JPS6049006B2 - Backwashing method in electromagnetic filter type furnace tower - Google Patents

Description

Detailed Description of the Invention The present invention provides an electromagnetic filter type filtration tower in which the inside of the filtration tower is filled with a magnetic material and an electromagnetic coil is arranged around the outside of the filtration tower. The present invention relates to a method for backflowing an electromagnetic filter type filtration tower to efficiently remove water from the filtration tower.

In general, an electromagnetic filter type offshore filter tower has a filtration tower filled with a magnetic material, and an electromagnetic coil placed around the filtration tower to generate a magnetic field. Adsorbs and captures paramagnetic and ferromagnetic fine particles contained in
The fine particles are separated and removed from raw water.

However, if fine particles are accumulated in the magnetic material filled in the filtering tower during operation, this will lead to an increase in the pressure loss of the filtering tower and deterioration of the quality of the treated water. A backwashing operation is carried out at appropriate time intervals to remove the fine particles captured by the magnetic material from the overflow tower. FIG. 1 is an explanatory diagram of a water treatment flow using a typical electromagnetic filter type offshore tower, and the general backwashing method carried out in this water treatment flow will be outlined below.

During operation of the overflow tower 1, raw water containing fine particles is supplied from the lower part of the overflow tower 1 to the electromagnetic filter by opening the valve 11. This electromagnetic filter consists of magnetic thin wires filled in the filter tower 1,
It includes a magnetic body 2 such as a magnetic porous plate, and the magnetic body 2 is excited by an electromagnetic coil 3. The raw water that is passed through the percolation tower 1 is separated and removed by the adsorption and capture of the paramagnetic and ferromagnetic fine particles contained therein by the excited magnetic material 2, and then passed through the valve from the upper part of the percolation tower 1. 12 and is discharged as treated water. The backwashing operation for removing the fine particles captured by the magnetic material 2 from the offshore tower 1 by the operation of flowing the raw water is carried out according to the procedure described below.

The mass valves 11 and 12 are closed to stop the flow of raw water, and the electromagnetic coil 3 is stopped. Next, valves 13 and 14 are opened, and valve 13
Pressurized air of 3 to 5 k9/d is supplied from the upper part of the filtration tower 1, and the water in the filtration tower 1 is discharged to the outside of the filtration tower 1 all at once through the valve 14. At this time, the electromagnetic fan. The filter is backwashed, but the backwash flow rate is 4 times faster than the normal water flow rate.
~1C@, and also has the effect of creating a gas-liquid mixed flow, forcibly separating the fine particles captured by the magnetic material 2,
Discharged to the outside of the tower along with backwash water. FIG. 2 is a graph showing an example of the relationship between the backwashing efficiency and the number of times of backwashing according to the backwashing method performed according to the above-described procedure.

However, backwash efficiency is defined by the following formula. η (%) = To Φ cutting 00 η (%): Backwash effective flow A: Amount of particulates captured by the magnetic material B: Amount of particulates removed by backwashing N: Number of times of backwashing It is clear from Figure 2 As shown, the backwash efficiency η (%) decreases as the number of backwashes N increases.

This reduction in backwashing efficiency means an increase in the amount of fine particles remaining in the magnetic material, resulting in an increase in pressure loss in the filtration tower.
This will lead to negative effects such as deterioration of treated water quality. and,
In particular, when there are many paramagnetic particles in the raw water, the ability of the magnetic force to capture the paramagnetic particles is small, which further deteriorates the quality of the treated water. This invention was made in view of the above-mentioned actual situation, but one of the reasons why backwashing efficiency decreases is that fine particles that cannot be removed by backwashing increase on the surface of the magnetic material. This is based on the knowledge that it strongly adheres to magnetic materials due to the positive and negative surface charges it possesses.

In other words, when performing backwashing in an electromagnetic filter-type offshore tower, the present invention removes water containing particles having a zeta potential opposite to the surface charge of the particles captured by the magnetic material into the P filter tower. The method is characterized in that water is circulated through the magnetic material to neutralize the charge on the particles trapped on the surface of the magnetic material, and then a backwashing operation is performed.

Embodiments of the present invention will be described in detail below with reference to FIGS. 3 and 4.

Under the conditions shown in Table 1 below, raw water containing α-Fe2O3, which is fine particles with a positive zeta potential, is passed through the electromagnetic filter type offshore tower 1 shown in Figure 3, and backwashed every 3 days. After performing the operation, the backwashing efficiency was 6 after 5 times of backwashing.
It decreased to 0%.

Therefore, a backwashing method according to an embodiment of the present invention was carried out according to the procedure described below. In FIG. 3, the supply of raw water was stopped and valves 11 and 12 were closed. Next, the electromagnetic coil 3 was stopped, the valves 13 and 14 were opened, and the water in the offshore tower 1 was pushed out by a normal backwash operation. Subsequently, valves 13 and 14 were closed, valves 21 and 22 were opened, and water containing Fe3O4, which is fine particles having a negative zeta potential, was circulated for three minutes under the conditions shown in Table 2 below. At this time, the electromagnetic coil 3 may or may not be excited, but if the particles to be injected are ferromagnetic particles as in this example, the electromagnetic coil 3 can be excited to make the injected particles into a magnetic material. This has the effect that it can be efficiently attached to 2. After completing the circulation of the injected fine particle-containing water, close the valves 21 and 22, and close the valve 13.
, 14 were opened and the backwashing operation was performed again to push out the water in the filtering tower 1. When the amount of particulates in the backwash water discharged by this operation was measured, it was found to be 20% greater than the amount of injected particulates. Therefore, according to the embodiment of the present invention described above, it was also confirmed that the particulates remaining in the magnetic material of the electromagnetic filter were removed. Next, under the conditions shown in Table 3 below, raw water containing fine particles of Fe3O4 having a negative zeta potential was passed through in the same manner as above, and backwashing was performed every three days.
The backwashing efficiency decreased to 80% after 5 backwashings.

Therefore, in the same way as in the above example, this time, under the conditions shown in Table 4 below, fine particles having a positive zeta potential were
After circulating e2O3-containing water for 30 minutes, a backwash operation similar to that described above was performed, and it was found that the amount of fine particles in the discharged backwash water was 15% greater than the amount of injected fine particles. Therefore, in this example as well, it was confirmed that the particulates remaining in the magnetic material of the electromagnetic filter were removed. If the raw water to be treated contains particles with both positive and negative zeta potentials, injection of particles with negative zeta potential and injection of particles with positive zeta potential are performed sequentially. Either to electrically neutralize each of the two types of fine particles, and then perform a backwash operation, or to remove the largest amount of both types of fine particles to the magnetic material 2 of the electromagnetic filter using a normal backwash operation. What is necessary is to inject water containing fine particles having a zeta potential of opposite polarity to that of the fine particles remaining on the surface.

As explained above, by carrying out the backwashing method according to the embodiment of the present invention, it is possible to efficiently remove particulates remaining in the packed magnetic material in an electromagnetic filter type overpass tower.

Although FIG. 4 differs from that shown in FIG. 3 in the configuration of the electromagnetic filter used, it is also an explanatory diagram of the backwashing method according to the present invention. The electromagnetic filter shown in FIG. 4 differs from the electromagnetic filter shown in FIG. 3 only in that the electromagnetic coil is divided into a coil 3A and a coil 3B, and other points are common. The procedure for carrying out the backwashing method according to this embodiment in this offshore tower 1 will be described below. First, the supply of raw water is stopped and valves 11 and 12 are closed.

Next, the coils 3A and 3B are stopped, the valves 13 and 14 are opened, and the water in the offshore tower 1 is pushed out by a backwash operation. Subsequently, only the coil 3B is energized and the valves 21 and 22 are opened to collect particles having either positive or negative zeta potential of opposite polarity depending on the polarity of charge of the particles remaining on the magnetic body 2 of the electromagnetic filter. The contained water is passed through and circulated. Injected fine particles are magnetic material 2
Most of the part of the coil 3B that is excited is captured, and especially when the injected particulates are made of ferromagnetic material, the injected particulates are almost completely captured in this part and sent into the circulating water. There will be no leakage7. After the circulation of the injected water is completed, the valves 21 and 22 are closed, and all the electromagnetic coils are stopped. Therefore, the valves 13 and 14 are opened to perform a backwash operation and push out the water in the offshore tower 1. According to the embodiment described with reference to FIG. 4, most of the injected particles are captured at the upper part of the magnetic body 2 by the excited coil 3B, so that the injected particles can be efficiently removed during the backwash operation. It has the effect of promoting electrical neutralization by bringing it into contact with the fine particles remaining in the magnetic material, and also has the effect of preventing contamination of the outlet of the filtration tower by circulating water containing the injected fine particles.

As understood from the above explanation, the present invention is based on the electromagnetic filter type? It is possible to efficiently remove the fine particles remaining in the magnetic material filled in the overflow tower, prevent an increase in pressure loss in the overflow tower, and maintain a stable quality of treated water when the overflow tower is in operation.

[Brief explanation of the drawing]

Is Figure 1 an electromagnetic filter type? An explanatory diagram of a conventional backwashing method in a filtration tower, FIG. 2 is a graph showing backwashing performance by a conventional backwashing method, and FIGS. 3 and 4 are a backwashing method in an electromagnetic filter type sake filtration tower according to the present invention. It is an explanatory diagram. 1... Electromagnetic filter type p-pass tower, 2...
Magnetic material, 3... Electromagnetic coil, 11 to 14, 21
,22...valve.

Claims (1)

[Scope of Claims] 1. In an electromagnetic filter type filtration tower in which an electromagnetic coil is arranged around the outer periphery of a filtration tower filled with a magnetic material, raw water is captured by the magnetic material by a backwashing operation after running through the raw water. A method for excluding particulates to the outside of the filtration tower, which method includes, before the backwashing operation,
A backwashing method for an electromagnetic filter type filtration tower, characterized in that water containing particulates having a zeta potential of opposite polarity to that of the particulates in raw water is circulated through the filtration tower, and then a backwashing operation is performed. 2. Claim 1, characterized in that an electromagnetic coil of an electromagnetic filter is excited when circulating particulate-containing water having a zeta potential of opposite polarity to the polarity of the particulates in raw water through a filter tower. Backwashing method in the electromagnetic filter type filtration tower described. 3. In an electromagnetic filter type filtration tower in which a plurality of electromagnetic coils are divided and arranged around the outer periphery of a filtration tower filled with a magnetic material,
A method of removing particulates captured by magnetic materials from the filtration tower by a backwashing operation after the raw water is in operation, and stopping the excitation of the electromagnetic coils except for some electromagnetic coils before the backwashing operation. In this state, particulate-containing water having a zeta potential opposite to that of the particulates in the raw water is circulated through the filtration tower, and then the excitation of all electromagnetic coils is stopped to perform a backwashing operation. Features of backwashing method in electromagnetic filter type filtration tower.