A method and device for measuring the suspension velocity of powder

Abstract

The present invention provides a method and device for measuring the suspension velocity of powder. Air is introduced into the lower end of a conical cylinder, and the powder to be measured is conveyed to the upper end. The powder particles move in the conical cylinder under the combined action of their own gravity, air buoyancy, and drag force. During this period, powder measurement sites at different heights in the conical cylinder are used to monitor in real time and online whether there is powder passing by in the plane where they are located. For two adjacent powder measurement sites, if the measurement site located below does not detect powder, while the measurement site located above detects powder passing by, then the wind speed at the plane of the lower measurement site is the suspension velocity of this powder. Compared with the prior art, the method and device provided by the present invention have a wide range of applications and relatively high accuracy. Secondly, the device is simple and the steps are concise, and the distribution and location interval of the powder in the conical cylinder can be obtained quickly, improving the measurement efficiency of the suspension velocity of powdery materials.

Description

Technical Field

[0001] The present invention belongs to the field of measurement of powder characteristic parameters, and particularly relates to a method and device for measuring the suspension velocity of powder. Background Art

[0002] The suspension velocity of powder refers to the velocity of the fluid when the powder is in a stable suspension state in the fluid. The suspension velocity is an important characteristic parameter of powder particles. Measuring the suspension velocity of powder particles is very important for designing a pneumatic conveying system and improving the process effect of pneumatic conveying equipment. However, in engineering practice, the powder has a small particle size and a wide particle size distribution, which brings great difficulties to the measurement of the suspension velocity of powder materials.

[0003] In one prior art, the suspension velocity of the material is measured by adjusting the air volume of the fan so that the tested material just suspends and stays at the half-height position of the transparent test cylinder, and then the anemometer is used to read the wind speed at this position, so as to obtain the suspension velocity of the material. The disadvantage is that it is only suitable for measuring the suspension velocity of materials with a single particle size or larger particle size; in another prior art, based on the light scattering method, the stable state of the suspended powder is judged, and the agglomerate size information of the suspended powder particles is obtained to accurately and effectively measure the suspension velocity of powders with a wide particle size distribution. However, this method is based on an optical method, the system is relatively complex, the steps are relatively cumbersome, and the requirements for the measurement environment are relatively high.

[0004] In summary, the prior art is only applicable to materials with a single particle size or larger particle size. When facing powders with a small particle size and a wide particle size distribution, the measurement accuracy is relatively low, and the measurement technology for the suspension velocity of powders with a wide particle size distribution has high environmental requirements and is relatively complex and cumbersome. Summary of the Invention

[0005] In view of the above technical problems, the present invention provides a method and device for measuring the suspension velocity of powder. The method has a wide application range and high accuracy, and the device is simple and the steps are concise, which can be applicable to the measurement of the suspension velocity of powder.

[0006] In the present invention, air is introduced into the lower end of the conical cylinder, and the powder to be tested is conveyed to the upper end. The powder particles move in the conical cylinder under the combined action of their own gravity, air buoyancy and drag. During this period, the powder measurement sites at different heights in the conical cylinder monitor in real time whether there is powder passing by in the plane where they are located. For two adjacent powder measurement sites, if the measurement site located below does not detect powder, while the measurement site located above detects powder passing by, then the wind speed at the plane where the lower measurement site is located is the suspension velocity of the powder. Compared with the prior art, the method and device provided by the present invention have a wide application range and relatively high accuracy. Secondly, the device is simple and the steps are concise, and the distribution and the interval of the powder in the conical cylinder can be obtained quickly, improving the measurement efficiency of the suspension velocity of powdery materials.

[0007] The present invention achieves the above technical objectives through the following technical means:

[0008] A method for measuring the suspension velocity of powder, comprising the following steps:

[0009] Step S1: Continuously introduce air from the lower end of a conical cylinder with the small end facing downwards, and the air flow velocity in the conical cylinder decreases with the increase in height;

[0010] Step S2: Convey a stream of powder to be measured from the upper end of the conical cylinder. The powder particles in the conical cylinder are subject to their own gravity F g , buoyancy F b of air, and drag force F d . When F g > F b + F d , the powder particles descend. When F g < F b + F d , the powder particles ascend. When F g = F b + F d , the powder particles are suspended;

[0011] Step S3: Denote the number of powder measurement sites along the height direction in the conical cylinder as M. Let the i-th measurement site from the top to the bottom of the conical cylinder be denoted as H i , and the value range of i is 1 to M;

[0012] Step S4: Monitor each powder measurement site. According to the height passed by the powder to be measured, judge the air flow rate. When no powder is detected passing by at H1, it is judged that the air flow rate is too large. When powder is detected passing by at H M , it is judged that the air flow rate is too small. When the air flow rate is too small or too large, cut off the air supply, empty the remaining powder in the conical cylinder, adjust the air input flow rate, and then convey a stream of powder to be measured from the upper end of the conical cylinder again. Monitor in real time and online whether there is powder passing by the plane where the powder measurement sites are located at different heights in the conical cylinder. For two adjacent powder measurement sites, if no powder is detected at the lower powder measurement site while powder is detected passing by at the upper powder measurement site, then the wind speed at the plane of the lower powder measurement site is the suspension velocity of the powder. Denote the current air flow rate as Q, and combine with the cross-sectional area A of the plane where the lower powder measurement site is located to calculate the air flow velocity v0 = Q / A at this plane, that is, the suspension velocity of the powder particles.

[0013] In the above solution, the calculation of the suspension velocity of the powder particles in step S4 specifically includes the following steps:

[0014] When the powder measurement site at H1 never detects the passing of the powder to be measured, it indicates that the powder particles in the conical cylinder reach the suspended state or are carried out of the conical cylinder by air before descending to H1. That is, the air flow rate introduced in step S1 is too large, causing the powder to be measured to be suspended in advance or form a pneumatic conveying and escape from the conical cylinder. Then, cut off the air supply, empty the remaining powder in the conical cylinder, reduce the input air flow rate, and convey a new portion of the powder to be measured from the upper end of the conical cylinder again until the powder measurement site at H i does not detect the passing of the powder to be measured, where 2 ≤ i ≤ M, and H i-1 If the powder measurement site detects the passing of powder, record the current air flow rate as Q, and combine it with the cross-sectional area A i of the plane where the powder measurement site of the conical cylinder is located i , and calculate the air flow velocity v0 of this plane as v0 = Q / A i , that is, the suspension velocity v0 of the powder particles;

[0015] When the powder measurement site at H M detects the passing of powder, it indicates that some of the powder particles in the conical cylinder have descended to the plane where H M is located. That is, the air flow rate introduced in step S1 is too small to suspend the powder to be measured in the conical cylinder. Then, cut off the air supply, empty the remaining powder in the conical cylinder, increase the input air flow rate, and convey a new portion of the powder to be measured from the upper end of the conical cylinder again until the powder measurement site at H i does not detect the passing of the powder to be measured, where 2 ≤ i ≤ M, and H i-1 If the powder measurement site detects the passing of powder, record the current air flow rate as Q, and combine it with the cross-sectional area A i of the plane where the powder measurement site of the conical cylinder is located i , and calculate the air flow velocity v0 of this plane as v0 = Q / A i , that is, the suspension velocity v0 of the powder particles.

[0016] In the above solution, the method for the powder measurement site to determine whether there is passing powder includes one or a combination of methods such as powder concentration measurement, powder mass flow measurement, and powder particle number measurement.

[0017] In the above solution, the distance from the first measurement site H1 to the upper end of the conical cylinder is ΔH, and ΔH ≥ 10 cm.

[0018] In the above solution, the number of powder measurement sites at the same height in the conical cylinder is N, and N ≥ 1.

[0019] In the above solution, the number of powder measurement sites at different heights in the conical cylinder is M, and M ≥ 2.

[0020] An apparatus for implementing the method of measuring the suspension velocity of powders, comprising a powder suspension system, a feedback control system, an air supply system, a feeding system, and a dust removal system;

[0021] The powder suspension system includes a conical cylinder, a tee, a discharge pipe, an electric valve, a cover plate, a feed pipe, and a discharge pipe; both ends of the straight pipe section of the tee are respectively connected to the lower end of the conical cylinder and the discharge pipe, an electric valve is installed on the discharge pipe, the lower end of the conical cylinder is a small opening, a cover plate is installed at the upper end of the conical cylinder, the cover plate is respectively connected to the feed pipe and the discharge pipe, and a plurality of equally spaced measurement ports are provided on the wall of the conical cylinder;

[0022] The feedback control system includes a powder measurement sensor, a data acquisition card, a computer, and a controller. One end of the powder measurement sensor is connected to the data acquisition card, and the other end enters the conical cylinder through the measurement port. The data acquisition card is connected to the computer, and the computer is connected to the controller;

[0023] The air supply system includes an air inlet pipe, a fan, an electric three-way valve, and a flow meter. The fan, the electric three-way valve, and the flow meter are sequentially arranged on the air inlet pipe, and the air inlet pipe is connected to the branch pipe section of the tee;

[0024] The feeding system is connected to the feed pipe;

[0025] The dust removal system is connected to the discharge pipe;

[0026] The computer is connected to the flow meter, and the flow meter is used to collect the current air flow rate Q;

[0027] The controller is connected to the fan, the electric three-way valve, the electric valve, and the feeding system.

[0028] In the above solution, the powder measurement sensor is a powder concentration sensor, a powder mass flow sensor, or a powder counting sensor.

[0029] In the above solution, the dust removal system includes a cyclone dust collector; the inlet of the cyclone dust collector is connected to the discharge pipe.

[0030] In the above solution, the feeding system includes a screw feeder and a motor; the discharge port of the screw feeder is connected to the feed pipe; the controller is connected to the motor.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] The present invention has a wide range of applications, high accuracy, a simple device, and simple steps, and can be applied to the measurement of the suspension velocity of powders.

[0033] The present invention can set powder measurement sites at different heights and different positions at the same height of the conical cylinder respectively, so as to quickly and accurately obtain the distribution and location interval of the powder in the conical cylinder, accelerate the adjustment speed of the air flow rate, and improve the measurement efficiency of the suspension speed.

[0034] In the present invention, air is introduced at the lower end of the conical cylinder, and the powder to be measured is conveyed at the upper end. Compared with the prior art in which both the powder and air are introduced from the lower end of the conical cylinder, it can avoid the disadvantage that large particles are still in a static state while small particles have been fluidized or escaped, and improve the accuracy of measuring the suspension speed of the powder.

[0035] A three-way pipe is provided between the air supply system and the powder suspension system in the present invention. Air enters through the branch pipe section of the three-way pipe. The two ends of the straight pipe section of the three-way pipe are respectively connected to the small end of the conical cylinder and the discharge pipe. By controlling the opening and closing of the electric valve on the discharge pipe, the powder in the conical cylinder is emptied. Compared with the prior art method of discharging the remaining powder from the top of the conical cylinder by increasing the air volume, it is more energy-saving, environmentally friendly, convenient and effective. Description of the Drawings

[0036] Figure 1 is a schematic structural diagram of a device for measuring the suspension speed of powder according to an embodiment of the present invention.

[0037] Figure 2 is a schematic flowchart of a method for measuring the suspension speed of powder according to an embodiment of the present invention.

[0038] In the figure: 1 - motor; 2 - screw feeder; 3 - cover plate; 4 - feed pipe; 5 - discharge pipe; 6 - cyclone dust collector; 7 - conical cylinder; 8 - acquisition card; 9 - powder measurement sensor; 10 - measurement port; 11 - three-way pipe; 12 - discharge pipe; 13 - electric valve; 14 - flow meter; 15 - electric three-way valve; 16 - air inlet pipe; 17 - fan; 18 - controller; 19 - computer. Detailed Embodiments

[0039] The embodiments of the present invention will be described in detail below. The examples of the embodiments are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present invention and should not be construed as limiting the present invention.

[0040] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "front", "rear", "left", "right", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, "a plurality" means two or more, unless otherwise specifically defined.

[0041] In the present invention, unless otherwise clearly specified and limited, the terms "mounted", "connected", "connected to", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] A method for measuring the suspension velocity of powder, comprising the following steps:

[0043] Step S1: Continuously introduce a certain flow rate of air from the lower end of the conical cylinder 7 with the small end facing downwards, so that the air flow velocity in the conical cylinder 7 slowly decreases with the increase of height;

[0044] Step S2: Convey a stream of powder to be measured from the upper end of the conical cylinder 7. The powder particles in the conical cylinder 7 are subjected to the combined action of their own gravity F g , the buoyancy F b of the air and the drag force F d . When F g > F b + F d , the powder particles descend. When F g < F b + F d , the powder particles rise. When F g = F b + F d , the powder particles are suspended;

[0045] Step S3: Denote the number of powder measurement sites along the height direction inside the conical cylinder as M, and denote the i-th measurement site from the top to the bottom of the conical cylinder as H i , where the value range of i is 1 to M;

[0046] Step S4: Monitor each powder measurement site, and judge the air flow rate according to the height passed by the powder to be measured. When no powder is detected passing by at H1, it is judged that the air flow rate is too large. When powder is detected passing by at H M , it is judged that the air flow rate is too small. When the input air flow rate is too small or too large, cut off the air input, empty the remaining powder in the conical cylinder, adjust the air input flow rate, and then convey a new portion of the powder to be measured from the upper end of the conical cylinder again. Monitor in real time and online whether there is powder passing by the plane where the powder measurement sites are located at different heights inside the conical cylinder. For two adjacent powder measurement sites, if the powder measurement site at the lower position does not detect powder passing by, while the powder measurement site at the upper position detects powder passing by, then the wind speed at the plane where the lower powder measurement site is located is the suspension velocity of the powder. Denote the current air flow rate as Q, and combine with the cross-sectional area A of the plane where the lower powder measurement site is located to calculate the air flow velocity v0 = Q / A at this plane, that is, the suspension velocity of the powder particles.

[0047] Preferably, the calculation of the suspension velocity of the powder particles in step S4 specifically includes the following steps:

[0048] When the powder measurement site at H1 never detects the powder to be measured passing by, it indicates that the powder particles in the conical cylinder (7) reach the suspension state or are carried out of the conical cylinder (7) by air before descending to H1, that is, the air flow rate input in step S1 is too large, causing the powder to be measured to be suspended in advance or form pneumatic conveying and escape from the conical cylinder (7). Then cut off the air input, empty the remaining powder in the conical cylinder (7), reduce the air input flow rate, and convey a new portion of the powder to be measured from the upper end of the conical cylinder (7) again until H i (2 ≤ i ≤ M) the powder measurement site does not detect the powder to be measured, and H i-1 (2 ≤ i ≤ M) the powder measurement site detects powder passing by, then denote the current air flow rate as Q, and combine with the cross-sectional area A of the plane where the powder measurement site at H i of the conical cylinder (7) is located i , calculate the air flow velocity v0 = Q / A at this plane i , that is, the suspension velocity v0 of the powder particles;

[0049] When the powder measurement site at H M detects powder passing by, it indicates that some powder particles in the conical cylinder (7) have descended to H MThe plane where it is located, that is, the air flow rate introduced in step S1 is too small to suspend the powder to be measured in the conical cylinder (7). Then, cut off the air supply, empty the remaining powder in the conical cylinder (7), increase the input air flow rate, and convey a stream of the powder to be measured from the upper end of the conical cylinder (7) again until no powder to be measured is detected at the powder measurement site at H i (2 ≤ i ≤ M), and H i-1 (2 ≤ i ≤ M), if powder passing by is detected at the powder measurement site, record the current air flow rate as Q, and combine it with the cross-sectional area A i of the plane where the powder measurement site is located in the conical cylinder (7) i , and calculate the air flow velocity v0 of this plane as v0 = Q / A i , that is, the suspension velocity v0 of the powder particles

[0050] Preferably, the method for determining whether there is powder passing by at the powder measurement site includes one or a combination of more of the methods of powder concentration measurement, powder mass flow measurement, and powder number measurement

[0051] Preferably, the distance from the first measurement site H1 to the upper end of the conical cylinder 7 is ΔH, and ΔH ≥ 10 cm

[0052] Preferably, the number of powder measurement sites at the same height in the conical cylinder 7 is N, and N ≥ 1

[0053] The number of powder measurement sites at different heights in the conical cylinder 7 is M, and M ≥ 2

[0054] An apparatus for implementing the method for measuring the suspension velocity of powder includes a powder suspension system, a feedback control system, an air supply system, a feeding system, and a dust removal system

[0055] As Figure 1 shown, the powder suspension system includes a conical cylinder 7, a tee 11, a discharge pipe 12, an electric valve 13, a cover plate 3, a feed pipe 4, and a discharge pipe 5. Both ends of the straight pipe section of the tee 11 are respectively connected to the lower end of the conical cylinder 7 and the discharge pipe 12. An electric valve 13 is installed on the discharge pipe 12. The lower end of the conical cylinder 7 is a small opening. A cover plate 3 is installed at the upper end of the conical cylinder 7. The cover plate 3 is respectively connected to the feed pipe 4 and the discharge pipe 5. Multiple equally spaced measurement ports 10 are provided on the barrel wall of the conical cylinder 7

[0056] The feedback control system includes a powder measurement sensor 9, a data acquisition card 8, a computer 19, and a controller 18. One end of the powder measurement sensor 9 is connected to the data acquisition card 8, and the other end enters the conical cylinder 7 through the measurement port 10. The data acquisition card 8 is connected to the computer 19, and the computer 19 is connected to the controller 18

[0057] The air supply system includes an air inlet pipe 16, a fan 17, an electric three-way valve 15, and a flow meter 14. The fan 17, the electric three-way valve 15, and the flow meter 14 are sequentially arranged on the air inlet pipe 16, and the air inlet pipe 16 is connected to a branch pipe section of a three-way pipe 11;

[0058] The feeding system is connected to a feed pipe 4;

[0059] The dust removal system is connected to a discharge pipe 5;

[0060] The computer 19 is connected to the flow meter 14, and the flow meter 14 is used to collect the current air flow rate Q;

[0061] The controller 18 is connected to the fan 17, the electric three-way valve 15, an electric valve 13, and the feeding system.

[0062] The feeding system includes a screw feeder 2 and a motor 1; the discharge opening of the screw feeder 2 is connected to the feed pipe 4; the controller 18 is connected to the motor 1.

[0063] Preferably, the dust removal system includes a cyclone dust collector 6; the inlet of the cyclone dust collector 6 is connected to the discharge pipe 5.

[0064] Preferably, the powder measurement sensor 9 is a powder concentration sensor, a powder mass flow sensor, or a powder counting sensor.

[0065] Preferably, the measurement port 10 is in a sealed state during the measurement process.

[0066] Combined with Figure 2 , the specific implementation working process:

[0067] The computer 19 sends an instruction to the controller 18 to control the closing of the electric valve 13, the opening of the fan 17, and the adjustment of the opening degree of the electric three-way valve 15. After the air entering the conical cylinder 7 is stable, the controller 18 controls the start of the motor 1, and the motor 1 drives the screw feeder 2 to convey a stream of powder to be measured from the upper part of the conical cylinder 7 and then stops running; the powder measurement sensor 9 in the conical cylinder 7 measures the passing situation of the powder at the measured height in real time online, and the acquisition card 8 collects the measured signals and transmits them to the computer 19;

[0068] Denote the powder measurement sites at different heights of the conical cylinder as H i , with a cross-sectional area of A i , first input the air Q, and then through the air and the input powder, let i = 1;

[0069] When the powder measurement sensor 9 at H1 never detects the passing of powder, it indicates that the powder particles in the conical cylinder 7 have not dropped to H1 yet but have already reached the suspended state or been carried out of the conical cylinder 7 by air, that is, the air flow rate introduced is too large and the air volume needs to be reduced. The computer 19 issues an instruction to close the blower 17 through the controller 18, open the electric valve 13. After emptying the powder in the conical cylinder 7, control to close the electric valve 13, start the blower 17, reduce the opening degree of the electric three-way valve 15, and start the motor 1 again to convey a stream of powder to be measured until the powder measurement sensor 9 at H i (2 ≤ i ≤ M) does not detect the powder to be measured, and the powder measurement sensor 9 at H i-1 (2 ≤ i ≤ M) detects the passing of powder, then obtain the current air flow rate as Q according to the flow meter 14, and combine with the cross-sectional area A of the plane where the powder measurement site of the conical cylinder 7H i is located i , and calculate the air flow velocity v0 of this plane as v0 = Q / A i , that is, the suspension velocity v0 of the powder particles.

[0070] When the powder measurement sensor 9 at H M detects the passing of powder, it indicates that some powder particles in the conical cylinder 7 have dropped to H M , that is, the air flow rate introduced is too small and the air volume needs to be increased. The computer 19 issues an instruction to close the blower 17 through the controller 18, open the electric valve 13. After emptying the powder in the conical cylinder 7, control to close the electric valve 13, start the blower 17, increase the opening degree of the electric three-way valve 15, and start the motor 1 again to convey a stream of powder to be measured; until the powder measurement sensor 9 at H i (2 ≤ i ≤ M) does not detect the powder to be measured, and the powder measurement sensor 9 at H i-1 (2 ≤ i ≤ M) detects the passing of powder, then obtain the current air flow rate as Q according to the flow meter 14, and combine with the cross-sectional area A of the plane where the powder measurement site of the conical cylinder 7H i is located i , and calculate the air flow velocity v0 of this plane as v0 = Q / A i , that is, the suspension velocity v0 of the powder particles. The present invention can respectively set powder measurement sites at different heights and different positions at the same height in the conical cylinder 7 to quickly and accurately obtain the powder distribution and the interval in the conical cylinder, speed up the adjustment speed of the introduced air flow rate, and improve the measurement efficiency of the suspension velocity.

[0071] The present invention respectively introduces air at the lower end of the conical cylinder 7 and conveys the powder to be measured at the upper end. Compared with the prior art where both the powder and air are introduced from the lower end of the conical cylinder, it can avoid the drawback that large particles are still in a static state while small particles have already fluidized or escaped, and improve the accuracy of the powder suspension velocity measurement.

[0072] A tee 11 is provided between the air supply system and the powder suspension system of the present invention. Air enters through the branch section of the tee 11. The two ends of the straight pipe section of the tee 11 are respectively connected to the small end of the conical cylinder and the discharge pipe 12. By controlling the opening and closing of the electric valve 13 on the discharge pipe 12, the powder in the conical cylinder 7 is emptied. Compared with the prior art method of discharging the remaining powder from the top of the conical cylinder by increasing the air volume, it is more energy-saving, environmentally friendly, convenient and effective.

[0073] It should be understood that although this specification is described according to each embodiment, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0074] The series of detailed descriptions listed above are only specific descriptions of the feasible embodiments of the present invention, and they are not intended to limit the protection scope of the present invention. Any equivalent embodiments or changes made without departing from the technical spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for measuring the suspension velocity of powder, characterized in that, It includes the following steps: Step S1: Continuously introduce air from the lower end of the conical cylinder (7) with the small end facing downwards, and the air flow velocity in the conical cylinder (7) decreases with the increase in height; Step S2: Convey a powder sample to be measured from the upper end of the conical cylinder (7). The powder particles in the conical cylinder (7) are subject to their own gravity F g , buoyancy F b of air, and drag force F d . When F g > F b + F d , the powder particles descend. When F g < F b + F d , the powder particles ascend. When F g = F b + F d , the powder particles are suspended; Step S3: Denote the number of powder measurement sites in the conical cylinder (7) along the height direction as M, and denote the i-th measurement site from the top to the bottom of the conical cylinder (7) as H i , where the value range of i is 1 to M; Step S4: Monitor each powder measurement site, and judge the air flow rate according to the height at which the powder to be measured passes by. When no powder is detected passing by at H1, it is judged that the air flow rate is too large. When powder is detected passing by at H M it is judged that the air flow rate is too small. When the air flow rate is too small or too large, the air supply is cut off, the remaining powder in the conical cylinder (7) is emptied, the air input flow rate is adjusted, and a new stream of powder to be measured is conveyed from the upper end of the conical cylinder (7). Monitor in real time and online whether there is powder passing by the plane where the powder measurement sites are located at different heights in the conical cylinder (7). For two adjacent powder measurement sites, if no powder is detected at the lower powder measurement site while powder is detected passing by at the upper powder measurement site, the wind speed at the plane where the lower powder measurement site is located is the suspension velocity of the powder. Record the current air flow rate as Q, and combine it with the cross-sectional area A of the plane where the lower powder measurement site is located to calculate the air flow velocity v0 = Q / A at this plane, that is, the suspension velocity of the powder particles.

2. The method for measuring the suspension velocity of powder according to claim 1, wherein The calculation of the suspension velocity of the powder particles in step S4 specifically includes the following steps: When the powder measurement site at H1 has never detected the passing of the powder to be measured, it indicates that the powder particles in the conical cylinder (7) have not dropped to H1, that is, the air flow rate introduced is too large. Then, cut off the air supply, empty the remaining powder in the conical cylinder (7), reduce the air flow rate input, and convey a stream of the powder to be measured from the upper end of the conical cylinder (7) again until there is no detection of the powder to be measured at the powder measurement site at H i where 2 ≤ i ≤ M, and at the powder measurement site at H i-1 there is detection of the passing of the powder, then record the current air flow rate as Q, and combine it with the cross-sectional area A i of the plane where the powder measurement site of the conical cylinder (7) is located i , and calculate the air flow velocity v0 of this plane as v0 = Q / A i , that is, the suspension velocity v0 of the powder particles; When there is powder passing by detected at the powder measurement site at H M it indicates that some powder particles in the conical cylinder (7) have dropped to the plane where H M is located, that is, the air flow rate introduced is on the low side. Then, cut off the air supply, empty the remaining powder in the conical cylinder (7), increase the input air flow rate, and convey a new portion of powder to be measured from the upper end of the conical cylinder (7) again until there is no powder to be measured detected at the powder measurement site at H i where 2 ≤ i ≤ M, and when there is powder passing by detected at the powder measurement site at H i-1 record the current air flow rate as Q, and combine it with the cross-sectional area A i of the plane where the powder measurement site at H i is located, and calculate the air flow velocity v0 = Q / A i at this plane, which is the suspension velocity v0 of the powder particles.

3. A method for measuring the suspension velocity of powder according to claim 1, characterized in that, The method for determining whether there is powder passing by the powder measurement site includes one or a combination of more of the powder concentration measurement, powder mass flow measurement, and powder number measurement methods.

4. A method for measuring the suspension velocity of powder according to claim 1, characterized in that, The distance from the first measurement site H1 to the upper end of the conical cylinder (7) is ΔH, and ΔH≥10 cm.

5. A method for measuring the suspension velocity of powder according to claim 1, characterized in that, The number of powder measurement sites at the same height in the conical cylinder (7) is N, and N≥1.

6. A method for measuring the suspension velocity of powder according to claim 1, characterized in that The number of powder measurement sites at different heights in the conical cylinder (7) is M, and M≥2.

7. An apparatus for implementing the method of measuring the suspension velocity of powder according to any one of claims 1-6, characterized in that, It includes a powder suspension system, a feedback control system, an air supply system, a feeding system, and a dust removal system; The powder suspension system includes a conical cylinder (7), a tee (11), a discharge pipe (12), an electric valve (13), a cover plate (3), a feed pipe (4), and a discharge pipe (5); both ends of the straight pipe section of the tee (11) are respectively connected to the lower end of the conical cylinder (7) and the discharge pipe (12), an electric valve (13) is installed on the discharge pipe (12), the lower end of the conical cylinder (7) is a small end, a cover plate (3) is installed at the upper end of the conical cylinder (7), the cover plate (3) is respectively connected to the feed pipe (4) and the discharge pipe (5), and a plurality of equally spaced measurement ports (10) are provided on the cylinder wall of the conical cylinder (7); The feedback control system includes a powder measurement sensor (9), a data acquisition card (8), a computer (19), and a controller (18). One end of the powder measurement sensor (9) is connected to the data acquisition card (8), and the other end enters the conical cylinder (7) through the measurement port (10). The data acquisition card (8) is connected to the computer (19), and the computer (19) is connected to the controller (18); The air supply system includes an air inlet pipe (16), a fan (17), an electric three-way valve (15), and a flowmeter (14). The fan (17), the electric three-way valve (15), and the flowmeter (14) are sequentially arranged on the air inlet pipe (16), and the air inlet pipe (16) is connected to the branch pipe section of the tee (11); The feeding system is connected to the feed pipe (4); The dust removal system is connected to the discharge pipe (5); The computer (19) is connected to the flowmeter (14), and the flowmeter (14) is used to collect the current air flow Q; The controller (18) is connected to the fan (17), the electric three-way valve (15), the electric valve (13), and the feeding system.

8. A device for measuring the suspension velocity of powder according to claim 7, characterized in that The powder measurement sensor (9) is a powder concentration sensor, a powder mass flow sensor, or a powder counting sensor.

9. The device for measuring the suspension velocity of powder according to claim 7, characterized in that, The dust removal system includes a cyclone dust collector (6); the inlet of the cyclone dust collector (6) is connected to the discharge pipe (5).

10. The device for measuring the suspension velocity of powder according to claim 7, characterized in that, The feeding system includes a screw feeder (2) and a motor (1); the discharge port of the screw feeder (2) is connected to the feed pipe (4); the controller (18) is connected to the motor (1).

Images