MBE liquid nitrogen tail gas cold energy recovery device

Abstract

The utility model discloses a kind of MBE liquid nitrogen tail gas cold energy recovery device, including heat exchange mechanism, cooling medium circulation mechanism and temperature control mechanism;The heat exchange mechanism includes precooling heat exchanger and main heat exchanger;The heat exchange surface of the precooling heat exchanger is directly opposite MBE liquid nitrogen tail gas discharge pipe outlet, receives directly discharged liquid nitrogen tail gas and carries out preliminary heat exchange;Through the cooling medium in precooling heat exchanger, closed loop shunt is formed with cooling medium storage tank directly, can be according to tail gas cold quantity dynamic adjustment flow entering precooling heat exchanger, ensure that the heat exchange time of cooling medium and tail gas adapts cold energy intensity, avoid the efficiency loss caused by surplus waste or deficiency of cold energy;Tail gas only contacts with precooling heat exchanger, does not enter main heat exchanger, completely avoids the risk that trace impurity in tail gas deposits or freezes in main heat exchanger, reduces equipment jam fault;Main heat exchanger focuses on the heat exchange of cooling medium and PCW system process water, is not disturbed by tail gas temperature fluctuation.

Description

Technical Field

[0001] This utility model relates to the field of energy-saving technology for molecular beam epitaxy (MBE) equipment, and in particular to a liquid nitrogen tail gas cold energy recovery device for MBE, which is used to cool down the cooling water of the MBE process. Background Technology

[0002] Molecular beam epitaxy (MBE) equipment features ultra-high vacuum, ultra-high precision, and ultra-high uniformity thin film deposition. It is a core process equipment for the manufacture of compound semiconductor materials and devices and is widely used in the preparation of epitaxial thin films for solid-state microwave radio frequency devices, semiconductor lasers, detectors, etc.

[0003] In the field of molecular beam epitaxy (MBE) technology, molecular beam equipment requires the use of large amounts of liquid nitrogen to cool the vacuum chamber during crystal growth. Liquid nitrogen absorbs a significant amount of heat upon vaporization, releasing a large amount of cold energy. This cold energy is directly discharged into the atmosphere through the exhaust pipes of the liquid nitrogen circulation system on the equipment. Because the discharged gas is low-temperature nitrogen, there is a high risk of icing and oxygen deficiency. Currently, there is no device that can recover the energy from the liquid nitrogen exhaust and integrate the heat exchange system and facility temperature control, resulting in the underutilization of this energy and significant energy waste.

[0004] To address this, a liquid nitrogen tail gas cooling energy recovery device for MBE is proposed, which is used to cool the cooling water in the MBE process. Utility Model Content

[0005] The purpose of this invention is to provide an MBE liquid nitrogen tail gas cold energy recovery device to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the main technical solutions adopted by this utility model include:

[0007] A liquid nitrogen exhaust gas cold energy recovery device for MBE includes a heat exchange mechanism, a refrigerant circulation mechanism, and a temperature control mechanism, wherein:

[0008] The heat exchange mechanism includes a precooling heat exchanger and a main heat exchanger; the heat exchange surface of the precooling heat exchanger faces the outlet of the MBE liquid nitrogen tail gas discharge pipe and receives the directly discharged liquid nitrogen tail gas for preliminary heat exchange; the heat source inlet of the main heat exchanger is connected to the PCW system return pipe, and the heat source outlet is connected to the PCW system inlet pipe.

[0009] The refrigerant circulation mechanism includes a refrigerant storage tank, a circulation pump, an energy storage tank, and pipelines. One main inlet of the refrigerant storage tank is connected to the outlet of the precooling heat exchanger via a pipeline, and the other main inlet is connected to the energy release outlet of the energy storage tank via a pipeline. The circulation pump is connected via a pipeline between the cold source inlet of the main heat exchanger and the main outlet of the refrigerant storage tank, pumping the refrigerant into the main heat exchanger to absorb cold energy. The cold source outlet of the main heat exchanger is connected via a pipeline to a temperature control mechanism, and after being diverted by the mechanism, it is connected to the energy storage inlet of the precooling heat exchanger and the energy storage tank, respectively. The refrigerant storage tank is filled with propane, and the energy storage tank is filled with paraffin-based phase change material.

[0010] As a preferred technical solution, the temperature control mechanism includes a thermocouple array, an electric regulating valve, and a PID controller. The thermocouple array is installed on the pipeline. The inlet of the electric regulating valve is connected to the cold source outlet of the main heat exchanger through a pipeline. Its first outlet is connected to the precooling heat exchanger through a pipeline, and its second outlet is connected to the energy storage inlet of the energy storage tank through a pipeline. The PID controller controls the flow opening of the electric regulating valve based on the temperature signal.

[0011] As a preferred technical solution, the refrigerant circulation mechanism further includes a bypass pipe and an electric butterfly valve. The electric butterfly valve is installed on the bypass pipe. One end of the bypass pipe is connected to the pipeline between the electric regulating valve and the energy storage tank, and the other end is connected to the pipeline between the energy storage tank and the refrigerant storage tank.

[0012] As a preferred technical solution, a check valve is installed on the pipeline between the main outlet of the refrigerant storage tank and the circulating pump, and a one-way valve is installed on the main inlet pipe connecting the refrigerant storage tank and the energy storage tank.

[0013] As a preferred technical solution, the thermocouple array includes four T-type thermocouples, which are respectively arranged at the inlet end of the precooling heat exchanger, the main outlet of the refrigerant storage tank, the cold source outlet and the heat source outlet of the main heat exchanger.

[0014] As a preferred technical solution, the precooling heat exchanger is a corrugated finned tube heat exchanger made of austenitic stainless steel SUS316L, and the main heat exchanger is a plate-fin heat exchanger.

[0015] As a preferred technical solution, a safety valve is installed on the top of the refrigerant storage tank, and the energy storage tank has a double-layer vacuum insulation structure filled with PCM-45 phase change material.

[0016] As a preferred technical solution, the inlet pipe diameter of the precooling heat exchanger is 30±0.5mm, and the outlet pipe diameter is 50±0.5mm.

[0017] This utility model has at least the following beneficial effects:

[0018] This application utilizes a pre-cooling heat exchanger where the refrigerant is directly connected to the refrigerant storage tank via an electric regulating valve, forming a closed-loop flow. The flow rate into the pre-cooling heat exchanger can be dynamically adjusted based on the exhaust gas's cooling capacity, ensuring the heat exchange time between the refrigerant and the exhaust gas matches the cooling energy intensity. This avoids efficiency losses due to excessive or insufficient cooling energy. The exhaust gas only contacts the pre-cooling heat exchanger and does not enter the main heat exchanger, completely eliminating the risk of trace impurities in the exhaust gas depositing or freezing in the main heat exchanger, reducing equipment blockage failures. The main heat exchanger focuses on heat exchange between the refrigerant and the PCW system process water, unaffected by exhaust gas temperature fluctuations, ensuring stable cooling of the process water. Attached Figure Description

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

[0020] Figure 2 This is a partial structural diagram of the present invention. Figure 1 ;

[0021] Figure 3 This is a partial structural diagram of the present invention. Figure 2 .

[0022] In the diagram: 100, heat exchange mechanism; 110, pre-cooling heat exchanger; 120, main heat exchanger; 200, refrigerant circulation mechanism; 210, refrigerant storage tank; 220, circulation pump; 230, energy storage tank; 240, bypass pipe; 250, electric butterfly valve; 300, temperature control mechanism; 310, thermocouple array; 320, electric regulating valve; 400, check valve; 500, one-way valve. Detailed Implementation

[0023] 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.

[0024] Please see Figures 1-3This utility model provides an MBE liquid nitrogen tail gas cold energy recovery device, including a heat exchange mechanism 100, a refrigerant circulation mechanism 200, and a temperature control mechanism 300. The heat exchange mechanism 100 includes a pre-cooling heat exchanger 110 and a main heat exchanger 120. The heat exchange surface of the pre-cooling heat exchanger 110 faces the outlet of the MBE liquid nitrogen tail gas discharge pipe and receives the directly discharged liquid nitrogen tail gas for preliminary heat exchange. The heat source inlet of the main heat exchanger 120 is connected to the PCW system return pipe, and the heat source outlet is connected to the PCW system inlet pipe, directly cooling the PCW system through cold energy exchange. The refrigerant circulation mechanism 200 includes a refrigerant storage tank 210, a circulation pump 220, and an energy storage tank 230. The refrigerant storage tank 210 has one main inlet connected to the outlet of the precooling heat exchanger 110 via a pipeline, and the other main inlet connected to the energy release outlet of the energy storage tank 230 via a pipeline. The circulating pump 220 is connected between the cold source inlet of the main heat exchanger 120 and the main outlet of the refrigerant storage tank 210 via a pipeline, pumping the refrigerant into the main heat exchanger 120 to absorb cold energy. The cold source outlet of the main heat exchanger 120 is connected to the temperature control mechanism 300 via a pipeline, and after being diverted by the mechanism, it is connected to the energy storage inlet of the precooling heat exchanger 110 and the energy storage tank 230 respectively. The refrigerant storage tank 210 is filled with propane medium, and the energy storage tank 230 is filled with paraffin-based phase change material.

[0025] The temperature control mechanism 300 includes a thermocouple array 310, an electric regulating valve 320, and a PID controller. The thermocouple array 310 is installed on the pipeline. The inlet of the electric regulating valve 320 is connected to the cold source outlet of the main heat exchanger 120 through a pipeline. Its first outlet is connected to the precooling heat exchanger 110 through a pipeline, and its second outlet is connected to the energy storage inlet of the energy storage tank 230 through a pipeline. The PID controller controls the flow opening of the electric regulating valve 320 based on the temperature signal. The thermocouple array 310 in the temperature control mechanism 300 monitors the pipeline temperature in real time. The PID controller controls the flow opening of the electric regulating valve 320 according to the signal, accurately adjusts the refrigerant flow rate, and distributes cold energy to the precooling heat exchanger 110 and the energy storage tank 230 as needed, thereby improving the cold energy utilization rate and preventing the main heat exchanger 120 from freezing.

[0026] The refrigerant circulation mechanism 200 also includes a bypass pipe 240 and an electric butterfly valve 250. The electric butterfly valve 250 is installed on the bypass pipe 240. One end of the bypass pipe 240 is connected to the pipeline between the electric regulating valve 320 and the energy storage tank 230, and the other end is connected to the pipeline between the energy storage tank 230 and the refrigerant storage tank 210. The electric butterfly valve 250 has a manual emergency function. The bypass pipe 240 and the electric butterfly valve 250 of the refrigerant circulation mechanism 200 provide a redundant path. When the energy storage tank 230 fails, the electric butterfly valve 250 is opened, and the refrigerant circulates around the energy storage tank 230 through the bypass pipe 240, ensuring the normal operation of the system and improving reliability and maintainability.

[0027] A check valve 400 is installed on the pipeline between the main outlet of the refrigerant storage tank 210 and the circulating pump 220, and a one-way valve 500 is installed on the main inlet pipe connecting the refrigerant storage tank 210 and the energy storage tank 230. The check valve 400 between the main outlet of the refrigerant storage tank 210 and the circulating pump 220 prevents refrigerant backflow and protects the circulating pump 220. The one-way valve 500 on the pipeline connecting the refrigerant storage tank 210 and the energy storage tank 230 prevents refrigerant backflow and ensures the cold energy storage effect of the phase change material in the energy storage tank 230.

[0028] The thermocouple array 310 includes four T-type thermocouples, which are respectively arranged at the inlet of the precooling heat exchanger 110, the main outlet of the refrigerant storage tank 210, the cold source outlet and the heat source outlet of the main heat exchanger 120; it comprehensively monitors the temperature of key parts of the system, provides accurate data for temperature control, and ensures the stable operation of the system.

[0029] Among them, the precooling heat exchanger 110 is a corrugated finned tube heat exchanger made of austenitic stainless steel SUS316L, with a fin height of 8±0.2mm, a fin pitch of 12±0.3mm, and a fin ratio ≥18.5. The main heat exchanger 120 is a plate-fin heat exchanger, with the fin surface treated by micro-arc oxidation to form a ceramic layer micropore array with a pore size of 80-120μm and a micropore distribution density of 200-250 pores / cm². 2 The heat transfer coefficient is not less than 380 W / (m²). 2 •K); The precooling heat exchanger 110 is made of corrugated finned tubes and austenitic stainless steel SUS316L, which improves heat exchange efficiency and corrosion resistance; the plate-fin structure and microporous array of ceramic layer with micro-arc oxidation treatment of the main heat exchanger 120 further improve the heat transfer coefficient and enhance the cold energy recovery effect.

[0030] The refrigerant storage tank 210 is equipped with a safety valve on its top, with an opening pressure of 1.2 MPa. The energy storage tank 230 has a double-layer vacuum insulation structure and is filled with PCM-45 phase change material, with a phase change temperature of -50 to -45℃ and a latent heat of phase change ≥210 kJ / kg. The refrigerant storage tank has a volume of 20L and is designed to withstand a pressure of 1.5 MPa. The safety valve on the top of the refrigerant storage tank 210 opens to release pressure when the pressure exceeds 1.2 MPa, ensuring safety. The double-layer vacuum insulation structure and PCM-45 phase change material of the energy storage tank 230 ensure effective storage and release of cold energy, maintaining a stable supply of cold energy to the system.

[0031] The precooling heat exchanger 110 has an inlet pipe diameter of 30±0.5mm and an outlet pipe diameter of 50±0.5mm, forming a gradually expanding structure to reduce the airflow velocity. The gradually expanding structure of the precooling heat exchanger 110 with an inlet pipe diameter of 30±0.5mm and an outlet pipe diameter of 50±0.5mm reduces the airflow velocity, reduces pressure loss, improves system operating efficiency, and avoids insufficient heat exchange.

[0032] Among them, the PID controller is a common temperature control component in this field, and the specific model selection usually depends on the system's control accuracy, response speed and other requirements (such as the common Siemens S7-200, Omron E5CC, etc.).

[0033] The working principle of this utility model is as follows:

[0034] Directional capture of exhaust gas cold energy: The cryogenic liquid nitrogen exhaust gas discharged from the MBE equipment is directly blown onto the corrugated fin surface of the precooling heat exchanger 110, and the cold energy is transferred to the refrigerant flowing inside through the fins; the exhaust gas that has completed heat exchange is directly discharged and does not enter the subsequent main heat exchanger 120, so as to avoid impurities from interfering with the main heat exchange process.

[0035] Refrigerant diversion and circulation and cold energy transfer: The refrigerant in the refrigerant storage tank 210 is pressurized by the circulation pump 220 and enters the cold source side of the main heat exchanger 120. The cold source side is the refrigerant flow channel, where the temperature decreases after absorbing cold energy. Subsequently, the refrigerant is diverted in both directions through the electric regulating valve 320.

[0036] Most of the refrigerant enters the precooling heat exchanger 110 through the first outlet of the electric regulating valve 320. After absorbing the cold energy of the exhaust gas, the temperature is further reduced and it flows directly back to the refrigerant storage tank 210, forming an instantaneous cold energy cycle between the refrigerant storage tank 210, the main heat exchanger 120, the precooling heat exchanger 110 and the refrigerant storage tank 210.

[0037] When there is excess cold energy, some of the refrigerant enters the energy storage tank 230 through the second outlet of the electric regulating valve 320, transferring the cold energy to the internal phase change material for storage; when there is insufficient cold energy, the refrigerant in the energy storage tank 230 releases the cold energy and flows back to the refrigerant storage tank 210 to replenish the system's cold capacity.

[0038] The stable cooling process of the PCW system: The process cooling water to be cooled in the PCW system enters the heat source side of the main heat exchanger 120. The heat source side is the process water flow channel. It indirectly exchanges heat with the low-temperature refrigerant on the cold source side through the heat exchange wall. After the process water temperature is reduced, it flows back to the PCW system. Because the refrigerant temperature is kept stable by the dual regulation of the pre-cooling heat exchanger 110 and the electric regulating valve 320, the heat exchange efficiency of the main heat exchanger 120 is constant, ensuring that the cooling effect of the process water is consistent.

[0039] Intelligent control and safety assurance mechanism: Thermocouple array 310 monitors the temperature of four key points in real time.

[0040] Inlet of precooling heat exchanger 110: Monitor the initial temperature of the refrigerant entering the precooling heat exchanger 110, reflecting the cooling status of the refrigerant before it enters the tail gas heat exchange stage;

[0041] Main outlet of coolant storage tank 210: Monitoring the reference temperature of the coolant entering the main circulation from coolant storage tank 210 is the core indicator for judging the overall cold energy reserve of the system.

[0042] Main heat exchanger 120 cold source outlet: monitors the temperature of the refrigerant after it releases cold energy through the main heat exchanger 120, that is, the state of the refrigerant after it is heated, reflecting the efficiency of cold energy transfer to process water.

[0043] Main heat exchanger 120 heat source outlet: Monitoring the temperature of the process cooling water in the PCW system after cooling through the main heat exchanger 120 directly reflects the system's cooling effect on the process water and is the core basis for PID controller adjustment; the PID controller dynamically adjusts the opening of the electric regulating valve 320 based on the monitoring data.

[0044] If the temperature at the main outlet of the refrigerant storage tank 210 is too high, it indicates insufficient cooling energy. Increase the proportion of refrigerant diverted to the precooling heat exchanger 110 and prolong the contact time between the refrigerant and the exhaust gas.

[0045] If the heat source outlet temperature of the main heat exchanger 120 is too low, the process water will be too cold, reducing the flow to the pre-cooling heat exchanger 110 and increasing the flow to the energy storage tank 230, thereby reducing the input of cold energy.

[0046] Meanwhile, the check valve 400 prevents the refrigerant from flowing back from the circulation pump 220, the one-way valve 500 restricts the one-way backflow from the energy storage tank 230 to the refrigerant storage tank 210, and the safety valve ensures the safety of the storage tank pressure. In the event of a failure of the energy storage tank 230 or the precooling heat exchanger 110, the bypass pipe 240 and the electric butterfly valve 250 are opened, and the refrigerant circulates directly to ensure continuous operation of the system.

[0047] All parts not described in this utility model are the same as or can be implemented using existing technology. Although embodiments of this utility model have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this utility model, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A liquid nitrogen tail gas cold energy recovery device for MBE, characterized in that, It includes a heat exchange mechanism (100), a refrigerant circulation mechanism (200), and a temperature control mechanism (300), wherein: The heat exchange mechanism (100) includes a precooling heat exchanger (110) and a main heat exchanger (120); the heat exchange surface of the precooling heat exchanger (110) faces the outlet of the MBE liquid nitrogen tail gas discharge pipe and receives the directly discharged liquid nitrogen tail gas for preliminary heat exchange; the heat source inlet of the main heat exchanger (120) is connected to the PCW system return pipe, and the heat source outlet is connected to the PCW system inlet pipe, so as to directly cool the PCW system through cold energy exchange; The refrigerant circulation mechanism (200) includes a refrigerant storage tank (210), a circulation pump (220), an energy storage tank (230), and pipelines. One of the main liquid inlets of the refrigerant storage tank (210) is connected to the outlet of the precooling heat exchanger (110) via a pipeline, and the other main liquid inlet is connected to the energy release outlet of the energy storage tank (230) via a pipeline. The circulation pump (220) is connected to the cold source of the main heat exchanger (120) via a pipeline. Between the inlet and the main outlet of the refrigerant storage tank (210), the refrigerant is pumped into the main heat exchanger (120) to absorb cold energy. The cold source outlet of the main heat exchanger (120) is connected to the temperature control mechanism (300) through a pipeline, and after being diverted by the mechanism, it is connected to the precooling heat exchanger (110) and the energy storage inlet of the energy storage tank (230). The refrigerant storage tank (210) is filled with propane medium, and the energy storage tank (230) is filled with paraffin-based phase change material.

2. The MBE liquid nitrogen tail gas cold energy recovery device according to claim 1, characterized in that: The temperature control mechanism (300) includes a thermocouple array (310), an electric regulating valve (320), and a PID controller. The thermocouple array (310) is located on a pipeline. The inlet of the electric regulating valve (320) is connected to the cold source outlet of the main heat exchanger (120) through a pipeline. Its first outlet is connected to the precooling heat exchanger (110) through a pipeline, and its second outlet is connected to the energy storage inlet of the energy storage tank (230) through a pipeline. The PID controller controls the flow opening of the electric regulating valve (320) based on the temperature signal.

3. The MBE liquid nitrogen tail gas cold energy recovery device according to claim 2, characterized in that: The refrigerant circulation mechanism (200) also includes a bypass pipe (240) and an electric butterfly valve (250). The electric butterfly valve (250) is installed on the bypass pipe (240). One end of the bypass pipe (240) is connected to the pipeline between the electric regulating valve (320) and the energy storage tank (230), and the other end is connected to the pipeline between the energy storage tank (230) and the refrigerant storage tank (210).

4. The MBE liquid nitrogen tail gas cold energy recovery device according to claim 3, characterized in that: A check valve (400) is installed on the pipeline between the main outlet of the refrigerant storage tank (210) and the circulating pump (220), and a one-way valve (500) is installed on the main inlet pipe connecting the refrigerant storage tank (210) and the energy storage tank (230).

5. The MBE liquid nitrogen tail gas cold energy recovery device according to claim 4, characterized in that: The thermocouple array (310) includes four T-type thermocouples, which are respectively arranged at the inlet end of the precooling heat exchanger (110), the main outlet of the refrigerant tank (210), the cold source outlet and the heat source outlet of the main heat exchanger (120).

6. The MBE liquid nitrogen tail gas cold energy recovery device according to claim 5, characterized in that: The precooling heat exchanger (110) is a corrugated finned tube heat exchanger made of austenitic stainless steel SUS316L, and the main heat exchanger (120) is a plate-fin heat exchanger.

7. The MBE liquid nitrogen tail gas cold energy recovery device according to claim 6, characterized in that: The top of the refrigerant storage tank (210) is equipped with a safety valve, and the energy storage tank (230) is a double-layer vacuum insulation structure filled with PCM-45 phase change material.

8. The MBE liquid nitrogen tail gas cold energy recovery device according to claim 7, characterized in that: The inlet diameter of the precooling heat exchanger (110) is 30±0.5mm, and the outlet diameter is 50±0.5mm.

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