A system and method for comprehensive utilization of liquid nitrogen cold energy

Abstract

This invention discloses a system and method for the comprehensive utilization of liquid nitrogen cold energy, including a liquid nitrogen storage tank, a vaporizer, a fan, an insulation cover, a temperature sensor, and an intelligent control unit. The vaporizer has a liquid nitrogen channel with a liquid nitrogen inlet and a nitrogen outlet. The outlet of the liquid nitrogen storage tank is connected to the liquid nitrogen inlet of the vaporizer via a first pipe, which is equipped with a regulating valve. The nitrogen outlet is connected to the grain silo via a second pipe. The insulation cover surrounds the vaporizer. The fan delivers ambient air into the insulation cover, allowing indirect heat exchange between the air and the vaporizer. After cooling, the air is connected to the grain silo via a third pipe. The temperature sensor is installed on the second and / or third pipes. The intelligent control unit is electrically connected to the temperature sensor, the regulating valve, and the fan. Liquid nitrogen is vaporized by the vaporizer, and the air is cooled after heat exchange within the insulation cover. Operating parameters can be automatically adjusted according to grain conditions and climate, achieving energy-saving and intelligent temperature and atmosphere control in the grain silo.

Description

Technical Field

[0001] This invention relates to the field of grain storage and energy conservation technology, and in particular to a system and method based on the comprehensive utilization of liquid nitrogen cold energy. Background Technology

[0002] Currently in the grain storage industry, such as Figure 1 As shown, cooling and controlled atmosphere typically employ two independent systems: a fan system for cooling and a liquid nitrogen system for controlled atmosphere. Currently, liquid nitrogen is widely used in industry for food freezing, cryogenic grinding, and biological sample preservation. The cold energy released during its vaporization process (approximately 199 kJ / kg) is usually dissipated directly into the atmosphere through an ambient temperature vaporizer, resulting in significant energy waste. In the grain storage sector, although some research has attempted to use liquid nitrogen cold energy for localized cooling, a mature and systematic integrated utilization solution has not yet been developed, especially lacking an integrated system that recovers cold energy for grain silo cooling while simultaneously utilizing vaporized nitrogen for controlled atmosphere. This "cold and hot separation" operating mode leads to low system energy efficiency, high operating costs, slow cooling speed, and unsatisfactory grain quality control, making it difficult to meet the development needs of large-scale, intelligent, and green grain storage. Summary of the Invention

[0003] In order to solve all or some of the above problems, the present invention aims to provide a system and method based on the comprehensive utilization of liquid nitrogen cold energy.

[0004] The present invention solves its problems through the following technical solution: A system based on the comprehensive utilization of liquid nitrogen cold energy includes: a liquid nitrogen storage tank, a vaporizer, a fan, an insulation cover, a temperature sensor, and an intelligent control unit; the vaporizer is provided with a liquid nitrogen channel, which has a liquid nitrogen inlet and a nitrogen outlet; the outlet of the liquid nitrogen storage tank is connected to the liquid nitrogen inlet of the vaporizer through a first pipe, and a regulating valve is provided on the first pipe; the nitrogen outlet is connected to a grain silo through a second pipe; the insulation cover is wrapped around the outside of the vaporizer; the fan sends ambient air into the insulation cover, allowing indirect heat exchange between the air and the vaporizer; after cooling, the air is connected to the grain silo through a third pipe; the temperature sensor is installed on the second pipe and / or the third pipe; the intelligent control unit is electrically connected to the temperature sensor, the regulating valve, and the fan respectively.

[0005] Optionally, the heat exchange method of the vaporizer can be selected from either or a combination of the following two: (1) air flows through the outer wall of the vaporizer and indirectly exchanges heat with the low-temperature medium in the liquid nitrogen channel; (2) the vaporizer is provided with a heat exchange pipe, and air flows through the heat exchange pipe and indirectly exchanges heat with the low-temperature medium.

[0006] Optionally, one or more vaporizers may be provided. When multiple vaporizers are provided, they may be connected in parallel or in series.

[0007] Optionally, the grain silo is equipped with a temperature and humidity sensor and an oxygen concentration sensor, both of which are electrically connected to the intelligent control unit.

[0008] A method for the aforementioned system based on the comprehensive utilization of liquid nitrogen cold energy includes the following steps: a. Liquid nitrogen supply steps: Liquid nitrogen in the liquid nitrogen storage tank is transported to the liquid nitrogen channel of the vaporizer through the first pipeline and regulating valve, where it absorbs heat and vaporizes, releasing cold energy; b. Air pre-cooling step: The fan is started, driving ambient air into the insulation cover, where it indirectly exchanges heat with the vaporizer, and the air is pre-cooled to the set temperature range. c. Cooling and air supply steps: The pre-cooled air is sent into the grain silo through the third pipe, mixes with the air inside the silo, and lowers the internal temperature of the grain silo. d. Nitrogen gas conditioning procedure: The nitrogen gas vaporized in the vaporizer is injected into the grain silo through the second pipeline to replace the air in the silo and reduce the oxygen concentration; e. Intelligent control steps: The intelligent control unit receives parameters collected in real time from the temperature sensor, humidity sensor, and oxygen concentration sensor, and automatically adjusts the opening of the regulating valve and the fan speed according to the preset threshold to achieve on-demand cooling and gas regulation.

[0009] Optionally, in step e, when the temperature inside the grain silo is higher than the preset upper limit, the intelligent control unit increases the opening of the regulating valve and / or increases the fan speed; when the temperature inside the grain silo is lower than the preset lower limit, the regulating valve opening is reduced and / or the fan speed is decreased; when the oxygen concentration is higher than the preset upper limit, the liquid nitrogen flow rate is increased; when the oxygen concentration is lower than the preset lower limit, the liquid nitrogen flow rate is decreased.

[0010] The technical principle of this invention lies in the fact that liquid nitrogen vaporizes at -196℃ under normal pressure, releasing a large amount of cold energy during the vaporization process. This system uses an insulated shield to indirectly exchange heat between the vaporizer and the ambient air, allowing the air to absorb the cold energy from the liquid nitrogen and be pre-cooled before being sent into the grain silo for further cooling, thus achieving primary utilization of the cold energy. The vaporized nitrogen gas (still maintaining a low temperature, approximately -150℃ to -50℃) is directly injected into the grain silo, utilizing its low-temperature characteristics for further cooling and its inert properties to displace oxygen, achieving secondary utilization of the cold energy and controlled atmosphere function. Through this tiered utilization model, the cold energy of the liquid nitrogen is fully recovered, significantly improving the overall energy efficiency of the system.

[0011] In summary, the technical effects and advantages of this invention are as follows: (1) High cold energy recovery rate: The cold energy released by liquid nitrogen vaporization is about 199 kJ / kg. This system utilizes air pre-cooling and low-temperature nitrogen direct delivery in two stages, and the cold energy recovery rate can reach more than 70%, which is a qualitative improvement compared with the traditional ambient temperature vaporizer (cold energy is completely lost). (2) Improved cooling efficiency: The temperature of the pre-cooled air can reach 5-15℃, which is 30%-50% more efficient than direct cooling of ambient air, and the cooling cycle of the grain warehouse is shortened by more than 1 / 3; (3) Reduced system energy consumption: By using cold energy recovery to replace part of the mechanical refrigeration, the overall system energy consumption is reduced by 40%-60%, and the operating cost is significantly reduced; (4) Dual-function unit, simplified equipment: The cooling and controlled atmosphere functions are integrated into the same system, reducing equipment investment by about 20%-30%; (5) Intelligent control and precise cooling: Adjustment is made in real time according to the grain condition to avoid excessive cooling and nitrogen waste, and further reduce operating costs; (6) Green and environmentally friendly: It uses liquid nitrogen as a cold source and is free of harmful refrigerants such as Freon, which meets the requirements for green grain storage. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of the structure of a traditional grain warehouse with an independent dual system. Figure 2 This is a schematic diagram of a system based on the comprehensive utilization of liquid nitrogen cold energy according to an embodiment of the present invention.

[0014] The components are: 1. Liquid nitrogen storage tank; 2. Vaporizer A; 3. Vaporizer B; 4. Fan; 5. Temperature sensor; 6. Insulation cover; 7. First pipeline; 8. Regulating valve; 9. Second pipeline; 10. Third pipeline; 11. Grain silo A; 12. Grain silo B. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0016] like Figure 2As shown, this embodiment of a system based on the comprehensive utilization of liquid nitrogen cold energy mainly includes: a liquid nitrogen storage tank 1, a vaporizer, a fan 4, an insulation cover 6, a temperature sensor 5, and an intelligent control unit. The liquid nitrogen storage tank 1 is used to store liquid nitrogen, serving as both a nitrogen source and a cold energy source. The vaporizer has a liquid nitrogen channel with a liquid nitrogen inlet and a nitrogen outlet. The outlet of the liquid nitrogen storage tank 1 is connected to the liquid nitrogen inlet of the vaporizer via a first pipe 7. A regulating valve 8 is installed on the first pipe 7 to regulate the liquid nitrogen flow rate. The nitrogen outlet is connected to a grain silo via a second pipe 9. The insulation cover 6 surrounds the vaporizer, forming a closed structure. In this embodiment, the insulation cover 6 is an openable / closable type. The fan 4 delivers ambient air into the insulation cover 6, allowing indirect heat exchange between the air and the vaporizer. After cooling, the air connects to the grain silo via the third pipe 10. The temperature sensor 5 is installed on the second pipe 9 and / or the third pipe 10. The intelligent control unit is electrically connected to the temperature sensor 5, the regulating valve 8, and the fan 4. In this embodiment, the vaporizer is a closed structure with a liquid nitrogen channel. The liquid nitrogen vaporizes and releases cold energy within the channel. Air flows through the heat exchange pipes on the outer wall of the vaporizer or inside the vaporizer to exchange heat with the liquid nitrogen channel, achieving air pre-cooling. Simultaneously, the vaporized nitrogen is output as a controlled atmosphere gas. The fan 4 is a centrifugal fan.

[0017] Optionally, the heat exchange method of the vaporizer can be selected from either or a combination of the following two methods according to the actual application: (1) air flows through the outer wall of the vaporizer and indirectly exchanges heat with the low-temperature medium in the liquid nitrogen channel; (2) the vaporizer is provided with a heat exchange pipe, and air flows through the heat exchange pipe and indirectly exchanges heat with the low-temperature medium.

[0018] Optionally, the system supports modular expansion, allowing for the configuration of multiple gasification and air supply units based on the size of the grain silo. That is, one or more gasifiers can be installed in the system, connected in parallel or series when multiple gasifiers are used. In practical applications, when multiple gasifiers are installed, the following operating modes can be adopted: Parallel mode: Multiple gasifiers work simultaneously, suitable for high-flow-rate scenarios (such as cooling multiple grain silos at the same time). Series mode: Air flows through multiple vaporizers in sequence to achieve stepped cooling, which is suitable for scenarios with lower supply air temperature requirements; Rotation mode: Some vaporizers are in operation, while others are on standby or defrosting. This mode is suitable for continuous operation scenarios and ensures system reliability.

[0019] For example, such as Figure 2As shown, vaporizers A2 and B3 are connected in parallel. The regulating valve corresponding to vaporizer A2 is open, and the regulating valve corresponding to vaporizer B3 is closed. Vaporizer A2 is working, while vaporizer B3 is not. Air enters the insulation cover of vaporizer A2, is cooled, and then is delivered to grain silo A11, reducing the internal temperature of grain silo A11. Liquid nitrogen enters vaporizer A2, is vaporized, and then is delivered to grain silo B12, reducing the oxygen concentration inside grain silo B12. Furthermore, multiple vaporizers can be connected in series on the pipeline of vaporizer A2 to achieve cascaded cooling; similarly, multiple vaporizers can also be connected in series on the pipeline of vaporizer B3 to achieve cascaded cooling as well.

[0020] Optionally, the grain silo is equipped with temperature and humidity sensors and oxygen concentration sensors, both of which are electrically connected to the intelligent control unit. Temperature sensor 5 and the temperature and humidity sensors can be installed in different areas inside the grain silo (top, middle, bottom).

[0021] In this embodiment, the low-temperature air after heat exchange is sent into the grain silo through the third pipe 10, which is an air supply pipe to achieve rapid cooling; the vaporized nitrogen can be partially or completely injected into the grain silo as needed to establish a low-oxygen environment; the system uses a temperature sensor 5 to monitor the inlet and outlet air temperature and nitrogen temperature in real time, and combines the regulating valve 8 and the frequency converter control of the fan 4 to achieve precise adjustment of the air supply temperature.

[0022] This embodiment also provides a method for the aforementioned system based on the comprehensive utilization of liquid nitrogen cold energy, comprising the following steps: a. Liquid nitrogen supply steps: Liquid nitrogen in liquid nitrogen storage tank 1 is transported to the liquid nitrogen channel of vaporizer through the first pipeline 7 and regulating valve 8, where it absorbs heat and vaporizes, releasing cold energy. b. Air pre-cooling step: Fan 4 is started, driving ambient air into the insulation cover 6, where it indirectly exchanges heat with the vaporizer, and the air is pre-cooled to the set temperature range; for example, the air is pre-cooled to 5-15℃. c. Cooling and air supply steps: The pre-cooled air is sent into the grain silo through the third pipe 10, where it mixes with the air inside the grain silo to reduce the internal temperature of the grain silo. d. Nitrogen gas conditioning procedure: The nitrogen gas vaporized in the vaporizer is injected into the grain silo through the second pipe 9 to replace the air in the grain silo and reduce the oxygen concentration in the grain silo. e. Intelligent control steps: The intelligent control unit receives parameters collected in real time from the temperature sensor 5, the temperature and humidity sensor, and the oxygen concentration sensor, and automatically adjusts the opening of the regulating valve 8 and the speed of the fan 4 according to the preset threshold to achieve on-demand cooling and gas regulation.

[0023] Optionally, the system automatically adjusts the liquid nitrogen flow rate and fan speed 4 based on the internal temperature and humidity, oxygen concentration, and external climate conditions of the grain silo. In step e, when the temperature inside the grain silo is higher than the preset upper limit, the intelligent control unit increases the opening of the regulating valve 8 and / or increases the fan speed 4; when the temperature inside the grain silo is lower than the preset lower limit, the opening of the regulating valve 8 is decreased and / or the fan speed 4 is reduced; when the oxygen concentration is higher than the preset upper limit, the liquid nitrogen flow rate is increased; when the oxygen concentration is lower than the preset lower limit, the liquid nitrogen flow rate is decreased. During operation, liquid nitrogen is vaporized by the vaporizer to release cold energy, and air exchanges heat with the vaporizer inside the insulation cover 6 to form low-temperature air supply. At the same time, nitrogen can be injected into the grain silo as needed. The system can automatically adjust operating parameters according to grain conditions and climate to achieve efficient, energy-saving, and intelligent grain silo temperature and atmosphere control. Typically, when the temperature and oxygen concentration inside the grain silo reach the target values, the system stops working on that grain silo and will then move to the next grain silo, supplying low-temperature air and nitrogen to that silo.

[0024] The technical principle of this embodiment is as follows: Liquid nitrogen vaporizes at -196℃ under normal pressure, releasing a large amount of cold energy during the vaporization process. This system uses an insulated shield 6 to indirectly exchange heat between the vaporizer and the ambient air, allowing the air to absorb the cold energy from the liquid nitrogen and be pre-cooled before being sent into the grain silo for further cooling, achieving primary utilization of the cold energy. The vaporized nitrogen gas (still maintaining a low temperature, approximately -150℃ to -50℃) is directly injected into the grain silo, utilizing its low-temperature characteristics for further cooling and its inert properties to displace oxygen, achieving secondary utilization of the cold energy and controlled atmosphere function. Through this tiered utilization model, the cold energy of the liquid nitrogen is fully recovered, significantly improving the overall energy efficiency of the system.

[0025] In summary, this embodiment aims to solve the problems of liquid nitrogen cold energy waste, low cooling efficiency, high system energy consumption, high operating costs, and unsatisfactory grain quality control in existing grain warehouse temperature control and atmosphere control systems, and provides an integrated grain warehouse temperature control and atmosphere control system and method with comprehensive cold energy utilization, energy efficiency, and intelligent control. This embodiment has the following beneficial effects: (1) High cold energy recovery and utilization rate: The cold energy released by liquid nitrogen vaporization is about 199 kJ / kg, this system utilizes air pre-cooling and low-temperature nitrogen direct delivery in two stages, and the cold energy recovery rate can reach more than 70%, which is a qualitative improvement compared with the traditional air-temperature vaporizer (cold energy is completely lost); (2) Improved cooling efficiency: the pre-cooled air temperature can reach 5-15℃, which is 30%-50% more efficient than the direct cooling of ambient air, and the cooling cycle of the grain warehouse is shortened by more than 1 / 3; (3) Reduced system energy consumption: the cold energy recovery replaces part of the mechanical refrigeration, the overall energy consumption of the system is reduced by 40%-60%, and the operating cost is significantly reduced; (4) Dual-function machine, simplified equipment: the cooling and atmosphere control functions are integrated into the same system, reducing equipment investment by about 20%-30%; (5) Intelligent control, precise cooling: real-time adjustment according to grain conditions, avoiding excessive cooling and nitrogen waste, further reducing operating costs; (6) Green and environmentally friendly: liquid nitrogen is used as the cold source, without harmful refrigerants such as Freon, which meets the requirements of green grain storage.

[0026] Finally, the following points should be noted: First, in the description of this application, it should be noted that, unless otherwise specified and limited, the terms "installation", "connection", and "linkage" should be interpreted broadly, and can be mechanical or electrical connections, or internal connections between two components, or direct connections. "Up", "down", "left", "right", etc. are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may change. Secondly: The accompanying drawings of the embodiments disclosed in this invention only involve the structures involved in the embodiments disclosed in this invention. Other structures can refer to the general design. In the absence of conflict, the same embodiment and different embodiments of this invention can be combined with each other. In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A system based on the comprehensive utilization of liquid nitrogen cold energy, characterized in that, include: The system comprises a liquid nitrogen storage tank, a vaporizer, a blower, an insulation cover, a temperature sensor, and an intelligent control unit. The vaporizer has a liquid nitrogen channel with a liquid nitrogen inlet and a nitrogen outlet. The outlet of the liquid nitrogen storage tank is connected to the liquid nitrogen inlet of the vaporizer via a first pipe, which is equipped with a regulating valve. The nitrogen outlet is connected to the grain silo via a second pipe. The insulation cover surrounds the vaporizer. The blower draws ambient air into the insulation cover, allowing indirect heat exchange between the air and the vaporizer. After cooling, the air is connected to the grain silo via a third pipe. The temperature sensor is located on the second and / or third pipes. The intelligent control unit is electrically connected to the temperature sensor, the regulating valve, and the blower.

2. The system based on the comprehensive utilization of liquid nitrogen cold energy according to claim 1, characterized in that, The heat exchange method of the vaporizer is selected from either or a combination of the following two: (1) air flows through the outer wall of the vaporizer and indirectly exchanges heat with the low temperature medium in the liquid nitrogen channel; (2) the vaporizer is provided with a heat exchange pipe, and air flows through the heat exchange pipe and indirectly exchanges heat with the low temperature medium.

3. The system based on the comprehensive utilization of liquid nitrogen cold energy according to claim 1, characterized in that, One or more vaporizers are provided. When multiple vaporizers are provided, they are connected in parallel or in series.

4. The system based on the comprehensive utilization of liquid nitrogen cold energy according to claim 1, characterized in that, The grain silo is equipped with temperature and humidity sensors and oxygen concentration sensors, all of which are electrically connected to the intelligent control unit.

5. A method for use in the system based on the comprehensive utilization of liquid nitrogen cold energy as described in any one of claims 1-4, characterized in that, Includes the following steps: a. Liquid nitrogen supply steps: Liquid nitrogen in the liquid nitrogen storage tank is transported to the liquid nitrogen channel of the vaporizer through the first pipeline and regulating valve, where it absorbs heat and vaporizes, releasing cold energy; b. Air pre-cooling step: The fan is started, driving ambient air into the insulation cover, where it indirectly exchanges heat with the vaporizer, and the air is pre-cooled to the set temperature range. c. Cooling and air supply steps: The pre-cooled air is sent into the grain silo through the third pipe, mixes with the air inside the silo, and lowers the internal temperature of the grain silo. d. Nitrogen gas conditioning procedure: The nitrogen gas vaporized in the vaporizer is injected into the grain silo through the second pipeline to replace the air in the silo and reduce the oxygen concentration; e. Intelligent control steps: The intelligent control unit receives parameters collected in real time from the temperature sensor, humidity sensor, and oxygen concentration sensor, and automatically adjusts the opening of the regulating valve and the fan speed according to the preset threshold to achieve on-demand cooling and gas regulation.

6. The method for a system based on the comprehensive utilization of liquid nitrogen cold energy according to claim 5, characterized in that, In step e, when the temperature inside the grain silo is higher than the preset upper limit, the intelligent control unit increases the opening of the regulating valve and / or increases the fan speed; when the temperature inside the grain silo is lower than the preset lower limit, the regulating valve opening is reduced and / or the fan speed is decreased; when the oxygen concentration is higher than the preset upper limit, the liquid nitrogen flow rate is increased; when the oxygen concentration is lower than the preset lower limit, the liquid nitrogen flow rate is decreased.

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