CH216003A - Electrolysis process and electrolyser for continuous service. - Google Patents

Description

Electrolysis process and electrolyser - for continuous service. Electrolyzers in which a solid substance is formed at one of the electrodes, generally at the cathode, without adhering strongly to it, can be divided into two groups: those producing a solid substance of lower density than that of the electrolyser. 61electrolyte, and those producing a solid substance of higher density than that of the electrolyte. While the. electrolysers of the first category can be suitable for electrolysis in continuous service, since the solid substance collects at the surface of the bath from which it can be evacuated by simple gravity, the electrolysers of the second category could only function in continuous service if they were fitted with a mechanical device which continuously extracts from the bath the solid substance which is deposited at the bottom. However, the use of a device of this kind presents great difficulties of execution and exploitation, already in the case of aqueous electrolysis at normal temperature, and even more so in the igneous electrolysis in a neutral atmosphere. . This is why e61ectrolysis has not been carried out to date industrially in continuous service, when the solid substance produced is denser than the electrolyte and does not adhere strongly to the electrode, or does not adhere to it at all.

However, in large electrochemical operations, it is particularly desirable for the apparatus to operate in continuous service rather than by successive charges, so that handling, loss of time, loss of heat, waste, irregularities in the processing and quality of finished products, variations in power, etc. will be reduced to a minimum. If, for example, the @electrolysis has to be done away from the atmosphere to avoid @oxidation or the absorption of water vapour, the continuous service @would be considerably more advantageous than the service by successful charges. - sives.

The present invention relates to a continuous process for electrolysis in. which forms at one of the electrodes, without strongly adhering thereto, a solid substance denser than the electrolyte. Said electrode, revolving in the shape of an annular body of revolution with an axis of symmetry oblique with respect to the vertical and revolving only partly covered by the bath, rotates on its axis, such that this rotation has the effect of continuously remove the formed solid substance from the bath, thus facilitating the subsequent evaporation of this substance. <B>Im</B> the simplest mode for carrying out this vacuation consists in that the annular electrode, provided in its middle with an opening at a level higher than that of the electrolyte, slides the solid substance along a scraper to the opening, through which the substance flows by gravity.

The electrolyser for the implementation of this process can be executed in such a way that the rotating electrode constitutes the tank of the electrolyser, which would minimize the quantity of electrolyte used for the bath, as well as the dimensions of the device. Alternatively, the shaft of the rotating electrode could be hollow so that it could serve as an exit channel for the solid substance extracted from the bath.

Thus a new field of application is opened up to electrolysis in continuous service. The drawing shows, by way of example, an electrolyser for implementing the process. This apparatus is intended for the ignited electrolysis, in continuous service, of a molten metallic salt whose metal is denser than the electrolyte. fig. 1 shows a section of the electrolyser seen in gi1givation, while FIG. 2 1st shown in plan. The cathode a, on which the dissociated metal will be deposited, constitutes the tank of the electrolyser; its axis b is oblique with respect to the vertical e. The electrolyte d in which. The fanode is contained only in the lower part, represented at right, of the coneave cathode <I>a.</I> The scraper <I>f,</I> fixed in space, follows the internal shape of the the cnve. The cathode shaft g is a hollow shaft. The anode e is electrically connected to the positive pole of a low voltage electric current source, while the hollow shaft g is received by the brush h at the negative pole of this source. The electrolyser is contained in a heat-insulated envelope i.

The electrolyser works in the following way when the metal salt is, for example, zinc chloride electrolyzed at 400° C., at 1.9.6 volts. When current passes from anode e to cathode a through the RTI ID="0002.0274" WI="7" HE="4" LX="1276" LY="634"> zinc chloride bath melted d, the latter decomposes into a gas, chlorine, which escapes from anode e, crosses it and flows through pipe k, and into zinc which is deposited in the crystallized state on cathode a. . The e1eetrolyte d is renewed as and when measured by its dissociation; it arrives through the pipe p and the overflow can flow out through the channel g. The cathode, driven by a transmission 1, rotates slowly around its axis, gradually raising the deposited zinc out of the bath which only covers the surface m (fig. 2) of the cathode. Pressed against the scraper f, the crystals of zine accumulate against the latter and are forced by it towards the central opening n of the cathode, from where they fall through the interior of the hollow shaft g into the silo ä zinc o.

Thus the cathode serves both as an electrolyser tank and as a conveyor device extracting the metal from the bath and transporting it to the silo. As the metal crystals are stirred by the scraper f in their upward motion, electrolyte particles which may have been entrained disengage from them and squirt into the bath. Any adhesion of the crystals to the aethode can be avoided, for example by the choice of the material(s) of which it is made.

If the electrolysis is to take place in a neutral atmosphere, an will introduce the neutral gas inside the envelope i. As this space communicates with the silo o through the channel of the hollow shaft g, the silo will also contain inert gas capable of protecting the metallic crystals, for example until their cooling, against the harmful influences of atmospheric air. By causing the neutral gas to circulate in the free space reserved for the electrolyser and by maintaining the temperature of this gas at that desired for the electrolysis, an equality of temperature throughout the apparatus will be ensured. .

To avoid any mixture of inert gas with the gas released at the anode a, the anode will be surrounded by a collecting bell r, the edges of which, not electrically conductive, are immersed in the bath. The tightness of the gas release line produced will thus be ensured. It may be advantageous to give the filling electrolyte a higher flow rate than that which corresponds to the electrolytic dissociation, so that, on the one hand, the level of the bath remains strictly constant, on the other hand, a certain current of electrolyte settles to facilitate electrolysis.

If it is necessary to protect the bearings - not represented on the drawing - of the cathode shaft against the radiant heat of the electrolyser, they can be cooled by circulating water. arrange Jans 1st silo o. In the latter case, the extended shaft will only be hollow to a level slightly below that of the top of the silo, and will be provided with openings at this level for the flow of crystals into the silo. In both cases, the junction of the shaft to the cathode will be removable to facilitate disassembly.

The torsion moment exerted by the weight of the electrolyte on the hollow shaft can be suppressed by supporting the cathode under the bath by rollers, or by a ring arranged horizontally and mounted on balls.

The scraper, instead of being applied directly to the cathode, can be slightly raised, in order to leave a layer of the substance produced on the cathode when the latter is likely to protect it.

Instead of dropping the solid substance extracted from the bath through an opening located in the center of the cathode, an can remove it from the cathod by other means, mechanical) or electromagneti.ques.

The tank can very well also be independent of the cathode, for example be constituted by a cement tank in which partially immerses the crown of the cathode. In this case, the cathode will have no other weight to bear than that of the extracted substance.

The oathode in the form of a revolution can have any suitable profile or be composed of articulated parts; which, during rotation, are driven by RTI ID="0003.0277" WI="15" HE="4" LX="1421" LY="493"> slideways according to a given ehe min.

Claims (1)

CLAIM I: Continuous electrolysis process in which there is formed at one of the electrodes, without strongly adhering thereto, a substance, a solid denser than the electrolyte, characterized in that said electrode, kaut of the shape of an annular body of revolution with an axis of symmetry oblique with respect to the vertical, and being only partly covered by the baln, rotates on its axis,. in such a way that this rotation has the effect of causing the solid substance formed to come out of the bath continuously, thereby facilitating the subsequent evacuation of this substance. SUB-CLAIM 1. Process according to claim 1, characterized in that the annular electrode, provided in its middle with an opening at a level higher than that of the electrolyte, by rotating causes the solid substance the bong of a scraper to the opening through which this substance flows by gravity. CLAIM II: Electrolyser for carrying out the process according to claim I, characterized in that the rotary electrode in the form of an annular body of revolution with an axis of symmetry oblique with respect to the vertical constitutes the tank of 1 electrolyser. SORS-CLAIM 2. Electrolyser according to claim II, characterized in that the shaft of the rotary electrode Best is hollow so that it can serve as an exit channel for the solid substance extracted from the bath.