JPS58153514A - Electrode assembly equipped with ion exchange membrane - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The invention is suitable for use in dewatering suspensions containing fine, previously colloidal solid particles suspended in a carrier liquid, such as kaolin suspensions. With respect to the electrode assembly, K is created by applying an electric current to the suspension by immersing it in the suspension and passing an electric current through the suspension by means of electrodes spaced apart by 91 pairs. The present invention relates to an electrode assembly for application to a vacuum dehydration method using an electric field.

A rounding method and apparatus for dehydrating S suspensions are described in Example tti.
U.S. AI% Permit No. 414a222 Oyohi No. 4,207,15
No. 8, and my U.S. patent application Ser. No. 109, filed January 4, 1980. ? It is disclosed in JS No.1. In Nire et al.'s conventional technology, the hollow self-contained electrode assembly is immersed in the suspension during normal operation, but it is designed so that it can be pulled out of the suspension at the end of the day for inspection, etc. is being done. This hollow electrode has two types of wall surfaces, namely:
It has a rounded ion permeable wall for the electrode assembly of one polarity and a liquid permeable wall for the electrode assembly of the opposite polarity.

The wall surfaces of these electrode assemblies are constructed of a permeable porous membrane with a chemically and electrically neutral filter material, which can be lined by a support grid, and a planar electrode surface. present.

In operation, a bipolar electrode assembly is immersed in a suspension, a vacuum source is connected inside the electrode assembly with the liquid permeable wall to establish a controllable pressure difference, and - across the surface. The carrier liquid is allowed to flow while the solid particles are allowed to flow through 1. It migrates in the opposite direction under the action of an electric field and is deposited as a cake on an electrode assembly having an ion-permeable wall.

The F liquid, ie, the carrier liquid from which solid particles have been removed, is extracted from the interior of the liquid-filled hollow electrode structure at a constant and controllable flow rate, such as by a pump.

As previously mentioned, cake deposition occurs on hollow electrode assemblies with ion-permeable surfaces; however, these electrode assemblies are fully saturated with electrolyte and the electrode elements are not electrolyzed. immersed in the liquid and isolated from direct contact with the suspension. As the electrolyte, one is particularly selected that has high conductivity and compatibility with the electrode element. "Compatibility" refers to the electrolyte being relatively non-corrosive under the conditions normally present within the hollow electrode assembly. Since decomposition or release products and heat are generated at the electrode element of the hollow electrode assembly, the electrolyte is allowed to flow into and through the electrode, thereby removing the foreign products and heat. The electrode chamber is flushed so that a relatively constant predetermined electrolyte composition is maintained.

The ion-permeable walls of these conventional electrode assemblies consist of a chemically and electrically neutral filter material, a permeable porous membrane. , film, or other material requiring support, it is backed by a chemically and electrically neutral grid and placed in a planar position against the slurry to be treated. Ensure that the electrode filter surface is exposed.

A cake forms on this electrode during the electrical process and is removed by contact with the doctor blade so that it does not appear unless it is dangerous.
The friction cage may be provided with spacer means to protect the filter material from direct contact with the doctor blade. - The scrubbing cage consists of a thin rod-like body made of a relatively hard material that covers the filter material so that it does not come into contact with the doctor blade. The spacer means may be formed by arranging in a frame-like configuration a plurality of strips of plastic material, such as acetal resin, of sufficient thickness to prevent contact between the doctor blade and the filter material. In order to recover the cake, the electrode assembly, with the collected solid particles or cake layer attached, can be lifted into a device consisting of a suspension. Since the electrolyte remains in the lifted electrode assembly, a vacuum is applied inside the electrode to reduce the pressure acting on the filter material and prevent the filter material from breaking. During operation, when the electrode assembly is immersed, the vacuum applied internally serves to remove gaseous products such as chlorine and carbon dioxide that are generated within the electrode element.

Conventional ion permeable electrode structures applied in the field of clay dewatering suffer from several operational problems. Since the clay particles in the feed material (suspension) are of the cotetraid size, a significant amount of clay particles will pass through the filter material.

The clay particles accumulate within the chamber of the electrode assembly and contaminate the electrolyte circulating through the electrode chamber, restricting and blocking the flow of electrolyte through the electrode chamber. Therefore, the electrode assembly must ultimately be pulled out, disassembled, cleaned, and reassembled. This is a time consuming and expensive task. Previously, it is known that the electrolyte is pumped from the chamber of the electrode assembly into the bath of JIFl liquid, but such inflow into the bath may have a negative effect on the properties of the dehydrated product. give. Therefore, there is a need for an electrode assembly that does not have these drawbacks.

Accordingly, it is an object of the present invention to provide an improved electrode assembly for performing electrofiltration.

Other objects and advantages of the invention will become more apparent from the following description, taken in conjunction with the accompanying drawings.

Briefly, an electrode assembly of the present invention for immersion in a solid particle suspension comprises a chamber having at least one wall comprising an ion exchange membrane, and a chamber disposed within the chamber for immersion in an electrolyte. and at least one electrode element.

Although referred to as a pole assembly, this electrode assembly can be a cathode for certain dehydration operations. When used as an anode assembly, a cation exchange membrane is used, and when used as a cathode assembly, a theoretical ion exchange membrane is used.

Referring to the accompanying drawings, FIG. 1 schematically shows an electrically assisted vacuum dewatering apparatus to which the present invention is directed. This dehydration device is a suspended particle bath! It has a tank 10 containing a bath 9 in which an electrode assembly 15 and a pair of cathodes 31, 52 are immersed on either side. The tank IOK is provided with a supply port connection pipe 11 for supplying suspension. The suspension is a clay suspension or a suspension in which negatively charged fine particles of colloidal size are uniformly dispersed. Inside the tank “′
i The required depth of the suspension is the overflow receptacle 4i11
50 overs 7o-rim.

12 to ensure that the electrode is fully immersed within the tank. The feed suspension is therefore fed at such a flow rate that the surplus constantly overflows the tank and the suspension in the tank is constantly metabolized. Furthermore, a connection part 14a is provided to the tank.

Since the nine-circulation pump 14 connected at 14b keeps the liquid in the tank in a constantly flowing state, particles in the suspension are appropriately dispersed, and the suspension in the tank VC is absorbed by the cathode and anode. Guarantees proper and uniform functioning of the surface.

Thus, cathode and anode surfaces in the form of planar self-contained electrode structures arranged parallel to each other are provided, each electrode structure extending vertically in its own plane to its withdrawn position from the suspension. It is configured so that it can be lifted and lowered back into suspension.

In the illustrated embodiment, ie, for suspended particles such as negatively charged clay, a hollow self-contained anode structure 15 of positive polarity is placed in the center of the tank as described above.

Vertical guide members (not shown) are provided so that the electrode structure can be pulled out of the suspension vertically in its plane, raised to the nine position, and lowered back into the liquid. (9) A rounding treatment device is provided for peeling off cakes adhering to the anode surface from the suspension during the return and lowering of the electrode structure.

As an example, these processing devices may be equipped with a 1/2-inch machine that can be oscillated between a neutral position and a cake-stripping position (around a horizontal axis).
Paired symmetrical arrangement of doctor blades 17.18 (Fig. 1)
It is shown as consisting of. The nine cakes peeled off from the electrode by this doctor blade can be carried out by a band conveyor 19.20 or the like. Of course, the cake-stripping device can also be configured to perform cake-stripping using the upward movement in which the electrode structure is lifted out of the suspension. As shown in FIGS. 2 and 3, one anode structure 15 is a hollow structure consisting of a rectangular frame member 21 and a pair of walls 22. As shown in FIGS. The wall 22 is
It consists of a membrane 22m formed of a negatively charged ion exchange resin bonded to a frame member 21. The frame member 21 is outwardly open and has a U-shaped cross-sectional shape so that an ion permeable wall can be fixed thereto. Each wall 22 has a multilayer structure consisting of a cation exchange membrane 22m, a support grid 22b, and a membrane cage 22c, and is adapted to adhere negatively charged solid particles from the suspension as a cake layer. There is.

The entire electrode structure 1s is attached to the tank 1 on the frame member 21.
0, and a pair of support brackets 15m for support are fixed.

A terminal of positive polarity in the form of a vertical rod 2.6 is arched into the interior of the hollow electrode structure 15 and connected to an electrode 27 within the structure. This rod 26 is exposed.

Attach a 26m connection cable to the top end.

Frame member 21 and wall member 22 of electrode structure 15 are electrically neutral and are therefore formed of a non-conductive material such as plastic and are insulated from electrode 27 and conductor 26.26m.

Furthermore, means for filling the inside of this electrode structure 1S with a suitable electrolyte (anolyte) is provided.

During operation of this electrically assisted vacuum filtration, the electrolyte is prepared and fresh electrolyte is passed through. The equipment for maintaining this flow of electrolyte, for example a shrimp, can be as simple as a gravity feed system.

That is, an elevated electrolyte tank (not shown) is connected to the electrode structure 15 by a supply conduit 28 and from the electrode structure by a waste conduit 29 to, for example, a waste tank (not shown). The gas generated at the anode is carried away together with the discharged electrolyte. The OiIll solution of this electrolytic solution can also be produced using a rather complicated system. The ion exchange resin membrane used in the electrode assembly of the present invention also separates the gas generated at the anode from the anolyte and injects it into the catholyte for other purposes such as pH control. It is completely permeable to mass flow of liquid. Therefore, clay particles do not flow into the anolyte chamber and contaminate the anolyte; furthermore, there is no mass flow of anolyte into the bath 9 (provided that no particles are created during the electrofiltration operation). Under the action of the generated electric field, electroosmosis occurs, causing a portion of the anolyte to flow into the solution 9. However, this phenomenon does not at least reduce the mass flow of the anolyte seen in the case of conventional membranes. (Half, and in many cases an order of magnitude less than conventional mass 7o-.) Various types of cation exchange membranes are commercially available, but
A perfluorosulfonic acid membrane sold by DuPont under the trade name "Naflon" has been found to be particularly suitable.

An electrofiltration anode assembly was modified by stretching and fixing a cation exchange membrane over one example of the anode and blinding the other side of the anode. Cation exchange membrane is
Pretreatment was carried out with N@ct at a temperature of 4a9°C for 1 hour. The feed material was a granular [5μ] clay slurry that included ammonium polyacrylate as a dispersant. The dehydration operation is
When the test was carried out under the following conditions for approximately 4 hours, a relatively constant filtrate flow rate (dehydration rate) was observed.

Table 1 8:20 6Q 6.0 911
Start 8:55 60 40? ”
51℃ 1010crAO min 9:255846
9” 57℃ 10:0560 table o” b” !$7℃10:5560
40 7" 40℃ 11:10 59 42 8"
45℃ 11:50
1000ct AO minute 11:40 6G
&4 45" 41.5 se 12: End of QO The following table ■ shows I) Hs conductivity and solid particle content (A) regarding the voice supply liquid, P liquid, bath, and cake in the dehydration operation of keratin. ing.

Supply liquid 8:00 a5 2,700
515F liquid 10:45122 6JOO-bath 11:159.1 2J00 557 cake 11:1
0 &9° 710” 7!
LO bath 11:409.2 2,700 5lhOF 1
1 [11:40 112 S, 950
-Cake 11:40-
74.0 Anolyte 12:50 13 117
,000 - *The cake was resuspended using deionized water to a solids content of 13%.

The conductivity of the bath during this test (2700-2800 m m
ho/cmi) and the conductivity of the anolyte (117,000 m
mho/cm), it can be seen that the cation exchange membrane eliminates the ingress of anolyte into the bath.

In the case of dewatering a slurry with a particle size of 5μ containing ammonium polyacrylate as a dispersant, the performance of the nine anode assembly equipped with a cation exchange membrane (Nafion; trade name) and the conventional ion permeation l [(Dinel) The results of a comparison of the performance of anode assemblies with (trade name) are given in Table IK below.

Table l Conventional membrane Cation exchange membrane temperature 25.5°C 41.5°C Feed liquid Solid particles (IL weight) 34J 56.8 Conductivity (rnmho cm-” 2700 27
00oHas &5 Throughput Solids (ton Δhr) 9876 amp 2.75
574 liquids (gallons/hour) 1.42
0 1930P liquid solid particles (wt%) α0 αO
pH 11512,2 Flow rate (gallons/hour) 9874 p 940 124
0 Solid product solid particles (wt%) 75 7 Hair 5
Flow rate (ton/hour) 2.75 at 9874 amp
A74 bath solid particles (wt%) 3 & 0 5 straight O
pH9,49,2 Electrical conductivity (m who cm') 2690
2700DC Required amount of product (Kwh/) 7 solids) 156 1
58F liquid (Kwh/I+-o gallon) 458
From the data shown in Table 468, it can be said that the performance of the cation exchange membrane according to the present invention is comparable to that of conventional membranes. Although the solid product production rate using cation exchange membranes is higher than with conventional membranes, this difference is believed to be primarily due to the difference in operating temperature. However, when using the membrane of the present invention, the inflow of clay particles into the electrode assembly does not occur, whereas in the case of conventional membranes the influx of clay particles into the electrode assembly is unavoidable. l!
Furthermore, in contrast to the loss of anolyte caused by penetration of the anolyte into the cake when using conventional membranes, in the present invention, no penetration of the anolyte into the cake occurs.

Although the preferred embodiments of the present invention have been described above, the present invention is not limited thereto, and various modifications can be made within the scope of the present invention.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an electric voltage passing device incorporating the electrode assembly of the present invention, and FIG. 2 is a detailed diagram of the electrode assembly of the present invention.
FIG. 5 is a cross-sectional view taken along line 5--3 in FIG. 2. In the figure, 15 is an electrode assembly, 21 is a frame member, 22 is a wall, and 22a is an ion exchange membrane.

Claims (1)

Claims: 1) An electrode assembly for electrically assisted vacuum passing of a suspension of solid particles suspended in a carrier liquid, comprising: an electrically conductive frame structure; a means for circulating an electrolyte having a high electrical conductivity through the electrode chamber; and a means for circulating an electrolyte having a high conductivity through the electrode chamber; an electrode assembly comprising: at least one electrode element connected to each other; and at least 41 of said walls containing an ion exchange membrane. 2) The electrode assembly according to claim 1, wherein the solid particle suspension*a clay slurry is used to make the electrical connection line electrode assembly an anode. 5) The electrode assembly according to claim 1 or 2, wherein the ion exchange membrane is a cation exchange membrane. 4) The electrode assembly according to claim 1 or 2, wherein the ion exchange membrane is made of a perfluoro-sulfonic acid polymer. 5) The electrode assembly of claim 1, wherein the solid particle suspension is a clay slurry and the electrical connection is adapted to make the electrode assembly a cathode. 6) The electrode assembly according to claim 1, wherein the ion exchange membrane is an anionic/exchange membrane.