DE2248432A1 - ELECTROLYSIS PROCEDURE - Google Patents

Description

Patent attorneys Dipl.-Xng. E Weickmann,

Dipl.-Xng. H. "We ι c km an n, Dipl.-Phys. Dr .. IC. Fincke Dipl.-Ing. FAWEICKMANN, Dipl.-Chem. B. Huber

S MUNICH 86, POST BOX 860 820

MÖHLSTRASSE 22, NUMBER 48 39 21/22

<983921/22>

CASE: 186.082 "

DIAIlOKD SHAMROCK CORPOMiDIOIi 300 Union Commerce Bldg., Cleveland, Ohio 44115 / USA

"Electrolysis process"

The invention "relates to an electrolysis process, and more particularly a method for reducing the operating voltage of an electrolytic cell in which gas is generated at the anode.

A large number of electrochemical reactions are "known" in which electrical current flows from one anode to an opposite one Cathode is passed through an aqueous electrolyte, and in which gas development occurs on the anode surface. A few »few examples of such reactions are the electrolytic extraction of metals from aqueous solutions, the electrolysis of water and the formation of chlorine, alkali. alkalis and chemical compounds of these products. To the extent that by increasing the anode current density used in these processes, the rate of formation and the amount of Gas development, which also applies to the operating voltage of the cell. In all practical cases, at least initially this voltage increase is directly related to the increase in current density. However, it was found that the higher current densities, which help to increase productivity

"3098 18/10 19"

n a given electrolytic cell it is desirable that the voltage increases at a greater rate than theoretically expected, resulting in an increase in energy consumption per unit of product leads.

Attempts have been made to reduce this undesirable stress increase to stop speed. E.g. became according to certain known method of electrolyte with ultrasonic vibrations treated, which unfortunately had no noticeable effect.

It is therefore the aim of the invention to provide a method of reduction to provide the operating voltage of an electrochemical cell, which is particularly effective when the cell is operated at relatively high current densities.

It has now been found that when performing an electrolytic Reaction in which an electric current flows between an anode and an opposing cathode through a Electrolyte flows and gas development occurs at the anode, the operating voltage can be reduced by one sets the anode directly in high-frequency mechanical vibration.

As already described above, the invention is applicable to those electrochemical reactions in which an electrical Current with a voltage sufficient for the desired reaction is passed through an aqueous electrolyte and to leads to the development of gas or gases on the anode surface. Generally the gas released is either direct the desired product (e.g. chlorine) or a subsequent chemical reaction that leads to the desired product used (e.g. chlorine, which is converted to chlorate). However, the method according to the invention is the same Veise applicable to those cases where the gas released is an inevitable by-product and where the desired one The reaction takes place predominantly on the cathode surface (e.g.

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_ 3 -

Oxygen, which occurs at the anode in electrometallurgy). The advantages of the method according to the invention are "particularly clear at relatively high current densities at which the production speed is so high that considerable amounts of gas are released and the electrolyte decomposes rapidly enters the anode surface. These procedures where high Current densities applied are recently concurrent with the development of dimensionally stable anodes, the not subject to the usual decomposition and wear and tear in the case of increased current densities, e.g. graphite has become common property.

According to the invention, the anode is set into “high-frequency mechanical vibrations”. This expression ,, together with the expression "Direct" is intended to indicate that the anode itself, in particular the working surface of the anode, makes it vibrate is, which is preferably with an oscillation frequency of more than 6000, in particular more than 9000 vibrations per minute up to frequencies that can be referred to as ultrasonic frequencies (e.g. 20,000 oscillations per second). the Vibrations are transmitted directly to the anode and / or its carrying and holding devices, including the current conductors (busbars) transfer. It has been found that using other cell components such as the cell supports or the side walls or vibrate the electrolyte, there is essentially no effect.

The device used to produce the mechanical vibration is of secondary importance in the present invention, although it is extremely important from a practical point of view. It has been found that it is necessary for the vibrations to be transmitted continuously, since with an interruption of the. Oscillation movement, the operating voltage instantly rises to its previous excessively high value. For this reason, the vibration device should be selected taking into account its durability and ease of operation and maintenance. Typical devices of this type are those vibrators in which

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Compressed air is used to turn balls or rollers into unbalanced To move (unbalanced) rotation, which in turn has the consequence that associated devices start to vibrate.

The following example is intended to explain the invention further, without however, to limit them.

example

This example is intended to describe the effect of the method according to the invention on the electrolysis of an aqueous alkali metal halide solution in a cell which has a dimensionally stable anode and a moving (flowing) mercury cathode. The cell used is a horizontally aligned mercury cell in which an anode is used which is arranged above a cathode base plate made of steel and which is contained in a housing which encloses the electrolyte and the electrolysis products. The dimensionally stable anode consists essentially of titanium, is held by an anode frame and is connected to a copper busbar. A connecting link with which the anode can be lifted leads from the connection point with the busbar into the interior of the cell. The active working surface of the anode consists of a large number of elongated rod-like elements which are arranged in a plane parallel to the surface of the flowing mercury and are connected to the anode holding device via soldered-on secondary conductors. The surface of these titanium rods is coated with an electrically conductive, electrocatalytically active material, in this case a titanium dioxide / ruthenium oxide deposit. The anode / cathode spacing is 0.34-3 cm (0.156 inch). As the electrolyte, a sodium chloride solution is used at a concentration of 305 g / liter at an average cell temperature of 76 ⁰ C.

The attached drawing shows the relationship between the applied Anode current density and the operating voltage of the cell if the conditions given above are complied with. The first

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Curve (1) represents the theoretical linear relationship between the voltage and the current density under the given conditions. The curve (3) shows the anode current density plotted against the cell voltage actually achieved between the anode surface and the mercury was measured. The curve (2) shows the plot of the measured voltage for the various Current densities all of the conditions being the same as in the case of determining curve (3) except that the anode was vibrated mechanically.

The vibration was carried out by directly connecting a commercially available compressed air driven vibrator (Vibrolator Model BDR-16, Martin Engineering Co.) with the anode busbar. The vibrator was operated with a vibration frequency in the range of 9,000 to 11,000 vibrations per minute. the Point where the vibrator is connected to the copper busbar is not critical and equivalent results were obtained when the vibrator was connected to the anode as such and the anode frame.

The attached figure shows the considerable reduction in tension due to the application of the oscillatory movement, voltage reductions of up to 300 millivolts were observed.

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Claims (4)

Patent claims 1. Procedure for reducing the operating voltage at the implementation of an electrolytic heating in which an electric current flows between an anode and an opposite one Cathode is passed through an aqueous electrolyte and gas evolution occurs at the anode, thereby characterized in that the anode is set in high-frequency mechanical vibrations. 2. The method according to claim 1, characterized in that that one vibrates the anode with frequencies of 6000 vibrations per minute up to frequencies lying in the ultrasonic range offset. 3. A process for the electrolysis of alkali metal halide solutions, in which a current is passed between an anode and an opposing cathode with a current density which is sufficient that there is evolution of gas at the anode , characterized in that the operating voltage is reduced by the anode directly vibrated mechanically . 4. A process for the electrolysis of aqueous alkali metal halides in which a current is passed through the aqueous halide between an anode and an opposing cathode with a current density of more than 1.24 A / cm (8 amperes per square inch), characterized in that one the operating voltage is reduced by causing the anode to vibrate directly at high frequencies. 309818/1019