A method for sampling and measuring the electrostatic charge of particles

Abstract

This invention discloses a method for sampling and measuring the electrostatic charge of particles, belonging to the field of particle electrostatic charge sampling and measurement technology. It addresses the problems in existing technologies where sampling and measurement are performed in separate steps, and the sampling operation can cause changes in the electrostatic charge of the particle, affecting the accuracy of the measurement. The method includes: activating the preheating function of the charge meter; turning on the negative pressure suction device and checking the overall airtightness of the sampling and measurement system; activating the charge acquisition function of the charge meter; bringing the sample inlet of the sampling tube close to the particle to be measured; under the negative pressure suction, the particle is drawn into the particle cavity through the sampling tube; the particle transfers its charge to the charge meter through contact charging and induction charging within the sampling tube, contact plate, and particle cavity; and the charge meter measures and calculates the charge parameters of the particle. This invention can be used for particle electrostatic charge sampling and measurement.

Description

Technical Field

[0001] This invention belongs to the field of particle electrostatic charge sampling and measurement technology, and particularly relates to a method for sampling and measuring particle electrostatic charge. Background Technology

[0002] Currently, the commonly used methods for determining the electrostatic charge of particles usually involve two steps: sampling and measurement.

[0003] However, due to the unstable nature of electrostatic charge, charge changes are easily generated during the sampling process. In particular, when metal instruments (e.g., sampling spoons) are used for sampling, the contact between the metal instruments and the particles can cause charge dissipation, thus affecting the accuracy of the final measurement. Summary of the Invention

[0004] In view of the above analysis, the present invention aims to provide a sampling and measurement method for particle static charge, so as to solve the problem that in the prior art, sampling and measurement are performed in separate steps, and the sampling operation will cause changes in the static charge of the particle to be measured, which will affect the accuracy of the measurement.

[0005] The objective of this invention is mainly achieved through the following technical solutions.

[0006] This invention provides a method for sampling and measuring the electrostatic charge of particles. The sampling and measuring method employs a sampling and measuring system, which includes a sampling tube, a contact plate, a connecting terminal, a particle cavity, a charge meter, and a negative pressure suction device. The contact plate is electrically connected to the particle cavity, the sampling tube's outlet end is electrically connected to the contact plate and passes through the contact plate to communicate with the particle cavity, one end of the connecting terminal is electrically connected to the particle cavity, the other end of the connecting terminal is electrically connected to the input end of the charge meter, and the negative pressure suction device is connected to the rear end of the particle cavity.

[0007] The sampling and measurement method includes the following steps:

[0008] Step 1: Activate the charge meter's preheating function;

[0009] Step 2: Turn on the negative pressure suction device and check the overall airtightness of the sampling and measurement system to ensure that the particle chamber is under negative pressure.

[0010] Step 3: Activate the charge acquisition function of the charge meter. Bring the sample inlet of the sampling tube close to the particle to be tested. Under the negative pressure attraction, the particle to be tested is drawn into the particle cavity through the sampling tube. The particle to be tested transfers its charge to the charge meter through contact charging and induction charging in the sampling tube, contact plate and particle cavity. The charge meter measures and calculates the charge parameters of the particle to be tested, thus completing the sampling and measurement of the particle's static charge.

[0011] Furthermore, in step 1, the preheating time is 10–15 minutes.

[0012] Furthermore, the percentage of the particle to be tested in the particle cavity is 20-80%.

[0013] Furthermore, step 2, checking the overall airtightness of the sampling and measurement system includes the following steps:

[0014] Step 21: Block the sampling end of the sampling tube;

[0015] Step 22: Observe the pressure gauge reading on the negative pressure suction device. If the pressure gauge reading decreases, it indicates that the overall airtightness of the sampling and measurement system is good. If the pressure gauge reading remains unchanged, it indicates that there is a leak in the sampling and measurement system.

[0016] Furthermore, the charge parameters include particle charge, charge-to-mass ratio, surface charge density, and equivalent current.

[0017] Further, in step 3, the charge parameters are the particle charge quantity and charge-to-mass ratio. The charge parameters of the particle to be tested are measured by the charge meter in the following steps:

[0018] Stop the charge meter's charge acquisition function, read the charge amount, turn off the negative pressure suction device, open the outer cover, take out the particles to be tested from the particle chamber and weigh them to obtain the particle mass, and obtain the charge-to-mass ratio of the particles to be tested.

[0019] Furthermore, in step 3, the charge parameter is the surface charge density, and the surface charge density of the particle to be tested is calculated using the following formula:

[0020]

[0021] In the formula, ρ is the density of the particle to be measured, kg / m³. 3 ;d p σ is particle size, m; q is charge, C; m is particle mass, kg; σ is surface charge density, C / m 2 .

[0022] Furthermore, in step 3, the charge parameter is the equivalent current, and the charge parameter of the particle to be tested is measured by the charge meter in the following steps:

[0023] Record the relationship between the cumulative charge and time;

[0024] The slope of the curve showing the cumulative charge changing with time is obtained, and the equivalent current of the particle is calculated using the following formula:

[0025]

[0026] In the formula, I is the equivalent current, A; q i For the cumulative charge, C; t i For time, s; The average value over time, in seconds. C represents the average charge.

[0027] Furthermore, the sampling tube, contact plate, and particle chamber are made of conductive metal.

[0028] Furthermore, the sampling tube, contact plate, and particle chamber are made of pure copper.

[0029] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects.

[0030] A) The particle electrostatic charge sampling and measurement method provided by this invention is applicable to the online sampling and measurement of particle electrostatic charge parameters (e.g., particle charge, charge-to-mass ratio, surface charge density, and equivalent current). Since the sampling tube is directly connected to the particle cavity, the sampling tube, contact plate, and particle cavity constitute a conductive cavity. By using a negative pressure suction device to keep the particle cavity under negative pressure, the sampling and measurement of the particle to be tested can be carried out simultaneously, avoiding the change in the electrostatic charge of the particle to be tested due to the sampling and measurement being carried out in separate steps. This effectively improves the accuracy of particle electrostatic charge sampling and measurement, providing a new means for the electrostatic measurement of particles in powder industry and chemical industry equipment, and providing a reference for equipment upgrades and improvements.

[0031] B) The particle electrostatic charge sampling and measurement method provided by the present invention, since the sampling tube, contact plate and particle cavity are all conductive materials, can collect the electrostatic charge parameters of the particle to be tested at the instant the particle to be tested contacts the sampling tube, contact plate and particle cavity, with basically no loss of electrostatic charge, thereby effectively improving the accuracy of particle electrostatic charge sampling and measurement.

[0032] In this invention, the above-described technical solutions can be combined with each other to achieve more preferred combinations. Other features and advantages of this invention will be set forth in the following description, and some advantages may become apparent from the description or be learned by practicing the invention. The objects and other advantages of this invention can be realized and obtained through the embodiments described and the accompanying drawings, which are particularly pointed out. Attached Figure Description

[0033] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0034] Figure 1 The flowchart shows the particle electrostatic charge sampling and determination method provided in Embodiment 1 of the present invention.

[0035] Figure 2 This is a schematic diagram of the sampling and measurement system in the particle electrostatic charge sampling and measurement method provided in Embodiment 1 of the present invention;

[0036] Figure 3This is a schematic diagram of the sampling device in the particle electrostatic charge sampling and determination method provided in Embodiment 1 of the present invention;

[0037] Figure 4 This is a schematic diagram of the sampling tube structure in the particle electrostatic charge sampling and determination method provided in Embodiment 1 of the present invention;

[0038] Figure 5 This is a schematic diagram of the particle cavity structure in the particle electrostatic charge sampling and measurement method provided in Embodiment 1 of the present invention.

[0039] Figure label:

[0040] 1-Sampling device; 101-Sampling tube; 1011-Reduced diameter section; 1012-Constant diameter section; 1013-Expanded diameter section; 1014-Elastic convex area; 102-Outer cover; 103-Contact piece; 104-Connecting terminal; 105-Filter screen; 106-Particle chamber; 1061-Cavity guide groove; 107-Outer shell; 2-Charge meter; 3-Negative pressure suction device. Detailed Implementation

[0041] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which constitute a part of the present invention and are used together with the embodiments of the present invention to illustrate the principles of the present invention, but are not intended to limit the scope of the present invention.

[0042] Example 1

[0043] This embodiment provides a method for sampling and determining the electrostatic charge of particles. See [link to relevant documentation]. Figure 1 The sampling and measurement method employs a sampling and measurement system with the following structure:

[0044] For this sampling and measurement system, see [link / reference]. Figures 2 to 3 The system includes a sampling device 1, a charge meter 2, and a negative pressure suction device 3. The sampling device 1 includes a sampling tube 101 made of conductive material, a contact piece 103, a connecting terminal 104, and a particle chamber 106. The front end of the particle chamber 106 is open. The contact piece 103 covers the opening at the front end of the particle chamber 106 and is electrically connected to it. The sampling tube 101's outlet end is electrically connected to the contact piece 103 and passes through it to communicate with the particle chamber 106. One end of the connecting terminal 104 is electrically connected to the particle chamber 106, and the other end is electrically connected to the input end of the charge meter 2. The negative pressure suction device 3 is connected to the rear end of the particle chamber 106 via a flexible tube. It should be noted that the end of the particle chamber 106 with the sampling tube 101 is defined as the front end, and the end of the particle chamber 106 corresponding to the head is defined as the rear end.

[0045] The sampling and measurement method includes the following steps:

[0046] Step 1: Start the preheating function of the charge meter, and the preheating time is 10-15 minutes;

[0047] Step 2: Turn on the negative pressure suction device and check the overall airtightness of the sampling and measurement system to ensure that the particle chamber is under negative pressure.

[0048] Step 3: Activate the charge acquisition function of the charge meter, bring the sample inlet of the sampling tube close to the particle to be tested, and the particle to be tested is drawn into the particle cavity through the sampling tube under the negative pressure attraction. The particle to be tested transfers the charge on the particle to the charge meter through contact charging and induction charging in the sampling tube, contact plate and particle cavity. The charge meter measures and calculates the charge parameters of the particle to be tested. The charge parameters mainly include particle charge, charge-to-mass ratio, surface charge density and equivalent current, thus completing the sampling and measurement of the static charge of the particle.

[0049] Compared with the prior art, the particle electrostatic charge sampling and measurement method provided in this embodiment is applicable to the online sampling and measurement of particle electrostatic charge parameters (e.g., particle charge, charge-to-mass ratio, surface charge density, and equivalent current). Since the sampling tube 101 is directly connected to the particle cavity 106, the sampling tube 101, the contact plate 103, and the particle cavity 106 constitute a conductive cavity. The negative pressure suction device 3 keeps the particle cavity 106 in a negative pressure state, which enables the simultaneous sampling and measurement of the particle to be tested. This avoids the change in the electrostatic charge of the particle to be tested due to the sampling and measurement being performed in separate steps, thereby effectively improving the accuracy of particle electrostatic charge sampling and measurement. This provides a new means for the electrostatic measurement of particles in powder industry and chemical industry equipment, and provides a reference for equipment upgrades and improvements.

[0050] Furthermore, since the sampling tube 101, contact plate 103, and particle cavity 106 are all made of conductive materials, the electrostatic charge parameters of the particle to be tested can be collected the instant the particle comes into contact with the sampling tube 101, contact plate 103, and particle cavity 106, with virtually no loss of electrostatic charge, thereby effectively improving the accuracy of particle electrostatic charge sampling and measurement.

[0051] To ensure measurement accuracy, for example, the percentage of the particle to be measured in the particle cavity is 20% to 80%.

[0052] For example, step 2 above, checking the overall airtightness of the sampling and measurement system includes the following steps:

[0053] Step 21: Block the sampling end of the sampling tube;

[0054] Step 22: Observe the pressure gauge reading on the negative pressure suction device. If the pressure gauge reading decreases, it indicates that the overall airtightness of the sampling and measurement system is good. If the pressure gauge reading remains unchanged, it indicates that there is a leak in the sampling and measurement system.

[0055] Specifically, in step 3 above, the charge parameters include particle charge, charge-to-mass ratio, and surface charge density. The charge parameters of the particle to be tested are measured by the charge meter in the following steps:

[0056] Stop the charge meter's charge acquisition function, read the charge quantity q, C, turn off the negative pressure suction device, open the outer cover, take out the particle to be tested from the particle chamber and weigh it to obtain the particle mass m, kg, and the charge-to-mass ratio q / m of the particle to be tested can be obtained.

[0057] Calculate the surface charge density σ, C / m of the particles. 2 The following formula is used:

[0058]

[0059] Where ρ is the density of the particle to be measured, kg / m³ 3 d p Let be the particle size, in meters (m).

[0060] In step 3 above, the charge parameters include the equivalent current. The charge parameters of the particle to be tested are measured by the charge meter in the following steps:

[0061] Record the cumulative charge q i With time t i The changing relationship;

[0062] The slope of the curve of cumulative charge changing with time is obtained, and the equivalent current I, A of the particle is calculated using the following formula:

[0063]

[0064] in, The average value over time, in seconds. C represents the average charge.

[0065] To ensure the stability of the overall structure, the above-mentioned sampling and measurement system also includes a housing 107 made of conductive material and an outer cover 102 made of insulating material. The front end of the housing 107 is open, and the outer cover 102 is placed over the opening of the housing 107 and is fixedly connected to the housing 107 by threads or other detachable means. When connecting, airtightness must be ensured. After connection, the contact piece 103 should be tightly attached to the particle chamber 106 and electrically conductive. A through hole is opened on the outer cover 102. The sampling tube 101 passes through the through hole and the contact piece 103 in sequence and communicates with the particle chamber 106. The contact piece 103 is fixed inside the outer cover 102. The rear end of the housing 107 is connected to the negative pressure suction device 3.

[0066] During the sampling and measurement process, in order to reduce the shaking of the sampling tube 101, the above-mentioned through hole is matched with the sampling tube 101. That is to say, the diameter of the through hole is equal to the outer diameter of the sampling tube 101, there is no gap between the sampling tube 101 and the through hole, and the sampling tube 101 can achieve a fixed connection with the through hole after passing through the through hole.

[0067] It should be noted that, in order to facilitate the connection of the negative pressure suction device 3, the rear end of the outer shell 107 is connected to the negative pressure suction device 3. However, in actual applications, the purpose of the negative pressure suction device 3 is to create a negative pressure state in the particle chamber 106. Therefore, the rear end of the particle chamber 106 is open, so that the particle chamber 106 is connected to the shell, thereby creating a negative pressure state in the particle chamber 106.

[0068] In order to prevent the particles to be tested from clogging the negative pressure suction device 3, the above sampling and measurement system also includes a filter screen 105. The filter screen 105 is covered at the opening at the rear end of the particle chamber 106 and is fixedly connected to the rear end of the particle chamber 106 by welding or other means. The mesh size of the filter screen 105 is smaller than the particle size of the particles to be tested, so that the particles to be tested can be confined within the particle chamber 106, thereby preventing the particles to be tested from clogging the negative pressure suction device 3.

[0069] Specifically, the structure of the connecting terminal 104 is a nested structure, including a connecting post, an insulating layer and a grounding layer arranged sequentially from the inside to the outside. The grounding layer is insulated from the connecting post and the particle cavity 106. The connecting post is electrically connected to the charge meter 2 through a connecting wire.

[0070] Specifically, the structure of the connecting line includes, from the inside out, a signal transmission line, an insulation layer, and a signal shielding mesh, which are sequentially nested. The signal shielding mesh is grounded and can effectively shield signal interference, further improving the accuracy of particle electrostatic charge sampling and measurement.

[0071] Understandably, in order to provide a reference potential, the grounding terminal of the charge meter 2 is grounded through the housing 107, and the grounding layer of the connecting terminal 104 is grounded through the housing 107.

[0072] Considering that the particle cavity 106 is suspended inside the outer shell 107, displacement of the particle cavity 106 is inevitable as the usage time increases. In order to ensure the installation stability between the particle cavity 106 and the outer shell 107, the sampling and measurement system also includes an insulating support. The particle cavity 106 is mounted inside the outer shell 107 through the insulating support.

[0073] To improve the sampling performance of sampling tube 101, for the structure of sampling tube 101, please refer to... Figure 4Specifically, it includes a narrowing section 1011, a constant-diameter section 1012, and an expanding section 1013 connected sequentially along the flow direction of the particles to be tested. The narrowing section 1011 accelerates the flow velocity of the particles to be tested and enhances their attraction, making it suitable for attracting larger particles under negative pressure when the negative pressure suction remains constant. The constant-diameter section 1012 stabilizes the flow of the particles to be tested and appropriately increases the contact time and probability between the particles and the constant-diameter section 1012, thereby improving charge conduction between them. The expanding section 1013 facilitates the smooth entry of the particles to be tested from the sampling tube 101 into the particle cavity 106.

[0074] For example, the ratio of the length to the diameter of the sampling tube 101 (i.e., the length-to-diameter ratio) is 10 to 20, the length of the sampling tube 101 is 10 to 20 cm, and the length ratio of the reduced diameter section 1011, the constant diameter section 1012 and the expanded diameter section 1013 is 1 to 1.5: 7.5 to 9: 1 to 1.5.

[0075] In order to further increase the contact time and contact probability between the test particles and the constant diameter section 1012, a spiral tube guide groove is opened on the inner wall of the expanded diameter section 1013. The spiral tube guide groove can generate a spiral flow of test particles, which can further improve the contact time and contact probability between the test particles and the sampling tube 101, thereby further improving the charge conduction between the test particles and the sampling tube 101.

[0076] It is worth noting that, due to the design of the reduced-diameter section 1011, the diameter of the feed end of the reduced-diameter section 1011 is larger than the diameter of the discharge end of the reduced-diameter section 1011 (i.e., the constant-diameter section 1012). During sampling, the constant-diameter section 1012 of the sampling tube 101 may become clogged. To reduce the occurrence of clogging in the constant-diameter section 1012, at least one elastic convex region 1014 is provided on the side wall of the constant-diameter section 1012. The inner wall of the elastic convex region 1014 is concave. The outer wall of 1014 is elastically convex. Once the constant diameter section 1012 becomes blocked, the elastically convex area 1014 can be pressed from the outer wall of the constant diameter section 1012, causing the elastically convex area 1014 to deform into the constant diameter section 1012. Then, the elastically convex area 1014 is released, and it pops outward and generates a certain vibration. Through the vibration, the particles to be tested at the blockage location of the constant diameter section 1012 are loosened and moved, thereby solving the problem of blockage in the constant diameter section 1012.

[0077] To improve the contact time and probability between the test particle and the particle cavity 106, a spiral-shaped cavity guide groove 1061 is also formed on the inner wall of the particle cavity 106. (See [reference]) Figure 5The spiral flow channel 1061 can generate a spiral flow of particles to be tested, which further increases the contact time and contact probability between the particles to be tested and the sampling tube 101, thereby further improving the charge conduction between the particles to be tested and the sampling tube 101.

[0078] It is worth noting that the cavity guide channel 1061 may cause the test particles to remain in the cavity guide channel 1061 and be unable to be poured out of the particle cavity 106. To solve the above problem, the cavity guide channel 1061 includes an inclined wall and a vertical wall arranged sequentially from the front end to the rear end of the particle cavity 106. The inclined wall is arranged radially relative to the particle cavity 106, and the vertical wall is arranged radially along the particle cavity 106. In this way, on the one hand, the arrangement of the guide channel can prolong the contact time between the test particles and the particle cavity 106 and increase the contact area between the test particles and the particle cavity 106. On the other hand, when the test particles are poured out of the particle cavity 106, the inclined wall can guide the test particles so that they can be poured out of the particle cavity 106 smoothly.

[0079] For example, the contact piece 103, filter 105 and particle chamber 106 are made of conductive metal, such as pure copper; the outer shell 107 is made of conductive metal, such as stainless steel; the outer cover 102 is made of insulating material, such as nylon; and the sampling tube 101 is made of conductive metal (e.g., pure copper) and covered with insulating material (e.g., insulating rubber).

[0080] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for sampling and determining the electrostatic charge of particles, characterized in that, The sampling and measurement method employs a sampling and measurement system, which includes a sampling tube, a contact plate, a connecting terminal, a particle chamber, a charge meter, and a negative pressure suction device. The contact plate is electrically connected to the particle chamber, the sampling tube's outlet end is electrically connected to the contact plate and passes through the contact plate to communicate with the particle chamber, one end of the connecting terminal is electrically connected to the particle chamber, the other end of the connecting terminal is electrically connected to the input end of the charge meter, and the negative pressure suction device is connected to the rear end of the particle chamber. The sampling and measurement method includes the following steps: Step 1: Activate the charge meter's preheating function; Step 2: Turn on the negative pressure suction device and check the overall airtightness of the sampling and measurement system to ensure that the particle chamber is under negative pressure. Step 3: Activate the charge acquisition function of the charge meter, bring the sample inlet of the sampling tube close to the particle to be tested, and the particle to be tested is drawn into the particle cavity through the sampling tube under the negative pressure attraction. The particle to be tested transfers the charge on the particle to the charge meter through contact charging and induction charging in the sampling tube, contact plate and particle cavity. The charge meter measures and calculates the charge parameters of the particle to be tested, and completes the sampling and measurement of the static charge of the particle. The charge parameters include particle charge, charge-to-mass ratio, surface charge density, and equivalent current; In step 3, the charge parameter is the equivalent current, and the charge parameter of the particle to be tested is measured by the charge meter in the following steps: Record the relationship between the cumulative charge and time; The slope of the curve showing the cumulative charge changing with time is obtained, and the equivalent current of the particle is calculated using the following formula: In the formula, I is the equivalent current, in A; qi is the cumulative charge, C; ti is the time, s; The average value over time, in seconds. C represents the average charge.

2. The method for sampling and determining the electrostatic charge of particles according to claim 1, characterized in that, In step 1, the preheating time is 10-15 minutes.

3. The method for sampling and determining the electrostatic charge of particles according to claim 1, characterized in that, The percentage of the volume of the particle cavity occupied by the particle to be tested is 20-80%.

4. The method for sampling and determining the electrostatic charge of particles according to claim 1, characterized in that, Step 2, checking the overall airtightness of the sampling and measurement system, includes the following steps: Step 21: Block the sampling end of the sampling tube; Step 22: Observe the pressure gauge reading on the negative pressure suction device. If the pressure gauge reading decreases, it indicates that the overall airtightness of the sampling and measurement system is good. If the pressure gauge reading remains unchanged, it indicates that there is a leak in the sampling and measurement system.

5. The method for sampling and determining the electrostatic charge of particles according to claim 1, characterized in that, In step 3, the charge parameters are the particle charge quantity and charge-to-mass ratio. The charge meter measures the charge parameters of the particle to be tested, including the following steps: Stop the charge meter's charge acquisition function, read the charge amount, turn off the negative pressure suction device, open the outer cover, take out the particles to be tested from the particle chamber and weigh them to obtain the particle mass, and obtain the charge-to-mass ratio of the particles to be tested.

6. The method for sampling and determining the electrostatic charge of particles according to claim 5, characterized in that, In step 3, the charge parameter is the surface charge density, and the surface charge density of the particle to be tested is calculated using the following formula: In the formula, ρ The density of the particles to be measured is kg / m³. 3 ; d p Particle size, in meters (m); q Let C be the amount of charge. m The mass of the particles is in kg. σ Surface charge density, C / m 2 .

7. The method for sampling and determining the electrostatic charge of particles according to any one of claims 1 to 6, characterized in that, The sampling tube, contact plate, and particle cavity are made of conductive metal.

8. The method for sampling and determining the electrostatic charge of particles according to claim 7, characterized in that, The sampling tube, contact plate, and particle chamber are made of pure copper.

Images