US1354498A - Process for the electrolysis of aqueous solutions by means of propulsive electrodes - Google Patents

Description

A. LUIB AND E. STEINBUCH. PROCESS FOR THE ELECTROLYSIS 0F AQUEOUS SOLUTIONS BY MEANS OF 'PROPULSIVE ELECTRODES.

APPLICATION FILED JAN. 29. 1913.

1,354,49 Patented Oct. 5,1920.

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ALPI-IONS LUIB AND EWALD STEINBUCH, OF MONTHEY, SWITZERLAND, ASSIGNORS TO SOCIETY OF CHEMICAL INDUSTRY IN BASLE, OF BASED, SVIITZERLAND.

PROCESS FOR THE ELECTROLYSIS OF AQUEOUS SOLUTIONS BY MEANS OF PROPULSIVE ELECTRODES.

Application filed January 29, 1913.

To all whom it may concern:

Be it known that we, ALPHoNs LUIB, a subject of the Emperor of Germany, and resident of Monthey, Canton of Vala-is, Switzerland, and EWALD STEINBUCH, a citizen of the Swiss Republic, and resident of Monthey, Canton of Valais, Switzerland, have invented new and useful Process for the Electrolysis of Aqueous Solutions by Means of Propulsive Electrodes, of which the following is a full, clear, and exact specification.

The invention relates to a process for the electrolysis of solutions in which gases are produced upon the electrodes. This process will be explained in detail by reference to the electrolysis of aqueous solutions of alkaline chlorids for the purpose of obtaining alkaline hydroxid and chlorin but the invention is also applicable in electrolysis for other purposes.

As is well known in order to secure good utilization of the current in electrolysis of alkaline chlorids when use is not made of fiuid metal cathodes and with as high a concentration of alkali in the catholyte as pos sible, it is necessary to propel the electrolyte in an evenst-ream in the direction from anode to cathode,-because the current of liquid in the opposite direction to the movement of the OH-ions tends to bear back these loss-causing ions toward the cathode. The movement of the electrolyte has been hitherto employed in two typical processes. The one rests on the fact that between superposed electrodes (anode above cathode) are formed horizontal layers of liquid, which can be kept at required distances from the electrodes by pouring in fresh electrolyte from above. A. disadvantage of this process is that the apparatus requires a comparatively large ground space, and that it is fundamentally necessary to have an even distribution of the fresh electrolyte over the whole cross section of the liquid, which it is not easy to attain, and that variations in pressure in the evolved gases adversely affect the utilization of the current. The other type is characterized by the use of so-called diaphragm cathodes in which the cathode side of the filter electrode is not immersed in electrolyte. The processes resting on this principle have the disadvantage that the hydraulical pressure on the anode- Specification of Letters Eatent.

Patented Got. 5, 1929.

Serial No. 744,937.

side which induces the flow across the diaphragm must quite carefully and that on account of deective contact between the diaphragm and the wlre netting cathode large contact resistances may easily arise and moreover the diaphragmcathode readily becomes incrusted.

The process described hereinafter, which is operated with electrodes arranged side by side, enables electrolyzers of very large current capacity to be mounted upon a small floor space and obviates the need for more or less complicated distributing devices for the electrolyte, since the even distribution of the liquid in the bath takes place quite automatically. Moreover it imports the advantages of the processes above mentioned, viz. the possibility of securing a high concentration of alkali and good utilization or yield of current. Further it is impossible for contact resistances or incrustations on the cathode to occur in this process since both electrode spaces are filled in the same way with electrolyte. The process rests on the use of the gases evolved upon the electrode concerned (in the case of electrolysis of alkaline chlorids on the use of the hydrogen formed on the cathode) for propelling the product of electrolysis produced on the said electrode (solution of alkali out of the electrode. chamber). For this purpose the cathode in electrolysis of alkaline chlorids) is arranged within a comparatively restricted cathode space formed of permeable material, for example by inclosing the cathode within a bag of substantially its own shape made of fine meshed asbestos fabric and protected in suitable fashion against any considerable distortion of form. Thus it will be attained that the cathode surface is a pretty large one relatively to the inclosed or confined volume of electrolyte. During the electrolysis a large quantity of hydrogen is commingled very intimately with a comparatively small quantity of liquid. The hydrogen separated in the relatively small cathode space produces on the surface of the electrolyte a considerable froth consisting of hydrogen bubbles in sheaths of alkaline solution carried up by them. The froth rises in the cathode space to a certain level and can overflow into a suitable receiving device. If the electrolyte is to be of electrolyte be regulated propelled to an important height above the level of the electrolyte, it is only necessary to narrow the upper part of the cathode space. In this narrowed upper part of the cathode space the froth rises and flows over into a suitable receptacle in which the hydrogen separates from the catholyte it has carried away. The cathode may have various shapes, for example it may be in the form of a rod, in which case the cathode space is preferably formed as a tube; or it may be in the form of a plate, in which case the cathode space takes the form of a narrow box.

Figures 1 and 2 of the accompanying drawing show as practical examples two forms of apparatus for performing the new process, in vertical sections. In the apparatus of Fig. 1 the cathode space is tubular and the cathode consists of the metal rods 1 which are fastened to an impervious upper part 2 which converges into a narrow tube at the top. The upper part 2 has an insulating coating on its outside, at least so far as it dips into the electrolyte, and. may conveniently serve as the current lead to the cathodes 1. Upon the upper part 2 a bag 3 of asbestos fabric, closed at the bottom, is fastened in such a manner that the hydrogen evolved in the electrolysis cannot escape between the bag and the upper part 2. A tube 4 of wire network inserted in the asbestos bag serves to brace it, the said tube being also, for simplicity, fastened to the upper part 2 so that the asbestos bag can be drawn over it like a stocking. In this case the wire network forms a part of the cathode. It must, however, be noted that this net-work is not necessary for the proper action of the cathode cell. The bracing device of the asbestos bag may equally well be separate from the circuit. The reduced portion 5 of the upper part 2 is secured inareceivin channel 6 (for the alkaline solution). he receiving channel 6 may suitably serve also as a current lead for a large number of separate cathode cells, a greater or less number of such cells being fastened to it as required. A hood 7 may be bent over the channel 6 so that the hydrogen will be collected beneath it. Obviously not only the cathode cell itself but the method of carrying away the catholyte and the hydrogen may be modified in various ways. For example the reduced tubular portion of the upper part may be bent downward in order to feed the solution into a receptacle at the side. Or, as in the case of Fig. 2 a tube broadened at the top into a funnel passes through the cathode space anlgl the alkali solution is led through this tu e.

The cathode cells together with desired anode cells are immersed in electrolytic baths which may be continuously supplied,

for example, with common salt solution. Chlorin is evolved at the anodes and in the cathode cells caustic soda solution and hydrogen are produced which together form the froth upon thesurface of the electrolyte in the cathode space. This froth rises in the upper part of the cathode spaces still farther and flows over into the collecting receptacle or receiving device. Since the hydrogen is developed in a uniform stream the removal of the catholyte out of the cathode chamber is very uniform also. To the extent that the cathode solution is propelled away, fresh electrolyte passes through the asbestos fabric sheathing the cathode; that is to say there is a uniform movement of liquid all over the surface of 'the permeable cathode sheath in the opposite direction to the movement of the OH- ions. It is therefore only necessary to supply to the spaceoutside the cathode cells an amount of fresh electrolyte corresponding with the amount of catholyte flowing away from the cathodes, in order to keep constant the alkali content of the solution which flows away.

Since each cathode cell automatically draws in the amount of electrolyte it needs, the fresh salt solution may be added at any desired point in the bath. For example an electrolyzer of 12000 amperes capacity needs only one point of supply for salt water. By the addition of larger or smaller amounts .of fresh electrolyte the concentration of the alkali solution which flows away can be altered at will. What we claimis:

1. A process for the electrolysis of solutions in which gas is evolved, at least at one of the two poles, consisting in raising the liquid decomposed by the electrolysis and surrounding -the.electrode corresponding to the said pole above the level of the electrolyte 1n the neighborhood of the said electrode, and 1n propelling simultaneously the said liquid out of the electrolyzer by the gas evolved at the said pole.

2. A process for the electrolysis of solutlons in which gas is evolved, at least at one of the two poles, consisting in producing automatically a continuous flow of the electrolyte toward the electrode corresponding to the said pole by raising the decomposed electrolyte in the space containing the said" electrode continuously by the gas evolved at this latter and propelling the same simultaneously by the said gas out of the said space.

3. The method of electrolyzing liquids to produce a solute and an evolved gas, which comprises the step of expelling the solute from the electrolytic cell by the buoyancy of the evolved gas.

4. In the electrolysis of solutions in which gas is evolved at least at one of the two poles, the method of-carrying ofi the decomand causing the gas generated at said pole to lift the adjacent portions of the electrolyte out of said restricted chambeigwhile fresh electrolyte flows in through said walls.

5. In the electrolysis of solutions iii-which hydrogen gas is evolved at the cathode, the

method of carrying off the decomposed electrolyte from and supplying fresh electrolyte to said cathode, which consists in placing said cathode in a restricted chamber projecting down into the electrolyte, said chamber having walls permeable to liquid, and causing the hydrogen gas generated at said cathodeto lift the adjacent portions of'the electrolyte out of said restricted chamber, while fresh electrolyte flows in through said walls.

6. In the electrolysis of alkali-haloid so lutions in which hydrogen gas is evolved at the cathode, the method of carrying off the decomposed electrolyte from and supplying fresh electrolyte to said cathode which consists in placing said cathode in a restricted chamber projecting down into the electrolyte, said chamber having its lower Walls permeable to liquid and its upper walls impermeable, and causing the hydrogen gas generated at said cathode to lift the adjacent portions of the alkali solution out of said. restricted chamber, while fresh electrolyte flows in through said permeable walls.

7. In the electrolysis of alkali-haloid solutions in which hydrogen gas is evolved at the cathode, the method of carrying oi the decomposed electrolyte from and supplying fresh electrolyte to said cathode which consists in forming the cathode in a series of parts separated from each other, placing said cathode so formed in a restricted chamber projecting down into the electrolyte, said chamber having its lower walls permeable to liquid and its upper walls impermeable, and causing the hydrogen gas generated at the parts of said cathode to lift the adjacent portions of the alkali solution out of said restricted chamber, while fresh electrolyte flows in through said permeable walls.

In witness whereof we have hereunto signed our names this eleventh day of Jan uary, 1913, in the presence of two subscribing witnesses.

ALPHONS LUIB. EWALD STEIN BUCH. Witnesses:

LOUIS HENRI Rossnn, J ULES EDOUARD MEYER.

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