Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
  • C25C7/06—Operating or servicing
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C1/00—Electrolytic production, recovery or refining of metals by electrolysis of solutions
  • C25C1/06—Electrolytic production, recovery or refining of metals by electrolysis of solutions or iron group metals, refractory metals or manganese
  • C25C1/08—Electrolytic production, recovery or refining of metals by electrolysis of solutions or iron group metals, refractory metals or manganese of nickel or cobalt
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
  • C25B13/00—Diaphragms; Spacing elements
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
  • C25C7/02—Electrodes; Connections thereof
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25C—PROCESSES FOR THE ELECTROLYTIC PRODUCTION, RECOVERY OR REFINING OF METALS; APPARATUS THEREFOR
  • C25C7/00—Constructional parts, or assemblies thereof, of cells; Servicing or operating of cells
  • C25C7/04—Diaphragms; Spacing elements

Definitions

• the present invention relates to a method of operating an electrolysis cell in electrowinning of metal, wherein cathode plates are arranged in cathode frames.
• the cathode plate and the cathode frame are enclosed in a diaphragm bag so as to form a cathode bag assem- bly.
• the cathode bag assemblies and anode plates are arranged in the electrolyte in an electrolysis cell in an alternating and consecutive manner.
• the invention relates to a cathode frame configured to re ⁇ tain a cathode plate and a diaphragm bag which enclos- es said cathode plate inside said cathode frame to form a cathodic compartment inside the diaphragm bag.
• Electrowinning is a process where a metal dissolved in an electrolyte is reduced on a cathode by means of electric current. Electrowinning takes place in an electrolytic cell that contains a number of anodes and a number of cathodes arranged in an alternating manner .
• a diaphragm technique can be used in electrowinning metals, which in the electrochemical series are less noble than hydrogen, eg. Ni, Co, Mn .
• the overpotential of the reduction of these metals is higher than that of hydrogen, which is why the development of hydrogen at a low pH should be avoided by separating the anolyte and the catholyte from each other by a material that perme- ates the electrolyte in a controlled manner, such as a diaphragm fabric, and the electrolyte should flow from the catholyte compartment to the anolyte compartment.
• said metal can be recovered using divided-cell electrowinning technology, i.e. where the anode and cathode compartments in the cell are sepa ⁇ rated appropriately.
• the solution surrounding the cathode (catholyte) is separated from the adjacent anodes in the cell by slotting each cath ⁇ ode into a suitable frame, over which a bag of dia ⁇ phragm material is stretched. The diaphragm material of the bag permeates the electrolyte in a controlled manner .
• a typical target in nickel electrowinning is to have a high delta-Ni (also known as bite i.e. difference in Ni concentrations between the electrolyte fed to the electrolysis cell and electrolyte overflown from the cell), or a high anolyte sulfuric acid concentration.
• delta-Ni also known as bite i.e. difference in Ni concentrations between the electrolyte fed to the electrolysis cell and electrolyte overflown from the cell
• delta-Ni also known as bite i.e. difference in Ni concentrations between the electrolyte fed to the electrolysis cell and electrolyte overflown from the cell
• delta-Ni can be increased by two ways, by
• an object of the present invention is to alleviate the problems described above and to intro ⁇ quiz a method of operating an electrolysis cell and a cathode frame that allow the electrowinning to be op ⁇ erated at a high current density and at the same time to achieve a high quality cathode deposit with a smooth surface and with a minimum amount of nodular growth .
• the object of the invention is to introduce a method of operating an electrolysis cell and a cathode frame that allow to achieve a high delta-Me (differ ⁇ ence in the metal concentrations between the electro ⁇ lyte fed to the cell and electrolyte overflown from the cell) whereby less cells are needed to obtain the same capacity.
• the object of the invention is to introduce a method of operating an electrolysis cell and a cathode frame that minimize the number of torn cathode bags and short-cuts and therefore to achieve a high current efficiency . Further, the object of the invention is to introduce a method of operating an electrolysis cell and a cathode frame that allow a good mixing of the electrolyte re ⁇ sulting in a homogenous electrolyte inside the cathode bag .
• a first aspect of the present invention is a method of operating an electrolysis cell in electrowinning of metal, wherein cathode plates are arranged in cathode frames and the cathode plate and cathode frame are en ⁇ closed in a diaphragm bag so as to form a cathode bag assembly, and the cathode bag assemblies and anode plates are arranged in the electrolyte in an electrol- ysis cell in an alternating and consecutive manner.
• the method includes dispos ⁇ ing a gas-sparging means in each of the cathode bag assemblies, and supplying sparging gas to the gas- sparging means such that the gas-sparging means forms a curtain of fine sparging gas bubbles to flush the cathode plate.
• a second aspect of the present invention is a cathode frame configured to retain a cathode plate and a dia- phragm bag which encloses said cathode plate inside said cathode frame to form a cathodic compartment in ⁇ side the diaphragm bag.
• the cathode frame comprises a gas-sparging means for flushing the cathode plate with a curtain of fine sparging gas bubbles inside the cathodic compartment.
• the advantage of the invention is that the sparged gas bubbles arising along the cathode plate surfaces de ⁇ crease the Nernst diffusion layer and thereby increase the limiting current enabling a high current density.
• a high delta-Me or anolyte acid concentration can be achieved and less electrolytic cells leading to a lower capital expendi ⁇ ture for the tankhouse.
• the high current den ⁇ sity it is possible to achieve a very smooth cathode deposit surface, i.e. high quality cathode is achieved. Nodular growth and torn bags are significantly reduced thereby reducing the number of short ⁇ cuts and leading to a high current density and low op ⁇ erating expenses.
• the bubbles also improve mixing of electrolyte inside the diaphragm bag.
• the method further includes disposing an electrolyte feed means in each of the cathode bag assemblies, and supplying electro ⁇ lyte to the electrolyte feed means to feed electrolyte into the cathode bag.
• the gas-sparging allows that electrowinning can be operated at a high current density and therefore the electrolyte feed does not need to be excessively reduced in order to achieve a high delta-Me .
• the gas-sparging means comprises a gas delivery manifold with a plural ⁇ ity of outlet orifices, said gas delivery manifold be ⁇ ing located at a distance below the cathode plate.
• the cathode frame comprises an electrolyte feed means integrated to the cathode frame for feeding of the electrolyte into the cathodic compartment.
• the electrolyte feed means comprises an electrolyte feed manifold lo ⁇ cated adjacent the gas delivery manifold. In an embodiment of the invention, the electrolyte feed manifold is located below the gas delivery mani ⁇ fold. In an embodiment of the invention, the cathode frame comprises
• first guide arranged at the first side member between the upper end and the lower end of the first side member to provide vertical guidance and lateral support for a first edge of the cathode plate
• a second guide arranged at the second side member between the upper end and the lower end of the first side member to provide vertical guidance and lateral support for a second edge of the cathode plate
• hangers at the upper ends of the first and second side member, said hangers being adapted to hang the cathode frame to the support of the opposite walls of the electrolysis cell, and
• a horizontal bottom member extending between and rigidly connecting the lower ends of the first and second side members, whereby the gas deliv- ery manifold is arranged to extend between the side members on and along the bottom member.
• the cathode frame comprises a stop member arranged at each of the first and second side members, against which stop members the lower end of the cathode plate may abut, said stop members being arranged to keep the lower end of the cathode plate at a distance from the gas delivery man ⁇ ifold
• the cathode frame comprises gas inlet channel arranged to supply pres ⁇ surized gas to the gas delivery manifold.
• the gas outlet ori ⁇ fices are disposed at the upper part of the gas deliv ⁇ ery manifold to direct the delivery of bubbles to an upwards direction. The aim is that all gas bubbles go directly upwards so that collisions and fusion of gas bubbles to larger bubbles on the gas delivery manifold are prevented so as to maintain the small size of the gas bubbles.
• the first guide and the second guide are disposed to center the cathode plate in the middle of the gas delivery manifold so that substantially an equal amount of fine bubbles uniformly flush each one of the opposite surfaces of the cathode plate.
• the cathode frame comprises a pair of cross-bars arranged adjacent the upper end of the cathode frame, each one of said cross-bars having a first end connected to the first side member and the a second end connected to the sec ⁇ ond side member.
• the cross-bars com ⁇ prise fastening members by which the diaphragm bag can be releasably fastened to the cathode frame.
• the gas delivery manifold is a gas permeable tube, the lower part of the tube being deposited with a gas impermeable mate- rial.
• the gas permeable upper part of the gas permeable tube is covered with material which improves the breakdown of the bubbles discharged from the orifices to smaller bubbles.
• the cathode frame comprises a cap which is releasably and gas-tightly connectable to the cathode frame, and that the cap comprises a central slot through which the cathode plate is sealably insertable to and removable from the frame .
• the cap comprises a suction pipe for removal of the sparged gas from in- side the bag.
• the method and the cathode frame having the gas- sparging means according to the invention can be used in any electrowinning process that needs separation of the catholyte (electrolyte inside the cathode bag) and the anolyte (electrolyte in the cell space surrounding the cathode bags) .
• the method and the cathode frame of the invention are usable in the elec ⁇ trowinning of nickel, manganese and cobalt.
• the method and the cathode frame are also usable in the electrowinning of copper. Further, it is also usable in the electrowinning of gold and silver.
• a method for electrowinning or a cathode frame which is an aspect of the invention may comprise at least one of the em ⁇ bodiments of the invention described above.
• Fig. 1 schematically shows an exploded view of a cath- ode bag assembly including a cathode frame according to one embodiment of the invention, a cathode plate insertable to the frame and a diaphragm bag configured to be drawn on the frame;
• Fig. 2 shows one embodiment of the cathode bag assem ⁇ bly assembled from the parts shown in Fig. 1 ;
• Figs. 3 shows another embodiment of the cathode frame having both the gas-sparging and electrolyte feed means integrated into the cathode frame;
• Fig. 4 schematically shows a cross-sectional view of the cathode bag assembly immersed in the electrolyte and the gas-sparging means sparging fine bubbles along the cathode plate surfaces;
• Fig. 5 shows a cross-section of the gas delivery manifold of one embodiment of the invention
• Fig. 6 schematically shows an electrolysis cell equipped with the cathode bag assemblies having cath ⁇ ode frames of Fig. 2 and anode plates arranged in the cell .
• FIG 1 shows a cathode frame 2 which is configured to hold a cathode plate 1 and a diaphragm bag 3.
• cathode plate 1 and the diaphragm bag 3 are shown separate from the cathode frame 2.
• the cathode frame 2 with the cathode plate 1 installed in the cathode frame 2 can be inserted inside the diaphragm bag 3 so that the diaphragm bag 3 encloses the cathode frame in a manner as shown in Fig. 2.
• the cathode plate 1 can be either a starter sheet or a permanent cathode.
• the cathode frame 2 comprises a gas-sparging means 6.
• the gas-sparging means comprises a gas delivery manifold 6 having a plurality of outlet orifices 8 through which the sparging gas can be distributed to the elec ⁇ trolyte in the cathodic compartment inside the dia ⁇ phragm bag 3 as a cloud of fine bubbles which rise as a curtain along the surface of the cathode plate 1 as illustrated in Fig. 4.
• Pressurized gas may be supplied to the gas delivery manifold 6 via a gas inlet channel 16.
• the gas outlet orifices 8 are disposed at the up ⁇ per part of the gas delivery manifold 6 to allow bub ⁇ ble delivery only in an upwards direction.
• the gas outlet orifices 8 have a diameter smaller than 3 mm.
• the gas de ⁇ livery manifold 6 may be made of a gas permeable tube, so that only the lower part of the tube is deposited with a gas impermeable material 19 and the upper part of the tube is left undeposited for discharging the sparging gas in an upwards direction.
• the gas imperme ⁇ able material 19 can be any suitable gas impermeable material, such as a layer of paint, lacquer, glue or polymer.
• the gas permeable upper part of the gas per ⁇ meable tube 6 may also be covered with material 24, such as industrial fabric, which improves the break- down of the bubbles discharged from the orifices 8 to even smaller bubbles.
• the cathode frame 2 comprises a vertical first side member 9 having an upper end and a lower end.
• a first guide 10 is arranged at the first side member 9 between the upper end and the lower end of the first side member to provide vertical guidance and lateral support for a first edge of the cathode plate.
• the cathode frame 2 comprises a vertical second side member 11 at a distance from the first side mem ⁇ ber, said second side member having an upper end and a lower end.
• a second guide 12 is arranged at the second side member 11 between the upper end and the lower end of the first side member to provide vertical guidance and lateral support for a second edge of the cathode plate.
• a horizontal bottom member 14 extends between and rigidly connecting the lower ends of the first and second side members 9, 11 so that the cathode frame 2 is substantially a U-shaped rigid structure.
• the cath- ode frame 2 can be made of suitable polymer material reinforced with steel inside the polymer material.
• the gas delivery manifold 6 extends between the side members 9, 11 on and along the bottom member 14.
• the cathode frame 2 comprises a stop member 15 which is arranged oppositely at the first and second side mem ⁇ bers 9, 11 so that the lower end of the cathode plate 1 may abut against the stop members 15.
• the stop mem ⁇ bers 15 being are arranged to keep the lower end of the cathode plate at a distance h from the gas deliv ⁇ ery manifold 6 so that the cathode plate 2 never con ⁇ tacts the gas delivery manifold 6 when the cathode plate 1 is installed in the cathode frame 2 (see Figs. 2 and 4) .
• the first guide 10 and the second guide 12 are disposed to center the cathode plate 1 in the middle of the gas delivery manifold 6 so that substantially an equal amount of fine bubbles uniformly flush each one of the opposite surfaces of the cathode plate 1.
• the cathode frame 2 comprises a pair of hangers 13 at the upper ends of the first and second side member 9. 11.
• the hangers are adapted to hang the cathode frame 2 to the support of the opposite walls of the electrolysis cell 5.
• the cathode frame 2 may al ⁇ so comprise a pair of cross-bars 17 arranged adjacent the upper end of the cathode frame 2.
• the number of cross-bars can also more than two, if needed.
• the cross-bars 17 have a first end connected to the first side member 9 and a second end connected to the second side member 11.
• the cross-bars 17 strengthen the structure of the cathode frame 2.
• the cross-bars 17 may also serve in fastening the dia ⁇ phragm bag to the frame 2. Then the cross-bars 17 may comprise fastening members 18 by which the diaphragm bag 3 can be releasably fastened to the cathode frame 2.
• the fastening members 18 may comprise a plurality of lugs to which the diaphragm bag 3 can be hanged, as shown in Fig. 2.
• the fastening members 18 can be e.g. cable ties or like straps (not shown) by which the diaphragm bag 3 can be hanged to the cross-bars 17.
• FIG. 3 shows a further modification of the cathode frame 2 of Fig. 1.
• the cathode frame 2 comprises a gas-sparging means 6 as disclosed above with reference to Fig. 1, 2, 3 and 5, and also an electrolyte feed means 7 integrated to the cathode frame 2 for feeding of the electrolyte into the ca- thodic compartment inside the bag 3.
• the electrolyte feed means comprises an electrolyte feed manifold 7 located adjacent and below the gas delivery manifold 6.
• the gas delivery man ⁇ ifold 6 of Fig. 1 can also be used to deliver electro ⁇ lyte into the bag 3.
• a simultaneous feeding of both sparging gas and electrolyte via the gas delivery man- ifold 6 is also possible.
• the gas de ⁇ livery manifold 6 (and the electrolyte feed manifold 7 and the bottom member 14 of the frame 2 are all inte- grated into an integral structure.
• the side members 9, 11 may also include shading elements that shade the flow so that the metal precipitating on the cathode surface does not grow on edge regions of the cathode plate 1 and get stuck with the guides 12.
• Fig. 4 shows that the cathode frame 2 may also com ⁇ prise a cap 20 which is releasably and gas-tightly connectable to top of the cathode frame 2.
• the cap 20 comprises a central slot 21 through which the cath- ode plate 1 is sealably insertable to and removable from the frame.
• the sparged gas which is collected to a space limited by the cap 20 and the electrolyte sur ⁇ face may be suctioned by a suction pipe 22 for removal of the sparged gas from inside the bag 3.
• cathode plates 1 are ar ⁇ ranged in cathode frames 2 and the cathode plate and cathode frame are enclosed in a diaphragm bag 3 so as to form a cathode bag assembly as shown on Fig. 2.
• cathode bag assemblies and anode plates 4 are arranged in the electrolyte in an electrolysis cell 5 in an alternating and consecutive manner.
• the neces ⁇ sary busbars arranged to supply electric current are not shown in Fig. 6.
• the busbars may be arranged in any way known to a man skilled in the art.
• Sparging gas is supplied to the gas-sparging means 6 such that a curtain of fine sparging gas bubbles is formed to flush the cathode plate 1.
• electrolyte may be supplied to the electrolyte feed means 7 to feed elec- trolyte into the cathode bag assembly.
• a tube 23 for supplying and distributing sparging gas, resp. electrolyte, to the gas-sparging means 6, resp. to elec ⁇ trolyte feed means 7, is preferable disposed outside the cell 5 beside the side wall of the cell as sche- matically illustrated in Fig. 6.
• the frame was equipped with an air inlet pipe to supply air to the gas delivery hose and cathode guides/holders to keep the cathode in position under sparging and stoppers that kept the bottom edge of the cathode from a distance of the hose.
• the cell was ac ⁇ commodated in a water bath to keep the electrolyte temperature constant.
• Catholyte was pumped into the cell (volume 3.5 1) inside a diaphragm bag that iso- lated catholyte from the anolyte.
• Anolyte was collect ⁇ ed as overflow.
• a nickel starter sheet was used as a cathode and two anodes were Pb-Ag (Ag 0.5%) (size 7.8 cm x 9.0 cm) with the spacing between anodes of 110 mm and hydrostatic head of 20 mm.
• Hydrostatic head is the height difference between anolyte surface and catho ⁇ lyte surface (see also Fig. 4; Catholyte surface is at a higher level than the anolyte surface and therefore the flow of the electrolyte is in the direction from the cathodic compartment (inside cathode bag) to the anodic compartment (outside cathode bag) ) .
• the current density can be increased by using the air sparging at least to 300 A/m 2 and very smooth deposit surface can be produced.
• no short-cuts were detected and it seems that gas sparging also re ⁇ Jerusalem the tendency to obtain short circuits reducing the number of torn bags in the Ni-EW process.
• a further modification of the invention may also be to integrate the gas-sparging means to an anode frame.
• the anode bag assembly comprises and anode frame into which an anode can be placed and a diaphragm bag is installed to enclose these.
• a gas-sparging means may be integrated to the anode frame in a manner that the gas sparging means is located outside the anode bag so that the gas-sparging means may be positioned right below the neighboring adjacent cathode plate to sparge gas as fine bubbles to flush the cathode plate.

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• Chemical & Material Sciences (AREA)
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• Chemical Kinetics & Catalysis (AREA)
• Electrochemistry (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Electrolytic Production Of Metals (AREA)
• Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)

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• 2012
  • 2012-02-08 FI FI20125139A patent/FI123851B/en not_active IP Right Cessation
• 2013
  • 2013-02-06 EA EA201491193A patent/EA028294B1/ru not_active IP Right Cessation
  • 2013-02-06 BR BR112014019547A patent/BR112014019547A8/pt not_active Application Discontinuation
  • 2013-02-06 WO PCT/FI2013/050128 patent/WO2013117814A1/en active Application Filing
  • 2013-02-06 CN CN201380008350.6A patent/CN104160067B/zh not_active Expired - Fee Related
  • 2013-02-06 CA CA2860814A patent/CA2860814C/en not_active Expired - Fee Related
• 2014
  • 2014-08-20 ZA ZA2014/06117A patent/ZA201406117B/en unknown

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