Liquid nitrogen cold energy recovery and chilled water preparation system

Abstract

The utility model discloses a liquid nitrogen cold energy recovery and chilled water preparation system. The system comprises a liquid nitrogen storage tank, a three-way valve, a vaporizer and a nitrogen storage tank which are connected in sequence, the three-way valve is further connected with a cooling liquid circulation loop. The cooling liquid circulation loop comprises a heat exchanger, a water inlet in one end of the heat exchanger is connected with a liquid storage tank, and a water outlet is connected with an evaporator; a circulating water pump is connected between a water outlet and a water inlet at the other end of the heat exchanger; the evaporator is further connected with the three-way valve, the liquid storage tank and the vaporizer.

Description

Technical Field

[0001] This utility model relates to the field of liquid nitrogen vaporization utilization, and in particular to a liquid nitrogen cold energy recovery and chilled water preparation system. Background Technology

[0002] Currently, in the lithium-ion battery manufacturing industry, cryogenic liquid nitrogen tanks are used as containers to store nitrogen gas. The liquid nitrogen stored is a liquid below -190 degrees Celsius. In the lithium battery production process, vaporizers are often used to vaporize the cryogenic liquid nitrogen into nitrogen gas at industrial temperatures to supply the gas to the production section. Liquid nitrogen vaporizers are generally either air-cooled or water-bath type. Air-cooled vaporizers use natural convection with air for heat exchange and vaporization. During the vaporization process, water vapor in the air can condense on the heat exchanger, causing frost to form on the heat exchanger walls, affecting the heat exchange efficiency. This not only results in significant energy loss but also reduces the reliability and stability of the gas supply. Water-bath type vaporizers require heating the liquid nitrogen with water at around 60 degrees Celsius to vaporize it. Although this avoids vaporization and freezing, water-bath type vaporizers require energy to heat the water, resulting in higher energy consumption.

[0003] Chilled water is also crucial in lithium battery manufacturing processes, with numerous applications such as slurry preparation, coating, and dehumidification. It is typically supplied by refrigeration units. During periods of high production load, the demand for cooling water increases, which in turn increases the operating load on the refrigeration units and consequently raises energy consumption.

[0004] Therefore, how to simultaneously achieve the recovery and reuse of cold energy from liquid nitrogen vaporization in lithium battery plants and the energy-saving preparation of chilled water is a major problem that urgently needs to be solved. Utility Model Content

[0005] The purpose of this invention is to provide a liquid nitrogen cold energy recovery and chilled water preparation system. By rationally connecting the evaporator and vaporizer through a three-way valve, the system can simultaneously achieve the recovery and reuse of liquid nitrogen vaporization cold energy in lithium battery plants and the energy-saving preparation of chilled water.

[0006] To achieve the above objectives, this utility model provides the following technical solution:

[0007] This utility model discloses a liquid nitrogen cold energy recovery and chilled water preparation system, including a liquid nitrogen storage tank, a three-way valve, a vaporizer, and a nitrogen storage tank connected in sequence; the three-way valve is also connected to a coolant circulation loop; the coolant circulation loop includes a heat exchanger, with the inlet of one end of the heat exchanger connected to a storage tank and the outlet connected to an evaporator; a circulating water pump is connected between the outlet and the inlet of the other end of the heat exchanger; the evaporator is also connected to the three-way valve, the storage tank, and the vaporizer respectively.

[0008] A further embodiment: the shell-side inlet of the evaporator is connected to a three-way valve, and the shell-side outlet is connected to a vaporizer; the tube-side inlet of the evaporator is connected to a heat exchanger, and the tube-side outlet is connected to a liquid storage tank.

[0009] A further solution: A regulating valve is provided between the liquid nitrogen storage tank and the three-way valve.

[0010] A further embodiment: A first temperature sensor and a first safety valve are provided between the vaporizer and the nitrogen storage tank.

[0011] A further solution: A circulating coolant pump is provided between the storage tank and the heat exchanger.

[0012] A further solution: A second temperature sensor is provided between the evaporator and the heat exchanger.

[0013] A further solution: a buffer pool is provided between the circulating water pump and the heat exchanger.

[0014] A further solution: A third temperature sensor and a filter are provided between the heat exchanger and the buffer tank.

[0015] A further solution: A second safety valve and a fourth temperature sensor are provided between the evaporator and the vaporizer.

[0016] A further embodiment: the evaporator is a shell-and-tube evaporator; the vaporizer is an ambient temperature vaporizer; and the heat exchanger is a liquid-liquid plate heat exchanger.

[0017] Compared with the prior art, the beneficial effects of this utility model are:

[0018] This invention uses a three-way valve to connect the evaporator and vaporizer in a reasonable manner, allowing them to regulate each other's temperature. It can also recover all the cooling capacity of liquid nitrogen to prepare process chilled water, making full use of the cooling capacity of liquid nitrogen in the nitrogen supply system. At the same time, it greatly reduces the energy consumption of the refrigeration unit, which not only improves energy efficiency but also significantly reduces the operating costs of the factory, creating significant economic benefits for lithium battery manufacturers. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of this utility model.

[0020] In the diagram: 1-Nitrogen storage tank, 2-Regulating valve, 3-Three-way valve, 4-Evaporator, 5-Vaporizer, 6-Liquid storage tank, 7-Nitrogen storage tank, 8-Circulating coolant pump, 9-Circulating water pump, 10-Heat exchanger, 11-Buffer tank, 12-Second safety valve, 13-First safety valve, 14-Fourth temperature sensor, 15-First temperature sensor, 16-Second temperature sensor, 17-Third temperature sensor, 18-Filter. Detailed Implementation

[0021] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0022] In the description of this utility model, it should be noted that the terms "upper", "lower", "left", "right", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the utility model product is usually placed in during use. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0023] Please see Figure 1 This embodiment of a liquid nitrogen cold energy recovery and chilled water preparation system includes a liquid nitrogen storage tank 1, a three-way valve 3, a vaporizer 5, and a nitrogen storage tank 7 connected in sequence. The three-way valve 3 is also connected to a coolant circulation loop. The coolant circulation loop includes a heat exchanger 10, with an inlet connected to a storage tank 6 and an outlet connected to an evaporator 4. A circulating water pump 9 is connected between the outlet and inlet at the other end of the heat exchanger 10. The evaporator 4 is also connected to the three-way valve 3, the storage tank 6, and the vaporizer 5. The nitrogen storage tank 1 contains liquid nitrogen with a freezing point of -196°C. The storage tank 6 is filled with a low-freezing-point working fluid with a freezing point of -30 to -48°C as the circulating coolant, which is a 45% to 57% ethylene glycol aqueous solution.

[0024] After liquid nitrogen enters the three-way valve 3, a portion flows into the vaporizer 5, where it vaporizes into nitrogen gas and enters the nitrogen storage tank 7. The remaining liquid nitrogen enters the coolant circulation loop through the other outlet of the three-way valve 3, where it exchanges heat with the coolant in the loop. The coolant storage tank 6 contains coolant, which absorbs the cooling energy from the liquid nitrogen to produce low-temperature chilled water. Simultaneously, the liquid nitrogen vaporizes due to the increased temperature and flows into the vaporizer 5 through the evaporator 4. In this way, the operating load and energy consumption of the refrigeration unit are reduced, the cooling energy from the liquid nitrogen vaporization is recovered and utilized, and the energy efficiency of the entire system is improved.

[0025] Furthermore, the shell-side inlet of evaporator 4 is connected to a three-way valve 3, and the shell-side outlet is connected to a vaporizer 5; the tube-side inlet of evaporator 4 is connected to a heat exchanger 10, and the tube-side outlet is connected to a liquid storage tank 6. Liquid nitrogen is delivered to the shell side of evaporator 4 by gravity flow, vaporizing into cryogenic nitrogen gas at a temperature not lower than -30°C. This cryogenic nitrogen gas is then heated to a temperature not lower than 20°C by vaporizer 5 and charged into nitrogen storage tank 7. Liquid nitrogen flows in the shell side of the evaporator, while coolant flows in the tube side, thus facilitating heat exchange.

[0026] Furthermore, a regulating valve 2 is provided between the liquid nitrogen storage tank 1 and the three-way valve 3. This regulating valve 2 maintains the system temperature balance by regulating the liquid nitrogen flow rate, ensuring that the liquid nitrogen is stably vaporized in the evaporator 4 and recovers cold energy; at the same time, the regulating valve 2 works in conjunction with the three-way valve 3 to distribute the flow rate of liquid nitrogen into different vaporization stages.

[0027] Furthermore, a circulating coolant pump 8 is provided between the liquid storage tank 6 and the heat exchanger 10. The function of the circulating coolant pump 8 is to transport the low-temperature circulating coolant in the liquid storage tank 6 to the tube side of the evaporator 4, where it exchanges heat with the liquid nitrogen in the shell side and recovers the cooling capacity of the liquid nitrogen.

[0028] Furthermore, a first temperature sensor 15 and a first safety valve 13 are provided between the vaporizer 5 and the nitrogen storage tank 7. The first temperature sensor 15 is used to monitor the temperature of nitrogen at the outlet of the ambient temperature vaporizer 5 in real time, and the first safety valve 13 plays an overpressure protection and timely pressure relief role in accident prevention.

[0029] Furthermore, a second temperature sensor 16 is provided between the evaporator 4 and the heat exchanger 10 to monitor the temperature of the circulating coolant in the tube side of the evaporator 4 in real time.

[0030] Furthermore, a buffer tank 11 is provided between the circulating water pump 9 and the heat exchanger 10. This buffer tank 11 is used to store the prepared low-temperature chilled water, playing a role in stabilizing the water supply. It can balance the fluctuations in the supply and demand of chilled water, ensure the stability of water supply pressure and flow when water consumption changes, and at the same time provide a certain amount of cooling capacity reserve for the system, ensuring the continuity of chilled water supply and improving the reliability and economy of system operation.

[0031] Furthermore, a third temperature sensor 17 and a filter 18 are provided between the heat exchanger 10 and the buffer tank 11. The third temperature sensor 17 is used to monitor the temperature of the chilled water after it has been cooled by the heat exchanger 10; the filter 18 is used to filter impurities in the circulating chilled water, reducing the decrease in heat exchange efficiency or equipment failure caused by impurities.

[0032] Furthermore, a second safety valve 12 and a fourth temperature sensor 14 are provided between the evaporator 4 and the vaporizer 5. The fourth temperature sensor 14 is used to monitor the temperature of the cryogenic nitrogen gas in real time.

[0033] Furthermore, evaporator 4 is a shell-and-tube evaporator; vaporizer 5 is an ambient air vaporizer; and heat exchanger 10 is a liquid-liquid plate heat exchanger. The shell-and-tube evaporator, through its tube-side and shell-side structural design, achieves highly efficient heat exchange. Liquid nitrogen flows in the shell side, while circulating coolant flows in the tube side; the two exchange heat through the tube walls, and the cooling capacity of the liquid nitrogen is absorbed by the circulating coolant, achieving effective recovery of cold energy. The ambient air vaporizer utilizes natural air convection to heat the low-temperature nitrogen gas, requiring no additional energy input and reducing operating costs. The plate heat exchanger has a compact structure, occupies little space, is suitable for installation in limited spaces, and is easy to integrate with other structures.

[0034] The working principle of this utility model is as follows:

[0035] When the temperature of liquid nitrogen after vaporization in evaporator 4 is below -30℃, the flow rate of liquid nitrogen is reduced through regulating valve 2, and the temperature of heat exchanger 10 is increased by circulating water pump 9. The flow rate of circulating coolant pump 8 is increased to ensure that the return temperature of coolant in heat exchanger 10 is not lower than -15℃. When the outlet temperature of nitrogen gas through vaporizer 5 is below 20℃, the temperature of evaporator 4 is increased by circulating coolant pump 8. The flow rate of circulating coolant pump 8 is increased to ensure that the outlet temperature of nitrogen gas in vaporizer 5 is maintained above 20℃. The other end of heat exchanger 10, circulating water pump 9, and buffer tank 11 are connected in sequence to form a loop. When the return temperature of chilled water in heat exchanger 10 is below 4℃, the flow rate of circulating water pump 9 is increased to maintain the return temperature of chilled water in heat exchanger 10 above 4℃.

[0036] The tube side of the shell-and-tube evaporator 4 is filled with circulating coolant. The heat exchange between the circulating coolant in the tube side and the liquid nitrogen in the shell side of the shell-and-tube evaporator 4 is used to recover the cooling capacity of the liquid nitrogen. The circulating coolant is then pumped by the circulating coolant pump 8 to the heat exchanger 10 to exchange heat with the circulating chilled water to prepare low-temperature chilled water.

[0037] The shell side of evaporator 4 carries liquid nitrogen supplied by liquid nitrogen storage tank 1. Buffer tank 11 stores the prepared cryogenic chilled water, which is then delivered to the chilled water pipeline network.

[0038] In practical applications, liquid nitrogen in nitrogen storage tank 1 is delivered to the shell side of the shell-and-tube evaporator 4 by gravity flow. Nitrogen storage tank 1 contains liquid nitrogen with a freezing point of -196°C. Storage tank 6 is filled with a low-freezing-point working fluid (-30 to -48°C) as a circulating coolant, consisting of a 45% to 57% ethylene glycol aqueous solution. The circulating coolant flows through the tube side of the shell-and-tube evaporator 4, utilizing heat exchange between the circulating coolant in the tube side and the liquid nitrogen in the shell side to recover the cooling capacity of the liquid nitrogen. The circulating coolant is then pumped by circulating coolant pump 8 to heat exchanger 10 to exchange heat with circulating chilled water to produce low-temperature chilled water. The liquid nitrogen vaporizes in the shell-and-tube evaporator 4 into low-temperature nitrogen gas with a temperature not lower than -30°C. The low-temperature nitrogen gas is heated to a temperature not lower than 20°C by vaporizer 5, then filled into nitrogen storage tank 7, and finally delivered to the gas-consuming end. The return water temperature of the chilled water in heat exchanger 10 is maintained above 4°C. The chilled water is stored in buffer tank 11 and finally connected to the chilled water network for use.

[0039] Based on the feedback PID control of the low-temperature nitrogen gas after liquid nitrogen vaporization, the opening and flow rates of regulating valve 2, three-way valve 3, circulating coolant pump 8, and circulating water pump 9 are adjusted to control the flow rates of liquid nitrogen, circulating coolant, and chilled water, thereby stabilizing the nitrogen temperature entering vaporizer 5. When the low-temperature nitrogen temperature entering vaporizer 5 after liquid nitrogen vaporizes by exchanging heat with circulating coolant in the shell-and-tube evaporator 4 is below -30℃, it is directly controlled by four PLC control programs. The control logic is as follows: 1. After the regulating valve 2 is loaded with PID control program, its opening gradually decreases, reducing the flow rate of liquid nitrogen entering the shell-and-tube evaporator 4. 2. The three-way valve 3 is adjusted with PID control program to control the flow rate of liquid nitrogen entering the shell-and-tube evaporator 4 and vaporizer 5. 3. After the flow rate of circulating coolant pump 8 is loaded with PID control program, the return flow rate is increased to ensure that the return coolant temperature of heat exchanger 10 is not lower than -15℃, thereby achieving temperature rise in the shell-and-tube evaporator 4 and ensuring stable vaporization of liquid nitrogen. 4. After the circulating water pump 9 is loaded with a PID control program, the return water flow rate is increased, ensuring that the return water temperature of the heat exchanger 10 is not lower than 4℃. This achieves circulating cooling heat exchange and temperature rise while maintaining the fluidity of the chilled circulating water. It also ensures that the low-temperature nitrogen temperature entering the vaporizer 5 is above -30℃.

[0040] When the nitrogen gas outlet temperature of the vaporizer 5 is below 20°C, the shell-and-tube evaporator 4 issues a control command through the PID control program to increase the circulating coolant flow rate of the circulating coolant pump 8 so that the nitrogen gas temperature is kept above 20°C, which meets the requirements of lithium battery production process.

[0041] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0042] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A liquid nitrogen cold energy recovery and chilled water preparation system, characterized in that, The system includes a liquid nitrogen storage tank (1), a three-way valve (3), a vaporizer (5), and a nitrogen storage tank (7) connected in sequence. The three-way valve (3) is also connected to a coolant circulation loop. The coolant circulation loop includes a heat exchanger (10), with a liquid storage tank (6) connected to the inlet of one end of the heat exchanger (10) and an evaporator (4) connected to the outlet. A circulating water pump (9) is connected between the outlet and the inlet of the heat exchanger (10). The evaporator (4) is also connected to the three-way valve (3), the liquid storage tank (6), and the vaporizer (5) respectively.

2. The liquid nitrogen cold energy recovery and chilled water preparation system according to claim 1, characterized in that, The shell-side inlet of the evaporator (4) is connected to the three-way valve (3), and the shell-side outlet is connected to the vaporizer (5); the tube-side inlet of the evaporator (4) is connected to the heat exchanger (10), and the tube-side outlet is connected to the liquid storage tank (6).

3. The liquid nitrogen cold energy recovery and chilled water preparation system according to claim 1, characterized in that, A regulating valve (2) is provided between the liquid nitrogen storage tank (1) and the three-way valve (3).

4. The liquid nitrogen cold energy recovery and chilled water preparation system according to claim 1, characterized in that, A first temperature sensor (15) and a first safety valve (13) are provided between the vaporizer (5) and the nitrogen storage tank (7).

5. The liquid nitrogen cold energy recovery and chilled water preparation system according to claim 1, characterized in that, A circulating coolant pump (8) is provided between the storage tank (6) and the heat exchanger (10).

6. The liquid nitrogen cold energy recovery and chilled water preparation system according to claim 1, characterized in that, A second temperature sensor (16) is provided between the evaporator (4) and the heat exchanger (10).

7. The liquid nitrogen cold energy recovery and chilled water preparation system according to claim 1, characterized in that, A buffer pool (11) is provided between the circulating water pump (9) and the heat exchanger (10).

8. The liquid nitrogen cold energy recovery and chilled water preparation system according to claim 7, characterized in that, A third temperature sensor (17) and a filter (18) are provided between the heat exchanger (10) and the buffer tank (11).

9. The liquid nitrogen cold energy recovery and chilled water preparation system according to claim 1, characterized in that, A second safety valve (12) and a fourth temperature sensor (14) are provided between the evaporator (4) and the vaporizer (5).

10. The liquid nitrogen cold energy recovery and chilled water preparation system according to claim 1, characterized in that, The evaporator (4) is a shell-and-tube evaporator; the vaporizer (5) is an ambient temperature vaporizer; and the heat exchanger (10) is a liquid-liquid plate heat exchanger.

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