Ice making system utilizing cold energy of liquefied natural gas

Abstract

The utility model provides an ice-making system utilizing liquefied natural gas cold energy, which is characterized in that the ice-making system transmits the cold energy of liquefied natural gas to a secondary refrigerant through a two-stage heat exchanger, and the secondary refrigerant transmits the cold energy to an ice-making preparation room, an ice-making room and an ice storage room through pipelines so as to maintain a low-temperature environment required by ice making; in the process, the liquefied natural gas is converted into gas after absorbing heat and enters a natural gas pipe network after being further treated. According to the ice-making system, the cold energy of the liquefied natural gas is effectively utilized by utilizing the characteristic that a large amount of heat is absorbed in the gasification process of the liquefied natural gas. Meanwhile, the ice-making system is also provided with a compressor refrigeration module which is used as a supplementary emergency when the energy supply of the liquefied natural gas is insufficient. The mixed refrigeration system solves the problems that in the prior art, a mixed refrigeration system adopting multiple compressors to supply cold at multiple temperature sections has multiple pipelines, control is complex, oil return is difficult, operation is tedious and the like, reduces huge energy consumption of the compressors in traditional refrigeration, and has wide application prospects.

Description

Technical Field

[0001] The utility model relates to the technical field of ice making, in particular to an ice making system utilizing the cold energy of liquefied natural gas. Background Art

[0002] As people's living standards continue to improve, the demand for ice is also increasing. Ice is widely used in various fields, including construction, the ocean shipping industry, and seafood and vegetable preservation. Simply put, the ice-making process involves freezing water. A mold filled with water is placed in a freezing environment, typically in a quick-freezing device, where the temperature is rapidly reduced to around -10°C and maintained for a certain period of time, allowing the water to solidify into ice. Currently, industrial ice plants generally use compressor refrigeration, which lowers the temperature in the ice-making chamber and freezes the water in the mold into solid ice. This compressor refrigeration method has a complex refrigeration system (including refrigeration piping, oil systems, cooling water systems, and electronic control systems), resulting in complex on-site construction processes, long construction cycles, and low energy efficiency.

[0003] Liquefied natural gas, primarily composed of methane, is a clean fossil fuel. It not only stores natural gas for heating and cooking, but also stores a vast amount of cold energy. When heated, liquefied natural gas returns to its gaseous state. During this heat exchange process, liquefied natural gas absorbs heat and transforms into a gaseous state. This phase change, resulting from temperature changes and the release of gasification, generates cold energy. Utility Model Content

[0004] In view of the above-mentioned shortcomings of the prior art, the present invention provides an ice-making system utilizing the cold energy of liquefied natural gas, comprising a primary heat exchanger, wherein the liquefied natural gas exchanges heat with a first refrigerant in the primary heat exchanger via a natural gas liquid inlet pipe. The cooled first refrigerant flows along a first pipeline and enters the ice-making room and ice storage bin respectively through a tee. After releasing the cold energy, it converges into a first refrigerant buffer container. The outlet of the first refrigerant buffer container is connected to the inlet of a first refrigerant circulation pump unit. The outlet of the first refrigerant circulation pump unit is divided into two paths through a tee, one of which flows back to the primary heat exchanger and the other is connected to an auxiliary refrigeration heat exchanger.

[0005] The auxiliary refrigeration heat exchanger cools down the inflowing first coolant through the compressor refrigeration module, and the first coolant after being cooled down by the auxiliary refrigeration heat exchanger is connected to the first pipeline through a pipeline.

[0006] Optionally, the compressor refrigeration module includes an auxiliary refrigeration compressor unit. The compressor refrigerant in the auxiliary refrigeration heat exchanger that completes cooling of the first refrigerant is connected to the auxiliary refrigeration compressor unit through a pipeline. The outlet of the auxiliary refrigeration compressor unit is divided into two paths through a tee. One path of the high-temperature and high-pressure compressor refrigerant after compression is connected to the condenser and enters the refrigeration expansion valve after cooling, and the other path is connected to the ice melting and demolding room to release heat energy and then enter the refrigeration expansion valve. The compressor refrigerant after throttling enters the auxiliary refrigeration heat exchanger and continues to be used to cool the inflowing first refrigerant.

[0007] Optionally, the liquefied natural gas enters the secondary heat exchanger after passing through the primary heat exchanger, transfers cold energy to the second refrigerant in the secondary heat exchanger, and then enters the natural gas outlet pipe.

[0008] Optionally, the second refrigerant after cooling flows out from the secondary heat exchanger and enters the ice making water pre-cooling tank and the ice making preparation room through a tee respectively. After releasing the cold energy, it flows into the second refrigerant buffer container. The outlet of the second refrigerant buffer container is connected to the inlet of the second refrigerant circulation pump group. The outlet of the second refrigerant circulation pump group is connected to the primary heat exchanger to realize the reflux of the second refrigerant.

[0009] Optionally, the ice-making water replenishment pipe is connected to the ice-making water pre-cooling water tank for preliminary cooling of the ice-making water, and the outlet of the ice-making water pre-cooling water tank is connected to the ice-making mold water injection pipe located in the ice-making preparation room, thereby injecting ice-making water into the ice-making mold.

[0010] Optionally, the ice making preparation room cooling fan is installed in the ice making preparation room, the ice making room cooling fan is installed in the ice making room, the ice storage room cooling fan is installed in the ice storage room, and the demoulding room heat exchanger is installed in the ice melting and demoulding room.

[0011] Optionally, a heater is installed in the demoulding room heat exchanger, and the heater is used for emergency heating when the compressor refrigeration module is shut down.

[0012] Optionally, the ice making preparation room, ice making room, ice melting and demoulding room and ice storage room are all heat-insulating storage structures.

[0013] Optionally, the temperature of the first coolant flowing out of the primary heat exchanger is -30°C to -25°C; the temperature of the second coolant flowing out of the secondary heat exchanger is -7°C to -3°C.

[0014] Optionally, the air temperature in the ice storage and ice making room is -20°C to -15°C; the air temperature in the ice making preparation room is 5°C to 10°C; and the air temperature in the ice melting and demoulding room is 10°C to 20°C.

[0015] As described above, the present invention provides an ice-making system that utilizes the cold energy of liquefied natural gas. This ice-making system transfers the cold energy of liquefied natural gas to a refrigerant through a two-stage heat exchanger. The refrigerant then transfers the cold energy through pipelines to the ice-making preparation room, ice-making room, and ice storage to maintain the low-temperature environment required for ice making. During this process, the liquefied natural gas absorbs heat and converts into a gaseous state. After further processing, it enters the natural gas pipeline network. This ice-making system utilizes the large amount of heat absorbed during the liquefied natural gas vaporization process to deeply integrate the liquefied natural gas, which contains cold energy, with the ice-making process, thereby achieving effective utilization of the cold energy of liquefied natural gas. At the same time, the ice-making system is also equipped with a compressor refrigeration module to serve as a supplementary emergency response when the liquefied natural gas energy supply is insufficient. This utility model solves the problems of traditional hybrid refrigeration systems that use multiple compressors with multiple temperature ranges for cooling, such as numerous pipelines, complex control, difficult oil return, and cumbersome operation. It also reduces the huge energy consumption of compressors in traditional refrigeration and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Shown is a schematic diagram of an ice-making system in Example 1 of the present invention.

[0017] Component number description

[0018] Natural gas liquid inlet pipe-1; primary heat exchanger-2; secondary heat exchanger-3; natural gas outlet pipe-4; first refrigerant buffer container-5; first refrigerant circulation pump unit-6; auxiliary refrigeration heat exchanger-7; second refrigerant buffer container-8; second refrigerant circulation pump unit-9; ice-making water pre-cooling tank-10; ice-making preparation room air cooler-11; ice-making preparation room-12; ice-making room air cooler-13; ice-making room-14; demoulding room heat exchanger-15; heater-16; ice-melting and demoulding room-17; ice storage air cooler-18; ice storage-19; auxiliary refrigeration compressor unit-20; condenser-21; refrigeration expansion valve-22; ice-making water supply pipe-23; ice-making mold water injection pipe-24. DETAILED DESCRIPTION

[0019] The following describes the embodiments of the present invention through specific examples. Those skilled in the art will readily understand the other advantages and benefits of the present invention from the disclosure herein. The present invention may also be implemented or applied through various other specific embodiments, and the details in this specification may be modified or altered based on different perspectives and applications without departing from the spirit of the present invention.

[0020] It should be noted that the illustrations provided in this embodiment are only used to schematically illustrate the basic concept of the present invention. Therefore, the illustrations only show components related to the present invention and are not drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0021] Example 1

[0022] like Figure 1 As shown, this embodiment provides an ice-making system utilizing liquefied natural gas cold energy, comprising:

[0023] In the primary heat exchanger 2, liquefied natural gas passes through the natural gas liquid inlet pipe 1 and exchanges heat with the first brine in the primary heat exchanger 2. The cooled first brine flows along the first pipeline and enters the ice making room 14 and the ice storage 19 through a tee. After releasing cold energy, it converges into the first brine buffer container 5. The outlet of the first brine buffer container 5 is connected to the inlet of the first brine circulation pump unit 6. The outlet of the first brine circulation pump unit 6 is divided into two paths through a tee. One path returns to the primary heat exchanger 2, and the other path is connected to the auxiliary refrigeration heat exchanger 7.

[0024] The auxiliary refrigeration heat exchanger 7 cools down the inflowing first refrigerant through the compressor refrigeration module. The first refrigerant cooled by the auxiliary refrigeration heat exchanger 7 is connected to the first pipeline through a pipeline to serve as a supplementary emergency when the liquefied natural gas energy supply is insufficient.

[0025] Furthermore, the compressor refrigeration module includes an auxiliary refrigeration compressor unit 20. The compressor refrigerant in the auxiliary refrigeration heat exchanger 7 that completes cooling of the first refrigerant is connected to the auxiliary refrigeration compressor unit 20 through a pipeline. The outlet of the auxiliary refrigeration compressor unit 20 is divided into two paths through a tee. One path of the high-temperature and high-pressure compressor refrigerant after compression is connected to the condenser 21 and enters the refrigeration expansion valve 22 after cooling, and the other path is connected to the ice melting and demolding room 17 to release heat energy and then enter the refrigeration expansion valve 22. The compressor refrigerant after throttling enters the auxiliary refrigeration heat exchanger 7 and continues to be used to cool the inflowing first refrigerant.

[0026] Furthermore, the liquefied natural gas passes through the primary heat exchanger 2 and enters the secondary heat exchanger 3, where it transfers its cold energy to the secondary refrigerant before entering the natural gas outlet pipe 4. The liquefied natural gas absorbs heat and vaporizes in the primary heat exchanger 2, where its temperature rises to approximately -40°C. The gas then enters the secondary heat exchanger 3, where it continues to absorb heat. After its temperature rises to approximately -10°C, it enters the downstream natural gas heating device through the natural gas outlet pipe 4. This two-stage heat exchanger fully releases the cold energy of the liquefied natural gas, minimizing energy waste.

[0027] Furthermore, the second refrigerant after cooling flows out from the secondary heat exchanger 3 and enters the ice-making water pre-cooling tank 10 and the ice-making preparation room 12 through a tee respectively. After releasing the cold energy, it converges into the second refrigerant buffer container 8. The outlet of the second refrigerant buffer container 8 is connected to the inlet of the second refrigerant circulation pump group 9. The outlet of the second refrigerant circulation pump group 9 is connected to the secondary heat exchanger 3 to realize the reflux of the second refrigerant.

[0028] Furthermore, the ice-making water replenishment pipe 23 is connected to the ice-making water pre-cooling water tank 10 for preliminary cooling of the ice-making water. The outlet of the ice-making water pre-cooling water tank 10 is connected to the ice-making mold water injection pipe 24 located in the ice-making preparation room 12, thereby injecting ice-making water into the ice-making mold. The ice-making mold filled with ice-making water is transferred to the ice-making room 14 for low-temperature freezing into solid ice, and then transferred to the ice-melting and demolding room 17 with a higher temperature for demolding and separation. Finally, the demolded solid ice is transferred to the ice storage 19 for storage. The specific shape, quantity, and placement of the ice-making mold can be flexibly adjusted according to actual needs and are not excessively restricted here.

[0029] Furthermore, the ice preparation room air cooler 11 is installed in the ice preparation room 12, the ice preparation room air cooler 13 is installed in the ice making room 14, the ice storage room air cooler 18 is installed in the ice storage room 19, and the demolding room heat exchanger 15 is installed in the ice melting and demolding room 17. The demolding room heat exchanger 15 is equipped with a heater 16, which is used for emergency heating when the compressor refrigeration module is shut down. The use of fans or heat exchangers can accelerate gas flow and speed up the cooling or heating process. The ice preparation room 12, ice making room 14, ice melting and demolding room 17, and ice storage room 19 all have insulated storage structures, which can effectively isolate heat transfer between the interior and exterior of the storage room and reduce the heat transfer load of the storage room.

[0030] It should be noted that the number of the ice preparation room cooling fan 11, ice making room cooling fan 13, ice storage room cooling fan 18, and demolding room heat exchanger 15 can be adjusted according to the actual system requirements. The above description and the illustrations in the accompanying drawings do not limit the number. Although the condenser 21 in the accompanying drawings is shown as an air-cooled condenser, this does not limit the condenser type. The condenser 21 can also be a water-cooled condenser, an evaporative condenser, or other types.

[0031] The ice-making system using liquefied natural gas cold energy proposed in this application includes, in addition to the components described above, various common components such as valves and instruments necessary to realize the control and regulation functions of the system operation, which will not be described in detail here.

[0032] The complete operation process of the above ice making system is illustrated as follows:

[0033] Liquid natural gas enters primary heat exchanger 2 through natural gas inlet pipe 1, where it exchanges heat with the first refrigerant. The liquid natural gas absorbs heat and vaporizes in primary heat exchanger 2, raising its temperature to approximately -40°C. The freezing point of the first refrigerant should be below -35°C, and the natural gas cools it down to approximately -30°C to -25°C in primary heat exchanger 2. The gaseous natural gas flows out of the outlet of primary heat exchanger 2 and enters secondary heat exchanger 3, where it continues to absorb heat and exchanges heat with the second refrigerant, raising its temperature to approximately -10°C. The second refrigerant, whose freezing point is below -10°C, is cooled by the natural gas in secondary heat exchanger 3 to approximately -5°C. Through primary and secondary heat exchangers 2 and 3, the cold energy contained in the liquefied natural gas is transferred to the first and second refrigerants. After the gaseous natural gas flows out from the outlet of the secondary heat exchanger 3, it enters the downstream natural gas heating device through the natural gas outlet pipe 4 and enters the natural gas pipeline network after being further heated.

[0034] The first brine, which flows out of the primary heat exchanger 2 at a temperature of approximately -30°C to -25°C, enters the ice storage air cooler 18 and the ice making room air cooler 13 through pipelines. The air coolers exchange heat with the air in the ice storage 19 and the ice making room 14, respectively, releasing cold energy, maintaining the air temperature in the ice storage 19 and the ice making room 14 at approximately -20°C to -15°C. After exchanging heat in the ice storage air cooler 18 and the ice making room air cooler 13, the first brine is heated to approximately -25°C to -20°C. It then flows through a pipeline into the first brine buffer container 5, where it is pumped into the primary heat exchanger 2 by the first brine circulation pump unit 6, where it is again cooled by the low-temperature natural gas to approximately -30°C to -25°C.

[0035] The auxiliary refrigeration heat exchanger 7 is connected in parallel with the primary heat exchanger 2. When the natural gas flow rate is small and the primary heat exchanger 2 cannot cool the first refrigerant to -30°C ~ -25°C, the auxiliary refrigeration compressor unit 20, condenser 21, refrigerant expansion valve 22 and auxiliary refrigeration heat exchanger 7 are started, and the auxiliary refrigeration system is used to cool the first refrigerant to ensure that the temperature of the first refrigerant entering the ice storage air cooler 18 and the ice making room air cooler 13 is in the range of -30°C ~ -25°C.

[0036] The second brine, flowing out of the secondary heat exchanger 3 at a temperature of approximately -5°C, enters the ice making pre-cooling water tank 10 and the ice making preparation room air cooler 11 through pipes. Part of the second brine entering the ice making pre-cooling water tank 10 releases its cooling capacity there, pre-cooling the ice making water supplied via the ice making water supply pipe 23 to a temperature of 2°C to 5°C. Part of the second brine entering the ice making preparation room air cooler 11 exchanges heat with the air in the ice making preparation room 12 through the air cooler, maintaining the air temperature in the ice making preparation room 12 at approximately 5°C to 10°C. After being heated by heat exchange in the ice making pre-cooling water tank 10 and the ice making preparation room air cooler 11, the second brine enters the second brine buffer tank 8 through pipes. It is then pumped into the secondary heat exchanger 3 by the second brine circulation pump unit 9, where it is again cooled to approximately -5°C by the low-temperature natural gas.

[0037] After being pre-cooled to 2°C to 5°C in the ice-making water pre-cooling tank 10, the ice-making water flows out of the pre-cooling tank 10 and enters the ice-making mold water injection pipe 24 through a pipe. In the ice-making preparation room 12, the ice-making water is injected into the ice-making mold through the ice-making mold water injection pipe 24, with the injection amount not exceeding 90% of the ice-making mold volume. In a preferred embodiment, the ice-making mold should be made of a metal with good thermal conductivity. The ice-making mold, already filled with ice-making water, is transferred to the ice-making room 14. The low-temperature air in the ice-making room 14 exchanges heat with the ice-making mold and the water inside it under the action of the ice-making room air cooler 13. After approximately 6 to 10 hours, the water inside the ice-making mold is frozen into solid ice. The frozen ice mold is transferred to the ice melting and demolding room 17, where the air temperature is maintained at 10°C to 20°C. After the ice mold remains in the room for 1-5 minutes, the ice clinging to the mold's inner wall melts slightly. The mold is then slowly tilted and the bottom slightly raised, allowing the ice column inside to escape. The finished ice column is then immediately transferred to the ice storage 19 for storage, where it remains frozen and can be further cooled to approximately -15°C.

[0038] The process of demolding the ice molds consumes a certain amount of heat. To maintain the temperature of the ice-melting and demolding room 17 at 10°C to 20°C, the air in the room should be heated using the demolding room heat exchanger 15. When the auxiliary refrigeration compressor 20 is running, the condensation heat of the refrigerant connected to the demolding heat exchanger 15 is preferentially used to heat the air in the room. When the auxiliary refrigeration compressor 20 is stopped, the heater 16 should be used to heat the air in the room.

[0039] The functions of the first brine buffer container 5 and the second brine buffer container 8 are to increase the capacity of the brine in the system and improve the stability of the brine circulation system.

[0040] In summary, the present invention provides an ice-making system that utilizes the cooling energy of liquefied natural gas (LNG). This ice-making system transfers the cooling energy of LNG to a refrigerant via a two-stage heat exchanger. The refrigerant then transfers the cooling energy via pipelines to the ice-making preparation room, ice-making room, and ice storage to maintain the low-temperature environment required for ice-making. During this process, the LNG absorbs heat and converts into a gaseous state. After further processing, it enters the natural gas pipeline network. This ice-making system utilizes the large amount of heat absorbed during the LNG vaporization process, deeply integrating the LNG, which contains cooling energy, with the ice-making process, thereby effectively utilizing the cooling energy of LNG. Furthermore, the ice-making system is equipped with a compressor refrigeration module to serve as a supplementary emergency response when the LNG energy supply is insufficient. This utility model solves the problems of conventional hybrid refrigeration systems that use multiple compressors with multiple temperature ranges for cooling, such as numerous pipelines, complex control, difficult oil return, and cumbersome operation. It also reduces the significant energy consumption of compressors in conventional refrigeration, and has broad application prospects.

[0041] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the present invention. Anyone skilled in the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by one of ordinary skill in the art without departing from the spirit and technical principles disclosed in the present invention are intended to be covered by the claims of the present invention.

Claims

1. An ice making system utilizing liquefied natural gas cold energy, characterized in that: The system comprises a primary heat exchanger, wherein liquid natural gas exchanges heat with a first refrigerant in the primary heat exchanger via a natural gas liquid inlet pipe. The cooled first refrigerant flows along a first pipeline and enters the ice making room and ice storage bin respectively through a tee. After releasing cold energy, the first refrigerant flows into a first refrigerant buffer container. The outlet of the first refrigerant buffer container is connected to the inlet of a first refrigerant circulation pump unit. The outlet of the first refrigerant circulation pump unit is divided into two paths through a tee, one of which flows back to the primary heat exchanger and the other is connected to an auxiliary refrigeration heat exchanger. The auxiliary refrigeration heat exchanger cools down the inflowing first coolant through the compressor refrigeration module, and the first coolant after being cooled down by the auxiliary refrigeration heat exchanger is connected to the first pipeline through a pipeline.

2. The ice-making system utilizing liquefied natural gas cold energy according to claim 1, characterized in that: The compressor refrigeration module includes an auxiliary refrigeration compressor unit. The compressor refrigerant in the auxiliary refrigeration heat exchanger that completes cooling of the first refrigerant is connected to the auxiliary refrigeration compressor unit through a pipeline. The outlet of the auxiliary refrigeration compressor unit is divided into two paths through a tee. One path of the high-temperature and high-pressure compressor refrigerant after compression is connected to the condenser and enters the refrigeration expansion valve after cooling. The other path is connected to the ice melting and demolding room to release heat energy and then enter the refrigeration expansion valve. The compressor refrigerant after throttling enters the auxiliary refrigeration heat exchanger and continues to be used to cool the inflowing first refrigerant.

3. The ice-making system utilizing liquefied natural gas cold energy according to claim 2, characterized in that: The liquefied natural gas enters the secondary heat exchanger after passing through the primary heat exchanger, where it transfers cold energy to the second refrigerant before entering the natural gas outlet pipe.

4. The ice-making system utilizing liquefied natural gas cold energy according to claim 3, characterized in that: The cooled second refrigerant flows out of the secondary heat exchanger and enters the ice making water pre-cooling tank and the ice making preparation room through a tee respectively. After releasing the cold energy, it flows into the second refrigerant buffer container. The outlet of the second refrigerant buffer container is connected to the inlet of the second refrigerant circulation pump group. The outlet of the second refrigerant circulation pump group is connected to the secondary heat exchanger to realize the reflux of the second refrigerant.

5. The ice-making system utilizing liquefied natural gas cold energy according to claim 4, characterized in that: The ice making water supply pipe is connected to the ice making water pre-cooling water tank for preliminary cooling of the ice making water, and the outlet of the ice making water pre-cooling water tank is connected to the ice making mold water injection pipe located in the ice making preparation room, so as to inject the ice making water into the ice making mold.

6. The ice-making system utilizing liquefied natural gas cold energy according to claim 4, characterized in that: The ice making preparation room cooling fan is installed in the ice making preparation room, the ice making room cooling fan is installed in the ice making room, the ice storage room cooling fan is installed in the ice storage room, and the demoulding room heat exchanger is installed in the ice melting and demoulding room.

7. The ice-making system utilizing liquefied natural gas cold energy according to claim 6, characterized in that: The stripping room heat exchanger is equipped with a heater, which is used for emergency heating when the compressor refrigeration module is shut down.

8. The ice-making system utilizing liquefied natural gas cold energy according to claim 4, characterized in that: The ice making preparation room, ice making room, ice melting and demoulding room and ice storage room are all heat-insulating storage structures.

9. The ice-making system utilizing liquefied natural gas cold energy according to claim 4, characterized in that: The temperature of the first coolant flowing out of the primary heat exchanger is -30°C to -25°C; the temperature of the second coolant flowing out of the secondary heat exchanger is -7°C to -3°C.

10. The ice-making system utilizing liquefied natural gas cold energy according to claim 4, characterized in that: The air temperature in the ice storage and ice making room is -20°C to -15°C; the air temperature in the ice making preparation room is 5°C to 10°C; and the air temperature in the ice melting and demoulding room is 10°C to 20°C.

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