US3607704A - Alkali salt electrolysis by mercury process and apparatus therefor - Google Patents

Alkali salt electrolysis by mercury process and apparatus therefor Download PDF

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Publication number
US3607704A
US3607704A US715046A US3607704DA US3607704A US 3607704 A US3607704 A US 3607704A US 715046 A US715046 A US 715046A US 3607704D A US3607704D A US 3607704DA US 3607704 A US3607704 A US 3607704A
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Prior art keywords
mercury
vessel
tower
electrolysis
passageway
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Expired - Lifetime
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US715046A
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English (en)
Inventor
Hiroshi Shibata
Teruo Imai
Shigeji Kumaki
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Kureha Corp
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Kureha Corp
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    • 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
    • C25B9/70—Assemblies comprising two or more cells
    • 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
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
    • C25B1/36—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in mercury cathode cells
    • 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
    • C25B1/00—Electrolytic production of inorganic compounds or non-metals
    • C25B1/01—Products
    • C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
    • C25B1/36—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in mercury cathode cells
    • C25B1/42—Decomposition of amalgams
    • 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
    • C25B11/00—Electrodes; Manufacture thereof not otherwise provided for
    • C25B11/02—Electrodes; Manufacture thereof not otherwise provided for characterised by shape or form
    • C25B11/033—Liquid electrodes
    • 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
    • C25B9/30—Cells comprising movable electrodes, e.g. rotary electrodes; Assemblies of constructional parts thereof
    • C25B9/303—Cells comprising movable electrodes, e.g. rotary electrodes; Assemblies of constructional parts thereof comprising horizontal-type liquid electrode

Definitions

  • Tung Attorney-Wenderoth, Lind & Ponack ABSTRACT In an alkali salt electrolysis operation by the mercury process in which mercury recovered in a denuding tower is recirculated with wash water through a return passageway to return to an electrolysis vessel, a large portion of this mecury is thus returned to the electrolysis vessel, and the remainder portion of the mercury, together with the wash water and mecury emulsion floating and flowing above it, undergo auxiliary recirculation back to the denuding toward.
  • This invention relates generally to the field of the mercury process (or amalgam process) and more particularly to improvements in salt electrolysis by the mercury process and to new and improved apparatus thereof.
  • the sodium amalgam which is formed within a mercury process, using a slat electrolysis bath, is separated from the electrolyte and contaminants and then denuded in a denuding tower to recover mercury, which is separated from the caustic soda fonned, washed with water, and then recirculated by a pump to the electrolysis bath.
  • a portion of the mercury recovered in the denuding tower is rendered into minute particles by the agitation of the pump and becomes mixed with water or (and) contaminants, such as graphite powder which is produced by disintegration of denuding or decomposing granular graphite within the denuding tower, to form a butterlike emulsion, which floats on the surface of the mercury.
  • this butterlike emulsion and the butterlike emulsion formed in the electrolysis bath by the intermixing of impurities such as magnesium salts and calcium salts within the electrolyte and disintegrated particles from the graphite anode with the mercury amalgam are collectively referred to as mercury butter.”
  • these two emulsions are differentiated, the former being referred to as mercury emulsion, and the latter being referred to as amalgam butter.”
  • a mercury process, salt electrolysis method and apparatus in which, in the path of the mercury recovered in the denuding tower and being sent by a pump to the electrolytic bath vessel, most of this mercury is separated out, to be sent to the electrolysis vessel, by an underflow baffle plate (which may also constitute a part of the sidewall of the path in some cases) having at the lower part thereof a mercury passage for separating only mercury, while the contaminants, such as mercury emulsion, floating in the path on the upstream side of the baffle plate are caused to overflow continuously, together with a small quantity of mercury and wash water, over an overflow weir provided in the path into an auxiliary mercury circulation path and sent to the denuding tower thereby to prevent stagnant accumulation of mercury emulsion of the upstream side of the baffle plate and to thereby prevent mercury passing under and past the baffle plate.
  • FIG. 1 is a diagrammatic plan view, with a part out out for foreshortening, showing one example of an electrolytic apparatus embodying the invention
  • FIG. 2 is a fragmentary, relatively enlarged perspective view, with parts cut away and parts in section showing the details of the part designated by Roman numeral II in FIG. I;
  • FIG. 3 is a diagrammatic plan view, with a part cut away, showing another example of an electrolytic apparatus embodying the invention
  • FIG. 4 is a diagrammatic plan view, with a part cut out for foreshortening, showing still another example of an electrolytic apparatus embodying the invention.
  • FIG. 5 is a fragmentary, relatively enlarged perspective view, with parts cut away and parts in section, showing the part designated by Roman numeral V in FIG. 4.
  • the principal part of the electrolytic apparatus is a salt electrolytic bath vessel 1 having an entrance-pass electrolysis chamber 2 and an exit-pass electrolysis chamber 3.
  • Mercury which has flowed through these electrolysis chambers and has become a sodium amalgam passes through a gas baffle 4 and a mercury bafl'le 5, thereby being separated from electrolyte and amalgam butter, and then passes through an amalgam outlet passageway 6 to enter a denuding tower 7.
  • denuding is accomplished, and, as caustic soda is formed, mercury is recovered.
  • the mercury thus recovered passes through path or conduit 8, is pumped by a pump 9, and enters a mercury return passageway 11, where the mercury is washed by wash water supplied into the passageway 11 through a wash water inlet I0. Then, at a mercury underflow baffle 12, only mercury is separated out and is recirculated to a mercury inlet passageway 13 of the electrolysis vessel I.
  • an auxiliary circulation path 15 connected through an overflow weir 14 to the mercury return passageway II is provided, and over this weir 14, as shown in detail in FIG. 2, mercury emulsion 17 which would otherwise accumulate in a stagnant state on the upstream side of the mercury baffle l2 and wash water 18 together with a small quantity of mercury 16 are caused to overflow and, flowing through the path 15, enter the aforementioned amalgam passageway 6 to recirculate to the denuding tower 7.
  • the labor required for operation is reduced since there is no necessity for scooping off accumulated mercury emulsion. Furthermore, there is no loss of mercury which would inevitably occur in the refining of the mercury emulsion if it were to be removed by scooping.
  • Another feature of this separation method and means is that, since a small quantity of mercury 16, together with mercury emulsion l7 and wash water 18, is constantly overflowing over the weir 14, the surface part of the mercury on the upstream side of the baffle I2 is flowing continuously toward the weir l4, and, therefore, even if there is a tendency of the greater portion of the mercury which passes under and past the baffle 12 to exert a pull on the mercury in the upper part, the induced flow of or on the mercury surface acts as a barrier whereby the mercury emulsion and wash water floating above the mercury are prevented from accompanying the mercury passing through the baffle I2.
  • This mercury separation can be made even more effective by constructing the baffle member so that it forms a part of a sidewall of the passageway II and is, therefore, parallel or nearly parallel to the mercury flow path. An example of such a construction is illustrated in FIG. 3.
  • Mercury emulsion is not separated in the practice of the present invention for the following reason. Since mercury emulsion has a lower viscosity than amalgam butter containing metallic salts such as magnesium salts and calcium salts, there is no possibility of mercury emulsion clogging parts of the denuding tower when it is introduced into the denuding tower. Furthermore, since it is relatively easy to separate mercury out of mercury emulsion, almost all of the emulsion is broken down during its passage through the denuding tower, and mercury is separated out.
  • the mercury emulsion is recirculated in the aforedescribed manner by means of the auxiliary circulation path in accordance with the invention, there is no necessity of being concerned with an increase to some extent in the formation of mercury emulsion within the mercury pump, and it has also become possible to reduce the quantity of mercury accumulating in the pump by using a high-speed pump.
  • a further feature of the invention is that all of the wash water is recirculated to the denuding tower and used as amalgam denuding water, whereby a high recovery rate of caustic soda is obtained.
  • the present invention is not limited in application to the mercury-circuit of such a specific organization. That is, the invention can be applied with equal efi'ectiveness to the mercury circulation paths of many other apparatus organizations as, for example, a horizontal electrolysis vessel of single-pass type which is being widely used or a long narrow electrolysis vessel as illustrated in FIG. 3 in which the flow is transversely directed across the width of the vessel.
  • the auxiliary circulation path may be connected directly to the denuding tower.
  • the mercury which has flowed through an electrolysis chamber 21 in the arrow direction and become an amalgam flows along a passageway 22 and out of the vessel and, at a mercury underflow baffle 23, is separated from the electrolyte and amalgam butter.
  • the mercury amalgam thus separated enters a passageway 24, where it confluently joins wash water, mercury emulsion, and other substances flowing into passageway 24 through an auxiliary circulation path 3I to enter a denuding tower 25.
  • Amalgam butter and other substances accumulating on the upstream side of the mercury bafile 23 are removed by a suitable method.
  • the resulting mercury leaving the denuding tower 25, together with wash water supplied through an inlet 27, is pumped by a pump 26 into a passageway 28 having a sidewall which is partly formed by a mercury underflow baffle 29.
  • a weir 30 is provided at the downstream extremity of the passageway 28, and matter overflowing this weir into the upstream end of the aforementioned auxiliary circulation path 31.
  • the mercury sent from the mercury pump (9 or 26) through the return passageway (11 or 28) is separated out by a mercury bal'fle (I2 or 29) and, after first entering a mercury supply passageway (13 or 32) outside of the electrolysis vessel, is then sent therefrom into the electrolysis vessel.
  • the mercury amalgam thus separated flows through a passageway 55 to a denuding tower $6.
  • the mercury leaving the denuding tower is pumped, together with wash water supplied through an inlet 57, by a pump 58 into a return passageway 59 having a downstream part 60 which constitutes the above mentioned mercury supply passageway.
  • This passageway 60 is parallely adjacent to the inlet side of the electrolysis vessel 5] and has therewith a common sidewall 61 having along its lower part a large number of openings 62 for separating mercury through which the passageway 60 communicates with the interior of the electrolysis vessel SI. Most of the mercury supplied through the passageway 60 passes through these openings 62 into the vessel 51.
  • a weir 63 is provided a cross the downstream end of the passageway 60, and a small portion of the mercury flowing along this passageway overflows, together with mercury emulsion and wash water floating thereabove, over this weir 63 to fall into a chamber 64 and, passing through an auxiliary circulation path 65 connected to this chamber 64, is recirculated directly to the denuding tower 56.
  • an apparatus system for conducting an alkali salt electrolysis by mercury process which apparatus embodies an electrolysis vessel (I) having sidewalls and portions constituting an inlet side and an outlet side; a denuding tower (7) having inlet and outlet sides for receiving and exiting mercury and related fluid flow media, and operable for denuding mercury amalgam evolved in the process as received from said electrolysis vessel (1) in order to recover mercury; conduit means forming circulation passageways a portion of which connects said vessel (1) with said denuding tower, and for otherwise conducting mercury and mercury amalgam and other related fluid including mercury emulsion toward and away from said vessel and tower; said conduit means also including a mercury return passageway (11) operably connected to said vessel: means (10) for introducing wash water into the system; and pump means (9) for positively conveying said mercury together with wash water through said system including passage through said mercury return passageway (ll) leading to said yessel (l); the improvement comprising in combination therewith:
  • a weir (12) disposed in a lower portion of said mercury return passageway (11), so as to separate and help collect a large amount of mercury within the lower portion of said passageway (11), while permitting weir overflow of relatively small amounts of the separated mercury together with wash water and mercury emulsion fluid flowing above said mercury responsive to a flow induced by the pump means (9) to convey the mercury and amalgam fluid;
  • branch conduit means constituting part of said conduit means, and forming an auxiliary mercury emulsion circulation passageway for conducting the combined smaller amounts of mercury, wash water and mercury emulsion back to said denuding tower (7);
  • said means (9) to convey the fluid mercury and mercury amalgam include a high-speed circulating pump having an input side and an output or delivery side, said pump interposed between said tower (7) and vessel (1), at the output side of said tower (l), and operably connected with said mercury return passageway (11) preceding the latter's connection with said vessel (1 said mercury return passageway (11) including a portion downstream of said pump serving also as a mercury supply passageway (60) at the inlet side of said vessel (1);
  • said latter-mentioned mercury supply passageway being elongated and disposed to adjoin and communicate with a sidewall of said electrolysis vessel (1) by means of a common wall portion which constitutes a baffle plate therebetween, said baffle plate provided at its lower part with at least one mercury-separating opening; and
  • said apparatus further including an overflow weir (63) disposed transversely to the elongated direction of flow in a lower portion of said latter mercury supply passageway (60) at the downstream end beyond said mercuryseparating opening, and said auxiliary recirculation passageway (15) of paragraphs (c) and (d) being connected with the downstream end of said mercury supply passageway (60) beyond said weir (63) in an arrangement interconnecting it operatively back with said inlet side of said tower (7).
  • an apparatus system for conducting an alkali salt electrolysis by mercury process which apparatus comprises an electrolysis vessel and a denuding tower, each having an inlet and outlet side, and said tower serving to denude mercury amalgam evolved from said vessel to recover mercury; conduit means connecting said vessel and tower in a fluid flow circuit into which wash fluid media is introduced; and pump means for imparting a positive flow to intermixed mercury and wash media through the circuit, the improvement in the combination of an electrolysis vessel having adjoined integrally therewith an elongated tubular mercury supply passageway adaptable to constitute a portion of said conduit means; said mercury supply passageway and vessel having a common elongated sidewall constituting a baffle plate therebetween at the inlet side of said vessel, and which baffle plate is provided with a series of mercury-separating openings along its lower part; said mercury supply passageway further having at its downstream end an overflow weir disposed transversely thereacross so as to have a predetermined space thereabove for predeterminable overflow of a mercury and washflow

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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)
  • Inorganic Chemistry (AREA)
  • Electrolytic Production Of Metals (AREA)
  • Electrolytic Production Of Non-Metals, Compounds, Apparatuses Therefor (AREA)
US715046A 1967-04-05 1968-03-21 Alkali salt electrolysis by mercury process and apparatus therefor Expired - Lifetime US3607704A (en)

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BE (1) BE713223A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
CH (1) CH493641A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
DE (1) DE1767130B1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
DK (1) DK135429B (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
ES (1) ES352766A1 (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
FR (1) FR1562412A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
GB (1) GB1207714A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
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NO (1) NO120072B (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html)
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4199418A (en) * 1979-05-08 1980-04-22 Basf Wyandotte Corporation Mercury recovery system in electrolytic process

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AT167834B (de) * 1947-05-14 1951-03-10 Vittorio De Nora Verfahren und Vorrichtung zur kontinuierlichen Zersetzung von Alkali-Amalgam

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4199418A (en) * 1979-05-08 1980-04-22 Basf Wyandotte Corporation Mercury recovery system in electrolytic process

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ES352766A1 (es) 1970-01-01
DE1767130B1 (de) 1971-09-30
BE713223A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1968-08-16
DK135429C (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1977-10-10
NL6804863A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1968-10-07
NL136042C (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1972-08-15
SE349553B (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1972-10-02
CH493641A (fr) 1970-07-15
GB1207714A (en) 1970-10-07
NO120072B (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1970-08-24
DK135429B (da) 1977-04-25
FR1562412A (GUID-C5D7CC26-194C-43D0-91A1-9AE8C70A9BFF.html) 1969-04-04

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