Hydrate method cold storage and cooling system based on LNG cold energy

Abstract

A kind of hydrate method cold accumulation and cooling system based on LNG cold energy, including gas supply system, hydrate method cold accumulation system, cooling system and refrigerating unit auxiliary system.The huge cold energy released in LNG gasification is used in gas supply system by deionized water and resident building return water coolant water in turn.The absorbed LNG cold energy is accumulated in hydrate method cold accumulation system, and the cold accumulation system can separate hydrate and deionized water, and can realize variable rate cold accumulation.The coolant water in cooling system exchanges heat with LNG and hydrate slurry in turn, and is sent to cold storage and resident building user by circulating pump pressurization, when the cooled coolant water cannot meet the requirement of cold energy demand end or cooling system cannot stably cool, refrigerating unit auxiliary system is opened, the opening of distribution valve is adjusted according to the temperature of cold energy demand end, the coolant water through distribution valve and the coolant water without distribution valve are mixed in mixer, to meet the cold energy demand of demand end.The system has the advantages of energy saving, sustainable and stable cooling, and has the value of commercial application.

Description

Technical Field

[0001] This invention belongs to the field of hydrate application research and relates to a hydrate-based cold storage and cooling system based on LNG cold energy. Background Technology

[0002] Modern summer cooling primarily relies on refrigeration cycles, with the compressor being the main energy-consuming component. It releases heat to the environment through the outdoor unit's radiator, but its advantage lies in its sustainable cooling capacity. Therefore, reducing compressor energy consumption and minimizing heat loss to the environment is crucial.

[0003] However, the thermodynamic state of LNG transportation is -162°C at atmospheric pressure, and it is generally transported through natural gas pipelines. This process involves a significant amount of cold energy. Carbon dioxide hydrate is formed from water and CO2 under low temperature and high pressure; both carbon dioxide and water are environmentally friendly substances. By changing the temperature and pressure at which the hydrate exists, or by changing both simultaneously, the hydrate can be decomposed, releasing a large amount of cold energy. CO2 hydrate has a high cold energy storage density; the cold energy storage density of pure CO2 hydrate is 500 KJ / Kg, greater than that of ice (333 KJ / Kg). Therefore, this invention is based on the cold energy of LNG, coupling the application of hydrate with traditional refrigeration systems to reduce the energy consumption of traditional cooling systems and reduce carbon dioxide emissions, thereby improving energy utilization efficiency.

[0004] This invention aims to provide a hydrate-based cold storage and cooling system based on LNG cold energy, with the goal of reducing the energy consumption of traditional cooling systems, reducing the waste heat emission from condensers into the air, reducing the operating costs of traditional refrigeration systems by utilizing LNG cold energy, and reducing CO2 emissions into the atmosphere, ultimately achieving the goal of energy conservation and emission reduction. Summary of the Invention

[0005] This invention aims to provide a hydrate-based cold storage and cooling system based on LNG cold energy, with the goal of reducing the energy consumption of traditional cooling systems, reducing the waste heat emitted from the condenser into the air, and reducing CO2 emissions into the atmosphere, ultimately achieving the goal of energy conservation and emission reduction.

[0006] The technical solution of the present invention:

[0007] A hydrate-based cold energy storage and cooling system for LNG includes an LNG cooling system, a hydrate-based cold energy storage system, a refrigerant cooling system, a refrigeration unit auxiliary system, and a control system.

[0008] The LNG cooling system includes an LNG storage tank 1, a rotary valve 2, an LNG high-pressure pump 3, a primary vaporization chamber 4-1, and a secondary vaporization chamber 4-2. The LNG storage tank 1, LNG high-pressure pump 3, primary vaporization chamber 4-1, and secondary vaporization chamber 4-2 are connected sequentially. A rotary valve 2 is installed on the pipeline between the LNG storage tank 1 and the LNG high-pressure pump 3. The rotary valve 2 controls the amount of LNG entering the LNG high-pressure pump 3 from the LNG storage tank 1. The pressurized LNG is vaporized sequentially in the primary vaporization chamber 4-1 and the secondary vaporization chamber 4-2. The cold energy in the primary vaporization chamber 4-1 is transferred to deionized water, which absorbs the cold energy and enters the reactor 7. The deionized water is circulated by a hydrate pressurization pump 16. The LNG that has released cold energy in the primary vaporization chamber 4-1 enters the secondary vaporization chamber 4-2. The cold energy in the secondary vaporization chamber 4-2 is transferred to the circulating chilled water flowing out of the residential building. The cooled circulating chilled water enters the heat exchanger 23. The LNG exiting the secondary vaporization chamber 4-2 directly enters the pipeline network.

[0009] The hydrate-based cold storage system includes a hydrate formation promoter 5, a solution pump 6, a reaction vessel 7, a CO2 storage tank 8, an exhaust valve 9, a motor 10, a gearbox 11, a stirrer 12, a hydrate sieve 13, a deionized water control valve 14, a hydrate control valve 15, a hydrate pressurizing pump 16, a first control valve 17, a second control valve 18, a gas-liquid separator 19, a dryer 20, a CO2 gas compressor 21, and a deionized water main control valve 22. The CO2 storage tank 8 is connected to the reaction vessel 7 via the exhaust valve 9, and the opening of the exhaust valve 9 controls the amount of carbon dioxide entering the reaction vessel 7. The hydrate formation promoter 5 is pressurized and injected into the reactor 7 by the solution pump 6; the motor 10 transmits power to the stirrer 12 via the gearbox 11. The stirrer 12 is located inside the reactor 7. Under the action of the stirrer 12 and the hydrate formation promoter 5, the hydrates are more evenly distributed. A hydrate sieve 13 is installed inside the reactor 7 to separate the hydrates and low-temperature deionized water in the reactor 7. The bottom of the reactor 7 has outlets for deionized water and hydrates. Deionized water control valve 14 and hydrate control valve 15 are respectively installed on the outlet pipes of deionized water and hydrates. Valve 14 and hydrate control valve 15 control the outflow of deionized water and hydrate from reactor 7, respectively. Both the deionized water and hydrate outlet pipes are connected to hydrate pressurization pump 16. After passing through hydrate pressurization pump 16, the flow branches into two lines. One line connects to the hydrate inlet of heat exchanger 23 via first control valve 17. Hydrate pressurization pump 16 pressurizes the hydrate slurry and controls its entry into heat exchanger 23 via first control valve 17, releasing cooling energy to the circulating chilled water. The other line connects sequentially to second control valve 18 and gas-liquid separator 19. Second control valve 18 controls the amount of deionized water entering gas-liquid separator 19. The gas-liquid separator 19 has two pipelines. One pipeline is connected in sequence to the deionized water main control valve 22 and the first-stage vaporization chamber 4-1. The other pipeline is connected in sequence to the gas dryer 20, the CO2 gas compressor 21, and the CO2 storage tank 8. The gas-liquid mixture inlet of the gas-liquid separator 19 is connected to the hydrate outlet of the heat exchanger 23. The gas-liquid separator 19 separates CO2 gas and deionized water. The deionized water enters the first-stage vaporization chamber 4-1 through the deionized water main control valve 22. The CO2 gas is dried and compressed in sequence by the dryer 20 and the CO2 gas compressor 21 before entering the CO2 storage tank 8 for storage.The refrigerant cooling system includes a secondary vaporization chamber 4-2, a heat exchanger 23, a first circulation pump 24, a liquid separator 25, a mixer 30, a fan coil unit 31, a residential building, and a second circulation pump 32. The residential building's circulating refrigerant water outlet pipe, the secondary vaporization chamber 4-2, the heat exchanger 23, and the first circulation pump 24 are connected sequentially. The residential building's circulating refrigerant water outlet of the heat exchanger 23 splits into two paths via the first circulation pump 24. One path connects sequentially to the liquid separator 25, the evaporator 26, and the mixer 30; the other path connects directly to the mixer 30. The two paths converge at the mixer 30. The mixer 30 outlet, the fan coil unit 31 in the cold storage, the second circulation pump 32, the residential building's circulating refrigerant water inlet pipe, the residential building's cooling supply end, and the residential building's circulating refrigerant water outlet pipe are connected sequentially. The refrigerant water flowing out of the residential building's refrigerant water outlet pipe enters the secondary vaporization chamber 4-2 to absorb refrigerant. Yes, the water then enters the heat exchanger 23 to absorb the cold energy released by the hydrate. After heat exchange, it enters the first circulation pump 24 for pressurization, and then enters the fan coil unit 31 in the cold storage through the mixer 30 to release the cold energy to the cold storage. After heat exchange, it is pressurized by the second circulation pump 32 and sent to the cooling end of the residential building to release the cold energy. After heat exchange, it enters the secondary vaporization chamber 4-2 through the circulating chilled water outlet pipe of the residential building to complete the circulation. When the cold energy stored by the hydrate is insufficient to meet the demand, the auxiliary system of the refrigeration unit is started. According to the temperature of the chilled water at the outlet of the first circulation pump 24 and the temperature of the cold energy demand end, the opening of the liquid separator 25 is adjusted to control the amount of chilled water entering the evaporator 26 to absorb cold energy. After heat exchange, the chilled water and the chilled water that did not enter the liquid separator 25 are mixed in the mixer 30. After mixing, it enters the cooling end of the cold storage to meet the cooling demand of the demand end.

[0010] The auxiliary system of the refrigeration unit includes an evaporator 26, a compressor 27, a condenser 28, and a throttling valve 29 connected in sequence in a ring. The low-temperature and low-pressure refrigerant after throttling releases its cold energy in the evaporator 26 to the chilled water that enters the evaporator through the liquid distribution valve 25. The low-pressure and high-temperature refrigerant vapor generated after heat exchange enters the compressor 27 for compression. The high-temperature and high-pressure refrigerant vapor generated enters the condenser 28 for condensation and heat dissipation. The low-temperature and high-pressure refrigerant generated enters the throttling valve 29 for throttling. The low-temperature and low-pressure refrigerant then enters the evaporator 26, completing the cycle.

[0011] The control system is used for the coordinated operation of the LNG-based hydrate-based cold storage and cooling system. Based on the LNG cold energy supply and demand, it controls the coordinated operation of various valves, pumps, and auxiliary systems of the refrigeration unit, as well as the adjustment of pump and compressor speeds. By controlling the opening of the LNG outlet rotary valve 2, it regulates the amount of LNG entering the primary vaporization chamber 4-1 and the secondary vaporization chamber 4-2, controls the temperature of the circulating deionized water, and the initial temperature drop of the circulating chilled water flowing out of the residential building. Based on the actual LNG cooling supply, it adjusts the opening of the deionized water control valve 14 and the hydrate control valve 15, as well as the gear position of the transmission 11, to adjust the system's cold storage capacity. Based on the hydrate cooling capacity and the actual situation of the cold energy demand, it activates the auxiliary systems of the refrigeration unit, adjusts the opening of the liquid distribution valve 25, and regulates the speed of the compressor 27.

[0012] The beneficial effects of this invention are as follows: Firstly, LNG cold energy is utilized to provide a low-temperature environment for CO2 hydrate formation, achieving cold storage via the hydrate method. Secondly, LNG cold energy is utilized to cool the return water of centralized cooling systems. This multi-stage utilization of LNG fully releases its internal cold energy. Under the combined action of the CO2 cooling system and the refrigerant circulation system, cold storage and centralized cooling residential buildings are sequentially cooled, achieving multi-stage utilization of refrigerant cold energy. The entire process reduces the CO2 content in the atmosphere, fully utilizes LNG cold energy, solves the problem of unsustainable cooling via the hydrate method, achieves the goal of energy conservation and emission reduction, and has commercial application value. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the system of the present invention.

[0014] In the diagram: 1 LNG storage tank; 2 rotary valve; 3 LNG high-pressure pump; 4-1 primary vaporization chamber; 4-2 secondary vaporization chamber; 5 hydrate formation promoter; 6 solution pump; 7 reactor; 8 CO2 storage tank; 9 gas outlet valve; 10 electric motor; 11 gearbox; 12 stirrer; 13 hydrate sieve; 14 deionized water control valve; 15 hydrate control valve; 16 hydrate pressurization pump; 17 first control valve; 18 second control valve; 19 gas-liquid separator; 20 gas dryer; 21 CO2 booster pump; 22 deionized water main control valve; 23 heat exchanger; 24 first circulation pump; 25 liquid separator valve; 26 evaporator; 27 compressor; 28 condenser; 29 throttle valve; 30 mixer; 31 fan coil unit; 32 second circulation pump. Detailed Implementation

[0015] The specific embodiments of the present invention will be described in detail below with reference to the technical solutions and accompanying drawings.

[0016] like Figure 1 The system structure shown, utilizing LNG cold energy, and the steps of the hydrate-based cold storage and cooling system are as follows:

[0017] The control system adjusts the opening of the deionized water control valve 14 according to the set deionized water temperature for hydrate formation, executes the command to start the hydrate pressurization pump 16, executes the command to open the second control valve 18 and the deionized water main control valve 22, issues the opening command of the rotary valve 2, adjusts the amount of LNG entering the LNG high-pressure pump, and then controls the amount of LNG entering the first-stage vaporization chamber 4-1 so that the deionization reaches the set temperature.

[0018] The control system executes the command to open the gas outlet valve 9 to control the amount of CO2 gas entering the reactor 7. Then, the motor 10 is started, and the power is transmitted to the stirrer 12 through the gearbox 11. According to the LNG supply, the working gear of the gearbox 11 is adjusted. At the same time, the solution pump 6 is started to inject the hydrate formation promoter 5 into the reactor 7. At this time, the gears of the rotary valve 2, deionized water control valve 14, gas outlet valve 9 and gearbox 11 are all adjusted to the maximum to achieve complete system cooling.

[0019] The control system starts the second circulation pump 32, adjusts the opening of the hydrate control valve 15, and closes the second control valve 18. Circulating chilled water flows out of the residential building and undergoes a first cooling process in the secondary vaporization chamber 4-2. After heat exchange, the LNG enters the natural gas pipeline network. After heat exchange, the chilled water enters the heat exchanger 23 to exchange heat with the hydrate slurry, and the chilled water is cooled again. The chilled water flowing out of the heat exchanger 23 is pressurized by the first circulation pump 24 and sent to the cold storage through the mixer 30. The fan coil unit 31 in the cold storage provides cooling capacity to the cold storage. The chilled water flowing out of the cold storage is pressurized again by the second circulation pump 32 and sent to the residential building for cooling. After the cooling is completed, the chilled water flows out of the residential building and enters the vaporizer 4-2 for cooling, completing the cooling cycle. The deionized water control valve 14 is closed, and the opening of the rotary valve 2, the gas outlet valve 9, and the hydrate control valve 15, as well as the gear of the transmission 11, are adjusted to the maximum to achieve the maximum cooling capacity of the system.

[0020] When the cooling capacity of the system cannot meet the cooling demand, the control system starts the auxiliary system of the refrigeration unit according to the refrigerant water temperature set at the outlet of the mixer 30 based on the cooling demand. The opening of the distributor valve 25 is adjusted to control the amount of refrigerant water entering the evaporator 26 for cooling. This portion of the cooled refrigerant water enters the mixer 30 and mixes with the refrigerant water that has not been diverted by the distributor valve 25, reaching the refrigerant water temperature set at the outlet of the mixer 30. The system can then achieve continuous and stable cooling. The control system sets the operating temperature of the evaporator 26 according to the opening of the distributor valve 25 and the refrigerant water temperature set at the outlet of the mixer 30, and adjusts the operating frequency of the compressor 27 and the opening of the throttle valve 29 to make the evaporator 26 reach the preset operating temperature.

[0021] The above description is merely a basic explanation of the present invention. Based on the above description, those skilled in the art can design similar application systems or use some parts of the system in the present invention independently or combine the functions of the entire system, all of which should fall within the protection scope of the present invention.

Claims

1. A hydrate-based cold storage and cooling system for LNG cold energy, characterized in that, The LNG-based hydrate-based cold energy storage and cooling system includes an LNG cooling system, a hydrate-based cold energy storage system, a refrigerant cooling system, a refrigeration unit auxiliary system, and a control system. The LNG cooling system includes an LNG storage tank (1), a rotary valve (2), an LNG high-pressure pump (3), a primary vaporization chamber (4-1), and a secondary vaporization chamber (4-2). The LNG storage tank (1), LNG high-pressure pump (3), primary vaporization chamber (4-1), and secondary vaporization chamber (4-2) are connected in sequence. A rotary valve (2) is installed on the pipeline between the LNG storage tank (1) and the LNG high-pressure pump (3). The rotary valve (2) controls the amount of LNG entering the LNG high-pressure pump (3) from the LNG storage tank (1). The pressurized LNG is then sequentially vaporized in the primary vaporization chamber (4-1). 4-1) Gasification occurs in the secondary gasification chamber (4-2). The cold energy in the primary gasification chamber (4-1) is transferred to the deionized water. The deionized water that absorbs the cold energy enters the reactor (7). The deionized water is circulated by the hydrate pressurization pump (16). The LNG that releases cold energy in the primary gasification chamber (4-1) enters the secondary gasification chamber (4-2). The cold energy in the secondary gasification chamber (4-2) is transferred to the circulating chilled water flowing out of the residential building. The cooled circulating chilled water enters the heat exchanger (23). The LNG coming out of the secondary gasification chamber (4-2) directly enters the pipeline network. The hydrate-based cold storage system includes a hydrate formation promoter (5), a solution pump (6), a reactor (7), a CO2 storage tank (8), an exhaust valve (9), an electric motor (10), a gearbox (11), a stirrer (12), a hydrate sieve (13), a deionized water control valve (14), a hydrate control valve (15), a hydrate pressurizing pump (16), a first control valve (17), a second control valve (18), a gas-liquid separator (19), a dryer (20), a CO2 gas compressor (21), and a deionized water main control valve (22). The CO2 storage tank (8) is connected to the reactor (7) via the exhaust valve (9). Adjusting the opening of the exhaust valve (9) controls the flow of gas into the reactor (7). The amount of carbon dioxide in the solution; the hydrate formation promoter (5) is pressurized and injected into the reactor (7) by the solution pump (6); the motor (10) transmits power to the stirrer (12) through the gearbox (11). The stirrer (12) is located inside the reactor (7). Under the action of the stirrer (12) and the hydrate formation promoter (5), the hydrates generated are more evenly distributed; a hydrate sieve (13) is set inside the reactor (7). The hydrate sieve (13) is used to separate the hydrates and low-temperature deionized water in the reactor (7); the bottom of the reactor (7) is provided with outlets for deionized water and hydrates. Deionized water control valve (14) and hydrate control valve (15) are respectively installed on the outlet pipes of deionized water and hydrates. The deionized water control valve (14) and the hydrate control valve (15) control the outflow of deionized water and hydrate from the reactor (7), respectively. The outlet pipes of deionized water and hydrate are connected to the hydrate pressurizing pump (16). After passing through the hydrate pressurizing pump (16), the flow splits into two branches. One branch is connected to the hydrate inlet of the heat exchanger (23) through the first control valve (17). The hydrate pressurizing pump (16) pressurizes the hydrate and controls its entry into the heat exchanger (23) through the first control valve (17), releasing the cold energy to the circulating chilled water. The other branch is connected in sequence to the second control valve (18) and the gas-liquid separator (19). The second control valve (18) controls the flow of water into the gas-liquid separator (19). Deionized water volume; the gas-liquid separator (19) is divided into two pipelines. One pipeline is connected in sequence to the deionized water main control valve (22) and the first-stage vaporization chamber (4-1). The other pipeline is connected in sequence to the gas dryer (20), the CO2 gas compressor (21) and the CO2 storage tank (8). The gas-liquid mixture inlet of the gas-liquid separator (19) is connected to the hydrate outlet of the heat exchanger (23). The gas-liquid separator (19) separates CO2 gas and deionized water. The deionized water enters the first-stage vaporization chamber (4-1) through the deionized water main control valve (22). The CO2 gas enters the CO2 storage tank (8) after being dried and compressed by the dryer (20) and the CO2 gas compressor (21). The refrigerant cooling system includes a secondary vaporization chamber (4-2), a heat exchanger (23), a first circulation pump (24), a liquid separator (25), a mixer (30), a fan coil unit (31), a residential building, and a second circulation pump (32). The residential building circulating refrigerant water outlet pipe, the secondary vaporization chamber (4-2), the heat exchanger (23), and the first circulation pump (24) are connected in sequence. The residential building circulating refrigerant water outlet of the heat exchanger (23) is split into two paths through the first circulation pump (24). One path is connected in sequence to the liquid separator (25), the evaporator (26), and the mixer (30), while the other path is directly connected to the mixer (30). The two paths converge at the mixer (30). The mixer (30) outlet, the fan coil unit (31) in the cold storage, the second circulation pump (32), the residential building circulating refrigerant water inlet pipe, the residential building cooling end, and the residential building circulating refrigerant water outlet pipe are connected in sequence. The refrigerant water flowing out through the residential building refrigerant water outlet pipe enters the secondary vaporization chamber. The evaporation chamber (4-2) absorbs cold energy, and then enters the heat exchanger (23) to absorb the cold energy released by the hydrate. After the heat exchange is completed, it enters the first circulation pump (24) for pressurization, and enters the fan coil unit (31) in the cold storage through the mixer (30) to release the cold energy to the cold storage. After the heat exchange is completed, it is pressurized by the second circulation pump (32) and sent to the residential building cooling end to release the cold energy. After the heat exchange is completed, it enters the secondary vaporization chamber (4-2) through the residential building circulating chilled water outlet pipe to complete the circulation. When the cold energy stored by the hydrate is insufficient to meet the demand side, the refrigeration unit auxiliary system is started. According to the temperature of the chilled water at the outlet of the first circulation pump (24) and the temperature of the cold energy demand side, the opening of the liquid separator (25) is adjusted to control the amount of chilled water entering the evaporator (26) to absorb cold energy. After the heat exchange is completed, the chilled water and the chilled water that did not enter the liquid separator (25) are mixed in the mixer (30). After the mixing is completed, it enters the cold storage cooling end to meet the cooling demand of the demand side. The auxiliary system of the refrigeration unit includes an evaporator (26), a compressor (27), a condenser (28), and a throttling valve (29) connected in sequence. The low-temperature and low-pressure refrigerant after throttling releases its cold energy in the evaporator (26) to the chilled water that enters the evaporator through the liquid separator (25). The low-pressure and high-temperature refrigerant vapor generated after heat exchange enters the compressor (27) for compression. The high-temperature and high-pressure refrigerant vapor generated enters the condenser (28) for condensation and heat dissipation. The low-temperature and high-pressure refrigerant generated enters the throttling valve (29) for throttling. The low-temperature and low-pressure refrigerant then enters the evaporator (26) to complete the cycle. The control system is used for the coordinated operation of the LNG cold energy hydrate method cold storage and cooling system. According to the LNG cold energy supply and the demand of the cold energy demand side, it controls the coordinated opening of various valves, various pumps and refrigeration unit auxiliary systems, as well as the adjustment of pump speed and compressor speed. By controlling the opening of the LNG outlet rotary valve (2), it adjusts the amount of LNG entering the primary vaporization chamber (4-1) and the secondary vaporization chamber (4-2), controls the temperature of circulating deionized water, and the initial cooling range of the circulating chilled water flowing out of the residential building. According to the actual LNG cooling supply, it adjusts the opening of the deionized water control valve (14) and the hydrate control valve (15), as well as the gear of the transmission (11), to adjust the cold storage capacity of the system. According to the hydrate cooling supply and the actual situation of the cold energy demand side, it opens the refrigeration unit auxiliary system, adjusts the opening of the liquid distribution valve (25) and the speed of the compressor (27).

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