Title of Invention

ELECTROLYTIC CELL COMPRISING AN INTERIOR TROUGH

Abstract The invention relates to an electrolysis device for halogen gas production from an aqueous alkali halide solution in several plate-type electrolysis cells stacked and arranged side by side, with electrical contacts, each of the cells with a housing consisting of two half-shells made of electrically conductive material, said housing being equipped with devices for feeding electrolytic current and the electrolysis plant reactants and devices for discharging electroIytic current and discharging the electrolysis products, with anodic electrode, cathodic electrode and a membrane arranged therebetween, built-in components being fitted in at least one of the two half- shells and permitting a defined increase in the liquid level and thus minimising the remaining gas volume accordingly. The built-in components are arranged in such a manner that they form an internal trough parallel to the said membrane and arranged horizontally, an interspace thus being provided between the trough and the membrane and an interspace between the trough and the electrolysis chamber, a part of which is located above the membrane, said trough having at least one opening communicating with the interspace between said trough and the upper side of the electrolytic chamber, and at least one outlet. (Drawing to be published with abstract: Figure 1)
Full Text Electrolytic cell comprising an interior trough
[0001] The invention relates to an electrolytic device for halogen gas production
from aqueous alkali halide solution in several plate-type electrolytic cells stacked and
arranged side-by-side and provided with electrical contacts, each of the cells provided
with a housing consisting of two half-shells made of electrically conductive material and
having external contact strips on at least one housing rear wall, said housing being
equipped with devices for feeding electrolytic current and electrolysis reactants and for
discharging electrolytic current and products, with anodic and cathodic electrodes that
evolve gas during normal operation and with gas outlets.
[0002] Electrolytic cells are well known and a typical example of state-of-the-art
technology is described in DE 196 41 125 A1. A device of this type ensures adequate
gas separation in the upper rear zone by means of a guide plate arranged towards the
membrane and which is in addition used for sufficiently wetting the electrolytic
membrane during the electrolyser operation. However, difficulties in maintaining such a
wetting may arise from interruptions of the electrolyser operation.
[0003] In order to protect the standard coatings it is possible to polarise the cell
during downtime periods such as start-up, shut-down, service interruptions or failures.
This applies whenever the cell must be filled and heated prior to starting operation.
When shutting down the electrolyser it is likewise imperative that the polarisation be
maintained until the anodic liquid is purged from chlorine and cooled down.
[0004] In case the electrolyser membrane is not sufficiently flooded in the upper
cell zone, the single element technology as described in DE 195 41 125 A1 provides
for a liquid level adjustment in the half-shells via the overfall weir of the standpipe. The
polarisation current must not be selected arbitrarily but has to exceed a given
threshold.
[0005] Depending on the type of material used for the standpipe, such as metal or
PTFE, and on its chamfered angle, gas zones more than 20 mm high may be

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established in the upper part of the cell in the cold state. Investigations revealed that
the membrane installed in the electrolytic cell is not gas-tight but presents a diffusion
rate that depends on the molecular size, irrespective of the differential pressure
between the anodic and cathodic chambers. As hydrogen gas is generated at the
cathode and chlorine or oxygen gas are generated at the anode depending on the
current density, hydrogen gas diffuses in the anodic chamber on account of its
substantially smaller atomic size. The amount of the anodic gas build-up when the
polarisation is switched on must be such that the explosion limit of the
chlorine/hydrogen mixture or oxygen/hydrogen mixture is assuredly not reached. The
production rate of oxygen or chlorine gas to be set is directly proportional to the
polarisation current and also depends on the membrane surface area in the gas
chamber. An electrolyser as described in DE196 41 125 A1 requires a polarisation
current of approx. 28 A, said device having PTFE standpipes and a gas chamber 20
mm high in the warm state and up to 30 mm high in the cold state of the electrolyser.
[0006] The object of the invention, therefore, is to design a device that overcomes
the aforementioned difficulties and that requires lower polarisation currents.
[0007] The object of the invension is achieved by providing built-in components to
be installed in the electrolyser in such a manner that the liquid level is raised so as to
minimise the volume of the remaining gas zone and to reduce the minimum current
required for polarisation. This method permits the filling of the cell element over the top
edge of the membrane so that the minimum current required for polarisation with the
element filled, hence in the absence of a hydrogen gas chamber contacting the
electrolytic membrane, is achieved even by currentless polarisation.
[0008] The invention provides for built-in components to be installed in the
appropriate electrolytic chamber and suited for playing a role in the hydraulics and
dynamics of the liquid/gas mixture. Said built-in components are characterised in that
• they form an internal trough located in parallel to the electrolytic membrane and
arranged horizontally,
• an interspace is provided between the trough and the electrolytic membrane,
• an interspace is also formed between said trough and the upper side of the
electrolytic chamber, a part of which is located above the membrane,

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• said trough has at least one opening communicating with the interspace between
the trough and the upper side of the electrolytic chamber,
• said trough has at least one outlet.
lt is possible to provide the internal trough either on the anodic or cathodic side or on
both the anodic and cathodic sides and it serves as an overfall weir for liquid or gas.
Moreover, it may be arranged along the whole cell width, merely in the inlet and outlet
sections or ir any other section therebetween.
[0009] In a particular embodiment of the invention, the interspace between the
trough and the upper side of the electrolytic chamber is implemented as a gap.
preferably of 2 to 3 mm width. In a particularly preferred embodiment such gap is
inclined both outwards and upwards with respect to the horizontal plane as seen from
the electrolytic membrane. The gap may also have a variable width, the adjacent
interfaces being straight, corrugated or arched.
[0010] In a further embodiment of the invention, the interspace between the trough
and the upper side of the electrolytic chamber is equipped with a perforated plate
arranged parallel to the electrolytic membrane or slightly inclined therefrom so that the
holes have the function of a perforated diaphragm.
[0011] According to a further embodiment of the invention, the interspace
between the trough and the upper part of the electronic chamber is equipped with a
duct bundle, the axes of the ducts lying in the plane of the interspace. The ducts need
not be circular but may also be honeycomb-structured. The greater stiffness of this
structure constitutes a particular advantage.
[0012] A further embodiment of the invention provides for beads, webs, nipples or
other spacers to be installed in the interspace between the trough and the upper part of
the electrolytic chamber, said spacers being used to geometrically delimit said
interspace and to secure the implementation of the defined flow pattern.

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[0013] According to a further embodiment of the invention, the members which
form the trough, inlets, outlets and related supports are at least partly coated to ensure
corrosion protection.
[0014] A further advantage of the invention is that the lower part of the trough also
assumes the function of gas pre-sepa ration which calms down the flow and dampens
or even prevents pulsation.
[0015] A leak of the trough will not necessarily jeopardise the operation of the
electrolytic cell since the cell built-in components are sealed inside the cell, which
represents a further advantage.
[0016] The device according to the invention can be retrofitted as an assembly into
existing plants, which is a further advantage.
[0017] The device designed in accordance with the invention, moreover, has a
particular advantage in that the anodic and cathodic rear walls need not specific
geometric requirements, hence they may be straight, corrugated or inclined.
[0018] In the following, the invention will be illustrated by means of an example.
Fig. 1 shows a cross-sectional view of the upper part of an electrolytic cell provided
with the troughs described in this invention and arranged on the anodic and cathodic
sides.
[0019] The two half-shells of the electrolytic cell are formed by anode rear wall 1
and cathode rear wall 2 and firmly damped by means of bolted connection 3. The
anodic electrode 4 of liouver-type design and the cathodic efectrode 5 are arranged
approximately in the centre of the electrolyser by means of support and fixing elements
not shewn in the Figure, the electrolytic membrane 6 being located between electrodes
4 and 5.
[0020] The anode side shows the trough 7 designed as a folded sheet 8. The
chlorine gas that forms at the louver-type anodic electrode 4 and the electrolytic liquid
simultaneously enter as a foam the interspace 9 located between sheet 8 dellmiting
trough 7 and electrode 4. The major part of the foam babbles collapses underneath
trough 7 so that they enter pre-separated into trough 7 via interspace 9 and gap 10.

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[0021] In the event of a shutdown, the amount of Iiquid admitted to the cell is such
that its level reaches the upper end 11 of gap 10. This method permits to completely
wet membrane 6 on the anode side, which reduces the quantity of hydrogen diffusing
from the cathode to anode side.
[0022] The cathode side shows trough 12 designed as bent sheet 13. The
hydrogen gas formed at the flat cathodic electrode 5 and the electrolytic liquid
simultaneously enter the interspace 14 located between sheet 13 delimiting trough 12
and electrode 5 as foam bubbles. The major part of the foam bubbles burst underneath
trough 12 so that they are pre-separated and enter trough 12 via interspace 14 and gap
15.
[0023] In the event of a shutdown, the amount of liquid admitted to the cell is such
that its level reaches upper end 16 of gap 15. This method permits wetting of the
complete membrane 6 on the cathodic side, which prevents hydrogen diffusion from
the cathodic to the anodic side.

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[0024] List of reference numerals
1 Anode rear wall
2 Cathode rear wall
3 Connection
4 Anodic electrode
5 Cathodic electrode
7 Trough
8 Sheet
9 Interspace
10 Gap
11 Upper edge
12 Trough
13 Sheet
14 Interspace
15 Gap
16 Upper edge

7
Claims
1. Electrolytic cell for halogen gas production comprising:
- a housing of two half-shells made of electrically conductive material:
- anodic and cathodic electrodes (4, 5) with an electrolytic membrane (6) arranged
therebetween:
- at least one of said half-shells being provided with built-in components permitting a
defined increase in the liquid level over the top edge of said etectrolytic membrane (6), said
built-in components forming art internal trough (7) having one major surface parallel to the
electrolytic membrane (6) and spaced therefrom by a first interspace (9, 14):
- a second interspace (10, 15) inclined both outwards and upwards with respect to the
horizontal plane as seen from said electrolytic membrane (6) being established between said
trough (7) and the upper side of said at least one half-shell, said trough (7) having at least
one opening communicating with said second interspace (10,15) and at least one outlet.
2. The cell of claim 1 wherein the highest point of said second interspace (10, 15) is
located above said top edge of said electrolytic membrane (6).
3. The cell of claim 1 or 2 wherein said trough (7) is arranged horizontally.
4. The cell of any one of the preceding claims wherein said second interspace (10, 15) is
implemented as a 2 to 3 mm wide gap.
5. The cell of any one of claims 1 to 4 wherein said second interspace (10, 15) is
implemented as a variable gap provided with straight, corrugated or arched delimiting
surfaces.
6. The cell of any one of the preceding claims wherein said second interspace (10, 15) is
equipped with a perforated plate arranged in parallel to said electrolytic membrane (6) or
slightly inclined therefrom.
7. The cell of any one of claims 1 to 5 wherein said second interspace (10, 15) is
equipped with duct bundles, the axes of said ducts lying in the plane of said second
interspace (10, 15).
8. The cell of claim 7 wherein said ducts are circular or honeycomb-structured.
9. The cell of any one of claims 1 to 5 wherein a multiplicity of beads, webs, nipples or
other spacers are installed in said second interspace (10, 15)
10. The cell of any one of the preceding claims wherein said built-in component forming
the trough (7) are at least partly coated to ensure adequate corrosion protection.
11. Electrolytic device for halogen gas production from aqueous alkali halide solution
comprising plate-type electrolytic cells stacked and arranged side by side, at least one of
said electrolytic cells being a cell of any one of the preceding claims.


The invention relates to an electrolysis device for halogen gas production from an
aqueous alkali halide solution in several plate-type electrolysis cells stacked and
arranged side by side, with electrical contacts, each of the cells with a housing
consisting of two half-shells made of electrically conductive material, said housing
being equipped with devices for feeding electrolytic current and the electrolysis plant
reactants and devices for discharging electroIytic current and discharging the
electrolysis products, with anodic electrode, cathodic electrode and a membrane
arranged therebetween, built-in components being fitted in at least one of the two half-
shells and permitting a defined increase in the liquid level and thus minimising the
remaining gas volume accordingly.
The built-in components are arranged in such a manner that they form an internal
trough parallel to the said membrane and arranged horizontally, an interspace thus
being provided between the trough and the membrane and an interspace between the
trough and the electrolysis chamber, a part of which is located above the membrane,
said trough having at least one opening communicating with the interspace between
said trough and the upper side of the electrolytic chamber, and at least one outlet.
(Drawing to be published with abstract: Figure 1)

Documents:


Patent Number 218976
Indian Patent Application Number 00950/KOLNP/2005
PG Journal Number 16/2008
Publication Date 18-Apr-2008
Grant Date 16-Apr-2008
Date of Filing 24-May-2005
Name of Patentee UHDENORA TECHNOLOGIES S.R.L.
Applicant Address VIA BISTOLFI, 35, 20134 MILAN, ITALY
Inventors:
# Inventor's Name Inventor's Address
1 DULLE, KARL HEINZ MARIE CURIE STRASSE 20-D-50399 OLFEN (DE)
2 WOLTERING, PETER SANDWEG 18 - D-48485 NEUENKIRCHEN(DE)
3 FUNCK, FRANK SUNDERPLATZ, 6-D-45474 MULHEIM(DE)
4 WOLLNY, MARTIN BRUCKSTRASSE 19-D-58455 WITTEN(DE)
5 KIEFER, RANDOLF LANGENDREER STRASSE 52A-44892 BOCHUM(DE)
6 STEINMETZ, THOMAS CHEMNITZER STRASSE 73-D-44139 DORTMUND(DE)
7 JANOWITZ, KOSMAS FALTERWEG 27-D-44269 DORTMUND(DE)
8 BECKMANN, ROLAND DORFSTRASSE 125B-D-44534 LUNEN(DE)
9 DRESEL, TORSTEN SONDERBURGSTRASSE 2C-D-58093 HAGEN(DE)
10 HARTZ, HANS-JOACHIM ISINGGRUND 27-D-59427 UNNA(DE)
PCT International Classification Number C25B 15/08
PCT International Application Number PCT/DE2003/003431
PCT International Filing date 2003-10-16
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 102 49 508.4 2002-05-24 Germany