US3574073A

US3574073A - Method for adjusting electrodes

Info

Publication number: US3574073A
Application number: US757437A
Authority: US
Inventors: Richard W Ralston Jr
Original assignee: Olin Corp
Current assignee: Olin Corp
Priority date: 1968-09-04
Filing date: 1968-09-04
Publication date: 1971-04-06
Anticipated expiration: 1988-04-06
Also published as: DE1944051A1; DE1944051B2; GB1233679A; FR2017393A1; JPS4825319B1

Abstract

ANODES ARE ADJUSTED IN A MERCURY CATHODE ELECTROLYTIC CELL USING HYDRAULIC MEANS FOR RAISING AND LOWERING THE ANODES WHERE THE HYDRAULIC MEANS IS ACTUATED (1) BY USING THE CHANGES IN FLUX OF THE MAGNETIC FIELD GENERATED BY THE ELECTRICAL FLOW IN THE CONDUCTORS SUPPLYING THE ANODES TO PREVENT OR CORRECT SHORT CIRCUITS AND (2) ELECTRICALLY CONTROLLING THE OPERATION OF THE HYDRAULIC SYSTEM.

Description

April 1971 R. w. RALSTON, JR 3,574,073

METHOD FOR ADJ USTING ELECTRODES Filed Sept. 4, 1968 I 2 Sheets-Sheet 1 INVENTOR RICHARD mmLsrom United States Patent O-fiice 3,574,073 Patented Apr. 6, 1971 3,574,073 METHGD FOR ADJUSTING ELECTRODES Richard W. Ralston, In, Cleveland, Tenn, assignor to Olin (Zorporation Fiied Sept. 4, 1968, Ser. No. 757,437 Int. Cl. C0141 1/14; B011; 3/00 U.S. Cl. 20499 8 Claims ABSTRACT OF THE DISCLOSURE This invention relates to an improved method of adjusting the elevation of anodes in cells for the electrolysis of aqueous solutions. More particularly the invention relates to a new method for the adjustment of the elevation of anodes in horizontal mercury cells. In another aspect, the method of this invention provides means for detecting current overloads and for automatically adjusting the anodes to correct and prevent short circuits between anodes and cathodes. This invention is particularly applicable to cells of the type described in US. Pats. 3,140,991 and 3,390,070 but the use of the method of this invention for anode elevation in other cells is also included within the scope of this invention.

Horizontal mercury cells usually consist of a covered elongated trough sloping slightly towards one end. The cathode is a flowing layer of mercury which is introduced at the higher end of the cell and flows along the bottom of the cell toward the lower end. The anodes are generally composed of rectangular blocks of graphite suspended from conductive lead-ins, for example, graphite or protected copper tubes or rods. The bottoms of the graphite anodes are spaced a short distance above the flowing mercury cathode.

In cells of this type, the distance between the graphite anodes and the mercury cathode is very important. This inter-electrode distance should be as small as possible to reduce the wasteful consumption of energy, for example, in the production of heat. However, if this distance is too small, secondary reactions take place, particularly the direct attack on sodium amalgam by chlorine bubbles. This distance is ordinarily maintained, if possible in the range of to inch, preferably about /8 to 7 inch.

In operation, the graphite anodes are consumed thereby increasing the distance between the anodes and cathode and resulting in reduced energy efiiciency. Graphite consumption of the anodes nearer the inlet end of the cell is less than at the outlet end of the cell. To maintain the proper distance between the anodes and cathode, it is necessary to adjust the elevation of the anodes from time to time. In most types of prior art apparatus it is necessary to adjust each anode individually. Adjustment of anodes individually would not be required solely because of graphite consumption since one group of anodes in a cross section of the cell usually are consumed at approximately the same rate. US. Pat. 3,140,991 provides for adjustment of a group of anodes arranged in a single cross section of the cell. US. Pat. 3,390,070 provides a mechanism for adjustment of a larger subgroup of anodes in such a cell.

Further problems arise in the operation of mercury cells with graphite anodes where short circuits occur. These may be caused by breakage of graphite, by loosening of anode supporting posts, by changes in the thickness of the mercury due to islands of thick mercury or faulty flow control or other causes which allow the graphite anode to contact the fiowing mercury cathode. The resulting short circuit causes an excessive flow of current in the anode and in the bus serving that anode, overheating of anode leads and of lead buttons when used in connecting graphite anodes to leads, loss of production of chlorine, excessive hydrogen in the chlorine and other problems.

Anodes of materials other than graphite also are suitable in mercury cathode cells, particularly titanium anodes having a thin coating over at least part of their surface of a platinum metal or oxide. The method of this invention is equally applicable to the adjustment of such anodes and this is particularly important since any short circuit rapidly removes the coating and this loss of a platinum metal or oxide cannot be economically tolerated. By the term platinum metal in the present specification and claims is means an element of the group consisting of ruthenium, rhodium, palladium, osmium, iridium and platinum or alloys of two or more of these metals. The term titanium is meant to include alloys consisting essentially of titanium.

One of the objects of this invention is to provide an improved method for adjusting the elevation of the anodes in a mercury cathode cell.

Another object of this invention is to provide for the improved adjustment of sub-groups of anodes in a mer cury cathode cell.

Another object of this invention is to provide a method for correcting and preventing short circuits in mercuury cells.

Other objects and advantages of this invention will appear in the course of the following description.

The method of this invention is particularly applicable to the structure defined in US. Pat. 3,390,070 providing endless, flexible drive means engaging a plurality of wheels which are adapted to raise or lower a sub-group of anodes in a mercury cell. The method of this invention is also applicable to control hydraulic means for adjusting anodes by other mechanical means.

The method of this invention comprises electrically controlling (l) intermittent flow of a control fluid and (2) the direction of said flow to one of a plurality of fluid-activated rotary adjustment means, each adapted for separately adjusting the elevation of a sub-group of said plurality of anodes above said cathode. In one aspect of this invention for automatic preventation of short circuits, the intermittent flow is controlled by providing a first electrical circuit interruptable in response to changes in the flux of the magnetic field generated by electrical flow in a conductor supplying said subgroup of anodes above said cathode. In a second aspect of this invention for manual adjustment of anodes, intermittent fiow is controlled (l) by providing a manually interruptable, selective second electrical circuit and selectively closing said second circuit to initiate said intermitttent flow to a selected one of said plurality of adjustment means and (2) the direction of said intermittent flow is controlled by manually closing a third electrical circuit when it is desired to decrease the elevation of the sub-group of anodes dependent on said selected adjustment means, thereby reversing the direction of said intermittent flow.

The accompanying figures show one suitable hydraulic and electrical system according to this invention. FIG. 1 shows the mechanical features of a suitable system with connections to the hydraulic and electrical systems. FIG. 1A shows detail of mounting of each reed switch. FIG. 2 shows a suitable hydraulic system for producing the desired flow in the hydraulic lines shown in FIG. 1 together 9 a with connections to the electrical system. FIG. 3 shows the electrical system for controlling movement of the anodes and for measuring voltage drop in the conductors carrying current to the anodes and includes associated parts of the hydraulic system.

FIG. 1 shows a section of a mercury cathode chloralkali cell similar to that shown in US. Pat. 3,390,070 issued June 25, 1968 including the chain drive means 111 connecting four jacking screws 114 which support two channels 112 each in turn supporting five anodes 113 and in turn supported on jacking screws 114 resting on cover 115. Each anode is supported by posts 116, one in one channel and one in an adjoining channel. FIG. 1 further shows hydraulic motor 121 connected by branch hydraulic lines 122 and 123 to main

hydraulic lines

124 and 125 respectively. Hydraulic fluid in

main lines

124 and 125 flows to and from hydraulic motor 121 via lines 122 and 123 when solenoid valve 126 is in the open position. Hydraulic pressure is maintained in one or the other of

main lines

124 and 125 depending on the position of a four-way valve 220 shown in FIG. 2. Solenoid Valve 126 is maintained in the closed position until it is opened by the solenoid actuated by current flowing in conductors 311 shown also in FIG. 3. One valve 126 and one motor 121 is provided for each pair of channels 112.

Each channel 112 carries at one end a flexible connector 128 which is an extension of bus 129 which carries current to the anodes. A reed switch 329 is mounted on the surface of bus 129 and is connected by

leads

312A and 312B to the electrical control system.

FIG. 1A shows the detail of mounting of the reed switch 329 enclosed in iron pipe 117 and clamped to bus 129 by means of clamp 18. The reed switch is an encapsulated magnetic switch that is actuated by the magnetic field generated by the electrical flow in the bus. The reed switches are mounted in steel pipe which are clamped against the bus to provide suitable shielding for this service. The reed switch is most sensitive when perpendicular to the length of the bus bar and it will not operate when parallel with the bus bar. The angle of the switch to the length of the bus is adjusted to cause the switch to close under the influence of a magnetic field of any desired strength, corresponding to any desired flow of current in the bus.

FIG. 2 shows the hydraulic system for operating the hydraulic motors 121 shown in FIG. 1. Tank 211 contains a suitable hydraulic fluid at atmospheric pressure which is transferred by pump 212 through check valve 213 in line 214. Accumulator 215 is connected to line 214 to provide reserve capacity. Pressure switch 216 is also provided in line 214 to maintain a selected pressure in line 214, suitably 1000 p.s.i. At higher pressures switch 216 operates solenoid valve 217 to pass hydraulic fluid from line 214 via relief line 128 to return line 219. Electrical supply lines 318, suitably of 110 v. AC is provided for operation of pressure switch 216 and solenoid 217.

Hydraulic fluid at any suitable pressure in line 214 is transmitted to operate hydraulic motors 121. The direction of flow and therefore direction of rotation of motors 121 to raise or lower the anodes is controlled by fourway valves 220 (two shown). Shut-01f valves 221 permit isolation of hydraulic lines serving any one cell from the rest of the system for use in case of leakage or repairs. When valve 220 is in the position shown in FIG. 2, the flow in

lines

124 and 125 serves to rotate the motors in one direction and to raise the anodes. When valve 220 is in the reverse position, anodes are lowered by rotation of the motor in the opposite direction. The position of valve 220 is controlled by attached solenoid 222 actuated as described in connection with FIG. 3. Flow controller 223 provided in line 124 automatically transmits hydraulic pressure to line 124 when that line is the pressurized line. Flow controller 224, provided in line 125 then permits flow at atmospheric pressure in line 125 which is the return line. When four-way valve 220 is reverse, line 125 is the pressurized line and controller 224 transmits hydraulic pressure therein. Controller 223 in line 124 then permits flow at atmospheric pressure. These adjustable flow controllers thus control the flow and provide consistent motor speeds in one direction while allowing free flow of hydraulic flow to atmospheric pressure in the opposite direction.

Flexible connections 225, suitably with quick-detachable fittings, are provided in

lines

124 and 125 to facilitate separation of the hydraulic supply system from

lines

124 and 125 which are suitably mounted on the cell cover when it is necessary to remove the cell cover from the cell.

In the hydraulic system the motors are operated at any convenient speed, for example, 40 r.p.m. Suitable hydraulic motors are commercially available for low speed operation using hydraulic pressures from 100 to 5000 p.s.i. but generally pressures from 500 to 1000 p.s.i. are preferred and especially pressures in the 500 to 600 p.s.i. range. The jacking nuts turned by the motors then move at 20 r.p.m. and are adjustable to about of a turn corresponding to 0.01 inch in the elevation of the anodes.

To avoid electrical hazard, hose connections in the hydraulic system are preferably non-conducting. Quick disconnecting joints are advantageous for electrically isolating the hydraulic lines and valves on the cell from the hydraulic supply system and to facilitate removal of the cell cover.

One central hydraulic supply system is sufficient for an entire cell room. Different motor speeds are suitably used, when desired, to lower the anodes more slowly and to raise the anodes more rapidly. Flow control valves for this purpose are known to the art.

Normally all the motors are shut 011 and each is independently operated by opening manually or automatically the valve to that motor.

Hydraulic lines are any suitable hydraulic tubing, for example, of steel and are advantageously inch in diameter but suitably range from A to /2 inch.

Hydraulic lines

124 and 125 run the length of a cell and are closed at the ends distant from the hydraulic pump.

Oil is the preferred hydraulic fluid since it is reasonable in price, it is electrically non-conducting and it is usually non-corrosive. Water is also a suitable hydraulic fluid but a leak-free system is more diflicult to maintain, it is frequently electrically conductive and it is also frequently corrosive. Air is also a suitable fluid for power transmission and has the advantage that air-operated motors can discharge into the atmosphere and no fluid return system is required. In addition, air motors suitably operate at pressures of 100 p.s.i. or lower. However, they operate most reliably at high speeds and then must be geare to produce low speeds. The oil operated motors operate satisfactorily at low speeds and produce high torque without the necessity of gear reduction. They are preferred because they are simpler and operate reliably, cheaply and safely at low speeds.

Systems using electric motors have been proposed but electric motors are inherently considerably more expensive and require more intricate control systems.

FIG. 3 shows the electrical system for operating fourway valve 220 and solenoid valve 126. The four-way valve 220 controls the direction of flow of the hydraulic [fluid and each solenoid valve 126 activates one hydraulic motor. One four-way valve 220 is provided per cell and one solenoid valve 126 is provided for each motor.

Transformer 313 is supplied with '115 v. AC current which is reduced to a more suitable voltage, conveniently 24 volts. The transformer is suitably of the dry or oilfilled type but any satisfactory transformer is usable provided it supplies adequate current to operate the 24 v. DC circuits. One AC lead is directly connected to transformer 313 and the other lead is controlled by double pole, double throw (DPDT) switch 314, one pole of which, in either of its two closed positions, completes the circuit to transformer 313. The other pole of switch 314- in one position closes the 24-volt circuit for automatic operation and in its other position opens the 24-volt circuit for manual operation when necessary.

The 24-volt current from transformer 313 is rectified in rectifier 315. One lead of the 24 v. DC is connected directly to each of solenoid valves 126 which control the flow of hydraulic fluid to the hydraulic motors 121. The other 24 v. DC lead supplies one pole of DPDT switches 314 and 316. DPDT switch 316 is of the center-off, momentary contact type which is closed only when manually held. When DPDT switch 316 is closed in either position, one pole closes the 24 v. DC circuit to rotary switch 317. The other pole of DPDT switch 316 in one position closes the 115 v. AC circuit to solenoid 222 of four-way valve 220 and reverses the direction of flow of hydraulic fluid in

lines

124 and 125, reversing the direction of rotation of motor 121 and lowering instead of raising the anodes. Normally four-way valve 220 is in position to cause raising of the anodes unless activated through switch 316 to lower the anodes. Four-way valves operated by solenoids designed for 24 v. DC are also suitable for this purpose.

The 24 v. DC circuit is completed through leads 312A and 31213 to reed switches 329 and solenoid Valve 126 with signal lamp 317A in parallel therewith. When DPDT switch 314 is closed for automatic operation, 24 v. DC current is supplied to reed switches 329, solenoid valve 126 and lamp 317A. When either of reed switches 329 shown in FIG. 3 closes, solenoid valve 126 is activated to raise one group of anodes and to light signal lamp 317A to indicate the location of the closed reed switch. When anodes are raised sufliciently the reed switch opens, anode motion stops and the signal lamp goes out.

In FIG. 3, manual adjustment of anodes is provided for by reversing DPDT switch 314 to supply 115 v. AC to transformer 313 by interrupting the 24 v. DC circuit through the reed switches. Manual adjustment of anodes according to the following description proceeds, however, even though DPDT switch 314 is not reversed since manual operation provides a closed circuit to solenoid valve 126 even though the circuit via the reed switches is open. Closing DPDT switch 316 in one direction leaves the 115 v. AC circuit to four-way valve 220 open but closes the 24 v. DC circuit through rotary switch 317. By means of the latter switch 317, it is possible to select and open any solenoid valve 126 and to raise one group of anodes while reed switches 329 are inactive or inactivated. Operation of the motor 121 controlled by solenoid valve 126 to raise the group of anodes continues until DPDT switch 316 is released to its center-off position. Closing DPDT switch 3-16 in the opposite direction additionally activates four-way valve 220 and results in lowering the same group of anodes.

FIG. 3 further shows the system for monitoring the voltage drop in the bus bars supplying current to the anodes and is used in conjunction with manual adjust ment of the anodes.

Rotary switches

411 and 412 are mounted on the same shaft 417 as rotary switch 317.

Switches

411 and 412 close the circuit to selected

contacts

413 and 414 spaced along one selected bus 129. Two contacts are arranged at a suitable distance apart, for example 36 inches, on each bus. Advantageously, the contacts are spaced apart as far as possible for maximum sensitivity and accuracy but a section of bus is preferably selected which is free from joints, connections or other features giving rise to disturbed or variable magnetic patterns. The greatest accuracy is thus obtained. The IR drop between any such pair of contacts is indicated on

millivolt meter

415 or 416. The IR drop for a normally operating cell with properly adjusted anodes is known. Observation of the millivolt meter reading while manually raising or lowering a group of anodes, permits adjustment of the anodes t the proper spacing.

In operation, the method of this invention provides for remote manual adjustment either by raising or lowering the anodes and for automatically raising of any set of anodes at any time in case of electrical overload, for example, by short circuit.

For manual adjustment of anodes, any desired group of anodes suspended from an adjoining pair of channels is selected for monitoring and manual adjustment by rotating rotary selector switch 317 to the desired position. In addition, the two rotary selector switches 411 and 412 are rotated to indicate on

millivolt meters

415 and 416 the IR drop in the two adjoining buses feeding current to the anodes in the group selected. The indicating meters may be of any type, but preferably utilize the millivolt drop in a fixed length of bus or in a calibrated shunt. The millivolt drop in the bus is suitably temperature compensated by means of a thermistor if desired. The normal IR drop in 36 inches of bus in a particular commercial cell is about millivolts. Observing the millivolt meters, the anodes are raised by operating DPDT (double-pole, double-throw, momentary, center-off) switch 316 in the direction which opens solenoid valve 126 to motor 121. The hydraulic fluid drives the motor and the engaged chain raises anodes 113. To lower anodes 113, the same switch 316 is operated in the direction which operates four-way valve 220 which reverses the hydraulic supply and return lines and opens valve 126 for the one motor. The motor then runs in the reverse direction and lowers the anodes.

The anodes of a selected sub-group are adjusted by observing the current flowing to these anodes and the current is brought to a value corresponding to the optimum operation. Each sub-group of anodes is similarly adjusted. More particularly, various techniques suitable for anode adjustment according to the present invention include the following procedures:

(1) Each sub-group of anodes is lowered by a small amount while observing the current in each bus. As the anodes approach the cathode but prior to any incipient short, the millivolt meter reading fluctuates widely and then the anodes are raised until the current flow is steady. All the anodes are thus adjusted until they are close to the cathode and at an efficient operating distance therefrom. This procedure, frequently repeated, makes a number of small changes in the inter-electrode distance which avoids problems resulting from a large change. Such large changes tend to disturb the mercury flow pattern and leave the previously adjusted anodes in an inefficient position relative to the mercury cathode.

(2) Each set of anodes is lowered in turn until the millivolt meter reading begins to increase at an increased rate and then the anode lowering is stopped. This leaves the anodes at a preselected desirable interelectrode distance before any incipient short circuit occurs. This technique avoids incipient short circuits which disturb the mercury flow pattern and make reproducible reposition ing of the anode relative to the mercury surface diflicult. (3) Another alternative procedure useful for adjjusting the anodes depends on the resistance of a sub-group of anodes. The cell voltage signal and the millivolt signal are fed as input to an analog computer which produces an output reading of resistance, calculated according to the formula:

EE R I where R is the resistance of one sub-group of anodes. E is the cell voltage, E is the reversible potential of the particular electrode-electrolyte system and I is the current flowing to the sub-group of anodes. Each sub-group of anodes has a characteristic resistance at optimum efficiency to which that set of anodes is appropriately adjusted.

(4) Alternatively, the anodes are adjusted using the automatic raise feature provided by the reed switches.

The shielding of the reed switches is adjusted to give the desired differential between make and break positions and the switches are then adjjusted to the desired operating point for a particular sub-group of anodes. That subgroup is then lowered until the reed switch closes and automatically raises that sub-group of anodes until the current decreases by the preselected amount. Each subgroup of anodes is thus adjusted to the optimum interelectrode distance.

As each sub-group of anodes Wears, its characteristics change and its fraction of the total cell current for best efficiency changes. The operating point of the switches for automatically raising each sub-group of anodes is periodically reset and optimum current distribution is achieved by this method of adjustment.

The method of this invention thus provides better metering for adjustment and better control of anode position. Adjustment is also faster, which permits more frequent adjustment with the same manpower.

Automatic short circuit protection is provided by the method of this invention by continuously monitoring the current in every bus. If current in any bus exceeds an arbitrarily set value, a reed switch 329 closes, operating the valve supplying hydraulic motor 121 on that set of anodes and these anodes only are raised After the current in the bus drops to about 90% of the set value, reed switch 329 opens and raising of the anodes stops Suitable reed switches for use in the method of this invention are commercially available, low-cost devices One suitable switch is designed to open (break) under the influence of a magnetic field of about half that required to close (make) the switch. When shielded and mounted in contact with the bus as described, the differential between make and break is reduced so that a to reduction in current from the make value causes the switch to open.

The shielding of the reed switches is saturated so that it is effective up to about 80% of the operating value. The reed switch is subjected only to the field caused by the top 20% range of current. As the current in the bus increases from 80% of the make value up to the make value, the field sensed by the reed switch goes from almost zero to 100% of that required to make. Thus the differential between make and break is much closer than would be expected based on the rating of the reed switch and this increases the sensitivity of the switch.

High current in one bus bar 129 closes the reed switch 329, the 24 v. DC circuit is completed, solenoid valve 126 opens and motor 121 operates to raise the set of anodes served by that bus. Raising the anodes decreases the current in the bus and the magnetic field on the reed switch, which causes the switch to open. Valve 126 closes and motor 121 stops.

The reed switches are set to operate at about 130% of normal bus current. With this setting, when a switch operates, the anodes are raised until the current drops to about 11 5 of normal. The switch then opens and the anodes stop at this position.

The automatic short circuit protection raises anodes enough to correct a short circuit or other excessive current condition but it causes a decrease in current of only 5 to 10%. Thus the system moves the anodes enough to correct an excessive current condition but it does not over-correct.

This system provides constant protection against short circuits and indeed against any electrically overloaded anode circuit. Thus, the usual safety factor that is allowed when adjusting anodes manually is not necessary and anodes can be maintained in their most eificient position.

The method of this invention thus provides improved operation and efiiciency by providing a system for remote adjustment of anodes and by providing automatic short circuit protection.

Among the advantages of the method of this invention are:

(1) More frequent adjustment keeps anodes closer to optimum position.

(2) Anodes are maintained closer to the cathode because if an electrical over-load occurs, the anodes are automatically raised. The safety factor now used in setting anode-cathode spacing is eliminated.

(3) Improved control of anode travel permits more consistent adjustment.

(4) Anode loss due to short circuits is eliminated.

(5) Anodes are adjusted more evenly.

(6) The time period of operation with an electrical overload is substantially eliminated.

As a result of these advantages, the voltage required for operation of the cells is reduced by from 0.05 to 0.4 volt per cell. In a plant consisting of 58 cells, each with 50 anodes, the annual power cost saving amounts to about $30,000 for each 0.1 volt reduction. Graphite consumption is reduced by more accurate adjustment and avoiding short circuits. Labor costs are reduced because adjustment of the anodes is quick, easy and accurate.

EXAMPLE In a cell about 4 x 40 feet having 50 anodes arranged 5 side-ways by 10 lengthwise, the anodes were supported and adapted to be raised and lowered as described in US. Pat. 3,390,070. Hydraulic motors were attached to the shaft of the idler and hydraulic and electrical systems were provided as shown in the figures of this application.

As a result of the installation, no shorts occurred during an operating period of several weeks Occasionally one sub-group of anodes was raised automatically and subsequent adjustment was made manually.

An operator regularly adjusted each sub-group of five anodes until the mi'llivolt drop in the two bus bars serving each group was maintained at 3515 millivolts in a spacing of 3 feet between check points on each bus bar.

The voltage was reduced by about 0.05 volt per cell. This represent power cost savings of $15,000 per year in a plant of 58 such cells.

While the invention has been particularly described with reference to cells in which a sodium chloride brine is electrolyzed, it is to be understood that the method is equally useful Where the conductive solution electrolyzed is another alkali metal halide brine or an alkaline earth metal halide brine or other conductive solution. Examples of suitable electrolytes include potassium bromide, lithium chloride, barium chloride and sodium sulfate.

Advantageously for the practice of the invention all the necessary electrical leads for each cell are brought together in a multiple plug which can be engaged by a multiple plug attached to a portable control panel, suitably on a cart which can be rolled from cell to cell, whereby adjustment of all the anodes in a cell room is facilitated.

While the invention has been particularly described with reference to a system in which a pair of anode-supporting channels are mechanically connected by a sprocket and chain arrangement, it is to be understood that subgroups of a larger number of anodes and anode-supporting channels, for example, 3 or 4 or more, are suitably connected mechanically when this is advantageous and the anodes of such a larger sub-group are simultaneously adjusted as a single unit.

In a further advantageous modification of this invention, a plurality of reed switches are applied to each bus. Each reed switch is set to close and to open at a particular amperage of current in the bus but each is set to operate at a different amperage. Selecton of the appropriate switch in the automatic raise circuit or in the manual adjustment circuit permits changing the amperage fed to each anode without changing or adjusting any reed switch. One reed switch is set to operate at the highest current flow likely to be desired and additional switches are set to operate at lower operating points. Each switch has a separate power supply line which is turned off to all the switches set to operate at a lower current flow than the one selected.

The use of the reed switch set to operate at the lowest current flow above the desired current flow results in the maximum sensitivity to current imbalance. Inefiicient operation of a sub-group of anodes is more quickly detected and corrected. The one reed switch in operation at a particular time completely protects the system from damaging overload at any total cell current.

What is claimed is:

1. Method for adjusting the spacing between a plurality of anodes and the flowing mercury cathode in a cell for clectrolyzing a conductive solution wherein said anodes are adjustably suspended in said solution, which method comprises electrically controlling (1) intermittent flow of a control fluid and (2) the direction of said flow to one of a plurality of fluid-activated rotary adjustment means, each adapted for separately adjusting the elevation of a sub-group of said plurality of anodes above said cathode; said intermittent flow of said control fluid being electrically controlled by opening and closing an electrical circuit including means responsive to changes in the flux of the magnetic field generated by electrical flow in a conductor supplying said sub-group of anodes.

2. Method as claimed in claim 1 in which said means responsive to changes in the flux of the magnetic field is adjustable by rotation in said magnetic field.

3. Method as claimed in claim 1 in which said means responsive to changes in the flux of the magnetic field is magnetically shielded.

4. Method as claimed in claim 1 in which said means responsive to changes in the flux of the magnetic field is plural.

5. Method as claimed in claim 1 in which the direc- 10 tion of said flow is maintained to increase the elevation of said sub-group of anodes above said cathode.

6. Method as claimed in claim 1 in which said control fluid is hydraulic.

7. Method as claimed in claim 1 in which (1) said intermittent flow is controlled by providing a manually interruptable, selective second electrical circuit and closing said second circuit to initiate said intermittent flow to a selected one of said plurality of adjustment means and (2) controlling the direction of said intermittent flow by manually closing a third electrical circuit thereby reversing the direction of said intermeittent flow to decrease the elevation of the sub-group of anodes dependent on said selected adjustment means.

8. Method as claimed in claim 7 in which said second circuit is manually interrupted to stop said intermittent flow.

References Cited UNITED STATES PATENTS 2,542,989 2/1951 Carter et al. 204250X 3,390,070 6/1968 Cooper et al. 204225X 3,476,660 11/1969 Selwa 2042 19X FOREIGN PATENTS 1,521,277 3/1968 France 20499 1,110,048 4/1968 Great Britain 204219 JOHN H. MACK, Primary Examiner D. R. VALENTINE, Assistant Examiner US. Cl. X.R. 204219, 225, 228

3 3? UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,574,073 Dated April 6, 1971 Invent fl R, u. Ralston, Jr.

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 2, line 20, "means" should read --meant--; line 32,

"mercuury" should read --mercury--; line 49, "preventation" should read --preventi0n-.

Column 3, line 34, "18" should read --118-; line 55, 128" should read --218.

Column 4, line 2, "reverse" should read -reversed-; line 54 "geare" should read --geared-.

Column 6, line 58, "adjjust "should read --adjust- Column 7, line 3, "adjjusted" should read --adjusted-; line after the word "raised" insert a period line 27, afte the word "stops" insert a period line 29, after the v "devices" insert a period Column 8, line 38, "represent should read -represents--;

line 67, "Selecton" should read --Selection-.

Column 10, line 12, "intermeittent" should read -intermitte1 Signed and sealed this 10th day of August 1971.

(SEAL) Attest:

EDWARD I'I.FLETCHER,JR. WILL-11 1i E. SCHU'YLEZR, JR. Attesting Officer- Connnissioner of Patents