JP3686944B2 - Nozzle type static eliminator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a static eliminator (a static eliminator) for efficiently removing static electricity from powders and other objects that are not charged with electrostatic charges in industrial processes.
[0002]
[Prior art]
In processes such as pneumatic piping transportation, static electricity is generated with the collision of powder with the tube wall. As a result, when the charged powder is accumulated in a silo or the like, a discharge is generated in the suspended dust or on the deposited powder layer, which may cause a dust explosion. Development of devices for removing static electricity from such powders has already been attempted, and some devices are commercially available.
[0003]
As such a conventional apparatus, a high voltage is applied to a needle-like or wire-like electrode, a corona discharge is generated between a flat or cylindrical ground metal object, and charged particles ( The mainstream is to remove the ions by neutralization by binding of different charges by sending ions) to the charged object using compressed air flow or electrical attraction.
[0004]
An apparatus for generating charged particles for neutralization is generally called an ionizer.
[0005]
[Problems to be solved by the invention]
However, the conventional static eliminator has the following drawbacks. That is,
(1) Since a corona discharge is generated by applying a high voltage to the electrode, it is a matter of course that a high voltage power supply is required. However, the discharge electrode and the ground electrode are When approaching abnormally, there is a possibility of generating sparks that are ignitable with respect to combustible dust and gas / steam.
(2) AC or DC is used as the voltage to be applied. In the former case, there are cases where the amount of ions generated is insufficient and the charge cannot be completely removed. It may be charged to the opposite polarity to the charging polarity.
[0006]
The present invention has been made paying attention to this point. The possibility of generating an ignitable discharge is remarkably small (it can be considered to be an explosion-proof specification) and always obtains an appropriate static elimination performance. it is an object of the present invention to provide a Roh nozzle type static eliminator Do that enables.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, a nozzle type static eliminator according to claim 1 is a closed circuit such as a pipe for passing a charged object, and is made of an insulating material, and the entire circuit is electrically insulating. The first nozzle made of a material or a part including a tip part including a tip is a metal material, and the remaining nozzle is a second nozzle made of an insulating material, and a grounded needle provided in the nozzle A nozzle type ionizer having an electrode is attached, and when the nozzle is the first nozzle, the closed circuit is charged to the same polarity as the charged object with the passage of the charged object. the charged object and in accordance with the electrostatic field concentration effects on the needle electrode due to charging of the closing position, whereas, the nozzle in the case of the second nozzle, said charged bodies and the closed positioned near the nozzle Accompanying the charging of In response to said electrostatic field concentration effects on the needle electrode due to charging of the metallic material which is insulated by an insulating material, to generate a corona discharge of the charged object and the opposite polarity to the needle electrode, which is generated by the corona discharge The charged object is efficiently neutralized by air ions for neutralization .
[0008]
Preferably, the nozzle type ionizer further includes a supply means for supplying a forced air into the nozzle from the outside, the air which has the feed, thereby releasing the charge removing air ions generated by the corona discharge It is characterized by.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[0011]
FIG. 1 is a cross-sectional view showing a schematic configuration of a nozzle-type static eliminator 1 according to an embodiment of the present invention, as viewed from the direction of arrow Ii in FIG.
[0012]
FIG. 2 is an enlarged sectional view of the ionizer 2 constituting the nozzle type static eliminator 1, and FIG. 3 is a partial sectional view of an experimental apparatus for evaluating the performance of the nozzle type static eliminator 1.
[0013]
As shown in FIG. 3, the nozzle type static eliminator 1 of the present embodiment is used by being attached to a terminal of a powder filling pipe 13 (corresponding to “closed circuit” in claim 1) of a silo 11, As shown in FIG. 1, a plurality of (for example, “holder”) 3 (for example, “holder”) 3 made of an insulating material (for example, PVC (polyvinyl chloride)) having the same diameter as the outer diameter of the powder filling pipe 13. 8) nozzle type ionizers 2 are attached.
[0014]
More specifically, two nozzle ionizers to be attached are provided with small holes such that the tip of each cap portion 2a of each nozzle ionizer 2 is flush with the inner surface of the holder 3 or does not protrude from the inner surface , that is, Eight pieces are spaced around the holder 3 at equal intervals, and the respective heads of the nozzle type ionizers 2 are fitted into the respective holes, and fixed from the outside on the circumference of the holder 3 with fixing brackets and metal screws (not shown). ing. Note that the metal nozzle, the fixing bracket, and the metal screw are in metal contact with each other, and the eight nozzles are electrically connected by the bonding wires 4 (the whole is insulated from the other by the resin of the main body 2f described later). ). The reason why the metal nozzle, the fixing bracket and the metal screw (metal nozzle or the like) are electrically connected in this way is as follows. That is,
(1) As will be described later, it is possible to increase the capacitance with the charged holder 3 to increase the amount of charge induced by electrostatic induction in a metal nozzle or the like. (2) Since the tip of the screw is exposed from the inner wall through the insulator, it is expected that a weak corona discharge will be generated here to collect the charge of the surrounding insulator and powder, which further increases the metal Electric charges are supplied to the nozzle or the like, and discharge from the needle electrode can be continuously generated.
[0015]
Each nozzle ionizer 2 includes a cap part 2a made of metal, a main body part 2f made of an insulator (for example, epoxy resin), and a supply part 2g for supplying compressed air to the inside of the cap part 2a via the main body part 2f. , Mainly composed.
[0016]
A hole 2a1 for releasing compressed air supplied from the supply unit 2g is provided at the tip of the cap unit 2a.
[0017]
The main body 2f is provided with a needle electrode 2b via a metal receiver 2c, and the needle electrode 2b is grounded via a resistor 2d having a high resistance value (for example, 50 MΩ) and a silicon cable 2e. As described above, the high-resistance resistor 2d is provided when there is no resistor or when a low-resistance resistor is provided, depending on the strength of the electric field at the nozzle tip. This is because the corona discharge easily becomes a spark (spark).
[0018]
A non-conductive resin (for example, a silicon resin) is poured into the chamber 2h in the body 2f in which the resistor 2d is disposed in order to fix the needle electrode 2b and insulate the resistor 2d. Moreover, the reason for using the silicon cable 2e, that is, the conductive cable covered with the silicon resin, as the conductive cable is to insulate the conductive cable.
[0019]
On the ground side of the silicon cable 2e, an ammeter 5 is also provided for measuring the value of the current flowing from the needle electrode 2b to the ground side when corona discharge occurs from the needle tip of the needle electrode 2b. However, the ammeter 5 is merely for confirming the performance of the nozzle ionizer 2 and does not constitute a feature of the present invention.
[0020]
The supply part 2g is provided with a hole 2g1 for supplying compressed air, and a cylindrical protrusion 2g2 is provided around the hole 2g1. A hose (not shown) is attached to the protrusion 2g2, this hose is attached to a compressor (not shown), and compressed air (for example, about 0.2 MPa) is supplied from the compressor via the hose.
[0021]
The main body portion 2f is provided with a vent 2f1 for passing the supplied compressed air into the cap portion 2a, and the compressed air supplied from the supply portion 2g is supplied into the cap portion 2a via the main body portion 2f. And released into the holder 3 from the hole 2a1 provided in the cap portion 2a.
[0022]
As described above, the compressed air is supplied into the nozzle type ionizer 2 because the ions generated from the nozzle type ionizer 2 are quickly delivered to the charged powder and the nozzle type from the hole 2a1 of the cap part 2a. This is to prevent the powder from entering the ionizer 2.
[0023]
In the static eliminator 1 configured as described above, since the holder 3 is an insulating short tube, the charge transfer from the charged powder when filling the charged powder or the like (the exact mechanism is unknown, but the charging It is presumed that the ions generated by the discharge from the powder are attached), so that the inner surface is charged with the same polarity as the charged powder. Therefore, when the charged powder and the cap portion 2a insulated by electrostatic induction and discharge from the charging surface of the insulating holder 3 are charged and the potential reaches about 2 kV, the charged powder is interposed between this and the needle electrode 2b. Corona discharge of the opposite polarity occurs, and air ions for charge removal are efficiently generated.
[0024]
FIG. 4 is a diagram showing an example of a result obtained by applying the nozzle type static eliminator 1 of FIG. 1 to the experimental apparatus of FIG. 3 and measuring the static elimination effect.
[0025]
As shown in FIG. 4, when the transfer of the powder (for example, polypropylene pellets) p into the silo 11 is started at time ta, an electrostatic field sensor attached to the side wall of the silo 11 (monitoring of the charge amount of the pellet deposited in the silo 11). ) 14 indication reaches 2 kV / cm or more. (The charge of the pellet p is negative, and the indicated value of the electrostatic field sensor 14, the charging potential of the holder 3, and the nozzle current measured by the ammeter 5 are all negative). In this case, a discharge (ignitable discharge) accompanied by a strong light emission that is observed with the naked eye on the pellet deposition surface frequently occurs. At this point, the needle electrode of the static eliminator is insulated to prevent corona discharge (static elimination stop).
[0026]
Next, at time tb, when the needle electrode 2b is grounded through the ammeter 5 in this state, corona discharge occurs from the needle tip, the nozzle current flows, and the charged powder is discharged (discharge operation). When the electrostatic field on the wall of the silo 11 was 1 kV / cm or less, ignitable discharge was prevented, but as a result of the charge removal operation, it became almost 0 kV / cm.
[0027]
When the static elimination is stopped at time tc, the electrostatic field rises again. When the static elimination is activated at time td, the electrostatic field becomes almost zero. When the pellet transfer is stopped at time te, the nozzle current flows. Disappear.
[0028]
FIG. 4 also shows the monitoring result of the charging potential of the holder 3. When the pellet p is transferred, the charging potential rises, reaching about 15 kV when discharging is stopped, and reaching about 7 kV when discharging is performed. This confirms that charging of the insulating holder contributes to the charge removal effect.
[0029]
In the present embodiment, the cap portion 2a is made of metal. However, the cap portion 2a is not limited to this, and the cap portion 2a is entirely made of an insulating material (for example, PVC) or part of the cap portion 2a. You may employ | adopt that a (part containing a front-end | tip) consists of metal materials, and the remaining part consists of an insulating material. In these cases, it has been confirmed that there is a charge eliminating effect to prevent ignitable discharge.
[0030]
When an insulating nozzle is used, the electric field from the charged surface of the insulating holder is superimposed on the needle electrode in addition to the electric field from the charged powder, which accelerates corona discharge and efficiently generates air ions for static elimination. Is done.
[0031]
【The invention's effect】
As described above, according to the invention described in claim 1, since there is no high-voltage power supply, the possibility of generating an ignitable discharge is extremely small (it is also possible to be an explosion-proof specification), In addition, since the amount of ions necessary for charge removal is automatically adjusted depending on the charge amount of the charged object, appropriate charge removal performance can always be obtained.
[0032]
According to the second aspect of the present invention, since the ions generated by corona discharge are released by the supplied air, the static elimination performance can be further improved.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view illustrating a schematic configuration of a nozzle-type static eliminator according to an embodiment of the present invention.
2 is an enlarged cross-sectional view of an ionizer constituting the nozzle type static eliminator of FIG. 1. FIG.
FIG. 3 is a partial cross-sectional view of an experimental apparatus for evaluating the performance of the nozzle type static eliminator of FIG. 1;
4 is a diagram illustrating an example of a result obtained by measuring the neutralizing effect when the nozzle type static eliminator of FIG. 1 is applied to the experimental apparatus of FIG. 3;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Nozzle type static elimination apparatus 2 Nozzle type ionizer 2a Cap part 2a1, 2g1 Hole 2b Needle electrode 2c Receptacle 2d Resistor 2e Silicone cable 2f Main body part 2f1 Ventilation hole 2g Supply part 3 Holder 4 Bonding wire

Claims (2)

A closed circuit such as a pipe for passing a charged object, which is made of an insulating material,
A first nozzle made entirely of an insulating material or a part of a second nozzle made of an insulating material, the part including a tip portion including a tip,
A nozzle type ionizer provided with a grounded needle electrode provided in the nozzle is attached,
Utilizing the fact that the closed circuit is charged to the same polarity as the charged object as the charged object passes,
The nozzle in the case of the first nozzle in response to the electrostatic field concentration effects on the charged object and the needle electrode due to charging of the closed positioned near the nozzle, on the other hand, the nozzle of the second nozzle If, in response to the electrostatic field concentration effects on the charged object and the needle electrode due to charging of the metallic material which is insulated by the insulating material due to charging of the closed positioned near the nozzle, to the needle electrode A nozzle type static eliminator that generates a corona discharge having a polarity opposite to that of the charged object, and efficiently neutralizes the charged object with the neutralizing air ions generated by the corona discharge . The nozzle type ionizers, and characterized in that further includes a supply means for supplying a forced air into the nozzle from the outside, the air which has the feed, releasing the charge removing air ions generated by the corona discharge The nozzle type static eliminator according to claim 1.

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