JPS6044964B2 - Method for collecting particles captured by magnetic separator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic separator, and more particularly, to a magnetic separator, a filler made of magnetic thin wires is placed in a vertical casing, and a magnetic field is applied to the fluid passing through the casing from the bottom to the top. The present invention relates to a method for collecting captured particles in a magnetic separator that separates magnetic particles.

Magnetic separators have been used to upgrade low-grade iron ore and remove iron from ceramic raw materials.

Recently, with the development of high-gradient magnetic separation methods, it has become possible to magnetically capture paramagnetic particles, which has been applied to the removal of heavy metals from industrial wastewater and the removal of radioactive iron from primary cooling water of nuclear reactors. I started to do that. In high-gradient magnetic separators, magnetic wires are filled in a magnetic field to generate a large magnetic field gradient. As the capture of magnetic particles onto the magnetic wire progresses, the effective radius of the magnetic wire becomes thicker, the capture rate decreases, and the flow path is blocked by the magnetic particles, resulting in an increase in pressure loss. Therefore, after temporarily stopping the capture operation and stopping the power supply to the electromagnetic coil for generating the magnetic field, an operation is adopted in which the magnetic particles are separated from the magnetic wire and collected by flowing backwash water. . With this method, if it is easy to perform backwash water operation or concentration operation after removing magnetic particles, such as when recovering iron from steelworks wastewater or removing heavy metals from factory wastewater, it is possible to use some backwashing. Even if there is a lot of water, it won't be much of a problem. However, when treating radioactive waste liquid or nuclear reactor cooling water, it is desirable to reduce the amount of backwash water as much as possible from the viewpoint of processing highly radioactive waste liquid. In order to remove trapped particles using normal backwash water operations, it is necessary to use high-pressure water to flow at a sufficiently high flow rate, resulting in an increase in the amount of highly radioactive waste liquid. An object of the present invention is to provide a method for collecting captured particles in which magnetic particles captured on magnetic fine wires of a magnetic separator are separated and recovered using as little treated water as possible.

The feature of the present invention is that, as a result of various studies on the release conditions for captured particles, it was found that particles captured on magnetic thin wires are released only when electricity to the electromagnet is stopped and water is not passed at a flow rate of several tens of cm/s or more. Although it is difficult to do so, we discovered that by forcibly introducing air bubbles into the magnetic fine wire filling part, the trapped particles can be easily separated from the magnetic particles, and we introduced gas from below the magnetic fine wire filling. Captured particle recovery consists of a step of detaching the captured particles from the surface of the packing, and a step of flowing backwash water from above to below the magnetic fine wire packing to recover the detached magnetic particles. It consists in adopting a method.

The present invention will be explained below with reference to the drawings.

Figure 1 is an overall configuration layout diagram when a magnetic separator that adopts the recovery method of the present invention is applied to purify nuclear reactor primary cooling water, where 1 is a nuclear reactor and 2 is a drive for the heat generated by this reactor. 3 is a condenser, 4 is a primary cooling water purification system, 5 is
6 indicates an ion exchange column, 6 indicates a magnetic separator, 7 indicates a backwash water inlet into which backwash water used in the magnetic separator 6 flows, and 8 indicates a backwash water outlet.

FIG. 2 is a drawing for explaining details of the magnetic separator 6.

The high gradient magnetic separator 11 is constructed by arranging a filler 14 made of magnetic thin wire inside a vertical casing 12 and applying a magnetic field to the magnetic thin wire filler 14 using a coil 13 provided outside the casing. configured. Cooling water containing radioactive iron oxide is introduced into the casing 12 from the purification system process flow of the reactor primary cooling water through a valve 20 located below the casing 12 . Most of the particles of Fe3O4 and Fe2O3 contained in the primary cooling water are captured on the magnetic wires of the magnetic wire packing 14. The primary cooling water containing uncaptured particles is returned to the purification system process stream via a valve 21 located above the casing 12. As the trapping operation progresses, the particles are captured double or triple on the magnetic fine wire, so the magnetic fine wire packing 14
The particle capture efficiency will be reduced. Moreover, since a part of the flow path is blocked, pressure loss increases. After determining the capture limit of the high gradient magnetic separator 11 by measuring pressure drop, etc., the valves 20 and 21 are closed to separate the magnetic separator from the process stream. Next, the valve 22 is opened to send argon or nitrogen gas to the gas introduction pipe 16 and discharged from the gas blowing nozzle 17.

At this time, a gas blowing pressure of several kg/Cd is sufficient. The released gas passes through the baffle plate 15 and rises from the bottom to the top of the magnetic fine wire packing 14 in the form of bubbles. The air bubbles mix with the primary cooling water remaining in the casing 12, and some of the primary cooling water rises inside the magnetic fine wire packing 14 along with the air bubbles, but immediately falls down due to its own weight. Due to the rise of the bubbles and the falling of the primary cooling water, the particles captured on the magnetic wire are easily separated from the magnetic wire. At this time, power to the coil 13 is stopped. Furthermore, valve 2
Valve 23 is kept open during the upper air blowing operation.
For example, the gas discharged from the reactor is treated in a radioactive gas processing facility (not shown). After the separation of the captured particles from the magnetic wire by the bubbles is completed, the valves 22 and 23 are closed,
The valve 24 is opened and backwash water is introduced via the backwash water introduction pipe 18 to wash out the radioactive particles staying in the casing 12 and discharged to the outside of the system via the valve 25.

In the above operation, almost no backwash water is required to remove the captured particles, and only necessary for washing out, making it possible to significantly reduce the amount of backwash water compared to conventional methods. As explained above, according to the present invention, magnetic particles captured on the magnetic wire of a magnetic separator can be recovered with a very small amount of treated water.

In the above embodiment, only the treatment of primary cooling water of a nuclear reactor was explained, but the method of the present invention can be applied not only to the removal of magnetic particles from radioactive waste liquid, but also to the removal of impurities from general liquid waste. It is also effective when it is necessary to reduce the volume.

[Brief explanation of drawings]

FIG. 1 is an overall layout diagram when a magnetic separator is applied to purify primary cooling water of a nuclear reactor, and FIG. 2 is an explanatory diagram of an embodiment of the present invention. 12...Casing, 13...Coil, 1
4... Magnetic thin wire filling, 15... Current plate, 16... Gas introduction tube, 17... Gas blowing nozzle, 18... Backwash water introduction pipe, 20-2
5...Valve.

Claims (1)

[Claims] 1. In a magnetic separator that separates magnetic particles in a fluid that passes through the casing from the bottom to the top by filling and arranging a filler made of magnetic fine wires in a vertical casing and applying a magnetic field, the magnetic particles captured by the filler are The particles are separated from the surface of the packing by introducing gas from below the packing, and after this step, backwash water is flowed downward from above the packing to remove the separated magnetic particles. 1. A method for collecting captured particles in a magnetic separator, comprising the step of collecting.