NO144066B - ELECTROLYCLE CELLS FOR ELECTROLYCE OF Aqueous SOLUTIONS, PARTICULARLY OF ALKALIMETAL CHLORIDES, AND PROCEDURES FOR THE MANUFACTURE OF THE ELECTROLYCLE CELL - Google Patents

Description

The present invention relates to electrolysis cells suitable for the electrolysis of aqueous solutions, and in particular cells equipped

for the electrolysis of aqueous alkali metal chloride solutions

gives.

Electrolysis cells have been widely used for many years

in the production of chlorine, chlorates, chlorides, hydrochloric acid, sodium hydroxide, hydrogen and other similar chemicals.

Meanwhile, such cells have been developed to such an extent

that a high operating efficiency has been achieved with regard to the electrical power used. The term operating efficiency includes current efficiency, splitting efficiency, energy efficiency, power efficiency and voltage efficiency. The latest development of such electrolytic cells

ler has gone out on. to improve the production capacity of the individual cells while maintaining the high operating efficiency. This has largely been done by modifying or rebuilding the individual cells as well as increasing the current values at which the individual cells work. The increased production capacity that is achieved for the individual cells that work at a higher current capacity enables a higher production rate for a given cell floor area and reduces the necessary capital investment as well as the operating costs per unit produced. '

The latest development of electrolysis cells has been towards larger cell units with high production capacity and which are designed to work with high current values while maintaining a high operating efficiency. Within certain operating parameters, the cell's production capacity will be higher the higher current values the cell is designed to work at. As the intended current value of a cell is increased,

however, it is important that a high operating efficiency is maintained. Simply increasing the size of the components in a cell designed to work at a low current value will not produce a cell that can work at higher current values and produce

shared, maintaining a high degree of operating efficiency. Numerous construction improvements must be included in an electrolysis cell with a high current value to achieve that high operating efficiency can be maintained and high production capacity achieved.

In the earliest designs, chlorine/alkali diaphragm cells were designed to operate at relatively low current ratings of around 10,000 amperes or less and had a correspondingly low output capacity. A typical representative of such cells is the so-called S-cell, which represented a major breakthrough in electrochemical technology at the time of the cell's development and initial practical application. This S-cell was later improved by a series of further developments such as the types S-3, S-3A, S-3B, S-3C, S-3D, and S-4, under which the improved cells were designed to work at increasingly higher current values, respectively around 15,000, 20,000, 25,000, 30,000, 40,000, and up to 55,000 amperes, with correspondingly higher production capacities. Design and performance of these type S cells are discussed in Shreve, Chemical Process Industries, Third Edition, page 233 (1967), McGraw-Hill; Mantell, Industrial Electro-chemistry, Third Edition, page 434 (1959), McGraw-Hill; and. Sconce, Shlorine, Its Manufacture, Properties and Uses, A.C.S. Monograph, pages 94-97 (1962), Reinhold. US Patent No. 2,987,463 mentions a chlorine/alkali diaphragm cell designed to be operated at a current value of about 30,000 amperes, and which is somewhat different from the aforementioned series of S cells. US Patent Nos. 3,464,912 and 3,493,487 relate to chlorine/alkali diaphragm cells designed to operate at a current rating of about 60,000 amperes.

on this background of known technology, it is an object of the present invention to produce an electrolysis cell of the type indicated above and which can work at current values of around 150,000 amperes and up to 200,000 amperes with correspondingly higher production capacities, at the same time as high

operating efficiency is maintained. ■

The invention thus relates to an electrolysis cell for the electrolysis of aqueous solutions, in particular of alkali metal chlorides,

and arranged' to be connected in series with other similar cells, the cell comprising a cathode chamber with conductive metal side walls, a cathodic busbar, cathode fingers with support devices, anodes with anode holder devices.

The special feature of the electrolysis cell according to the invention is that the cathodic busbar device includes at least one inlet busbar and several busbar strips with mutually different dimensions, the inlet busbar and the busbar strips being made of highly conductive metal and electrically connected, and the busbar device is in electrical contact with at least one side wall of the cathode chamber.

Each cathode finger comprises outer perforated conductive metal plates connected to an internal support device made of conductive metal and electrically connected rods of highly conductive metal placed on the cathode finger support devices, so that an internal gas cavity is formed in the cathode finger around the support device, and the cathode chamber contains a number of cathode fingers which extend mainly across the interior of the chamber and is electrically connected to the inside of at least one side wall of the chamber, while the cathodic busbar device is electrically connected to the outside of the same side wall.

The anode tube device comprises a highly conductive metal device with a mainly step-shaped cross-section which is composed of plates arranged next to each other and with a decreasing cross-section in the direction away from a contact surface, the metal device being electrically connected to contact points on the anode plates.

The new cathodic busbar device makes very economical use of the invested capital, particularly with regard to the highly conductive metal. The design and the different relative dimensions of the inlet busbar and the available number of busbar strips significantly reduce

the amount of highly conductive metal required in the cathodic busbar arrangement, compared to the prior art. The inlet busbar and the present busbar strips are, by virtue of their design and different relative dimensions, thus designed to maintain an essentially uniform current density over the entire busbar device.

The cathodic busbar device and the arrester device can be equipped with a device for connecting a bypass conductor when an adjacent electrolytic cell is removed from the electrical circuit. The busbar device and the arrester device can also be equipped with cooling devices to prevent the temperature in these devices from rising to harmful levels, as well as to further reduce the amount of well-conducting metal used.

Preferably, the cell is constructed so that the height of the various busbar strips that are included in the cathodic busbar device at the connection rafts against the side wall of the cathode chamber is essentially equal to the height of the cathode fingers' support device at the connection of the fingers to the side wall of the cathode chamber.

The support device for the cathode fingers preferably includes a wave-shaped conductive metal structure which is connected to the perforated metal plates by means of protruding ribs on the metal structure, and is equipped with protrusions on the outer rafts of the protruding ribs, for connection to the perforated metal plates to form additional cavities for gas.

The new anode construction comprises a well-conducting metal device with a mainly flat and even surface and a gradually decreasing cross-section in the direction away from the busbars between the cells. The well-conducting metal device can be a solid metal plate with the design described above or it can consist of two or more well-conducting metal pieces, for example in the form of plates, with different mutual dimensions and assembled in such a way that they form a current supply with gradually decreasing cross section, as described above. This device of well-conducting metal thus has different relative dimensions and is arranged so that it is able to conduct electric current and maintain essentially uniform current density through the anode holder construction up to electrical contact surfaces against the anode blades, without significant voltage drop and with the most economical power consumption possible in the anode holder construction.

The described anode holder construction utilizes invested capital in a favorable way by optimal utilization of the quantity of well-conducting metal used in the construction. The design and the different relative dimensions of the well-conducting metal device significantly reduce the required amount of well-conducting metal that is needed in the anode holder construction, compared to prior art. The well-conducting metal device is, by virtue of its design and its different relative dimensions, also well suited for maintaining essentially uniform current density throughout the entire anode holder construction.

The invention also applies to a method for carrying out a certain production step when manufacturing the cathode side of the cell, and this method involves connecting the rods of highly conductive metal to the support devices of the cathode fingers by first welding the same type of conductive metal that makes up the support devices to the rods and any metal failure resulting from the welding of dissimilar metals is then corrected, after which the conductive metal welded to the rods of highly conductive metal is welded to the conductive metal in the cathode finger support devices, whereby a firm mechanical connection is achieved between the rods of highly conductive metal and the cathode fin support devices mainly without metal failure of the welding connections.

The new electrolysis cell according to the invention can be used in many different electrolysis processes. Electrolysis of an aqueous solution of alkali metal chlorides is the most important application and the electrolysis cell of the invention will therefore be described in more detail with reference to a process of this type. However, this description should not be understood as a limitation of the electrolysis cell's applicability,

The present invention will now be described with reference to the attached drawings, on which: Fig. 1 shows an elevation of an electrolysis cell with a typical cathodic busbar device according to the invention; Fig 2 shows an enlarged partial section through the cell in fig. 1 along the plane 2 - 2 and shows the cathodic busbar arrangement seen from another side;

plane 2 - 2 and shows the cathodic busbar arrangement set

from another side.

Fig. 3 shows an enlarged part of a plan sketch of the wall-enclosed cathode chamber in the cell in fig. 1, and indicates the mutual positions of the cathode fingers', Fig. h is an enlarged section and elevation of the cathode fingers and the cathode chamber in the cell in fig. 3 along the section plane h-h and shows the relative positions of the cathode fingers and the anode blades placed at the end of the cathode chamber} Fig. 5 shows an enlarged elevation of a section through a cathode finger and the cathode chamber in the cell in fig. 3 along the plane 5-5" and shows the design of the highly conductive metal which is placed on the cathode finger's support device. Fig. 6 is an elevation of the opposite side of the cathode finger's holding device in Fig. 5 and shows the visible design of the highly conductive metal placed on the support device\ Fig. 7 is an elevation of another embodiment of the cathode finger's support device and shows the design of the highly conductive metal which is placed on the support device} Fig. 8 shows the cathode finger's support device in Fig. 7 seen from the side and in section along the plane 8-8 and also shows the design of the well-conducting metal which is placed on the support device as well as fastening means in the form of a knob or stick} Fig. 3) 't» 5", 6, 7 °g 8 shows, seen together, a typical embodiment of the cathode fingers' support device } Fig. 9 is a plan sketch of an anode holder construction that can be used in the cell in fig. 1, as the anode blades are not shown for the sake of clarity, Fig. 10 is an elevation of the anode holder construction in fig. 9 in section along the plane 10-10 and shows the well-conducting metal plates in detail} Fig. 11 is a sketch of the same type as fig. 10 and additionally shows a support structure for the cell} Fig. 12 is a plan sketch of an anode holder structure that can be used in the cell in fig. 1, as the anode blades are not shown for the sake of clarity} Fig. 13 is an elevation of the anode holder construction in fig. 12 in section along the plane 13-13 and shows the well-conducting metal plate in detail} and Fig. 1 is a sketch of the same kind as Fig. 13 and additionally shows a supporting construction for the cell.

Two different types of metal are used in the manufacture of most components or parts that make up the new electrolysis cell according to the present invention. One of these metal types is a good conducting metal. The second type of metal is a conductive metal with good holding strength and good construction properties.

The term "good conducting metal" is used in this connection for

a metal with low resistance to the passage of electric current and which is thus an excellent conductor of electric current. Suitable well-conducting metals include copper, aluminium, sol and the like as well as alloys of these metals. The preferred highly conductive metal is copper or one of its highly conductive alloys and any reference to copper in this application must be understood to mean that any other suitable highly conductive metal may be used in place of copper or any of its highly conductive alloys, when this is appropriate or practical.

The term "conductive metal" is used here to mean a metal with moderate resistance to the passage of electrical current, but which is still a relatively good conductor of electrical current. This conductive metal must also have good holding strength and good construction properties.

Suitable conductive metals of this nature include iron, steel,

nickel and the like, as well as alloys of these metals, such as e.g. stainless steel.and other chrome steel, nickel steel and the like. The preferred conductive metal is a relatively inexpensive bare steel, which will hereafter simply be referred to as "steel", and any reference to steel in this application shall be understood to mean that any other suitable conductive metal may be used instead. for said steel, when this is appropriate or practical.

The highly conductive metal and the conductive metal must have sufficient resistance or protection against corrosion during operation of the electrolytic cell.

In fig. 1 shows an electrolysis cell 11 which comprises a corrosion-resistant plastic cap 12, a wall-enclosed cathode chamber 13 and a cell support 1^. The top cap 12 is placed on top of the cathode chamber 13 and attached to this by means of attachment devices (not shown). A tight connection is maintained between the top cap 12 and the cathode chamber 13 by means of a gasket. The cathode chamber 13 is placed on the cell support 1<*>+ and attached to this by means of fasteners (not shown). A tight connection is maintained between the cathode chamber 13 and the cell support 1<>>+ by means of an elastomeric sealing insert. The electrolysis cell 11 is placed on leg 15 which is used as a support device for the cell.

The cathodic busbar device 16 is connected to which

in any suitable way, for example by welding, to the side wall 17 of steel in the cathode chamber 13. The cathodic busbar device 16 comprises an inlet busbar 18 of copper as well as several busbar strips 195 21 and 22 of copper, the inlet busbar and the various busbar strips being arranged to conduct electrical current and maintain substantially uniform current density through the cathodic busbar arrangement 16 to electrical contact surfaces on the side wall 17 of the cathode chamber 13.

The busbar device 16 can be equipped with a skirt device 23 comprising steel plates 2h, 25, 26 and 30, as well as inlet and outlet openings 27 and 28 made of steel and manufactured in any suitable way, for example by welding, to form said skirt device. The heating device 23 is connected in any suitable way, for example by welding, to the inlet busbar 18 and the busbar strip 19. A heating medium, preferably water, is caused to flow through the heating device 23 by means of a passage through the inlet and outlet opening 27 and 28. The heating device 23 is arranged primarily for use when an electrolysis cell next to the electrolysis cell 11 is disconnected and removed from the electrical circuit. Use of the heating device 2h allows the use of significantly less copper in the cathodic busbar device 16, which results in a significantly reduced capital investment for copper on the cathode side. Since the cooling device 23 is primarily arranged for use when an electrolysis cell next to the cell 11 is switched off, this cooling device 23 can also be used during normal cell operation, either to cool the cathodic busbar device 16 during periods of current overload or for continuous cooling of the device 16, thereby enabling a further reduction of the copper consumption in the busbar device 16 with correspondingly reduced capital investment for copper on the cathode side of the cell.

The input busbar 18 can be equipped with steel contact plates

29 and 31, which serve as..connectors. The steel contact plates 29 and 31 are connected to the intake busbar 18 in any suitable way, for example by means of screws 32. The intake busbar 18 and the steel contact plates 29 and 30 can be

equipped with holes 33, which can serve as means of connecting current conductors between the cells for carrying current from an adjacent cell, or wires for carrying current from another source to the intake busbar 18. The intake busbar 18 and the busbar strip 19 can be used as a cathodic bypass busbar when it is provided with holes 3<*>+ which can serve as means for connecting cathodic bypass conductors, when an adjacent electrolytic cell is disconnected and removed from the electrical circuit. It is during this disconnection process that the coil device 23 can prove to be most useful, as it relieves

the temperature in the cathodic busbar device 16 from rising to levels that may be harmful to the device 16 or other components of the electrolytic cell 11.

In fig. 2, the cathodic busbar device 16 is shown in another projection, and the description of this figure further includes a description of the design of the device and the different relative dimensions of the components or parts that make up the device 16, which were described in fig. 1.

The cathodic busbar device 16 comprises an inlet busbar 18 made of copper, as well as several busbar strips 19, 21 and 22 which are also made of copper. These busbar strips 19, 21 and 22 are connected to the steel wall 17 of the cathode chamber 13 in an appropriate manner, such as e.g. welds 35, 37? 38 and M of copper tL steel, as well as mutually in any suitable way, e.g. at welds 36 and 39 of copper to copper. The welding metal is preferably the same metal as is present in the busbar strips, which means copper. This embodiment of the connection between the busbar strips and the side wall 17 greatly reduces the required welding area and results in lower electrical contact resistance to the side wall 17 or the cathode steel. The inlet busbar 18 is connected to the busbar strip 19 in an appropriate manner, e.g. by means of welding h2 of copper to copper, and the inlet busbar 18 is also connected to the side wall 17 in a suitable way, e.g. using steel blocks <1>+3. The intake busbar 18 is

connected to the steel blocks U-3 in an appropriate manner, e.g. by means of a screw combination (not shown), and the steel blocks ^-3 are connected to the side wall 17 of the cathode chamber 13 in a suitable way, for example by welding ho of steel to steel. The steel contact plates 29 and 31 are connected to the inlet busbar 18 in a suitable way, e.g. by screws 32.

The above-mentioned connections produce a cathodic busbar device in which the inlet busbar 18 and the various busbar strips 19, 21 and 22 are attached and electrically connected to each other by means of welds 36, 37, 38, 39 and ^4-2, while the busbar device 16 forms electrical contact with the side wall 17 of the cathode chamber 13 by means of welds 35", 37, 38, <1>+0 and <1>+1.

The cathode fingers <1>+<1>+ are arranged in electrical contact with the side wall 17 in any suitable manner, for example by welding the cathode finger support means <1>+5 to the side wall 17. A typical cathode finger <1>+<1> + is partially shown. The cathode finger <1>+<1>+ comprises a support device <1>+5 and perforated steel plates <1>+6 which are attached in a suitable way, for example by welding. Perforated steel plates <1>+7' are connected in any suitable way, for example by welding, to the perforated steel plates <1>+6 and the side wall 17, so that a peripheral chamber 1+8 is formed.

The height of the different busbar strips at the points of contact with the side wall 17 is usually substantially equal to the height of the cathode finger support device at their attachment point to the side wall 17. This height can further be defined as more than about half the height of the cathode chamber 13. The thickness of the busbar strips 21 and 22 is preferably smaller than the thickness of the inlet busbar T8 and the busbar strip 19.

The support devices for the cathode fingers are preferably formed by bellows structures made of conductive steel plates, but other suitable support devices such as e.g. conductive metal rods, plates, reinforced plates and the like can also be used. The support devices of the cathode fingers serve the double function of firstly supporting and reinforcing the perforated steel plates,'..and secondly conducting electric current to all parts of these steel plates with the least possible electrical resistance.

The pierced conductive metal members used to form the cathode fingers and the peripheral chamber are preferably made of perforated steel plates, but can be steel screens. Other suitable pierced conductive metal bodies which can be used for forming the cathode fingers and the peripheral chamber include conductive metal grids, mesh nets, screens, wire mesh or the like.

The wall-enclosed cathode chamber 13 is placed on the cell support ^ h and attached to this support by means of fasteners (not shown). The cell support 1<l>+ comprises an elastomeric sealing insert <*>+9 and a conductive anode holder 5"1 ? °g is, if required, provided with a support structure 52. A seal is maintained between the cathode chamber 13 and the cell support 1<>>+ by using said elastomeric sealing inserts ^+9.

In a typical circuit for electrolysis cells, the electrical

current through mutual connections (not shown) between the cells of the inlet busbar 18 for the cathodic busbar device 16. This device 16 then conducts electric current with essentially uniform current distribution without significant voltage loss and with the most economical power consumption in the busbar device 16. This essentially uniform current density is maintained across the busbar device 16 by means of the design and the different relative dimensions of the inlet busbar 18 and the busbar strips 19, 21 and 22. Electric current is thus fed through the cathodic busbar device 16 to electrical contact surfaces on the side wall 17 of the cathode chamber 13, from which the current is distributed. the cathode fingers M+, and under these conditions electric current is easily fed to all parts of the perforated steel plates h6 with the least possible electrical resistance through the cathode fingers' support devices <1>+5.

The new cathodic busbar device utilizes invested capital as best as possible by optimizing the amount of copper or other suitable well-conducting metal used in the busbar device. The design and the different relative dimensions of the input busbar and the various busbar strips significantly reduce the amount of copper or other suitable well-conducting metal required in the busbar device, compared to corresponding known devices. The input busbar or busbars and the various busbar strips are also, by virtue of their design and different relative dimensions, also arranged to conduct electrical current in such a way that substantially uniform current density is maintained across the cathodic busbar device.

The design and dimensions of said inlet busbar and the various busbar strips can vary depending on the current rating the electrolysis cell is designed for, and is also dependent on a number of further factors, such as e.g. the desired current density, the conductivity of the metal used, the size of the welding areas, production costs and the like.

The new cathodic busbar device results in improved electrical conductivity to the intermediate areas of the cathode fingers, whereby minimal or no significant voltage drop is achieved along the busbar device, with significantly reduced consumption of copper or other suitable well-conducting metal compared to known devices.

The new device makes it possible to construct electrolysis cells according to the present invention as a chlorine/alkali diaphragm cell with a high current value of around 150,000 amperes and up to 200,000 amperes, while maintaining a high operating efficiency. These high current values thus lead to high production capacity, which results in a high production rate for a given cell floor area as well as reduced capital investments and operating costs.

In addition to being able to work at high currents, the electrolysis cell according to the present invention can also work efficiently at low currents, such as e.g. about 55,000 amperes, using the new cathodic busbar device.

In fig. 3 it is shown that the cathode fingers hh are enclosed by steel walls 17, 5^, 55 and 56 which form a cathode chamber 13. The cathode fingers kh may be present in any number, from about 10 to about 50 or more, the number is preferably approx. 15 to <>>+0 and preferably 20 to 30. The anode blades (not shown) are placed between the cathode fingers respectively. Perforated steel plates ^+6 are connected in any convenient way, e.g. when welding to the cathode finger support devices !+5. The steel plates 53 are also attached in a suitable manner, for example by welding,

to the support devices of the cathode fingers ^5. The cathode fingers hh are connected to the steel wall 17 in any suitable way, for example by welding steel plates 53 °g the cathode fingers

support devices 1+5 to the side wall 17. Perforated steel plates k-7 are connected at the side walls 17, 5^, 55 and 56, as well as to the perforated steel plates 1+6 in any suitable way, for example by welding. The perforated steel plates <1>+7 are arranged along the inner side walls of the cathode chamber 13, and form a peripheral chamber <1>+8 which serves as a collection chamber for the hydrogen gas formed at the cathode during the electrolysis process. Hydrogen gas that is developed at the cathode during electrolysis is led over the cathode fins <1>+<1>+ to the peripheral chamber <1>+8, from where the gas is passed on to a gas discharge 57"

In fig. <1>+ it is shown that perforated steel plates 1+6 are attached

appropriately, e.g. when welding, to the cathode finger support device <1>+5. The steel plates 53 are connected in an appropriate manner, e.g. when welding to the support device <1>+5. A carrying device 58 is attached in a suitable manner, e.g. when welding,

to the cathode fingers' support device <1>+5 and the side wall 56 for the cathode chamber 13 of steel. Perforated steel plates <1>+7 are attached in a suitable manner, for example by welding, to the perforated steel plates 1+6 and the side walls 17 and 56, to form the peripheral chamber 1+8. Due to the larger scale in this figure, the peripheral chamber 1+8 is more clearly shown. The cathode finger support device <1>+5 can be equipped with protrusions 59 and the perforated steel plates 1+6 can be attached in a suitable way, for example by welding, to the protrusions in order to thereby form additional cavities for hydrogen gas which is formed at the cathode during the electrolysis and shall is passed on to the peripheral chamber <1>+8.

The steel tips 61 and the steel plates 53 are fixed in any suitable way, for example by welding, to the copper rods 62. The steel tips 61 and the steel plates 53 are fixed in a suitable way, for example by welding, to the cathode finger support device <1>+5 to thereby place copper rods 62 on the support device.

The cathode fingers' support device <1>+5 preferably has a corrugated structure and is made of plate steel, but other appropriate support devices such as e.g. stasis, plates, stiffened plates and the like can also be used. The cathode finger's support device <1>+5 serves the dual function of firstly supporting and stiffening the perforated steel plates 1+6, and secondly to conduct electric current to all parts of said perforated steel plates 1+6 with the least possible electrical resistance through the cathode finger's support device 1+5.

Reference must now be made to fig. 2 and <l>+, which show the wall-encased cathode chamber 13 placed on the cell support 1>+ and attached to this support by fastening means (not shown). The cell support 1<1>+ comprises a conductive anode holder 51 and, if required, a suitable support structure 52. A seal is established between the cathode chamber 13 and the support 11+ by means of an elastomeric gasket insert 1+9.

The anode blades 72 are preferably of metal and electrically contact-connected to the conductive anode holder 51 in a suitable manner, e.g. by means of nuts and/or bolts, secured protrusions, knobs, welding or the like. The cathode fingers <1>+<1>+ are arranged at such mutual distances that the anode blades 72 can be placed in the middle between successive cathode fingers 1+1+, whereby the desired alignment of the anode blades 72 and ka twodef ingr ene 1+1+ is created.

The electrolysis cell 11 shown in fig. 2, 3 and <1>+ is particularly applicable for the electrolysis of solutions of alkali metal chlorides in general, which does not only apply to sodium chloride,

but also potassium chloride, lithium chloride, rubidium chloride and cesium chloride. When the electrolysis cell 11 is used for the electrolysis of such solutions, the cell 11 is equipped with a diaphragm 71 which serves to mutually separate anolyte and catholyte compartments, so that chlorine is formed at the anode and sodium hydroxide and hydrogen at the cathode. The diaphragm 71 comprises a liquid-permeable but halogen-repellent material which covers the steel plates 1+6 which are connected to the cathode fins 1+1+, as well as the perforated steel plates 1+7 which form the peripheral chamber 1+8. The diaphragm 71 is preferably made of asbestos fibers arranged in place on the outside of the perforated steel plates 1+6 and <1>+7. The electrolysis cell 11 is designed to enable the use of many diaphragm types, including asbestos tissue, asbestos paper, asbestos

flakes and other suitable materials known to those skilled in the art.

The perforated steel plates <1>+6 which are connected to the cathode fingers 1+1+, and the perforated steel plates <1>+7 which form the peripheral chamber 1+8 are perforated conductive metal members. Other suitable perforated conductive metal bodies which can be used for supporting the cathode fingers and forming the peripheral chamber include conductive metal grids, mesh nets, screens, wire mesh or the like.

In fig. 3 and 5, certain details described in the preceding figures are more clearly shown. The cathodic busbar device 16 is connected to the outside of the side wall 17 of the cathode chamber 13, while the ends of the cathode fingers 1+1+ which face this wall are connected to the inside of the wall in the cathode chamber 13, in the manner or ways described in connection with the preceding figures.

The other end of the cathode fingers 1+1+ is preferably placed in the following way: The outer edges 63 of the cathode fingers' support devices 1+5 are placed against the steel side wall <1>+5 of the steel cathode chamber 13 by means of steel support pieces 6* +, 65, 66 and 67. The support pieces 6<*>+ and 65 are fixed in any suitable way, e.g. by welding, to the cathode fin support devices 1+5 and h/ile against the support pieces 66 and 67, which in turn are fixed in a suitable way, e.g. by welding, the side wall 55. The support pieces 61+ and 65 can be connected or fixed respectively to the support pieces 66 and 67, but it is preferred that the pieces 6<1>+ and 65 are not fixed, so that linear thermal expansion and/or contraction can take place freely for cathode def ingers <1>+<1>+.

The perforated steel plates 1+7 are fixed in any suitable way, such as e.g. by welding, to each side wall, respectively 17, 5^, 55 °g 56, as well as to the adjacent perforated steel plates 1+6 to form the peripheral chamber 1+8.

The copper rods 62 are preferably of different lengths and are preferably placed on the cathode fin branches' support devices 1+5, as shown in fig. 5. The steel tips 61 are attached in any suitable manner, such as by welding to the ends 68 of the copper rods 62, while the steel plate 53 is attached in a suitable manner, e.g. by welding, to straighten ends 73 of the copper rods 62 to form a cathode assembly 69 of copper. The assembly 69 is attached to the cathode finger support devices 1+5 in a suitable manner, for example by welding the tips 61 and the steel plate 53 to the support device 1+5 of steel. The copper rods 62 can thus be placed on the cathode finger support devices <1>+5. The copper rods 62 have sufficient

but preferably different lengths are interposed, in order to maintain substantially similar current density in each cathode finger M+. The copper rods 62 do not necessarily need to be round or have the same cross-section along their entire length, but can have a square, rectangular, hexagonal, octagonal or similar cross-section, as well as varying cross-sections along the length. It is, however, important that the copper rods 62 have sufficient length and cross-section to conduct the necessary electric current and to maintain essentially the same current density in each cathode finger <1>+<1>+ without significant voltage drop and with the most economical power consumption in the cathode fingers <1> +<1>+.

Use of a suitable well-conducting metal, such as for example copper, in the cathodes 1+1+, as indicated in fig. l+, 5 5 6, 7 and 8, are believed to be a new application of a suitably good conducting metal. The use of copper in similar fingers is discussed in US patents 3.<i>+6<L>+.912 and 3A93.<I>+87, but in no way is the application suggested, much less described, in these documents of copper in cathode fingers for electrolytic cells in the manner indicated above.

The preferred method for placing the copper rods

62 on the cathode fingers' support devices <1>+5 and in the cathode fingers M+ itself, is also new. The steel tips 61 are welded to the ends 68 of the copper rods 62 and the steel plate 53 is welded to the straight ends 73 of the copper rods 62, so that a cathode assembly 69 of copper is formed. Any distortion in the welding of the steel tips 61 and the steel plate 53 to the copper rods 62 is corrected or is compensated for the cathode assembly 62 is connected to the cathode fin arms' support devices 1+5". The copper cathode assembly 69 is attached to the support devices h5 by welding the steel tips 61 and the steel plate 53 to the cathode fin arms' support devices <!>+5 of steel. The copper rods 62 are thereby placed on the cathode fin arms' support devices <1>+5 and in the cathode fingers themselves respectively. In this way, all welds between copper and steel for the welding of the cathode assembly 69 to the cathode finger support devices >+5 are carried out, and any distortion created during welding can be effectively eliminated.

The new cathode fingers make it possible to construct an electrolysis cell according to the invention in such a way that it can work as a chlorine/alkali diaphragm cell at high current values of about 150,000 amperes and up to about 200,000 amperes, while maintaining a high operating efficiency. These high current values make it possible to achieve a high production capacity, which results in a high production rate for a given cell floor area as well as reduced capital investments and operating costs. In addition to being able to work with high current values, the electrolytic cell of the invention can also work efficiently at lower current values, such as e.g. about 55,000 amperes, when using the new cathode fingers.

In fig. 6 shows the opposite side of the cathode finger support device !+5, in relation to the side shown in fig. 5, and the visible location of the copper rods 62 on the support device is also shown. The cathode assembly 69, which comprises copper rods 62, steel plates 53 and steel tips 61, is shown placed on the cathode finger support device !+5. The support device h-5 can be equipped with protrusions 59, so that perforated steel plates h6 can be attached in any suitable way, for example by welding, to the protrusions 59 to create additional cavities for hydrogen gas which is formed at the cathode during electrolysis, for passing on to the peripheral chamber h8. Protrusions 59 are placed at intervals on the cathode finger support device *+5 and only a representative section is shown in this figure.

In fig. 7 and 8, another embodiment of a support device for a cathode finger is shown, while the position of copper rods on the support device is also shown. In this embodiment, the support device 111 comprises a steel plate 112 with protruding peg or pin devices 113. The cathode assembly 69, which comprises copper rods 62, steel plates 53 and steel tips 61, is shown placed on the steel plate 112 for the support device 111, with a section of the steel plate 112 being removed for placement of the steel plate 53. The copper assembly 69 is connected to the cathode finger support device 111 in any suitable way, for example by welding the steel plate 53 and the steel tips 61 to the steel plate 112. Perforated steel plates 46 can be attached in any suitable way, for example by welding, to the steel pin device 113, thereby creating cavities for hydrogen gas which is formed at the cathode during the electrolysis and which is to be carried on to the peripheral chamber 48.

In fig. 9 and 10, an anode holder construction 74 is shown which comprises a copper plate 75 and another copper plate 76, and may also comprise steel plates 77, 78, 79, 81, and 98 or other suitable construction details. The anode holder structure 74 can be protected against corrosion by means of an elastomeric sealing insert 49. The copper plates 75 and 76 can be equipped with a fastener 82 for the anode blades, which can be used to connect the anode blades 72 to the copper plates 75 and 76.

The anode blades 72 may be made of any electrically conductive material capable of withstanding the corrosive attack of the cell's various reactants and products that come into contact with the anode blades. The anode blades 72 are preferably of metal. Such anode blades 72 can typically be manufactured from a so-called "valve metal", such as, for example, titanium, tantalum or niobium or possibly alloys of these metals where the valve metal makes up at least 90% of the alloy. The surface of the valve metal can be made active by means of a coating of one or more noble metals, noble metal oxides or mixtures of

such oxides, possibly with oxides of the valve metal.

The noble metals that can be used include ruthenium, rhodium, palladium, iridium and platinum. Particularly preferred metal anodes are anodes made of titanium and provided with a coating of mixed titanium oxide and ruthenium oxide on the surface, such as that described in US Patent No. 3,632. 498. In addition, the valve metal substrate can be applied to a more electrically conductive metal core, for example of aluminium, steel, copper or the like.

The anode blades 72 may be attached to the copper plates 75 and 76

in any appropriate manner, such as by means of nuts and/or bolts, attached protrusions, studs, welding or the like. A typical method for attaching the anode blades 72 to the copper plates 75 and 76 can be found in US Patent No. 3,591,483.

An anode bus bar 97 can be produced by attaching steel contact plates 89 and 91 to the copper plate 75 using means 85, the said steel and copper plates being equipped with holes 83 which can serve as means for connecting conductors for conducting electric current from an adjacent cell or another current source for the anode busbar.97.

Fig. 10 shows that the assembled copper plates 75 and 76 mainly form a gradually decreasing cross-section. The copper plates 75 and 76 have mutually different dimensions and are arranged in such a relative position that the copper plates 75 and 76 are able to conduct sufficient electric current at substantially the same current density in the anode holder structure 74 up to the electrical contact surfaces against the anode blades 72, without significant voltage loss and with the most possible economic power consumption in the anode holder construction 74. Mainly uniform current density is achieved by such an assembly of the various copper plates 75 and 76 that a total decreasing cross-section is achieved in discrete steps, ie. electrical current is taken mainly evenly distributed from the copper plates as the overall cross-section of the plates decreases.

In a typical circuit for the electrolysis cell, electric current is fed through supply conductors (not shown) to the anode busbar 97

in anode holder construction the ion 7h. Electric current is then fed with essentially similar current density through the anode holder construction 7<*>+} without significant voltage loss and with the most economical power consumption possible in the construction 7h. Supplying sufficient electric current and maintaining substantially uniform current density in the anode holder structure 7<*>+ is achieved by means of the design and the different relative dimensions of the copper plates 7? and 76. Electric current is thus fed through the construction 7h to electrical contact surfaces where the current is distributed on the anode blades 72 under such conditions that current is supplied to all parts of the blades 72.

The new anode holder construction makes use of invested capital

in the best possible way, namely by optimizing the amount of copper or other suitably well-conducting metal used in this construction. Design and the different relative dimensions of the copper plates significantly reduce the required amount of copper or other suitably well-conducting metal used in the anode holder construction, compared to known technology. Due to their design and dimensioning, these copper plates are also suitable for lining sufficiently

■electric current and maintain substantially similar current density in the anode holder structure.

The design and dimensions of the copper plates can vary depending on the desired current value for the electrolysis cell, and can also vary depending on a number of additional factors, such as current density, the conductivity of the metal used, the size of the welding area, manufacturing costs and the like. The new anode holder construction leads to improved electrical conductivity up to the anode blades, so that the least possible or no significant voltage drop is achieved along the anode holder construction with a significantly reduced consumption of copper or other suitably well-conducting metal, compared to known technology.

The new anode holder construction makes it possible to construct the electrolysis cell according to the invention for operation as a chlorine/alkali diaphragm cell with high current values of around 150,000 amperes and up to 200,000 amperes, while maintaining high operating efficiency. These high current values lead to high production capacity, which in turn results in a high production rate for a given cell floor area as well as reduced capital investments and operating costs. In addition to the cell being able to operate at high current values, it can also be operated efficiently at lower values, such as around 55,000 amperes, using the new anode holder design.

The anode holder structure 7<*>+ can be equipped with a coil device 92. The coolant, which is preferably water, is caused to flow through the coil device 92 by inlet through the inlet port 92 and passage through liquid-carrying means 95. After inlet through the inlet port 93, the coolant is fed along the steel plate 87 into and through the boiler equipment 96 and beyond

again along the steel plate 87. The dressing agent is then brought to flow along the steel plate 88 and then along and around the steel plate 89. The dressing agent is then fed along the opposite side of the steel plate 89 and then along the opposite side of the steel plate 88. The dressing agent is then brought to flow along it opposite side of the steel plate 87 and flows out through the outlet opening 9^. The fluid carrying means 95 may be any suitable carrying means, for example copper pipes connecting the coil equipment 96 and coil medium carrying channels arranged along the sides and ends of the steel contact plates 87, 88 and 89. The coil means 92 shown in this figure and described here, constitutes only an example of a typical coil device and the invention is in no way limited to the embodiment shown in the present figure and described above.

Use of the heating device 92 allows the use of a significantly smaller amount of copper in the anode holder construction 7^? which results in a significant reduction in the need for invested capital for anode copper. Damaged coil device 92

is arranged preferably for use when an adjacent

electrolysis cell is switched off, this device 92 can also be used during normal routine operation of the cell, either to cool the anode copper during any periodic overload or to continuously cool the anode copper to thereby

achieve a further reduction in the copper consumption in the anode holder construction j ion 7^5, which entails correspondingly reduced capital costs in this connection.

An anode bypass rail 99 can be provided by connecting steel contact plates 87 and 88 using means 86 to the copper plate 75? as said steel and copper plates are equipped with holes

&+ which can serve as means for connecting said bypass rail when an adjacent electrolysis cell is disconnected and removed from the electrical circuit. It is during this switch-off process that the skirt device 92 finds its greatest application by preventing the temperature in the anode holder construction 7^ from rising to levels that cause damage to the construction kh- or other components in the electrolysis cell 11.

In fig. 11 shows another embodiment of the anode holder construction 7^5 in that it is equipped with a carrier construction 52 which provides additional support for the construction 7>+. This embodiment will be advantageous and is preferred when the anode holder construction is made of a good conducting metal,

like for example. copper, which has excellent electrical properties but relatively poor structural properties. The supporting structure 5<*>2

can be made of any suitable construction materials, such as aluminium, iron, steel and the like, as well as alloys of these materials, such as stainless steel or other chrome steel, nickel steel and the like, and which have sufficient strength to form the required support. Such construction materials can take the form of I-beams, T-beams, L-beams, U-beams and the like. However, the support structure 52 does not need to be made of metal, but can also consist of other suitable construction materials, such as concrete, reinforced concrete or the like.

In fig. 12, 13 and 1*+ there is shown a different embodiment of the anode holder construction 7^ than that indicated in fig. 9, 10 and 11. The description of fig. 9, 10 and 11, however, also apply to fig. 12, 13 and 1<*>+, as the only thing that separates the latter figures from the former are additional copper plates 101 and 102, as well as steel plates 103 and 10^-. There is also an addition of a fourth row of anode blades 72, as well as a slight modification of the dress device 92 and bypass rail 99.

Fig. 13 and 1<i>+ show that the combined cross-sections of the copper plates 75"? 76, 101 and 102 form a combined cross-section in the form of a mainly stepped, truncated right triangle. The copper plates 75"} 76, 101 and 102 have mutually different dimensions and are assembled in such a way that the copper plates 75) 76, 101 and 102 are able to conduct sufficient electric current and to maintain essentially similar current density in the anode holder construction j ion 7<*>+ up to electrical contact surfaces against the anode blades 72, without significant voltage loss and with the most economical power consumption in the construction 7h.

Mainly similar current density is achieved by the special assembly of the different cross-sections of the copper plates 755 76, 101 and 102 into a combined cross-section mainly in the form of a step-shaped, truncated right triangle, from which electric current is drawn from the copper plates as the cross-section of the plates decreases.

In a typical circuit for electrolysis cells, the electric current is fed through current conductors (not shown) between the cells to the anode busbar 97 in the anode holder structure 7^. Electric current. of sufficient strength and essentially similar current density is then fed through the anode holder structure 7^ without significant voltage loss and with the most economical power consumption possible in the structure 71+. Sufficient electric current is obtained and substantially uniform current density is maintained in the anode holder structure 7h by means of the design and the different relative dimensions of the copper plates 75, 76, 101 and 102. Electric current is thus fed through the anode holder structure 7h to electrical contact surfaces where the current is distributed on the anode blades 72, under such condition that the current spreads easily to all parts of the anode blades 72. The new anode holder construction utilizes invested capital in the best possible way by using an optimal amount of copper or other suitably well-conducting metal in the construction. The assembly used and the different relative dimensions of the copper plates significantly reduce the required amount of copper or other suitable conductive metal in the anode holder construction compared to corresponding known constructions. On the basis of their assembly and different relative dimensions, the copper plates are also suitable for carrying sufficient electrical current and for maintaining substantially uniform current density throughout the construction.

The assembly and dimensioning of the copper plates may vary

depending on the desired current value for the electrolysis cell,

and is also dependent on a number of further factors, such as the current, the conductivity of the metal used, the size of the welding area, manufacturing costs and the like.

The new anode holder construction provides improved electrical conductivity up to the anode blades, whereby the least possible or no significant voltage drop across the anode holder construction is achieved together with a significantly reduced consumption of copper or other suitably well-conducting metal, compared to corresponding known constructions.

The anode holder structure 7<*>+ which is shown in fig. 9-1^ may be

an embodiment of the conductive anode holder 51 which is shown in fig. 2

and H.

The new anode holder construction makes it possible to construct the electrolysis cell according to the present invention for operation as a chlorine/alkali diaphragm cell at high current values of around 150,000 amperes and up to 200,000 amperes, while maintaining high operational efficiency. These high current values thus lead to high production capacity, which in turn results in a high production rate for a given cell floor area, as well as reduced capital requirements and reduced operating costs. In addition to being able to work at high amperages, the electrolysis cell of the invention can also work efficiently at lower amperage values, such as 5"5".000 amperes, by using the new anode holder construction.

The following exemplary embodiment will illustrate the application of the invention in practice.

EXAMPLE.

The following data are typical of the operating results obtained with the new electrolysis cell according to the present invention at a current value of 150,000 amperes. These operating data are compared with operating data for a smaller electrolysis cell of known design and with metal anode blades, the latter cell works with a current value of 8!+,000 amperes. Both electrolytic cells are chlorine/alkali diaphragm cells. •* The cells can be operated with a lower content of NaOH in the cell liquid. This will result in a higher current efficiency.

The above-mentioned data show that the new electrolysis cell according to the present invention works with essentially the same current efficiency, voltage and other operating conditions as the smaller, known electrolysis cell, and with the same anode current density. The new electrolysis cell according to the invention has a higher production rate for a given cell floor area, uses less operating personnel and also entails lower capital investment per tonnes of chlorine produced.

This example shows that an electrolysis cell can be made for

to work at a high current value to provide a high production capacity and a high production rate, while maintaining a high operating efficiency.

The new electrolysis cell according to the present invention can, however, be used for many other purposes. Alkali metal chlorates can, for example, be produced using the electrolysis cell of the invention, as the formed sodium hydroxide and chlorine can be brought to further reaction outside the cell. In this case, solutions containing both alkali metal chlorate and alkali metal chloride can be recycled to the electrolysis cell for further electrolysis. The electrolysis cell can be used for the electrolysis of hydrochloric acid alone or in combination with alkali metal chloride. The new electrolysis cell according to the present invention thus has a high applicability in connection with the aforementioned and many other aqueous solutions.

Claims (16)

1. Electrolysis cell (11) for the electrolysis of aqueous solutions, in particular of alkali metal chlorides, and designed to be connected in series with other similar cells, the cell comprising a cathode chamber (13) with side walls (17, 54, 55, 56) of conductive metal, a cathodic busbar (16), cathode fingers (44) with support devices, anodes (71) with anode holding devices (74), characterized in that: (I) the cathodic busbar device (16) comprises at least one inlet busbar (18) and several busbar strips (19, 21, 22) with mutually different dimensions, the inlet busbar (18) and the busbar strips being of well-conducting metal and electrically interconnected, and the busbar device (16) is in electrical contact with at least one side wall (17) of the cathode chamber (13), (II) each cathode finger comprises outer perforated conductive metal plates (46,47) connected to an internal support device (45) made of conductive metal and electrically connected rods (62) of highly conductive metal placed on the cathode fingers' support devices, so that an internal gas cavity (48) is formed in the cathode finger around the support device, and the cathode chamber (13) contains a number of cathode fingers (44) which extend mainly across the interior of the chamber (13) and is electrically connected to the inside of at least one side wall of the chamber, while the cathodic busbar device (16) e r electrically connected to the outside of the same side wall (17), (III) the anode holder device (74) comprises a highly conductive metal device with a mainly step-shaped cross-section which is composed of plates (75, 76, 101, 102) arranged next to each other and with decreasing cross-section in the direction away from a contact surface (89), the metal device being electrically connected to contact points on the anode plates (72). 2. Electrolysis cell as specified in claim 1, characterized in that the anode holder device (74) and/or the cathodic busbar device (16) is equipped with a device (34) for connection to a bypass conductor, when an adjacent electrolysis cell is disconnected and removed from the electrical circuit. 3. Electrolysis cell as specified in claim 1, characterized in that the anode holder device (74) and/or the cathodic busbar device (16) is equipped with a cooling device. 4. Electrolysis cell as stated in claim 1, characterized in that the cathode chamber (13) contains 10 to 50 cathode fingers (44). 5. Electrolysis cell as specified in claim 1, characterized in that the height of the different busbar strips (19, 21, 22) which are included in the cathodic busbar device (16) at the connection rafts against the side wall of the cathode chamber (13) is mainly equal to the height of the cathode branch support device (45) at the connection of the fingers to the side wall of the cathode chamber (13). 6. Electrolysis cell as stated in claim 1, characterized in that the cathode finger's support device made of conductive metal comprises a wave-shaped construction (45). 7. Electrolysis cell as stated in claim 6, characterized in that the wave-shaped conductive metal construction (45) is connected to the perforated metal plates (46) by means of protruding ribs on the metal construction. 8. Electrolysis cell as stated in claim 7, characterized in that the wave-shaped, conductive metal structure (45) is equipped with protrusions (59) on the outer surfaces of the protruding ribs, for connection to the perforated metal plates (46) to form additional cavities for gas . 9. Electrolysis cell as specified in claim 1, characterized in that the cathode finger support device (111) of conductive metal comprises a conductive metal plate (112) with peg or pin devices (113), 10. Electrolysis cell as set forth in claim 1, characterized in that the rods (62) of highly conductive metal are connected to the support devices (45) of the cathode fingers. 11. Electrolysis cell as stated in claim 10, characterized in that the rods (62) of highly conductive metal have different lengths, 12. Electrolysis cell as stated in claim 10 or 11, characterized in that the rods (62) of highly conductive metal have different cross-sections. 13. Electrolysis cell as specified in claim 1, characterized in that support pieces (64, 65, 66f 67) are arranged to bring the cathode fingers (44) into position at the side wall which is directly opposite the side wall to which the fingers are connected with, 14. Electrolysis cell as stated in claim 1, characterized in that the anode holder device comprises a support structure (52) which is designed to support the well-conducting metal device (75, 76, 101, 102) and consists of an assembly of shaped metal pieces which, together with the metal device form a unit. 15. Electrolysis cell as stated in claim 1, characterized in that the anode holder device is dimensioned to also support parts of the electrolysis cell other than anodes. 16. Method for manufacturing an electrolytic cell (11) for the electrolysis of aqueous solutions, in particular of alkali metal chlorides, and arranged to be connected in series with other similar cells, the cell comprising a cathode chamber (13) with side walls (17, 54, 55, 56) of conductive metal, a cathodic busbar (16), cathode fingers (44) with support devices, anodes (71) with anode holder devices (74), and the cell further has the following special features: (I) the cathodic busbar device (16) comprises at least an inlet busbar (18) and several busbar strips (19, 21, 22) with mutually different dimensions, the inlet busbar (18) and the busbar strips being made of highly conductive metal and electrically interconnected, and the busbar device (16) being in electrical contact with at least one side wall (17) of the cathode chamber (13); (II) each cathode finger comprises outer perforated conductive metal plates (46,' 47) connected to an internal support device (45) made of conductive metal and electrically interconnected rods (62) of highly conductive metal placed on the cathode finger support devices, so that it forms internal gas cavities (48) in the cathode finger around the support device, and the cathode chamber (13) contains a number of cathode fingers (44) which extend mainly across the interior of the chamber (13), and are electrically connected to the inside of at least one side wall of the chamber , while the cathodic busbar device (16) is electrically connected to the outside of the same side wall (17); (III) the anode holder device (74) comprises a highly conductive metal device with a mainly step-shaped cross-section which is composed of plates (75, 76, 101, 102) arranged next to each other and with a decreasing cross-section in the direction away from a contact surface (89), in that the metal device is electrically connected to contact points on the anode plates (72), characterized in that the rods (62) of highly conductive metal are connected to the cathode fins' support devices (45) by the same type of conductive metal that makes up the support devices being first welded to the rods (62 ) and any metal rejection resulting from the welding together of dissimilar metals is then corrected, after which the conductive metal welded to the rods of highly conductive metal is welded to the conductive metal in the support devices of the cathode fins, whereby a firm mechanical connection is achieved between the rods of highly conductive metal metal and the cathode finger's support devices mainly without metal failure of weld ef the orbs.