A multi-temperature cold storage system using LNG cold energy and its control method

Abstract

The present invention discloses a multi-temperature cold storage system using LNG cold energy and a control method thereof. The system includes an LNG heat exchanger, a cold storage hall module and at least one temperature-level cold storage module; the cold storage hall module includes a high-temperature refrigerant zone and a low-temperature refrigerant zone and a plurality of heat exchange pipelines. The circulating refrigerant of the LNG heat exchanger is divided into a plurality of circulating branches by a circulating pump to supply cold to each module and then flows back to the LNG heat exchanger, wherein: the circulating refrigerant of a circulating branch exchanges cold with the first refrigerant, and the other circulating refrigerants are mixed into the second circulating refrigerant heat exchanger and exchange cold with the second refrigerant after exchanging cold in each temperature-level cold storage module. Each module of the present invention has strong independence and high feasibility. It uses a series-parallel mode and phase-change refrigerant to recover LNG cold energy for use in a multi-temperature cold storage, realizing the cascade utilization of LNG cold energy, with low operating costs, and equipped with a refrigeration module to supplement cold energy for the system to ensure stable operation of the system.

Description

Technical Field

[0001] The invention relates to the field of LNG cold energy recovery and utilization, in particular to a multi-temperature cold storage system utilizing LNG cold energy and a control method thereof. Background Art

[0002] The traditional LNG receiving station uses a vaporizer to directly gasify the LNG. This gasification method not only wastes a lot of cold energy, but also requires investment in equipment and operation and maintenance costs, thereby increasing the company's investment. Combining LNG cold energy with cold storage is a feasible technical method, especially for the cascade utilization of cold storages at different temperature levels. How to achieve the combination of LNG cold energy and cold storage under high energy utilization and low cost is a difficult problem that needs to be solved urgently.

[0003] Chinese patent authorization CN106642800B discloses an LNG gasification cold energy cold storage system and its cold energy recovery method, the system includes a latent heat recovery tower, a sensible heat recovery tower, a reheating tower and a refrigeration device. The first-level latent heat recovery tower is mainly used to recover the latent heat in the LNG gasification process, the second-level sensible heat recovery tower is mainly used to recover the sensible heat after LNG gasification, the third-level reheating tower heats the NG to above 5°C, and the refrigeration device includes an ice tank, a refrigeration tank and multiple quick freezing tanks. The first and second levels use suitable phase change refrigerants, which are transported to the cold storage by a booster pump and gasified under the action of the throttling expansion valve of the cold storage to provide cold energy for the cold storage; the third-level reheating tower uses suitable liquid phase refrigerants and low-temperature NG for heat exchange, which can provide cold energy for cold storage food. This invention does not consider complementary connection with electric compression refrigeration and does not consider the load matching of cold energy inside different refrigeration devices. At the same time, since the temperature difference between the refrigerant and the cold storage should not be too large, the system is not applicable to cold storages of various different temperatures.

[0004] Chinese patent authorization CN108151419B discloses a cold storage system for cascade utilization of LNG cold energy, the system includes a pressure stabilizing device, a quick freezing warehouse, a cryogenic warehouse, a refrigerated warehouse, a fresh-keeping warehouse, a gasification device, etc. The invention uses the -65°C LNG cold energy after the secondary cold energy is utilized for quick freezing warehouses, cryogenic warehouses, refrigerated warehouses, and fresh-keeping warehouses to achieve cascade utilization of cold energy. However, the invention is only applicable to the situation where LNG is used after the secondary cold energy is used. At the same time, it is applied to the situation where the cost of LNG receiving stations is too high and the safety risk is high. The LNG exported from the LNG receiving station is high-pressure LNG. If the LNG is passed through cold storages of different temperatures in turn, the cost of the heat exchange equipment is high. And because LNG is a flammable and explosive substance, the system operation and maintenance requirements are extremely high.

[0005] The reference "Design and Analysis of Ship Cold Storage and Air Conditioning System Using LNG Cold Energy" introduces the use of LNG cold energy for low-temperature cold storage, high-temperature cold storage and air conditioning systems, in which low-temperature cold storage, high-temperature cold storage and air conditioning systems are all connected in parallel and equipped with an anti-freezing system to heat LNG. This document only uses LNG cold energy for different cold working conditions, and does not achieve the cascade utilization of cold energy. In some existing technologies, a backup electric refrigeration system is used, and the backup electric refrigeration system only uses one-stage compression to provide cascade cooling for the low-temperature zone and the high-temperature zone. When the cold consumption in the low-temperature zone is reduced, the system COP is low and the energy consumption is high. At the same time, since ethylene glycol does not change phase, only sensible heat is used for cold energy recovery, the circulation volume is large, and the required pump power is large. Summary of the invention

[0006] In view of the above-mentioned problems of difficulty in adapting to cold storages with various different temperatures and high operating costs, the present invention provides a multi-temperature cold storage system and a control method thereof using LNG cold energy, which solves the problem that the system is not applicable to cold storages with various different temperatures due to excessive temperature difference between the refrigerant and the cold storage. The modules of the system have strong independence and high feasibility. In series-parallel mode, phase change refrigerant is used to recover LNG cold energy for use in multi-temperature cold storages, thereby realizing the cascade utilization of LNG cold energy and having low operating costs. A refrigeration module is also provided to supplement cold energy for the system to ensure stable operation of the system.

[0007] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a multi-temperature cold storage system using LNG cold energy, comprising an LNG heat exchanger, a cold storage hall module and at least one temperature-level cold storage module;

[0008] The cold storage hall module includes a high-temperature refrigerant area, a low-temperature refrigerant area and a plurality of heat exchange pipelines, and the heat exchange pipelines include:

[0009] The first heat exchange pipeline includes a high-temperature refrigerant zone, a first refrigerant pump, a first circulating refrigerant heat exchanger, and a low-temperature refrigerant zone in sequence according to the flow direction of the first refrigerant;

[0010] The second heat exchange pipeline includes a high-temperature refrigerant zone, a second refrigerant pump, a second circulating refrigerant heat exchanger, and a low-temperature refrigerant zone in sequence according to the flow direction of the second refrigerant;

[0011] The circulating refrigerant of the LNG heat exchanger is divided into several circulating branches by a circulating pump to supply cooling to each module and then flows back to the LNG heat exchanger, wherein:

[0012] A circulation branch passes through the first circulating refrigerant heat exchanger to exchange cold between the circulating refrigerant and the first secondary refrigerant;

[0013] The other several circulation branches corresponding to at least one temperature-level cold storage module pass through the second circulating refrigerant heat exchanger. After the circulating refrigerant exchanges cold in each temperature-level cold storage module, it is mixed and enters the second circulating refrigerant heat exchanger to exchange cold with the second coolant.

[0014] As a further improvement of the present invention, the heat exchange pipeline also includes a third heat exchange pipeline, which includes a low-temperature refrigerant area, a third refrigerant pump, at least one cold storage hall and / or production workshop, and a high-temperature refrigerant area in sequence according to the flow direction of the third refrigerant.

[0015] As a further improvement of the present invention, the system further includes a refrigeration module, the refrigeration module includes at least one temperature-stage refrigeration group, the first temperature-stage refrigeration group includes a first compressor, a first condenser, a first expansion valve, and a first refrigeration refrigerant circulation barrel that are cyclically connected in sequence, and the first refrigeration refrigerant circulation barrel is connected to the fourth heat exchange pipeline of the cold storage hall module through a first refrigeration refrigerant circulation pump;

[0016] The fourth heat exchange pipeline includes a high-temperature refrigerant area, a fourth refrigerant pump, a first refrigeration refrigerant heat exchanger, and a low-temperature refrigerant area in sequence according to the flow direction of the fourth refrigerant, and the first temperature-level refrigerant of the first refrigeration refrigerant circulation barrel exchanges cold with the fourth refrigerant when flowing through the first refrigeration refrigerant heat exchanger.

[0017] As a further improvement of the present invention, the first refrigeration refrigerant circulation barrel is also connected to the first temperature-level cold storage module through the first refrigeration refrigerant circulation pump, the first temperature-level cold storage module includes a third circulation refrigerant heat exchanger, a second refrigeration refrigerant heat exchanger, a first cold storage refrigerant circulation barrel, a first cold storage circulation pump, and a first temperature-level cold storage, and the first cold storage refrigerant circulation barrel is connected to the first temperature-level cold storage through the first cold storage circulation pump to form a pipeline for the first cold storage refrigerant to release cold energy;

[0018] The third circulating refrigerant heat exchanger and the first cold storage refrigerant circulating barrel form a pipeline for circulating refrigerant in the first cold storage, wherein the circulating refrigerant in one circulating branch flows through the third circulating refrigerant heat exchanger so that the circulating refrigerant exchanges cold with the refrigerant in the first cold storage;

[0019] The second refrigeration refrigerant heat exchanger and the first cold storage refrigerant circulation barrel constitute a pipeline for the circulation of the first cold storage refrigerant. The first temperature level refrigeration refrigerant in the first refrigeration refrigerant circulation barrel flows through the second refrigeration refrigerant heat exchanger to exchange cold with the first cold storage refrigerant.

[0020] As a further improvement of the present invention, the at least one temperature-level cold storage module also includes a second temperature-level cold storage module with a lower temperature than the first temperature level, the second temperature-level cold storage module includes a fourth circulating refrigerant heat exchanger, a third refrigeration refrigerant heat exchanger, a second cold storage refrigerant circulation barrel, a second cold storage circulation pump, and a second temperature-level cold storage, and the second cold storage refrigerant circulation barrel is connected to the second temperature-level cold storage through the second cold storage circulation pump to form a pipeline for the second cold storage refrigerant to release cold energy;

[0021] The fourth circulating refrigerant heat exchanger and the second cold storage refrigerant circulating barrel constitute a pipeline for circulating refrigerant in the second cold storage, wherein the circulating refrigerant of a circulating branch flows through the fourth circulating refrigerant heat exchanger to exchange cold with the circulating refrigerant in the second cold storage.

[0022] As a further improvement of the present invention, the at least one temperature-stage refrigeration group further includes a second temperature-stage refrigeration group, the second temperature-stage refrigeration group includes a second compressor, a second condenser, a second expansion valve, and a second refrigeration refrigerant circulation barrel which are cyclically connected in sequence, wherein the first refrigeration refrigerant circulation barrel is connected to the second condenser via a first refrigeration refrigerant circulation pump;

[0023] The third refrigeration refrigerant heat exchanger and the second cold storage refrigerant circulation barrel constitute a pipeline for the circulation of the second cold storage refrigerant. The second refrigeration refrigerant circulation barrel constitutes a pipeline for the circulation of the second temperature-level refrigeration refrigerant through the second refrigeration refrigerant circulation pump and the third refrigeration refrigerant heat exchanger to exchange cold between the second cold storage refrigerant and the second temperature-level refrigeration refrigerant.

[0024] As a further improvement of the present invention, an overflow partition is provided between the high-temperature refrigerant zone and the low-temperature refrigerant zone.

[0025] As a further improvement of the present invention, the fourth heat exchange pipeline and each heat exchanger in at least one temperature-stage cold storage module are respectively located above the heat exchanger and a heat exchanger circulation barrel is provided for connecting a circulation branch and / or a refrigeration group. When each circulating refrigerant and / or refrigeration refrigerant enters the heat exchanger circulation barrel, the liquid refrigerant enters the corresponding heat exchanger below due to gravity, and returns to the heat exchanger circulation barrel above after vaporization.

[0026] On the other hand, the present invention also adopts the following technical solution: a multi-temperature cold storage control method using LNG cold energy, using the multi-temperature cold storage system using LNG cold energy as described above to perform the following steps:

[0027] The LNG heat exchanger uses the LNG flowing through it to exchange cold with the circulating refrigerant. The LNG heats up and gasifies into NG to enter the next process. The circulating refrigerant with LNG cold energy is divided into several circulating branches after passing through the cold storage hall module and at least one temperature-grade cold storage module, and then flows back to the LNG heat exchanger to form a cycle.

[0028] Control one of the circulation branches to flow through the first heat exchange pipeline of the cold storage hall module and be located at the first circulating refrigerant heat exchanger so that the circulating refrigerant exchanges cold with the first secondary refrigerant;

[0029] Control the other several circulation branches to flow through the circulating refrigerant heat exchanger of at least one temperature-level cold storage module respectively, so that the circulating refrigerant exchanges cold with the cold storage refrigerant of each temperature level respectively, the circulating refrigerant after the LNG cold energy is utilized is mixed and enters the second circulating refrigerant heat exchanger of the second heat exchange pipeline, the second refrigerant further recovers the residual cold of the circulating refrigerant, and the circulating refrigerant passing through the second circulating refrigerant heat exchanger is mixed with the circulating refrigerant passing through the first circulating refrigerant heat exchanger and flows back to the LNG heat exchanger to obtain new LNG cold energy;

[0030] When the LNG cold energy supply of the circulating refrigerant is insufficient, the first refrigerant circulating pump is started to circulate the first temperature-level refrigerant of the first refrigerant circulating barrel to the first refrigerant heat exchanger and the second refrigerant heat exchanger, respectively, to exchange cold with the fourth refrigerant and the first cold storage refrigerant to supplement cold energy;

[0031] Start the refrigerant circulation pumps of other temperature-level refrigeration groups, and circulate the refrigerant in the refrigerant circulation barrels of each temperature-level refrigeration group to the refrigerant heat exchangers of at least one temperature-level cold storage module, and exchange cold with the cold storage refrigerant of each temperature-level cold storage module to supplement cold energy.

[0032] As a further improvement of the present invention, the control method further comprises the following steps:

[0033] When the LNG cold energy is insufficient to supply the cold storage hall module and at least one temperature-grade cold storage module at the same time, the priority of the LNG cold energy of the circulating refrigerant to supply cold energy to each module is: low-temperature-grade cold storage module > high-temperature-grade cold storage module > cold storage hall module.

[0034] As a further improvement of the present invention, the control method further comprises the following steps:

[0035] In the cold storage hall module, the second heat exchange pipeline is started first, and the second refrigerant is used to recover the residual cold of the circulating refrigerant after the cold storage module is cooled, so as to supplement the cold energy for the low-temperature refrigerant area; when the residual cold recovered in the second heat exchange pipeline is insufficient, the first heat exchange pipeline is started first, and the first refrigerant is used to absorb the LNG cold energy of the circulating refrigerant, so as to supplement the cold energy for the low-temperature refrigerant area; when the first heat exchange pipeline does not absorb enough LNG cold energy, the fourth heat exchange pipeline is opened, and the fourth refrigerant is used to exchange cold with the first temperature-level refrigeration refrigerant, so as to supplement the cold energy for the low-temperature refrigerant area;

[0036] In at least one temperature-level cold storage module, the pipelines for exchanging cold between the cold storage refrigerant and the circulating refrigerant of the circulation branch are preferentially started, and the LNG cold energy of the circulating refrigerant is used to supplement it; when the LNG cold energy is insufficient, the pipelines for exchanging cold with at least one group of temperature-level refrigeration groups are opened, and the cold energy of the refrigeration refrigerants of each temperature level is absorbed by the refrigerants of each temperature level cold storage to supplement it.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] Each module of the present invention has strong independence and high feasibility. By using the series-parallel mode, the cascade utilization of LNG cold energy is realized while each cold module can operate independently, and a refrigeration module is equipped to supplement cold energy for the system to ensure stable operation of the system.

[0039] The present invention has low operating costs, uses phase change refrigerant to recover LNG cold energy for use in multi-temperature cold storage, and adopts cascade utilization to reduce the system refrigerant circulation volume; at the same time, it is equipped with high and low temperature electric compression refrigeration systems. When the LNG cold energy supply is insufficient, the high COP is used to provide cooling for the cold module.

[0040] The present invention realizes precise control of LNG cold energy by ensuring that the circulating refrigerant is in a full liquid state in the heat exchangers of the cold storage modules at each temperature level, and by coordinating the liquid level control and outlet pressure control of the circulating refrigerant circulating barrel, precise control of the gasification amount and gasification temperature of the circulating refrigerant is realized. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the technical solution, the drawings required for use in the implementation will be briefly introduced below. Obviously, the drawings described below are only some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0042] Figure 1 A schematic diagram of the structure of a multi-temperature cold storage system according to one embodiment of the present invention;

[0043] Figure 2 This is a schematic diagram of the structure of a multi-temperature cold storage system according to another embodiment of the present invention. DETAILED DESCRIPTION

[0044] In order to enable a clear and complete understanding of the technical solution, the present invention is further described in conjunction with the embodiments and drawings. Obviously, the described embodiments are only some embodiments of the present invention, and all other embodiments obtained by technicians in the relevant field without making creative work are within the scope of protection of the present invention.

[0045] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0046] It should also be understood that the terms used in this specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the specification of the present invention and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0047] It should be further understood that the term "and / or" used in the present description and the appended claims refers to and includes any and all possible combinations of one or more of the associated listed items.

[0048] The embodiment of the present invention provides a multi-temperature cold storage system using LNG cold energy, such as Figure 1 As shown, it includes an LNG heat exchanger 101, a cold storage hall module and at least one temperature-grade cold storage module.

[0049] The LNG (also called liquefied natural gas, the critical temperature between LNG gas and liquid under normal pressure is -162°C) output from the receiving station enters the LNG heat exchanger 101, and exchanges cold with the circulating refrigerant of this embodiment, so that the circulating refrigerant flowing through the LNG heat exchanger obtains LNG cold energy. After the cold exchange, the LNG is heated and vaporized into NG and enters the NG heat exchanger 102 for the next cold energy recovery or utilization process, thereby realizing the cascade recovery and utilization of cold energy.

[0050] It should be noted that the present invention does not impose any form of restriction on the LNG transportation pipeline and the energy exchange between it and the circulating refrigerant. The technicians can set it according to actual needs, as long as it can be achieved that the circulating refrigerant can have LNG cold energy through the LNG heat exchanger. At the same time, the present invention does not impose any form of restriction on the means and principles of energy exchange achieved by the following various heat exchangers. The technicians can set it according to actual needs. As long as the refrigerants from different pipelines enter the heat exchanger to achieve cooling or energy exchange, it will not be elaborated here.

[0051] Further explanation: the circulating refrigerant, cold storage refrigerant, and refrigeration refrigerant of the present invention include but are not limited to all phase change refrigerants such as ammonia, CO2, freons, and light hydrocarbons, and the refrigerant includes but is not limited to ethylene glycol aqueous solution, sodium chloride aqueous solution, calcium chloride aqueous solution, water and other liquid refrigerants. This embodiment is illustrated by taking CO2 as the circulating refrigerant, and taking 50% ethylene glycol aqueous solution as the refrigerant as an example. Other refrigerants are selected according to actual needs, among which freon refrigerants include but are not limited to any one of R23, R507, and R410a, and light hydrocarbon refrigerants include but are not limited to any one of ethane, propane, ethylene, and propylene.

[0052] like Figure 1 As shown, the circulating refrigerant of this embodiment has LNG cold energy after passing through the LNG heat exchanger, and is divided into several circulating branches after passing through the circulating pump 103, respectively flowing through the cold storage hall module, at least one temperature-level cold storage module, and then returning to the LNG heat exchanger 101 to form a cycle;

[0053] The cold storage hall module includes a high-temperature refrigerant area 201 and a low-temperature refrigerant area 202 and a plurality of heat exchange pipelines, wherein the heat exchange pipelines include:

[0054] The first heat exchange pipeline includes a high-temperature refrigerant zone 201, a first refrigerant pump 203, a first circulating refrigerant heat exchanger 204, and a low-temperature refrigerant zone 202 in sequence according to the flow direction of the first refrigerant; the first heat exchange pipeline is driven by the first refrigerant pump 203 to pump the first refrigerant of the high-temperature refrigerant zone 201 to the first circulating refrigerant heat exchanger 204 to exchange cold with the circulating refrigerant to obtain LNG cold energy and then enter the low-temperature refrigerant zone 202;

[0055] The second heat exchange pipeline includes a high-temperature refrigerant zone 201, a second refrigerant pump 205, a second circulating refrigerant heat exchanger 206, and a low-temperature refrigerant zone 202 in sequence according to the flow direction of the second refrigerant; the second heat exchange pipeline is driven by the second refrigerant pump 205 to pump the second refrigerant of the high-temperature refrigerant zone 201 to the second circulating refrigerant heat exchanger 206 to exchange with the circulating refrigerant and then enter the low-temperature refrigerant zone 202;

[0056] Furthermore, the circulating refrigerant of the LNG heat exchanger 101 is divided into several circulating branches through the circulating pump 103 to supply cooling to each module and then flows back to the LNG heat exchanger 101. This embodiment is illustrated by taking two temperature-level cold storage modules as an example, namely, a high-temperature cold storage module and a low-temperature cold storage module. Similarly, the circulating refrigerant is divided into a first circulating branch flowing through the cold storage hall module, a second circulating branch flowing through the high-temperature cold storage module, and a third circulating branch flowing through the low-temperature cold storage module through the circulating pump 103;

[0057] Specifically, the first circulation branch passes through the first circulation refrigerant heat exchanger 204 to exchange cold between the circulation refrigerant and the first secondary refrigerant, so that the first secondary refrigerant of the first heat exchange pipeline absorbs LNG cold energy and enters the low-temperature secondary refrigerant area 202 to replenish cold energy;

[0058] Specifically, the second circulation branch and the third circulation branch are respectively exchanged through the third circulation refrigerant heat exchanger 304 of the high-temperature cold storage module and the fourth circulation refrigerant heat exchanger 404 of the low-temperature cold storage module, and the cold storage refrigerants of the third circulation refrigerant heat exchanger 304 and the fourth circulation refrigerant heat exchanger 404 absorb the LNG cold energy of the circulation refrigerant and replenish the cold energy to the respective temperature-level cold storages;

[0059] The second circulation branch and the third circulation branch respectively pass through the high-temperature cold storage module and the low-temperature cold storage module, and then merge and connect to the second circulation refrigerant heat exchanger 206. The circulating refrigerant after cooling flows through the second circulation refrigerant heat exchanger 206 to exchange cooling with the second refrigerant. The second circulation refrigerant heat exchanger 206 mainly recovers the residual cooling of the low-temperature gas CO2 after the cold energy is utilized by the high-temperature cold storage module and the low-temperature cold storage module, so as to realize the cascade utilization of cold energy.

[0060] In this embodiment, when the LNG cold energy of the cold storage hall module is sufficient, the cold energy of the second circulation branch and the third circulation branch is preferentially used to supply through the second circulation refrigerant heat exchanger 206; when the LNG cold energy is insufficient, the first circulation branch is further opened, and the circulating refrigerant that is not used for LNG cold exchange with the first refrigerant in the first circulation refrigerant heat exchanger 204 to supplement the cold energy. In actual scenarios, in the case of further insufficient LNG cold energy, the cold storage hall module can also be set to add a heat exchange pipeline to exchange cold with the refrigeration module to ensure the supply of cold energy. This solution is explained through the following embodiments.

[0061] Through the above system, the cascade utilization of LNG cold energy is realized. Each module adopts a mixed mode of series and parallel connection. At the same time, each cold module can operate independently. It is suitable for cold storages with various temperatures and has a high cold energy utilization rate.

[0062] In an optional embodiment, the cold storage hall module further includes a third heat exchange pipeline, which includes a low-temperature refrigerant area 202, a third refrigerant pump 207, at least one cold storage hall and / or production workshop 208, and a high-temperature refrigerant area 201 in sequence according to the flow direction of the third refrigerant; the third heat exchange pipeline is driven by the third refrigerant pump 207 to pump the third refrigerant in the low-temperature refrigerant area 202 to one or more cold storage halls and / or production workshops 208, and release cold energy in the cold storage hall and / or production workshop 208. In addition to being applicable to halls and workshops, the cold energy release can also be other applicable cold environments, which is not limited in this embodiment. After the cold energy release, the third refrigerant enters the high-temperature refrigerant area 201;

[0063] That is to say, the third heat exchange pipeline and other heat exchange pipelines form a refrigerant circulation flow between the high-temperature refrigerant zone 201 and the low-temperature refrigerant zone 202. It should be noted that the first refrigerant, the second refrigerant, and the third refrigerant in this embodiment refer to the same substance, namely, ethylene glycol aqueous solution. The differentiated descriptions are used to better illustrate the refrigerant circulation flow paths of different heat exchange pipelines.

[0064] In order to further adapt to different cold working conditions and meet cold demand, when the supply of LNG cold energy is insufficient, another embodiment of the present invention further provides a multi-temperature cold storage system using LNG cold energy on the basis of the above embodiment, the system also includes a refrigeration module, the refrigeration module includes at least one group of temperature-level refrigeration groups, the refrigeration group preferably uses an electric compression refrigeration system to achieve refrigeration, and one or more groups of temperature-level refrigeration groups are used to further supplement cold energy to ensure stable operation of the system. The refrigeration module can be provided with an independent group of temperature-level refrigeration groups to supply cold to the cold storage hall module and the cold storage module respectively. When facing multiple temperature-level cold storage modules, multiple groups of different temperature-level refrigeration groups can be correspondingly provided to supply cold to the cold storage modules at corresponding temperature levels.

[0065] For better understanding, this embodiment takes an independent temperature-level refrigeration group as an example to provide cold energy supplementary supply, specifically:

[0066] refer to Figure 1 , the first temperature-level refrigeration group includes a first compressor 501, a first condenser 502, a first expansion valve 503, and a first refrigeration refrigerant circulation barrel 504, which are cyclically connected in sequence. It can be understood by those skilled in the art that the refrigeration compressor, condenser, expansion valve, and refrigerant circulation barrel are connected in a conventional manner to achieve refrigeration, and the operation means of the refrigeration refrigerant are connected in a conventional manner to achieve refrigeration. In this regard, this embodiment does not impose any form of limitation on the method of achieving refrigeration, as long as the refrigeration refrigerant in the refrigeration refrigerant circulation barrel can have corresponding cold energy.

[0067] Furthermore, the first refrigeration refrigerant circulation barrel 504 is connected to the fourth heat exchange pipeline of the cold storage hall module through the first refrigeration refrigerant circulation pump 505;

[0068] The fourth heat exchange pipeline includes a high-temperature refrigerant area 201, a fourth refrigerant pump 209, a first refrigeration refrigerant heat exchanger 210, and a low-temperature refrigerant area 202 in sequence according to the flow direction of the fourth refrigerant. The fourth heat exchange pipeline is driven by the fourth refrigerant pump 209 to pump the fourth refrigerant in the high-temperature refrigerant area 201 to the first refrigeration refrigerant heat exchanger 210. The first temperature-level refrigerant of the first refrigeration refrigerant circulation barrel 504 exchanges cold with the fourth refrigerant when flowing through the first refrigeration refrigerant heat exchanger 210. After the cold exchange, the fourth refrigerant enters the low-temperature refrigerant area 202 to replenish cold energy for the low-temperature refrigerant area 202.

[0069] In an optional embodiment, the first temperature-level refrigeration group is provided with another branch line to provide cooling for the cold storage module while supplementing the cold energy of the cold storage hall module. Specifically:

[0070] The first refrigeration refrigerant circulation barrel 504 is also connected to the first temperature-level cold storage module through the first refrigeration refrigerant circulation pump 505. The first temperature-level cold storage module includes a third circulation refrigerant heat exchanger 304, a second refrigeration refrigerant heat exchanger 305, a first cold storage refrigerant circulation barrel 301, a first cold storage circulation pump 303, and a first temperature-level cold storage 302. The first cold storage refrigerant circulation barrel 301 is connected to the first temperature-level cold storage 302 through the first cold storage circulation pump 303 to form a pipeline for the first cold storage refrigerant to release cold energy. The cold energy of the first cold storage refrigerant is utilized and then flows back to the first cold storage refrigerant circulation barrel 301, and then replenishes cold energy from the circulating refrigerant and / or the first temperature-level refrigeration refrigerant through the third circulation refrigerant heat exchanger 304 and / or the second refrigeration refrigerant heat exchanger 305.

[0071] Furthermore, the third circulating refrigerant heat exchanger 304 and the first cold storage refrigerant circulating barrel 301 constitute a pipeline for circulating the refrigerant in the first cold storage, wherein the circulating refrigerant of one circulating branch (the second circulating branch) flows through the third circulating refrigerant heat exchanger 304 so that the circulating refrigerant exchanges cold with the refrigerant in the first cold storage;

[0072] Furthermore, the second refrigeration refrigerant heat exchanger 305 and the first cold storage refrigerant circulation barrel 301 constitute a pipeline for the circulation of the first cold storage refrigerant, and the first temperature level refrigeration refrigerant of the first refrigeration refrigerant circulation barrel 504 flows through the second refrigeration refrigerant heat exchanger to exchange cold with the first cold storage refrigerant.

[0073] In order to better understand the multi-temperature cold storage system of the present invention, the following uses two temperature-level cold storage modules and refrigeration groups for example, including a high-temperature cold storage module (equivalent to the first temperature-level cold storage module in the above embodiment), a low-temperature cold storage module (a second temperature-level cold storage module of a lower temperature level relative to the first temperature-level cold storage module), a high-temperature refrigeration group (equivalent to the first temperature-level refrigeration group in the above embodiment), and a low-temperature refrigeration group (a second temperature-level refrigeration group of a lower temperature level relative to the first temperature-level refrigeration group). Based on this, an embodiment of the present invention, on the basis of one or more of the above embodiments, provides a multi-temperature cold storage system using LNG cold energy, and also includes a second temperature-level cold storage module and a second temperature-level refrigeration group.

[0074] Specifically, refer to Figure 1 The second temperature-level cold storage module includes a fourth circulating refrigerant heat exchanger 404, a third refrigeration refrigerant heat exchanger 405, a second cold storage refrigerant circulation barrel 401, a second cold storage circulation pump 403, and a second temperature-level cold storage 402. The second cold storage refrigerant circulation barrel 401 is connected to the second temperature-level cold storage 402 through the second cold storage circulation pump 403 to form a pipeline for the second cold storage refrigerant to release cold energy; the cold energy of the second cold storage refrigerant is utilized and then flows back to the second cold storage refrigerant circulation barrel 401, and then replenishes cold energy from the circulating refrigerant and / or the first temperature-level refrigeration refrigerant through the fourth circulating refrigerant heat exchanger 404 and / or the third refrigeration refrigerant heat exchanger 405.

[0075] The second temperature-level refrigeration group includes a second compressor 506, a second condenser 507, a second expansion valve 508, and a second refrigeration refrigerant circulation barrel 509, which are cyclically connected in sequence. The description of the refrigeration group to achieve refrigeration has been described in the above embodiment and will not be repeated. The second condenser 507 of the second temperature-level refrigeration group can also be provided with cold energy by the first temperature-level refrigeration group, and the first refrigeration refrigerant circulation barrel 504 is connected to the second condenser 507 through the first refrigeration refrigerant circulation pump 505.

[0076] That is to say, in the first refrigeration refrigerant circulation barrel 504 of the first temperature-level refrigeration group, the first refrigeration refrigerant can be divided into three branches for refrigeration and cold supply. One branch exchanges cold with the fourth heat exchange pipeline of the cold storage hall module, the second branch replenishes cold energy to the first temperature-level cold storage module, and the third branch supplies cold energy to the second temperature-level refrigeration group of a lower temperature level. The second temperature-level refrigeration group prepares lower temperature cold energy, and the lower temperature cold energy is supplied to the second temperature-level cold storage module of a lower temperature level.

[0077] Furthermore, the fourth circulating refrigerant heat exchanger 404 and the second cold storage refrigerant circulating barrel 401 constitute a pipeline for circulating the refrigerant in the second cold storage, wherein the circulating refrigerant of a circulating branch (the third circulating branch) flows through the fourth circulating refrigerant heat exchanger 404 to exchange cold with the circulating refrigerant in the second cold storage.

[0078] The third refrigeration refrigerant heat exchanger 405 and the second cold storage refrigerant circulation barrel 401 constitute a pipeline for the circulation of the second cold storage refrigerant. The second refrigeration refrigerant circulation barrel 509 constitutes a pipeline for the circulation of the second temperature-level refrigeration refrigerant through the second refrigeration refrigerant circulation pump 510 and the third refrigeration refrigerant heat exchanger 405. The two pipelines exchange the second cold storage refrigerant with the second temperature-level refrigeration refrigerant at the third refrigeration refrigerant heat exchanger 405.

[0079] Through the above system description, those skilled in the art can understand that the multi-temperature-level cold storage system can also set more temperature-level cold storages according to the actual cooling demand, and set more temperature-level refrigeration groups accordingly, and give priority to using the LNG cold energy (i.e., several circulation branches) of the circulating refrigerant for cooling. When the LNG cold energy is insufficient, a multi-temperature-level refrigeration group is used to supplement the cold energy. In the multi-temperature-level refrigeration group, the cold energy of the relatively high-temperature-level refrigeration group is used to work for the condenser of the relatively low-temperature-level refrigeration group, and the cold energy is further supplemented for the low-temperature-level refrigeration group to prepare lower-temperature cold energy to meet the cooling demand of the lower-temperature-level cold storage modules, so that the cold energy is utilized in a tiered manner with high utilization rate and high efficiency.

[0080] In an optional embodiment, an overflow baffle is provided between the high-temperature refrigerant zone 201 and the low-temperature refrigerant zone 202. The height of the overflow baffle is set according to the edge height of the high-temperature refrigerant zone 201 and the low-temperature refrigerant zone 202 (generally a water pool in actual application), preferably 0.5m-1m lower than the edge height of the two water pools, so that the two water pools can overflow each other and ensure the water level of the water pools.

[0081] In an optional embodiment, the fourth heat exchange pipeline and each heat exchanger in at least one temperature-stage cold storage module are respectively located above the heat exchanger, and a heat exchanger circulation barrel is provided above the heat exchanger for connecting a circulation branch and / or a refrigeration group. When each circulating refrigerant and / or refrigeration refrigerant enters the heat exchanger circulation barrel, the liquid refrigerant enters the corresponding heat exchanger below due to gravity, and returns to the heat exchanger circulation barrel above after vaporization.

[0082] Further explanation based on the above embodiments: Figure 2 The heat exchangers of this embodiment include a first refrigeration refrigerant heat exchanger 210, a second refrigeration refrigerant heat exchanger 305, a third refrigeration refrigerant heat exchanger 405, a third circulating refrigerant heat exchanger 304, and a fourth circulating refrigerant heat exchanger 404. Corresponding heat exchanger circulation barrels are placed above some of the heat exchangers, which are correspondingly connected to the circulating refrigerant and / or the refrigeration refrigerant. The heat exchanger circulation barrels include a first refrigeration refrigerant heat exchanger circulation barrel 2101, a second refrigeration refrigerant heat exchanger circulation barrel 3051, a third refrigeration refrigerant heat exchanger circulation barrel 4051, a third circulating refrigerant heat exchanger circulation barrel 3041, and a fourth circulating refrigerant heat exchanger circulation barrel 4041.

[0083] When the corresponding refrigerant enters the heat exchanger circulation barrel, due to the effect of gravity, the liquid refrigerant enters the heat exchanger located below. After cooling in the heat exchanger, the liquid refrigerant will heat up and vaporize. The vaporized gaseous refrigerant returns to the heat exchanger circulation barrel above and continues to participate in the circulation.

[0084] This embodiment separates the refrigerant gas and liquid by gravity, and gives priority to using liquid refrigerant for energy exchange, which effectively improves the conversion efficiency of cold energy. Similarly, the circulation barrel of this embodiment is also applicable to the refrigerant circulation barrel in the refrigeration group. The refrigerant enters the condenser only after being pressurized to high temperature and high pressure by the compressor, and after cooling and liquefaction, it is throttled and expanded by the expansion valve to be a low-temperature gas-liquid mixture and enters the refrigerant circulation barrel. Several branch outlets of the refrigerant circulation barrel are set at the bottom, driven by the refrigerant circulation pump, and the liquid refrigerant is given priority to supply cold to the outside, and after gasification, it returns to the refrigerant circulation barrel and enters the compressor to participate in refrigeration.

[0085] Obviously, the above embodiments are only used to illustrate the system structure of the present invention, and are not intended to limit the scope of protection of the present invention. Without departing from the concept of the present invention, those skilled in the art can adjust the above system structure so that the present invention can be applied to more specific application scenarios.

[0086] In order to better understand the above system structure, the multi-temperature cold storage system is described below in conjunction with an embodiment, but it is not intended to limit the technical solution of the embodiment of the present invention. Specifically:

[0087] An embodiment of the present invention provides a multi-temperature cold storage control method using LNG cold energy, using a multi-temperature cold storage system using LNG cold energy as in one or more of the above embodiments to perform the following steps:

[0088] The LNG heat exchanger 101 uses the LNG flowing through to exchange cold with the circulating refrigerant, and the LNG is heated up and gasified into NG to enter the next process; in some embodiments, the NG is returned to the receiving station after heat exchange with the cold water air conditioner through the NG heat exchanger 102, and the NG heat exchanger 102 uses the high-temperature water from the cold water air conditioner to reheat the NG while further recovering the remaining cold of the NG for the cold water air conditioning cycle, thereby realizing the cascade utilization of cold energy.

[0089] Furthermore, the circulating refrigerant with LNG cold energy is divided into several circulating branches after passing through the circulating pump 103, respectively flowing through the cold storage hall module and at least one temperature-grade cold storage module, and then flowing back to the LNG heat exchanger 101 to form a cycle;

[0090] Control one of the circulation branches to flow through the first heat exchange pipeline of the cold storage hall module and be located at the first circulating refrigerant heat exchanger 204 so that the circulating refrigerant exchanges cold with the first secondary refrigerant;

[0091] The other several circulation branches are controlled to flow through the circulating refrigerant heat exchanger of at least one temperature-level cold storage module respectively, so that the circulating refrigerant exchanges cold with the cold storage refrigerant of each temperature level respectively, and the circulating refrigerant after the LNG cold energy is utilized is mixed and enters the second circulating refrigerant heat exchanger 206 of the second heat exchange pipeline, and the second refrigerant further recovers the residual cold of the circulating refrigerant, and the circulating refrigerant passing through the second circulating refrigerant heat exchanger 206 is mixed with the circulating refrigerant passing through the first circulating refrigerant heat exchanger 204 and flows back to the LNG heat exchanger to obtain new LNG cold energy;

[0092] When the LNG cold energy supply of the circulating refrigerant is insufficient, the first refrigerant circulating pump 505 is started to circulate the first temperature-level refrigerant of the first refrigerant circulating barrel 504 to the first refrigerant heat exchanger 210 and the second refrigerant heat exchanger 305, respectively, to exchange cold with the fourth refrigerant and the first cold storage refrigerant to supplement cold energy;

[0093] Start the refrigeration refrigerant circulation pumps of other temperature-level refrigeration groups, and circulate the refrigeration refrigerant in the refrigeration refrigerant circulation barrels (such as the second refrigeration refrigerant circulation barrel 509) of each temperature-level refrigeration group to the refrigeration refrigerant heat exchangers (such as the third refrigeration refrigerant heat exchanger 405) of at least one temperature-level cold storage module, and exchange cold with the cold storage refrigerant of each temperature-level cold storage module to supplement cold energy.

[0094] In the above steps, although the control of each module is described in the above order, those skilled in the art can understand that some control steps of some modules can be independently operated and the modules can be operated in combination with each other through some control steps, and it is not necessary to operate all steps to achieve the corresponding technical effects. At the same time, in order to achieve the effect of this embodiment, different steps do not have to be executed in such an order, and they can be executed simultaneously (in parallel) or in a reverse order. These simple changes are within the protection scope of the present invention.

[0095] In an optional embodiment, the control method further includes the following steps:

[0096] When the LNG cold energy is insufficient to supply the cold storage hall module and at least one temperature-grade cold storage module at the same time, the priority of the cold energy supply of the LNG cold energy of the circulating refrigerant to each module is: low-temperature cold storage module>high-temperature cold storage module>cold storage hall module. This embodiment is illustrated by two temperature-grade cold storage modules, which can also have more temperature-grade cold storage modules in actual scenarios. In this embodiment, the priority of cold supply is that the cold storage module takes precedence over the cold storage hall module, and among the cold storage modules, the cold storage module of the lower temperature grade takes precedence over the cold storage module of the higher temperature grade.

[0097] In an optional embodiment, the control method further includes the following steps:

[0098] In the cold storage hall module, the second heat exchange pipeline is started first, and the second refrigerant is used to recover the residual cold of the circulating refrigerant after the cold storage module is cooled, so as to supplement the cold energy for the low-temperature refrigerant area 202;

[0099] When the second heat exchange pipeline does not recover enough residual cold, the first heat exchange pipeline is started first, and the first refrigerant is used to absorb the LNG cold energy of the circulating refrigerant to supplement the cold energy for the low-temperature refrigerant area;

[0100] When the first heat exchange pipeline absorbs insufficient cold energy from LNG, the fourth heat exchange pipeline is opened to use the fourth refrigerant to exchange cold with the first temperature-level refrigeration refrigerant to supplement cold energy for the low-temperature-level refrigerant area 202;

[0101] In at least one temperature-level cold storage module, the pipelines for exchanging cold between the cold storage refrigerant and the circulating refrigerant of the circulation branch are preferentially started, and the LNG cold energy of the circulating refrigerant is used to supplement it; when the LNG cold energy is insufficient, the pipelines for exchanging cold with at least one group of temperature-level refrigeration groups are opened, and the cold energy of the refrigeration refrigerants of each temperature level is absorbed by the refrigerants of each temperature level cold storage to supplement it.

[0102] In an optional embodiment, in at least one temperature-level cold storage module, a circulating refrigerant heat exchanger circulating barrel is provided above the circulating refrigerant heat exchanger, and a circulating refrigerant pressure regulating valve is provided at the outlet of the circulating refrigerant heat exchanger circulating barrel. This embodiment is illustrated by taking the first temperature-level cold storage module and the second temperature-level cold storage module as an example. Figure 2 As shown, through the action of the third circulating refrigerant heat exchanger circulating barrel 3041 and the fourth circulating refrigerant heat exchanger circulating barrel 4041, the shell sides of the third circulating refrigerant heat exchanger 304 of the first temperature stage cold storage module and the fourth circulating refrigerant heat exchanger 404 of the second temperature stage cold storage module are both in a full liquid state, and the circulating refrigerant is in a saturated state after vaporization, which is respectively restricted by the second circulating refrigerant pressure regulating valve 602 and the third circulating refrigerant pressure regulating valve 603, and the outlet gas circulating refrigerant temperature is at the saturated temperature under the set pressure.

[0103] This embodiment realizes precise control of LNG cold energy by ensuring that the circulating refrigerant is in a full liquid state in the circulating refrigerant heat exchanger of the cold storage module, and coordinating the liquid level control and outlet pressure control of the circulating barrel of the circulating refrigerant heat exchanger to realize precise control of the gasification amount and gasification temperature of the circulating refrigerant.

[0104] In order to better understand the control method of the multi-temperature cold storage system, an optional embodiment of the present invention provides a connection interlocking method for transmitters or regulating valves such as specific pressure, liquid level, temperature, flow, etc. in each pipeline. The means for adjusting the circulating pump, refrigerant pump, circulating barrel, and the pipeline in which it is located are set according to the actual use requirements of the system pipeline. This embodiment does not impose any form of restriction on the specific parameter control.

[0105] Specifically, refer to Figure 2, in the main flow line of circulating refrigerant:

[0106] The pressure transmitter 701 is interlocked with the opening of the first circulation refrigerant pressure regulating valve 601;

[0107] The first liquid level transmitter 702 is power-interlocked with the circulation pump 103;

[0108] In the cold storage hall module:

[0109] The first temperature transmitter 703 is interlocked with the opening of the first circulating refrigerant flow regulating valve 604;

[0110] The second temperature transmitter 704 is power-interlocked with the second coolant pump 205;

[0111] The third temperature transmitter 705 is power-interlocked with the third coolant pump 207;

[0112] The fourth temperature transmitter 706 is power-interlocked with the fourth coolant pump 209;

[0113] The second liquid level transmitter 707 is interlocked with the opening of the first refrigeration refrigerant flow regulating valve 605;

[0114] In at least one temperature-grade cold storage module:

[0115] The third liquid level transmitter 708 is interlocked with the opening of the second circulating refrigerant flow regulating valve 606;

[0116] The fifth temperature transmitter 709 is interlocked with the opening of the first cold storage flow regulating valve 607;

[0117] The fourth liquid level transmitter 710 is interlocked with the opening of the second refrigeration refrigerant flow regulating valve 608;

[0118] The fifth liquid level transmitter 711 is interlocked with the opening of the third circulating refrigerant flow regulating valve 609;

[0119] The sixth liquid level transmitter 712 is interlocked with the opening of the third refrigerant flow regulating valve 610 .

[0120] Through the interlocking control of the above transmitter, regulating valve and pump, the adjustment can be made according to the actual use situation, so as to realize the precise control of LNG cold energy. By keeping the circulating refrigerant in the cold storage heat exchanger in a full liquid state, and coordinating the liquid level control and outlet pressure control of the circulating refrigerant circulating barrel, the circulating refrigerant gasification amount and gasification temperature can be precisely controlled, reducing the system refrigerant circulation amount and low operating cost.

[0121] In order to better understand the multi-temperature cold storage control method, the present invention provides an optional embodiment. The parameters in the following embodiments are used to illustrate specific situations and are not intended to limit the present invention in other forms. Specifically, the circulating refrigerant is CO2, the brine is 50% ethylene glycol aqueous solution, the LNG flow rate is 180t / h, the temperature is -150 to -160°C, and the pressure is 9.2MPa. The control method includes the following steps:

[0122] refer to Figure 1 LNG at -160~-150℃ from the receiving station enters the LNG heat exchanger 101 and heats up to -20~-15℃ with the gas CO2 of flow rate 300~330t / h, temperature of -5℃ and pressure of 1.2~1.4MPa, and then passes through the NG heat exchanger 102 and heats up to the reheating condition of 0~5℃ with the cold water air conditioner of 12℃ and returns to the receiving station;

[0123] After the gaseous CO2 is cooled and liquefied into liquid CO2 at -35 to -30°C, it is divided into three circulation branches, which respectively supply cooling to the low-temperature cold storage module (second-level cold storage module), the high-temperature cold storage module (first-level cold storage module), and the cold storage hall module;

[0124] The -30~-25℃ gas CO2 from the low temperature cold storage module and the high temperature cold storage module enters the second circulating refrigerant heat exchanger 206 and exchanges heat with 0~5℃ 50% ethylene glycol aqueous solution (the second refrigerant of the second heat exchange pipeline) to raise the temperature to -5~0℃, and then mixes with the -5~0℃ gas CO2 from the cold storage hall module (after cooling through the first heat exchange pipeline) and enters the LNG heat exchanger 101;

[0125] 50% ethylene glycol aqueous solution at 0-5°C is separated from the high-temperature coolant water pool (high-temperature coolant zone 201) into routes ①, ②, and ③. Route ① passes through the first coolant pump 203 and enters the first circulating refrigerant heat exchanger 204 to exchange heat with liquid CO2 at -35-30°C and cool to -5-2°C before entering the low-temperature coolant water pool (low-temperature coolant zone 202); Route ② passes through the second coolant pump 205 and enters the second circulating refrigerant heat exchanger 206 to exchange heat with gas CO2 at -30-25°C After heat exchange and cooling to -5~-2℃, it enters the low-temperature refrigerant water pool; ③ It passes through the fourth refrigerant pump 209 and enters the first refrigeration refrigerant heat exchanger 210 to exchange heat with the high-temperature refrigerant (first temperature refrigerant) of -17~-15℃ and cool to -5~-2℃ before entering the low-temperature refrigerant water pool; The -5~-2℃ refrigerant coming out of the low-temperature refrigerant water pool passes through the third refrigerant pump 207 and enters the cold storage hall 208 to release cold energy. The refrigerant is heated to 0~5℃ and then returns to the high-temperature refrigerant water pool;

[0126] The -10~-7℃ gaseous high-temperature cold storage refrigerant comes out of the high-temperature cold storage circulation barrel (the first cold storage refrigerant circulation barrel 301) and is divided into two paths. One path enters the third circulation refrigerant heat exchanger 304 to heat exchange with the -35~-30℃ liquid CO2 to cool down and liquefy into a -12~-10℃ liquid and then returns to the high-temperature cold storage circulation barrel; the other path enters the second refrigeration refrigerant heat exchanger 305 to heat exchange with the -17~-15℃ high-temperature grade refrigerant to cool down and liquefy into a -12~-10℃ liquid and returns to the high-temperature cold storage circulation barrel; then it is transported to the high-temperature cold storage (the first temperature grade cold storage 302) through the first cold storage circulation pump 303 to release cold energy, and then returns to the high-temperature cold storage circulation barrel after gasification and heating to -10~-7℃;

[0127] The -23~-20℃ gaseous low-temperature cold storage refrigerant comes out of the low-temperature cold storage circulation barrel (the second cold storage refrigerant circulation barrel 401) and is divided into two paths. One path enters the fourth circulation refrigerant heat exchanger 404 and exchanges heat with the -35~-30℃ liquid CO2 to cool it down and liquefy it into a -28~-25℃ liquid before returning to the low-temperature cold storage circulation barrel. The other path enters the third refrigeration refrigerant heat exchanger 405 and exchanges heat with the -33~-30℃ low-temperature grade refrigerant to cool it down and liquefy it into a -28~-25℃ liquid before returning to the low-temperature cold storage circulation barrel; then it is transported to the low-temperature cold storage (the second temperature grade cold storage 402) through the second cold storage circulation pump 403 to release cold energy, and then returns to the low-temperature cold storage circulation barrel 402 after gasification and heating to -23~-20℃;

[0128] The gaseous high-temperature refrigerant of 0.35~0.38MPa, -15~-13℃ is pressurized to 1.3~1.5MPa by the high-temperature compressor and then enters the high-temperature refrigerant condenser to cool down and liquefy to 25~30℃, and then expands to -17~-15℃ gas-liquid mixture through the high-temperature refrigerant expansion valve and enters the first refrigeration refrigerant circulation barrel 504, and is divided into three paths by the first refrigeration refrigerant circulation pump 505, and respectively enters the high-temperature cold storage module (first temperature cold storage module), the cold storage hall module and the low-temperature refrigeration system (second temperature refrigeration group) to release cold energy, and then returns to the first refrigeration refrigerant circulation barrel 504 after heating and gasifying to -15~-13℃, and then enters the high-temperature compressor;

[0129] The -31~-28℃ gaseous low-temperature refrigerant is pressurized to 2.5~2.7MPa by the low-temperature compressor and then enters the low-temperature refrigerant condenser to exchange heat with the liquid high-temperature refrigerant and cool down to -12~-10℃. Then, it is throttled and expanded by the low-temperature refrigerant expansion valve to become a gas-liquid mixture of -33~-30℃ and enters the second refrigeration refrigerant circulation barrel 509. It enters the low-temperature cold storage module (second temperature level cold storage module) through the second refrigeration refrigerant circulation pump 510 to release cold energy, and is heated and vaporized to -31~-28℃, and then returns to the second refrigeration refrigerant circulation barrel 509 and enters the low-temperature compressor.

[0130] The above disclosure is only one or more preferred embodiments of the present invention, which are used to help understand the inventive concept of the technical solution, and is not intended to limit the present invention in other forms. Technical personnel in the relevant field may make other equivalent or customary replacement schemes based on the features defined by the present invention, which still fall within the scope of the present invention.

Claims

1. A multi-temperature cold storage system using LNG cold energy, characterized in that: It includes an LNG heat exchanger, a cold storage hall module and at least one temperature-grade cold storage module; The cold storage hall module includes a high-temperature refrigerant area, a low-temperature refrigerant area and a plurality of heat exchange pipelines, and the heat exchange pipelines include: The first heat exchange pipeline includes a high-temperature refrigerant zone, a first refrigerant pump, a first circulating refrigerant heat exchanger, and a low-temperature refrigerant zone in sequence according to the flow direction of the first refrigerant; The second heat exchange pipeline includes a high-temperature refrigerant zone, a second refrigerant pump, a second circulating refrigerant heat exchanger, and a low-temperature refrigerant zone in sequence according to the flow direction of the second refrigerant; The circulating refrigerant of the LNG heat exchanger is divided into several circulating branches through a circulating pump to supply cold to the cold storage hall module and at least one temperature-level cold storage module, and then flows back to the LNG heat exchanger, wherein: A circulation branch passes through the first circulating refrigerant heat exchanger to exchange cold between the circulating refrigerant and the first secondary refrigerant; The other several circulation branches corresponding to at least one temperature-level cold storage module pass through the second circulating refrigerant heat exchanger. After the circulating refrigerant exchanges cold in each temperature-level cold storage module, it is mixed and enters the second circulating refrigerant heat exchanger to exchange cold with the second coolant.

2. A multi-temperature cold storage system using LNG cold energy according to claim 1, characterized in that: The heat exchange pipeline also includes a third heat exchange pipeline, which includes a low-temperature refrigerant area, a third refrigerant pump, at least one hall and / or production workshop, and a high-temperature refrigerant area in sequence according to the flow direction of the third refrigerant.

3. The multi-temperature cold storage system using LNG cold energy according to claim 1 is characterized in that: The system also includes a refrigeration module, which includes at least one temperature-stage refrigeration group, wherein the first temperature-stage refrigeration group includes a first compressor, a first condenser, a first expansion valve, and a first refrigeration refrigerant circulation barrel which are cyclically connected in sequence, and the first refrigeration refrigerant circulation barrel is connected to the fourth heat exchange pipeline of the cold storage hall module through a first refrigeration refrigerant circulation pump; The fourth heat exchange pipeline includes a high-temperature refrigerant area, a fourth refrigerant pump, a first refrigeration refrigerant heat exchanger, and a low-temperature refrigerant area in sequence according to the flow direction of the fourth refrigerant, and the first temperature-level refrigerant of the first refrigeration refrigerant circulation barrel exchanges cold with the fourth refrigerant when flowing through the first refrigeration refrigerant heat exchanger.

4. A multi-temperature cold storage system using LNG cold energy according to claim 3, characterized in that: The first refrigeration refrigerant circulation barrel is also connected to the first temperature-level cold storage module through the first refrigeration refrigerant circulation pump. The first temperature-level cold storage module includes a third circulation refrigerant heat exchanger, a second refrigeration refrigerant heat exchanger, a first cold storage refrigerant circulation barrel, a first cold storage circulation pump, and a first temperature-level cold storage. The first cold storage refrigerant circulation barrel is connected to the first temperature-level cold storage through the first cold storage circulation pump to form a pipeline for the first cold storage refrigerant to release cold energy; The third circulating refrigerant heat exchanger and the first cold storage refrigerant circulating barrel form a pipeline for circulating refrigerant in the first cold storage, wherein the circulating refrigerant in one circulating branch flows through the third circulating refrigerant heat exchanger so that the circulating refrigerant exchanges cold with the refrigerant in the first cold storage; The second refrigeration refrigerant heat exchanger and the first cold storage refrigerant circulation barrel constitute a pipeline for the circulation of the first cold storage refrigerant. The first temperature level refrigeration refrigerant in the first refrigeration refrigerant circulation barrel flows through the second refrigeration refrigerant heat exchanger to exchange cold with the first cold storage refrigerant.

5. The multi-temperature cold storage system using LNG cold energy according to claim 3 is characterized in that: The at least one temperature-level cold storage module also includes a second temperature-level cold storage module with a lower temperature than the first temperature level, the second temperature-level cold storage module includes a fourth circulating refrigerant heat exchanger, a third refrigeration refrigerant heat exchanger, a second cold storage refrigerant circulation barrel, a second cold storage circulation pump, and a second temperature-level cold storage, and the second cold storage refrigerant circulation barrel is connected to the second temperature-level cold storage through the second cold storage circulation pump to form a pipeline for the second cold storage refrigerant to release cold energy; The fourth circulating refrigerant heat exchanger and the second cold storage refrigerant circulating barrel constitute a pipeline for circulating refrigerant in the second cold storage, wherein the circulating refrigerant of a circulating branch flows through the fourth circulating refrigerant heat exchanger to exchange cold with the circulating refrigerant in the second cold storage.

6. A multi-temperature cold storage system using LNG cold energy according to claim 5, characterized in that: The at least one temperature-stage refrigeration group further includes a second temperature-stage refrigeration group, the second temperature-stage refrigeration group includes a second compressor, a second condenser, a second expansion valve, and a second refrigeration refrigerant circulation barrel which are cyclically connected in sequence, wherein the first refrigeration refrigerant circulation barrel is connected to the second condenser via a first refrigeration refrigerant circulation pump; The third refrigeration refrigerant heat exchanger and the second cold storage refrigerant circulation barrel constitute a pipeline for the circulation of the second cold storage refrigerant. The second refrigeration refrigerant circulation barrel constitutes a pipeline for the circulation of the second temperature-level refrigeration refrigerant through the second refrigeration refrigerant circulation pump and the third refrigeration refrigerant heat exchanger to exchange cold between the second cold storage refrigerant and the second temperature-level refrigeration refrigerant.

7. The multi-temperature cold storage system using LNG cold energy according to claim 1 is characterized in that: The at least one temperature-stage cold storage module and each heat exchanger in the fourth heat exchange pipeline are respectively located above the heat exchanger, and a heat exchanger circulation barrel is provided for connecting the circulation branch and / or the refrigeration group. When each circulating refrigerant and / or refrigeration refrigerant enters the heat exchanger circulation barrel, the liquid refrigerant enters the corresponding heat exchanger below due to gravity, and returns to the heat exchanger circulation barrel above after vaporization.

8. A multi-temperature cold storage control method using LNG cold energy, characterized in that: The following steps are performed using a multi-temperature cold storage system using LNG cold energy as described in any one of claims 1 to 7: The LNG heat exchanger uses the LNG flowing through it to exchange cold with the circulating refrigerant. The LNG heats up and gasifies into NG to enter the next process. The circulating refrigerant with LNG cold energy is divided into several circulating branches after passing through the cold storage hall module and at least one temperature-grade cold storage module, and then flows back to the LNG heat exchanger to form a cycle. Control one of the circulation branches to flow through the first heat exchange pipeline of the cold storage hall module and be located at the first circulating refrigerant heat exchanger so that the circulating refrigerant exchanges cold with the first secondary refrigerant; Control the other several circulation branches to flow through the circulating refrigerant heat exchanger of at least one temperature-level cold storage module respectively, so that the circulating refrigerant exchanges cold with the cold storage refrigerant of each temperature level respectively, the circulating refrigerant after the LNG cold energy is utilized is mixed and enters the second circulating refrigerant heat exchanger of the second heat exchange pipeline, the second refrigerant further recovers the residual cold of the circulating refrigerant, and the circulating refrigerant passing through the second circulating refrigerant heat exchanger is mixed with the circulating refrigerant passing through the first circulating refrigerant heat exchanger and flows back to the LNG heat exchanger to obtain new LNG cold energy; When the LNG cold energy supply of the circulating refrigerant is insufficient, the first refrigerant circulating pump is started to circulate the first temperature-level refrigerant of the first refrigerant circulating barrel to the first refrigerant heat exchanger and the second refrigerant heat exchanger, respectively, to exchange cold with the fourth refrigerant and the first cold storage refrigerant to supplement cold energy; Start the refrigerant circulation pumps of other temperature-level refrigeration groups, and circulate the refrigerant in the refrigerant circulation barrels of each temperature-level refrigeration group to the refrigerant heat exchangers of at least one temperature-level cold storage module, and exchange cold with the cold storage refrigerant of each temperature-level cold storage module to supplement cold energy.

9. A multi-temperature cold storage control method using LNG cold energy according to claim 8, characterized in that: The control method further comprises the following steps: When the LNG cold energy is insufficient to supply the cold storage hall module and at least one temperature-grade cold storage module at the same time, the priority of the LNG cold energy of the circulating refrigerant to supply cold energy to each module is: low-temperature-grade cold storage module > high-temperature-grade cold storage module > cold storage hall module.

10. A multi-temperature cold storage control method using LNG cold energy according to claim 8, characterized in that: The control method further comprises the following steps: In the cold storage hall module, the second heat exchange pipeline is started first, and the second refrigerant is used to recover the residual cold of the circulating refrigerant after the cold storage module is cooled, so as to supplement the cold energy for the low-temperature refrigerant area; when the residual cold recovered in the second heat exchange pipeline is insufficient, the first heat exchange pipeline is started first, and the first refrigerant is used to absorb the LNG cold energy of the circulating refrigerant, so as to supplement the cold energy for the low-temperature refrigerant area; when the first heat exchange pipeline does not absorb enough LNG cold energy, the fourth heat exchange pipeline is opened, and the fourth refrigerant is used to exchange cold with the first temperature-level refrigeration refrigerant, so as to supplement the cold energy for the low-temperature refrigerant area; In at least one temperature-level cold storage module, the pipelines for exchanging cold between the cold storage refrigerant and the circulating refrigerant of the circulation branch are preferentially started, and the LNG cold energy of the circulating refrigerant is used to supplement it; when the LNG cold energy is insufficient, the pipelines for exchanging cold with at least one group of temperature-level refrigeration groups are opened, and the cold energy of the refrigeration refrigerants of each temperature level is absorbed by the refrigerants of each temperature level cold storage to supplement it.

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