EP1048093A1 - Cellule electrolytique a faible densite de courant et son procede de fabrication - Google Patents

Cellule electrolytique a faible densite de courant et son procede de fabrication

Info

Publication number
EP1048093A1
EP1048093A1 EP99969981A EP99969981A EP1048093A1 EP 1048093 A1 EP1048093 A1 EP 1048093A1 EP 99969981 A EP99969981 A EP 99969981A EP 99969981 A EP99969981 A EP 99969981A EP 1048093 A1 EP1048093 A1 EP 1048093A1
Authority
EP
European Patent Office
Prior art keywords
cell
cathode
anodes
electrolytic cell
cathode tube
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP99969981A
Other languages
German (de)
English (en)
Inventor
Richard L. Romine
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Eltech Systems Corp
Original Assignee
Eltech Systems Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Eltech Systems Corp filed Critical Eltech Systems Corp
Publication of EP1048093A1 publication Critical patent/EP1048093A1/fr
Withdrawn legal-status Critical Current

Links

Classifications

    • 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
    • C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
    • C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
    • C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms

Definitions

  • the present invention relates to an electrolytic cell of decreased current density which allows for lower power consumption, and a method for reconfiguring an electrolytic cell to allow for lower power consumption while maintaining the designed current capacity of the cell.
  • Electrolytic cells are used extensively on an industrial scale for the production of metals and chemicals, e.g., for the electrowinning of aluminum, copper, nickel and zinc and the production of chlorine, chlorides, sodium hydroxide, sodium chlorate, hydrogen and oxygen.
  • chlor-alkali cells and particularly chlor- alkali diaphragm cells.
  • Chlor-alkali diaphragm cells were originally designed to operate at relatively low current capacities of about 10,000 amperes. These cells had relatively low production capacities by modern standards. Typical cells of this type are the Hooker Type S cells which were developed by the Hooker Chemical Corporation. This particular cell was subsequently improved upon by increasing its designed current capacity to about 50,000 amperes with corresponding increases in production capacity.
  • a method for substantially decreasing the power consumption of an electrolytic cell while maintaining the designed current capacity is achieved by increasing the number of cathodes and anodes within the cell body. This can be accomplished in part by decreasing the lateral dimensions of the individual cathode tubes. This modification helps to allow the use of substantially more cathodes and anodes within the cell. It can be used with a reduction in the existing spacing between anodes and cathodes. Moreover, sufficient space is maintained within cathode tubes to allow for improved release of hydrogen gas from the cathode.
  • the number of anodes within the cell can be increased from 42 up to as many as 50 elements, while the number of cathodes can be increased from 20 up to as many as 24 elements.
  • the new electrolytic cell has the following additional advantage of improved anodic efficiency as a result of lower current density producing smaller chlorine gas bubbles at the anode which are more easily removed from the anode surface.
  • the hydrogen disengagement of the cathode is also improved, resulting in less hydrogen in the chlorine which is a significant product improvement.
  • the lower current density also results in a lower cell liquor temperature which reduces the corrosion of metal parts and extends the life of the plastic cell top and rubber anode blanket.
  • the invention is directed to an electrolytic cell having a walled enclosure of a size containing from about 42 to about 46 anodes and from about 20 to about 22 cathodes, the cathodes comprising spaced apart conductive metal cathode tube members of foraminous conductive metal plates forming the exterior of a cathode tube structure, the improvement in the cell comprising an increased number of up to about 25 cathode tube members of reduced cathode-to-cathode spacing and an increased number of up to about 52 anodes, of reduced anode-to-anode spacing, the cell having a cathode area increase of up to about 20 percent and an anode area increase of up to about 20 percent.
  • the invention is directed in a manner related to the foregoing, but for a cell having three times the number of anodes than cathodes, plus three additional anodes, wherein there is provided an increased number of anodes from about 87 to about 102, and increased number of cathodes from about 28 to about 33.
  • the invention is directed to a method of decreasing the power consumption of an electrolytic cell, the cell having a walled enclosure of a size containing from about 42 to about 46 anodes and from about 20 to about 22 cathodes, with there being a proportion of two times the number of anodes than cathodes, plus two additional anodes, each cathode comprising spaced apart foraminous conductive metal plates forming the exterior of a cathode tube structure, wherein a cell top is removed from the electrolytic cell and the walled enclosure of a size is separated from a cell base, the method comprising the steps of:
  • the above method is directed in a related manner to a cell having about 87 anodes and about 28 cathodes, where there is provided an increase to about 102 anodes as well as to about 33 cathodes.
  • the invention is directed to a method for providing an electrolytic cell of reduced power consumption, said cell having a walled enclosure sized for containing from about 42 to about 46 anodes and from about 20 to about 22 cathodes, with there being a proportion of two times the number of anodes than cathodes, plus two additional anodes, each cathode comprising spaced apart conductive foraminous metal plates forming the exterior of a cathode tube structure, wherein the cell comprises a cell top, the walled enclosure, and a cell base, the method comprising the steps of:
  • the foregoing method can be directed to a cell having about 87 anodes and about 28 cathodes, where there is provided an increase to about 102 anodes and about 33 cathodes.
  • the invention is directed to a cathode tube structure member comprising spaced apart foraminous conductive metal plates having a tube width of about 1 5/64 inches and a tube length of about 50 inches.
  • the invention is directed to a method of operating an electrolytic cell having from greater than 20 up to about 24 cathodes and from greater than 42 up to about 50 anodes, which method comprises:
  • Fig. 1 is a perspective view of the exterior of an electrolytic cell used for employing the present invention.
  • Fig. 1 A is a side elevation, in section of a type of cathode sidewall utilized for the electrolytic cell of Fig. 1 .
  • Fig. 2 is an enlarged partial sectional and elevation view depicting internal components including cathode tube structures, as well as a portion of the walled enclosure of the electrolytic cell of Fig. 1 .
  • Fig. 2A is a magnified view of a portion of the cathode tube structures and anodes of Fig. 2 highlighting the cathode-to-cathode spacing (CS) and the cathode tube width (TW).
  • CS cathode-to-cathode spacing
  • TW cathode tube width
  • Electrolytic cells employing the present invention can typically be useful for the electrolysis of a dissolved species contained in a bath, such as in electrolyzers employed in a chlor-alkali cell to produce chlorine and caustic soda, or in an electrolysis process producing chlorate.
  • the cathode and cathode assembly elements can be made of any electrically conductive metal resistant to attack by the catholyte in the cell.
  • the cathodes can be any of those as are conventionally used in a cell including activated cathodes.
  • FIG. 1 there is shown an electrolytic cell 1 which can be adapted in accordance with the present invention.
  • Principal elements of the cell 1 include the cell top 2, which can be formed from a corrosion-resistant plastic material, the cathode walled enclosure or "cell can" 3, and cell base 5 (Fig. 2).
  • Part of the cathode walled enclosure 3 is positioned behind a sidewall busbar 4 (Fig. 1 A), as will be more particularly described hereinbelow.
  • the cell top 2 is fastened to the cathode walled enclosure 3 which is, in turn, fastened to a cell base 5.
  • the fastening means allow ease of removal of the cell top 2, cathode walled enclosure 3 and cell base 5.
  • This bonded structure extends the full length from an edge of the cell top 2 downwardly to a cell base 5.
  • the sidewall busbar 4 can be a unitary, monolithic and planar busbar 4 that, for the particular cell of the figure, is as high as the cathode walled enclosure 3 and can be longer than the walled enclosure 3 to which it is bonded.
  • the busbar 4 may thus be actually larger than the walled enclosure 3.
  • the extra length of the sidewall busbar 4 and its adjacent walled enclosure 3 together form one wall of the cell 1 .
  • the cathode busbar 4 being typically a copper busbar 4
  • the cathode walled enclosure 3 such as by explosion bonding, brazing or roll bonding.
  • a cathode busbar 4 of this type is described in U.S. Patent 5, 137,61 2, the disclosure of which is incorporated herein by reference.
  • the cathode busbar structure 4 may comprise other configurations, e.g., a plurality of copper busbar strips of varying dimensions. These busbar strips can be attached to the cathode walled enclosure 3 by any suitable manner, as by welding.
  • a cathode busbar structure of this type is described in U.S. Patent 3,904,504, the disclosure of which is incorporated herein by reference.
  • Fig. 2 there is then illustrated, for a representative cell, the cathode walled enclosure 3 and the individual cathode tube structure members 1 1 .
  • These representative cathode tube structure members 1 1 are formed from pairs of adjacent parallel conductive metal screens or perforated plates 12. These two plates 1 2, with their top 1 2A and bottom 1 2B, collectively form a cathode tube.
  • the plates 1 2 of an individual tube 1 1 for the representative cell of the figure to be refurbished are usually spaced apart approximately 1 3/16 inches.
  • the cathode tube structure members 1 1 further include cathode tube reinforcing means 1 5.
  • Disposed at each end of the electrolytic cell 1 and within the walled enclosure 3 are cathode end tube structures 1 7. These end tube structures 1 7 are somewhat identical to the cathode tubes 1 1 , however, the end tube structures have only one conductive metal screen or perforated plate 12 forming the end of the cathode tube structure.
  • Fig. 2A there is then shown an expanded view of the bottom portion of Fig. 2, in which the cathode tube structure member width, usually referred to herein just as the "tube width" (TW) is illustrated.
  • This tube width is the distance measured between the outside surfaces of the two plates 12 of a cathode tube.
  • the cathode-to-cathode spacing (CS), then, is the distance measured between cathodes. This can be the spacing between adjacent cathodes or, as depicted in the figure, the spacing between a cathode end tube structure 1 7 and the next adjacent cathode tube structure member 1 1 . In the representative old cell 1 to be refurbished, the spacing (CS) will generally be 2 1 /4 inches.
  • the cell 1 is filled with an electrolytic medium, preferably a brine solution, and current is supplied to the cell 1 through external connections.
  • the products of the cell 1 are removed through outlets situated on the side of the cell 1 .
  • These products for a chlor-alkali cell include sodium hydroxide, chlorine and hydrogen gas.
  • the initial step is to drain the cell 1 of electrolytic solution and disconnect the external electrical connections to the cell 1 .
  • the cell top 2 is then removed from the cell by disconnecting it from the cathode walled enclosure 3.
  • the cathode walled enclosure 3 is disconnected and removed from the cell base 5.
  • the cathode walled enclosure 3 can be removed from the cell base 5 using any convenient means, such as by a crane or hoist.
  • the cathode tube structure members 1 1 After detachment and removal of the cathode walled enclosure 3 from the cell base 5, the cathode tube structure members 1 1 , usually 20 in number for this representative cell, are removed from the cathode walled enclosure 3. This is accomplished by cutting the cathode rim screen 16
  • FIG. 2 around the internal periphery of the cathode walled enclosure 3 and then cutting any connection points of the cathode tube structure members 1 1 to the cathode walled enclosure 3.
  • the existing cathode tube structure members 1 1 are then removed from the enclosure 3.
  • New cathode tube structure members 1 1 similar in appearance and which can be at least generally similar in their elements of construction to the original cathode tube structure members 1 1 are then installed into the cathode walled enclosure 3.
  • the new cathode tube structure members 1 1 have a narrower lateral dimension or "tube width" (TW) of approximately 1 5/64 inches, again as measured between the outside surfaces of adjacent plates 1 2 in the same structure 1 1 .
  • TW lateral dimension
  • This width permits the accommodation of up to 24 cathode tube structures 1 1 in the refurbished cathode walled enclosure, providing a cathode area increase of up to approximately 20 percent.
  • cathode area increase of from about 1 5 to about 20 percent can be realized for the type of cell as represented by the cell of the figutes.
  • any corrugated conductive metal reinforcing means 1 5 which may be used will also be narrower, i.e., have a narrower width, than the original reinforcing means.
  • the new cathode tube structure members 1 1 can, by way of example, have a tube length of about 50 inches.
  • conductive rods may be placed between the corrugations of the reinforcing means 1 5 and form a part of the cathode tube structure members 1 1 .
  • These rods can be metal rods consisting of copper, brass, or bronze and can serve to conduct electrical current more efficiently along the cathode tubes.
  • the space between the reinforcing means 1 5 and the perforated plates 12 is approximately the same as provided in the original design. This space defines a hydrogen gas channel within the cathode tube structure member 1 1 . While the tube width is decreased for the cell of the figures, this helps allow for an increased number of tubes, thereby providing adequate space for release of the hydrogen gas from the cathode tube structure member
  • the same number of electrical contact points is also more than adequate in the new member since the reconfigured cell has a somewhat lower current density than the original cell.
  • the refurbished cell of the figures may have a current density of as low as approximately 1 .2 amperes per square inch. This compares to a current density of 1 .5 amperes per square inch for the conventional cell. Both of these current densities are based on equivalent design current capacity of 84,000 amperes. Design current capacity for commercial cells will often be within the range from about 50,000 amperes to about 100,000 amperes.
  • the new cathode tube structure members 1 1 are then reinstalled in the cathode walled enclosure 3 in a similar manner as the original cathode tube structure members 1 1 .
  • a new cathode rim screen 1 6 is also installed around these members 1 1 and the sidewall of the cathode walled enclosure 3.
  • CS cathode-to-cathode spacing
  • the type of cell as represented by the cell of the figures has a proportion of anodes to cathodes that is two times the number of anodes than cathodes, plus two additional anodes. With the improved cells of this type there can generally be obtained an anode area increase of from about 1 5 to about 20 percent.
  • the anodes 20 are positioned between adjacent cathode tube structure members 1 1 . All cathodes, including additional cathodes, are attached to the cell base 5 in any suitable manner, such as by bolting or welding. Also, in a cell refurbishing, the anode-to-anode spacing can be reduced from 3 5/8 inches to 3 1 /8 inches. As for the cathodes, this anode spacing is the width within the cell 1 between adjacent anodes 20.
  • the invention cell is an improved MDC-55, such cell can have three times the number of anodes than cathodes, plus three additional anodes.
  • an original cell of 28 cathodes and 87 anodes may have, as an improved cell, 33 cathodes and 102 anodes.
  • the anode area increase, as well as the cathode area increase, can also be on the order of about 20 percent.
  • the anode-to-anode spacing may be reduced by about 0.8 inch.
  • the invention cell could be an improved MDC cell of the type MDC-29 that has twice the number of anodes than cathodes, plus two additional anodes, the cell could contain 25 cathodes, as opposed to 22 for the original cell, and as an improved cell have 52 anodes, as opposed to 46 for the original cell.
  • the cathode walled enclosure 3 can then be reattached to the cell base 5.
  • the cell top 2 is then reinstalled and attached to the cathode walled enclosure 3. Following connection of the electrical contacts, the cell 1 can be placed into service.
  • the outer surfaces of the individual cathode plates 12 are covered by a separator.
  • the separator for the cell will be a diaphragm, e.g., an asbestos diaphragm, which may sometimes be referred to herein as a "diaphragm porous separator".
  • a synthetic, electrolyte permeable diaphragm can also be utilized.
  • the synthetic diaphragms generally rely on a synthetic polymeric material, such as polytetrafluoroethylene fiber as disclosed in U.S. Patent 5,606,805 or expanded polytetrafluoroethylene as disclosed in U.S. Patent 5, 183,545.
  • Such synthetic diaphragms can contain a water insoluble inorganic paniculate, e.g., silicon carbide, or zirconia, as disclosed in U.S. Patent 4,606,805.
  • a water insoluble inorganic paniculate e.g., silicon carbide, or zirconia
  • the diaphragm is the generally non- asbestos fiber diaphragm containing inorganic particulates as disclosed in U.S. Patent 4,853,101 .
  • this diaphragm of particular interest comprises a non- isotropic fibrous mat wherein the fibers of the mat comprise 5-70 weight percent organic halocarbon polymer fiber in adherent combination with about 30-95 weight percent of finely divided inorganic particulates impacted into the fiber during formation.
  • the diaphragm has a weight per unit surface area of between about 3 to about 1 2 kilograms per square meter. Preferably, the diaphragm has a weight in the range of about 3-7 kilograms per square meter.
  • a particularly preferred particulate is zirconia.
  • Other metal oxides, i.e., titania can be used, as well as silicate, aluminates, ceramics, cermets, carbon, and mixtures thereof.
  • the diaphragm may be compressed, e.g., at a compression of from about one to about 6 tons per square inch.
  • the anodes 20 will be coated with an electrochemically active coating.
  • electrochemically active coatings for the foraminous metal anode are those provided from platinum or other platinum group metals or they can be represented by active oxide coatings such as platinum group metals, magnetite, ferrite, cobalt spinel or mixed metal oxide coatings.
  • Such coatings have typically been developed for use as anode coatings in the industrial electrochemical industry. They may be water based or solvent based, e.g., using alcohol solvent. Suitable coatings of this type have been generally described in one or more of the U.S. Patent Nos. 3,265,526, 3,632,498, 3,71 1 ,385 and 4,528,084.
  • the mixed metal oxide coatings can often include at least one oxide of a valve metal with an oxide of a platinum group metal including platinum, palladium, rhodium, iridium, and ruthenium or mixtures of themselves and with other metals.
  • Further coatings include tin oxide, manganese dioxide, lead dioxide, cobalt oxide, ferric oxide, platinate coatings such as M x PT 3 0 4 where M is an alkali metal and x is typically targeted at approximately 0.5, nickel-nickel oxide and a mixture of nickel and lanthanum oxides, such an lanthanum nickelate.
  • the operating temperature of the present invention can be increased by either raising the feed brine temperature or by insulating the electrolytic cell. This is typically done by wrapping the cathode with an insulation blanket.
  • Results of the cell operation presented in the following table illustrate the improved performance of the representative new cell of the figures as compared to the conventional, or comparative cell. Both cells operate at an equivalent design current capacity of 84,000 amperes and also produce the same amount of cell product. However, the new cell has a significantly reduced power consumption as well as a reduced current density and operates at a cell voltage below 3.4.

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

Abstract

L'invention concerne dans un aspect une cellule électrolytique (1) et un procédé pour diminuer la consommation d'énergie d'une cellule électrolytique (1) présentant une capacité de courant nominale fixe. Ce procédé consiste à rééquiper une cellule électrolytique (1) de cathodes et d'anodes additionnelles pour diminuer la densité de courant global de la cellule. Dans le but de loger les anodes additionnelles, l'espacement entre cathodes (CS) peut être réduit et les cathodes peuvent également être reconfigurées pour constituer une structure tubulaire à cathodes (11) plus étroite, ce qui peut être réalisé par réduction de l'espacement entre les plaques cathodiques (12) opposées. Cette modification permet le fonctionnement de la cellule (1) à la capacité de courant nominale initiale avec une consommation d'énergie notablement réduite. Une nouvelle fabrication de cellule est également envisagée.
EP99969981A 1998-11-05 1999-11-04 Cellule electrolytique a faible densite de courant et son procede de fabrication Withdrawn EP1048093A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US10713698P 1998-11-05 1998-11-05
US107136P 1998-11-05
PCT/US1999/026107 WO2000030187A2 (fr) 1998-11-05 1999-11-04 Cellule electrolytique a faible densite de courant et son procede de fabrication

Publications (1)

Publication Number Publication Date
EP1048093A1 true EP1048093A1 (fr) 2000-11-02

Family

ID=22315043

Family Applications (1)

Application Number Title Priority Date Filing Date
EP99969981A Withdrawn EP1048093A1 (fr) 1998-11-05 1999-11-04 Cellule electrolytique a faible densite de courant et son procede de fabrication

Country Status (7)

Country Link
EP (1) EP1048093A1 (fr)
BR (1) BR9906750A (fr)
CA (1) CA2316930A1 (fr)
NO (1) NO20003456L (fr)
PL (1) PL343901A1 (fr)
WO (1) WO2000030187A2 (fr)
ZA (1) ZA200003243B (fr)

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3705862A1 (de) * 1986-02-27 1987-09-03 Oxytech Systems Inc Verfahren zum verringern des energiebedarfes einer elektrolytischen zelle

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO0030187A2 *

Also Published As

Publication number Publication date
PL343901A1 (en) 2001-09-10
NO20003456L (no) 2000-09-04
ZA200003243B (en) 2001-05-31
BR9906750A (pt) 2000-12-05
WO2000030187A2 (fr) 2000-05-25
CA2316930A1 (fr) 2000-05-25
NO20003456D0 (no) 2000-07-04
WO2000030187A3 (fr) 2000-11-16

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