A nitrogen circulation system for a grain bin

Abstract

The utility model relates to the field of grain storage, concretely relates to a granary nitrogen circulation system, including nitrogen recovery unit, nitrogen generation unit, nitrogen output unit and shallow round bin unit, shallow round bin unit includes at least two shallow round bins, is provided with upper ring flow pipe and lower ring flow pipe on the shallow round bin, and the lower ring flow pipe is connected with the upper ring flow pipe between adjacent shallow round bin's connection pipeline, the output end of nitrogen output unit and the upper ring flow pipe between first shallow round bin's connection have first delivery pipeline, the lower ring flow pipe between end shallow round bin and nitrogen recovery unit's first input end connection has recovery pipeline, and the second input end of nitrogen recovery unit is linked with outside air, nitrogen output unit carries out nitrogen delivery to shallow round bin unit through first delivery pipeline and upper ring flow pipe, and the oxygen in shallow round bin is discharged through lower ring flow pipe, and finally enters nitrogen recovery unit through recovery pipeline, and forms nitrogen circulation loop between shallow round bin and outside, reduces the storage cost.

Description

Technical Field

[0001] This utility model relates to the field of grain storage, specifically to a nitrogen circulation system for grain storage. Background Technology

[0002] Shallow circular silos are grain storage facilities that combine the characteristics of circular and shallow silos. Their name directly reflects their shape: the silo is cylindrical and relatively shallow. This design gives them unique advantages in structural stress: the circular shape ensures even stress distribution, resulting in significantly better wind and earthquake resistance than rectangular silos, while the shallower shape reduces construction difficulty and material costs, and facilitates daily maintenance and operation. Typical shallow circular silos are usually kept below 20 meters in height and have a relatively large diameter, giving them a "short and stout" appearance. A single silo can have a capacity of several thousand tons, depending on its specific dimensions, with a common configuration of around 5,000 tons, making them suitable for large-scale centralized grain storage.

[0003] Nitrogen filling of grain silos is a green grain storage technology that involves filling sealed grain silos with high-purity nitrogen to create a low-oxygen or anaerobic environment, thereby inhibiting grain respiration, delaying quality deterioration, and killing pests and mold. Its core principle lies in utilizing the chemical stability of nitrogen and its non-participation in biological metabolic reactions. By reducing the oxygen concentration inside the silo (usually controlled below 5%, or even as low as 2%), the grain enters a "dormant" state, while simultaneously destroying the survival conditions of pests and mold, achieving the goal of long-term safe storage. For example, the utility model patent application number CN202210030081.4, entitled "A Method and System for Slow-Release Modified Atmosphere Storage Using Air Columns and Airbags for Shallow Circular Grain Silos," discloses a nitrogen storage method with high replenishment efficiency; however, this method has low nitrogen utilization and high operating costs. Utility Model Content

[0004] The purpose of this invention is to provide a nitrogen circulation system for grain storage, which aims to improve the problems of low nitrogen utilization and high operating costs of conventional nitrogen storage controlled atmosphere methods.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A nitrogen circulation system for grain storage includes a nitrogen recovery unit, a nitrogen generation unit, a nitrogen output unit, and a shallow circular silo unit;

[0007] The shallow circular chamber unit includes at least two shallow circular chambers, each with an upper circulation pipe and a lower circulation pipe. The lower circulation pipe is connected to the upper circulation pipe of the adjacent shallow circular chamber via a connecting pipe. The output end of the nitrogen output unit is connected to the upper circulation pipe of the first shallow circular chamber via a first delivery pipe. The lower circulation pipe of the last shallow circular chamber is connected to the first input end of the nitrogen recovery unit via a recovery pipe.

[0008] The second input terminal of the nitrogen recovery unit is connected to the outside air, the output terminal of the nitrogen recovery unit is connected to the input terminal of the nitrogen generation unit, and the output terminal of the nitrogen generation unit is connected to the input terminal of the nitrogen output unit.

[0009] Furthermore, the nitrogen output unit includes a nitrogen storage tank, the output end of which is connected to an output pipe, the first delivery pipe is connected to the output pipe, and a first valve body is provided thereon;

[0010] The output pipe is also connected to a second conveying pipe. The end of the second conveying pipe is connected to the top of the shallow circular silo and passes through the top of the silo. It is also connected to an air supply pipe. The air supply pipe is vertically installed and extends to the middle of the grain pile. Air supply holes are opened on the periphery of the air supply pipe.

[0011] Furthermore, there are multiple air supply pipes, which are distributed in an equilateral triangular shape at intervals, and the distribution center of the multiple air supply pipes is located in the same vertical extension direction as the bottom center of the shallow circular chamber.

[0012] Furthermore, the spacing between adjacent air supply pipes located on the same hypotenuse decreases sequentially from both sides of the hypotenuse endpoints toward the midpoint of the hypotenuse.

[0013] Furthermore, the number of the second conveying pipes is the same as the number of shallow circular silos, and each is connected to a shallow circular silo.

[0014] A third valve body is installed on the second conveying pipeline.

[0015] Furthermore, the shallow circular chamber is equipped with an oxygen sensor network, which includes an upper network, a middle network, and a lower network.

[0016] The upper network includes a first sensor positioned above the grain pile and at the center of the shallow circular silo; the middle network is located 1-2 meters below the grain surface of the grain pile and includes four second sensors positioned at two mutually perpendicular diameter ends of the plane; the lower network is located 1-2 meters below the air supply pipe and includes five third sensors positioned at the center of the plane and at two mutually perpendicular diameter ends.

[0017] The distance between the third sensor located at both ends of the diameter and the inner wall of the shallow circular chamber is smaller than the distance between the second sensor and the inner wall of the shallow circular chamber.

[0018] Furthermore, one end of the output pipe is connected to a nitrogen storage tank, and the other end of the output pipe is connected to a first conveying pipe and a second conveying pipe. The middle section of the output pipe is located below the ground, and a protective sleeve is fitted where the output pipe passes through the ground.

[0019] Furthermore, the nitrogen recovery unit includes an air compressor, a front storage tank, and a refrigerated dryer. The recovery pipeline is connected to the first input end of the air compressor, and the second input end of the air compressor is connected to the outside air. The output end of the air compressor is connected to the front storage tank, the front storage tank is connected to the input end of the refrigerated dryer, and the output end of the refrigerated dryer is connected to the nitrogen generation unit.

[0020] Furthermore, the nitrogen generation unit includes a first generation branch and a second generation branch. Both the first generation branch and the second generation branch are equipped with adsorption towers and are respectively connected to the nitrogen recovery unit and the nitrogen output unit. The input and output ends of both the first generation branch and the second generation branch are equipped with fourth valves.

[0021] By adopting the above technical solution, this utility model has the following advantages compared with the prior art:

[0022] 1. The nitrogen recovery unit draws in air through the second input terminal and delivers the air to the nitrogen generation unit. After adsorbing oxygen and other component gases, the nitrogen generation unit outputs nitrogen to the nitrogen output unit. The nitrogen output unit delivers nitrogen to the shallow circular silo unit through the first delivery pipe and the upper circulation pipe. The oxygen in the shallow circular silo is discharged through the lower circulation pipe and finally enters the nitrogen recovery unit through the recovery pipe, forming a nitrogen circulation loop between the shallow circular silo and the outside, making full use of nitrogen and reducing storage costs.

[0023] 2. Since nitrogen is less dense than oxygen, the upper circulation pipe is used to transport nitrogen to the top of the shallow circular silo, ensuring that oxygen is fully discharged from top to bottom, avoiding oxygen residue and affecting the storage effect of grain. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the nitrogen circulation system for grain storage as described in this utility model;

[0025] Figure 2 This is a schematic diagram of the gas supply pipe distribution of the nitrogen circulation system in the grain warehouse described in this utility model;

[0026] Figure 3 This is a schematic diagram of the end structure of the gas supply pipe of the nitrogen circulation system for grain storage described in this utility model;

[0027] Figure 4 This is a schematic diagram of the oxygen sensor network distribution in the nitrogen circulation system of the grain silo described in this utility model;

[0028] Figure 5 This is a schematic cross-sectional view of the output pipeline assembly of the nitrogen circulation system for grain storage described in this utility model.

[0029] Explanation of reference numerals in the attached figures:

[0030] 1. Nitrogen recovery unit; 11. Air compressor; 111. First input terminal; 112. Second input terminal; 12. Front storage tank; 13. Refrigerated dryer; 14. Primary filter; 15. Secondary filter; 16. Tertiary filter; 17. Recovery pipeline;

[0031] 2. Nitrogen generation unit; 21. Adsorption tower; 22. Fourth valve body;

[0032] 3. Nitrogen output unit; 31. Nitrogen storage tank; 311. Output pipeline; 312. Second valve body; 313. Flow meter; 314. Pressure reducing valve; 315. Protective sleeve; 32. First delivery pipeline; 321. First valve body; 33. Second delivery pipeline; 331. Third valve body; 34. Gas supply pipe; 341. Gas supply port; 342. Opening section; 35. Fan;

[0033] 4. Shallow circular chamber unit; 41. Shallow circular chamber; 411. Upper circulation pipe; 412. Lower circulation pipe; 42. Connecting pipe; 43. Oxygen sensor network; 431. Upper network; 4311. First sensor; 432. Middle network; 4321. Second sensor; 433. Lower network; 4331. Third sensor;

[0034] 5. Ground. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this utility model clearer, the present utility model will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this utility model and are not intended to limit this utility model.

[0036] Additionally, it should be noted that the terms "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are all based on the orientation or positional relationship shown in the accompanying drawings. They are merely for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element of this utility model must have a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0037] When an element is referred to as being "fixed to," "set on," or "contained on" another element, it can be directly on or indirectly on that other element. When an element is referred to as being "connected to," it can be directly connected to or indirectly connected to that other element.

[0038] Unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0039] Example

[0040] Please refer to Figure 1-5 As shown, this embodiment provides a nitrogen circulation system for a grain silo, including a nitrogen recovery unit 1, a nitrogen generation unit 2, a nitrogen output unit 3, and a shallow circular silo unit 4. The shallow circular silo unit 4 includes at least two shallow circular silos 41, each with an upper circulation pipe 411 and a lower circulation pipe 412. A connecting pipe 42 connects the lower circulation pipe 412 to the upper circulation pipe 411 of the adjacent shallow circular silo 41. A first conveying pipe 32 connects the output end of the nitrogen output unit 3 to the upper circulation pipe 411 of the first shallow circular silo 41. A recovery pipe 17 connects the lower circulation pipe 412 of the last shallow circular silo 41 to the first input end 111 of the nitrogen recovery unit 1. The second input end 112 of the nitrogen recovery unit 1 is connected to the outside air. The output end of the nitrogen recovery unit 1 is connected to the input end of the nitrogen generation unit 2, and the output end of the nitrogen generation unit 2 is connected to the input end of the nitrogen output unit 3.

[0041] Nitrogen recovery unit 1 draws in air through the second input terminal 112 and delivers the air to nitrogen generation unit 2. Nitrogen generation unit 2 adsorbs oxygen and other component gases, then outputs nitrogen to nitrogen output unit 3. Nitrogen output unit 3 delivers nitrogen to shallow circular silo unit 4 through the first delivery pipe 32 and the upper circulation pipe 411. Oxygen in shallow circular silo 41 is discharged through the lower circulation pipe 412 and finally enters nitrogen recovery unit 1 through recovery pipe 17, forming a nitrogen circulation loop between shallow circular silo 41 and the outside, fully utilizing nitrogen and reducing storage costs. Furthermore, nitrogen has a lower density than oxygen; by using the upper circulation pipe 411 to deliver nitrogen to the upper end of shallow circular silo 41, it ensures sufficient oxygen discharge from top to bottom, avoiding oxygen residue that could affect grain storage. Similarly, nitrogen can be output using the lower circulation pipe 412, and oxygen can be discharged using the upper circulation pipe 411.

[0042] Please refer to Figure 1As shown, the nitrogen output unit 3 includes a nitrogen storage tank 31. The output end of the nitrogen storage tank 31 is connected to an output pipe 311. A first conveying pipe 32 is connected to the output pipe 311 and is equipped with a first valve body 321. A second conveying pipe 33 is also connected to the output pipe 311. The end of the second conveying pipe 33 is connected to the top of the shallow circular silo 41 and passes through the top of the silo. It is connected to a gas supply pipe 34. The gas supply pipe 34 is vertically arranged and extends to the middle of the grain pile. Gas supply holes 341 are opened on the periphery of the gas supply pipe 34.

[0043] Specifically, in this embodiment, the output pipe 311 is equipped with a second valve body 312, a flow meter 313, and a pressure reducing valve 314. The second valve body 312 is located at the end of the output pipe 311 near the first conveying pipe 32 and the second conveying pipe 33. The first conveying pipe 32 is connected to the upper circulation pipe 411, through which nitrogen gas is conveyed into the shallow circular silo 41. The second conveying pipe 33 conveys nitrogen gas through the gas supply pipe 34 and the gas supply hole 341 into the shallow circular silo 41. The upper circulation pipe 411 serves to expel air from the inside of the shallow circular silo 41, while the gas supply pipe 34 extends to the middle of the grain pile, conveying nitrogen gas to the middle of the grain pile. This achieves three-dimensional uniform nitrogen filling, improves the nitrogen filling efficiency in the shallow circular silo 41, shortens the concentration equilibrium time, improves the uniformity of gas distribution in the deeper layers of the grain pile, effectively overcomes the resistance of the grain pile, and delivers nitrogen gas to every corner, avoiding the problem of incomplete pest control caused by uneven concentration. Furthermore, the top end of the air supply pipe 34 is connected to the second conveying pipe 33, meaning that the air inlet end of the air supply pipe 34 is the top end, which effectively prevents the grain husk from entering the air supply pipe 34 and causing blockage of the air inlet port of the air supply pipe 34, thus affecting the nitrogen filling efficiency.

[0044] Please refer to Figure 2 As shown, there are multiple air supply pipes 34, which are distributed in an equilateral triangular shape at intervals. The distribution center of the multiple air supply pipes 34 is located in the same vertical extension direction as the center of the bottom circle of the shallow circular chamber 41. The equilateral triangular distribution, with air supply holes 341 on its periphery, further ensures uniform nitrogen filling in all directions of the shallow circular chamber 41 in the horizontal direction, avoiding dead zones.

[0045] Please refer to Figure 2As shown, the spacing between adjacent air supply pipes 34 located on the same hypotenuse decreases sequentially from both sides of the hypotenuse endpoints towards the midpoint of the hypotenuse. Because the air supply pipes 34 are distributed in an equilateral triangular shape, the spacing between the air supply pipe 34 located at the midpoint of the hypotenuse and the inner wall of the shallow circular silo 41 is larger than the spacing between the air supply pipe 34 located at the hypotenuse endpoints and the inner wall of the shallow circular silo 41. By controlling the spacing between the air supply pipes 34 on the hypotenuse within the midpoint range to be smaller than the spacing on both sides, the density of the air supply pipes 34 at the midpoint of the hypotenuse is increased, thereby increasing the nitrogen supply at the midpoint and ensuring sufficient nitrogen supply to the edge of the grain pile at the midpoint, further improving the uniformity of nitrogen supply.

[0046] Furthermore, the total area of ​​the air supply holes 341 on a single air supply pipe 34 is equal to the cross-sectional area of ​​the air supply pipe 34. The opening diameter of the air supply holes 341 is controlled to prevent them from being too large, which would cause all the nitrogen to flow out from the upper end of the air supply pipe 34, affecting the nitrogen supply effect at the bottom of the pipe. This ensures that nitrogen is transported over long distances within the air supply pipe 34 under arch pressure and seeps evenly from all the air supply holes 341, thus improving the nitrogen supply effect.

[0047] Please refer to Figure 3 As shown, the bottom of the gas supply pipe 34 is provided with an opening section 342, and the top of the opening section is located below the grain surface of the grain pile, so that the gas supply pipe 34 only supplies nitrogen to the bottom of the grain pile, and the top of the grain pile is only supplied with nitrogen by the upper circulation pipe 411, thereby improving the nitrogen transport efficiency inside the grain pile.

[0048] The number of second conveying pipes 33 is the same as the number of shallow circular chambers 41, and they are connected to the shallow circular chambers 41 respectively. A third valve body 331 is provided on each of the second conveying pipes 33. In this embodiment, a blower 35 is provided on both the second conveying pipe 33 and the first conveying pipe 32, driving nitrogen gas to move within them. The second conveying pipes 33 form nitrogen-filling branches. The number of second conveying pipes 33 is the same as the number of shallow circular chambers 41, making the nitrogen-filling branches of each shallow circular chamber 41 independent. By controlling the opening degree of each third valve body 331, the nitrogen flow rate of the corresponding nitrogen-filling branch of each shallow circular chamber 41 is controlled, thereby adjusting the opening degree of the corresponding nitrogen-filling branch in real time according to the nitrogen content of each shallow circular chamber 41, providing better flexibility.

[0049] Please refer to Figure 4As shown, an oxygen sensor network 43 is provided inside the shallow circular silo 41. The oxygen sensor network 43 includes an upper network 431, a middle network 432, and a lower network 433. The upper network 431 includes a first sensor 4311, which is located above the grain pile and at the center of the shallow circular silo 41. The middle network 432 is located 1-2m below the grain surface of the grain pile and includes four second sensors 4321, which are located at the two mutually perpendicular diameter ends of the plane. The lower network 433 is located 1-2m below the air supply pipe 34 and includes five third sensors 4331, which are located at the center of the plane and at the two mutually perpendicular diameter ends. The distance between the third sensors 4331 located at the diameter ends and the inner wall of the shallow circular silo 41 is smaller than the distance between the second sensors 4321 and the inner wall of the shallow circular silo 41.

[0050] In this embodiment, the middle layer network 432 is located 1m below the grain surface; similarly, the middle layer network 432 can also be located 2m below the grain surface. The lower layer network 433 is located 1m below the air supply pipe 34; similarly, the lower layer network 433 can also be located 2m below the air supply pipe 34. A three-layer sensor network is set up: the upper layer network 431 detects the oxygen content in the space above the grain pile; the middle layer network 432 detects the oxygen content at a position 1m below the grain surface, and second sensors 4321 distributed around the perimeter detect multiple positions on the same horizontal plane; the lower layer network 433 detects the oxygen content at a position 1m below the air supply pipe 34, and third sensors 4331 distributed around the perimeter and center detect multiple positions on the same horizontal plane. A three-dimensional detection network is formed, thereby achieving accurate detection of the oxygen content in the shallow circular silo 41. Furthermore, by controlling the distance between the lower third sensor 4331 and the side wall of the Zener circular silo to be small, detection of the bottom edge position is achieved, avoiding detection blind spots and further improving detection accuracy.

[0051] Please refer to Figure 5 As shown, one end of the output pipe 311 is connected to the nitrogen storage tank 31, and the other end is connected to the first conveying pipe 32 and the second conveying pipe 33. The middle section of the output pipe 311 is located below the ground level 5, and a protective sleeve 315 is fitted at the point where the output pipe 311 passes through the ground level 5. The output pipe 311 is buried underground, making way for equipment in the grain storage area, improving the space utilization of the grain storage area, and protecting the output pipe 311 from damage that could affect nitrogen delivery. Furthermore, the protective sleeve 315 at the point where the output pipe 311 exits the ground level 5 protects the output pipe 311 from damage caused by ground subsidence.

[0052] Please refer to Figure 1 As shown, the nitrogen recovery unit 1 includes an air compressor 11, a front storage tank 12, and a refrigerated dryer 13. A recovery pipeline 17 is connected to the first input terminal 111 of the air compressor 11, and the second input terminal 112 of the air compressor 11 is connected to external air. The output terminal of the air compressor 11 is connected to the front storage tank 12, which is connected to the input terminal of the refrigerated dryer 13. The output terminal of the refrigerated dryer 13 is connected to the nitrogen generation unit 2. The front storage tank 12 stores the discharged air, nitrogen, and external air absorbed by the air compressor 11, allowing for the secondary use of air and nitrogen and further reducing grain storage costs.

[0053] The nitrogen generation unit 2 includes a first generation branch and a second generation branch. Both the first and second generation branches are equipped with adsorption towers 21, which are respectively connected to the nitrogen recovery unit 1 and the nitrogen output unit 3. Specifically, the input and output ends of the adsorption towers 21 are connected to the output end of the refrigerated dryer 13 and the nitrogen storage tank 31, respectively. A fourth valve 22 is installed at both the input and output ends of both the first and second generation branches. The adsorption towers 21 selectively adsorb nitrogen molecules, allowing nitrogen to pass through, thereby providing nitrogen to the nitrogen output unit 3. By controlling the connection of either the first generation branch to the nitrogen recovery unit 1 and the nitrogen output unit 3, or the second generation branch to the nitrogen recovery unit 1 and the nitrogen output unit 3, continuous nitrogen generation is achieved, improving nitrogen supply efficiency.

[0054] The specific control steps are as follows;

[0055] S1 air compressor 11 works, driving air into nitrogen recovery unit 1 for primary filtration 14, refrigerated dryer 13, secondary filtration 15 and tertiary filtration 16.

[0056] After passing through the three-stage filter 16, the air from S2 enters the nitrogen generation unit 2, and the fourth valve body 22 alternately connects the first generation branch and the second generation branch.

[0057] S3 nitrogen generation unit 2 delivers nitrogen storage tank 31, blower 35 works, drives nitrogen through first delivery pipe 32 and second delivery pipe 33 into shallow circular silo 41, and discharges air from shallow circular silo 41.

[0058] S31 sets the target oxygen concentration a% and the target oxygen reduction time, and the PLC control cabinet obtains the oxygen content information at each location through the oxygen sensor network 43.

[0059] The S32 PLC control cabinet controls the full opening of the second valve body 312, controls the high-level output of the blower 35, and drives nitrogen into the shallow circular chamber 41; in the initial state, it controls the full opening of the second valve body 312 to ensure that the output pipeline has a high nitrogen flow rate, and maximizes the nitrogen filling within the target oxygen reduction time.

[0060] S33 detects the difference between the oxygen content at the location of the lower layer network 433 and the oxygen content at the location of the middle layer network 432 in real time. If the difference between the oxygen content of the lower layer and the oxygen content of the middle layer exceeds 4%, the fan 35 of the first conveying pipeline will maintain a medium-high level of operation, and the fan 35 of the corresponding second conveying pipeline will adopt a high level of output.

[0061] When the difference is less than 4%, the blower 35 of the second output pipeline will switch to a medium-high output. During the nitrogen filling process, the difference in oxygen content at each location will be checked. If uneven nitrogen filling occurs, i.e., the difference in oxygen content is too large, the power of the blower 35 of the second output pipeline will be increased to improve the nitrogen filling rate inside the grain pile, thereby ensuring the uniformity of nitrogen filling and improving the nitrogen filling efficiency to ensure that the target oxygen reduction time is met.

[0062] When the oxygen concentration at each sensor location is below (a+10)%, the PLC control cabinet calculates whether the rate of change in oxygen content meets the target oxygen reduction time. If it does, the fan 35 maintains a medium-high output. If an individual shallow silo 41 does not meet the requirement, the fan 35 in the second conveying pipeline of the corresponding shallow silo 41 is controlled to operate at a high output. If all shallow silos 41 do not meet the requirement, the fans 35 in both the first and second conveying pipelines are controlled to operate at a high output. In the early stage, the two fans 35 are controlled to operate at medium-high power for rapid nitrogen filling, quickly reducing the oxygen content in the shallow silos 41. In the middle stage, it is judged whether the oxygen reduction time can be met. Since the second conveying pipelines 33 of each shallow silo 41 are independent of each other, if an individual shallow silo 41 cannot meet the oxygen reduction time requirement, the individual motor is controlled to operate at high power, making the overall nitrogen filling more flexible, reducing energy loss and costs while meeting the target oxygen reduction time.

[0063] When the oxygen concentration at each sensor location is lower than (a+2)%, the PLC control cabinet controls the fans 35 of the first and second conveying pipelines to use medium-speed output; under the premise of meeting the oxygen reduction time in the later stage, low-power output is carried out to further reduce the cost of grain storage.

[0064] S4 When the oxygen concentration at each sensor location is lower than a%, the PLC control cabinet controls the fans 35 of the first and second conveying pipelines to use low-speed output.

[0065] S5 nitrogen generation unit 2 is intermittently switched on a single branch;

[0066] When the oxygen sensor network 43 detects that the oxygen content exceeds (a+2)%, the PLC control cabinet controls the fan 35 of the second delivery pipeline corresponding to the shallow circular silo 41 to output at medium speed, and returns to step S3 until the nitrogen filling is completed and the machine is shut down. After the target oxygen concentration a% is met, nitrogen is generated intermittently, and the fan 35 operates at low speed to ensure that the shallow circular silo 41 is maintained within the target oxygen concentration range.

[0067] The above description is merely a preferred embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the scope of the claims.

Claims

1. A nitrogen circulation system for grain storage, characterized in that, It includes a nitrogen recovery unit, a nitrogen generation unit, a nitrogen output unit, and a shallow circular silo unit; The shallow circular chamber unit includes at least two shallow circular chambers, each with an upper circulation pipe and a lower circulation pipe. The lower circulation pipe is connected to the upper circulation pipe of the adjacent shallow circular chamber via a connecting pipe. The output end of the nitrogen output unit is connected to the upper circulation pipe of the first shallow circular chamber via a first delivery pipe. The lower circulation pipe of the last shallow circular chamber is connected to the first input end of the nitrogen recovery unit via a recovery pipe. The second input terminal of the nitrogen recovery unit is connected to the outside air, the output terminal of the nitrogen recovery unit is connected to the input terminal of the nitrogen generation unit, and the output terminal of the nitrogen generation unit is connected to the input terminal of the nitrogen output unit.

2. The grain storage nitrogen circulation system according to claim 1, characterized in that: The nitrogen output unit includes a nitrogen storage tank, the output end of which is connected to an output pipe. The first delivery pipe is connected to the output pipe and is equipped with a first valve body. The output pipe is also connected to a second conveying pipe. The end of the second conveying pipe is connected to the top of the shallow circular silo and passes through the top of the silo. It is also connected to an air supply pipe. The air supply pipe is vertically installed and extends to the middle of the grain pile. Air supply holes are opened on the periphery of the air supply pipe.

3. The grain storage nitrogen circulation system according to claim 2, characterized in that: The number of air supply pipes is multiple, and the multiple air supply pipes are distributed in an equilateral triangular shape at intervals. The distribution center of the multiple air supply pipes and the bottom center of the shallow circular chamber are located in the same vertical extension direction.

4. The grain silo nitrogen circulation system according to claim 3, characterized in that: The spacing between adjacent air supply pipes located on the same hypotenuse decreases sequentially from both sides of the hypotenuse endpoints toward the midpoint of the hypotenuse.

5. The grain storage nitrogen circulation system according to claim 2, characterized in that: The number of the second conveying pipes is the same as the number of shallow circular silos, and each pipe is connected to a shallow circular silo. A third valve body is installed on the second conveying pipeline.

6. The grain storage nitrogen circulation system according to claim 2, characterized in that: The shallow circular chamber is equipped with an oxygen sensor network, which includes an upper network, a middle network, and a lower network. The upper network includes a first sensor positioned above the grain pile and at the center of the shallow circular silo; the middle network is located 1-2 meters below the grain surface of the grain pile and includes four second sensors positioned at two mutually perpendicular diameter ends of the plane; the lower network is located 1-2 meters below the air supply pipe and includes five third sensors positioned at the center of the plane and at two mutually perpendicular diameter ends. The distance between the third sensor located at both ends of the diameter and the inner wall of the shallow circular chamber is smaller than the distance between the second sensor and the inner wall of the shallow circular chamber.

7. The grain storage nitrogen circulation system according to claim 2, characterized in that: One end of the output pipe is connected to a nitrogen storage tank, and the other end of the output pipe is connected to a first conveying pipe and a second conveying pipe. The middle section of the output pipe is located below the ground, and a protective sleeve is fitted where the output pipe passes through the ground.

8. The grain storage nitrogen circulation system according to claim 1, characterized in that: The nitrogen recovery unit includes an air compressor, a front storage tank, and a refrigerated dryer. The recovery pipeline is connected to the first input end of the air compressor, and the second input end of the air compressor is connected to the outside air. The output end of the air compressor is connected to the front storage tank, the front storage tank is connected to the input end of the refrigerated dryer, and the output end of the refrigerated dryer is connected to the nitrogen generation unit.

9. The grain storage nitrogen circulation system according to claim 1, characterized in that: The nitrogen generation unit includes a first generation branch and a second generation branch. Both the first generation branch and the second generation branch are equipped with adsorption towers and are respectively connected to a nitrogen recovery unit and a nitrogen output unit. The input and output ends of both the first generation branch and the second generation branch are equipped with fourth valves.

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