GB2191508A - Bipolar electrolytic cell - Google Patents

Abstract

A bipolar electrolytic cell comprises a cell housing 11 containing a row of bipolar electrodes 12, these electrodes 12 are supported one adjacent the other substantially transverse to the general flow of electrolyte liquid through the cell and such that liquid passes in succession back and forth through all the spaces between the electrodes in the row. The back and forth flow of liquid is preferably, achieved by means of a hole or holes in each electrode, the holes of successive electrodes being offset one from the other. Each electrode may be sealed by a O-ring seal 22 positioned around the outer circumferential edge of the electrode. The electrodes may be spaced by annular spacers 20. The cell eliminates problems of leakage, sealing, unreliability and inflexibility associated with prior art arrangements. <IMAGE>

Description

SPECIFICATION Improvements in and relating to a bipolar electrolytic cell The cells may, for example, be used for the electrolysis of sodium chloride solution or sea water to form sodium hypochlorite and hydrogen.

In such prior art cells, leakage and scaling have been major problems, due to the complicated arrangement of electrodes.

According to the present invention, there is provided a bipolar electrolytic cell comprising a housing, a row of spaced-apart electrodes supported in the housing at least one of which is a bipolar intermediate electrode which has an anode and a cathode integral with one another, an inlet into the housing at one end of the housing for the supply of electrolyte liquid, and an outlet from the housing at the other end of the housing for the discharge of treated liquid, liquid flowing from the inlet to the outlet in which it passes in succession back and forth through all the spaces between the electrodes in the row, in each case across the faces of the two electrodes on opposite sides of the space, the electrodes being supported in the housing substantially transverse to the general flow direction of electrolyte liquid through the cell.

The term "bipolar" is used in the art to describe an electrode which has one face which acts as an anode and an opposite face which acts as a cathode and cells containing such electrodes are termed "bipolar" cells.

Such a cell eliminates problems of leakage, scaling, unreliability and inflexibility, due to the simple and effective arrangement of the electrodes.

Preferably, the back and forth flow of liquid is achieved in the supported electrodes by means of a hole or holes being provided in each electrode, the holes of successive electrodes being offset one from the other.

Each electrode is suitably individually sealed by sealing means, which may be in the form of an O-ring seal positioned around the outer circumferential edge of the electrode.

Spacing means are preferably provided between adjacent electrodes, which may be in the form of circular and hollow spacers positioned between the circumferential edges of adjacent electrodes.

Sealing plates are advantageously provided within the cell housing at both ends of the row of electrodes, in order to fully seal the cell.

Suitably, means are provided for causing liquid to flow through the cell at a sufficient liquid flow rate, in order to prevent the cell from becoming blocked with by-product. This flow causes such by-product to be satisfactorily washed away.

The invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 shows a cross-sectional side view of a bipolar electrolytic cell in accordance with the invention, Figure 2 shows a plan view of the cell of Fig. 1, Figure 3 shows an enlarged detail of the portion circled and marked "A" in Fig. 1, and Figure 4 shows a cross-sectional side view of a further bipole electrolytic cell in accordance with the invention.

The cell 10 shown in Figs. 1 and 2 has a housing 11 containing a row of bipolar electrodes 12 each acting as an anode at one face thereof, and as a cathode at the other face thereof. Each electrode 12 is provided with a hole 18 at one side, and the electrodes are arranged one above the other such that holes 18 are provided alternatively at one side of the cell and then on the other side of the cell (i.e. diametrically opposite from each other as seen in plan).

A monopole plate 13 is provided at one end of the row of electrodes 12, and another monopole plate 15 is provided at the other end of the row of electrodes 12, the monopole plates 13 and 15 being of opposite polarity.

The electrodes 12 are supported one adjacent the other in the cell 10 substantially transverse to the general flow direction (see line A) of electrolyte liquid through the cell, and are spaced apart from each other by a circular spacer 20 (preferably made of PTFE) provided at the outer circumference thereof.

An additional spacer (not shown) may be provided along the centre line (see line B) of the row of electrodes between each adjacent two electrodes 12. The spacer 20 extends slightly outwardly from the outer edge of the electrodes 12, and each electrode 12 is individually sealed by means of an 0-ring seal 22 being provided between each outer edge of the electrode 12, two adjacent spacers 20 and the wall of the cell housing 11. The seals 22 are accordingly squashed and encased, and prevent firstly movement between adjacent electrodes, and secondly flow of eiectro lyte liquid passing around the edges of the electrodes.

At each end of the cell housing 11, there is a sealing plate 24 and rigid end plate 26 of electrically insulating material, the end plates 26 being clamped together by a connector member 28, the cell housing 11 and a number of nuts and bolts 30, in order to compress all the components of the cell together. A tube 32 is fastened to each end plate 26, and holes pass through this plate and the sealing plate 24 so that electrolyte can continuously enter or exit the tube 32 and flow in a straight line through these holes and the hole 19 in the plate 13 or 15 into or from the space between the plate 13 or 15 and the adjacent electrode 12. The electrolyte flows from the inlet through all the spaces between successive adjacent electrodes 12 one after the other (back and forth from one hole 18 on one side of the cell to the next hole 18 on the other side of the cell), finally to the outlet.

The hole 19 of the plate 15 is provided with an insulating bush 40 thereacross, to prevent blockage by electrolytic by-product.

Positive and negative electrical supply is provided by conductors 36 which pass through holes in the end and sealing plates to engage via terminal posts 42 (made from titanium or another Noble metal) the plates 13 and 15.

The electrodes 12 are preferably made from a sheet of titanium, one surface of which is provided with a thin layer of platinum. The surface of titanium acts as a cathode and the surface of platinum acts as an anode.

Eiectrolytic cells constructed as described above may be used for the production of sodium hypochlorite by electrolysis of brine solution or sea water. In particular, sea water enters through the inlet, and is caused to flow back and forth in the spaces between the electrodes 12 while electrolysing current passes thereacross, until the outlet when a mixture of water and sodium hypochlorite is left.

The cell 10 eliminates problems of leakage, scaling, unreliability and inflexibility associated with prior art arrangements. In particular, the electrodes 12 and 0-ring seals 22 ensure no leakage, eliminating the risk of hydrogen escape and danger to personnel through contact with the conducting fluid. The arrangement also causes turbulent flow between the electrodes 12 which prevents scaling salts generated by electrolysis side reactions from precipitating on and accumulating on the electrode surfaces, and reduces electrode surface polarisation to a minimum.

The simple arrangement of 0-ring seals, electrodes and spacers also allows quick and easy electrode maintenance.

The cell 50 shown in Fig. 4 is similar to the cell 10 shown in Figs. 1 to 3 except for the following specific features. The cell 50 has an integral housing member 52 suitably of polypropelene (corresponding to cell housing 11 and connector member 28 of cell 10), and an integral end plate member 54 (corresponding to sealing plate 24 and rigid end plate 26 of cell 10), whereby a nut and bolt combination 56 clamp together the housing member 52 and end plate members 54 at each end thereof.

The conductors 36 of the cell 50 meanwhile are provided with an additional seal 58 in order to obtain a double seal configuration.

Claims (9)

1. A bipolar electrolytic cell comprising a housing, a row of spaced-apart electrodes supported in the housing at least one of which is a bipolar intermediate electrode which has an anode and a cathode integral with one another, an inlet into the housing at one end of the housing for the supply of electrolyte liquid, and an outlet from the housing at the other end of the housing for the discharge of treated liquid, liquid flowing from the inlet to the outlet in which it passes in succession back and forth through all the spaces between the electrodes in the row, in each case across the faces of the two electrodes on opposite sides of the space, the electrodes being supported in the housing substantially transverse to the general flow direction of electrolyte liquid through the cell.

2. A cell as claimed in claim 1 wherein the liquid flows from the inlet to the outlet of the housing via a hole or holes provided in each electrode, the holes of successive electrodes being offset one from the other.

3. A cell as claimed in either claim 1 or 2 wherein each electrode is individually sealed by sealing means.

4. A cell as claimed in claim 3 wherein the sealing means comprises an 0-ring seal positioned around the outer circumferential edge of the electrode.

5. A cell as claimed in any preceding claim wherein spacing means are provided between adjacent electrodes.

6. A cell as claimed in claim 5 wherein the spacing means comprises circular and hollow spacers positioned between the circumferential edges of adjacent electrodes.

7. A cell as claimed in any preceding claim wherein sealing plates are provided within the cell housing at both ends of the row of electrodes.

8. A cell as claimed in any preceding claim wherein means are provided for causing liquid to flow through the cell at a sufficient liquid flow rate.

9. A bipolar electrolytic cell substantially as herein described with reference to the accompanying drawings.