JP2001170404A - Magnetic separator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic separation process for use in a coagulating sedimentation method, which enables high settling velocity of flocs through formation of magnetic flocs by using a magnetic powder as a seed agent and easy recovery/reutilization of the seed agent, and also to provide a magnetic separator for the magnetic separation process. SOLUTION: The magnetic separation process using this magnetic separator comprises, adding a magnetic powder as a seed agent to raw water in floc formation fsx to form magnetic flocs each having high specific gravity, recovering the formed magnetic flocs as sludge, and thereafter, recovering the magnetic powder from the recovered magnetic flocs, to reutilize the magnetic powder and to perform continuous operation of the magnetic separator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for coagulating sedimentation, and to coagulate sedimentation at a high sedimentation rate by coagulating solid suspended matter in raw water such as sewage, lakes, rivers and the like with magnetic powder, and solid floating The present invention relates to a sedimentation treatment device for effectively removing matter.

[0002]

2. Description of the Related Art A conventional technique for removing solid suspended solids in water to be treated is mainly one in which a flocculant is added to raw water to flocculate solid suspended solids in raw water to form flocs and settle and separate. There is a coagulation and sedimentation treatment device. However, in this coagulation sedimentation method, the sedimentation speed of floc is low, so that the processing time is long, and a large space is required for performing a large-capacity processing.

[0003] As a method of increasing the sedimentation speed of flocs and shortening the treatment time, sand, a flocculant and a polymer flocculant are added to raw water and flocculated in a flocculation tank to seed the sand. There is one that generates a floc (see, for example, JP-A-7-302637). The floc generated by this method has a large specific gravity due to the incorporation of sand, so that the sedimentation speed increases and the processing time is shortened. The floc generated by this apparatus is settled in the coagulation settling tank and is pulled out as sludge from the lower part of the settling tank.

[0004] However, in this case, the weight of the generated sludge increases, and it is necessary to reduce the volume. In addition, it costs much to supply sand. Therefore, a method has been proposed in which sand is separated and recovered from the sludge by a cyclone and reused. After collecting the sand, the sludge is discharged out of the system. The recovered sand is returned to the coagulation tank and reused.

[0005]

However, in the above-mentioned conventional method, a cyclone is used as a means for separating sand from sludge.
It is difficult to separate the sand and solid suspended matter taken into the floc-like sludge, and the solid suspended matter and flocculant may remain attached to the surface of the sand, and are reused as a seeding agent in the flocculation tank. Sometimes the cohesion performance may be reduced.

When separating sand taken in floc-like sludge from sludge, it is difficult to selectively separate and collect only sand by centrifugal force. May be mixed, and the weight of sludge may eventually increase.

There is such a problem.

[0008] An object of the present invention is to solve the above-mentioned conventional problems and to provide a purification apparatus for performing high-speed coagulation sedimentation treatment.

[0009]

According to the present invention, there is provided a purification apparatus comprising: a coagulation treatment tank for coagulating a raw water by adding a magnetic powder, a coagulant, and a polymer coagulant as a coagulation aid; A sludge blanket type sedimentation tank into which water is introduced, means for extracting sludge deposited at the lower part of the sludge blanket, a device for mechanically or hydrothermally decomposing the extracted sludge, and only magnetic powder from the decomposed sludge. It is characterized by comprising a magnetic separation device for selectively separating and collecting, and means for returning the collected magnetic powder to the flocculation tank.

In the present invention, the use of magnetic powder as a seeding agent to generate magnetic flocs having a large specific gravity increases the sedimentation speed, shortens the treatment time, and effectively separates and recovers the magnetic powder from the recovered sludge. By doing so, the magnetic powder can be reused, and high-speed coagulation precipitation can be performed efficiently.

[0011]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a magnetic separator according to an embodiment of the present invention.

FIG. 1 is a schematic system diagram of a purifying apparatus showing one embodiment of the present invention.

In FIG. 1, 1 is a flocculant, magnetic powder, pH
This is a rapid stirring tank for mixing a regulator. 2 is a rapid stirring tank 1
This is a slow stirring tank for growing a strong floc by growing a micro floc generated by adding a polymer flocculant to the micro floc. In front of the rapid stirring tank, there are provided a pH adjuster injection device 3 for adding a pH adjuster, a magnetic powder injection device for adding magnetic powder 4, and a coagulant injection device 5 for injecting a coagulant.

A polymer coagulant injection device 6 for adding a polymer coagulant is provided between the rapid stirring tank 1 and the slow stirring tank. Reference numeral 7 denotes a sludge blanket settling tank provided with a rotary rake 8. 8A is a drive mechanism for rotating the rake. Reference numeral 9 denotes a sludge decomposer that mechanically decomposes sludge that has settled and deposited at the lower part of the sedimentation tank 7. Reference numeral 10 denotes a magnetic separation device that collects magnetic powder from sludge decomposed in the decomposition device 9. Numeral 11 denotes an electromagnetic coil for generating a magnetic field in the magnetic separation device.
Reference numeral denotes a magnetic filter made of a ferromagnetic material, which is provided in a space interposed between the electromagnetic coils 11.

The procedure of the present invention will be described below.

The raw water to which the coagulant, the pH adjuster, and the magnetic powder have been added is transported to the rapid stirring tank 1 and then stirred and mixed. Here, solid suspended matter (hereinafter referred to as SS) in raw water forms flocs with magnetic powder. This floc is hereinafter referred to as a magnetic floc. This floc is small and is a micro floc that is weak against shearing force. After adding a polymer flocculant to the raw water flowing out of the rapid stirring tank 1 containing the micromagnetic flocs, the polymer flocculant is sent to the slow stirring tank 2 where a large floc resistant to shearing force is generated.

Since the specific gravity of the magnetic powder is about 5 g / cc, which is larger than the specific gravity of the organic and inorganic particles contained in the raw water, the specific gravity of the magnetic floc is larger than that of the floc containing no magnetic powder. The sedimentation velocity increases. The raw water containing the magnetic flocs is sent from the slow stirring tank 2 to the sedimentation tank 7, where it is settled and collected, and purified water is taken out as supernatant. In the lower part of the sedimentation tank 7, the rake 8 is rotated to increase the concentration efficiency of the accumulated sludge. After withdrawing the accumulated concentrated sludge, the sludge is sent to the sludge decomposing device 9. 9 is 30
This is a mixer having a rotor and a stator for rotating sludge having a rotation speed of 00 to 10000 rpm, and a rotor and a stator for grinding treatment having a clearance of 2 mm or less in the subsequent stage. In the first stage, the sludge is pulverized, and in the second stage, a grinding process is applied to separate the sludge and the magnetic powder.

The sludge decomposed in 9 is sent to a magnetic separator 10 to separate and collect magnetic powder. Reference numeral 10 denotes a hollow cylinder in which an electromagnetic coil 11 is provided, and a magnetic filter made of a ferromagnetic material is provided in a hollow portion. Since the magnetic field has a high gradient near the fine line of the magnetic filter, a strong magnetic force is generated everywhere, and only the magnetic powder is selectively recovered from the sludge that has been subjected to the decomposition treatment passing therethrough. You can do it. Sludge discharged from the magnetic separator is composted, incinerated and landfilled. After the magnetic powder is collected by the magnetic separation device 10, the magnetic powder is returned to the magnetic powder injection device and reused.

In the description of the above embodiment, the sludge decomposing apparatus is mechanically decomposed, but a sludge decomposing method by hydrothermal decomposition is also possible. Hydrothermal decomposition is a wet oxidation method performed at a subcritical temperature of 300 ° C. or lower. In the case of the supercritical treatment in which the temperature is raised to 300 ° C. or more, the magnetization of the magnetic powder, which is a ferromagnetic material, decreases due to oxidation, but continues to exhibit physical properties as a ferromagnetic material in the subcritical state. Further, if this method is used, it is possible to reduce the volume of the collected sludge such as organic matter. When the sludge is hydrolyzed, the magnetic powder and the sludge are completely separated.

In the above embodiment, the magnetic separation device is an electromagnetic magnet, but may be a superconducting magnet or a magnetic separation device using a permanent magnet.

FIG. 2 shows a magnetic powder recovery apparatus using a permanent magnet. This is a device in which a permanent magnet 14 is attached to a disk 13. As shown in FIG. 2, while rotating the disk 13, the decomposed sludge is caused to flow into contact with the magnet installation area below the disk, and the magnetic powder is adsorbed to the disk. The magnetic powder stuck to the disk is scraped off by the scraper 15 and collected in the magnetic powder collection tank.

When a method of hydrothermal decomposition is used as the sludge decomposing apparatus, a method of recovering magnetic powder by magnetic separation is not necessarily required, and a classification method utilizing specific gravity may be used.

FIG. 3 shows an example in which the above hydrothermal decomposition and the classification method are combined. The concentrated sludge collected from the settling tank 7 is sent to the hot water treatment device 17. The sludge and the magnetic powder are decomposed in the first-stage heater unit 18, and the magnetic powder separated from the sludge when sent to the second-stage heater unit is collected in the first-stage magnetic powder collection tank 19 by gravity sedimentation. . Further, sludge is further reduced in the second heater section 20. In the second-stage magnetic powder collection tank 21, the magnetic powder that cannot be collected in the first-stage magnetic powder collection tank 19 is collected. At this stage, the sludge has been completely reduced in volume.

When a magnetic field is applied so that a magnetic force is applied in the sedimentation direction during coagulation and sedimentation, the sedimentation speed can be further increased. At the same time, it is needless to say that the floc, which is an aggregate, is compacted by the force of the magnetic field, water in the gaps of the aggregate structure is released, the water content is reduced, and the volume of the sludge is reduced.

By installing a baffle plate having a labyrinth structure inside the sedimentation tank 7, the sedimentation area of the floc is increased, and the frequency of the contact of the floc is increased to promote the growth of the floc to further reduce the sedimentation. A structure that can easily make a large floc may be provided.

[0026]

According to the present invention, when the method of coagulation and sedimentation using a magnetic powder as a seed agent is adopted, the sedimentation speed is increased, the removal speed is increased, and the reuse of the magnetic powder is facilitated. Driving efficiency is improved.

[Brief description of the drawings]

FIG. 1 is a schematic system diagram showing a purification device according to an embodiment of the present invention.

FIG. 2 is a schematic perspective view showing a magnetic separation device for collecting magnetic powder.

FIG. 3 is a configuration diagram showing a magnetic powder separation and recovery device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rapid stirring tank, 2 ... Slow stirring tank, 3 ... pH adjuster injection apparatus, 4 ... Magnetic powder injection apparatus, 5 ... Coagulant injection apparatus, 6 ...
Polymer coagulant injection device, 7: sludge blanket type sedimentation tank, 8: rake, 8A: rake drive shaft, 9: sludge decomposition device, 10: magnetic separation device, 11: electromagnetic coil, 12 ...
Magnetic filter, 13 ... disk, 14 ... permanent magnet, 15
... Scraper, 16 ... Magnetic powder collection tank, 17 ... Hydrolysis device, 18 ... First stage heater, 19 ... First stage magnetic powder collection tank, 20 ... Second stage heater, 21 ... Second stage magnetic powder collection tank .

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takashi Isogami 502 Kandate-cho, Tsuchiura-city, Ibaraki Pref. Machinery Research Laboratories, Hitachi, Ltd. 4D015 BA21 BB09 BB12 CA14 DA37 DB01 EA07 EA16 EA32 FA03 FA30 4D062 BA21 BB09 BB12 CA14 DA37 DB01 EA07 EA16 EA32 FA03 FA30

Claims (1)

[Claims] 1. A flocculation tank for adding a flocculant and a magnetic powder to raw water to perform a flocculation treatment, a sludge blanket-type precipitation tank into which effluent of the flocculation tank is introduced, and a sludge under a sludge blanket in the precipitation tank. A purifying device, comprising means for extracting the sludge and transporting the sludge to a sludge decomposing device.