JPH0365699A - Recovering and reusing device for abrasive grain in dry grain blasting abrasive device - Google Patents

Abstract

PURPOSE:To intend to realize a sound particle size classification by vacuuming abrasive grains, by making an air flow of vacuuming rise up from a lower end of a straight stand pipe which is provided at an upper part of an abrasive grain collecting tank, and by dropping and collecting the abrasive grains having sizes larger than those can be borne by the air flow velocity. CONSTITUTION:Abrasive grains 3 which are transferred by a suction hose 4 are discharged upwardly from a spouting end 7 of the suction hose 4 at a lower part of a straight stand pipe 6 erected on an upper part of an abrasive grain collector 5. An inner diameter of the straight stand pipe 6, is designed to give a final falling velocity corresponding to a required size of an abrasive grain diameter to be collected. Coarse grains from which fine grains are already removed by a wind power grain classification in the straight stand pipe 6, are dropped down into a rotary tank 5 and then are spouted again and used as abrasive grains for a contamination removal work. An air flow exhausted from a fine grain discharge pipe 8 which is connected to an upper end of the straight stand pipe 6, is sucked and exhausted by a volume typed blower 12 after a dust collection by a cyclon 9 and bag filter 10.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is used in nuclear reactor equipment to recover and reuse abrasive particles used when decontaminating members contaminated with radioactive materials using an abrasive jet polishing device. It is related to the device.

(Prior technology) The abrasive particles injected by an abrasive jet polishing device are collected and reused to continue work. Since the abrasive particles are crushed during use, it is necessary to replenish and remove the crushed abrasive particles. becomes.

Decontamination of nuclear reactor equipment involves work inside a sealed house, so a method is expected to reliably remove powder from recovered abrasive grains in order to ensure visibility and prevent radioactive materials that collect on the grinding abrasive grain side. has been done.

Conventionally, (1) a sieve is used, and (2) a cyclone or the like is installed in the suction and recovery line. (3) Measures such as providing a simple bend in the airflow of the suction and recovery line to separate coarse particles have been taken.

Although the sieve in (1) above is reliable, the equipment is large and the sieve mesh is subject to a lot of wear and tear.The cyclone in the line in (2) is originally a device for collecting fine particles. Therefore, when the abrasive grains are separated (several 100 μm), fine particles are recovered, and there is a problem in that the wear of the equipment is also large. Furthermore, the method (3) of providing a bending part makes it easy to aim for separation of abrasive grains with a size of several 100 microns, but it is sensitive to changes in the shape of the ventilation passage due to changes in air volume and deposits in the pipe, and the location where the abrasive grains settle is However, there are some drawbacks such as changes in the data, resulting in poor accuracy.

(Problems to be Solved by the Invention) An object of the present invention is to provide an abrasive grain recovery and classification device that can solve the problems of the prior art described above, such as large size, wear and tear, and poor classification accuracy. do.

(Means for solving the problem) In order to collect and reuse the used abrasive grains deposited on the floor during polishing work in the work house, the abrasive grains 3 are first vacuum-suctioned, and the airflow is transferred to the abrasive grain collection tank 5. It is raised from the lower end of an upright tube 6 provided at the top of the tube. Abrasive grains in the rising air, those with a particle size larger than the wind speed, fall and are collected, *The powder rides on the air current and is collected for the next process! Collected at I9 and 10.

The air velocity (that is, the air volume) that regulates the classification size in the upright tube 6 is operated by a positive displacement fan 12 that can be easily kept substantially constant without depending on the resistance change of the ventilation line, and is also provided with an air volume control valve 11. Furthermore, a vacuum breaker valve 14 is provided at one end of the suction hose 4 that sucks the deposited abrasive grains, so that even if the suction port is suddenly blocked during suction of the deposited abrasive grains 3, the vacuum breaker valve 14 is installed in the suction hose 4. It was opened to draw in outside air and ensure the amount of ventilation in the ventilation line. By these measures, the amount of air passing through the upright cylinder 6 is kept substantially constant, and the abrasive grains can be classified within the upright cylinder 6 with high accuracy. Note that the lower part of the upright cylinder 6'' was sealed from the outside air and communicated with the abrasive grain recovery tank 5.

(Example) An example of the present invention will be described with reference to the drawings. In the work of spraying dry abrasive grains 2 to decontaminate reactor contaminated parts 1, the deposited abrasive grains 3 scattered on the floor are collected and reused. The deposited abrasive grains 3 carried by the suction hose 4 are ejected upward from the spouting end 7 of the suction hose 4 into the upright cylinder at the lower part of the upright cylinder 6 erected above the abrasive grain recovery tank 5. The inner diameter of the upright cylinder 6 is determined by the final falling velocity (
terminal velocity).
Design using the Newtonian method of sedimentation.

The coarse grains from which fine powder has been removed by air classification in the upright cylinder 6 are dropped into the abrasive grain recovery tank 5 and are used again by injection as abrasive grains for decontamination work. The airflow containing fine particles discharged from the fine powder discharge pipe 8 connected to the upper end of the upright cylinder 6 is transferred to the following cyclone 9. After the dust is collected by the bag filter IO, it is sucked and exhausted by the air volume control valve 11 and the positive displacement exhaust fan 12.

On the other hand, even if the suction end of the suction hose 4 accidentally becomes blocked, the suction operation of the deposited abrasive grains 3 with the suction hose 4 is carried out by the vacuum breaker valve 14 provided near the suction end of the suction hose 4.
The negative pressure inside the hose on the 3 side increases, the vacuum breaker valve 14 opens, and outside air is sucked in to keep the air volume inside the suction hose 4 constant. This has the effect of keeping the classification air speed in the upright tube 6 constant, in combination with the displacement type exhaust fan (for example, a Roots blower) 12, which makes it easy to obtain a relatively constant air volume even if the external ventilation resistance increases or decreases.

FIG. 2 is a sectional view showing an example of the vacuum breaker valve 14. An opening 14a is provided on the side of the suction hose 4, and the opening 14a is closed with a lid 14b. An adjustment screw 14c is screwed into the center of the lid 14b, and the set pressure can be adjusted by the screw 14c.

That is, at the lower end of the adjustment screw 14c there is a spring 14f held by a spring holder 14d which itself has a ventilation section.
The spring force of the spring 14f is adjusted by a pressing plate 14e that is moved up and down by an adjusting screw 14c.

When the vacuum pressure inside the suction hose 4 becomes excessive, the lid 14b
is pulled open (pushed by atmospheric pressure), and outside air flows in from the opening 14a as shown by the arrow, reducing the vacuum pressure.

In addition, 15 is a work house where the spraying work of abrasive grains 2 and suction work with an abrasive grain suction hose are divided and sealed, and 16 is a work house 15.
617 is a wire mesh inside the abrasive grain collection tank 5, 18 is a sand storage switching valve, 19 is an abrasive grain storage tank, and 20 is an abrasive grain supply valve. be. 21 is compressed air for injection, 22 is a sealed collection dust container for the cyclone, and 23 is a sealed collection dust container for the bag filter.

(Effects) l) Since wind classification is performed by gravity falling of the abrasive grains and rising air current in the upright tube 6, the abrasive grain diameter is relatively coarse (several 100 μm).
Classification is carried out reliably.

2) Since the abrasive grains are classified during air flow transport, coarse grains and fine grains are separated in space, and there is no adhesion between coarse grains and fine grains, resulting in excellent classification efficiency.

3) By changing the air volume using the air volume control valve 11, the classified particle size can be changed freely.

4) By using the positive displacement exhaust fan 12 and the vacuum breaker valve 14 in combination, it is easy to maintain a constant wind speed (ie, air volume) necessary for wind classification.

5) As an operational effect, by using the vacuum break valve 14, the suction hose 4, which is a typical trouble in suction air flow transportation, can be removed.
This prevents the tube from being blocked at the rising end (which occurs when the ratio of powder amount/air amount increases when the suction port is suddenly blocked).

6) The classification flow rate in the upright tube 6 is several meters per second or less, so there is little wear on the equipment, and the equipment is simple and compact.

7) Since fine powder (crushed abrasive grains and radioactive material fine powder scraped off) is continuously removed from the flow of abrasive grains during collection and use, the visibility and work environment inside the work house 15 are extremely good. It is maintained.

[Brief explanation of drawings]

FIG. 1 shows the structure and arrangement of the abrasive material recovery and reuse device of the present invention and related equipment in which this device is used. Figure 2 is a diagram of the principle of the vacuum breaker valve. In the figure: 1 Contaminated member 2 Abrasive grains 3 Deposited abrasive grains 4 Suction hose 5 Collection tank 6 Upright tube 7 Spout end (of suction hose) 8 Fine powder discharge pipe 9 Cyclone lO bag filter 11 Air volume control valve 12 Positive displacement exhaust fan 13 ( Suction hose) Suction end vacuum break valve 15 Work house Suction purification piping wire mesh inside the house 18 Sand storage switching valve Abrasive grain storage tank 20 Abrasive grain supply valve Sealed collection dust container for compressed air cyclone Sealed collection dust container for bag filter and above

Claims (1)

[Claims] In dry abrasive jet polishing equipment for decontaminating nuclear reactor equipment,
A vacuum breaker valve (14) is provided on the suction end (13) side of the suction hose (4) that collects accumulated abrasive grains during spray polishing in the work house (15), and the other end of the suction hose is connected to the abrasive The lower part of the upright cylinder (6), which has a cylinder diameter that provides the upward wind speed necessary for the particle falling classification and collection size, is opened upward, and the upper end of the upright cylinder (6) is used for dust collection through the fine particle discharge pipe (8). Vessel (9
, 10) and a positive displacement exhaust fan (12) equipped with an air volume control valve (11), while the lower end of the upright cylinder (6) was connected to the upper part of the abrasive grain collection tank (5) in a closed state to outside air. An abrasive grain recovery and reuse device in a dry abrasive jet polishing device characterized by the following.