U.S. patent application number 10/493440 was filed with the patent office on 2004-12-16 for electrochemical half-cell.
Invention is credited to Bulan, Andreas, Gestermann, Fritz, Klesper, Walter, Pinter, Hans-Dieter.
Application Number | 20040251127 10/493440 |
Document ID | / |
Family ID | 7703440 |
Filed Date | 2004-12-16 |
United States Patent
Application |
20040251127 |
Kind Code |
A1 |
Bulan, Andreas ; et
al. |
December 16, 2004 |
Electrochemical half-cell
Abstract
The invention concerns an electrochemical half-cell for
preparing chlorine from aqueous alkali chloride solutions,
comprising an electrode chamber (17) designed to contain an
electrolyte. Said half-cell also comprises several gas pockets (26,
27, 28, 29) which are separated from the electrode chamber (17) by
a gas-diffusing electrode (5). The invention is characterized in
that said half-cell includes a support element (21), for supporting
the gas pockets (26, 27, 28, 29), which is adjacent over its entire
surface to the rear wall (20) of the pockets (26, 27, 28, 29) or
which constitutes the rear wall (20) of said gas pockets (26, 27,
28, 29).
Inventors: |
Bulan, Andreas; (Langenfeld,
DE) ; Gestermann, Fritz; (Leverkusen, DE) ;
Pinter, Hans-Dieter; (Wermelskirchen, DE) ; Klesper,
Walter; (Bergisch Gladbach, DE) |
Correspondence
Address: |
CONNOLLY BOVE LODGE & HUTZ LLP
SUITE 800
1990 M STREET NW
WASHINGTON
DC
20036-3425
US
|
Family ID: |
7703440 |
Appl. No.: |
10/493440 |
Filed: |
April 23, 2004 |
PCT Filed: |
October 11, 2002 |
PCT NO: |
PCT/EP02/11404 |
Current U.S.
Class: |
204/265 ;
204/277 |
Current CPC
Class: |
C25B 9/19 20210101 |
Class at
Publication: |
204/265 ;
204/277 |
International
Class: |
C25B 001/26 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 23, 2001 |
DE |
101 52 276.2 |
Claims
1. An electrochemical half-element, in particular for producing
chlorine from aqueous solutions of alkali metal chloride, at least
comprising an electrode space for receiving an electrolyte, the
electrode space having an electrolyte feed and an electrolyte
discharge, a gas space, formed from a plurality of gas pockets, for
receiving gas, the bottom gas pocket having a gas feed, a
connecting passage, which connects two gas pockets to one another
and through which the gas emerging from a lower gas pocket via an
outlet opening flows into a gas pocket above it via an inlet
opening, a gas diffusion electrode, which separates the electrode
space from the gas pockets, and a support element for supporting
the gas pockets, which support element bears against the back wall
of the gas pockets over its entire surface or forms the back wall
of the gas pockets.
2. The electrochemical half-element as claimed in claim 1, wherein
the support element is formed in the manner of a well.
3. The electrochemical half-element as claimed in claim 1 or 2,
wherein the support element is connected fixedly, to the half-shell
of the half-element.
4. The electrochemical half-element as claimed in claim 1, wherein
the support element is connected to the half-shell, via one or more
bearing elements.
5. The electrochemical half-element as claimed in claim 4, wherein
the bearing element is a trapezium profiled section or a Z profiled
section.
6. The electrochemical half-element as claimed in claim 1, wherein
the connecting passage ) is arranged on the support element.
7. An electrochemical half-element as claimed in claim 3, wherein
the support element is connected by welding.
8. An electrochemical half-element as claimed in claim 4, wherein
the support element is connected electrically conductively.
9. The electrochemical half-element as claimed in claim 2, wherein
the support element is connected fixedly, to the half-shell of the
half-element.
10. The electrochemical half-element as claimed in claim 2, wherein
the support element is connected to the half-shell, via one or more
bearing elements.
11. The electrochemical half-element as claimed in claim 3, wherein
the support element is connected to the half-shell, via one or more
bearing elements.
12. The electrochemical half-element as claimed in claim 2, wherein
the connecting passage is arranged on the support element.
13. The electrochemical half-element as claimed in claim 3, wherein
the connecting passage is arranged on the support element.
14. The electrochemical half-element as claimed in claim 4, wherein
the connecting passage is arranged on the support element.
15. The electrochemical half-element as claimed in claim 5, wherein
the connecting passage is arranged on the support element.
Description
[0001] The invention relates to an electrochemical half-element for
the electrochemical production of chlorine from aqueous solutions
of alkali metal chloride.
[0002] The use of gas diffusion electrodes in alkali metal chloride
electrolysis as oxygen-consuming cathodes is advantageously
effected with pressure compensation between the height-dependent
pressure of the sodium hydroxide solution in front of the gas
diffusion electrode and the constant pressure of the oxygen behind
the gas diffusion electrode, in the form of gas pockets, as
presented, for example, in EP-A-0 717 130.
[0003] In DE 19 646 950, the gas pockets are configured such that
they can be removed individually from the half-shell housing of the
half-cell. This has the drawback that in the event of all the
components of a half-cell being exchanged, for example for a
changeover operation, all the components, in particular the gas
pockets with their gas feeds and gas discharges, have to be
dismantled and reassembled individually. This leads to
unnecessarily long down times in the electrolyzer.
[0004] It is an object of the invention to provide an
electrochemical half-cell for the production of chlorine from
aqueous solutions of alkali metal chloride, in particular sodium
chloride, which simplifies exchange of the gas pockets.
[0005] According to the invention, the object is achieved by the
features of claim 1.
[0006] The electrochemical half-cell has an electrode space for
receiving an electrolyte. Furthermore, the electrochemical
half-cell has a plurality of gas pockets, the gas pockets being
separated from the electrode space by at least one gas diffusion
electrode. If appropriate, it is also possible for one gas
diffusion electrode to be provided per gas pocket. According to the
invention, the at least two gas pockets are supported by a common
support element, which bears against the back wall of the gas
pockets over its entire surface and/or forms the back wall of the
gas pockets. In this case, the support element according to the
invention in the half-cell separates the electrode space between
gas diffusion electrode and ion exchange membrane from the back
space, the electrode space and the back space being connected to
one another via one or more openings in the support element.
[0007] The advantage of the invention is that the support element
forms a module with the gas pockets, and this module can be
inserted into the half-shell housing of the half-cell and connected
to it, in particular by welding. Connecting the module comprising
support element and gas pockets to the half-shell, instead of
having to connect a plurality of individual gas pockets,
considerably simplifies installation of the gas pockets.
[0008] In a simple embodiment, the support element is an
electrically conductive plate, preferably made from nickel or a
nickel alloy. It would also be conceivable to use a frame-like
support element, although this would have a lower mechanical
stability than a support element in plate form and would therefore
be less advantageous.
[0009] The support element according to the invention preferably
forms the back wall of the gas pockets. However, it is also
possible for the gas pockets to be formed completely independently
of the support element and to be releasably connected to the
support element in such a manner that individual gas pockets or a
plurality of gas pockets together can be separated from the support
element and/or removed therefrom.
[0010] In a further preferred embodiment, the support element is
designed in well form, so that the support element completely
accommodates the gas pockets. In this case, it is particularly
preferable for the side walls of the support element to have a rim
which rests loosely on the rim of the half-shell of the
electrochemical half-cell.
[0011] In a particularly preferred embodiment of the invention, the
support element is connected to a housing, in particular
electrically conductively, via one or more bearing elements. In
this case, it is preferable to use a low-resistance electrically
conductive connection, as described for example in EP-A-1 041 176.
The bearing elements used are, for example, trapezium or Z profile
sections which are fitted to the back wall of the half-shell.
[0012] The invention is explained in more detail below on the basis
of preferred embodiments and with reference to the appended
drawings, in which:
[0013] FIG. 1 shows a diagrammatic longitudinal section through an
electrochemical half-cell,
[0014] FIG. 2 shows a diagrammatic cross section through the
half-cell illustrated in FIG. 1,
[0015] FIG. 3 shows a diagrammatic excerpt from a first embodiment
of a support element arranged in a housing,
[0016] FIG. 4 shows a diagrammatic excerpt from a second embodiment
of a support element arranged in a housing,
[0017] FIG. 5 shows a diagrammatic excerpt from a third embodiment
of a support element arranged in a housing,
[0018] FIG. 6 shows a diagrammatic, perspective excerpt from the
embodiment illustrated in FIG. 5, and
[0019] FIG. 7 shows a diagrammatic excerpt from a fourth embodiment
of a support element arranged in a housing.
[0020] The gas space can be divided into two or more gas pockets
26, 27, 28, 29 positioned above one another in a cascade
arrangement (FIGS. 1 and 2). The gas pockets 26, 27, 28, 29 are
usually separated from one another and open at the bottom toward
the electrolyte. The gas from the gas pockets 26, 27, 28, 29 passes
via outlet openings 10 into the back space, located behind the gas
pocket 26, 27, 28, 29, of the half-element 18. In this way, the
pressure in the gas pocket 26, 27, 28, 29 is kept in equilibrium,
via the outlet openings 10 to the electrolyte, with the pressure of
the liquid column of the electrolyte in the corresponding part of
the electrode space 17 located between the gas diffusion electrode
5 and the ion exchange membrane 4. The supply of gas to or
dissipation of gas from the respective gas pocket 26, 27, 28, 29
takes place via the gas inlet openings 9 or outlet openings 10. The
supply of gas to the bottom gas pocket 26 may, for example, take
place directly via a connection piece or an inlet 12.
[0021] The gas passes from the bottom gas pocket 26, via the outlet
openings 10, into the back space 18 of the half-element. Here, the
gas is collected by a gas-collection device, e.g. a gas bell 7, and
is passed via the gas inlet opening 9 into the gas pocket 27 above
it. From the gas pocket 27, the gas once again passes out of gas
outlet openings 10, via a gas bell 7, into the gas pocket 28 above.
The gas bells 7 are arranged on an outer side of a well-shaped
support element 2 according to the invention.
[0022] The electrolyte is introduced, for example, by means of a
distributor pipe 11 at the bottom of the half-element and then
flows upward in the half-element. The electrolyte also enters the
electrode space 17 through a compensation opening 13. In the
electrode space 17, the electrolyte flows upward until it reaches
the overflow opening 6. The electrolyte passes via the overflow
opening 6 into the half-element space 18 behind the gas pockets 26,
27, 28, 29, from where it can be discharged from the half-element
via an outlet 14, for example via a standpipe (not shown here).
[0023] The gas diffusion electrodes 5 are electrically conductively
connected to the half-shell 1, for example at webs 16. This should
be effected with a low resistance, as described for example in
DE-A-196 22 744. One of the possible design variants of this
low-resistance attachment is described in EP-A-1 041 176 and may be
effected, for example, by means of laser welding.
[0024] A first embodiment is illustrated in FIG. 3. In this case,
by way of example, a plate which has been inserted into the
half-shell and connected to the half-shell at the side walls of the
half-shell, for example by welding, forms the support element 2.
The plate is in this case connected to the half-shell 1 via bearing
elements 21. The gas collection devices 7 and the gas feed openings
and gas outlet openings can be fitted to the plate in the back
space.
[0025] Another alternative is illustrated in FIG. 4. The well-like
support element 2 may, as illustrated in FIG. 4, be fitted into the
half-shell 1. The well or support element 2 is fixedly connected to
the half-shell via trapezium or Z profile sections as bearing
element 21. The connection can be effected by conventional forms of
contact, such as for example welded or soldered joints. Moreover,
the well 2 is connected to the half-shell 1 at its side walls. In
the back space, the gas collection devices 7 and gas feed openings
and gas outlet openings may be arranged on the outer side 19 of the
back wall 20 of the well 2.
[0026] As illustrated in FIGS. 5 and 6, the well may particularly
preferably be installed in such a way that it rests loosely on a
rim 23 of the half-shell 1 and is connected to the half-shell 1 via
the bearing elements 21. The connection should have a low
resistance. This can be effected, for example, by welding,
soldering or clamping connections.
[0027] The sealing of the gas pockets 26, 27, 28, 29 with respect
to the back space of the half-shell 1 is effected by means of the
seal 3, which seals off the half-shell 1 with the ion exchange
membrane 4.
[0028] Another design variant is illustrated in FIG. 7. In this
case, the space behind the well 2 is surrounded by a dedicated
sheet-metal construction 22 which is in half-shell form and serves
as a bearing element, so that the gas collection devices and
electrolyte supply and distribution and gas/electrolyte discharge
from the half-shell can be installed therein. The bearing element
22 is connected to the part serving as support element 2, for
example by means of a weld seam 25 and via webs 24.
* * * * *