GB2238795A

GB2238795A - Electrolytic cell for production of sodium hypochlorite from brine

Info

Publication number: GB2238795A
Application number: GB8927746A
Authority: GB
Inventors: Athanasios Sermbezis
Original assignee: Individual
Current assignee: Individual
Priority date: 1989-12-07
Filing date: 1989-12-07
Publication date: 1991-06-12
Anticipated expiration: 2009-12-07
Also published as: GB2238795B; GB8927746D0

Abstract

In an electrolytic cell comprising two coaxial titanium tubes 1, 2 having ends fitted into housing blocks 3 and 4, water being supplied through the inner tube and electrolyte through the annular space between the tubes, the lower housing block 4 incorporates means for adjusting the strength of the brine electrolyte comprising a water flow regulator 27 for causing a constant flow of water to operate an injector 6, brine solution being drawn by the resultant creation of a partial vacuum into the injector via port 39 from a tapered chamber 7 (Fig. 2 not shown) having a flow indicator 8 registering the brine flow entering the injector 6. The lower housing block 4 is also fitted with a flow sensing device 11 which sends a signal to energize the current supply to the cell. <IMAGE>

Description

Improvement in Electrolytic Apparatus This invention relates to electrolytic apparatus consisting of a cell such as employed for example, in the production of sodium hypochlorite from brine.

In such electrolytic cells, both electrodes are placed vertical and are usually made of titanium tubes, with one of these tubes being coated with platinum on the surface in contact with the electrolyte. In this type of cell it is important to control the velocity in which the electrolyte passes the narrow annular space between the two tubes, as this has a bearing on the amount of hypochlorite produced and on salt consumption, as salt consumption is dependent on flow through the tubes. It is also important to have a flow sensing device for monitoring the water flow through the cell as a very low flow or no flow through the cell will lead to local overheating which can damage the electrodes.

According to the present invention the electrolytic cell comprises of at least two coaxial tubes made of titanium, at least one of these two tubes being coated with platinum on the surface in contact with the electrolyte, a means of connecting said two tubes to a supply of electric current, also the inner tube passes through the top housing block where, because of the shape of this housing block part of the inner tube is exposed allowing a clamp to be secured onto the outer diameter of this tube for the supply of electric current, means of supplying cooling water through the inner tube, means of supplying electrolyte at fixed velocity to a narrow annular space between the two tubes, means of sensing the supply flow to the cell, means of making up brine solution and means of registering the brine solution.

The improved cell is particularly adapted for use in the chlorination of a water supply, water being fed to the cell from the delivery pipe-line of the water to be treated. This water passes through the inner tube for cooling, through the flow sensing device and into the flow regulator assembly, where the water is fed into an injector at fix flow rate. The conversion of water into electrolyte is been carried out by the injector.

The invention is hereinafter described with reference to the accompanying drawings, 1/2, 2/2.

The cell comprises of two titanium tubes 1 and 2 which are mounted coaxially in a vertical position, with their ends fitted into two housing blocks upper 3 and lower 4, made of transparent plastic material, such as known under the registered Trate Mark "PERSPEX". A current connector clamp 42 is attached to the outer titanium tube 1 at any convenient point in its length, also current connector clamp 43 is attached to the inner titanium tube 2 at the exposed point on the upper housing block 3. The lower housing block 4 incorporates a flow regulator assembly 27, an injector 6, a tapered chamber 7 with flow indicator 8 registering the rate of brine flow entering the injector 6, sealing o'ring 9 and screw cap 10. The lower housing block 3 is also fitted with a flow sensing device housing block 11.These housing blocks being fixed upon a supporting panel 12 by means of bolts 13, nuts 14. Housing blocks 3 and 11 are held together with four socket screws 15.

The inner tube 2 forms the cathode of the cell, while the outer tube 1, forms the anode, this is coated internally with a very thin layer of porous platinum; the inner tube 2 may also be coated with platinum, and if desired both tubes may be coated with platinum, both internally and externally.

Water from the delivery pipe-line enters the upper block 3 via inlet nipple 16 through the supporting panel 12 and through sealing o'ring 17 into the inner tube 2, this is the water supply to the cell and also acts as the cooling water. The inner tube has three sealing o'rings 18 on the upper block 3 and one on the lower block 4. The outer tube 1 has its ends engaged in shouldered recesses in the respective housing blocks, in which they are sealed by o'rings 19.

Water which flows out from the inner tube 2 enters the lower housing block 4, it flows from the lower housing block 4 through o'ring 20 and enters flow sensing housing block 11, this sensing housing block incorporates a screw cap 21, a sealing o'ring 22, a piston stop 23, a dry reed switch 24 and a magnetic piston 25. As flow is established upward through the sensing housing block 11 and continues to increase the pressure differential across the magnetic piston 25 increases until it overcomes the small piston 25 resistance (mass). The force causes the magnetic piston 25 to progress fully upward which actuates the dry reed switch 24 which sends a signal to energize the current supply to the cell.Water from the sensing housing block 11, enters the flow regulator assembly 27 which is incorporated in lower housing block 4, it comprises of a nut 26, an orifice 44, balanced control valve fitted with a rubber seat 5, two diaphragm plates 28, a rubber diaphragm 29, a spring 30, a nozzle 31 and sealing o'ring 32.

The pressure difference P1-P2 produced at the orifice 44 in the balanced control valve 5 acts on a pressure responsive element assembly ( comprising of diaphragm plates 28 and rubber diaphragm 29) and positions the balanced control valve 5 by deflecting the control spring 30. At a certain load, P1-P3, an equilibrium of forces between the diaphragm thrust and the return spring exists at the required flowrate, for example, the flow rate calculated is 500 cc per minute. If the load P1-P3 changes, the balanced control valve 5 will be moved to a new position so as to produce the necessary compensation to restore the original flowrate and retain the same P1-P2 value. The constant flow of water from the regulator assembly 27 operates the injector 6 which is incorporated in the lower housing block 4 and consists of a Venturi-type nozzle 31 and throat 45.Water enters the Venturi under high pressure and low velocity. At the neck of nozzle 31 these conditions change to those of low pressure and high velocity, creating a partial vacuum. This vacuum draws brine into the Venturi, the brine solution is sucked from a salt saturator via the nipple 33 through the supporting panel 12 and sealing o'ring 34 and into the lower housing block 4. It pass acrosses the control brine valve 35, fitted with sealing o'ring 36 and enters into the tapered chamber 7 which is incorporated into the lower housing block 4, from which the flow of brine is registerd by the float 8. To prevent this from jamming there is a float stop 37 fitted with a sealing o'ring 38.The brine solution reaches the injector 6 via port 39, which dilutes the brine to approximately 5%, prior to passing up to the annular space between the tubes 1 and 2 which form the cathode and the anode of the cell respectively and are supplied with current from a suitable source i.e. direct current, such as a rectifier.

The desired position of the control brine valve 35 i.e. to increase or decrease the concentration of brine solution can be obtained by measuring the conductivity across the electrodes, as conductivity is directly proportional to the salt concentration.

The hypochlorite solution produced finally emerges through the upper housing block 3 through the supporting panel 12 through the sealing o'ring 40 and out through the outlet nipple 41 into a storage tank for collection. Due to the cooling water being passed through the inner tube 2 the cell may be operated with a high amperage relative to its size, resulting in larger electrolytic production.

The diameter and lengths of the tubes 1 and 2 may be as desired; apparatus of different amperage may be constructed by assembling tubes of greater or less length, while using standard diameter and fittings, the housing blocks 3 and 4 being spaced apart to suit the selected length of the tubes.

If desired, more than two coaxial tubes made of titanium may be provided, the innermost tube still affording a continuous passage for the cooling fluid, while the outer tubes provide two or more annular spaces for electrolyte to flow in parallel streams around the innermost tube, forming a multipolar assembly between the outermost tube or anode and the innermost tube or cathode.

The simplicity of the cell construction, coupled with the use of transparent plastic material for the housing blocks 3,4 and 11 will permit visual inspection to be carried out at all times.

Claims

1. An electrolytic cell comprising at least two coaxial tubes

made of titanium, means of supplying cooling water through the inner tube, means of supplying electrolyte at fixed velocity to a narrow annular space between two of the tubes and means of connecting said two tubes to a supply of electric current.

2. An electrolytic cell according to claim 1, in which the ends of the tubes are fitted into two insulating housing blocks having connections for entry of cooling fluid into the inner tube and discharge of hypochlorite through the upper housing block.

3. An electrolytic cell according to claim 1, in which the ends of the tubes are fitted into two insulating housing blocks, the lower housing block incorporates an injector for the purpose of making up the brine to be electrolysed, a flow regulator, a tapered chamber with flow indicator registering the brine flow entering the injector. The lower housing block it is also fitted with a flow sensing device.

4. An electrolytic cell according to claim 2 or 3, in which the insulating housing blocks are made of transparent plastic material.

5. An electrolytic cell according to claim 2 or 3, in which the insulating housing blocks are fixed upon a support, the inner tube passes through the top housing block where, because of the shape of this housing block part, of the inner tube is exposed allowing a clamp to be secured onto the outer diameter of this tube for the supply of electric current.

6. An electrolytic cell substantially as described with reference to and as illustrated in the accompanying drawings.