Two-stage heat exchange LNG gasification system

Abstract

The utility model discloses a two-stage heat exchange LNG gasification system which comprises an LNG storage tank, a low-temperature LNG outlet of the LNG storage tank is connected to an LNG gasification heat exchange structure through an output pipeline provided with an LNG pump and then is connected to an NG output end, and the two-stage heat exchange LNG gasification system is characterized in that the LNG gasification heat exchange structure comprises an LNG first-stage gasification heat exchange structure and an LNG second-stage cold release heat exchange structure which are connected in series front and back; the LNG first-stage gasification heat exchange structure is used for achieving gasification heat exchange from LNG to low-temperature NG, and the LNG second-stage cold release heat exchange structure is used for achieving conversion heat exchange from the low-temperature NG to normal-temperature NG. Two-stage heat exchange in the LNG gasification process can be achieved, the cold energy recovery and conversion efficiency is improved, cold energy utilization is better achieved, the gasifier is prevented from being frozen in winter, the advantages of being more energy-saving and efficient are achieved, and considerable economic benefits and energy-saving and emission-reducing benefits can be generated.

Description

Technical Field

[0001] The utility model relates to LNG gasification equipment capable of realizing cold energy recovery and utilization, in particular to a two-stage heat exchange LNG gasification system. Background Art

[0002] Many types of liquids, such as liquefied natural gas (LNG), liquid oxygen, liquid nitrogen, liquid ethane, liquid propane, etc., need to be vaporized before use. The vaporization process releases a large amount of cold energy. If this cold energy is recovered, energy consumption can be reduced and economic benefits can be obtained.

[0003] With the urgent need to transform traditional energy in my country, my country's LNG industry chain has developed rapidly. By 2023, China's LNG imports will reach 71.32 million tons, making it the world's largest LNG importer. Based on the requirements of modern energy system planning, we need to strengthen energy conservation and waste energy recovery in energy processing, storage and transportation facilities, and promote comprehensive utilization of waste energy such as waste heat and pressure, and LNG cold energy.

[0004] The gasification device is a key facility to ensure that LNG is converted into NG and transported to the end user. However, in winter, due to the decrease in seawater temperature and ambient temperature, LNG vaporizers such as open rack vaporizers (ORV) and air temperature vaporizers are prone to ice formation, which will seriously affect their normal operation. Although the traditional gas water bath heating method can solve the problem of vaporizer ice formation, it will lead to a significant increase in energy consumption and does not meet the requirements of energy conservation and emission reduction.

[0005] Therefore, how to design an LNG gasification equipment that can improve the cold energy recovery and conversion efficiency, better realize the cold energy utilization, and avoid the freezing of the gasifier in winter has become a problem that technical personnel in this field need to consider and solve. Utility Model Content

[0006] In view of the above-mentioned deficiencies in the prior art, the technical problem to be solved by the present invention is: how to provide a two-stage heat exchange LNG gasification system that can achieve two-stage heat exchange, improve the efficiency of cold energy recovery and conversion, better realize cold energy utilization, avoid ice formation in the vaporizer in winter, and be more energy-saving and efficient.

[0007] In order to solve the above technical problems, the utility model adopts the following technical solutions:

[0008] A two-stage heat exchange LNG gasification system comprises an LNG storage tank, wherein the low-temperature LNG outlet of the LNG storage tank is connected to an LNG gasification heat exchange structure through an output pipeline equipped with an LNG pump and then connected to an NG output end, wherein the LNG gasification heat exchange structure comprises an LNG primary gasification heat exchange structure and an LNG secondary cooling heat exchange structure arranged in series front and back, wherein the LNG primary gasification heat exchange structure is used to realize gasification heat exchange from LNG to low-temperature NG, and the LNG secondary cooling heat exchange structure is used to realize conversion heat exchange from low-temperature NG to normal-temperature NG.

[0009] In this way, the LNG gasification system of the utility model adopts a two-stage heat exchange method. The first stage heat exchange realizes the gasification of LNG first, and the second stage heat exchange realizes the conversion of NG from low temperature to normal temperature. Therefore, it can better realize the recovery and utilization of cold energy, improve the heat exchange conversion efficiency, and better avoid the freezing of the gasification device in winter, making it more energy-saving and efficient.

[0010] Furthermore, the LNG primary gasification heat exchange structure includes a gasification heat exchanger, an ice maker and an ice storage container, the gasification heat exchanger is provided with a low-temperature LNG inlet, a low-temperature NG outlet, an antifreeze hot inlet and an antifreeze cold outlet; the LNG inlet and the low-temperature NG outlet are connected through an internal LNG gasification channel, the antifreeze hot inlet and the antifreeze cold outlet are connected through an internal heat exchanger antifreeze heat exchange channel, the LNG gasification channel and the heat exchanger antifreeze heat exchange channel are adjacently arranged and used for heat exchange; the ice maker is provided with an antifreeze hot outlet, an antifreeze cold inlet, an ice outlet and a water inlet, the antifreeze hot outlet and the antifreeze cold outlet are connected through an internal heat exchanger antifreeze heat exchange channel, the LNG gasification channel and the heat exchanger antifreeze heat exchange channel are adjacently arranged and used for heat exchange; The cold inlets are connected through an internal ice-making machine antifreeze heat exchange channel, and the ice outlet and the water inlet are connected through an internal ice-making heat exchange channel. The ice-making machine antifreeze heat exchange channel and the ice-making heat exchange channel are adjacently arranged and used for heat exchange; an ice inlet A and a water outlet A are provided on the ice storage container and are connected to the inner cavity; the pipe connected to the antifreeze cold outlet is connected to the antifreeze cold inlet, and the pipe connected to the antifreeze hot outlet is connected to the antifreeze hot inlet after installing a circulation pump A to form a circulation; the pipe connected to the ice outlet is connected to the ice inlet A, and the pipe connected to the water outlet A is connected to the water inlet after installing a circulation pump B to form a circulation.

[0011] In this way, the LNG primary gasification heat exchange structure is used to realize the first stage of heat exchange, which uses the latent heat of low-temperature water to offset the gasification heat of LNG using an ice maker. The process is that -162°C low-temperature LNG comes out of the LNG storage tank, is transported to the gasification heat exchanger through an LNG pump, and after absorbing the heat energy released by the ice maker cycle, it becomes -25°C low-temperature NG.

[0012] The heat exchange cycle of the LNG primary gasification heat exchange structure includes antifreeze circulation and ice making cycle. For the antifreeze circulation, the antifreeze can be a high-concentration ethylene glycol aqueous solution or other environmentally friendly and economical solution. Under the action of the circulation pump A, the antifreeze comes out from the antifreeze hot outlet on the ice maker, passes through the gasification heat exchanger, absorbs the LNG gasification cold energy, and then the temperature drops. It returns to the ice maker through the antifreeze tank, and then absorbs the latent heat of the low-temperature water in the ice making cycle, thereby completing the cycle. For the ice making cycle, under the action of the circulation pump B, the low-temperature water comes out from the water outlet A on the ice storage container, passes through the ice maker, becomes ice slurry, and then enters the ice storage container from the ice inlet A.

[0013] The ice maker preferably uses an existing supercooled water ice maker, and the low-temperature water is cooled to a supercooled state in the supercooler inside the ice maker, and after passing through the cold eliminator, it is transported out of the ice maker in the form of ice slurry. The ice storage container stores LNG gasification cold energy in the form of ice slurry in winter, which can be used for air conditioning cooling in summer, thereby generating considerable economic benefits and energy-saving and emission reduction benefits; if there is no need to store cold energy in winter, the low-temperature water required for the ice-making cycle can be directly obtained from seawater, lake water or river water, and accordingly, the prepared ice slurry is directly discharged into seawater, lake water or river water.

[0014] Furthermore, an antifreeze tank is installed on the pipe connected from the antifreeze liquid cold outlet to the antifreeze liquid cold inlet.

[0015] In this way, by accumulating and transferring antifreeze in the antifreeze tank, the circulation supply effect of the antifreeze can be better guaranteed and antifreeze can be better achieved.

[0016] Furthermore, the ice storage container is provided with an ice inlet B and a water outlet B connected to the inner cavity, and the ice inlet B and the water outlet B are connected to the heat pump unit of the LNG secondary cooling and heat exchange structure, so that the ice storage container constitutes the heat pump heat source of the heat pump unit.

[0017] In this way, the ice storage container also serves as a heat source for the heat pump unit, not only providing the heat pump unit with latent heat of low-temperature water so that it does not need an additional heat source, but also further improving the cold preservation and freezing effect of the ice storage container itself.

[0018] As an option for the LNG secondary cooling and heat exchange structure, the LNG secondary cooling and heat exchange structure includes a heat pump unit, which is provided with a low-temperature NG inlet, a normal temperature NG outlet, a heat source hot inlet and a heat source cold outlet. An NG channel is connected between the low-temperature NG inlet and the normal temperature NG outlet, a heat pump channel and a heat pump device are connected between the heat source hot inlet and the heat source cold outlet, and the NG channel and the heat pump channel are adjacent to each other and used for heat exchange; the outer side of the low-temperature NG inlet is connected to the low-temperature NG outlet of the gasification heat exchanger through a pipeline, and the outer side of the normal temperature NG outlet is connected to the NG output end through a pipeline; the external pipelines of the heat source hot inlet and the heat source cold outlet are connected to the heat source of the heat pump and constitute a heat pump cycle.

[0019] In this way, in the LNG secondary cooling and heat exchange structure, the heat pump unit is used to pump heat and exchange heat with low-temperature NG, and the NG at room temperature is input to the NG output end for use. The NG output end is usually connected to an external NG user. In this way, the secondary heat exchange of LNG is realized, and the utilization efficiency of the cold energy of LNG gasification is improved.

[0020] As an optional form of heat pump heat source, the heat pump heat source is a heat source tower. The external pipeline of the heat source cold outlet of the heat pump unit is connected to the return liquid port of the heat source tower after passing through a circulation pump C. The external pipeline of the liquid outlet of the heat source tower is connected to the heat source hot inlet of the heat pump unit to form a circulation; the heat source tower is also provided with an air inlet and an air outlet.

[0021] In this way, the heat source tower is a conventional heat pump heat source device with good heat exchange effect and easy implementation. When the heat pump heat source is in the form of a heat source tower, the heat exchange process of the second-stage LNG secondary cooling and heat exchange structure is that the low-temperature NG of -25°C comes out of the gasification heat exchanger, enters the heat pump unit from the low-temperature NG inlet, absorbs the circulating heat energy of the heat source tower, and becomes 5°C normal temperature NG, and then is transported to the NG user at the NG output end. The heat source tower circulation is that under the action of the circulating pump C, the antifreeze liquid comes out from the heat source cold outlet on the heat pump unit, passes through the heat source tower, absorbs the low-temperature heat energy in the air, and the temperature rises, and then enters the heat pump unit from the heat source hot inlet, thereby completing the cycle. The antifreeze circulating in the heat source tower is a calcium chloride solution or an ethylene glycol solution.

[0022] As another optional method of heat source for heat pump, the heat source for heat pump is an ice storage container in the LNG primary gasification heat exchange structure, the external pipe of the heat source cold outlet of the heat pump unit is connected to the ice inlet B of the ice storage container after passing through a crystal promoter, and the external pipe of the water outlet B of the ice storage container is connected to the heat source hot inlet of the heat pump unit after passing through a circulation pump D to form a circulation.

[0023] In this way, the ice storage container in the LNG primary gasification heat exchange structure is used as the heat source of the heat pump to form an ice source heat pump, which is not only conducive to implementation, but also can better take away the heat of the ice storage container and better maintain its cold storage effect. The heat exchange process of the LNG secondary cooling heat exchange structure is that the low-temperature NG of -25°C comes out of the gasification heat exchanger, enters the heat pump unit from the low-temperature NG inlet, absorbs the latent heat of the low-temperature water in the ice storage container, and becomes 5°C normal temperature NG, and then is transported to the NG user at the NG output end. The ice source side cycle is formed when the low-temperature water comes out from the outlet B on the ice storage container under the action of the circulation pump D, and becomes supercooled water after the heat pump unit releases heat, and then undergoes phase change and freezes through the crystal promoter, and then enters the ice storage container from the ice inlet B, thus completing the cycle.

[0024] As another option for the LNG secondary cooling and heat exchange structure, the LNG secondary cooling and heat exchange structure includes a water bath vaporizer and a gas boiler; the water bath vaporizer is provided with a low-temperature NG inlet, a normal temperature NG outlet, a high-temperature hot water inlet and a low-temperature hot water outlet; an NG heat exchange channel is provided between the low-temperature NG inlet and the normal temperature NG outlet, a water heat exchange channel is provided between the high-temperature hot water inlet and the low-temperature hot water outlet, and the water heat exchange channel and the NG heat exchange channel are adjacently arranged and used for heat exchange; the gas boiler is provided with a high-temperature hot water outlet, a low-temperature hot water inlet and a gas inlet; the low-temperature NG inlet is externally connected to the low-temperature NG outlet of the gasification heat exchanger through a pipeline, the low-temperature hot water outlet is externally connected to the low-temperature hot water inlet of the gas boiler, and the high-temperature hot water outlet of the gas boiler is externally connected to the high-temperature hot water inlet through a circulation pump E to form a circulation; the normal temperature NG outlet of the water bath vaporizer is externally connected to the NG output end through a three-way valve, and the branch interface of the three-way valve is connected to the gas inlet of the gas boiler through a pipeline.

[0025] In this way, when the LNG secondary cooling and heat exchange structure exchanges heat with the water bath vaporizer, its heat exchange process is as follows: the low-temperature NG of -25°C comes out from the gasification heat exchanger, enters the water bath vaporizer from the low-temperature NG inlet, absorbs the heat energy of the hot water circulation of the gas boiler, and becomes the normal temperature NG of 5°C. After that, part of it is delivered to the gas boiler through the three-way valve to meet its operating consumption, and the other part is delivered to the NG user at the NG output end. The gas boiler hot water circulation is that under the action of the circulation pump E, the high-temperature hot water comes out from the high-temperature hot water outlet on the gas boiler, exchanges heat to the low-temperature NG through the water bath vaporizer, the temperature drops to become low-temperature hot water, and then returns to the gas boiler, thus completing the cycle. In this way, the combustion of NG formed by partial gasification is directly used as a heat source to generate heat, and then the gasified low-temperature NG is converted into normal temperature NG through heat exchange in the water bath vaporizer to be supplied to the user, avoiding the problem that traditional LNG gasification equipment is easy to freeze in winter.

[0026] Therefore, in the present invention, after LNG comes out of the LNG storage tank, it will go through two stages of heat exchange in total. The first stage of heat exchange is carried out in the gasification heat exchanger. After the low-temperature LNG at -162°C absorbs the heat energy released by the ice-making machine cycle, it becomes a low-temperature NG at -25°C, and then enters the second stage heat exchange device; the second stage of heat exchange is carried out in the heat pump unit or water bath gasifier. After the low-temperature NG at -25°C absorbs the heat energy released by the heat pump cycle or the gas boiler hot water cycle, it becomes a normal temperature NG at 5°C, and then is delivered to the user. In the second stage of heat exchange, heat pump heat exchange is the main form, and water bath gasifier heat exchange is only for LNG gasification stations that already have boiler conditions and low natural gas prices.

[0027] Therefore, compared with the prior art, the utility model is an LNG gasification device of a heat pump composite ice maker, which can release LNG gasification cold energy in stages, solving the problems of easy freezing and low efficiency of some traditional LNG gasifiers such as open-shelf gasifiers and air-temperature gasifiers in winter, and also greatly reduces the energy consumption of gas water bath gasifiers. In addition, in winter, the present invention stores LNG gasification cold energy in the form of ice slurry through the ice storage tank, which can be used for air conditioning cooling in summer, thereby generating considerable economic benefits and energy-saving and emission reduction benefits.

[0028] In summary, the utility model can realize two-stage heat exchange in the LNG gasification process, improve the cold energy recovery and conversion efficiency, better realize cold energy utilization, avoid ice formation in the gasifier in winter, has the advantages of being more energy-saving and efficient, and can generate considerable economic benefits and energy-saving and emission reduction benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of the first specific implementation mode of the utility model.

[0030] Figure 2 This is a schematic diagram of the LNG secondary cooling and heat exchange structure when the heat source of the heat pump in the first embodiment is a heat source tower.

[0031] Figure 3 This is a schematic diagram of the LNG secondary cooling and heat exchange structure when the heat source of the heat pump in the first embodiment is an ice storage container.

[0032] Figure 4 The arrows in each figure indicate the direction of fluid flow. DETAILED DESCRIPTION

[0033] The utility model is further described in detail below in conjunction with specific implementation methods.

[0034] The first implementation method: Figure 1-3As shown, a two-stage heat exchange LNG gasification system includes an LNG storage tank 1, and the low-temperature LNG outlet 101 of the LNG storage tank 1 is connected to the LNG gasification heat exchange structure through an output pipeline equipped with an LNG pump 2, and then connected to the NG output end 10, characterized in that the LNG gasification heat exchange structure includes an LNG primary gasification heat exchange structure and an LNG secondary cooling heat exchange structure arranged in series front and back, the LNG primary gasification heat exchange structure is used to realize gasification heat exchange from LNG to low-temperature NG, and the LNG secondary cooling heat exchange structure is used to realize conversion heat exchange from low-temperature NG to normal temperature NG.

[0035] In this way, the LNG gasification system of the utility model adopts a two-stage heat exchange method. The first stage heat exchange realizes the gasification of LNG first, and the second stage heat exchange realizes the conversion of NG from low temperature to normal temperature. Therefore, it can better realize the recovery and utilization of cold energy, improve the heat exchange conversion efficiency, and better avoid the freezing of the gasification device in winter, making it more energy-saving and efficient.

[0036] Furthermore, the LNG primary gasification heat exchange structure includes a gasification heat exchanger 3, an ice maker 6, and an ice storage container 8, the gasification heat exchanger is provided with a low-temperature LNG inlet 301, a low-temperature NG outlet 302, an antifreeze hot inlet 303, and an antifreeze cold outlet 304; the LNG inlet 301 and the low-temperature NG outlet 302 are connected through an internal LNG gasification channel, the antifreeze hot inlet 303 and the antifreeze cold outlet 304 are connected through an internal heat exchanger antifreeze heat exchange channel, the LNG gasification channel and the heat exchanger antifreeze heat exchange channel are adjacently arranged and used for heat exchange; the ice maker 6 is provided with an antifreeze hot outlet 601, an antifreeze cold inlet 602, an ice outlet 603, and a water inlet 604, the antifreeze hot outlet 601 and the antifreeze cold outlet 304 are connected through an internal heat exchanger antifreeze heat exchange channel. The liquid cooling inlet 602 is connected through the internal ice maker antifreeze heat exchange channel, and the ice outlet 603 and the water inlet 604 are connected through the internal ice making heat exchange channel. The ice maker antifreeze heat exchange channel and the ice making heat exchange channel are arranged adjacent to each other and are used for heat exchange; an ice inlet A801 ​​and a water outlet A802 are provided on the ice storage container 8 and are connected to the inner cavity; the pipe connected to the antifreeze liquid cold outlet 304 is connected to the antifreeze liquid cold inlet 602, and the pipe connected to the antifreeze liquid hot outlet 601 is connected to the antifreeze liquid hot inlet 303 after installing a circulation pump A5 to form a circulation; the pipe connected to the ice outlet 603 is connected to the ice inlet A801, and the pipe connected to the water outlet A802 is connected to the water inlet 604 after installing a circulation pump B7 to form a circulation.

[0037] In this way, the LNG primary vaporization heat exchange structure is used to realize the first stage of heat exchange, which uses the latent heat of low-temperature water to offset the vaporization heat of LNG using an ice maker. The process is that -162°C low-temperature LNG comes out of the LNG storage tank 1, is transported to the vaporization heat exchanger 3 through the LNG pump 2, and after absorbing the heat energy released by the ice maker cycle, it becomes -25°C low-temperature NG.

[0038] The heat exchange cycle of the LNG primary gasification heat exchange structure includes an antifreeze cycle and an ice-making cycle. In the antifreeze cycle, the antifreeze can be a high-concentration ethylene glycol aqueous solution or other environmentally friendly and economical solution. Under the action of the circulation pump A5, the antifreeze comes out from the antifreeze hot outlet 601 on the ice maker 6, passes through the gasification heat exchanger 3, absorbs the LNG gasification cold energy, and then the temperature drops. It returns to the ice maker 6 through the antifreeze tank 4, and then absorbs the latent heat of the low-temperature water in the ice-making cycle, thereby completing the cycle. In the ice-making cycle, under the action of the circulation pump B7, the low-temperature water comes out from the water outlet A802 on the ice storage container 8, passes through the ice maker 6, becomes ice slurry, and then enters the ice storage container 8 from the ice inlet A801.

[0039] The ice maker 6 preferably adopts an existing supercooled water ice maker, and the low-temperature water is cooled to a supercooled state in the supercooler inside the ice maker, and after passing through the cold eliminator, it is transported out of the ice maker in the form of ice slurry. The ice storage container 8 stores LNG gasification cold energy in the form of ice slurry in winter, which can be used for air conditioning cooling in summer, thereby generating considerable economic benefits and energy-saving and emission reduction benefits; if there is no need to store cold energy in winter, the low-temperature water required for the ice-making cycle can be directly obtained from seawater, lake water or river water, and accordingly, the prepared ice slurry is directly discharged into seawater, lake water or river water.

[0040] Furthermore, an antifreeze tank 4 is installed on the pipe connected to the antifreeze liquid cold outlet 304 and the antifreeze liquid cold inlet 602 .

[0041] In this way, the antifreeze liquid is accumulated and transferred in the antifreeze tank 4, so that the circulation supply effect of the antifreeze liquid can be better guaranteed and the antifreeze can be better achieved.

[0042] Furthermore, the ice storage container 8 is also provided with an ice inlet B803 and a water outlet B804 connected to the inner cavity, and the ice inlet B803 and the water outlet B804 are connected to the heat pump unit of the LNG secondary cooling and heat exchange structure, so that the ice storage container 8 constitutes the heat pump heat source of the heat pump unit.

[0043] In this way, the ice storage container also serves as a heat source for the heat pump unit, not only providing the heat pump unit with latent heat of low-temperature water so that it does not need an additional heat source, but also further improving the cold preservation and freezing effect of the ice storage container itself.

[0044] As an option of the LNG secondary cooling and heat exchange structure, the LNG secondary cooling and heat exchange structure includes a heat pump unit 9, which is provided with a low-temperature NG inlet 901, a normal temperature NG outlet 902, a heat source hot inlet 903 and a heat source cold outlet 904. An NG channel is connected between the low-temperature NG inlet 901 and the normal temperature NG outlet 902, and a heat pump channel and a heat pump device are connected between the heat source hot inlet 903 and the heat source cold outlet 904. The NG channel and the heat pump channel are adjacently arranged and used for heat exchange; the outer side of the low-temperature NG inlet 901 is connected to the low-temperature NG outlet 302 of the gasification heat exchanger 3 through a pipeline, and the outer side of the normal temperature NG outlet 902 is connected to the NG output end 10 through a pipeline; the external pipelines of the heat source hot inlet 903 and the heat source cold outlet 904 are connected to the heat pump heat source 11 and constitute a heat pump cycle.

[0045] In this way, in the LNG secondary cooling and heat exchange structure, the heat pump unit is used to pump heat and exchange heat with low-temperature NG, and the NG at room temperature is input to the NG output end for use. The NG output end is usually connected to an external NG user. In this way, the secondary heat exchange of LNG is realized, and the utilization efficiency of the cold energy of LNG gasification is improved.

[0046] As an alternative to heat pump heat source, see Figure 2 The heat source of the heat pump is a heat source tower 13. The heat source cold outlet 904 of the heat pump unit 9 is connected to the return liquid port 133 of the heat source tower through a circulation pump C12. The liquid outlet 134 of the heat source tower is connected to the heat source hot inlet 903 of the heat pump unit 9 to form a circulation. The heat source tower is also provided with an air inlet 131 and an air outlet 132.

[0047] In this way, the heat source tower is a conventional heat pump heat source device, which has good heat exchange effect and is easy to implement. When the heat pump heat source is in the form of a heat source tower, Figure 2 As shown, the heat exchange process of the second-stage LNG secondary cooling and heat exchange structure is that the low-temperature NG of -25°C comes out from the gasification heat exchanger 3, enters the heat pump unit 9 from the low-temperature NG inlet 901, absorbs the heat energy of the heat source tower circulation, becomes 5°C normal temperature NG, and then is transported to the NG user 10. The heat source tower circulation is that under the action of the circulation pump C12, the antifreeze liquid comes out from the heat source cold outlet 904 on the heat pump unit 9, passes through the heat source tower 13, absorbs the low-temperature heat energy in the air, and the temperature rises, and then enters the heat pump unit 9 from the heat source hot inlet 903, thereby completing the cycle. The antifreeze circulating in the heat source tower is a calcium chloride solution or an ethylene glycol solution.

[0048] As an alternative to heat pump heat source, see Figure 3The heat source of the heat pump is the ice storage container 8 in the LNG primary gasification heat exchange structure. The heat source cold outlet 904 of the heat pump unit 9 is connected to the ice inlet B803 of the ice storage container through a crystal promoter 14. The water outlet B804 of the ice storage container is connected to the heat source hot inlet 903 of the heat pump unit 9 through a circulation pump D15 to form a circulation.

[0049] In this way, the ice storage container in the LNG primary gasification heat exchange structure is used as the heat source of the heat pump to form an ice source heat pump, which is not only convenient for implementation, but also can better remove the heat of the ice storage container and better maintain the cold storage effect. Figure 3 As shown, the heat exchange process of the LNG two-stage cooling and heat exchange structure is that the low-temperature NG at -25°C comes out from the gasification heat exchanger 3, enters the heat pump unit 9 from the low-temperature NG inlet 901, absorbs the latent heat of the low-temperature water in the ice storage container 8, becomes 5°C normal temperature NG, and is then transported to the NG user 10. The ice source side cycle is formed when the low-temperature water comes out from the water outlet B804 on the ice storage container 8 under the action of the circulation pump D15, and becomes supercooled water after heat release by the heat pump unit 9, and then undergoes phase change and freezes through the crystal promoter 14, and then enters the ice storage container 8 from the ice inlet B803, thereby completing the cycle.

[0050] The second implementation method, see Figure 4 The difference between this embodiment and the first embodiment is only that the LNG secondary cooling and heat exchange structure is different, while the rest of the structures are the same. In this embodiment, the LNG secondary cooling and heat exchange structure includes a water bath vaporizer 16 and a gas boiler 18; the water bath vaporizer 16 is provided with a low-temperature NG inlet 901, a normal temperature NG outlet 902, a high-temperature hot water inlet 161 and a low-temperature hot water outlet 162; an NG heat exchange channel is provided between the low-temperature NG inlet 901 and the normal temperature NG outlet 902, a water heat exchange channel is provided between the high-temperature hot water inlet 161 and the low-temperature hot water outlet 162, and the water heat exchange channel and the NG heat exchange channel are adjacently arranged and used for heat exchange; the gas boiler 18 is provided with a high-temperature hot water outlet 181, a low-temperature hot water inlet 182 and a gas inlet 183; the low-temperature NG inlet 901 is connected to the low-temperature NG outlet 302 of the gasification heat exchanger 3 by an external pipeline, and the low-temperature hot water outlet 162 is connected to the low-temperature NG outlet 302 of the gasification heat exchanger 3 by an external pipeline. The external pipeline is connected to the low-temperature hot water inlet 182 of the gas boiler 18, and the high-temperature hot water outlet 181 of the gas boiler 18 is externally connected to the high-temperature hot water inlet 161 through a circulation pump E17 to form a circulation; the normal temperature NG outlet 902 of the water bath gasifier 16 is externally connected to the NG output terminal 10 through a three-way valve 19, and the branch interface of the three-way valve 19 is connected to the gas inlet 183 of the gas boiler 18 through a pipeline.

[0051] In this way, when the LNG secondary cooling and heat exchange structure exchanges heat with the water bath vaporizer 16, the heat exchange process is as follows: the low-temperature NG of -25°C comes out from the vaporization heat exchanger 3, enters the water bath vaporizer 16 from the low-temperature NG inlet 901, absorbs the heat energy of the gas boiler hot water circulation, and becomes the normal temperature NG of 5°C, and then passes through the three-way valve 19, a part of which is delivered to the gas boiler 18 to meet its operation consumption, and the other part is delivered to the NG user 10. The gas boiler hot water circulation is that under the action of the circulation pump E17, the high-temperature hot water comes out from the high-temperature hot water outlet 181 on the gas boiler 18, exchanges heat with the low-temperature NG through the water bath vaporizer 16, the temperature drops to become low-temperature hot water, and then returns to the gas boiler 18, thus completing the cycle. In this way, the combustion of NG formed by partial gasification is directly used as a heat source to generate heat, and then the gasified low-temperature NG is converted into normal temperature NG for supply to users through heat exchange in the water bath vaporizer 16, avoiding the problem that traditional LNG gasification equipment is easy to freeze in winter.

[0052] Therefore, in the present invention, after LNG comes out of the LNG storage tank 1, it will undergo a total of two stages of heat exchange. The first stage of heat exchange is carried out in the vaporization heat exchanger 3, and the low-temperature LNG of -162°C absorbs the heat energy released by the ice-making machine cycle and becomes a low-temperature NG of -25°C, and then enters the second stage heat exchange device; the second stage of heat exchange is carried out in the heat pump unit 9 or the water bath vaporizer 16, and the low-temperature NG of -25°C absorbs the heat energy released by the heat pump cycle or the gas boiler hot water cycle and becomes a normal temperature NG of 5°C, and then is delivered to the user. In the second stage of heat exchange, heat pump heat exchange is the main form, and water bath vaporizer heat exchange is only for LNG gasification stations that already have boiler conditions and low natural gas prices.

Claims

1. A two-stage heat exchange LNG gasification system, comprising an LNG storage tank, wherein the low-temperature LNG outlet of the LNG storage tank is connected to the LNG gasification heat exchange structure through an output pipeline equipped with an LNG pump and then connected to the NG output end, characterized in that: The LNG gasification heat exchange structure includes a LNG primary gasification heat exchange structure and a LNG secondary cooling heat exchange structure arranged in series front and back. The LNG primary gasification heat exchange structure is used to realize gasification heat exchange from LNG to low-temperature NG, and the LNG secondary cooling heat exchange structure is used to realize conversion heat exchange from low-temperature NG to normal temperature NG.

2. The two-stage heat exchange LNG gasification system according to claim 1, characterized in that: The LNG primary gasification heat exchange structure includes a gasification heat exchanger, an ice maker and an ice storage container. The gasification heat exchanger is provided with a low-temperature LNG inlet, a low-temperature NG outlet, an antifreeze hot inlet and an antifreeze cold outlet; the LNG inlet and the low-temperature NG outlet are connected through an internal LNG gasification channel, the antifreeze hot inlet and the antifreeze cold outlet are connected through an internal heat exchanger antifreeze heat exchange channel, the LNG gasification channel and the heat exchanger antifreeze heat exchange channel are adjacently arranged and used for heat exchange; the ice maker is provided with an antifreeze hot outlet, an antifreeze cold inlet, an ice outlet and a water inlet, and the antifreeze hot outlet and the antifreeze cold inlet are connected through an internal heat exchanger antifreeze heat exchange channel. The outlets are connected through an internal ice-making machine antifreeze heat exchange channel, and the ice outlet and the water inlet are connected through an internal ice-making heat exchange channel, and the ice-making machine antifreeze heat exchange channel and the ice-making heat exchange channel are adjacently arranged and used for heat exchange; an ice inlet A and a water outlet A are provided on the ice storage container and are connected to the inner cavity; the pipe connected to the antifreeze cold outlet is connected to the antifreeze cold inlet, and the pipe connected to the antifreeze hot outlet is connected to the antifreeze hot inlet after installing a circulating pump A to form a circulation; the pipe connected to the ice outlet is connected to the ice inlet A, and the pipe connected to the water outlet A is connected to the water inlet after installing a circulating pump B to form a circulation.

3. The two-stage heat exchange LNG gasification system according to claim 2, characterized in that: An antifreeze tank is also installed on the pipeline connected from the antifreeze liquid cold outlet to the antifreeze liquid cold inlet.

4. The two-stage heat exchange LNG gasification system according to claim 2, characterized in that: The ice storage container is also provided with an ice inlet B and a water outlet B which are connected to the inner cavity. The ice inlet B and the water outlet B are connected to a heat pump unit with an LNG secondary cooling and heat exchange structure, so that the ice storage container constitutes a heat pump heat source of the heat pump unit.

5. The two-stage heat exchange LNG gasification system according to claim 1, characterized in that: The LNG secondary cooling and heat exchange structure includes a heat pump unit, which is provided with a low-temperature NG inlet, a normal temperature NG outlet, a heat source hot inlet and a heat source cold outlet. An NG channel is connected between the low-temperature NG inlet and the normal temperature NG outlet, a heat pump channel and a heat pump device are connected between the heat source hot inlet and the heat source cold outlet, and the NG channel and the heat pump channel are adjacent to each other and used for heat exchange; the outer side of the low-temperature NG inlet is connected to the low-temperature NG outlet of the gasification heat exchanger through a pipeline, and the outer side of the normal temperature NG outlet is connected to the NG output end through a pipeline; the external pipelines of the heat source hot inlet and the heat source cold outlet are connected to the heat source of the heat pump and constitute a heat pump cycle.

6. The two-stage heat exchange LNG gasification system according to claim 5, characterized in that: The heat source of the heat pump is a heat source tower. The external pipeline of the heat source cold outlet of the heat pump unit is connected to the return liquid port of the heat source tower after passing through a circulation pump C. The external pipeline of the liquid outlet of the heat source tower is connected to the heat source hot inlet of the heat pump unit to form a circulation; the heat source tower is also provided with an air inlet and an air outlet.

7. The two-stage heat exchange LNG gasification system according to claim 5, characterized in that: The heat source of the heat pump is an ice storage container in the LNG primary gasification heat exchange structure. The external pipeline of the heat source cold outlet of the heat pump unit is connected to the ice inlet B of the ice storage container after passing through a crystal promoter. The external pipeline of the water outlet B of the ice storage container is connected to the heat source hot inlet of the heat pump unit after passing through a circulation pump D to form a circulation.

8. The two-stage heat exchange LNG gasification system according to claim 1, characterized in that: The LNG secondary cooling and heat exchange structure includes a water bath vaporizer and a gas boiler; the water bath vaporizer is provided with a low-temperature NG inlet, a normal temperature NG outlet, a high-temperature hot water inlet and a low-temperature hot water outlet; an NG heat exchange channel is provided between the low-temperature NG inlet and the normal temperature NG outlet, a water heat exchange channel is provided between the high-temperature hot water inlet and the low-temperature hot water outlet, and the water heat exchange channel and the NG heat exchange channel are adjacently arranged and used for heat exchange; the gas boiler is provided with a high-temperature hot water outlet, a low-temperature hot water inlet and a gas inlet; the low-temperature NG inlet is externally connected to the low-temperature NG outlet of the gasification heat exchanger through a pipeline, the low-temperature hot water outlet is externally connected to the low-temperature hot water inlet of the gas boiler, and the high-temperature hot water outlet of the gas boiler is externally connected to the high-temperature hot water inlet through a circulation pump E to form a circulation; the normal temperature NG outlet of the water bath vaporizer is externally connected to the NG output end through a three-way valve, and the branch interface of the three-way valve is connected to the gas inlet of the gas boiler through a pipeline.

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