Multi-temperature-range ice slurry cold storage system for liquefied natural gas cold energy cascade recovery

Abstract

The invention relates to the technical field of energy recycling, in particular to a multi-temperature-range ice slurry cold storage system for liquefied natural gas cold energy gradient recycling. Comprising a deep cooling stage unit, an intermediate cooling stage unit and a shallow cooling stage unit which are sequentially connected in series in the flowing direction of liquefied natural gas, and each stage unit integrates the functions of ice slurry preparation, slurry separation, dynamic storage and cooling capacity output and is provided with a monitoring regulation and control assembly; the refrigerant circulating mechanism is connected with each stage of unit to form a closed cycle, light liquid toluene is used as a refrigerant to transfer cooling capacity, and a light refrigerant layer, an ice slurry generation base liquid layer and a heavy liquid perfluorohexane isolation liquid layer are arranged in each stage of ice slurry making tank from top to bottom. According to the system and the method, LNG full-temperature-range cold energy release from-162 DEG C to 0 DEG C is adapted through a multi-stage unit, precise energy and mass matching is realized by utilizing freezing point differences of base liquids with different concentrations, ice blockage is avoided by virtue of an immiscible isolation liquid layer, and the energy utilization rate and the operation stability are improved in combination with refrigerant recovery and a real-time monitoring mechanism.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy recycling, in particular to a multi-temperature-zone ice slurry cold storage system for gradient recovery of liquefied natural gas cold energy. BACKGROUND

[0002] Liquefied natural gas (LNG) is the cleanest fossil energy in the world. During the process of converting from ultra-low temperature liquid state to normal temperature gaseous state natural gas (NG) at atmospheric pressure, the temperature rises from -162℃ to 25℃, and a large amount of cold energy can be released, up to 830kJ / kg. If this part of cold energy can be efficiently recovered and utilized, it can not only reduce the energy cost of liquefied natural gas terminal users, but also reduce carbon emissions and energy consumption of traditional refrigeration, which is an important measure to realize energy gradient utilization and industrial carbon reduction.

[0003] Liquefied natural gas cold energy utilization can be divided into deep cold (-100℃ below), medium cold (-100℃ to -50℃) and shallow cold (0℃ to 0℃) according to temperature zone. Current applications include light hydrocarbon recovery, air separation, organic Rankine cycle power generation, seawater desalination, carbon capture and cold storage, etc. In particular, with the development of centralized cooling technology, the use of liquefied natural gas cold energy for ice slurry cold storage shows good application potential. However, the temperature zone of cold energy released by liquefied natural gas gasification covers different temperature zones of deep cold, medium cold and shallow cold, while the cold source temperature required for ice slurry generation is in the range of -10℃ to 0℃. Direct use of liquefied natural gas gasification process in multiple temperature zones for ice slurry preparation and storage will result in "high quality and low use", and the energy loss will be too large.

[0004] In order to improve the energy efficiency of liquefied natural gas cold energy for ice slurry preparation and storage, an indirect refrigeration system with two-stage heat exchange is generally used, which cools the intermediate coolant by liquefied natural gas, and then exchanges heat between the intermediate coolant and pure water or water solution to produce ice slurry. Such a system has limited potential for reducing energy loss after two heat exchanges, and is prone to ice blockage in the heat exchanger. At the same time, due to the performance limitation of the intermediate coolant, it is not possible to realize the matching extraction of cold energy in multiple temperature zones. If the intermediate heat exchange link is reduced, and liquefied natural gas is used as a cold source gas to directly prepare ice slurry, although the energy loss in the intermediate process can be reduced, the problem of poor adaptability of multiple temperature zones still exists. SUMMARY

[0005] The purpose of the present application is to provide a multi-temperature-zone ice slurry cold storage system for gradient recovery of liquefied natural gas cold energy, which solves the technical problems of single temperature zone, mismatch of energy and quality, low energy utilization rate and ice blockage in the prior art, and realizes efficient gradient recovery and storage of liquefied natural gas cold energy in the whole temperature zone.

[0006] In order to achieve the above purpose, the technical scheme of the present application is as follows: a multi-temperature-zone ice slurry cold storage system for gradient recovery of liquefied natural gas cold energy, comprising: The multi-stage temperature adaptation unit is arranged in series along the LNG flow direction; The refrigerant circulation mechanism is connected with each stage of the temperature adaptation unit and forms a circulation loop for transferring cold energy. The monitoring and control assembly is arranged on each stage of the temperature adaptation unit and the refrigerant circulation mechanism to realize temperature control and energy quality adjustment. The multi-stage temperature adaptation unit adapts the cold energy release process of the LNG in the whole temperature range through the refrigerant circulation mechanism, and realizes the step-by-step extraction and multi-temperature range ice slurry storage of the cold energy of the LNG.

[0007] In another implementation manner of the present application, the multi-stage temperature adaptation unit comprises a deep cooling stage unit, a medium cooling stage unit and a shallow cooling stage unit, the deep cooling stage unit adapts the deep cooling temperature range of the LNG, the medium cooling stage unit adapts the medium cooling temperature range of the LNG, and the shallow cooling stage unit adapts the shallow cooling temperature range of the LNG.

[0008] In another implementation manner of the present application, the deep cooling stage unit comprises a deep cooling stage cooler, a deep cooling stage ice slurry making tank, a deep cooling stage slurry separation tank, a deep cooling stage ice slurry storage tank and a deep cooling heat exchanger connected in sequence; the medium cooling stage unit comprises a medium cooling stage cooler, a medium cooling stage ice slurry making tank, a medium cooling stage slurry separation tank, a medium cooling stage ice slurry storage tank and a medium cooling heat exchanger connected in sequence; and the shallow cooling stage unit comprises a shallow cooling stage cooler, a shallow cooling stage ice slurry making tank, a shallow cooling stage slurry separation tank, a shallow cooling stage ice slurry storage tank and a shallow cooling heat exchanger connected in sequence.

[0009] In another implementation manner of the present application, the refrigerant circulation mechanism comprises a refrigerant medium, a main circulation pipeline, a branch pipeline and a refrigerant recovery pipeline; the main circulation pipeline is communicated with the cooler of each stage of the temperature adaptation unit, the branch pipeline is communicated with the ice slurry making tank of the corresponding stage and the cooler to form an independent refrigerant circulation branch of each stage; and the refrigerant recovery pipeline is connected with the slurry separation tank of each stage and the ice slurry making tank of the corresponding stage to recover the residual refrigerant medium separated in the slurry separation tank.

[0010] In another implementation manner of the present application, the refrigerant medium is liquid toluene, and the liquid toluene forms an independent closed loop circulation between the deep cooling stage ice slurry making tank and the deep cooling stage cooler, between the medium cooling stage ice slurry making tank and the medium cooling stage cooler, and between the shallow cooling stage ice slurry making tank and the shallow cooling stage cooler; and the deep cooling stage ice slurry making tank, the medium cooling stage ice slurry making tank and the shallow cooling stage ice slurry making tank are sequentially provided from top to bottom with a light refrigerant layer, an ice slurry generation base fluid layer and a heavy isolation fluid layer, and the medium of the light refrigerant layer is the liquid toluene.

[0011] In still another implementation manner of the present application, the medium of the heavy isolation fluid layer is liquid perfluorohexane, which is insoluble with the ice slurry generating base fluid of the corresponding level, forming an isolation fluid layer for preventing ice blockage; the ice slurry generating base fluid in the deep cooling level ice slurry tank is potassium formate solution, the ice slurry generating base fluid in the medium cooling level ice slurry tank is calcium chloride solution, and the ice slurry generating base fluid in the shallow cooling level ice slurry tank is sodium chloride solution.

[0012] In still another implementation manner of the present application, the monitoring and regulating assembly comprises temperature sensors, pressure sensors, mass flow meters, check valves and circulating pumps arranged in the branch pipeline, and temperature sensors and pressure sensors arranged on each level ice slurry tank, slurry separation tank and ice slurry storage tank; the check valves are used to block the backflow of the refrigerant medium, the circulating pumps provide power for the circulating flow of the refrigerant medium, and the mass flow meters monitor the refrigerant medium flow in real time and cooperate with the detection data of the temperature sensors and pressure sensors to realize accurate regulation of the refrigerant circulating process.

[0013] In still another implementation manner of the present application, the end of the branch pipeline extending into the bottom of the ice slurry tank is provided with a distributor, which is used to bubble the refrigerant medium, and the refrigerant medium passes through the heavy isolation fluid layer under the action of buoyancy, exchanges heat with the ice slurry generating base fluid layer, and promotes the precipitation of ice crystals.

[0014] In still another implementation manner of the present application, the deep cooling level slurry separation tank, the medium cooling level slurry separation tank and the shallow cooling level slurry separation tank all store the ice slurry and the precipitated light refrigerant of the corresponding level, and are respectively provided with an electric stirring paddle for separating the refrigerant.

[0015] In still another implementation manner of the present application, the deep cooling level ice slurry tank, the medium cooling level ice slurry tank and the shallow cooling level ice slurry tank are all provided with a refrigerant inlet and outlet, an ice slurry outlet, a base fluid return inlet, a base fluid supplement inlet and a precipitated refrigerant return inlet, so as to realize the recycling and supplement of the medium.

[0016] The present application can achieve the following technical effects due to the use of the above technical solutions: 1. The present application accurately covers the whole temperature range of LNG from-162℃ to 0℃ through the cooperative design of the multi-level temperature adaptation unit and the refrigerant circulating mechanism, completely solves the technical bottleneck of single temperature range of traditional LNG cold energy recovery, and realizes the cascade and whole temperature range extraction of cold energy.

[0017] 2. According to the cold energy characteristics of different temperature ranges, the ice slurry generating base fluid and the independent refrigerant circulating branch are matched, so that the cold energy quality and energy demand are adapted, the energy waste of "high quality and low use" is effectively avoided, and the energy quality utilization efficiency of LNG cold energy is greatly improved.

[0018] 3. Through the design of refrigerant closed loop circulation, residual refrigerant recovery and reduction of intermediate heat exchange links, the energy loss in the cold energy transfer process is reduced, and the circulation and reuse of refrigerant medium are realized, which significantly improves the overall energy utilization rate of LNG cold energy recovery and reduces the energy cost.

[0019] 4. With the anti-icing design of heavy isolation fluid layer, monitoring and control components, and independent unitized structure, the problems of ice blockage, medium leakage and parameter fluctuation that are prone to occur in traditional systems are effectively avoided, ensuring long-term continuous and stable operation of the system, and the reliability is strong.

[0020] 5. The system integrates ice slurry preparation, separation, storage and cold energy output functions, has compact structure and simple process, does not need complex auxiliary equipment, and can adapt to various practical application scenarios such as building air conditioning cold storage, thereby providing an efficient and feasible engineering solution for LNG cold energy resource utilization. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the present application or prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can obtain other drawings according to these drawings without creative labor.

[0022] Figure 1 A schematic diagram of a multi-temperature zone ice slurry cold storage system for LNG cold energy cascade recovery; Figure 2 A schematic diagram of a deep cold stage ice slurry tank structure; Figure 3 A schematic diagram of a medium cold stage ice slurry tank structure; Figure 4 A schematic diagram of a shallow cold stage ice slurry tank structure; Figure 5 A heat exchange process of a multi-temperature zone ice slurry cold storage system for LNG cold energy cascade recovery. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. The following description of at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0024] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0025] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the accompanying drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0026] Example 1 like Figure 1 As shown, this embodiment discloses a multi-temperature-range ice slurry cold storage system for the cascade recovery of liquefied natural gas (LNG) cold energy. The system aims to achieve cascaded extraction and stable storage of LNG cold energy across the entire temperature range, solving problems such as single temperature range, energy-mass mismatch, and susceptibility to ice blockage inherent in traditional technologies. Specifically, it includes: Multi-stage temperature adaptation unit: It is set in series along the liquefied natural gas (LNG) flow direction, including cryogenic stage unit A, mesocooling stage unit B and shallow cooling stage unit C. Each stage unit integrates four major functions: ice slurry preparation, slurry separation, dynamic storage and cold energy output, forming an independent and collaborative cold energy recovery module. Refrigerant circulation mechanism: It is connected to each stage of temperature adaptation unit to form a circulation loop, which is responsible for transferring cold energy between liquefied natural gas (LNG) and each stage of unit to ensure the efficiency of cold energy transfer. Monitoring and control components include a temperature sensor 16, a pressure sensor 17, a mass flow meter 18, a check valve 19, and a circulation pump 20, as well as temperature and pressure sensors located on each stage of the ice-making slurry tank, slurry separation tank, and ice slurry storage tank, which are used to achieve precise temperature control and energy quality regulation to ensure stable system operation.

[0027] Through the above-mentioned structural synergy, the multi-stage temperature adaptation unit can adapt to the full temperature range of LNG cold energy release process from -162℃ to 0℃ through the refrigerant circulation mechanism, and finally realize the cascade extraction of LNG cold energy and multi-temperature range ice slurry storage.

[0028] In the embodiment, the deep cooling stage unit A is adapted to cold energy recovery of LNG deep cooling temperature range (-162℃ ~ -100℃), and specifically includes the connected deep cooling stage LNG cooler 1, deep cooling stage ice slurry tank 2, deep cooling stage slurry separation tank 3, deep cooling stage ice slurry storage tank 4 and deep cooling heat exchanger 5. The deep cooling stage ice slurry tank 2 is a cold energy exchange core component, and the tank is divided into three layers from top to bottom: the bottom is heavy liquid perfluorohexane 2-1, the middle is ice slurry generating potassium formate solution with a mass fraction of 42% 2-2, and the top is light liquid toluene 2-3. The tank is also provided with an electric stirring paddle 2-4 and a distributor 2-5, wherein the electric stirring paddle 2-4 is used to accelerate the heat exchange process, and the distributor 2-5 is used to realize uniform distribution of the refrigerant. As shown in Figure 2 , the reserved pipeline interfaces include light liquid toluene inlet 2-6, light liquid toluene outlet 2-7, deep cooling stage ice slurry outlet 2-8, deep cooling stage ice slurry liquid refrigerant recovery inlet and supplementary base liquid inlet 2-9, and precipitated light liquid toluene recovery inlet 2-10. The deep cooling stage slurry separation tank 3 is used to separate the residual refrigerant entrained in the ice slurry, and the tank stores deep cooling ice slurry 3-1 and precipitated light liquid toluene 3-2, and is provided with an electric stirring paddle 3-3 to realize efficient separation of the ice slurry and residual toluene through stirring. The deep cooling stage ice slurry storage tank 4 is used to store the separated deep cooling ice slurry, and is provided with an electric stirring paddle 4-1 to prevent ice slurry from coagulating and agglomerating, and to ensure stable storage state. The deep cooling stage LNG cooler 1 is a primary heat exchange component of LNG and refrigerant, and the deep cooling heat exchanger 5 is used to output the cold energy of the stored deep cooling ice slurry to an external cold use scene, or directly deliver the deep cooling ice slurry to a deep cooling cooling scene application.

[0029] In the embodiment, the medium cooling stage unit B is adapted to cold energy recovery of LNG medium cooling temperature range (-100℃ ~ -40℃), and is designed in a symmetrical manner with the deep cooling stage unit A, and specifically includes the connected medium cooling stage NG cooler 6, medium cooling stage ice slurry tank 7, medium cooling stage slurry separation tank 8, medium cooling stage ice slurry storage tank 9 and medium cooling heat exchanger 10. The medium cooling stage ice slurry tank 7 is divided into three layers from top to bottom: the bottom is heavy liquid perfluorohexane 7-1, the middle is ice slurry generating calcium chloride solution with a mass fraction of 22% 7-2, and the top is light liquid toluene 7-3. The tank is also provided with an electric stirring paddle 7-4 and a distributor 7-5, as shown in Figure 3 , the reserved pipeline interfaces include toluene inlet 7-6, toluene outlet 7-7, ice slurry outlet 7-8, base liquid recovery / supplementary inlet 7-9, and precipitated toluene recovery inlet 7-10. The medium cooling stage slurry separation tank 8 stores medium cooling ice slurry 8-1 and precipitated light liquid toluene 8-2, and is provided with an electric stirring paddle 8-3 to realize refrigerant separation and recovery. The medium cooling stage ice slurry storage tank 9 is provided with an electric stirring paddle 9-1 to stably store the medium cooling ice slurry. The medium cooling stage NG cooler 6 receives the NG flowed out from the deep cooling stage and performs secondary heat exchange, and the medium cooling heat exchanger 10 is responsible for cold energy output of the medium cooling ice slurry.

[0030] In the present embodiment, the shallow cooling stage unit C is adapted to the cold energy recovery of the LNG shallow cooling temperature range (-40°C-0°C), and has the same structure as the deep cooling stage and the medium cooling stage unit, including the shallow cooling stage NG cooler 11, the shallow cooling stage ice slurry tank 12, the shallow cooling stage slurry separation tank 13, the shallow cooling stage ice slurry storage tank 14, and the shallow cooling heat exchanger 15 connected in sequence; wherein the shallow cooling stage ice slurry tank 12 has three layers of liquid from bottom to top: the bottom heavy liquid perfluorohexane 12-1, the middle ice slurry generation sodium chloride solution with a mass fraction of 14% 12-2, and the top light liquid toluene 12-3; the tank is provided with an electric stirring paddle 12-4 and a distributor 12-5, as shown in Figure 4 The reserved pipeline interfaces include a toluene inlet 12-6, a toluene outlet 12-7, an ice slurry outlet 12-8, a base fluid recovery / supplement inlet 12-9, and a precipitated toluene return inlet 12-10; the shallow cooling stage slurry separation tank 13 stores the shallow cooling ice slurry 13-1 and the light liquid toluene 13-2, and is provided with an electric stirring paddle 13-3 to realize the separation and recovery of the refrigerant; the shallow cooling stage ice slurry storage tank 14 is provided with an electric stirring paddle 14-1 for stable storage of the shallow cooling ice slurry; the shallow cooling stage NG cooler 11 receives the NG discharged from the medium cooling stage and completes the final heat exchange, and the shallow cooling heat exchanger 15 is responsible for the cold energy output of the shallow cooling ice slurry.

[0031] Example 2 As shown in Figure 5 Based on the aforementioned multi-temperature zone ice slurry cold energy cascade recovery system for liquefied natural gas, the present embodiment provides a method for accurately adapting to the cold energy release of the LNG full temperature zone and realizing cascade storage, which guarantees the cold energy recovery efficiency and stable operation of the system through step-by-step heat exchange, separation, storage, and regulation, and the specific implementation steps include: S1: The liquefied natural gas (LNG) enters the deep cooling stage LNG cooler 1 through the system inlet and performs countercurrent heat exchange with the light liquid toluene 2-3 from the top of the deep cooling stage ice slurry tank 2: the LNG releases deep cooling temperature range (-162°C-100°C) cold energy during the heat exchange process, and the temperature rises from the initial -162°C to -100°C, and is converted into gaseous natural gas (NG); after absorbing the cold energy, the temperature of the light liquid toluene 2-3 decreases from -45°C to -65°C, which has the ability to transfer cold energy to the ice slurry generation base fluid.

[0032] S2: The light liquid toluene 2-3 after cooling flows from the bottom of the deep cooling ice slurry tank 2 through a pipeline, is uniformly bubbled by the distributor 2-5 in the tank, and under the action of buoyancy, passes through the isolation liquid layer of heavy liquid perfluorohexane 2-1 at the bottom of the tank (to avoid direct contact of toluene with the base liquid to cause local ice blockage of the pipeline), and fully contacts and exchanges heat with the potassium formate solution 2-2 with a mass fraction of 42% in the middle of the tank. In the process of cold energy transfer, the potassium formate solution 2-2 reaches the freezing point and precipitates ice crystals to form deep cooling ice slurry; the light liquid toluene 2-3 after releasing cold energy rises in temperature to the top of the deep cooling ice slurry tank 2 and enters the next round of heat exchange with the deep cooling LNG cooler 1. During the entire heat exchange process, the electric stirring paddle 2-4 in the deep cooling ice slurry tank 2 continuously operates to accelerate the mixing of toluene bubbles and potassium formate solution and improve the heat exchange efficiency; the potassium formate solution 2-2 consumed due to ice crystal precipitation is regularly supplemented through the base liquid inlet and the supplement inlet 2-9 to maintain the stability of the base liquid concentration.

[0033] S3: The deep cooling ice slurry generated by the deep cooling ice slurry tank 2 is transported to the deep cooling slurry separation tank 3 through the ice slurry outlet 2-8. The electric stirring paddle 3-3 in the deep cooling slurry separation tank 3 is started to separate the residual light liquid toluene entrained in the ice slurry through stirring action; the separated residual toluene is transported by a circulating pump and returned to the deep cooling ice slurry tank 2 through the toluene precipitation return inlet 2-10 to realize the recycling of the refrigerant and reduce the medium loss.

[0034] S4: The deep cooling ice slurry after removing the residual toluene through slurry separation flows into the deep cooling ice slurry storage tank 4, and the electric stirring paddle 4-1 in the tank continuously operates to prevent the ice slurry from coagulating and agglomerating and to ensure the stability of the storage state. According to the actual cooling demand, the ice slurry can be indirectly heat exchanged with external systems through the deep cooling heat exchanger 5 to realize cold energy output; or can be directly transported to deep cooling cooling scenes (such as low-temperature storage and industrial deep cooling processes) for direct application to complete the cold storage and cooling closed loop of the deep cooling unit A.

[0035] S5: The NG (temperature -100℃) flowing out from the deep cooling LNG cooler 1 enters the medium cooling NG cooler 6 and exchanges heat with the light liquid toluene 7-3 from the top of the medium cooling ice slurry tank 7: the NG releases medium cooling temperature domain (-100℃~-40℃) cold energy and the temperature rises to -40℃; the light liquid toluene 7-3 after absorbing cold energy, the temperature drops from -20℃ to -35℃. The subsequent ice slurry preparation, refrigerant circulation, ice slurry separation, refrigerant recovery, ice slurry storage and cold energy output process are completely consistent with the deep cooling unit A: the calcium chloride solution 7-2 with a mass fraction of 22% in the medium cooling ice slurry tank 7 precipitates ice crystals to form medium cooling ice slurry, the residual toluene is separated and recovered through the medium cooling slurry separation tank 8, the ice slurry is stored in the medium cooling ice slurry storage tank 9 and the cold energy is output through the medium cooling heat exchanger 10.

[0036] S6: The NG (temperature -40℃) from the middle cold stage NG cooler 6 enters the shallow cold stage NG cooler 11 and exchanges heat with the light liquid toluene 12-3 from the top of the shallow cold stage ice slurry tank 12: the NG releases the cold energy in the shallow cold temperature range (-40℃~0℃), and the temperature rises to 0℃; the light liquid toluene 12-3 absorbs the cold energy, and the temperature drops from -5℃ to -15℃. The subsequent ice slurry preparation, refrigerant circulation, ice slurry separation, refrigerant recovery, ice slurry storage and cold output processes are consistent with the deep cold stage unit A, the middle cold stage unit B: the ice crystals are formed in the shallow cold stage ice slurry by the precipitation of the 14% sodium chloride solution 12-2 in the shallow cold stage ice slurry tank 12, the residual toluene is separated and recovered by the shallow cold stage slurry separation tank 13, and the ice slurry is stored in the shallow cold stage ice slurry storage tank 14 and outputs cold energy through the shallow cold heat exchanger 15.

[0037] During the whole system operation, the temperature sensors 16 and the pressure sensors 17 configured in each stage unit monitor the temperature and pressure parameters of the ice slurry tank, the slurry separation tank, the ice slurry storage tank and the pipeline in real time, to ensure that the working conditions of the deep cold stage, the middle cold stage and the shallow cold stage meet the design requirements; the mass flow meters 18 monitor the refrigerant and base fluid flow in real time, and cooperate with the circulating pumps 20 and the check valves 19 to ensure the stable flow of the medium.

[0038] According to the concentration change of the base fluid in each stage ice slurry tank, the potassium formate, calcium chloride and sodium chloride base fluid is regularly supplemented through the base fluid supplement port to maintain the stable freezing point of the solution; the layer thickness of the heavy liquid perfluorohexane at the bottom of each stage ice slurry tank (to ensure the isolation effect) and the operation state of each electric stirring paddle are regularly checked, and the residual impurities in the pipeline and equipment are cleaned in time to ensure the long-term stable operation of the system.

[0039] Through the above steps, the method realizes the step-by-step recovery of the cold energy of LNG from -162℃ to 0℃, generates three types of ice slurry in deep cold, middle cold and shallow cold, and stores them, which can output cold energy as needed, effectively solving the problems of single temperature range, mismatch of energy and quality, low energy utilization rate and easy ice blockage in traditional LNG cold energy utilization.

[0040] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for some technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A multi-temperature-range ice slurry cold storage system for cascade recovery of cold energy from liquefied natural gas, characterized in that, include: Multi-stage temperature adaptation units are connected in series along the liquefied natural gas flow direction; The refrigerant circulation mechanism is connected to the temperature adaptation unit of each stage to form a circulation loop for transferring cooling capacity. Monitoring and control components are configured on each stage of the temperature adaptation unit and the refrigerant circulation mechanism to achieve temperature control and energy quality regulation; The multi-stage temperature adaptation unit adapts to the full-temperature-range cold energy release process of liquefied natural gas through the refrigerant circulation mechanism, realizing the cascade extraction of cold energy from liquefied natural gas and the storage of ice slurry in multiple temperature ranges.

2. The multi-temperature-range ice slurry cold storage system for cascade recovery of cold energy from liquefied natural gas according to claim 1, characterized in that, The multi-stage temperature adaptation unit includes a cryogenic stage unit (A), a mesocooling stage unit (B), and a shallow cooling stage unit (C). The cryogenic stage unit (A) is adapted to the cryogenic temperature range of liquefied natural gas, the mesocooling stage unit (B) is adapted to the mesocooling temperature range of liquefied natural gas, and the shallow cooling stage unit (C) is adapted to the shallow cooling temperature range of liquefied natural gas.

3. The multi-temperature-range ice slurry cold storage system for cascade recovery of cold energy from liquefied natural gas according to claim 2, characterized in that, The cryogenic stage unit (A) includes a cryogenic stage cooler (1), a cryogenic ice-making slurry tank (2), a cryogenic slurry separator (3), a cryogenic ice slurry storage tank (4), and a cryogenic heat exchanger (5) connected in sequence; the intermediate stage unit (B) includes an intermediate stage cooler (6), an intermediate stage ice-making slurry tank (7), an intermediate stage slurry separator (8), an intermediate stage ice slurry storage tank (9), and an intermediate stage heat exchanger (10) connected in sequence; the shallow stage unit (C) includes a shallow stage cooler (11), a shallow stage ice-making slurry tank (12), a shallow stage slurry separator (13), a shallow stage ice slurry storage tank (14), and a shallow stage heat exchanger (15) connected in sequence.

4. The multi-temperature-range ice slurry cold storage system for cascade recovery of cold energy from liquefied natural gas according to claim 3, characterized in that, The refrigerant circulation mechanism includes a refrigerant medium, a main circulation pipeline, branch pipelines, and a refrigerant recovery pipeline. The main circulation pipeline is connected to the cooler of each temperature adaptation unit, and the branch pipelines connect the cooler to the ice-making slurry tank of the corresponding level, forming an independent refrigerant circulation branch for each level. The refrigerant recovery pipeline connects the slurry separation tank of each level to the ice-making slurry tank of the corresponding level, and is used to recover the residual refrigerant medium separated in the slurry separation tank.

5. The multi-temperature-range ice slurry cold storage system for cascade recovery of cold energy from liquefied natural gas according to claim 4, characterized in that, The refrigerant is liquid toluene, which forms an independent closed-loop circulation between the cryogenic ice-making slurry tank (2) and the cryogenic cooler (1), the intermediate ice-making slurry tank (7) and the intermediate cooler (6), and the shallow ice-making slurry tank (12) and the shallow cooler (11). The cryogenic ice-making slurry tank (2), the intermediate ice-making slurry tank (7), and the shallow ice-making slurry tank (12) are each provided with a light refrigerant layer, an ice-making base liquid layer and a heavy isolation liquid layer from top to bottom. The medium of the light refrigerant layer is the liquid toluene.

6. The multi-temperature-range ice slurry cold storage system for cascade recovery of cold energy from liquefied natural gas according to claim 5, characterized in that, The medium of the heavy isolation liquid layer is liquid perfluorohexane. The liquid perfluorohexane is immiscible with the ice slurry generating base liquid of the corresponding level, forming an isolation liquid layer to prevent ice blockage. The ice slurry generating base liquid in the deep cryogenic ice slurry tank (2) is potassium formate solution (2-2), the ice slurry generating base liquid in the intermediate cryogenic ice slurry tank (7) is calcium chloride solution (7-2), and the ice slurry generating base liquid in the shallow cryogenic ice slurry tank (12) is sodium chloride solution (12-2).

7. The multi-temperature-range ice slurry cold storage system for cascade recovery of cold energy from liquefied natural gas according to claim 4, characterized in that, The monitoring and control components include a temperature sensor (16), a pressure sensor (17), a mass flow meter (18), a check valve (19), and a circulation pump (20) configured on the branch pipeline, as well as temperature sensors and pressure sensors located on each stage of ice-making slurry tank, slurry separation tank, and ice slurry storage tank; wherein, the check valve (19) is used to block the backflow of the refrigerant, the circulation pump (20) provides power for the circulation flow of the refrigerant, and the mass flow meter (18) monitors the flow rate of the refrigerant in real time and works in conjunction with the detection data of the temperature sensor (16) and the pressure sensor (17) to achieve precise control of the refrigerant circulation process.

8. The multi-temperature-range ice slurry cold storage system for cascade recovery of cold energy from liquefied natural gas according to claim 5, characterized in that, The branch pipe is equipped with a distributor (2-5, 7-5, 12-5) at one end of the ice-making slurry tank. The distributor foams the cold medium and, under the action of buoyancy, passes through the heavy isolation liquid layer and exchanges heat with the ice slurry base liquid layer, which promotes the precipitation of ice crystals.

9. A multi-temperature-range ice slurry cold storage system for cascade recovery of cold energy from liquefied natural gas according to claim 1, characterized in that, The cryogenic slurry separator (3), the intermediate slurry separator (8), and the shallow slurry separator (13) all store ice slurry of the corresponding level and precipitated light refrigerant, and are each equipped with an electric stirring paddle for separating the refrigerant.

10. A multi-temperature-range ice slurry cold storage system for cascade recovery of cold energy from liquefied natural gas according to claim 3, characterized in that, The cryogenic ice-making slurry tank (2), the meso-cold ice-making slurry tank (7), and the shallow ice-making slurry tank (12) are all equipped with refrigerant inlet and outlet, ice slurry outlet, base liquid recovery inlet, base liquid replenishment inlet, and precipitated refrigerant recovery inlet, so as to realize the recycling and replenishment of the medium.

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