U.S. patent application number 11/628988 was filed with the patent office on 2007-09-06 for electric circuit of an electrolyzer with bipolar electrodes and electrolysis installation with bipolar electrodes.
This patent application is currently assigned to SOLVAY (SOCIETE ANONYME). Invention is credited to Joachim Lange.
Application Number | 20070205110 11/628988 |
Document ID | / |
Family ID | 34946650 |
Filed Date | 2007-09-06 |
United States Patent
Application |
20070205110 |
Kind Code |
A1 |
Lange; Joachim |
September 6, 2007 |
Electric Circuit Of An Electrolyzer With Bipolar Electrodes And
Electrolysis Installation With Bipolar Electrodes
Abstract
Electric circuit of an electrolyzer with substantially vertical
bipolar electrodes, comprising at least one busbar (9, 10) that is
placed below and/or above the electrolyzer (3). Electrolysis
installation comprising such a circuit and at least one
electrolyzer (3) with vertical bipolar electrodes.
Inventors: |
Lange; Joachim; (Tervuren,
BE) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
SOLVAY (SOCIETE ANONYME)
Brussels
BE
B-1050
|
Family ID: |
34946650 |
Appl. No.: |
11/628988 |
Filed: |
June 8, 2005 |
PCT Filed: |
June 8, 2005 |
PCT NO: |
PCT/EP05/52653 |
371 Date: |
December 8, 2006 |
Current U.S.
Class: |
205/511 ;
204/230.2; 205/616 |
Current CPC
Class: |
C25B 9/66 20210101; C25B
9/65 20210101 |
Class at
Publication: |
205/511 ;
204/230.2; 205/616 |
International
Class: |
C25B 1/16 20060101
C25B001/16; C25B 1/26 20060101 C25B001/26 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 10, 2004 |
FR |
0406278 |
Claims
1-12. (canceled)
13. An electric circuit of an electrolyzer with bipolar electrodes,
comprising: at least one electric current line placed outside the
electrolyzer, wherein the electric current line includes at least
one busbar placed below and/or above the electrolyzer.
14. An electric circuit according to claim 13, wherein the busbar
is attached to a wall of the electrolyzer.
15. An electric circuit according to claim 14, wherein the wall is
a bottom wall of the electrolyzer.
16. An electric circuit according to claim 14, wherein the busbar
is a metal flat of which one of larger sides is attached to the
wall.
17. An electric circuit according to claim 15, wherein the busbar
is attached substantially to an entire surface of the wall.
18. An electric circuit according to claim 13, wherein the electric
current line further comprises two additional busbars attached
respectively to two side walls of the electrolyzer.
19. An electric circuit according to claim 13, wherein the electric
current line is positioned so as to generate an electromagnetic
field that is substantially symmetrical about the median vertical
plane of the electrolyzer.
20. An electric circuit according to claim 13, wherein the
electrolyzer comprises a line for continuous intake of an aqueous
electrolyte and a line for continuous removal of an aqueous
electrolyte.
21. An electric circuit according to claim 20, wherein the
electrolyzer comprises membranes that are selectively permeable to
cations, and that are inserted between the bipolar electrodes.
22. Use of the electric circuit according to claim 13, to reduce an
electromagnetic field in the neighborhood of the electrolyzer.
23. An electrolysis installation comprising: at least one
electrolyzer with bipolar electrodes, connected to an electric
circuit according to claim 13.
24. Use of the installation according to claim 23, for production
of chlorine and of aqueous sodium hydroxide solutions.
Description
[0001] The invention relates to electrolyzers with bipolar
electrodes, and especially to the electric power supply of such
electrolyzers.
[0002] The invention especially relates to an electric circuit for
supplying rectified electric power to an electrolyzer with bipolar
electrodes.
[0003] Electrolyzers with bipolar electrodes, supplied with DC
power, are commonly used in the electrochemical industry. Such
electrolyzers are commonly used to electrolyze aqueous solutions of
sodium chloride, in order to produce chlorine, aqueous sodium
hydroxide solutions or aqueous solutions of sodium chlorate.
[0004] Considering the high current densities employed in
electrolyzers with bipolar electrodes, rectified AC power is
generally substituted for DC power. Rectified AC power normally
presents pulses of which the frequency and amplitude depend on the
rectifier used. Accordingly, the electromagnetic field produced by
the rectified AC power is likely to generate induced currents which
may be relatively strong in certain industrial applications,
particularly with bipolar electrolyzers for the continuous
production of chlorine and of aqueous sodium hydroxide
solutions.
[0005] It is also well known that under extreme conditions, high
electromagnetic fields can have detrimental effects on the human
organism, especially those produced by rectified AC power, because
of the induced currents that they are liable to generate. It is
consequently important to take measures to protect the personnel in
the neighbourhood of the industrial installations or to reduce the
strength of the electromagnetic fields. Standards have moreover
been set in this sense, requiring the limitation of the strength of
electromagnetic fields in industrial premises. Among these
standards, European standard 89/391/EEC is particularly
stringent.
[0006] It is an object of the invention to provide an electric
circuit of novel design, to supply high strength electric current
to an industrial electrolyzer with bipolar electrodes.
[0007] It is a particular object of the invention to provide an
electric circuit with which the electromagnetic field in the
neighbourhood of the electrolyzer is reduced to a sufficiently low
value to meet the abovementioned European standard.
[0008] It is even more particularly an object of the invention to
reduce the strength of the magnetic field on walkways installed
along the side walls of electrolyzers with bipolar electrodes.
[0009] In consequence, the invention relates to an electric circuit
of an electrolyzer with bipolar electrodes, comprising at least one
electric current line that is placed outside the electrolyzer,
characterized in that the electric current line comprises at least
one busbar which is placed below and/or above the electrolyzer.
[0010] The invention relates more specifically to electrolyzers
with substantially vertical bipolar electrodes. Such electrolyzers
are well known in the art, where they are widely used for the
electrolysis of aqueous solutions of metal halides, particularly
sodium chloride. These electrolyzers are generally formed from a
succession of metal frames each comprising a bipolar electrode,
these frames being juxtaposed as in a filter press (Moderne
Chlor-alkali technology, Volume 3, SCI, 1986, chapter 13 "Operating
experience gained with the bipolar Hoechst-Uhde membrane cell";
Modern Chlor-alkali Technology, Volume 4, SCI, 1990, chapter 20
"Hoechst-Uhde single element membrane electrolyzer:
concept-experiences-applications"). The flames usually have a
square or rectangular profile, so that when they are juxtaposed, as
in a filter press, they form an upper wall, a lower or bottom wall,
and two side walls of the electrolyzer. The electrolyzer is
normally supplied with DC power or, more generally, with rectified
AC power. The DC or rectified AC power flows from a terminal of the
DC source or of the rectifier, through the bipolar electrodes, and
then returns to the other terminal of the DC source or the
rectifier, via an electric current line located outside the
electrolyzer. According to the invention, the said return electric
current line comprises at least one busbar that is placed below or
above the electrolyzer. The choice of placing the busbar below or
above the electrolyzer is dictated by considerations related to the
construction of the electrolyzer and the method of assembling the
bipolar electrodes. As a variant, the abovementioned electric
current line may comprise a busbar placed below the electrolyzer
and another busbar placed above the electrolyzer. According to
another variant, the electrolyzer may also comprise a plurality of
busbars below the electrolyzer and/or a plurality of busbars above
the electrolyzer. In practice, for considerations related to the
assembly and maintenance of the electrolyzer, it is generally
preferable for the abovementioned electric current line not to
comprise a busbar above the electrolyzer.
[0011] It has been found, all other things remaining equal, that
the electric circuit according to the invention significantly
reduces the electromagnetic field in the neighbourhood of the
electrolyzer with bipolar electrodes, chiefly along its side walls,
especially on walkways that are normally installed along the side
walls and are used by the operating and maintenance personnel. In
the discussion below, the expression "in the neighbourhood of the
electrolyzer" means the space along the side walls of the
electrolyzer, where the walkways used by the operating and
maintenance personnel of the electrolyzer are normally
installed.
[0012] In the electric circuit according to the invention, the
material of the busbar is not a critical factor for the definition
of the invention. It is generally made from copper, aluminium or
aluminium alloy.
[0013] In the electric circuit according to the invention, the
profile of the cross section of the busbar is not a critical factor
for the definition of the invention. It may, for example, be
square, rectangular, circular or polygonal.
[0014] In a first and particular embodiment of the electric circuit
according to the invention, the busbar has a rectangular profile
and is oriented so that its large sides are substantially
horizontal. It has been observed, all other things remaining equal,
that the selection of a rectangular section busbar, placed
horizontally below and/or above the electrolyzer, minrimises the
strength of the electromagnetic field in the neighbourhood of the
electrolyzer. It has also been observed that the decrease in the
electromagnetic field in the neighbourhood of the electrolyzer is
greater if the ratio of the thickness to the width of the busbar is
smaller. In practice, it is consequently preferable to use a metal
flat for the busbar. As a variant, a plurality of metal flats can
be used, placed side by side below and/or above the
electrolyzer.
[0015] It has further been observed, all other things remaining
equal, that the strength of the electromagnetic field in the
neighbourhood of the electrolyzer decreases as the busbar is
brought closer to the wall of the electrolyzer.
[0016] In consequence, in a second embodiment of the electric
circuit according to the invention, the busbar is placed
immediately next to a wall of the electrolyzer. In this embodiment
of the invention, the said wall of the electrolyzer is the lower or
bottom wall of the electrolyzer or its upper wall, depending on
whether the busbar is positioned below or above the electrolyzer.
In this embodiment of the invention, the expression "immediately
next to the wall of the electrolyzer" means that the distance
between this wall and the busbar is not more than five times
(preferably three times) the thickness of the busbar. Preferably,
this distance does not exceed the thickness of the busbar.
[0017] In a preferred variant of the abovementioned second
embodiment of the invention, the busbar is attached to the said
wall of the electrolyzer. In this preferred variant of the
invention, the busbar is advantageously a metal flat of which one
of the large sides is attached to the said wall, separated from the
wall only by the thickness of the necessary electrical insulation.
The metal flat may be attached to a portion of the surface of the
said wall. It is preferable for the metal flat to be attached to
substantially the entire surface of the said wall.
[0018] In a third particular embodiment of the invention, the
abovementioned electric line further comprises two additional
busbars, that are placed respectively immediately next to two side
walls of the electrolyzer. In this embodiment of the invention, the
expression "immediately next to" is identical to the definition of
this expression given in the second embodiment discussed above. All
other things remaining equal, the presence of the additional
busbars reduces the strength of the electromagnetic field in the
neighbourhood of the electrolyzer.
[0019] In this third embodiment according to the invention, the
additional busbars may have any shape compatible with the
construction of the electrolyzer. They may, for example, have a
square, rectangular, polygonal, oval or circular profile. The
additional busbars may also have the same profile or different
profiles and they may have the same dimensions or different
dimensions. In practice, however, it is preferable that the
additional busbars have the same profile and the same dimensions.
It is also preferable for the additional busbars to have a
rectangular profile and that they be attached by their large side
respectively to the two side walls of the electrolyzer.
[0020] In the third embodiment of the invention described above,
the respective dimensions of the additional busbars and those of
the or each busbar that is placed below and/or above the
electrolyzer are determined according to the way in which the
electric current is to be distributed to all these busbars. In
practice, it is recommended that the strength of the electric
current in the busbar positioned below and/or above the
electrolyzer differ by no more than 30% (preferably no more than
20%) from the strength of the electric current in each of the
additional busbars. It is preferable for the strength of the
electric current to be substantially identical in the busbar that
is positioned below and/or above the electrolyzer and in each of
the additional busbars.
[0021] In a fourth embodiment of the invention, which is especially
advantageous, the return electric current line of the electric
circuit is positioned so as to generate an electromagnetic field
that is substantially symmetrical about the median vertical plane
of the electrolyzer. In this embodiment, the aim (to generate an
electromagnetic field that is substantially symmetrical about the
median vertical plane of the electrolyzer) is achieved by
adequately dimensioning and positioning the or each busbar. The
choice of the optimal dimensions and the optimal position is
determined by a person skilled in the art, particularly according
to the shape and dimensions of the electrolyzer. In practice, this
result can generally be achieved by placing the busbar or the
busbars symmetrically about the median vertical plane of the
electrolyzer.
[0022] The electric circuit according to the invention
significantly reduces the electromagnetic field in the
neighbourhood of the electrolyzer with bipolar electrodes.
[0023] In consequence, the invention further relates to the use of
the electric circuit according to the invention, to reduce the
electromagnetic field in the neighbourhood of the electrolyzer.
[0024] The electric circuit according to the invention applies
specially to electrolyzers for the continuous electrolysis of water
or of aqueous solutions such as aqueous solutions of alkali metal
halides, especially of sodium chloride. In consequence, in a
preferred embodiment of the invention, the electrolyzer comprises a
line for the continuous intake of an aqueous electrolyte and a line
for the continuous removal of an aqueous electrolyte.
[0025] The invention applies in particular to electrolyzers for the
production of sodium chlorate by the electrolysis of aqueous
solutions of sodium chloride. The invention applies especially to
electrolyzers for the production of chlorine and of aqueous sodium
hydroxide solutions, by the electrolysis of aqueous solutions of
sodium chloride, these electrolyzers comprising membranes that are
selectively permeable to cations, and which are inserted between
the bipolar electrodes.
[0026] The electric circuit according to the invention applies to
any electrolysis installation incorporating at least one
electrolyzer with vertical bipolar electrodes.
[0027] In consequence, the invention further relates to an
electrolysis installation comprising at least one electrolyzer with
bipolar electrodes, connected to an electric circuit according to
the invention. The installation according to the invention may
comprise a single electrolyzer or a plurality of electrolyzers
connected in electrical series.
[0028] The invention relates in particular to the use of this
installation for the production of chlorine and of aqueous sodium
hydroxide solutions.
[0029] Particular features and details of the invention will appear
from the following description of the figures appended hereto,
which show a number of particular embodiments of the invention.
[0030] FIG. 1 shows an overall plan view of an electrolysis
installation prior to the invention.
[0031] FIG. 2 shows a schematic longitudinal elevation view of a
particular embodiment of the electrolysis installation according to
the invention.
[0032] FIG. 3 shows a vertical cross section on the plane III-III
of FIG. 2.
[0033] FIG. 4 is a view similar to that of FIG. 3, of another
embodiment of the installation according to the invention.
[0034] FIG. 5 is a preferred variant of the installation in FIG. 4.
In these figures, the same reference numerals designate identical
elements.
[0035] The electrolysis installation shown in FIG. 1 is prior to
the invention and does not conform to it. It comprises three
electrolyzers 1, 2 and 3 designed for the production of chlorine,
hydrogen and sodium hydroxide by the electrolysis of an aqueous
solution of sodium chloride. The electrolyzers 1, 2 and 3 are of
the vertical bipolar electrode type. They are formed by the
juxtaposition of vertical rectangular frames 4, each containing a
vertical bipolar electrode (not shown). The frames 4 are juxtaposed
as in a filter press. Membranes that are selectively permeable to
cations are inserted between the frames 4 to form alternating anode
and cathode chambers. The anode chambers of the electrolyzers 1, 2
and 3 communicate with a line (not shown) for the continuous intake
of an aqueous solution of sodium chloride. They also communicate
with a manifold (not shown) for the continuous removal of chlorine.
The cathode chambers of the electrolyzers 1, 2 and 3 communicate
with two manifolds (not shown) that serve respectively for the
continuous extraction of hydrogen, on the one hand, and of an
aqueous sodium hydroxide solutions, on the other.
[0036] The electrolyzers 1, 2 and 3 are coupled in electrical
series with a rectifier 5 of an AC power source, via an electric
circuit comprising, on the one hand, busbars 6 inserted between the
electrolyzers 1, 2 and 3 and, on the other, a return electric
current line 7, placed outside the electrolyzers 1, 2 and 3. The
electric circuit further comprises a bipolar switch 8.
[0037] In the electrolysis installation in FIG. 1, the return
electric current line 7 consists of a long busbar running along a
longitudinal side wall of the electrolyzers 1, 2 and 3.
[0038] In the electrolysis installation shown in FIG. 1, each of
the three electrolyzers 1, 2, and 3 may, for example, comprise 30
to 40 elementary electrolysis cells and the electric power supply
comprises, for example, a 520 V DC rectifier, capable of delivering
a current of between 8 and 20 kA. Depending on the surface area of
the electrodes, this may result in an anodic current density of 2.5
to 6 kA/m.sup.2 of anode area. However, these numerical values are
purely indicative and do not limit the scope of the invention and
the claims that follow.
[0039] When the bipolar switch is closed, rectified electric
current flows successively in the electrolyzers 1, 2, and 3,
through the bipolar electrodes and in the return line 7. This
electric current generates an electromagnetic field in the
environment of the installation.
[0040] The installation shown in FIGS. 2 and 3 conforms to the
invention. In these figures, only the electrolyzer 3 has been
shown. In the installation in FIGS. 2 and 3, the return electric
current line 7 comprises two busbars 9 and 10 that are placed below
the bottom wall 1 of the electrolyzer 3. The busbars 9 and 10 are
prismatic bars of a metal that is a good electrical conductor
(preferably copper or aluminium). These busbars are placed
symmetrically on each side of the median vertical plane X-X of the
electrolyzer. The busbars 9 and 10 are further placed in the
neighbourhood of the bottom wall 1 of the electrolyzer 3. The
layout of the busbars 9 and 10 in the way shown in FIG. 3 has the
effect of reducing the strength of the electromagnetic field on the
walkways 12 running along the side walls 13 of the electrolyzer 3
and which are intended for the electrolyzer maintenance
personnel.
[0041] All other things remaining equal, it has been found that the
strength of the electromagnetic field on the walkways 12 is reduced
more if the busbars 9 and 10 are closer to the mid-plane X-X and to
the bottom wall 1. It has also been observed that the strength of
the electromagnetic field on the walkways 12 is reduced by
decreasing the ratio of the thickness to the width of the busbars 9
and 10. It is accordingly preferable to use flats or horizontal
strips for the busbars 9 and 10.
[0042] In the embodiment shown in FIG. 4, the return electric
current line 7 comprises a metal flat or strip 14 that is attached
to the bottom wall 1 of the electrolyzer and that substantially
covers this entire wall.
[0043] In the installation in FIG. 5, the electric current line 7
comprises a metal flat 14 that is applied against the bottom wall 1
of the electrolyzer 3 and two additional busbars 15 and 16
positioned respectively along the two side walls 13 of the
electrolyzer 3. The two additional busbars 15 and 16 are
advantageously metal flats or strips that are attached to the side
walls 13.
* * * * *