U.S. patent application number 14/382709 was filed with the patent office on 2015-02-05 for anode and method of operating an electrolysis cell.
This patent application is currently assigned to OUTOTEC (FINLAND) Oy. The applicant listed for this patent is OUTOTEC (FINLAND) OY. Invention is credited to Michael H. Barker, Ville Nieminen, Henri Virtanen.
Application Number | 20150034491 14/382709 |
Document ID | / |
Family ID | 49115992 |
Filed Date | 2015-02-05 |
United States Patent
Application |
20150034491 |
Kind Code |
A1 |
Nieminen; Ville ; et
al. |
February 5, 2015 |
ANODE AND METHOD OF OPERATING AN ELECTROLYSIS CELL
Abstract
The invention relates to an anode for electrowinning process in
an electrolytic cell, and the method of operation thereof, having
cell walls and a cell bottom for holding an electrolyte and
electrolyte feeding means, which anode comprises a hanger bar for
supporting the anode, a conducting rod for distributing the
current, an anode body having at least partly conductive structure.
The anode body allows electrolyte penetration and is at least
partly covered by electrocatalytic coating, when in connection with
the anode there is arranged a non-conductive element, which is
restricted to the conductive structure of the anode body, at least
from its one side, and which non-conductive element is arranged at
a distance A from the electrolyte surface level, when the
non-conductive element provides a means for attaching the anode to
the cell.
Inventors: |
Nieminen; Ville; (Turku,
FI) ; Barker; Michael H.; (Pori, FI) ;
Virtanen; Henri; (Pori, FI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
OUTOTEC (FINLAND) OY |
Espoo |
|
FI |
|
|
Assignee: |
OUTOTEC (FINLAND) Oy
ESpoo
FI
|
Family ID: |
49115992 |
Appl. No.: |
14/382709 |
Filed: |
March 6, 2013 |
PCT Filed: |
March 6, 2013 |
PCT NO: |
PCT/FI2013/050242 |
371 Date: |
September 3, 2014 |
Current U.S.
Class: |
205/292 ;
204/280; 204/284; 204/292 |
Current CPC
Class: |
C25D 3/38 20130101; C25C
7/02 20130101; C25D 17/12 20130101 |
Class at
Publication: |
205/292 ;
204/280; 204/284; 204/292 |
International
Class: |
C25D 17/12 20060101
C25D017/12; C25D 3/38 20060101 C25D003/38 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 9, 2012 |
FI |
20120075 |
Claims
1. An anode (1) for electrowinning process in an electrolytic cell
(4) having cell walls (2) and cell bottom (3) for holding an
electrolyte and electrolyte feeding means (6), which anode
comprises of a hanger bar (7) for supporting the anode, a
conducting rod (8), for distributing the current to the anode, an
anode body (9) having at least a partly conductive structure, which
anode body allows the penetration of the electrolyte and is at
least partly covered by electrocatalytic coating, characterized in
that in connection with the anode (1) there is arranged a
non-conductive element (10, 12, 14), which is restricted to the
conductive structure of the anode body (9) at least from its one
side and which non-conductive element is arranged at a distance A
from the electrolyte surface level (11), when the non-conductive
element provides a means for attaching the anode to the
electrolytic cell (4).
2. Anode according to the claim 1, characterized in that the length
A is arranged to be between 0.3-2 meters.
3. Anode according to the claim 1 or 2, characterized in that the
non-conductive element (10, 14) of the anode (1) is formed by
excluding part of the anode body (9) from electrocatalytic
coating.
4. Anode according to claim 3, characterized in that at least 2
percent of the anode surface is excluded from electrocatalytic
coating.
5. Anode according to any of the claims 1-2, characterized in that
the non-conductive element is made of at least one non-conductive
object (12) attached to the anode body (9).
6. Anode according to any of the claims 1-5, characterized in that
the anode is being attached into the electrolytic cell (4) by
anchoring elements (13) located in the cell bottom (3).
7. Anode according to any of the claims 1-5, characterized in that
the anode is being attached into the electrolytic cell by anchoring
elements (13) located in the cell wall.
8. Anode according to any of the claims 1-5, characterized in that
the anode is being attached into the electrolytic cell by anchoring
elements (13) located in the electrolyte feeding means (6).
9. Anode according to any of the claims 1-5, characterized in that
the anode is being attached into the electrolytic cell by anchoring
elements (13) attached to the cathode next to the anode (1).
10. Anode according to any of the claims 1-9, characterized in that
the conductive structure of the anode body (9) consists of a mesh
structure, including preferably at least one of the following; Ti,
Ni, Pb, Ta, Zr or Nb.
11. Anode according to claim 1, characterized in that the
electrocatalytic coating is consists of a Pt-group metal oxide or a
mixture of metal oxides.
12. Anode according to any of the claims 1-11, characterized in
that the height B between the upper part (16) of the non-conductive
element (10,12,14) and anode bottom surface (15) is arranged to be
between 0.05-0.3 m.
13. A method of operating an electrolysis cell to be used in the
electrowinning of metal, when metal is electrodeposited on the
cathode surface from an electrolyte solution (5) in an electrolytic
cell (4) having cell walls (2) and cell bottom (3), which cell (4)
contains electrolyte (5) where anodes (1) and cathodes are immersed
in alternating fashion, in which the anode is supported by a hanger
bar (7) on the conducting rod, which distributes the current to the
anode, when the anode body (9) has at least partly conductive
structure allowing the penetration of the electrolyte and an
electrocatalytic coating, characterized in that the anode is
attached inside the electrolytic cell (4) by a non-conductive
element (10, 12, 14) arranged in connection with the anode (1),
which non-conductive element is restricted to the conductive
structure of the anode body at least from its one side and which
non-conductive element is arranged at a distance A from the
electrolyte surface level (11).
14. Method according to claim 13, characterized in that the anode
is attached into the electrolytic cell bottom (3) by anchoring
elements (13).
15. Method according to claim 13, characterized in that the anode
is attached into the electrolytic cell wall (2) by anchoring
elements.
16. Method according to claim 13, characterized in that the anode
is attached into the electrolyte feeding means (6) by anchoring
elements (13).
17. Method according to claim 13, characterized in that the anode
is attached into the cathode next to the anode by anchoring
elements (13).
18. Method according to any of the claims 13-17, characterized in
that the electrolyte is fed at least from two manifolds in the
cell, when the other one is at the is bottom of the cell.
19. Use of the anode according to any one of the claims 1 to 12 in
the electrowinning of the metal copper, Cu.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a new kind of anode to be used in
electrowinning. The invention also relates to a method of operating
an electrolysis cell to be used in the electrowinning of
metals.
[0002] Electrowinning is a process where a metal dissolved in an
electrolyte is reduced on a cathode by means of an electrical
current. In electrowinning a current is passed through the anode
through the electrolyte solution containing the metal value so that
the metal value is extracted as it is deposited in an
electroplating process onto the cathode. When an electrical current
is applied to the sulfate based electrolysis system, metal is
precipitated on the surface of the cathode and water decomposes on
the anode where acid and oxygen are formed. Electrowinning takes
place in an electrolytic cell that contains a number of anodes and
a number of cathodes arranged in an alternating manner. The
commercial use of electrowinning requires a large number of
cathodes and anodes in a single electrolytic cell. One type of
anode used in electrowinning has been lead based anode, which could
have a negative effect on the quality of copper deposited. One
significant disadvantage of using such lead based anodes is that
during electrowinning operations small amounts of lead are released
from the surface of the anode, which causes the undesirable
particulates to be suspended in the electrolyte. In addition, the
lead sludge must be cleaned periodically from the cell bottom e.g.
every 45 to 90 days, and during this time the electrowinning cell
is not producing metal.
[0003] One issue in electrowinning processes is a rather high cell
voltage leading to increased energy consumption. Due to high energy
consumption in electrowinning and low corrosion resistance of
previous anodes, there has been a need to investigate better anode
materials in electrowinning. Mixed metal oxide (MMO) coated anodes
consist of conductive mixed metal oxide coatings on valve metal
substrates, usually titanium or nickel. Dimensionally Stable Anode
or DSA.RTM. is a well-known type of MMO-coated anode. When the
MMO-coated anodes are used in sulfate based electrowinning the cell
can be operated at a lower cell voltage than when lead based anodes
are used. One type of dimensionally stable anode is presented in
patent publication US4134806, where the idea is to stabilize
current distribution between the DSA anode and cathode by
thickening the DSA anode structure in the border areas. Publication
US 20100276281 presents the anode for use in electrowinning cells.
According to the publication the electrode includes a hanger bar
and an electrode body including at least one conductor rod and a
substrate, a connection coupling the hanger bar and the at least
one conductor rod, and a seal isolating the connection. An
electrode comprises a hanger bar including at least one recessed
hole, and an electrode body comprising at least one conductor rod
press fit into said at least one recessed hole and a substrate
coupled to said conductor rod.
[0004] Past research and development efforts have focused on ways
to increase production capacity per plant area for copper
electrowinning, which directly impacts on the cost-effectiveness of
the electrowinning process. To increase the production of the
electrolysis plant and cell, it is desirable to increase the
current density during electrolysis, and achieve a higher
deposition rate of copper on the cathodes. The current density on
the cathode side is limited by the quality of the copper deposited,
as due to the increased overvoltage on the cathodes more impurities
are deposited with increasing current density. In addition,
increasing the current density also leads to an increase in the
corrosion rate of lead from lead anodes and consequently more lead
circulates in the electrolyte and lead can be included in the
cathodes, necessitating an increase in the frequency of cell
cleaning to control lead and decreasing the production rate.
[0005] Due to high investment and operating costs of the
electrolysis plants and cathode processing plants comprising of a
crane and stripping machines, which are combined in the so-called
tankhouse, attempts have been made for quite some time at
increasing the economic efficiency of both the refining
electrolysis and the extraction/electrowinning electrolysis. This
largely depends on the efficiency of the electrolysis as well as on
the number of the cathode movements and therefore on the amount of
copper deposited per cathode. One way to decrease tankhouse capital
expenses is by increasing the length of cathode, thus increasing
the production capacity per cell without the need to increase the
current density, the plant area or the number of electrolytic
cells.
[0006] Publication WO 2005/080640 presents a process for
electrochemically winning or refining copper, where the idea of the
invention is to increase the copper loading per cathode. To
increase the economic efficiency of such processes and plants, it
is proposed in accordance with the publication to immerse at least
one cathode into the electrolyte over a length of at least 1.2
meters during operation of the electrolysis.
[0007] Still problems can occur when using cathodes with great
length. When using lead anodes with jumbo cathodes i.e. cathodes of
great length, warping of the anode during electrowinning may occur
and cause short circuits to the process. There can be problems
especially with the first and last anodes in a cell, with current
flowing only on one side of the anode, which may cause warping or
creep deformation of the anode. Warping leads to an increased
number of short circuits and a lower current efficiency. If lead
anodes are used with jumbo cathodes, more frequent cell maintenance
is needed to remove the lead sludge from the cell. In addition, for
an even current distribution it is beneficial to position the
anodes at equal distances from the cathodes. In order to avoid such
issues or problems there has been a need to develop a new kind of
anode to be used with long cathodes with a rigid structure and
located in the right position in the cell.
OBJECTIVE OF THE INVENTION
[0008] An object of the invention is to provide an anode for
electrowinning process, especially when the anode is to be used
with "jumbo" cathodes having a great length (of 1.2 m or longer)
and for avoiding problems stabilizing the position of the anode
inside the electrolytic cell.
SHORT DESCRIPTION OF THE INVENTION
[0009] The anode and the method of the invention are characterized
by the definitions of independent claims. Preferred embodiments of
the invention are defined in the dependent claims.
[0010] The invention presents an anode for an electrowinning
process in an electrolytic cell having cell walls and a bottom cell
for holding an electrolyte and electrolyte feeding means. The anode
comprises of a hanger bar for supporting the anode, a conducting
rod for distributing the current to the anode, an anode body having
at least partly conductive structure, which anode body allows the
penetration of the electrolyte and is at least partly covered by
electrocatalytic coating, when in connection with the anode there
is arranged a non-conductive element, which is restricted to the
conductive structure of the anode body at least from its one side
and which non-conductive element is arranged at a distance A from
the electrolyte surface level, when the non-conductive element
provides a means for attaching the anode to the cell. By using of
anode presented in this invention many problems in a process for
electrowinning can be avoided. According to the embodiment of the
invention the length A is arranged to be between 0.3-2 meters,
which depends on the size of the electrodes and process
parameters.
[0011] According to the one embodiment of the invention the
non-conductive element of the anode is formed by excluding part of
the anode body from electrocatalytic coating, for example at least
2 percent of the anode surface is excluded from electrocatalytic
coating.
[0012] According to one embodiment of the invention the
non-conductive element is made of at least one non-conductive
object attached to the anode body.
[0013] According to another embodiment of the invention the anode
is being attached into the electrolytic cell by anchoring elements
located in the cell bottom, in the cell wall, in the electrolyte
feeding means or attached to the cathode next to the anode.
[0014] According to the invention the conductive structure of the
anode body consists of a mesh structure, including preferably at
least one of the following; Ti, Ni, Pb, Ta, Zr or Nb and the
electrocatalytic coating consists of a Pt-group metal oxide or a
mixture of metal oxides.
[0015] According to another embodiment of the invention the height
B between the upper part of the non-conductive element and anode
bottom surface is arranged to be between 0.05-0.3 m.
[0016] The invention also describes a method of operating an
electrolysis cell to be used in the electrowinning of metal, when
metal is electrodeposited on the cathode surface from an
electrolyte solution in an electrolytic cell having cell walls and
a cell bottom, which cell contains electrolyte where anodes and
cathodes are immersed in alternating fashion, in which the anode is
supported by a hanger bar on the conducting rod, which distributes
the current to the anode, when the anode body has at least a partly
conductive structure allowing the penetration of the electrolyte
and an electrocatalytic coating, when the anode is attached inside
the electrolytic cell by a non-conductive element arranged in
connection with the anode, which non-conductive element is
restricted to the conductive structure of the anode body at least
from its one side and which non-conductive element is arranged at a
distance A from the electrolyte surface level. According to the
embodiment of the invention the anode is attached into the
electrolytic cell bottom by anchoring elements.
[0017] According to the different embodiments of the method the
anode is attached into the electrolytic cell wall, into the
electrolyte feeding means or the cathode next to the anode by
anchoring elements.
[0018] According to one embodiment of the invention the electrolyte
is fed at least from two manifolds in the cell, when the other one
is at the bottom of the cell.
[0019] According to one embodiment of the invention the anode could
be used in the electrowinning of the metal copper, Cu.
[0020] There are many advantages of using the anode according to
the invention. The anode can easily be attached in the cell, anode
warping is avoided, good mixing effect of electrolyte inside the
cell is reached by using the anode according to the invention. Also
copper growth on the cathode surface will be more even. When using
a flow-through anode with electrolyte feeding vertically in the
middle of the cell, good electrolyte mixing is obtained and metal
ion concentration gradients can be avoided. Better anode attaching
and anchoring in the cell can be achieved by coating only part of
the surface of the anode with the electrocatalytic coating.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] The accompanying drawings, which are included to provide a
further understanding of the invention and constitute a part of
this specification, illustrate embodiments of the invention and
together with the description help to explain the principles of the
invention. In the drawings:
[0022] FIG. 1 schematically shows an anode according to the
invention, where the non-conductive part of the anode is part of
the anode body.
[0023] FIG. 2 shows another embodiment of the anode, where the
non-conductive element is attached to the anode.
[0024] FIG. 3a schematically shows an anode according to the
invention, where the anchoring elements are located on the
electrolytic cell bottom.
[0025] FIG. 3b schematically shows an anode according to the
invention, where the anchoring elements are located on the
electrolytic cell walls.
[0026] FIG. 3c schematically shows an anode according to the
invention, where the anchoring elements are located on the
electrolyte feeding means.
[0027] FIG. 3d schematically shows an anode according to the
invention, where the non-conductive element is attached to the
anode and attached to the anchoring elements.
DETAILED DESCRIPTION OF THE INVENTION
[0028] Reference will now be made in detail to the embodiments of
the present invention, examples of which are illustrated in the
accompanying drawings.
[0029] FIGS. 1 and 2 shows an anode 1 for electrowinning of metals,
such as copper in an electrolytic cell 2 having cell walls 3 and
cell bottom 4 for holding an electrolyte 5. The anode comprises of
a hanger bar 7 for supporting the anode on the conducting rod 8,
which distributes the current to the anode, an anode body 9 having
at least partly conductive structure allowing the penetration of
the electrolyte and an electrocatalytic coating. According to the
invention there is arranged a non-conductive element 10, 12, 14 in
connection with the anode 1 at a distance A from the electrolyte
surface level 11, when the distance A is arranged to be at an
interval 0.3-2 meter. This depends on the size of the anode used.
The non-conductive element 10, 12, 14 provides means for attaching
the anode 1 inside the electrolytic cell 4, which is important when
using long anodes with long cathodes. When using long cathodes, it
is important that the anode is fixed and rigid in its place and
possible warping of the anode is prevented. The non-conductive
element consists of any suitable material that is not electrically
conductive and could be selected based on the process needs. It is
possible that the non-conductive element could consist of several
pieces or is made from one piece.
[0030] FIGS. 3a, 3b, 3c and 3d describe different ways for
attaching the anode inside the electrolytic cell 4. The
non-conductive element 10, 12, 14 of the anode provides means for
attaching the anode 1 for example in the cell bottom 3, to the
walls 2 or to the electrolyte feeding means 6 by anchoring elements
13, which are attached to the non-conductive elements. It is also
possible to attach the anode next to the cathode inside the
electrolytic cell (not shown in figures). When the anode is
attached to the cathode by using non-conductive element, it means
that it acts as a spacer, which is known to be used to align the
electrodes and separate them at a fixed distance from each other in
order the electrolytic process to function. One way for attaching
the anode is presented in FIG. 3b, when the anchoring elements 13
are located in both sides of the anode, which anchoring elements
are attached to the non-conductive element 14 and from its other
side to the electrolytic cell walls 2. By attaching the anchoring
elements 13 to the electrolyte feeding means 6, as presented in
FIG. 3c, it saves space inside the electrolytic cell.
[0031] When using a long anode, it is important that the anode is
rigid and straight and positioned from even distance from the
adjacent cathodes. According to the invention the anode can be
anchored inside electrolytic cell 4 by supportive anchoring
elements 13, which could be of any shape (e.g. V-neck) and suitable
for attaching them to the non-conductive elements 10, 12, 14. The
electrolytic cell may be used for electrowinning of several metal
values. An electrowinning cell as described herein may be
configured for the extraction of a variety of metal values. FIG. 3d
schematically shows an anode, where the non-conductive element 12
is attached to the anode and attached to the anchoring elements 13.
It is possible that the non-conductive element is attached to the
cathode next to the anode, when the non-conductive element
functions as a cathode guide, i.e. during cathode harvests it
guides the cathode into the correct position and prevents any
contact between the cathode and the anode body.
[0032] According to the invention the distance between electrolyte
surface level 11 and the non-conductive element, meaning length A
is arranged to be in interval 0.3-2 meter when the height B between
the upper part 16 of the non-conductive element 10,12,14 and anode
bottom surface 15 is arranged to be between 0.05-0.3 m. Then the
immersion of the anode is enough to be used with long cathodes. One
way is to form the non-conductive element 10, 12, 14 of the anode 1
is by excluding the anode body 9 from electrocatalytic coating when
at least 2 percent of the anode 1 surface is excluded from
electrocatalytic coating. When part of the surface is left without
conductive electrocatalytic surface, electric current can be
shielded and anode can be placed on the cell bottom without
problematic edge deposit growth on the cathode bottom. The
conductive structure of the anode body consists for example of a
mesh structure allowing the penetration of the electrolyte, when
the anode mesh consists of preferably one of the following metals;
Ti, Ni, Pb, Ta, Zr or Nb. Catalytic coating preferably consists of
Pt-group metal oxide.
[0033] It is apparent to a person skilled in the art that as
technology advanced, the basic idea of the invention can be
implemented in various ways. The invention and its embodiments are
therefore not restricted to the above examples, but they may vary
within the scope of the claims.
* * * * *