EP0685575B1 - Electrode for electrolysis cells - Google Patents

Description

The invention relates to an electrode for electrolytic cells, in particular for mercury-chlor-alkali electrolytic cells. with power supplies via rods or power supply bolts and Power distributors in the form of upright standing, spaced flat profiles, the activated electrode parts arranged on their lower edge with perpendicular to them made of upright flat profiles with vertical or almost vertical outer sides are connected by welding, the activated electrode parts from a larger one There are a number of individual elements as the current distributors and the activated electrode parts with a gap of at least 2 mm to each other.

From US-A-35 07 771 it is known that vertically arranged on the underside of power distributors, activated electrode parts standing upright and arranged parallel to each other Use sheet metal profiles, the wedge-shaped lower edges seen in cross section exhibit; The sheet profiles are in the area of their U-shaped upper edge with openings through which gas and used solution emerge upwards.

GB-A-10 68 992 describes an anode arrangement for chlor-alkali electrolysis in which the underside of power distributors is provided with electrode parts made of titanium sheet profiles, the have wedge-shaped tapered lower edges around a gas bubble discharge from the anode area to improve.

It proves to be problematic that the known anode arrangements are due to the ascending gas bubbles along the active electrode surfaces Form of an electrolyte-gas mixture the electrochemical conversion (ion exchange) in the can hinder the upper part of the electrode.

Furthermore, from US-PS 40 22 679 an electrode for mercury-chlor-alkali electrolysis cells known with power supplies via rods or power supply bolts, which has spaced-apart flat profiles that are perpendicular to their lower edge is connected to them arranged activated electrode parts, the activated electrode parts consist of a larger number of individual elements than the electrical parts and the Individual elements seen in cross section has a tapering lower edge, which is essentially is formed exhaust gas; proves to be problematic in such circular or semicircular configurations the removal of the gas bubbles generated during electrolysis, since this on the one hand the ion exchange in the electrolytic gap between the semicircular profiles and hinder the mercury cathode, on the other hand, have no rapid withdrawal option, so that a kind of gas bubble cushion can be expected in the lower area of the profile anode got to; furthermore, the height of the activation coating on the electrodes is proportional high, so that the areas with precious metals are relatively far removed from the electrode gap Substances are provided, but practically no electrochemicals Contribute implementation.

From US Pat. No. 4,364,811 an anode for mercury-chlor-alkali electrolysis cells is included Power supply via a rod or bolt known with the electrode parts activated Flat profiles above the current distribution and transverse current distributors is connected in the form of rectangular profiles; here too there is a risk of formation of a Gas cushion in the electrode gap, or below the horizontally running lower edge of the Electrode elements, so that a rapid electrochemical conversion with sufficient ion supply is not possible and implementation is hindered due to gas generation; even if the current is distributed favorably over three conductor levels with optimal dimensions Flat profiles is possible here, but the question of rapid electrochemical implementation arises in the electrode gap and their hindrance by gas bubble generation or formation of a gas cushion.

The object of the invention is so the electrodes or anodes for the chlor-alkali electrolysis cell to design that the gas extraction from the area of the electrode gap is promoted and an interface between the anode and the electrolyte in the area of the electrode gap that is as free as possible from gas bubbles is available; In addition, a high energy utilization in Electrolysis can be achieved by low electrode voltage.

The object is solved by the features of claim 1.

It proves to be particularly advantageous that there is practically no swirling of the electrolyte-gas mixture more takes place in the electrode gap, so that advantageously the electrode voltage can be kept low.

In a further advantageous embodiment, the triangle or wedge-shaped element of the Bottom edge an angle in the range of 30 to 90 °, in particular in the range of approx. 60 ° a particularly rapid gas extraction of the electrolytic reaction can take place. More beneficial Refinements are specified in the subclaims. The thickness is preferably of the activated electrode parts in the range from 1.5 to 2.5 mm.

The subject matter of the invention is explained in more detail below with reference to FIGS. 1 and 2.

FIG. 1 shows an electrode, the upper part of the cross section of which tapers upwards is, while the lower part is tapered downwards.

Figure 2 shows schematically an electrode with electrode elements according to Figure 1, the two upper current conductor levels are recognizable.

Figure shows schematically the use of the electrodes 1,2 according to the invention with a base angle Alpha in the area of the lower edge 3 of 60 °, whereby due to the Bottom edge 3 isosceles extending partial triangle 4 by means of the electrocatalytic applied Layer 5 rapid electrolytic conversion and rapid removal any gas bubbles that may occur by means of a gap 6 between two adjacent electrodes 1,2 resulting chimney effect. The gas bubbles are symbolic here with reference numerals 7 provided. In practice, this is the case with chlor-alkali electrolysis Electrode elements 1 and 2 arranged in a gap 6 of at least 2 mm to each other due to a large number of small gas bubbles based on the principle of the mammoth pump, an upward one Let flow arise, which for a rapid gas removal from the critical Electrode gap 6 ensures and thus a relatively high efficiency of the electrolytic cell enables; 1 is about the taper in the area of the partial triangle 4 of Bottom edge 3 also the upper part of the electrodes 1, 2 tapers upwards, so that here the resulting gas bubbles 7 without contact or any influence the exchange of materials with the electrocatalytically active upper side of the electrodes rising up; due to the upward funnel-like expansion of the distance of the Both electrodes 1 and 2, the gas bubbles 7 can rise vertically while the active areas 11, 12 of the electrodes 1, 2 in the rear area from the gas bubbles not more covered so that the electrochemical conversion in the upper part of the electrode largely without obstructing the gas bubbles flowing in from below. Consequently can also the rear side surfaces of the activated electrode parts without hindrance participate in the electrolysis process by gas bubbles.

The electrodes 1, 2 with the current distributors 17 of the second are on their upper side 14 Layer connected, which are shown here only broken for a better overview.

Figure 2 shows schematically the electrode according to the invention with its three current collector levels of which the two upper levels are formed from rectangular flat profiles 17, 18, which stand upright on top of each other and are perpendicular to each other so that none Obstruction of the gas flow from the area of the electrode gap 6 can occur; on the lower edges of the current distributors 17 of the second level are the electrode elements 1, 2 fixed by welding at an angle of 90 ° so that the gas discharge of the resulting Gas bubbles are not hindered. With regard to the electrode structure of the two upper levels and the power supply line is referred to U.S. Patent 4,364,811.

Claims (3)

1. An electrode for electrolysis cells, in particular for mercury chloroalkali electrolysis cells, with current supplies over bars or current supply pins and current distributors in the form of flat sections standing on edge, arranged at a distance from each other, which on their lower edge are connected by welding with activated electrode parts, arranged perpendicularly with respect to them, of flat sections standing on edge with vertical or approximately vertical outer faces, wherein the activated electrode parts consist of a greater number of individual elements than the current distributors, and the activated electrode parts are arranged with a gap of at least 2 mm with respect to each other, characterised in that the activated electrode parts (1, 2), viewed in cross-section, have lower edges narrowing in a wedge shape/prismatically, which lower edges, viewed in the cross-section of the section, have a triangular lower part which is held by an upwardly narrowing upper part.
2. An electrode according to Claim 1, characterised in that the wedge-shaped lower edge is formed from two planes which intersect each other at an angle in the range of 40 to 100°.
3. An electrode according to Claim 1 or 2, characterised in that the electrode parts (1, 2) of the third plane are arranged running parallel to each other at a distance in the range of 1.5 to 3 mm.

Images