JPH1157724A - Electrolytic flocculator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease the frequency in exchanging electrode by using an electrode having a shape different from that of the conventional one and to perform flocculation with high efficiency. SOLUTION: The fine grains in a liq. are electrolytically flocculated. The flocculator consists of a couple of electrodes 8 and 9 at least one of which consists of electrically corrosive metallic thin sheet of aluminum, iron or their alloy and which are spiraled and an insulating material and is provided with a reticular spacer 10 for interposing between the electrodes at a specified distance and spiraled like the electrodes and a means for letting the liq. pass between the electrodes in the axial direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for aggregating fine particles in a liquid by an electrolytic reaction, and more particularly to a method for producing scale-forming substances such as suspended solids, colloid components, oil emulsions, and dissolved silica in water purification and drainage facilities. It can be suitably used in the aggregation treatment step.

[0002]

2. Description of the Related Art Most of fine particles such as suspended solids and colloid components in a liquid to be treated are negatively charged and hardly aggregate. Therefore, as a means to coagulate and facilitate separation and removal,
An electrolytic coagulation method in which aluminum, iron, or an alloy thereof is immersed in a liquid to be treated as an anode to perform an electrolytic reaction is generally known.

[0003] The mechanism of aggregation will be described with reference to an example in which aluminum is used as the anode. When a voltage higher than the theoretical decomposition voltage of aluminum is applied, aluminum is ionized and melts from the anode. The aluminum ions are hydrolyzed and polymerized to produce polymerized aluminum ions having positive charges and aluminum hydroxide. And
It is believed that they combine with the negatively charged fine particles to form an uncharged complex and aggregate. The amount of aluminum added needs to be adjusted according to the type and concentration of the fine particles to be aggregated, but can be easily calculated according to Faraday's law. When iron is used as the anode, the principle is the same as that for aluminum except that the polymer iron ion and iron hydroxide have a positive charge.

[0004] The structure of an electrolysis apparatus is most generally one in which a plurality of flat-plate-shaped electrodes are alternately arranged on the positive and negative sides. In addition, another type in which a plurality of cylindrical electrode pairs are arranged in an electrolytic cell and set up is proposed. (Japanese Unexamined Patent Publication No. Hei 6-343972).

In the electrolytic coagulation method, it is important not only to improve the coagulation efficiency but also to extend the electrode life. This is because the anode is gradually consumed inevitably as the process proceeds in principle of the electrolytic coagulation method. That is, the electrode which has been consumed to some extent needs to be replaced because the electric resistance increases and the elution amount of the metal ion decreases, so that the electrolytic efficiency decreases. In general, the replacement operation requires labor and sometimes the coagulation process needs to be temporarily stopped, which is inconvenient especially in continuous processing. Therefore, in order to reduce the frequency of replacement, both the positive and negative electrodes are made of the same electrolytic corrosion metal, and the operation is performed while intermittently inverting the polarity to extend the life of the electrodes.

[0006]

The method of operating while reversing the polarity has no room for further improvement as a means for extending the life of the electrode. On the other hand, as means for extending the life of the electrode, it is conceivable to increase the packing density of the electrode in the electrolytic cell in addition to reversing the polarity.

However, in the conventional electrolytic agglomeration apparatus, the packing density is merely increased in an arrangement range that is possible in a known electrode shape such as the above-mentioned flat electrode or cylindrical electrode pair.
In addition, in order to increase the aggregation efficiency, it is necessary to efficiently stir and mix the metal ion or its hydroxide with the aggregation target in a short time.

However, in the conventional method, it is not sufficient because the stirring is only performed by the bubbles of the hydrogen gas generated by the electrolytic reaction from the electrodes. Therefore, an object of the present invention is to provide an electrolytic coagulation apparatus capable of performing an agglomeration treatment with high efficiency by reducing the frequency of electrode replacement with an electrode shape different from the conventional one.

[0009]

In order to achieve the object, an electrocoagulation apparatus of the present invention is an apparatus for coagulating fine particles in a liquid by performing an electrolytic reaction, at least one of which is made of aluminum, iron, A pair of spirally wound electrodes made of a thin metal plate of electrolytic corrosion such as an alloy of
It is characterized by comprising a mesh-like spacer which is made of an insulating material and is spirally wound between the electrodes similarly to the electrodes to determine the electrode interval, and means for regulating the liquid so as to pass in the axial direction between the electrodes.

According to the present invention, the electrodes and spacers are spirally wound and filled with the spacers keeping the distance between the electrodes uniformly narrow, so that the packing density of the electrodes can be increased. Therefore, power consumption can be saved and the frequency of electrode replacement can be reduced. In addition, since the liquid to be treated advances in the axial direction between the electrodes through the mesh while colliding with the spacer, the metal ions or the hydroxide thereof and the aggregated object are sufficiently stirred. Therefore, the metal ions and the hydroxides thereof generated by the electrolytic reaction are thoroughly combined with the aggregation target to form aggregated flocs which are easily separated.

Preferably, the electrode pair is made of a galvanic metal of the same quality in order to prevent only one of the electrodes from being consumed unevenly. The power source may be either AC or DC, but when it is DC, it is preferable to connect it to a power source so that the polarity of the electrodes can be intermittently reversed.

[0012]

Embodiments of the present invention will be described with reference to the drawings. 1 is a partially cutaway perspective view showing an electrolytic coagulation apparatus, FIG. 2 is a perspective view showing an expanded state of an electrode element, FIG. 3 is an end view of the electrode element, FIG. 4 is a plan view of a spacer, and FIG. It is 5-5 sectional drawing.

The electrolytic flocculation apparatus 20 includes a cylindrical container 1,
It comprises an electrode element 2 housed in this and spirally wound. The electrode element 2 is made of a hard plastic and has a central tube 3 closed at one end, conductive wires 4 and 5, and a thickness of 0.2 to 1 piece.
A pair of electrodes 8 made of an electrolytic corrosion metal sheet of about 1 mm,
9. Plastic mesh spacer 10 and PP or P
It is composed of a plastic insulating sheet 11 such as E. The central tube 3 is provided with a not-shown conducting wire through hole at an intermediate portion in the axial direction.

The method of manufacturing the electrode element 2 is generally as follows. However, each procedure may be appropriately changed.
One end of each of the conductors is passed through conductors 4 and 5, one end of which is connected to each of the electrodes 8 and 9, and the other end is guided to the open end of the central tube 3. The conductor through-hole is liquid-tightly sealed with a sealing material such as silicon rubber while passing the conductor. Spacer 10 between electrodes 8 and 9
, The insulating sheet 11 is superimposed on the outside of the electrode 9 and wound around the central tube 3. The electrode 8 and the electrode 9 of the same turn are interposed between the electrode 9 and the electrode 8 of the next turn by the interposition of the spacer 10.
The short circuit is prevented by the interposition of the insulating sheet 11.
As shown in FIG. 3, the gap portions a and b at the beginning and end of the winding are sealed with resin so that the supply liquid does not pass through a space other than between the electrodes. Thus, the electrode element 2 is completed.

The inner diameter of the container 1 is slightly larger than the outer diameter of the electrode element 2, and a raw water inlet 6 is provided at a lower end and a treated water outlet 7 is provided at an upper end. The electrode element 2 is inserted into the container 1 with the open end of the central tube 3 facing upward, with the circular packing 12 being fitted therein. Then, the container 1 is closed so that only the open ends of the conductive wires 4 and 5 and the center tube 3 are exposed. Since the spacing between the electrodes can be uniformly reduced by the spacer 10, the packing density of the electrodes is improved, which leads to a reduction in power consumption and a reduction in the frequency of electrode replacement.

In the apparatus 20, raw water is supplied from the raw water inlet 6, is put into the container 1, and spreads at a stretch to the lower end surface of the electrode element 2. Conductors 4 and 5 are connected to electrodes 8 and 9
Energize more. Then, the raw water proceeds between the electrode 8 and the electrode 9 in the axial direction while passing through the mesh of the spacer 10. Raw water is electrolyzed during the process, and the spacer 1
The mixture collides with 0 and is stirred and mixed. For this reason, the fine particles floating in the raw water combine with the metal ions and the hydroxides thereof generated by the electrolysis to form aggregated flocs, and emerge as treated water from the upper end surface of the electrode element 2. Treated water is treated water outlet 7
It is sent to a solid-liquid separation device.

The spacer 10 will be described in detail. As shown in FIGS. 4 and 5, the spacer 10 has a large number of plastic wires intersecting three-dimensionally and welded at the intersections to form a square mesh. However, the shape of the mesh is arbitrary such as a rhombus and a parallelogram. In short, because of the three-dimensionally crossed shape, the flow resistance is small, but the turbulence is promoted, and the supply liquid is sufficiently stirred. In addition, since the distance between the electrodes is kept constant by the spacer 10, a uniform current can be passed, and efficient electrolysis can be performed. The material of the spacer 10 may be a general-purpose plastic that does not conduct electricity, such as PP and PE. As the size, thickness d = 0.5 to 5 mm, pitch p = 2 to 30 m
What is necessary is just to select the thing of about m according to liquid quality. For example,
When the stock solution contains a large amount of silica scale, a thick solution having a large pitch is used to prevent clogging of the spacer.

The current supply method may be either AC or DC. However, when a DC power supply is used, the polarity is intermittently inverted for the purpose of evenly consuming both electrodes and cleaning the electrodes. Although the shape of the container is not limited, an upward flow type is preferable in order to easily discharge hydrogen gas generated by electrolysis.

[0019]

【Example】

-Example-A test cell 30 shown in Fig. 6 was manufactured as an electrolytic aggregation device. The test cell 30 includes a convex mold 13 and a concave mold 14 fitted to each other, and a pair of plate-like electrodes 15, 1 fixed between the molds.
6 and a spacer 17 interposed between the electrodes. The fitting gap around the electrodes 15 and 16 is sealed from outside with an O-ring 18 in a liquid-tight manner. The convex mold 13 includes a supply hole 21 for guiding raw water supplied from a raw water supply pipe 19 to a fitting gap surrounded by an O-ring 18, a water intake hole 22 for guiding treated water to the outside, and electrodes 15 and 16. Terminals 23 and 24 for connecting to a substantially external power supply are provided.

Using this test cell 30, 50 ppm
Of silica-containing groundwater was performed under the following conditions. Sampling of the treated water was performed 10 minutes after being taken out from the water intake hole 22 and stored in the water storage tank 25. Silica concentration is measured by HACH silica measurement kit SI
It measured using -5. As a result, the dissolved silica concentration in the treated water was 27 ppm.

[Conditions] Electrode material: Aluminum Electrode size: 4 × 7 mm (28 cm ² ) Voltage: DC 16 V Current: 0.21 A Electrode spacing: 2.5 mm Spacer: 2 mm pitch, 1.2 mm thick grid Temperature: Room temperature Water supply: 100 mL / min

Comparative Example Unlike the test cell 30, an electrode was fixed in a beaker without a spacer. The same groundwater as in the example was poured into the beaker, and desiliconization was performed under the following conditions. Sampling of the treated water and measurement of the silica concentration were performed in the same manner as in the examples. As a result, the concentration of dissolved silica in the treated water was 38 ppm.

[Conditions] Electrode material: Aluminum Electrode size: 4 × 7 mm (28 cm ² ) Voltage: 16 V DC Current: 0.21 A Electrode interval: 5 mm Beaker capacity: 420 mL Temperature: Room temperature Supply water amount: 100 mL / min

[0024]

As described above, according to the present invention, since the packing density of the electrodes is high, the frequency of electrode replacement can be reduced. In addition, since the liquid is rapidly stirred while passing between the electrodes, the aggregation efficiency is good. Therefore, the electrolytic aggregation treatment can be performed efficiently.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing an electrolytic aggregation device according to an embodiment.

FIG. 2 is a perspective view showing an expanded state of an electrode element used in the embodiment.

FIG. 3 is an end view of the same electrode element.

FIG. 4 is a plan view of the spacer.

FIG. 5 is a sectional view taken along line 5-5 of FIG. 4;

FIG. 6 is a cross-sectional view illustrating a test cell according to an example.

[Explanation of symbols]

 Reference Signs List 20 electrolytic flocculation apparatus 1 container 2 electrode element 3 central tube 4, 5 conductor 6 raw water inlet 7 treated water outlet 8, 9, 15, 16 electrode 10, 17 spacer 11 insulating sheet 12 circular packing 30 test cell

Claims (3)

[Claims] An apparatus for agglomerating fine particles in a liquid by performing an electrolytic reaction, wherein at least one of the pair of electrodes is made of an electrolytically corrosion-resistant metal thin plate such as aluminum, iron, or an alloy thereof, and has a pair of spirally wound electrodes. It is characterized by comprising a mesh-like spacer which is made of an insulating material and is spirally wound between the electrodes in the same manner as the electrodes to determine the electrode interval, and means for regulating the liquid so as to pass in the axial direction between the electrodes. Electrolytic coagulation equipment. 2. The electrode pair is connected to a DC power supply capable of intermittently reversing the polarity of the electrodes.
An apparatus according to claim 1. 3. The apparatus according to claim 1, wherein said pair of electrodes are connected to an AC power supply.