CN111551797A - Online electrostatic charge quantity measuring device suitable for energetic material - Google Patents
Online electrostatic charge quantity measuring device suitable for energetic material Download PDFInfo
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- CN111551797A CN111551797A CN202010302702.0A CN202010302702A CN111551797A CN 111551797 A CN111551797 A CN 111551797A CN 202010302702 A CN202010302702 A CN 202010302702A CN 111551797 A CN111551797 A CN 111551797A
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Abstract
The invention discloses an on-line electrostatic charge quantity measuring device suitable for energetic materials, which comprises a stock bin, a micro-current sensor and a data acquisition processor, wherein the stock bin, the micro-current sensor and the data acquisition processor are electrically connected in sequence; the invention can realize continuous on-line measurement, directly measure the electrostatic electrification current and the total electrostatic charge quantity of the powder in the storage bin, ensure that the maximum spark discharge energy of the measuring device is far less than the minimum ignition energy of the powder, has high safety, has the maximum error less than 6 percent compared with the measurement result of a potentiometer method, has accurate and reliable measurement result, convenient installation of the measuring device and wide application range.
Description
Technical Field
The invention relates to the technical field of energetic material electrostatic charge measurement, in particular to an online electrostatic charge amount measuring device suitable for energetic materials.
Background
Static electricity is one of the main factors that trigger the combustion and explosion of energetic materials. Real-time monitoring of the amount of electrostatic charge is an important means for preventing electrostatic disasters. At present, the method of using a faraday cylinder and a potentiometer is mainly adopted for measuring the electrostatic charge quantity, the principle is that a faraday cylinder is formed by an inner concentric metal cylinder and an outer concentric metal cylinder which are insulated from each other, the faraday cylinder has a fixed capacitance C, the outer cylinder is grounded, the inner cylinder is insulated from the outer cylinder, after a sampled energetic material is injected into the inner cylinder of the faraday cylinder, an electrostatic potential relative to the outer cylinder is generated in the inner cylinder, the electrostatic potential U is measured by the potentiometer, and the electrostatic charge quantity of the energetic material can be calculated according to Q & ltCU & gt.
The potentiometer method has many limitations in the actual measurement process, which are mainly shown in the following steps:
(1) the sample is required to be manually sampled and injected into the Faraday cylinder for measurement, and the electrostatic charge quantity of the sample is influenced in the manual sampling process, so that the measurement result is inaccurate. In order to eliminate the influence caused by artificial sampling, researchers research various online sampling measurement modes, such as a method of arranging a movable automatic material taking device at a feed inlet in the process of performing "alignment tests with different charges from polymeric granules in situ" by m.glor, b.maurer. The method is characterized in that a special sample sampling spoon and a special sampling shovel are designed for measuring the electrostatic charge quantity of the energetic material of the fluidized bed by sharmene Ali and the like, and Li wenguo, Jin taidong and the like develop an online Faraday cylinder method.
Although students research different online sampling modes, the method is to measure the quantity of electrostatic charges of a small quantity of energetic material samples on an energetic material conveying pipeline or at the feeding moment of a storage bin, and then calculate the total quantity of electrostatic charges of all energetic materials in the storage bin according to the charge-to-mass ratio of the samples, rather than directly monitoring the total quantity of electrostatic charges of the energetic materials in the storage bin.
(2) The potentiometric method has a greater safety risk. For some energetic materials with small electrostatic ignition energy (even less than 0.1mJ), the Faraday inner cylinder is groundedLarge resistance, input impedance of potentiometer higher than 1014Omega, when the charged energetic material enters the Faraday inner cylinder, the Faraday inner cylinder generates a higher voltage, and electrostatic discharge is possible to occur. If the mass of the energetic material conveyed into the Faraday cup through the pipeline is 1kg, the maximum possible quantity of generated electrostatic charge can reach 10-6C/kg, the capacitance C of the Faraday cup is about 100pf generally, and at the moment, the electrostatic voltage of the inner cylinder and the outer cylinder of the Faraday cup reaches to
That is, such a high voltage may cause spark discharge between the inner and outer cylinders of the Faraday cup, and the discharge energy will reach
This discharge energy makes it possible to ignite a charge with an electrostatic ignition energy of less than 5 mJ.
Based on the above, the present invention provides an online electrostatic charge measurement device suitable for energetic materials, so as to solve the above mentioned problems.
Disclosure of Invention
The present invention is directed to an online electrostatic charge measurement device for energetic materials, so as to solve the problems mentioned in the background art.
In order to achieve the purpose, the invention provides the following technical scheme: the utility model provides an online electrostatic charge amount measuring device suitable for energetic material, includes feed bin, little current sensor and data acquisition treater, electric connection in proper order between feed bin, little current sensor and the data acquisition treater, be equipped with in the feed bin and contain can the powder, the feed bin top is equipped with the feed inlet, the feed bin is detached the totally closed design in all the other positions outside the feed inlet, the feed bin overcoat has the shielding layer, contactless between shielding layer and the feed bin, shielding layer ground connection, little current sensor includes low input impedance little current preamplifier, falls circuit, AD converting circuit and data transmission circuit of making an uproar, the data acquisition treater includes data receiving circuit, integrating circuit, data storage circuit and data display element.
Preferably, the feeding bin, the low-input-impedance micro-current preamplifier, the noise reduction circuit, the A/D conversion circuit, the data transmission circuit, the data receiving circuit, the integrating circuit, the data storage circuit and the data display unit are electrically connected in sequence.
Preferably, the data acquisition processor receives data transmitted by the micro-current sensor, and performs micro-current integration, data storage, data display and time control.
Preferably, the storage bin and the shielding layer are both cylindrical, and the storage bin and the shielding layer are both made of metal materials.
Preferably, an insulating support body is arranged in the shielding layer and supports the storage bin.
Preferably, the micro-current sensor and the data acquisition processor are both grounded.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention can conveniently realize continuous on-line measurement, directly measure the electrostatic electrification current and the total electrostatic charge quantity of the powder in the storage bin, and avoid the complicated material sampling process.
2. The maximum spark discharge energy of the measuring device is far less than the minimum ignition energy of the powder, so that the combustion and explosion accidents possibly caused by the spark discharge of the measuring device are avoided, and the safety is high.
3. Compared with the measuring result of a potentiometer method, the maximum error is less than 6%, and the measuring result is accurate and credible.
4. The measuring device is convenient to install and wide in application range, and not only can be used for monitoring the electrostatic charge quantity of a powder storage bin, but also can be used for monitoring the electrostatic charge quantity of other types of materials such as liquid and the like.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic view of a measuring device according to the present invention;
FIG. 2 is a schematic diagram of the measurement of the present invention;
FIG. 3 is a graph comparing the amount of electrostatic charge measured by the inductive micro-current method and the potentiometric method according to the present invention;
FIG. 4 is a graph showing the induced current when the powder flow rate is 0.6 m/s;
FIG. 5 is a graph showing the charge amount at a flow rate of 0.6 m/s;
FIG. 6 is a graph showing the induced current at a powder flow rate of 0.9m/s according to the present invention;
FIG. 7 is a graph showing the charge amount at a flow rate of 0.9m/s for the powder of the present invention;
FIG. 8 is a graph showing the induced current at a powder flow rate of 1.2m/s according to the present invention;
FIG. 9 is a graph showing the charge amount at a powder flow rate of 1.2m/s according to the present invention;
FIG. 10 is a graph comparing the charge amount curves of powders at different flow rates according to the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1-2, the present invention provides a technical solution of an online electrostatic charge measurement device for energetic materials: comprises a storage bin 3, a micro-current sensor 5 and a data acquisition processor, wherein the storage bin 3, the micro-current sensor 5 and the data acquisition processor 6 are electrically connected in sequence, the equivalent input impedance of the micro-current sensor 5 is less than 1000 omega, the measurement range is 1nA-1mA, energy-containing powder 4 is filled in the storage bin 3, the top of the storage bin 3 is provided with a feeding hole 1, the rest parts of the storage bin 3 except the feeding hole 1 are designed in a totally-closed way, the power line generated by the electrostatic charge of the powder is ensured not to leak, a shielding layer 2 is sleeved outside the storage bin 3, the shielding layer 2 is not in contact with the storage bin 3, the external electrostatic interference is shielded, the shielding layer 2 is grounded, the micro-current sensor 5 comprises a low-input impedance micro-current preamplifier 51, the amplification of the equivalent resistance to the ground and the nA-mA micro-current is reduced, a noise reduction circuit 52 is used for realizing, the A/D conversion circuit 53 realizes the digital conversion function of the amplified analog current signal, the data transmission circuit 54 realizes the digital signal coding and transmission functions, and the data acquisition processor 6 comprises a data receiving circuit 61, an integrating circuit 62, a data storage circuit 63 and a data display unit 64.
Wherein, the feeding bin 3, the low input impedance micro-current preamplifier 51, the noise reduction circuit 52, the A/D conversion circuit 53, the data transmission circuit 54, the data receiving circuit 61, the integrating circuit 62, the data storage circuit 63 and the data display unit 64 are electrically connected in sequence.
The data acquisition processor 6 receives the data transmitted by the micro-current sensor 5, and performs micro-current integration, data storage, data display and time control.
The storage bin 3 and the shielding layer 2 are both cylindrical, and the storage bin 3 and the shielding layer 2 are both made of metal materials; an insulating support body 7 is arranged in the shielding layer 2, and the insulating support body 7 supports the storage bin 3; both the micro-current sensor 5 and the data acquisition processor 6 are grounded.
Principle of obtaining electrostatic charge amount by induction micro-current integration: the powder is electrified due to friction and collision in the transmission process, when the powder carrying the electrostatic charge quantity q in the time t enters the stock bin, the equivalent opposite charges-q are induced on the inner wall of the stock bin according to the Gaussian theorem, the equivalent same charges q are generated on the outer wall of the stock bin, if the outer wall is grounded, the charges flow into the ground through a leakage line to form induced leakage current, and the electrostatic charge quantity entering the stock bin powder in the time t can be obtained by measuring the leakage current and integrating the leakage current according to the time, namely. When t takes different values, a curve of the change in the amount of charge with time can be obtained.
Principle of reducing the spark discharge energy of the stock bin: supposing the maximum of the powderSmall ignition energy EminIt was 0.1 mJ. The maximum energy of the stock bin for generating spark discharge is
(wherein Q is the electrostatic charge amount of the powder in the storage bin, and U is the ground potential of the storage bin). To ensure safety, E must be less than Emin0.1 mJ. When the maximum mass of the powder in the storage bin is 10kg, the maximum charge-to-mass ratio
When the maximum charge quantity Q in the storage bin is 10kg 10-6C/kg＝10-5C. In order to ensure that E is less than 0.1mJ, the maximum potential of the storage bin must be ensured
The maximum potential of the silo is determined by the equivalent ground resistance R of the silo and the electrostatic induction current I, i.e., U ═ IR. When the maximum charging speed v of the storage bin is 1kg/s, the electrostatic induction electrification current of the storage bin
In order to ensure that U is less than 20V, the equivalent ground resistance of the storage bin
From the above, when the equivalent ground resistance of the storage bin is smaller than 2 x 107Omega, the maximum potential of the bin is less than 20V, and the maximum spark discharge energy of the bin is less than 0.1 mJ.
The specific working principle is as follows:
the measuring circuit adopts a micro-current sensor and is connected between the stock bin and the ground, the equivalent ground resistance of the stock bin is mainly determined by the input impedance of the micro-current sensor, and the input impedance is 1000 omega, so that the equivalent ground resistance of the stock bin is less than 1000 omega, the maximum potential and the maximum discharge energy which can be reached by the stock bin are far less than the minimum ignition energy of the powder, the electrostatic discharge generated by a measuring system can be ensured not to ignite the powder, and the safety is ensured.
Selecting polypropylene powder with the minimum ignition energy of 25mJ as a substitute, controlling the same electrification condition, comparing and measuring the quantity of electrostatic charge by adopting an induction micro-current method and a potentiometer method, wherein the measurement result is shown in figure 3, as can be seen from figure 3, the measurement results of the induction micro-current method and the potentiometer method are basically consistent, the maximum error is not more than 6%, and the charge-to-mass ratio of the materials measured by the two methods is uniformly distributed in the range of 1-3 mu C/kg.
The powder storage bin with the minimum ignition energy smaller than 0.1mJ is continuously monitored by an induction micro-current method, the height h1 of the outer cylinder of the storage bin is 380mm, the diameter d1 is 470mm, the height h2 of the inner cylinder is 300mm, the diameter d2 is 310mm, and C is 70 pf. The powder is continuously injected into the storage bin at three different flow rates of 0.6m/s, 0.9m/s and 1.2m/s, the mass of the materials injected into the storage bin is 10kg, the measured electrostatic leakage current curve and the electrostatic charge quantity curve are shown in figures 4-10, and the electrostatic charge polarity of the measured powder is negative as can be seen from figures 4-10; as shown in fig. 4-5, when the powder flow speed is 0.6m/s, the maximum electrostatic charge amount of the storage bin is-5.2, and the charge-to-mass ratio is-0.52; as shown in fig. 6-7, when the powder flow speed is 0.9m/s, the maximum electrostatic charge amount of the storage bin is-8.1, and the charge-to-mass ratio is-0.81; as shown in FIGS. 8-9, when the powder flow rate is 1.2m/s, the maximum electrostatic charge amount of the storage bin is-9.7, and the charge-to-mass ratio is-0.97. As can be seen from fig. 10, the maximum electrostatic charge amount and the charge-mass ratio of the powder both increase with the increase of the powder flow rate, and it can be seen that the electrostatic charge amount of the powder bin can be continuously monitored by using the induction micro-current method.
In the description herein, references to the description of "one embodiment," "an example," "a specific example" or the like are intended to mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above do not necessarily refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The preferred embodiments of the invention disclosed above are intended to be illustrative only. The preferred embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims (6)
1. An online electrostatic charge amount measuring device suitable for energetic materials is characterized in that: including feed bin (3), little current sensor (5) and data acquisition treater, electric connection in proper order between feed bin (3), little current sensor (5) and data acquisition treater (6), be equipped with in feed bin (3) and can powder (4), feed bin (3) top is equipped with feed inlet (1), feed bin (3) are detached feed inlet (1) outer all the other totally closed designs in position, feed bin (3) overcoat has shielding layer (2), contactless between shielding layer (2) and feed bin (3), shielding layer (2) ground connection, little current sensor (5) are including little current preamplifier of low input impedance (51), fall circuit of making an uproar (52), AD converting circuit (53) and data transmission circuit (54), data acquisition treater (6) are including data receiving circuit (61), An integrating circuit (62), a data storage circuit (63), and a data display unit (64).
2. The on-line electrostatic charge amount measuring device suitable for the energetic material according to claim 1, wherein: the feeding bin (3), the low-input-impedance micro-current preamplifier (51), the noise reduction circuit (52), the A/D conversion circuit (53), the data transmission circuit (54), the data receiving circuit (61), the integrating circuit (62), the data storage circuit (63) and the data display unit (64) are electrically connected in sequence.
3. The on-line electrostatic charge amount measuring device suitable for the energetic material according to claim 1, wherein: and the data acquisition processor (6) receives the data transmitted by the micro-current sensor (5), and performs micro-current integration, data storage, data display and time control.
4. The on-line electrostatic charge amount measuring device suitable for the energetic material according to claim 1, wherein: the storage bin (3) and the shielding layer (2) are both cylindrical, and the storage bin (3) and the shielding layer (2) are both made of metal materials.
5. The on-line electrostatic charge amount measuring device suitable for the energetic material according to claim 1, wherein: be equipped with insulating support body (7) in shielding layer (2), insulating support body (7) support feed bin (3).
6. The on-line electrostatic charge amount measuring device suitable for the energetic material according to claim 1, wherein: the micro-current sensor (5) and the data acquisition processor (6) are both grounded.
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