DE2344647A1 - ELECTRODE - Google Patents

Description

HETALLGESELLSCHAFT Frankfurt / M., September 3rd, 73

Public company DrOz / KSchu

Prov. No. 7251 LC

electrode

The invention relates to a vertically arranged electrode for electrolysis taking place with gas formation.

In the electrolysis of liquids and the formation of Gaseous products result in difficulties as very quickly due to concentration polarization and checkout transport conditional problems occur. This is especially true when the gases are very sparingly soluble in the electrolyte are.

In the case of horizontally arranged electrodes, attempts have been made to remedy the situation by connecting the electrode with a large number cylindrical holes or slits are provided, which serve to remove the chlorine gas as quickly as possible (DT-OS 1 667 812, 1 792 183, GB-PS 1 229 402). Gas passage cross-sections in the order of magnitude between 15 and 35% are common. ”Due to the arrangement of holes or slits, the gas rises to the electrolyte surface by the shortest possible route.

A further development with regard to the design of the passage channels is described in DT-GM 7 207 894. Here the passage channels should be at least close to and towards a surface of the electrode. be extended. In particular Venturi-like shaped channels are provided.

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Electrodes that work in a vertical position are preferably ribbed, corrugated, perforated or made porous, so the gas or the gas-liquid dispersion can be removed and replaced by new liquid (A.T. Kulm, Industrial Electrochemical Processes, Elsevier Publishing-Company, Amsterdam, London, New York (1971) p. 602).

However, these known proposals allow a "flawless, i.e. undisturbed, electrocirculation not. In particular, gas-liquid dispersion is not sufficiently prevented detected by the downward flowing liquid and thus conveyed back into the lower electrode space will. The result is considerable overvoltages, which ultimately result in a low level of energy and increased "./arm development" impact. The inadequately fast gas discharge also creates local overheating phenomena, can seriously damage the electrodes and nearby diaphragms.

The object of the invention is to provide an electrode, which does not have the known disadvantages and, in particular, a perfect gas discharge without constructive effort and electrolyte circulation guaranteed.

The object is achieved in that the vertically arranged electrode for electrolysis taking place with gas formation according to the invention has an inactive area 2 running from top to bottom on the gas generating side, at least 2 cm wide and at most 20% of the electrode surface, which is surrounded by at least one delimitation 3 extending downwards from the top is separated from the active area 4.

The inactive area separated from the active electrode surface enables perfect reflux

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of the electrolyte completely or at least largely freed from gas into the lower cell space. It will be particular a mutual disturbance of the upward flow of gas-electrolyte suspension and downward flow of the electrolyte prevented.

The inactive area can be maintained in various ways. For example, it can be made of a previously active electrode part by covering it with a plastic film or Applying a plastic paint can be created. Another possibility is to have two active electrode parts to be attached to a connecting insulating piece, so that a loss of previously active electrode surface is avoided will.

According to a third embodiment, the inactive area can be obtained by removing the surface area in question before activation of the entire electrode is covered and thus not activated. The latter working method is for example sv / ei se for electrodes based on titanium metal with surface activation by platinum metals or platinum metal oxides particularly advantageous.

When dimensioning the inactive area, the size is the Electrode to be considered. Starting from the observation that the width of the inactive area is from hydrodynamic Reasons must not be less than 2 cm, comparatively small-area electrodes with a - on the total surface related - are equipped with a larger percentage of inactive areas than large-area electrodes. That means, that small electrodes stressed an inactive area in the upper stressed area, while large electrodes stressed in the lower Should have area. The inactive area is preferably at least 5 / ό of the electrode surface.

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The boundaries separating the inactive from the active area can be made with suitable shaping processing the electrode material itself, provided that the inactive Area facing "application is also inactive.

As a rule, however, it is easier to produce the boundary by attaching plastic profiles on the electrode.

In the case of electrodes with small surface dimensions, a continuous inactive area is generally sufficient. at For large-area electrodes, however, it is advantageous to divide this area several times. However, each of the Partial areas occupy at least 5? S of the electrode surface: Two or three sub-areas -are also with larger lileL-: tro & e: generally sufficient.

In the case of electrodes which develop gas on both sides and which must therefore have an inactive area on both sides, it is advantageous to provide these opposite one another. In the embodiment of the invention with at least a connecting element for the active electrode areas, this configuration is usually already in terms of manufacturing technology given.

The geometric shape of the electrode according to the invention is largely arbitrary. For example, it can be quite angular, be square or round.

In the case of rectangular and square electrodes, it is useful to give the inactive area the shape of a continuous strip which - if a division is not provided - lies approximately in the middle of the area. If the inactive area is subdivided several times, one becomes

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generally choose the position of the strips so that; 3 the Electrode surface is divided into, for example, three or four areas of approximately the same size.

With round electrodes, it is advisable to place the inactive area on the circumference of the electrode. Possibly a strip in the middle can also be provided.

The electrode according to the invention can be used for all electrolyses in which gas is present on at least one electrode is being developed. Use cases are, for example

Electrolysis of hydrochloric acid and common salt using the diaphragm process, the reduction electrolyses for extraction of non-ferrous and precious metals from salt solutions, chlorate electrolysis and the electrowinning of peroxyacid ..

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- ό -

The invention is illustrated by way of example using the figures and examples and explained in more detail.

Show it

Figure 1 is a plan view of a rectangular electrode

FIG. 2 the top view of a round electrode *.

The electrodes marked 1 v / iron one in Figure 1 strip-shaped, in Figure 2 circular inactive Area 2. The inactive area is active due to plastic profiles 3 applied to the electrode Area 4 separated.

In the embodiment according to Figure 2, the plastic profiles not brought down to the bottom of the electrode space, because on the one hand the electrolyte is briskly flowing downwards held by the centrifugal forces on the circumference of the electrode space, which is also circular in shape, and on the other hand due to the vertical upward flow of the gas bubbles their entry into the backflowing electrolyte in the lower Area of the electrode space can not take place.

In both figures, the drawn out H: express the haste downward flow of the electrolyte practically free of gas bubbles and the broken arrows die upward flow of the gas-electrolyte suspension. The inactive area of the electrode is shown hatched.

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Execution example game
Example 1

An NaCl solution with a concentration of 320 g / l was investigated in a diaphragm test cell. The Elelctrolytter.peratur was 85 ⁰ C, the pH -. * / Ert of the incoming NaCl-solution was 4.

An untreated graphite plate with the dimensions 80 cm high and 120 cm wide served as the anode. The current density was set to 1.2 kA / m.

At the beginning of the operating period, in which the abnode burn-off is still negligibly small, a cell voltage of 3.2 V measured.

Example_2! Invention)

The experiment according to Example 1 was repeated. However, an anode is used, which is centered with a strip-shaped, 10 cm wide and 1 cm deep area inactivated with asplit was provided. The inactive area was against the active area on both sides with PVC square profiles, which in the in height up to the diaphragm and in length up to 5 cm in each case from the top and bottom edge of the anode, delimited.

At a current density of 1.2 kA / m, a Cell voltage of 2.9 volts measured. This corresponded to a voltage gain of 300 mV.

- 8 claims

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Claims (6)

23U647 Claims Vertically arranged electrode for draining with gas formation Electrolyses, labeled through one on the gas generating side from above downward, at least 2 cm wide, ::. a :: i-egg 20 ^ 3 of the electrode surface occupying inactive Area (2) separated from the active area (4) by at least one boundary (3) extending downwards from above. is separated. 2. Electrode according to claim 1, characterized in that that the inactive area (2) occupies at least 5 / ö of the electrode surface. 3. Electrode according to claim 1 or 2, characterized in that that the inactive area (2) is subdivided several times and the individual areas at least Occupy 5 / a of the total electrode surface. 4. Electrode according to claim 1, 2 or 3, characterized in that that the inactive area (2) of at least one connecting element for the active lead electrode areas (4) formed v / ird. 5. Electrode according to one or more of claims 1 to 4, characterized in that when gas is generated Both inactive areas (2) are opposite on both electrode surfaces. 509817/0370 23ΑΑ6Λ7 6. Electrode according to one or more of claims 1 bic 53, characterized in that the height of the boundary (3) for the inactive area (2) extends to the next electrode or to the diaphragm. 509817/0370 Blank page