Accurate and stable feeding method and system for negative pressure dense phase pneumatic conveying

Abstract

The present invention belongs to the technical field of pneumatic conveying, and specifically relates to a precise and stable feeding method and system for negative pressure dense phase pneumatic conveying, which monitors the deviation between the average powder conveying flow rate and the target flow rate during the sampling period, changes the outlet diameter of the silo through the regulating mechanism at the silo outlet, and roughly adjusts the powder flow rate at the silo outlet. At the same time, the loosening air flow rate regulating device adjusts the loosening air flow rate at the silo outlet to achieve precise and stable feeding of the sending silo; on the other hand, a pressure sensor is used to monitor the air pressure above the silo P 1 and lower air pressure P 2. Feedback signal, adjust the air pressure balance of the sending bin to realize automatic feeding; during the feeding process, the loosening wind provides 10% to 20% of the target air supply volume, avoiding the problem of air pressure balance arch phenomenon in the sending bin caused by too much loosening wind volume in the traditional process affecting the feeding stability; the present invention effectively improves the feeding accuracy and stability of the negative pressure dense phase pneumatic conveying system.

Description

Technical Field

[0001] The present invention belongs to the technical field of negative pressure dense phase pneumatic conveying, and in particular relates to a negative pressure dense phase precise and stable feeding method and a system thereof. Background Art

[0002] The negative pressure pneumatic conveying system uses air below atmospheric pressure as the conveying medium. The system relies on the suction effect of the air source machinery to form a certain vacuum in the tube bundle, and uses the moving air with the necessary flow rate to transport the material from a certain place through the pipeline to a destination at a certain distance. During the negative pressure conveying process, the conveying gas will not escape into the atmosphere. At the same time, the conveying gas will pass through the air source machinery after conveying the material, which will not pollute the material. Therefore, it is widely used in conveying toxic or easily polluting powdery and granular materials and food and pharmaceutical particles.

[0003] In industrial applications, the feeding speed of negative pressure pneumatic conveying systems is usually regulated by a single valve or by a valve combined with loose air. When conveying powders that are prone to sticking and agglomeration, rat holes, bridging and segregation are prone to occur in the delivery bin. Due to its limited adjustment accuracy, a single valve cannot achieve precise control of the feeding speed. In the valve combined with loose air adjustment method, the loose air flow control method is not yet clear. When the loose air volume is too large, an air pressure balance arch will appear in the bin, and the discharge of the delivery bin will be intermittent jet flow, and the feeding stability is poor.

[0004] Patent CN117602382B provides a negative pressure pneumatic conveying rotary feeder, including: a transmission box and an anti-clogging mechanism, which can convey materials at the upper and lower ports of the exhaust chamber through a spiral feeder, effectively avoiding the blockage of materials at the connection points of the components. At the same time, under the action of the pusher and the second transmission component, the material falling into the acceleration chamber can be continuously scattered and pushed to avoid affecting the normal transportation of the material, and effectively prevent the motor and Roots blower from being damaged due to long-term overload operation caused by material blockage. However, this invention cannot achieve precise adjustment of the feeding amount.

[0005] Therefore, it is urgent to design a precise and stable feeding method and system for negative pressure dense phase pneumatic conveying to solve the problems of poor feeding accuracy and low stability of existing negative pressure dense phase pneumatic conveying systems.

[0006] It should be noted that the above information disclosed in this background technology section is only for understanding the background technology of the present application concept, and therefore, it may contain information that does not constitute the prior art. Summary of the invention

[0007] The purpose of the present invention is to provide a precise and stable feeding method and system for negative pressure dense phase pneumatic conveying to solve the above technical problems.

[0008] In a first aspect, the present invention provides a precise and stable feeding method for negative pressure dense-phase pneumatic conveying. The deviation between the average powder conveying flow rate and the target flow rate within a sampling time period is obtained. The opening degree of the silo outlet is roughly adjusted through an adjusting mechanism to adjust the powder flow rate. At the same time, the loosening air flow control device adjusts the loosening air flow rate at the silo outlet to achieve precise and stable discharging of the silo. The specific steps are as follows:

[0009] Step A: The pressure control module opens the balance air solenoid valve and the air shut-off valve, adds materials to the silo until the target filling amount is reached, and stops feeding.

[0010] Step B: Adjust the conveying air volume to 80% - 90% of the target air volume. The powder flow rate control module controls the operation of the adjusting mechanism and slowly increases the diameter of the silo outlet. Q 0 Measure the powder conveying flow rate.

[0011] The powder flow rate control module calculates and sets the average powder mass flow rate within the segmented sampling time. G s (t) ; τ where is the target powder conveying flow rate,

[0012] is the powder conveying flow rate; a is the deviation of the powder conveying flow rate. ;

[0013] is the serial number of the time period. The first time period is denoted as G 0 , the second time period is denoted as G s (t) , and so on. When a > 5%, the adjusting mechanism continuously increases the opening degree of the silo outlet until 2% < a ≤ 5%. When 2% < a ≤ 5%, the powder flow rate control module sends a signal, and the adjusting mechanism maintains the current opening degree of the silo outlet. When |a| ≤ 2%, the powder flow rate control module sends a signal, and the loosening air flow control device maintains the loosening air at the current flow rate.

[0014] When -5% ≤ a < -2%, the powder flow rate control module sends a signal, and the loosening air flow control device reduces the loosening air flow rate until |a| ≤ 2%.

[0015]

[0016]

[0017]

[0018] ​​​When a<-5%, close the loose air flow control device. If a<-5% is still present, the powder flow control module sends a signal and the regulating mechanism reduces the opening of the silo outlet until |a|≤2%.

[0019] In an alternative embodiment, the air pressure at the top of the silo is monitored P 1 , through the formula: Δ P 1 =P a -P 1 >P 0 , calculate the pressure difference between the silo and the outside air pressure ΔP 1 , where P a is atmospheric pressure, P 0 To set the maximum allowable pressure difference;

[0020] If the above equation is established, the pressure control module controls the balance air solenoid valve to increase its opening to adjust the relative balance between the silo and the external air pressure to ensure smooth feeding of the silo.

[0021] In an alternative embodiment, the air pressure at the bottom of the silo is monitored P 2 , when the balance air solenoid valve is opened to 100%, and the pressure difference ΔP 1 Still greater than P 0 ,and P 1 ≈ P 2 , it is judged that the material level in the silo is too low, and the pressure control module sends a signal to control the air shut-off valve to open and supply material into the silo.

[0022] In an optional implementation, the loosening air volume is 10% to 20% of the design target air supply volume.

[0023] In an optional embodiment, the powder calculates the average mass flow rate segment collection time τ 2s~10s, acquisition frequency is 5Hz~500Hz;

[0024] In a second aspect, the present invention provides a precise and stable feeding system for negative pressure dense phase pneumatic conveying, which is used to implement the precise and stable feeding method as described above, comprising:

[0025] The sending bin is divided into a silo section and a bucket section, and a discharge port is provided at the bottom of the bucket section;

[0026] An adjusting mechanism, the movable end of which is suitable for sliding to adjust the opening of the discharge port;

[0027] A plurality of loosening air flow control devices, each having a double-layer loosening air distribution plate, wherein the air outlet of the double-layer loosening air distribution plate faces the discharge port;

[0028] A powder flow meter device, which is used to measure the mass flow of the material discharged from the discharge port G s ;

[0029] A powder flow control module, wherein the regulating mechanism, the loosening air flow control device and the powder flow meter device are all electrically connected to the powder flow control module;

[0030] Breathing valve and balance air solenoid valve are used to adjust the pressure in the upper part of the silo section;

[0031] Two pressure sensors are installed at the upper and lower parts of the silo section to measure the air pressure at the corresponding positions. P 1 and P 2 ;

[0032] The pressure control module, the breathing valve, the balance wind solenoid valve, the air shut-off valve and the pressure sensor are all electrically connected to the pressure control module.

[0033] In an optional embodiment, the adjustment mechanism includes an adjustment member and a servo electric cylinder, the adjustment member is inserted into the inner side of the discharge port, and the servo electric cylinder is transmission-connected to the adjustment member via a screw rod;

[0034] The servo electric cylinder is electrically connected to the powder flow control module and is used to adjust the height of the adjusting member to adjust the opening of the discharge port.

[0035] In an optional embodiment, the loosening air flow control device further includes a loosening air chamber and a loosening air solenoid valve, the loosening air chamber is arranged on the outer wall of the bucket section, and the loosening air chamber is connected to the double-layer loosening air distribution plate;

[0036] The loosening air solenoid valve is communicated with the loosening air chamber, and the loosening air solenoid valve is electrically connected to the powder flow control module for adjusting the loosening air flow rate.

[0037] In an optional embodiment, the loosening air distribution height range H1 of the double-layer loosening air distribution plate is not less than 65% of the bucket section height H2.

[0038] In an optional embodiment, the bottom of the discharge port is connected to an acceleration chamber, one side of the acceleration chamber is provided with a conveying air solenoid valve, and the conveying air solenoid valve is electrically connected to the powder flow control module for adjusting the conveying air volume;

[0039] The discharge end of the acceleration chamber is connected to a vacuum pump, and the powder flow meter device is installed between the acceleration chamber and the vacuum pump;

[0040] A separation material collecting tank and a cyclone dust collector are sequentially arranged between the powder flow meter device and the vacuum pump.

[0041] The beneficial effect of the present invention is that the present invention changes the outlet diameter of the silo through the regulating mechanism of the silo outlet, roughly adjusts the powder flow rate at the silo outlet, and at the same time, the loosening air flow rate control device adjusts the loosening air flow rate at the silo outlet to achieve accurate and stable material discharge from the sending silo; on the other hand, the pressure sensor is used to monitor the air pressure above the silo P 1 and lower air pressure P 2 , feedback signal, adjust the air pressure balance of the sending bin, and realize automatic feeding; during the feeding process, the loosening wind provides 10% to 20% of the target air supply volume, avoiding the problem of air pressure balance arch phenomenon in the sending bin caused by too much loosening wind volume in the traditional process affecting the feeding stability; the present invention effectively improves the feeding accuracy and stability of the negative pressure dense phase pneumatic conveying system.

[0042] Other features and advantages of the present invention will be described in the following description, and partly become apparent from the description, or understood by practicing the present invention. The purpose and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 A schematic diagram of a negative pressure dense phase pneumatic conveying precision feeding system provided in an embodiment of the present disclosure;

[0046] Figure 2 This is a schematic diagram of the sending bunker section and the silo section.

[0047] In the figure:

[0048] 1. Sending bin; 11. Discharging port; 12. Breathing valve; 13. Balance air solenoid valve; 14. Air shut-off valve; 15. Silo section; 16. Bucket section;

[0049] 21. Adjustment part; 22. Servo electric cylinder;

[0050] 31. Loose air chamber; 32. Double-layer loose air distribution plate; 33. Loose air solenoid valve;

[0051] 4. Powder flow meter device;

[0052] 5. Acceleration chamber; 51. Delivery air solenoid valve;

[0053] 6. Vacuum pump; 61. Separation and collection tank; 62. Cyclone dust collector; 63. Filter;

[0054] 71. Pressure control module; 72. Powder flow control module;

[0055] 8. Pressure sensor. DETAILED DESCRIPTION

[0056] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0057] According to research, the feeding speed of negative pressure pneumatic conveying systems in industrial applications is usually regulated by a single valve or by a valve combined with loose air. When conveying powders that are prone to sticking and agglomeration, rat holes, bridging and segregation are prone to occur in the delivery bin. Due to its limited adjustment accuracy, a single valve cannot achieve accurate control of the feeding speed. In the valve combined with loose air adjustment method, the loose air flow control method is not yet clear. When the loose air volume is too large, a pressure balance arch will appear in the bin, and the discharge from the delivery bin will be an intermittent jet flow, and the feeding stability is poor.

[0058] In the following, some embodiments of the present invention are described in detail in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. In addition, in the accompanying drawings, in order to effectively describe the technical content, the thickness of the components can be exaggerated or reduced.

[0059] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0060] Based on the above research, the present disclosure provides a precise and stable feeding method for negative pressure dense phase pneumatic conveying, which can obtain the powder sampling time period. τThe deviation between the average conveying flow rate inside and the target flow rate is used to roughly adjust the opening degree of the silo outlet through the adjusting mechanism to adjust the powder flow rate. At the same time, the loosening air flow control device is adjusted to regulate the loosening air flow rate at the silo outlet, so as to achieve accurate and stable discharging of the silo. The specific steps are as follows:

[0061] Step A: The pressure control module 71 opens the balance air solenoid valve 13 and the air shut-off valve 14, adds materials to the silo until the target filling amount is reached, and stops feeding;

[0062] Step B: Adjust the conveying air volume to 80% - 90% of the target air volume. The powder flow control module 72 controls the operation of the adjusting structure and slowly increases the diameter of the silo outlet, that is, the opening degree; Q 0 Measure the powder conveying flow rate in real time. The powder flow control module calculates and sets the segmented acquisition time, and calculates the average powder mass flow rate within the time period;

[0063] Measure the powder conveying flow rate in real time G s (t) The powder flow control module calculates and sets the segmented acquisition time τ The average powder mass flow rate within ;

[0064] ; ;

[0065] In the formula, G 0 is the target powder conveying flow rate, G s (t) is the powder conveying flow rate, is the serial number of the time period. The first time period is recorded as and the second time period is recorded as , and so on; a is the deviation of the powder conveying flow rate;

[0066] When a > 5%, continuously increase the opening degree of the silo outlet until 2% < a ≤ 5%;

[0067] When 2% < a ≤ 5%, the powder flow control module 72 sends a signal, and the adjusting mechanism maintains the current opening degree of the silo outlet;

[0068] Step C: Adjust the loosening air flow control device to increase the loosening air flow rate. When |a| ≤ 2%, the powder flow control module 72 sends a signal, and the loosening air flow control device keeps the loosening air running at the current flow rate;

[0069] When - 5% ≤ a < - 2%, the powder flow control module 72 sends a signal, and the loosening air flow control device reduces the loosening air flow rate until |a| ≤ 2%;

[0070] When a<-5%, the loose air flow control device is closed. If a<-5% is still present, the powder flow control module 72 sends a signal, and the regulating mechanism reduces the opening of the silo outlet until |a|≤2%;

[0071] In at least one embodiment, in order to ensure stable feeding at the outlet of the silo, when performing step A, the air pressure at the top of the silo is monitored in real time. P 1. Through the formula: ΔP 1 =P a -P 1 >P 0 , calculate the pressure difference between the silo and the outside air pressure ΔP 1 , where P a is atmospheric pressure, P 0 To set the maximum allowable pressure difference. If the above formula is established, the pressure control module 71 controls the balance air solenoid valve 13 to increase the opening to adjust the relative balance between the silo and the external air pressure to ensure smooth feeding of the silo. On the other hand, in order to ensure that the material in the silo is full, it is also necessary to monitor the air pressure at the bottom of the silo. P 2 , when the balance air solenoid valve 13 is opened to 100%, and the pressure difference ΔP 1 Still greater than P 0 ,and P 1 ≈ P 2 , it is determined that the material level in the silo is too low, and the pressure control module 71 sends a signal to control the air shut-off valve 14 to open and supply material into the silo.

[0072] In some embodiments, step A1 can be added between step A and step B to adjust the height of the movable end of the mechanism when the silo outlet opening is fully closed or fully open. H 0 and H 4 , and is input into the powder flow control module 72 to assist the powder flow control module 72 in controlling the stroke of the regulating mechanism and the opening of the silo outlet.

[0073] In at least one embodiment, the loosening air volume is 10% to 20% of the design target air supply volume, which effectively avoids the silo air pressure balance arch phenomenon caused by excessive loosening air volume.

[0074] In some embodiments, the segmented acquisition time τ for calculating the average mass flow rate of the powder is 2s to 10s, and the acquisition frequency is 5Hz to 500Hz.

[0075] In addition, in at least one embodiment, the present disclosure also provides a precise and stable feeding system for negative pressure dense phase pneumatic conveying, which is used to perform the precise and stable feeding method shown above, referring to Figure 1 , which includes a sending bin 1, which can be divided into a silo section 15 and a bucket section 16, and a discharge port 11 is provided at the bottom of the bucket section 16; an adjusting mechanism, whose movable end is suitable for sliding to adjust the opening of the discharge port 11; a plurality of loose air flow control devices, which have a double-layer loose air distribution plate 32, and the air outlet of the double-layer loose air distribution plate 32 faces the discharge port 11; a powder flow meter device 4, which is used to measure the mass flow of the material discharged from the discharge port 11 G s ; The powder flow control module 72, the regulating mechanism, the loose air flow control device and the powder flow meter device 4 are all electrically connected to the powder flow control module 72. The breathing valve 12 and the balance air solenoid valve 13 are used to adjust the pressure on the upper part of the silo section 15; two pressure sensors 8 are respectively arranged at the upper and lower parts of the silo section 15 to measure the air pressure at the corresponding positions P 1 and P 2 The pressure control module 71 , the breathing valve 12 , the balance wind solenoid valve 13 , the air shut-off valve 14 , and the two pressure sensors 8 are all electrically connected to the pressure control module 71 .

[0076] Reference Figure 1 In at least one embodiment, the adjustment mechanism includes an adjustment member 21 and a servo electric cylinder 22. The adjustment member 21 is inserted into the inner side of the discharge port 11, and the servo electric cylinder 22 is connected to the adjustment member 21 through a screw rod; the servo electric cylinder 22 is electrically connected to the powder flow control module 72, and is used to adjust the height of the adjustment member 21 to adjust the opening of the discharge port. Preferably, the adjustment member 21 should adopt a conical valve, which is conducive to reducing the rat hole bridging phenomenon in the sending bin 1. Preferably, the adjustment accuracy of the servo electric cylinder 22 is not less than 0.01mm.

[0077] Reference Figure 1 , in at least one embodiment, the loosening air flow control device further includes a loosening air chamber 31 and a loosening air solenoid valve 33, the loosening air chamber 31 is arranged on the outer wall of the bucket section 16, and the loosening air chamber 31 is connected to the double-layer loosening air distribution plate 32;

[0078] Reference Figure 1 The loosening air solenoid valve 33 is communicated with the loosening air chamber 31, and the loosening air solenoid valve 33 is electrically connected to the powder flow control module 72 for adjusting the loosening air flow rate.

[0079] Reference Figure 2In some embodiments, the loose air distribution height range H1 of the double-layer loose air distribution plate 32 is not less than 65% of the height H2 of the silo section 16, and the height of the silo section 15 is H3.

[0080] Reference Figure 1 In some embodiments, the bottom of the discharge port 11 is connected to an acceleration chamber 5, and one side of the acceleration chamber 5 is provided with a conveying air solenoid valve 51, which is electrically connected to a powder flow control module 72 for adjusting the conveying air volume.

[0081] Reference Figure 1 In some embodiments, the discharge end of the acceleration chamber 5 is connected to a vacuum pump 6, and the powder flow meter device 4 is installed between the acceleration chamber 5 and the vacuum pump 6; a separation receiving tank 61 and a cyclone dust collector 62 are sequentially arranged between the powder flow meter device 4 and the vacuum pump 6. Preferably, P 0 It is preferably 0.1 times the vacuum degree of the selected vacuum pump. A filter 63 is also provided between the cyclone dust collector 62 and the vacuum pump 6 to filter impurities and prevent the impurities from entering the vacuum pump 6 and causing blockage.

[0082] In the several embodiments provided in this application, it should be understood that the disclosed systems, devices and methods can be implemented in other ways. The device embodiments described above are merely schematic. For example, the division of the units is only a logical function division. There may be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. Inspired by the above-mentioned ideal embodiments of the present invention and through the above-mentioned description, relevant staff can make various changes and modifications without departing from the technical idea of ​​the present invention. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A precise and stable feeding method for negative pressure dense phase pneumatic conveying, characterized in that: Obtain the deviation between the average powder conveying flow rate and the target flow rate within the sampling time period. Coarsely adjust the opening degree of the bin outlet through the adjustment mechanism to adjust the powder flow rate. At the same time, loosen the air flow control device to adjust the loosening air flow rate at the bin outlet, so as to achieve accurate and stable discharging of the bin. The specific steps are as follows: Step A: The pressure control module (71) opens the balance air solenoid valve (13) and the air shut-off valve (14), adds materials to the bin until the target filling amount is reached, and stops feeding. Step B: Adjust the delivery air volume to the target air volume Q 0 The powder flow control module (72) controls the operation of the regulating mechanism to slowly increase the outlet diameter of the silo; Real-time measurement of powder conveying flow G s (t) , the powder flow control module (72) calculates and sets the segmented collection time τ Average powder mass flow rate within ; ； ； in G 0 Delivering flow rate to powder targets, G s (t) It is the powder conveying flow rate; a is the powder conveying flow deviation, is the sequence number of the time period, the first time period is recorded as , the second time period is recorded as , and so on; When a > 5%, the adjustment mechanism continuously increases the opening degree of the bin outlet until 2% < a ≤ 5%. When 2% < a ≤ 5%, the powder flow control module (72) sends a signal, and the adjustment mechanism maintains the current opening degree of the bin outlet. Step C: Adjust the loosening air flow control device to increase the loosening air flow rate. When |a| ≤ 2%, the powder flow control module (72) sends a signal, and the loosening air flow control device keeps the loosening air flowing at the current flow rate. When -5% ≤ a < -2%, the powder flow control module (72) sends a signal, and the loosening air flow control device reduces the loosening air flow rate until |a| ≤ 2%. When a < -5%, close the loosening air flow control device. If there is still a < -5%, the powder flow control module (72) sends a signal, and the adjustment mechanism reduces the opening degree of the bin outlet until |a| ≤ 2%.

2. The accurate and stable feeding method for negative pressure dense phase pneumatic conveying according to claim 1, wherein Monitoring of air pressure at the top of the silo P 1. Through the formula: ΔP 1 =P a -P 1 >P 0 , calculate the pressure difference between the silo and the outside air pressure ΔP 1 , where P a is atmospheric pressure, P 0 To set the maximum allowable pressure difference; If the above formula holds, the pressure control module (71) controls the balance air solenoid valve (13) to increase the opening degree to adjust the relative balance of the air pressure between the bin and the outside, and ensure smooth feeding of the bin.

3. The accurate and stable feeding method for negative pressure dense phase pneumatic conveying according to claim 2, wherein Monitoring of air pressure at the bottom of the silo P 2 , when the balance air solenoid valve (13) is opened to 100%, the pressure difference ΔP 1 Still greater than P 0 ,and P 1 ≈ P 2 , it is determined that the material level in the silo is too low, and the pressure control module (71) sends a signal to control the air shut-off valve (14) to open and supply material into the silo.

4. The accurate and stable feeding method for negative pressure dense phase pneumatic conveying according to claim 1, wherein The loosening air volume is 10% - 20% of the designed target air supply volume.

5. The accurate and stable feeding method for negative pressure dense phase pneumatic conveying according to claim 1, wherein Powder calculation average mass flow rate segment collection time τ The acquisition time is 2s to 10s, and the acquisition frequency is 5Hz to 500Hz.

6. A precise and stable feeding system for negative pressure dense phase pneumatic conveying, characterized in that: Applied to execute the accurate and stable feeding method according to any one of claims 1 - 5, the accurate and stable feeding system includes: A sending bin (1), which is divided into a silo section (15) and a hopper section (16), and an outlet (11) is provided at the bottom of the hopper section (16). An adjustment mechanism, whose movable end is adapted to slide to adjust the opening degree of the outlet (11). A plurality of loosening air flow control devices, which have a double-layer loosening air distribution plate (32), and the air outlet of the double-layer loosening air distribution plate (32) faces the outlet (11). A powder flow meter device (4) for measuring the mass flow of the material discharged from the discharge port (11) G s ; A powder flow control module (72), and the adjustment mechanism, the loosening air flow control device and the powder flow meter device (4) are all electrically connected to the powder flow control module (72). A breather valve (12) and a balance air solenoid valve (13), which are used to adjust the pressure at the upper part of the silo section (15). Two pressure sensors (8) are respectively arranged at the upper and lower parts of the silo section (15) to measure the air pressure at the corresponding positions. P 1 and P 2 ; A pressure control module (71), and the breather valve (12), the balance air solenoid valve (13), the air shut-off valve (14) and the pressure sensor (8) are all electrically connected to the pressure control module (71).

7. The precise and stable feeding system for negative pressure dense phase pneumatic conveying according to claim 6, characterized in that: The adjusting mechanism comprises an adjusting member (21) and a servo electric cylinder (22); the adjusting member (21) is inserted into the inner side of the material discharge port (11); and the servo electric cylinder (22) is transmission-connected to the adjusting member (21) via a screw rod; The servo electric cylinder (22) is electrically connected to the powder flow control module (72) and is used to adjust the height of the adjustment member (21) to adjust the opening of the discharge port (11).

8. The precise and stable feeding system for negative pressure dense phase pneumatic conveying according to claim 6, characterized in that: The loosening air flow control device further comprises a loosening air chamber (31) and a loosening air solenoid valve (33); the loosening air chamber (31) is arranged on the outer wall of the bucket section (16); the loosening air chamber (31) is connected to the double-layer loosening air distribution plate (32); The loosening air solenoid valve (33) is in communication with the loosening air chamber (31), and the loosening air solenoid valve (33) is electrically connected to the powder flow control module (72) for adjusting the loosening air flow rate.

9. The precise and stable feeding system for negative pressure dense phase pneumatic conveying according to claim 6, characterized in that: The loose air distribution height range H1 of the double-layer loose air distribution plate (32) is not less than 65% of the height H2 of the bucket section (16).

10. The precise and stable feeding system for negative pressure dense phase pneumatic conveying according to claim 6, characterized in that: The bottom of the discharge port (11) is connected to an acceleration chamber (5), one side of the acceleration chamber (5) is provided with a conveying air solenoid valve (51), and the conveying air solenoid valve (51) is electrically connected to a powder flow control module (72) for adjusting the conveying air volume; The discharge end of the acceleration chamber (5) is connected to a vacuum pump (6), and the powder flow meter device (4) is installed between the acceleration chamber (5) and the vacuum pump (6); A separation material collecting tank (61) and a cyclone dust collector (62) are sequentially arranged between the powder flow meter device (4) and the vacuum pump (6).

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