JP4021859B2 - Electric field measuring apparatus and electric field measuring method - Google Patents

Description

  The present invention relates to an electric field measuring apparatus and an electric field measuring method for predicting the electric field strength of the inner wall of a stirring tank whose inner wall is coated with an insulating material.

  In a stirring tank used in the field of chemical industry or the like, static electricity may be generated by the relative movement of the contents in the stirring tank during the stirring process or mixing process. This static electricity is remarkably generated when the content in the agitation tank is a mixture of a low-solubility powder (solid) and a low-conductivity solvent (liquid), and is accumulated in the low-conductivity content. Cause electrostatic charge. Therefore, when the solvent is a flammable liquid with low conductivity, the discharge from the electrostatic level accumulated in the contents becomes the ignition source of the mixed gas of the solvent vapor and air, and the agitation is performed. Risk of fire and explosion of the tank.

  In addition, the inner wall of the steel tank of the stirring tank is coated (covered) with an insulating material such as glass in order to prevent the contents in the stirring tank from adhering or corrosion of the stirring tank. A stirring tank may be used. In such an agitation tank whose inner wall is coated with glass (hereinafter referred to as a GL agitation tank), the GL agitation tank is caused by electrostatic charge generated by agitation and mixing of a powder having a low solubility and a solvent. There is a possibility that dielectric breakdown is caused in the coating layer (glass layer). That is, when the voltage between the coating layers generated by the charges accumulated in the coating layer exceeds the breakdown voltage, dielectric breakdown occurs, and the coating layer has pinholes, chipping, or peeling of the coating material. Destructive phenomena such as damage may occur.

  Therefore, in order to prevent the fire and explosion caused by the electrostatic charge as described above, a technique for measuring the charge amount of the contents such as the powder and the solvent has been proposed (for example, Non-Patent Documents 1 and 2). ).

For example, in Non-Patent Documents 1 and 2, in order to measure the charge amount of the contents in the stirring tank, an electrostatic field measuring device is attached to the upper part of the contents surface in the metal stirring tank to Is described. In this way, by measuring the amount of charge of the contents in the agitation tank, information on the generation of static electricity during the agitation process of the contents in the agitation tank is obtained, and the risk of charging is evaluated. A method for preventing this problem has been studied.
“Research Report on Industrial Safety Research Institute”, RIIS-RR-89, Tsutomu Kodama et al. “Quantification of electrostatic charge and prevention of static electricity by stirring flammable liquids”, Ministry of Labor, Industrial Safety Research Institute, p. 79-93, May 1990 Monthly issue “Research Report on Industrial Safety Research Institute”, RIIS-RR-90, Tsutomu Kodama et al. “Quantification of electrostatic charge and prevention of static charge by stirring and mixing of solid-liquid two-phase system”, Ministry of Labor, Industrial Safety Research Institute, p.89-100 Published in May 1991

  However, in the GL stirring tank, since the coating layer has insulating properties, there is a problem that the coating layer in the GL stirring tank is not uniformly charged due to static electricity generated in the stirring process. In other words, there is a problem that the coating layer is biased in electric charge, and the polarity and charge amount of the coating layer of the GL stirring tank vary greatly depending on the position of the GL stirring tank.

  Therefore, as described in Non-Patent Documents 1 and 2 above, it is impossible to grasp the charge amount and the charge bias in the coating layer only by measuring the electrostatic field intensity at the upper surface of the contents of the stirring tank. In particular, since the dielectric breakdown is likely to occur at a portion where the charge amount in the coating layer of the GL stirring tank is large, detailed knowledge about the bias of charge as described above and the charged state in the GL stirring tank is obtained, and It is important to prevent the occurrence.

  On the other hand, in order to measure the charge amount at each position of the coating layer of the GL stirring tank, an electric field sensor is disposed at a position where knowledge about the charge amount is to be obtained, and the electric field at the position where the electric field sensor is disposed. It is necessary to measure the strength. However, since the coating layer is provided on the inner wall of the GL stirring tank, it is not possible to place an electric field sensor on the coating layer inside the GL stirring tank without contacting the contents in the GL stirring tank. Is possible.

  The present invention has been made to solve the above-described conventional problems, and is an electric field measuring apparatus and an electric field measuring method for obtaining knowledge about charge bias in a coating layer of a stirring tank provided in an actual apparatus. Is to provide.

  As a result of intensive studies in view of the above problems, the present inventors have obtained knowledge about the charge amount distribution on the inner wall of the stirring tank when stirring is performed in the stirring tank provided in the actual apparatus. Using a bench-scale experimental stirrer equipped with a stirring vessel having insulation equivalent to the insulating material covering the inner wall of the stirring vessel, if the amount of charge on the wall surface of the stirring vessel is measured, It has been found that the charge amount can be approximately predicted (hereinafter referred to as prediction), and the present invention has been completed.

  That is, in order to solve the above-mentioned problems, the electric field measurement apparatus of the present invention is equipped with an actual stirrer for predicting the electric field strength of a stirrer whose inner wall is covered with an insulating material. An insulating container formed of a material having an insulating property equivalent to that of the insulating material, a conductive sheet that covers the outer surface of the insulating container, and an electric field sensor. The electric field sensor is provided in a region where the conductive sheet covering the outer surface is partially cut out and the outer surface of the insulating container is exposed.

  According to said structure, the electrically conductive sheet of the insulating container (henceforth agitation container) with which the outer surface was coat | covered with the electrically conductive sheet with which the electric field measurement apparatus was equipped was cut off partially, and an insulating container Since the electric field sensor is provided in the region where the outer surface of the substrate is exposed, the electric field strength of the region can be obtained. Since the electric field measuring apparatus reproduces the actual apparatus equipped with the stirring tank on a bench scale, it is made of an insulating material covering the inner wall of the stirring tank based on the knowledge about the electric field strength obtained by the electric field sensor. It is considered possible to predict the electric field strength on the wall surface (hereinafter referred to as an insulating wall surface), the change in electric field strength with respect to the position of the insulating wall surface of the stirring tank, and the like.

  Therefore, based on the predicted electric field strength, the stirring conditions are controlled so that the electric field strength on the insulating wall surface of the stirring tank of the stirring device for an actual machine, which is difficult to measure, does not exceed the dielectric breakdown electric field strength of the insulating wall surface. Therefore, it is considered that dielectric breakdown can be prevented. Alternatively, the strength of the insulating wall is increased or the insulating wall is repaired with respect to the insulating wall at a specific location that is likely to cause dielectric breakdown because the electric field strength is larger than other positions of the insulating wall of the stirring tank. It is considered that the dielectric breakdown on the insulating wall surface can be prevented by increasing the frequency of the above.

  As described above, by using the electric field measuring apparatus of the present invention, the electric field strength at the insulating wall of the stirring tank predicted based on the actual measurement value by the electric field sensor is evaluated, and the actual apparatus stirring apparatus is inspected and maintained in advance. be able to. Thereby, the dielectric breakdown in the insulation wall surface of the said stirring tank with which the stirring apparatus for actual machines was equipped can be prevented.

  In the electric field measurement apparatus of the present invention, in the electric field measurement apparatus, the insulating container preferably has a geometric shape that is substantially similar to the stirring tank. Thereby, based on the measured value by the said electric field sensor, the electric field strength in the insulation wall surface of a stirring tank can be estimated more correctly.

  Moreover, it is preferable that the electric field measuring apparatus of this invention is used in order to estimate especially the electric field strength of the said stirring tank in the case of stirring an insulating substance in the said stirring tank.

  Moreover, the electric field measurement method of the present invention is an electric field measurement method for predicting the electric field strength of a stirring tank provided in an actual apparatus for stirring to have the inner wall covered with an insulating material, in order to solve the above-described problems. The insulating material exposed by covering the outer surface of an insulating container formed of a material having the same insulating property as the insulating material with a conductive sheet and partially cutting the conductive sheet. It is characterized by measuring the electric field strength of the outer surface of the container.

  According to the above method, the electric field intensity is obtained by providing the electric field sensor on the outer surface of the insulating container of the stirring container provided in the electric field measuring apparatus that reproduces the actual apparatus equipped with the stirring tank on a bench scale. . Therefore, based on the information on the electric field strength obtained by the electric field sensor, the electric field strength on the insulating wall surface of the stirring tank, the dependence of the electric field strength on each position of the insulating wall surface, and the like can be predicted. This makes it possible to predict and evaluate the electric field strength of the insulating wall surface of the stirring tank, which is difficult to measure, so that it is possible to prevent dielectric breakdown in the insulating wall surface of the stirring tank provided in the actual machine stirring device. It will be possible.

  In the electric field measurement method of the present invention, in the electric field measurement method, the insulating container preferably has a geometric shape that is substantially similar to the stirring tank. Thereby, based on the measured value by the said electric field sensor, the electric field strength in the insulating wall surface of a stirring tank can be estimated more correctly.

  The electric field measuring method of the present invention is particularly suitable for predicting the electric field strength of the stirring tank when the content stirred in the stirring tank is an insulating substance.

  As described above, the electric field measurement apparatus of the present invention is such that the outer surface of an insulating container formed of an insulating material is coated with a conductive sheet, and the conductive sheet is partially cut off to form the insulating container. An electric field sensor is provided in a region where the outer surface is exposed.

  Therefore, the electric field measuring device can reproduce the actual stirring device on a bench scale. Therefore, based on the knowledge about the electric field strength obtained by the electric field sensor, the electric field strength on the wall surface of the insulating material covering the inner wall of the actual machine stirring tank, the change in the electric field strength with respect to the position of the insulating wall surface of the actual stirring tank, etc. Can be predicted. In this way, by evaluating the electric field strength of the agitation tank for actual equipment that is expected by the electric field measurement device, inspect and maintain the actual equipment agitation device in advance to prevent dielectric breakdown on the insulating wall surface of the actual equipment agitation device. There is an effect that can be.

  Further, as described above, the electric field measurement method of the present invention uses an experimental stirring vessel in which the outer surface of an insulating container formed of an insulating material is covered with a conductive sheet, and is attached to the experimental stirring vessel. This is a method of measuring the electric field strength of the outer surface of the insulating container exposed by partially cutting the attached conductive sheet.

  Therefore, based on the information on the electric field strength obtained by the electric field sensor, it is possible to predict the electric field strength on the insulating wall surface of the stirring tank for an actual machine, the dependence of the electric field strength on each position of the insulating wall surface, and the like. Based on the predicted electric field strength of the insulation wall of the actual tank, which is difficult to measure, control the stirring conditions in the actual mixer, or repair or reinforce the actual mixer Thus, there is an effect that there is a possibility that the insulation breakdown in the insulating wall surface of the actual agitator can be prevented in advance.

  An embodiment of the present invention will be described below with reference to FIG.

  The electric field measurement apparatus of the present embodiment is a bench-scale agitation apparatus configured to predict the charge amount (electric field strength) of the inner wall surface of the agitation tank provided in the actual apparatus agitation apparatus.

  In the present embodiment, the stirring tank of the actual stirring device has a coating layer which is a glass (insulating material) layer formed by glass lining on the inner wall of a tank made of a conductive material such as steel or stainless steel. A case where the electric field intensity in the coating layer is predicted based on information obtained from the electric field measuring device will be described as an example.

  When the actual machine stirring device includes the GL stirring tank, as shown in FIG. 1, an electric field measuring device for predicting the electric field strength of the inner wall of the GL stirring tank is a glass flask (insulating container) 1a. And a conductive adhesive tape (conductive sheet) 1b having conductivity and adhesiveness, and the outer surface of the flask 1a is covered with the conductive adhesive tape 1b. In other words, the electric field measuring apparatus includes the stirring container 1 formed by covering the outer surface of the flask 1a with the conductive adhesive tape 1b. Specifically, the stirring vessel 1 is formed by adhering the conductive adhesive tape 1b to the outer surface of the flask 1a without any gap.

  Here, the electric field measuring device may be different in size so as to be a simulation device (model) of the actual machine stirring device, but includes an experimental stirring device having the same structure as the actual machine stirring device as much as possible. It is preferable. In other words, it is preferable to design the experimental stirring device so that when the experimental stirring device is scaled up to become an actual stirring device, the stirring operation in the actual stirring device is reproduced by the experimental stirring device. In particular, the electric field measuring device preferably includes a stirring vessel 1 having a shape that can be regarded as geometrically similar to the shape of the GL stirring tank of the actual stirring device. That is, it is preferable that the electric field measuring apparatus includes a stirring vessel 1 formed by covering the outer surface of a flask 1a having a geometric shape with respect to the GL stirring tank with the conductive adhesive tape 1b.

  Further, the material of the flask 1a is preferably the same material as the coating layer of the GL stirring tank, but any material having the same level of insulation as the coating layer may be used. That is, any insulating material that can be regarded as substantially equivalent to the coating layer may be used. Furthermore, the said electrically conductive adhesive tape 1b should just be provided with electroconductivity and adhesiveness and the electroconductivity which can be considered substantially equivalent to the said tank of a GL stirring tank.

  Thereby, the said flask 1a can be regarded as what simulated the coating layer of the said GL stirring tank. Further, the stirring container 1 covered with the conductive adhesive tape 1b can be regarded as a simulation of the electrostatic charge state of the GL stirring tank of the actual stirring device.

  The conductive adhesive tape 1b is a laminated tape obtained by laminating a metal foil on a conductive adhesive obtained by kneading conductive powder and an adhesive resin. Examples of the conductive powder include metal powder such as nickel powder, gold powder, silver powder, copper powder, and metal whisker, and powder of conductive carbon. The adhesive resin includes an adhesive such as an acrylic resin. The resin which has can be mentioned. The metal foil is formed by forming a metal such as aluminum, copper, or iron into a thin film.

  The conductive adhesive tape 1b is commercially available as an electromagnetic wave shield. For example, a single-sided tape for shielding CU7635R using a rolled copper foil or an electrolytic copper foil as a metal foil and a conductive acrylic resin as a conductive adhesive material. , CU7636R, CU7637R, CU7638D (all manufactured by Sony Chemical Co., Ltd.); Ebarrier ETN, ETA, ETC (all trade names, manufactured by Fossei Kasei Co., Ltd., Furukawa Electric Co., Ltd.) using aluminum foil or copper foil as metal foil; Conductive metal foil tape NITOFOIL CT-311E, CT-311EG, CT-315E, AT-511E, AT-5105E (all made by Nitto Denko Corporation) using electrolytic copper foil, rolled copper foil, and aluminum foil as metal foil ) Etc. may be used.

  In the present embodiment, the conductive adhesive tape 1b is used. However, a conductive adhesive containing metal powder is applied to the metal foil, and the metal foil is applied to the outer surface of the flask. May be.

  As shown in FIG. 1, the electric field measuring apparatus includes a stirrer 2 for stirring the contents in the stirring container 1 and a baffle plate for disturbing the flow of the contents in the stirring container 1. Baffle 3, sample upper field sensor 7 for measuring the electric field strength in the vicinity of the liquid level in the stirring vessel 1, and electric field sensor 8 for measuring the electric field strength at the vessel wall of the flask 1 a of the stirring vessel 1. And further. Here, it is preferable to use the stirrer 2 and the baffle 3 that are designed so as to correspond to the stirrer and the baffle provided in the actual apparatus by scaling up.

  The agitator 2 has one end of the agitation shaft attached to the motor 4 so as to rotate about the agitation shaft. The motor 4 is connected to a controller with a torque meter (hereinafter referred to as a controller) 5. The controller 5 can control the number of stirring of the stirrer 2 by arbitrarily adjusting the number of rotations of the motor 4. Further, since the agitator 2 is a conductor, for example, a wire (not shown) is wound in a coil shape so as to contact the agitation shaft portion, and the wire is grounded.

  The sample upper electric field sensor 7 is provided for measuring the electric field strength of air in a region not filled with the contents in the stirring vessel, that is, in a region between the contents and the upper portion of the stirring vessel. Yes.

  Moreover, the stirring container 1 has the sensor attachment part 1c formed by exposing the outer surface of the flask 1a by partially cutting off the conductive adhesive tape 1b attached to the flask 1a. An electric field sensor 8 is attached to the sensor attachment portion 1c. The detection part for detecting the electric field provided in the electric field sensor 8 may be attached so as to contact the flask 1a, or may be attached separately from the flask 1a.

  The sensor mounting portion 1c includes, for example, the bottom of the stirring vessel 1, the lower side of the side of the side of the stirring vessel, the center of the side above the lower side of the side, and the vicinity of the surface of the contents contained in the stirring vessel 1 What is necessary is just to form in the position which is going to acquire the knowledge regarding electric field strength, such as the surface part of content.

  The sensor mounting portion 1c is provided with an electric field sensor 8 for measuring the electric field strength of the flask 1a. Thereby, the electric field strength in each sensor attachment part 1c of the vessel wall of the flask 1a can be measured.

  In order to attach the electric field sensor 8 to the sensor attachment portion 1c, first, the adhesive of the conductive adhesive tape 1b attached to the sensor attachment portion 1c is removed. Subsequently, the electric field sensor 8 is brought into intimate contact with the conductive adhesive tape 1b so that the detection part of the electric field sensor 8 faces the outer surface of the flask 1a at the substantially central part of the sensor mounting part 1c, and the electric field sensor is used with the adhesive tape. Install 8.

  Alternatively, the electric field sensor 8 may be attached by applying a conductive adhesive or a conductive adhesive to the sensor mounting portion 1c from which the adhesive of the conductive adhesive tape 1b has been removed. In this case, attention should be paid so that the adhesive or pressure-sensitive adhesive does not protrude from the portion of the sensor mounting portion 1c that faces the detection portion of the electric field sensor 8.

  The above-described sample upper electric field sensor 7 and electric field sensor 8 (hereinafter collectively referred to as sensors 7 and 8) calibrate the surface potential meter (for example, KSD-109, 0202, 0303 manufactured by Kasuga Electric) for measuring the electric field strength. It is a thing. The measurement values detected by these sensors 7 and 8 are converted by an analog / digital converter (hereinafter referred to as an A / D converter) 9 and input to the computer 6. As a result, the measurement values detected by the sensors 7 and 8 are monitored by the computer 6 in real time.

  In FIG. 1, for convenience of explanation, all the sensors 7 and 8 are connected to the A / D converter 9, but in actuality, each sensor 7 and 8 is a multi-channel A / D. What is necessary is just to set it as the structure connected to each channel of a converter.

  The stirring vessel 1 has a conductive adhesive tape 1b on the outer surface grounded. Therefore, a part of static electricity accumulated in the flask 1a can be leaked via the conductive adhesive tape 1b according to the conductivity of the flask 1a.

  In the electric field measuring apparatus having the above configuration, when predicting the charge amount of the coating layer of the GL stirring tank provided in the actual apparatus, the following operation may be performed. That is, the contents are put in the stirring container 1 of the electric field measuring device, and the motor 5 is rotated by the controller 5 to drive the stirrer 2. Here, it is preferable that the stirring operation performed by the electric field measuring device is set as much as possible as the stirring condition in the actual machine stirring device so that the stirring operation in the actual machine stirring device can be reproduced. For example, the volume ratio of the contents to the volume of the stirring vessel 1 is preferably set to be the same as the volume ratio of the contents to the volume of the GL stirring tank in the actual stirring apparatus. Moreover, it is preferable to set also about the stirring number of the said motor 4 so that it may become the same as the stirring number in an actual machine stirring apparatus.

  When the controller 5 drives the stirrer 2, the stirrer 2 rotates, and the contents in the stirring vessel 1 flow and are stirred. At this time, since the flow of the contents changes when the contents collide with the baffle 3, the contents in the stirring vessel 1 can be made to flow uniformly. In addition, although the structure provided with the baffle 3 as a baffle plate was shown in the stirring container 1 as an electric field measuring apparatus of this Embodiment, the structure which is not equipped with this baffle may be sufficient.

  In addition, the sensors 7 and 8 are operated along with the rotation of the agitator 2, and the measured values detected by the sensors 7 and 8 are monitored by the computer 6 via the A / D converter 9. Generally, in the stirring container 1, when stirring is started by the rotation of the stirrer 2, electric charges are generated due to friction between the contents or between the contents and the stirring container 1. This electric charge is gradually accumulated as static electricity on the inner wall of the flask 1a of the stirring vessel 1, and a part of the electric charge accumulated in the flask 1a is applied to the conductive adhesive tape 1b according to the conductivity of the flask 1a. Leak through. Therefore, as the agitation time elapses, static electricity is accumulated in the agitation container 1 and the amount of charge gradually rises. Becomes a steady state.

  Therefore, the value calculated from the measured value when the charged state of the stirring vessel 1 reaches a steady state is determined as the electric field strength at each position of the flask 1a of the stirring vessel 1.

  In addition, what is necessary is just to calculate the electric field strength in the steady state of the said stirring container 1 based on the measured value after predetermined time passes, for example from the start of stirring. That is, the value calculated based on the measured value may be determined as the electric field strength at each sensor attachment portion 1c on the outer surface of the flask 1a of the stirring vessel 1. Alternatively, a measurement value at a time point when the measurement value detected by the sensors 7 and 8 is hardly observed and the measurement value can be regarded as constant is determined as an electric field strength in each sensor attachment portion 1c of the stirring vessel 1. Also good.

  Here, the conversion of the measured value detected by the sensors 7 and 8 into the electric field intensity may be performed by, for example, a conversion formula obtained using the electric field calibration electrode. Specifically, as shown in FIG. 2B, the electric field calibration electrode includes a grounded ground electrode 10 and a voltage application electrode 11 that is a plate to which a voltage is applied, with a predetermined interval d therebetween. It is fixed by a post 12 (FIG. 2A) so as to face each other. The ground electrode 10 is provided with, for example, a hole 10a for arranging an electric field sensor in the central portion, and a grounded plate and a rectangle larger than the hole 10a of the plate (size of 20 mm × 90 mm). And two plates having a plurality of openings. The ground electrode 10 and the voltage application electrode 11 are plate-like electrodes formed of a conductive material such as SUS.

  In order to derive the conversion formula using the electric field calibration electrode having the above-described configuration, first, a detection unit of an electric field sensor (surface potential meter) is arranged in accordance with the position of the hole 10a, and the electric field sensor is connected to the ground electrode. 10 is brought into close contact with the shallow rectangular portion (the portion exposed from the opening of the plate provided with the hole 10a). Then, the voltage Vap is applied to the voltage application electrode 11, and the indicated value V 'of the electric field sensor is read.

Here, since the distance between the ground electrode 10 and the voltage application electrode 11 is d, the electric field strength E ′ between the two electrodes is theoretically expressed by the equation (1).
E '= Vap / d (1)
Is calculated by On the other hand, since the indication value V ′ of the electric field sensor is in principle proportional to the electric field intensity E ′ of the equation (1), there is an equation (2) between the indication value V ′ and the electric field strength E ′.
d ′ = V ′ / E ′ (2)
Therefore, when the electric field intensity measurement of the electric field measuring device is performed using the electric field sensor, the electric field intensity E at the position of the sensor mounting portion 1c is based on the actual measurement value V and the expression (2). Formula (3)
E = V / d '(3)
It is converted by. Here, in Expression (3), d ′ is a constant determined by Expression (2) using the electric field calibration electrode.

  Based on the electric field strength of the stirring vessel 1 measured in this way, the electric field strength of the wall surface of the GL stirring tank provided in the actual stirring device and the tendency of charging in the GL stirring tank can be predicted. That is, the experimental stirring device is a simulation of an actual stirring device on a bench scale. Therefore, the tendency of the electric field strength in the stirring vessel 1 of the experimental stirring device is considered to have similarity to the tendency of the electric field strength in the GL stirring tank of the actual stirring device. Therefore, the electric field strength in the coating layer of the GL agitation tank provided in the actual apparatus is determined based on the value of the electric field intensity measured by the electric field measurement device and the knowledge about the dependence of the electric field strength on each position of the sensor mounting portion 1c. The correlation between the strength and the position of the coating layer and the electric field strength (hereinafter referred to as electric field strength dependency) can be predicted.

  In addition, the magnitude of the electric field strength of the GL stirring tank and the dependence of the electric field strength can be predicted almost accurately if the stirring container 1 uses the flask 1a having a shape similar to that of the GL stirring tank. However, in order to predict more accurately, it is preferable to use the flask 1a having a geometric shape that is substantially similar to the GL stirred tank. Here, “substantially similar” means that both the GL stirring tank and the flask 1a of the stirring vessel 1 are cylindrical, and the geometric shapes of both are the same or substantially the same. It shall mean having a geometric shape. That is, the stirring container 1 of the electric field measurement device may not be completely similar as long as the geometric shape is the same (substantially the same) as the GL stirring tank of the actual stirring device.

  Thus, if the electric field measuring apparatus is used, the electric field strength in the coating layer of the GL stirring tank, which is difficult to measure with the actual apparatus stirring apparatus, can be predicted. Therefore, by evaluating this predicted electric field strength, the stirring conditions are controlled so that the electric field strength in the coating layer of the GL stirring tank does not exceed the breakdown electric field strength of the coating layer, or It is possible to prevent dielectric breakdown in the coating layer by appropriately strengthening or repairing the coating layer at a specific location where the electric field strength during stirring is greater than that in the location.

Examples of the contents stirred in the stirring vessel 1 include a liquid, a gas-liquid mixture, a liquid-liquid mixture, a solid-liquid mixture, and the like. Among these, in particular, when agitation is performed using an insulating substance as a content, dielectric breakdown tends to occur in the coating layer of the GL agitation tank. Therefore, the electric field measuring device is particularly useful for predicting the electric field strength of the coating layer of the GL stirring tank when the insulating material is stirred as a stirring sample with an actual stirring device. Here, in particular, the insulating substance means a solid and / or liquid whose volume resistivity is independently 1 × 10 ⁹ (Ω · m) or more. That is, the electric field measurement performed using the electric field measuring device is particularly useful when a mixture of a solid and a liquid having high insulation properties is used.

In the present embodiment, the actual apparatus stirring apparatus provided with the GL stirring tank having the glass coating layer has been described as an example. However, the coating layer may be, for example, a thermoplastic resin such as fluororesin or polyethylene, epoxy You may form with thermosetting resins, such as resin, thermosetting polyester, and polyurethane. That is, the coating layer on the inner wall of the stirring tank provided in the actual stirring device is made of glass or the above resin, for example, the resistivity is 1 × 10 ⁹ (Ω · m) or more, particularly 1 × 10 ¹¹ (Ω · m ) In the case where the insulating material is formed as described above, predicting the electric field strength using the electric field measuring apparatus of the present invention is useful for preventing dielectric breakdown of the coating layer.

  Further, the size of the sensor mounting portion 1c provided in the stirring container 1 of the electric field measuring device can be appropriately changed according to the size of the electric field sensor 7 disposed in the sensor mounting portion 1c. Furthermore, the number and position of the sensor attachment portions 1c provided in the stirring vessel 1 can be appropriately set so that the electric field strength at a desired position on the outer surface of the flask 1a can be obtained. Therefore, if the electric field measuring device is used, it is possible to easily estimate the electric field strength in the coating layer of the actual machine stirring tank provided in the actual machine stirring device that is difficult to measure. Thereby, it is considered that the dielectric breakdown of the coating layer can be prevented by a simpler method.

  Hereinafter, embodiments of the present invention will be described in detail with reference to FIGS. The conversion formula for calculating the electric field strength from the measured value was derived as follows.

[Derivation of conversion formula]
As shown in FIGS. 2 (a) and 2 (b), a 250 mm × 300 mm square SUS ground electrode 10 and a voltage application electrode 11 are used, and both electrodes are opposed to each other with an interval of 45 mm. It was fixed with four posts 12 made of (registered trademark) to form an electric field calibration electrode. The ground electrode 10 of the electric field calibration electrode is grounded, and the position of the detection portion of the electric field sensor is aligned in the hole 10a provided in the center of the ground electrode 10 so that the voltage Vap is applied to the voltage application electrode 11. did. Thereafter, the indicated value V ′ measured by the electric field sensor was read, and a conversion formula was derived based on the above-described formulas (2) and (3).

[Example 1]
A conductive adhesive tape (shield single-sided tape CU7636R, manufactured by Sony Chemical Co., Ltd.) was affixed to a 2 L cylindrical glass flask without gaps to obtain a stirring container. In addition, the said conductive adhesive tape laminates | stacks the 30-micrometer-thick conductive acrylic adhesive on 40-micrometer rolled copper foil.

  Next, as shown in FIG. 3 (b), a Faudler-type stirrer 2 is attached to the stirring vessel 1 such that the stirring shaft is positioned at the center of the stirring vessel 1, and the stirring shaft of the stirrer 2 is attached. The baffle 3 was attached so that it might be arrange | positioned between the stirring vessel 1 and the side wall.

  Moreover, as shown in FIG. 3 (a) (b) among the electrically conductive adhesive tapes affixed on the said stirring container 1, the height from the bottom face of the stirring container 1 of the side wall of the stirring container 1 is 3 mm. The conductive adhesive tape at the position ((i) in the figure), the position 70 mm ((ii) to (iv) in the figure), and the position 130 mm ((v) in the figure) is 6 mm × 8 mm square. The flask was exposed by partially cutting out by size, and used as a sensor mounting position. A surface electrometer (KSD-0202, 0303 manufactured by Kasuga Denki) was calibrated and attached to the sensor mounting position for electric fields.

  In addition, as shown in (ii)-(iv) of FIG.3 (b), the three surface electrometers attached in the position of 70 mm in height follow the outer periphery of a stirring container on the basis of the arrangement position of a baffle. Thus, they were arranged at positions ((iii) and (iv)) moved 90 degrees to the left and right and positions ((ii)) moved 180 degrees. This position of 70 mm in height corresponds to a substantially intermediate position between the bottom surface of the stirring vessel and the upper surface of the contents.

On the other hand, polypropylene (volume resistivity: 7.7 × 10 ¹⁴ [Ω · m], specific gravity: 1.12) and n-heptane (conductivity: 6.3 ×) so that the concentration by weight of the powder is 10 wt%. A solid-liquid mixture was prepared by mixing 10 ^-14 [S / m], specific gravity; 0.68). This solid-liquid mixture is put into the stirring vessel so that the position of the stirring vessel at a height of 130 mm (position (v) in FIG. 3 (a)) becomes the stationary liquid level, The surface potential meter (KSD-109 manufactured by Kasuga Electric Co., Ltd.) was placed on the position on the static liquid surface with a distance of 45 mm (position (vi) in FIG. 3A; position where the height from the bottom of the stirring vessel was 175 mm)). ) Was installed.

The solid-liquid mixture in the stirring vessel is continuously stirred for about 1 hour at each of the stirring rotational speeds of 300 rpm (5 s ⁻¹ ), 450 rpm (7.5 s ⁻¹ ), and 600 rpm (10 s ⁻¹ ), Measurements were made with a surface electrometer attached at positions i) to (vi). FIG. 4 shows the results obtained by converting the measured analog output value of the surface electrometer into electric field strength according to the conversion formula shown in Table 1. The electric field strength calculated based on the value measured at the position (ii) is shown as the electric field strength at the position of the side wall 70 mm.

[Examples 2 and 3]
The electric field strength is the same as that in Example 1 except that the prepared solid-liquid mixture is used so that the concentration by weight of the powder is 20 wt% (Example 2) or 40 wt% (Example 3). It was determined. The results are shown in FIG. 5 (Example 2) and FIG. 6 (Example 3).

Example 4
Melamine resin (volume resistivity: 1.0 × 10 ^{10 to} 1.0 × 10 ¹² [Ω · m], specific gravity: 1.25) is used as the powder, and the solid-liquid mixture is adjusted so that the weight% concentration of the powder is 20 wt%. The electric field strength was determined in the same procedure as in Example 1 except for the preparation. The result is shown in FIG.

Example 5
Except that alumina (volume resistivity: 3.0 × 10 ⁹ [Ω · m], specific gravity: 4.00) was used as the powder, and the solid-liquid mixture was prepared so that the concentration by weight of the powder was 20 wt%. The electric field strength was determined in the same procedure as in Example 1. The result is shown in FIG. In FIG. 8, the value surrounded by a broken-line circle is that the surface electrometer is overscaled. Therefore, the electric field strength is determined by the measured value immediately before the overscale.

  From each of the above examples, it can be seen that the electric field strength on the side surface of the stirring vessel changes depending on the installation position of the electric field sensor and the stirring speed. It can also be seen that the electric field strength varies depending on the contents to be stirred. From this, it is suggested that it is very useful to evaluate the electric field strength of the stirring tank in the actual apparatus using the knowledge about the electric field strength obtained by the electric field measuring device.

  The electric field measurement apparatus of the present invention predicts the magnitude of the electric field strength and its positional bias on the wall surface of the stirring tank when stirring the insulating substance in the stirring tank whose inner wall is coated with an insulating material. Can be used. As a result, the amount of charge on the inner wall of the stirring tank, which is difficult to measure, can be estimated approximately, so that dielectric breakdown of the stirring tank can be prevented.

It is a schematic sectional drawing which shows one Embodiment of the electric field measuring apparatus in this invention. (A) is a top view of the electrode for electric field calibration, (b) is A-A 'arrow sectional drawing which shows (a). (A) is a schematic sectional drawing of the stirring container used in the Example, (b) is an upper surface top view of the stirring container shown to (a). It is a graph which shows the electric field strength in the side wall of a stirring container at the time of stirring the solid-liquid mixture of the polypropylene and n-heptane whose polypropylene is 10 wt% in an electric field measuring device. It is a graph which shows the electric field strength in the side wall of a stirring container at the time of stirring the solid-liquid mixture of the polypropylene and n-heptane whose polypropylene is 20 wt% in an electric field measuring device. It is a graph which shows the electric field strength in the side wall of a stirring container at the time of stirring the solid-liquid mixture of polypropylene and n-heptane whose polypropylene is 40 wt% in an electric field measuring device. It is a graph which shows the electric field strength in the side wall of a stirring container at the time of stirring the solid-liquid mixture of melamine resin and n-heptane whose melamine resin is 20 wt% in an electric field measuring device. It is a graph which shows the electric field strength in the side wall of a stirring container at the time of stirring the solid-liquid mixture of the alumina and n-heptane whose alumina is 20 wt% in an electric field measuring device.

Explanation of symbols

1 Stirring container 1a Flask (insulating container)
1b Conductive adhesive tape (conductive sheet)
1c Sensor mounting part 2 Stirrer 3 Baffle 4 Motor 5 Controller with torque meter (controller)
6 Computer 7 Sample top electric field sensor 8 Electric field sensor 9 Analog / digital converter (A / D converter)
10 ground electrode 10a hole 11 voltage application electrode 12 post

Claims (6)

An electric field measuring device for predicting the electric field strength of an agitation tank provided in an agitator for an actual machine and having an inner wall coated with an insulating material,
An insulating container formed of a material having an insulating property equivalent to the insulating material, a conductive sheet covering the outer surface of the insulating container, and an electric field sensor,
An electric field measuring apparatus, wherein the electric field sensor is provided in a region where the conductive sheet covering the outer surface of the insulating container is partially cut out and the outer surface of the insulating container is exposed. .   The electric field measuring apparatus according to claim 1, wherein the insulating container has a geometric shape that is substantially similar to the stirring tank.   3. The electric field measuring apparatus according to 1 or 2, wherein the electric field measuring apparatus is used for predicting an electric field intensity of the stirring tank when the insulating substance is stirred in the stirring tank. An electric field measurement method for predicting the electric field strength of an agitation tank provided in an agitator for an actual machine and having an inner wall coated with an insulating material,
The outer surface of the insulating container exposed by covering the outer surface of the insulating container formed of a material having the same insulating property as the insulating material and covering the conductive sheet and partially cutting the conductive sheet. An electric field measuring method, comprising: measuring an electric field strength of   The electric field measuring method according to claim 4, wherein the insulating container has a geometric shape that is substantially similar to the stirring vessel. 6. The electric field measuring method according to claim 4, wherein the electric field strength of the stirring tank is predicted when the content stirred in the stirring tank is an insulating substance.

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