can be divided into zones to maintain pressure stability in each zone. At the same time, the pressure in the main pipe can be increased to ensure that the pressure of the liquefied gas after pressure reduction flash evaporation meets the transportation requirements.

[0072] The pressure and temperature of each part of the system are shown in the table below: Example 5

[0073] like Figure 10 As shown, this embodiment adds a gas storage tank 12 to the fourth embodiment. The gas storage tank 12 is connected in series between the main delivery pipe 5 and the combustion device 6.

[0074] The top of the gas storage tank 12 is welded with a pressure relief valve interface, and a spring-loaded pressure relief valve 13 is installed at the interface. The opening pressure of the pressure relief valve 13 is set to 0.7MPa. When the pressure inside the gas storage tank 12 exceeds 0.7MPa due to abnormal conditions (such as the sudden shutdown of the combustion equipment 6 or the failure of the main valve to close), the pressure relief valve 13 will automatically open to release pressure. It will automatically close when the pressure drops below 0.6MPa to ensure the safe use of the gas storage tank 12.

[0075] By setting the gas storage tank 12, the pressure and flow of gaseous liquefied gas entering the combustion device 6 can be stabilized, and problems such as large and small combustion flame, flameout and the like caused by gas fluctuation can be avoided, thereby ensuring the stability of the combustion device 6. In addition, the gas storage tank 12 can also mix the liquefied gas uniformly. Since the saturated vapor pressure of propane is higher than that of butane, the gas flashed out for the first time is mainly propane, and the gas output from the primary heat exchange device 4 and the secondary heat exchange device 9 gradually increases in butane. After entering the gas storage tank, the gases can be fully mixed and uniform, which is beneficial to full combustion. Example six

[0076] Corresponding to the system in example one, a liquefied gas cold energy utilization method is provided in this embodiment, comprising the following steps: S1: liquefied gas storage, storing liquefied gas in a liquefied gas storage device 1 with an internal pressure maintained at 0.5-1.2 MPa, and a liquid outlet is arranged at the bottom of the liquefied gas storage device 1; S2: primary pressure reduction flash evaporation, reducing the pressure of the liquid liquefied gas output from the liquid outlet of the liquefied gas storage device 1 to 0.2-0.45 MPa through the first pressure reduction valve 2, so as to cause part of the liquid liquefied gas to flash evaporate into gas; S3: primary gas-liquid separation, introducing the gas-liquid mixed liquefied gas treated in step S2 into the gas-liquid separation device 3 to separate the first gaseous liquefied gas and the first liquid liquefied gas, and the first gaseous liquefied gas is transported to the delivery main pipe through the first gas phase outlet 31 of the gas-liquid separation device 3; S4: primary heat exchange and cold extraction, introducing the first liquid liquefied gas separated in step S3 into the first liquefied gas pipeline 42 of the primary heat exchange device 4, so that the first liquid liquefied gas exchanges heat with the heat exchange medium flowing in the first medium pipeline 41 of the primary heat exchange device 4, and the first liquid liquefied gas gasifies to form the second gaseous liquefied gas after absorbing heat, and the second gaseous liquefied gas is transported to the delivery main pipe 5 through the output end of the first liquefied gas pipeline 42; S5: gaseous delivery and combustion, the first gaseous liquefied gas of step S3 and the second gaseous liquefied gas of step S4 are combined through the delivery main pipe 5, and the combined gaseous liquefied gas is delivered to the combustion device 6 for combustion. Example seven

[0077] Corresponding to the system in example three, a liquefied gas cold energy utilization method is provided in this embodiment, which further comprises the following steps between step S4 and step S5 on the basis of example six: S41: intermediate separation, introducing the second gaseous liquefied gas (containing residual liquid liquefied gas which has not been completely gasified) output from the first liquefied gas pipeline 42 in step S4 into the intermediate separator 7 to separate the third gaseous liquefied gas and the second liquid liquefied gas, and the third gaseous liquefied gas is transported to the delivery main pipe 5 through the second gas phase outlet 72 of the intermediate separator 7; S42: two-stage pressure reduction flash evaporation, the second liquid liquefied gas separated in step S41 is reduced in pressure to 0.1-0.2 MPa by a second pressure reduction valve, so as to cause part of the second liquid liquefied gas to flash evaporate into a gaseous state; S43: two-stage heat exchange to obtain cold, the gas-liquid mixed liquefied gas after step S42 is introduced into the second liquefied gas pipeline 92 of the two-stage heat exchange device 9, so that the gas-liquid mixed liquefied gas exchanges heat with the heat exchange medium flowing in the second medium pipeline 91 of the two-stage heat exchange device 9, the liquid liquefied gas that is not flash evaporated absorbs heat and completely gasifies to form fourth gaseous liquefied gas, and the fourth gaseous liquefied gas is transported to the delivery main pipe 5 through the output end of the second liquefied gas pipeline 92, and is delivered to the combustion equipment 6 after being combined with the first gaseous liquefied gas and the third gaseous liquefied gas. Example Eight

[0078] Corresponding to the system in Example Four, the present embodiment provides a liquefied gas cold energy utilization method, which, on the basis of Example Seven, when delivering the first gaseous liquefied gas to the delivery main pipe 5 in step S3 and delivering the third gaseous liquefied gas to the delivery main pipe 5 in step S41, further comprises: stabilizing the pressure of the combined gas stream of the first gaseous liquefied gas and the third gaseous liquefied gas by the first nozzle pressure expansion device 10, so as to maintain the pressure of the combined gas stream at 0.2-0.45 MPa; when delivering the fourth gaseous liquefied gas to the delivery main pipe 5 in step S43, the pressure of the fourth gaseous liquefied gas is increased to 0.2-0.45 MPa by the second nozzle pressure expansion device 11, so as to ensure that the pressure of all gaseous liquefied gas in the delivery main pipe 5 is consistent before being delivered to the combustion equipment 6; and before the gaseous liquefied gas is delivered to the combustion equipment 6, the gaseous liquefied gas is first introduced into the gas storage tank 12 connected in series between the delivery main pipe 5 and the combustion equipment 6 for temporary storage, and when the pressure in the gas storage tank 12 exceeds 0.6-0.8 MPa, the pressure relief valve on the gas storage tank 12 automatically opens to release pressure.

[0079] The above examples are only for illustrating the technical concept and characteristics of the present application, and the purpose is to enable those skilled in the art to understand the content of the present application and implement it, and cannot limit the protection scope of the present application. Any equivalent changes or modifications made according to the spirit and essence of the present application shall be covered within the protection scope of the present application.

Claims

1. A liquefied gas cold energy utilization system, characterized by, The liquefied gas storage device is internally pressurized at 0.5-1.2 MPa, and the bottom of the liquefied gas storage device is provided with a liquid outlet. The first pressure reducing valve is connected with the liquid outlet of the liquefied gas storage device, and is used for reducing the pressure of the liquefied gas to 0.2-0.45 MPa and making part of the liquefied gas flash into a gaseous state. The gas-liquid separation device is connected with the output end of the first pressure reducing valve, and is provided with a first gas phase outlet and a first liquid phase outlet. The first heat exchange device comprises a first medium pipeline for flowing through a heat exchange medium and a first liquefied gas pipeline for flowing through liquefied gas, and the first medium pipeline and the first liquefied gas pipeline are provided with a first heat exchange structure. The first gas phase outlet of the gas-liquid separation device is connected with one end of the delivery main pipe, and the other end of the delivery main pipe is connected with the combustion device. The gas-liquid separation device is horizontally placed in a cylindrical structure, the first gas phase outlet is arranged at the top of the gas-liquid separation device, the first liquid phase outlet is arranged at the bottom of the gas-liquid separation device, a liquid droplet isolation net is arranged below the first gas phase outlet, and the outer wall of the gas-liquid separation device is provided with a heat preservation layer.

2. The liquefied gas cold energy utilization system according to claim 1, characterized by The first liquefied gas pipeline of the first heat exchange device is a horizontally arranged tube bundle with gradually increasing pipe diameters, the pipe diameter ratio of the rear end to the front end of the first liquefied gas pipeline is 1.5:1-2.5:1, and the first heat exchange structure is an aluminum fin wrapped outside the first liquefied gas pipeline.

3. The liquefied gas cold energy utilization system according to claim 1, characterized by The liquefied gas cold energy utilization system further comprises an intermediate separator, the output end of the first liquefied gas pipeline is connected with the input end of the intermediate separator, the intermediate separator is provided with a second gas phase outlet, the second gas phase outlet is connected with the delivery main pipe, and the gaseous liquefied gas output from the first liquefied gas pipeline is subjected to gas-liquid separation through the intermediate separator and then output from the second gas phase outlet to the delivery main pipe.

4. The liquefied gas cold energy utilization system according to claim 1, characterized by The intermediate separator is vertically placed in a cylindrical structure, the second gas phase outlet is arranged at the top of the intermediate separator, the input end of the first liquefied gas pipeline is arranged at the middle of the intermediate separator in a tangential direction, and a liquid droplet isolation net is arranged below the second gas phase outlet.

5. The liquefied gas cold energy utilization system according to claim 4, characterized by The intermediate separator further comprises a second liquid phase outlet arranged at the bottom of the intermediate separator, the outer wall of the intermediate separator is wrapped with a heat preservation layer, and the liquefied gas cold energy utilization system further comprises:

6. The liquefied gas cold energy utilization system according to claim 5, characterized by The second pressure reducing valve is connected with the second liquid phase outlet of the intermediate separator, and is used for reducing the pressure of the liquefied gas to 0.1-0.2 MPa and making part of the liquefied gas flash into a gaseous state. ​ The secondary heat exchange device comprises a second medium pipeline for circulating a heat exchange medium and a second liquefied gas pipeline for circulating liquefied gas, a second heat exchange structure is arranged between the second medium pipeline and the second liquefied gas pipeline, an input end of the second liquefied gas pipeline is connected with an output end of the second pressure reducing valve, an output end of the second liquefied gas pipeline is connected with the delivery main pipe, and the second medium pipeline is connected with a second refrigeration device.

7. The liquefied gas cold energy utilization system according to claim 6, characterized by The second liquefied gas pipeline comprises a plurality of branch pipes, the second heat exchange structure comprises heat exchange plates and corrugated fins, the corrugated fins are arranged on upper and lower surfaces of the heat exchange plates, the plurality of branch pipes pass through the inside of the heat exchange plates, input ends of the plurality of branch pipes are connected with the output end of the second pressure reducing valve, output ends of the plurality of branch pipes are connected with the delivery main pipe after being connected with each other, and a ratio of a rear end pipe diameter to a front end pipe diameter of the second liquefied gas pipeline is 2:1 to 3:

1.

8. The liquefied gas cold energy utilization system according to claim 6, characterized by Further comprising: A first nozzle pressure expansion device is connected with the first gaseous phase outlet of the gas-liquid separation device, the second gaseous phase outlet of the intermediate separator and the intersection of the delivery main pipe, and is used for stabilizing the pressure of the plurality of gaseous media after being combined; A second nozzle pressure expansion device is connected with the intersection of the output end of the second liquefied gas pipeline of the secondary heat exchange device and the delivery main pipe, and is used for improving the pressure of the gaseous liquefied gas after the secondary heat exchange to be adapted to the delivery main pipe.

9. A method for utilizing cold energy of liquefied gas, characterized by, The method comprises the following steps by using the liquefied gas cold energy utilization system in any one of claims 1 to 5: S1: liquefied gas storage, storing liquefied gas in a liquefied gas storage device, and maintaining the internal pressure at 0.5 to 1.2 MPa; S2: primary pressure reduction flash evaporation, reducing the pressure of the liquid liquefied gas output from the liquid outlet of the liquefied gas storage device to 0.2 to 0.45 MPa through a first pressure reducing valve, so that part of the liquid liquefied gas is flashed into a gaseous state; S3: primary gas-liquid separation, introducing the gas-liquid mixed liquefied gas treated in step S2 into a gas-liquid separation device to obtain first gaseous liquefied gas and first liquid liquefied gas, wherein the first gaseous liquefied gas is delivered to the delivery main pipe through the first gaseous phase outlet of the gas-liquid separation device; S4: primary heat exchange refrigeration, introducing the first liquid liquefied gas obtained in step S3 into a first liquefied gas pipeline of a primary heat exchange device, so that the first liquid liquefied gas exchanges heat with a heat exchange medium circulating in a first medium pipeline of the primary heat exchange device, the first liquid liquefied gas is gasified to form second gaseous liquefied gas after absorbing heat, and the second gaseous liquefied gas is delivered to the delivery main pipe through the output end of the first liquefied gas pipeline; S5: gaseous delivery combustion, delivering the combined gaseous liquefied gas to a combustion device for combustion through the delivery main pipe.

10. A method for utilizing cold energy of liquefied gas, characterized by, The method comprises the following steps by using the liquefied gas cold energy utilization system in any one of claims 6 to 8: S1: liquefied gas storage, storing liquefied gas in a liquefied gas storage device, and maintaining the internal pressure at 0.5 to 1.2 MPa; S2: primary pressure reduction flash evaporation, reducing the pressure of the liquid liquefied gas output from the liquid outlet of the liquefied gas storage device to 0.2 to 0.45 MPa through a first pressure reducing valve, so that part of the liquid liquefied gas is flashed into a gaseous state; S3: primary gas-liquid separation, the gas-liquid mixed liquefied gas treated in step S2 is introduced into a gas-liquid separation device to obtain first gaseous liquefied gas and first liquid liquefied gas, wherein the first gaseous liquefied gas is transported to the delivery main pipe through a first gas phase outlet of the gas-liquid separation device; S4: primary heat exchange refrigeration, the first liquid liquefied gas separated in step S3 is introduced into a first liquefied gas pipeline of a primary heat exchange device to exchange heat with a heat exchange medium flowing in a first medium pipeline of the primary heat exchange device, and the first liquid liquefied gas is gasified to form second gaseous liquefied gas after absorbing heat, and the second gaseous liquefied gas is transported to the intermediate separator through an output end of the first liquefied gas pipeline; S41: intermediate separation, the second gaseous liquefied gas (containing residual liquid liquefied gas that is not completely gasified) output from the first liquefied gas pipeline in step S4 is introduced into the intermediate separator to obtain third gaseous liquefied gas and second liquid liquefied gas, and the third gaseous liquefied gas is transported to the delivery main pipe through a second gas phase outlet of the intermediate separator; S42: secondary pressure reduction flash evaporation, the second liquid liquefied gas separated in step S41 is reduced in pressure to 0.1-0.2 MPa through a second pressure reduction valve to cause part of the second liquid liquefied gas to flash evaporate into a gaseous state; S43: secondary heat exchange refrigeration, the gas-liquid mixed liquefied gas treated in step S42 is introduced into a second liquefied gas pipeline of a secondary heat exchange device to exchange heat with a heat exchange medium flowing in a second medium pipeline of the secondary heat exchange device, and the liquid liquefied gas that is not flash evaporated is completely gasified to form fourth gaseous liquefied gas after absorbing heat, and the fourth gaseous liquefied gas is transported to the delivery main pipe through the second liquefied gas pipeline to be combined with the first gaseous liquefied gas and the third gaseous liquefied gas; S5: gaseous delivery combustion, the combined gaseous liquefied gas is delivered to a combustion device for combustion by the delivery main pipe.

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