CA1069462A - Method of operating electrolytic diaphragm cells having horizontal electrodes - Google Patents
Method of operating electrolytic diaphragm cells having horizontal electrodesInfo
- Publication number
- CA1069462A CA1069462A CA223,667A CA223667A CA1069462A CA 1069462 A CA1069462 A CA 1069462A CA 223667 A CA223667 A CA 223667A CA 1069462 A CA1069462 A CA 1069462A
- Authority
- CA
- Canada
- Prior art keywords
- cell
- chamber
- liquid
- anolyte
- permeable barrier
- 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.)
- Expired
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
-
- 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
- C25B1/46—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in diaphragm cells
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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 Non-Metals, Compounds, Apparatuses Therefor (AREA)
- Electrolytic Production Of Metals (AREA)
Abstract
Abstract Disclosed is a method of operating an electrolytic cell divided into an anolyte chamber and a catholyte chamber by a substantially hori-zontal, permeable barrier. The anolyte chamber is above the permeable barrier while the catholyte chamber is below the permeable barrier. Elec-trolyte passes from the anolyte chamber through the permeable barrier to the catholyte chamber. An electrical current passes through the cell, thereby evolving chlorine gas on the anode and hydrogen gas on the cathode.
The electrical current is in excess of the unaided flow of electrolyte through the permeable barrier resulting in diminished cathode current efficiency and necessitating augmentation of the flow of electrolyte to restore the current efficiency to acceptable values. According to the disclosed method, chloride gas is collected at super-atmospheric pressure in the anolyte chamber, and withdrawn from the anolyte chamber while main-taining the chlorine gas at such elevated pressure. The elevated pressure of chloride augments the flow of electrolyte through the permeable barrier to the catholyte chamber.
The electrical current is in excess of the unaided flow of electrolyte through the permeable barrier resulting in diminished cathode current efficiency and necessitating augmentation of the flow of electrolyte to restore the current efficiency to acceptable values. According to the disclosed method, chloride gas is collected at super-atmospheric pressure in the anolyte chamber, and withdrawn from the anolyte chamber while main-taining the chlorine gas at such elevated pressure. The elevated pressure of chloride augments the flow of electrolyte through the permeable barrier to the catholyte chamber.
Description
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Backg~ound ~ultiple elec~rolyte processes, i~.~ " diaphragm cell a~d perm~onic : ~ ~ membrane cell processes; for th~ electrolysis:~of alkali metal chloride brine : ~ ~ to yield chlorine9 hydrogen, and elther caust~c~soda:or potassium hydroxide .~ ...
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r~quire a head of brine to force electrolyte throu~h the dlaphr~m or the permionic membrane. This is especially true of electrolytic processes ùsing either modified diaphragms, e.g., diaphragms treated wi~h various agents to increase their life, or permionic membranes.
Stacked bipolar electrolyzers, i.e., bipolar elec~rolyzers having a plurality of bipolar electrolytic cells, each divided into an anolyte chamber and a catholyte chamber by a horizontal diaphragm or permionic membrane, with the anolyte chamber of a cell above the diaphragm or permlonic membrane of the cell and the catholyte chamber of the cell below the diaphragm or permionic membrane, where a plurality of such cells ~ ~
are stacked one atop the other, provide a high amount of electrode area per unit of floor space. However, in such stacked, bipolar, horiæontal cells, economies of construction and operation are realized with a low lndividual cell height. For this reason, the provision of a tall indi-vidual czll to provide a brine head may counter-balance the economies resulting from the stacked, bipolar, horizontal cell configuration.
Additionally, the horizontal cell configuration finds use in mercury cell conversions. Such conversions, necessitated by environmental considerations, result in an electrolytlc cell having the original mercury cell horizontal anode above a horizontal cathode, with a horizontal dia- -phragm or permionic membrane interposed therebetween. The existing cell structure and bus bars of the mercury cell circuit militates against pro-viding electrolyte head means within the electrolytic cell.
One way of augmenting the flow of electrolyte through the per-meable barrier is to draw a vacuum on the catholyte side. However, the provision of a vacuum on the catholyte side may also draw chlorine gas through the permeable barrier, thereby resulting in chlorine gas being present in the catholyte chamber with the hydrogen gas. This is objection-able for safety reasons.
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Summary It has now been found that the beneficial effects of a high hydro-static head may be provided in a horizontal cell by providing a chlorine gas pad, at an elevated pressure, within the anolyte chamber. According to this invention, such an elevated pressure chlorine gas pad is provided within the anolyte chanlber while removing chlorine from the chamber.
In one aspeet the invention provides a method of operating an eleetrolytie eell whieh eell has an eleetrolyte ehamber divided horizontally by a permeable barrier into an anolyte chamber eontaining a substantially horl~ontal anode above said permeable barri~rs, and a eatholyte ehamber containing a substantially horizontal cathode below said horizontal barrier; which method eomprises feeding alkali metal chloride brine to said anolyte ehamber; passing eleetrieal eurren-t through said eell to generate hydrogen gas on said cathode, collecting the chlorine gas in said anolyte ehamber above the anolyte so as to maintain a ehlorine gas pad at an elevated pressure in said anolyte chamber; withdrawing the ehlorine gas from said anolyte ehamber to a liquid-eontaining tank, diseharging the ehlorine gas from said cell into the liquid in said liquid-eontaining tank and maintaining a level of liquid in said liquid-eontaining tank above the level of anolyte liquor in said eell suffieient to augment the flow of anolyte liquor through said permeable barrier against the pressure of the hydrogen to said eathnlyte ehamber.
Detailed Description of the Invention The invention may be understood by reEerence to the figures.
Figure 1 is a perspective, partial cutaway view o one apparatus for obtaining a high chlorine partial pressure within the anolyte chalnber of an electrolytic cell.
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g2 Fi~ure 2 is a schemat:l.c dia~ram of tl~e apyarat:U~ oE l~igure 1 with an associated horizontal cell.
Figure 3 is a partial cutaway view of a hori~ontal bipolar d~aphragm cell in combination with the apparatus of Figure 1.
Figure 4 is a partial cutaway view of a converted mercury cell in combination with the apparatus of Figure 1.
In an electrolytic cell (1) with a horizontal, permeable barrier (11), the el.ectrolyte chamber is divided by the permeable barrier (11) into an anolyte chamber (21~ above the permeable barrier (11) and a catholyte chamber (31) below the permeable barrier (11). Within such a cell (1), the electrodes are substantially parallel to each other and to the permeable barrier (11) with the anode (23) being in the anolyte chamber (21), above the permeable barrier (11), and the cathode (33) being in the catholyte chamber (31), below the permeable barrier (11). Such cells (1) are re-ferred ~o hereln as hortzoDtal cells.
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1~ 2 Modern hori~ontal cells are also characterized by a low vertical clearance between the anode (23) and the top (25) of the anolyte cha~ber (21). For this reason, the space above the anode (23) for the anolyte liquor to provide a hydrostatic head is limited. The amount of vertical space may be less than two feet, frequently less than eighteen inches, and even less than one foot. Such a height is insufficient to provide a head of brine sufficient to drive the electrolyte through the permeable barrier.
In the operation of a horizontal electrolytic cell ~1), a brine feed containing ~rom about 275 to about 325 or more grams yer liter of sodium chloride ls Eed to the anolyte chamber. This brine feed may be saturated or even super-saturated. An electrical current is passed through the cell (1) from the anode (23) through the electrolyte to and through the permeable barrier (11) to the cathode (33). Chlorine gas is generated on the anodes (23) and anolyte liquor passes through the permeable barrier (11) to the catholyte chamber (31). Within the catholyte chamber (31~ -hydrogen gas is generated on the cathode (33) and a catholyte liquor of sodium hydroxide and sodium chloride is obtained.
Catholyte liquor containing from about 120 to about 150 grams per liter of sodium hydroxide and from about 175 ~o about 225 grams per ~-liter of sodium chloride in a diaphragm cell and from about 80 to about 440 grams per liter of sodium hydroxide and about 0.10 to about lO grams per liter of sodium chloride in a permionic membrane equipped cell, is re-covered from the catholyte chamber. Additionally, some of the anolyte liquor may be removed from the anolyte chamber, refortified or resaturated with brine, and recirculated to the anolyte chamber.
While the operation of the electrolytic cell system is illustrated with reference to sodium chloride brines, it is also useful in the electro-lysls of other alkali me~al halide brin~s~ such as potassium chloride brines.
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~694~2 The permeable ba~rier (11) may be in the form of an electrolyte permeable, cation permeable barrier. Such a barrier is called a diaphragm.
Most commonly, asbestos is used to provide the diaphragm. The diaphragm may be deposited onto the upper surface of the cathode from a slu~ry of asbestos in water, in aqueous sodium chloride, or in cell liquor. Most commonly, diaphragms are deposited from a cell llquor slurry containing about one to two weight percent chrysotile asbestos, 120 to 150 grams per liter of sodium hydroxide, and 175 to about 225 grams per liter of sodium chloride. Alternatively~ the asbestos may be provided by asbestos paper or asbestos cloth. The asbestos diaphragm may be trea~ed to increase the . -effective life thereof. For example9 the asbestos diaphragm may be treated with an organic resin having fluorocarbon and fluorocarbon acid moieties, such as DuPont NAFION resin or an inorganic material such as a silicate or the asbestos diaphragm may be sub~ected to thermal treatment.
The permeabla barrier may also be a cation permeable barrier of limited electrolyte pe~meability, such as an ion exchange resin. For example, the per~eable barrier may be provided by a fluorocarbon-fluoro-carbon acid resin ion exchange membrane~ i.e., such as DuPont NAFION or the like.
According to the preferred method of this invention, the operation of the electrolytic cell is facilitated by providing a chlorine gas pad (41) a~ the top (25) of the anolyte chamber (21). The chlorine gas pad (413 is at an elevated pressure so as to provide a hydrostatic head withln the anolyte chamber (21). Typically the chlorine gas pad is at a pressure of from about 0.5 to about 5.0 pounds per square gauge. The hydrostatic head augments the flow of electrolyte through the permeable barrier (11). Ac-cording to this invention, the chlorine gas pad (41) is maintained at an ' - ' 5 _ .
~69462 elevated pressure while withdrawing chlorine from the anolyte chamber ~21).
This may be accomplished by providing a high pressure manifold or by dis-charging the chlorine into a head of liquid.
Most commonly, the chlorine gas pad (41) will be maintained within the anolyte chamber by discharging chlorine into a head of liquid. For example, as shown in Figures 2, 3, and 4, the chlorine gas may be withdrawn from the anolyte chamber (21) of a cell (1) to a liquid-containing tank (51) and discharged into the liquid (53) in the liquid-containin~ tank (51). A
level (55) of liquid (53) sufficient to provide a hydraulic head within the anolyte compartment (21) is maintained within the liquid-containing tank (Sl). This head should be sufficient to drive the electrolyte from the anolyte chamber (21) to and through the permeable barrier (11) into the catholyte chamber (31), thereby augmenting the flow of electrolyte through the bar~ier (11). In this way, the hydrostatic head is sufficient to force electrolyte through tlle barrier (11) against the pressure of the evolved hydrogen, thereby maintaining a high cathode curre~t efficiency.
The upper level (55) of liquid (53) in the liquid-containing tank (51) is sufficiently above the level of the gas discharge (59) into the tank (51) to discharge the chlorine gas into a positive head of liquid, thereby to provide a hydrostatic head within the anolyte chamber (21). For example, the upper level (55) of the liquid (53~ liquid-containing tank (51) may be from about one foot to about four or more or even five or six feet above the level of the gas discharge (59) into the liquid tank (51). The - level (55) Oe the liquid (53) may be regulated, e.g., by movable pipe (60) whereby to regu~ate the pressure of the chlorine gas pad. In this way, a higher head can be provided, for example w~en the diaphragm has "tightened"
or the current density is high. The chlorine gas is recovered from chlo-I rine recovery means~(54) in the upper portion of tank (51), and the over--~ ~ flow liquid, e.g., brlne, ls recovered from movable pipe (60~.
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In Figure 3 is sllo~n one exemplification of an electrolytic cell (7) utilizing the method and apparatus of ~his invention. In Figure 3, a horizontal cell (3) oE a stacked, bipolar diaphragm cell electrolyzer is shown. While only two cells (3) are shown in the figure, there may be five or more, for example9 eleven or fifteen or twen~y cells in the electroly~er. These cells (3) are in bipolar configuration with the cathode (33) of one cell electrically in series with the anode (~3) of the cell directly below. This is accompllshed by a common repeating structural member9 i.e., a bipolar unit (61). ~ bipolar unit (61) includes the cath-ode (33) of one cell (3), an impermeable housing with a metal horizontal floor or surface (63), and the anode (23) o~ the next adjacent cell.
The upper surface (65) of the horizontal floor (63) is abricated of a catholyte-resistant material and provides the floor or bottom oE ~he catholyte chamber of the upper or prior c~ll in the electrolyzer. The cath-odic portion is fabricated of a catholyte-resistant material, such as iron, cobalt, nickel, steel, stainless steel, or the like. The cathodic half cell portion of the bipolar unit (61) includes means (71) for removing cell liquor from the ca~holyte chamber (31) of an individual cell (3). The means (71) for removing cell liquor are generally near the bottom of the cathodic half cell. The cathodic hal~ cell also includes means for removing hydrogen (73) generally near the top of the cathodi'c half cell. Alternatively, the same line may be used for recovering the cell liquor and the hydrogen.
. The cathodic half cell includes a cathode (33). The cathode (33) may be in the form of mesh, rods, perforated plate, or expanded mesh.
The cathode is generally fabricated of iron, cobalt, nickel, steel, stain-less steel, or the lilce. ~dditionally, the cathode (33) may lnclude means thereon for lowerlng the hydrogen overvolcage of the cathode;
The cathode~(33) is connected to the bipolar unit (61) by electrical conducting means (68j. The electrical conducting means (68) , ' `
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~L~D6~ 2 may bc in the form of studs, copper conductorsl conductive spring clips, or the like. The conducting means (68) permit the cathode (33) to be maintained at a pre-determined spacing from the anode ~23) of the cell (3) and to be maintained in an electroconductive relationship with the anode (23) of the next adjacent cell in the electrolyzer.
A permeable barrier (11) is provided above the cathode. The permeable barrier may be in the form of a diaphragm or permionic membrane as deseribed hereinbefore. Typically, the cathode half cell has a height measured from the eatholyte-resistant floor to the top of the cathode of from about one inch to about five inches.
The lower half of the bipolar unit (61) ineludes the anodie half cell of the next adjacent individual eell in the eleetrolyzer. The anodie half eell is fabrieated of an anolyte-resistant material on the eeiling (67? and walls of the anodic half cell. The anolyte-resistant material may be the structural material on the half cell. Alternatively, the anolyte-resistant material may be a coating, film, lamination, or - layer upon the stractural material used to fabricate the cathodic half eell.
` Typically, the anolyte-resistant material is a valve metal.
The valve metals are those metals which form a corrosion-resistant, elec-trieally insulating oxide upon exposure to aeidic aqueous ~edia.
The valve metals inelude titanium, zirconium, hafnium, columbium, tantalum, and tungsten. Most commonly, titanium or tantalum is the valve metal utilized for the anolyte-resistant, anolyte-retaining structure of chlor-alkali electrolytic cells. Titanium is preferred for this service because of its cost and ready availability. However, the anolyte-resistant material may also be a~rubber or plastic coating or sheathing upon the cath-.~
olyte-resistant mate~rial used in fabricating the upper half of the cell.
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i~69~62 The anodic half cell includes brine feed me~ns (77). The brine feed means (77) may be in the form of sparger (78) for spraying the brine feed out of apertures (79) therein at either a horizontal angle or upwardly inclined from the horlzontal. ~lternatively, the brine feed may be in the form of a simple pipe leading into the anolyte chamber.
The anodic half cell includes the anode (23). The anode (23) may be in the form of a valve metal having a suitable electroconductive coating thereon, where the valve metals are as describecl hereinabove.
Most commonly, the anode will be fabricated of titanium or tantalum, with titanium being preferred for chlor-alkali service. The electroconductive -coating on the anode is provided by a corrosion-resistant material having a low chlorine overvoltage, e.g., below about 0.250 voIt at 200 Amperes per square foot. The electroconductive coating is most frequently pro-vided by a metal of the platinum group, i.e., ruthenium, rhodium, palladium, osmium, iridium, platinum, and alloys thereof; oxides of the platinum group metal as ruthenium ox3de, rhodium oxide, palladium oxide, osmlum oxide, iridium oxide, platinum oxide, and oxides thereof; oxygen-containing com-pounds of the platinum group metals such as alkaline earth ruthenates, alkaline earth rhodates, alkaline earth ruthenites, alkaline earth rhodites, cobalt palladite, cobalt platinate, ruthenium titanate, ruthenium titanite, and the like. Alternatively, the electroconductive coating may be pro-vided by mixed crystals of the oxldes of the platinum group metal and the oxides of the valve metals, i.e., the electroconductive surface may be provided by a mixture of ruthenium oxide and titanium dioxide or ruthenium dioxlde and zirconium dioxide or rhodium oxide and titanium dioxide or rhodium oxide and zirconium dioxide or the like. ~dditionally, other oxlde materials may be present in the electroconductive surface, such as, for example, tin oxide, lead oxide, bismuth, antimony, arsenic, or the like.
_ g _ ' ', ' ~0~;9462 Generally, the anodic half cell has a height of from about three inches to about twenty-four inches or more and most frequently from about four inches to about seven inches when measured from the bot-tom of the anode (23) to the ceiling (65) of the anolyte chamber (21).
An individual electrolyeic cell (3) of the bipolar electrolyzer is formed by the anodic half cell of one bipolar unit and the cathodic half cell of the next adjacent bipolar unit with the anode above the per-meable barrier, the cathode below the permeable barrier, and the anode~
cathode permeable barrier being parallel to each other and in horizontal relationship. ~ -In the operation of such a cell, a head of brine is maintained within the anolyte chamber (21) by a chlorine gas pad (41) in the upper portion of the anolyte chamber (21). A chlorine line (43) leads from the anolyte chamber (23) to liquid-containing tank (51). The level of the outlet to pipe (43) from the anolyte chamber (21) is referred to as the overflow level of the cell.
Within the liquid-containing tank (51) the chlorine i9 discharged in such a way as to cause the chlorine to be discharged as many small bubbles rather than as a few large bubbles. For example, the chlorine may be discharged downward into the liquid through a downward facing plpe through a screen or mesh. Alternatively, the chlorine gas discharged into an upward facing pipe (58) with a bubble cap (59) or the like there-above. As shown in the figures, the bubble cap (59) may be provided having serrated edges m order to break up the flow of chlorine into small bubbles~
In this way, a uniform pressure of from about 0.5 to about 5.0 pounds per square inch gauge is provided within the anolyte chamber (21j.
The method of this invention may also be used in mercury cells (5) that have been converted to diaphragm cell operation. Such a mercury .
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cell conversion (5) is shown in Figure 4. Mercury cells (5) typically have an inclined metal bottom (35) for conveying the mercury.
Cathode bus bars (81) feed the current to the inclined surface (35). The inclined surface (35) is most commonly fabricated of iron, cobalt, nickel, steel, stainless steel, or any other material'tha-t is no~ readily attacked by nascent hydrogen, caustic soda, or mercury. Generally, the bottom (35) has a slope of from about one-half percent to about two percent in the direction of the mercury flow. In a mercury cell converted to diaphragm cell service, sufficient s:Lope should be maintained to allow the cell liquor to be collected at one end of the cell, but the slope should not be so great as to permit the opposite end of the cell to run dry. For example, a slope of from about one-quarter of one percent to about one-half of one percent may be maintained.
The anodes (23) are typically suspended from the cell top (83) and spaced from the cell bottom (35) a distance sufficient to provide a spacing of from about 0.085 inch to about 0.125 inch above the mercury, l.e., a spacing of from about 0.15 inch to about 0.30 inch above the cell bottom. A typical mercury cell (5) also includes brine feed means and mercury feed means at the higher end of the cell, brine recovery and mercury recovery at the lower end of the cell, and chlorine recovery along the length of the cell.
When, however, it is necessary to convert a mercury cell to diaphragm cell operation, an electrolyte permeable cathode (33) spaced from the cell bottom (35) is ~rovided. The electrolyte permeable cathode (33) is generally spaced from about two inches to about five inches from the cell bottom (35) and is spaced therefrom by channel frames (37). The channel frames (37) may have perforations therein to allow cell liquor to Elow along the lengtb of the cell botto~ (35) ~o the cell liquor recovery : L~69462 means (71). The channel frames (37) may be joined to the cell bottom (35), for example, by welding or bolLing. Alternatively, the channel frames (37) may simply be laid upon the cell bottom t35). The cathode (33) may be joined to the channel frames (37) by welding or bolting of the like. Al-ternatively, the cathode (33) may just be laid on top of the channel frames (37).
The channel frames (37~ may conduct current from the cathodes (33) to the cathode bus bars (81). Alternatively, electrical conductors (85) may conduct the electrical current from the cathodes (33) to the cathode bus bars (81). The electrical contact may be provided by clips (86) on the cell bottom (35) engaging the cathode (33) or by clips on the ca~hode engaging conductors on the cell bottom (35).
Permeable barrier means (11) are provided on the cathode (33).
The permeable barrier means (ll) define the upper limit of the catholyte chamber (31) and the lower limlt of the anolyte chamber (21).
In a mercury cell conversion (5), the anodes (23) are raised above the normal mercury cell anode position to allow for the cathode (33) and permeable barrier (11) to be inserted in the cell (5). In ~his way, the cathodes (33) originally intended for use with the cell (5) may be salvaged and used for diaphragm cell or permionic membrane cell operation, therefore effecting an econon~y of capital investment. Generally, the anodes (23) are spaced from about l/16 inch to about 3/4 inch above the cathode (33), and generally less than 3/8 inch above the cathode (33) when the per-meable barrier is a deposited asbestos diaphragm. However, when the barrier is an asbestos paper diaphragm, as a 50 mil asbestos paper diaphragm, the anode may be spaced as close as from about 0.05 inch to about 0.125 inch above the cathode.
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' In a mercury cell conversion, the c211 top conventionally used for mercury cell operation may be replaced by a metal or heavy plastic cell top (83) to allow for the containment of the pressurized chlorine gas pad (41).
In the operation of the cell shown in Figure 4, brine feed is through the brine feed means (77). An electrical current passes from the anode (23) through the permeable barrier (11) to the cathode (33) thereby causing chlorine to be ~enerated on the anodes (~3~ and hydrogen to be generated on the cathode (33). Chlorine gas evolved at the anode (3~) is removed through conduit (43) under elevated pressure 9 e.g., from about 0.50 pounds per square inch to about 5.0 pounds per square inch gauge to a liquid-containing tank (51).
Discharge of the chlorine into the liquid-containing tank (51) is from a conduit (43) which delivers the chlorine into the liquid (53).
The downward direction of the discharge into the liquid may be brought about either by a bubble cap arrangement (59) or by a downward-facing con-duit within the liquid-containing tank. By either method, the pressure of the chlorine gas pad (41) is maintained at between 0.50 pounds per square inch gauge and 5.0 pounds per square inch gauge, the~eby to augmsnt the flow of anolyte liquor to the permeable barrier.
The liquid within the liquid-containing tank (51) may be brine or water. Most frequently the llquid will be brine, which may be either saturated brine or depleted;brine. Brine is preferred because of the overflow into the tank (51)~from the cell (1, 3, or 5) through conduit (43) and the backflow~into the~cell (1, 3, or 5) from the tank (51) through the conduit (43). Frequently, especially at high current density operations, e.g., above about 400 Amperes per square foot, and especially above about 600 or even 800 or more Amperes per square foot, a considerable : ~ :
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exces~ of brlne is fed to the cell, e.g., a 400 percent or 600 percent, o~
even an 800 percent excess of brine is fed to the cell. The excess brine may be recovered through conduit (43) and movable pipe (60) and recycled to the cell with the feed brine.
It is to be understood that although the invention has been described with speciEic reference to specific details and particular em-bodiments thereof, it is not to be so limited in that changes and alter-ations therein may be made which are in the full intended scope of this invention as defined by the appended claims.
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Backg~ound ~ultiple elec~rolyte processes, i~.~ " diaphragm cell a~d perm~onic : ~ ~ membrane cell processes; for th~ electrolysis:~of alkali metal chloride brine : ~ ~ to yield chlorine9 hydrogen, and elther caust~c~soda:or potassium hydroxide .~ ...
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. ,: ~ , .. ~ . ~ , - .::
~069~;%
r~quire a head of brine to force electrolyte throu~h the dlaphr~m or the permionic membrane. This is especially true of electrolytic processes ùsing either modified diaphragms, e.g., diaphragms treated wi~h various agents to increase their life, or permionic membranes.
Stacked bipolar electrolyzers, i.e., bipolar elec~rolyzers having a plurality of bipolar electrolytic cells, each divided into an anolyte chamber and a catholyte chamber by a horizontal diaphragm or permionic membrane, with the anolyte chamber of a cell above the diaphragm or permlonic membrane of the cell and the catholyte chamber of the cell below the diaphragm or permionic membrane, where a plurality of such cells ~ ~
are stacked one atop the other, provide a high amount of electrode area per unit of floor space. However, in such stacked, bipolar, horiæontal cells, economies of construction and operation are realized with a low lndividual cell height. For this reason, the provision of a tall indi-vidual czll to provide a brine head may counter-balance the economies resulting from the stacked, bipolar, horizontal cell configuration.
Additionally, the horizontal cell configuration finds use in mercury cell conversions. Such conversions, necessitated by environmental considerations, result in an electrolytlc cell having the original mercury cell horizontal anode above a horizontal cathode, with a horizontal dia- -phragm or permionic membrane interposed therebetween. The existing cell structure and bus bars of the mercury cell circuit militates against pro-viding electrolyte head means within the electrolytic cell.
One way of augmenting the flow of electrolyte through the per-meable barrier is to draw a vacuum on the catholyte side. However, the provision of a vacuum on the catholyte side may also draw chlorine gas through the permeable barrier, thereby resulting in chlorine gas being present in the catholyte chamber with the hydrogen gas. This is objection-able for safety reasons.
~ OG946;~
Summary It has now been found that the beneficial effects of a high hydro-static head may be provided in a horizontal cell by providing a chlorine gas pad, at an elevated pressure, within the anolyte chamber. According to this invention, such an elevated pressure chlorine gas pad is provided within the anolyte chanlber while removing chlorine from the chamber.
In one aspeet the invention provides a method of operating an eleetrolytie eell whieh eell has an eleetrolyte ehamber divided horizontally by a permeable barrier into an anolyte chamber eontaining a substantially horl~ontal anode above said permeable barri~rs, and a eatholyte ehamber containing a substantially horizontal cathode below said horizontal barrier; which method eomprises feeding alkali metal chloride brine to said anolyte ehamber; passing eleetrieal eurren-t through said eell to generate hydrogen gas on said cathode, collecting the chlorine gas in said anolyte ehamber above the anolyte so as to maintain a ehlorine gas pad at an elevated pressure in said anolyte chamber; withdrawing the ehlorine gas from said anolyte ehamber to a liquid-eontaining tank, diseharging the ehlorine gas from said cell into the liquid in said liquid-eontaining tank and maintaining a level of liquid in said liquid-eontaining tank above the level of anolyte liquor in said eell suffieient to augment the flow of anolyte liquor through said permeable barrier against the pressure of the hydrogen to said eathnlyte ehamber.
Detailed Description of the Invention The invention may be understood by reEerence to the figures.
Figure 1 is a perspective, partial cutaway view o one apparatus for obtaining a high chlorine partial pressure within the anolyte chalnber of an electrolytic cell.
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g2 Fi~ure 2 is a schemat:l.c dia~ram of tl~e apyarat:U~ oE l~igure 1 with an associated horizontal cell.
Figure 3 is a partial cutaway view of a hori~ontal bipolar d~aphragm cell in combination with the apparatus of Figure 1.
Figure 4 is a partial cutaway view of a converted mercury cell in combination with the apparatus of Figure 1.
In an electrolytic cell (1) with a horizontal, permeable barrier (11), the el.ectrolyte chamber is divided by the permeable barrier (11) into an anolyte chamber (21~ above the permeable barrier (11) and a catholyte chamber (31) below the permeable barrier (11). Within such a cell (1), the electrodes are substantially parallel to each other and to the permeable barrier (11) with the anode (23) being in the anolyte chamber (21), above the permeable barrier (11), and the cathode (33) being in the catholyte chamber (31), below the permeable barrier (11). Such cells (1) are re-ferred ~o hereln as hortzoDtal cells.
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1~ 2 Modern hori~ontal cells are also characterized by a low vertical clearance between the anode (23) and the top (25) of the anolyte cha~ber (21). For this reason, the space above the anode (23) for the anolyte liquor to provide a hydrostatic head is limited. The amount of vertical space may be less than two feet, frequently less than eighteen inches, and even less than one foot. Such a height is insufficient to provide a head of brine sufficient to drive the electrolyte through the permeable barrier.
In the operation of a horizontal electrolytic cell ~1), a brine feed containing ~rom about 275 to about 325 or more grams yer liter of sodium chloride ls Eed to the anolyte chamber. This brine feed may be saturated or even super-saturated. An electrical current is passed through the cell (1) from the anode (23) through the electrolyte to and through the permeable barrier (11) to the cathode (33). Chlorine gas is generated on the anodes (23) and anolyte liquor passes through the permeable barrier (11) to the catholyte chamber (31). Within the catholyte chamber (31~ -hydrogen gas is generated on the cathode (33) and a catholyte liquor of sodium hydroxide and sodium chloride is obtained.
Catholyte liquor containing from about 120 to about 150 grams per liter of sodium hydroxide and from about 175 ~o about 225 grams per ~-liter of sodium chloride in a diaphragm cell and from about 80 to about 440 grams per liter of sodium hydroxide and about 0.10 to about lO grams per liter of sodium chloride in a permionic membrane equipped cell, is re-covered from the catholyte chamber. Additionally, some of the anolyte liquor may be removed from the anolyte chamber, refortified or resaturated with brine, and recirculated to the anolyte chamber.
While the operation of the electrolytic cell system is illustrated with reference to sodium chloride brines, it is also useful in the electro-lysls of other alkali me~al halide brin~s~ such as potassium chloride brines.
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~694~2 The permeable ba~rier (11) may be in the form of an electrolyte permeable, cation permeable barrier. Such a barrier is called a diaphragm.
Most commonly, asbestos is used to provide the diaphragm. The diaphragm may be deposited onto the upper surface of the cathode from a slu~ry of asbestos in water, in aqueous sodium chloride, or in cell liquor. Most commonly, diaphragms are deposited from a cell llquor slurry containing about one to two weight percent chrysotile asbestos, 120 to 150 grams per liter of sodium hydroxide, and 175 to about 225 grams per liter of sodium chloride. Alternatively~ the asbestos may be provided by asbestos paper or asbestos cloth. The asbestos diaphragm may be trea~ed to increase the . -effective life thereof. For example9 the asbestos diaphragm may be treated with an organic resin having fluorocarbon and fluorocarbon acid moieties, such as DuPont NAFION resin or an inorganic material such as a silicate or the asbestos diaphragm may be sub~ected to thermal treatment.
The permeabla barrier may also be a cation permeable barrier of limited electrolyte pe~meability, such as an ion exchange resin. For example, the per~eable barrier may be provided by a fluorocarbon-fluoro-carbon acid resin ion exchange membrane~ i.e., such as DuPont NAFION or the like.
According to the preferred method of this invention, the operation of the electrolytic cell is facilitated by providing a chlorine gas pad (41) a~ the top (25) of the anolyte chamber (21). The chlorine gas pad (413 is at an elevated pressure so as to provide a hydrostatic head withln the anolyte chamber (21). Typically the chlorine gas pad is at a pressure of from about 0.5 to about 5.0 pounds per square gauge. The hydrostatic head augments the flow of electrolyte through the permeable barrier (11). Ac-cording to this invention, the chlorine gas pad (41) is maintained at an ' - ' 5 _ .
~69462 elevated pressure while withdrawing chlorine from the anolyte chamber ~21).
This may be accomplished by providing a high pressure manifold or by dis-charging the chlorine into a head of liquid.
Most commonly, the chlorine gas pad (41) will be maintained within the anolyte chamber by discharging chlorine into a head of liquid. For example, as shown in Figures 2, 3, and 4, the chlorine gas may be withdrawn from the anolyte chamber (21) of a cell (1) to a liquid-containing tank (51) and discharged into the liquid (53) in the liquid-containin~ tank (51). A
level (55) of liquid (53) sufficient to provide a hydraulic head within the anolyte compartment (21) is maintained within the liquid-containing tank (Sl). This head should be sufficient to drive the electrolyte from the anolyte chamber (21) to and through the permeable barrier (11) into the catholyte chamber (31), thereby augmenting the flow of electrolyte through the bar~ier (11). In this way, the hydrostatic head is sufficient to force electrolyte through tlle barrier (11) against the pressure of the evolved hydrogen, thereby maintaining a high cathode curre~t efficiency.
The upper level (55) of liquid (53) in the liquid-containing tank (51) is sufficiently above the level of the gas discharge (59) into the tank (51) to discharge the chlorine gas into a positive head of liquid, thereby to provide a hydrostatic head within the anolyte chamber (21). For example, the upper level (55) of the liquid (53~ liquid-containing tank (51) may be from about one foot to about four or more or even five or six feet above the level of the gas discharge (59) into the liquid tank (51). The - level (55) Oe the liquid (53) may be regulated, e.g., by movable pipe (60) whereby to regu~ate the pressure of the chlorine gas pad. In this way, a higher head can be provided, for example w~en the diaphragm has "tightened"
or the current density is high. The chlorine gas is recovered from chlo-I rine recovery means~(54) in the upper portion of tank (51), and the over--~ ~ flow liquid, e.g., brlne, ls recovered from movable pipe (60~.
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In Figure 3 is sllo~n one exemplification of an electrolytic cell (7) utilizing the method and apparatus of ~his invention. In Figure 3, a horizontal cell (3) oE a stacked, bipolar diaphragm cell electrolyzer is shown. While only two cells (3) are shown in the figure, there may be five or more, for example9 eleven or fifteen or twen~y cells in the electroly~er. These cells (3) are in bipolar configuration with the cathode (33) of one cell electrically in series with the anode (~3) of the cell directly below. This is accompllshed by a common repeating structural member9 i.e., a bipolar unit (61). ~ bipolar unit (61) includes the cath-ode (33) of one cell (3), an impermeable housing with a metal horizontal floor or surface (63), and the anode (23) o~ the next adjacent cell.
The upper surface (65) of the horizontal floor (63) is abricated of a catholyte-resistant material and provides the floor or bottom oE ~he catholyte chamber of the upper or prior c~ll in the electrolyzer. The cath-odic portion is fabricated of a catholyte-resistant material, such as iron, cobalt, nickel, steel, stainless steel, or the like. The cathodic half cell portion of the bipolar unit (61) includes means (71) for removing cell liquor from the ca~holyte chamber (31) of an individual cell (3). The means (71) for removing cell liquor are generally near the bottom of the cathodic half cell. The cathodic hal~ cell also includes means for removing hydrogen (73) generally near the top of the cathodi'c half cell. Alternatively, the same line may be used for recovering the cell liquor and the hydrogen.
. The cathodic half cell includes a cathode (33). The cathode (33) may be in the form of mesh, rods, perforated plate, or expanded mesh.
The cathode is generally fabricated of iron, cobalt, nickel, steel, stain-less steel, or the lilce. ~dditionally, the cathode (33) may lnclude means thereon for lowerlng the hydrogen overvolcage of the cathode;
The cathode~(33) is connected to the bipolar unit (61) by electrical conducting means (68j. The electrical conducting means (68) , ' `
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~L~D6~ 2 may bc in the form of studs, copper conductorsl conductive spring clips, or the like. The conducting means (68) permit the cathode (33) to be maintained at a pre-determined spacing from the anode ~23) of the cell (3) and to be maintained in an electroconductive relationship with the anode (23) of the next adjacent cell in the electrolyzer.
A permeable barrier (11) is provided above the cathode. The permeable barrier may be in the form of a diaphragm or permionic membrane as deseribed hereinbefore. Typically, the cathode half cell has a height measured from the eatholyte-resistant floor to the top of the cathode of from about one inch to about five inches.
The lower half of the bipolar unit (61) ineludes the anodie half cell of the next adjacent individual eell in the eleetrolyzer. The anodie half eell is fabrieated of an anolyte-resistant material on the eeiling (67? and walls of the anodic half cell. The anolyte-resistant material may be the structural material on the half cell. Alternatively, the anolyte-resistant material may be a coating, film, lamination, or - layer upon the stractural material used to fabricate the cathodic half eell.
` Typically, the anolyte-resistant material is a valve metal.
The valve metals are those metals which form a corrosion-resistant, elec-trieally insulating oxide upon exposure to aeidic aqueous ~edia.
The valve metals inelude titanium, zirconium, hafnium, columbium, tantalum, and tungsten. Most commonly, titanium or tantalum is the valve metal utilized for the anolyte-resistant, anolyte-retaining structure of chlor-alkali electrolytic cells. Titanium is preferred for this service because of its cost and ready availability. However, the anolyte-resistant material may also be a~rubber or plastic coating or sheathing upon the cath-.~
olyte-resistant mate~rial used in fabricating the upper half of the cell.
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i~69~62 The anodic half cell includes brine feed me~ns (77). The brine feed means (77) may be in the form of sparger (78) for spraying the brine feed out of apertures (79) therein at either a horizontal angle or upwardly inclined from the horlzontal. ~lternatively, the brine feed may be in the form of a simple pipe leading into the anolyte chamber.
The anodic half cell includes the anode (23). The anode (23) may be in the form of a valve metal having a suitable electroconductive coating thereon, where the valve metals are as describecl hereinabove.
Most commonly, the anode will be fabricated of titanium or tantalum, with titanium being preferred for chlor-alkali service. The electroconductive -coating on the anode is provided by a corrosion-resistant material having a low chlorine overvoltage, e.g., below about 0.250 voIt at 200 Amperes per square foot. The electroconductive coating is most frequently pro-vided by a metal of the platinum group, i.e., ruthenium, rhodium, palladium, osmium, iridium, platinum, and alloys thereof; oxides of the platinum group metal as ruthenium ox3de, rhodium oxide, palladium oxide, osmlum oxide, iridium oxide, platinum oxide, and oxides thereof; oxygen-containing com-pounds of the platinum group metals such as alkaline earth ruthenates, alkaline earth rhodates, alkaline earth ruthenites, alkaline earth rhodites, cobalt palladite, cobalt platinate, ruthenium titanate, ruthenium titanite, and the like. Alternatively, the electroconductive coating may be pro-vided by mixed crystals of the oxldes of the platinum group metal and the oxides of the valve metals, i.e., the electroconductive surface may be provided by a mixture of ruthenium oxide and titanium dioxide or ruthenium dioxlde and zirconium dioxide or rhodium oxide and titanium dioxide or rhodium oxide and zirconium dioxide or the like. ~dditionally, other oxlde materials may be present in the electroconductive surface, such as, for example, tin oxide, lead oxide, bismuth, antimony, arsenic, or the like.
_ g _ ' ', ' ~0~;9462 Generally, the anodic half cell has a height of from about three inches to about twenty-four inches or more and most frequently from about four inches to about seven inches when measured from the bot-tom of the anode (23) to the ceiling (65) of the anolyte chamber (21).
An individual electrolyeic cell (3) of the bipolar electrolyzer is formed by the anodic half cell of one bipolar unit and the cathodic half cell of the next adjacent bipolar unit with the anode above the per-meable barrier, the cathode below the permeable barrier, and the anode~
cathode permeable barrier being parallel to each other and in horizontal relationship. ~ -In the operation of such a cell, a head of brine is maintained within the anolyte chamber (21) by a chlorine gas pad (41) in the upper portion of the anolyte chamber (21). A chlorine line (43) leads from the anolyte chamber (23) to liquid-containing tank (51). The level of the outlet to pipe (43) from the anolyte chamber (21) is referred to as the overflow level of the cell.
Within the liquid-containing tank (51) the chlorine i9 discharged in such a way as to cause the chlorine to be discharged as many small bubbles rather than as a few large bubbles. For example, the chlorine may be discharged downward into the liquid through a downward facing plpe through a screen or mesh. Alternatively, the chlorine gas discharged into an upward facing pipe (58) with a bubble cap (59) or the like there-above. As shown in the figures, the bubble cap (59) may be provided having serrated edges m order to break up the flow of chlorine into small bubbles~
In this way, a uniform pressure of from about 0.5 to about 5.0 pounds per square inch gauge is provided within the anolyte chamber (21j.
The method of this invention may also be used in mercury cells (5) that have been converted to diaphragm cell operation. Such a mercury .
694~
cell conversion (5) is shown in Figure 4. Mercury cells (5) typically have an inclined metal bottom (35) for conveying the mercury.
Cathode bus bars (81) feed the current to the inclined surface (35). The inclined surface (35) is most commonly fabricated of iron, cobalt, nickel, steel, stainless steel, or any other material'tha-t is no~ readily attacked by nascent hydrogen, caustic soda, or mercury. Generally, the bottom (35) has a slope of from about one-half percent to about two percent in the direction of the mercury flow. In a mercury cell converted to diaphragm cell service, sufficient s:Lope should be maintained to allow the cell liquor to be collected at one end of the cell, but the slope should not be so great as to permit the opposite end of the cell to run dry. For example, a slope of from about one-quarter of one percent to about one-half of one percent may be maintained.
The anodes (23) are typically suspended from the cell top (83) and spaced from the cell bottom (35) a distance sufficient to provide a spacing of from about 0.085 inch to about 0.125 inch above the mercury, l.e., a spacing of from about 0.15 inch to about 0.30 inch above the cell bottom. A typical mercury cell (5) also includes brine feed means and mercury feed means at the higher end of the cell, brine recovery and mercury recovery at the lower end of the cell, and chlorine recovery along the length of the cell.
When, however, it is necessary to convert a mercury cell to diaphragm cell operation, an electrolyte permeable cathode (33) spaced from the cell bottom (35) is ~rovided. The electrolyte permeable cathode (33) is generally spaced from about two inches to about five inches from the cell bottom (35) and is spaced therefrom by channel frames (37). The channel frames (37) may have perforations therein to allow cell liquor to Elow along the lengtb of the cell botto~ (35) ~o the cell liquor recovery : L~69462 means (71). The channel frames (37) may be joined to the cell bottom (35), for example, by welding or bolLing. Alternatively, the channel frames (37) may simply be laid upon the cell bottom t35). The cathode (33) may be joined to the channel frames (37) by welding or bolting of the like. Al-ternatively, the cathode (33) may just be laid on top of the channel frames (37).
The channel frames (37~ may conduct current from the cathodes (33) to the cathode bus bars (81). Alternatively, electrical conductors (85) may conduct the electrical current from the cathodes (33) to the cathode bus bars (81). The electrical contact may be provided by clips (86) on the cell bottom (35) engaging the cathode (33) or by clips on the ca~hode engaging conductors on the cell bottom (35).
Permeable barrier means (11) are provided on the cathode (33).
The permeable barrier means (ll) define the upper limit of the catholyte chamber (31) and the lower limlt of the anolyte chamber (21).
In a mercury cell conversion (5), the anodes (23) are raised above the normal mercury cell anode position to allow for the cathode (33) and permeable barrier (11) to be inserted in the cell (5). In ~his way, the cathodes (33) originally intended for use with the cell (5) may be salvaged and used for diaphragm cell or permionic membrane cell operation, therefore effecting an econon~y of capital investment. Generally, the anodes (23) are spaced from about l/16 inch to about 3/4 inch above the cathode (33), and generally less than 3/8 inch above the cathode (33) when the per-meable barrier is a deposited asbestos diaphragm. However, when the barrier is an asbestos paper diaphragm, as a 50 mil asbestos paper diaphragm, the anode may be spaced as close as from about 0.05 inch to about 0.125 inch above the cathode.
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' In a mercury cell conversion, the c211 top conventionally used for mercury cell operation may be replaced by a metal or heavy plastic cell top (83) to allow for the containment of the pressurized chlorine gas pad (41).
In the operation of the cell shown in Figure 4, brine feed is through the brine feed means (77). An electrical current passes from the anode (23) through the permeable barrier (11) to the cathode (33) thereby causing chlorine to be ~enerated on the anodes (~3~ and hydrogen to be generated on the cathode (33). Chlorine gas evolved at the anode (3~) is removed through conduit (43) under elevated pressure 9 e.g., from about 0.50 pounds per square inch to about 5.0 pounds per square inch gauge to a liquid-containing tank (51).
Discharge of the chlorine into the liquid-containing tank (51) is from a conduit (43) which delivers the chlorine into the liquid (53).
The downward direction of the discharge into the liquid may be brought about either by a bubble cap arrangement (59) or by a downward-facing con-duit within the liquid-containing tank. By either method, the pressure of the chlorine gas pad (41) is maintained at between 0.50 pounds per square inch gauge and 5.0 pounds per square inch gauge, the~eby to augmsnt the flow of anolyte liquor to the permeable barrier.
The liquid within the liquid-containing tank (51) may be brine or water. Most frequently the llquid will be brine, which may be either saturated brine or depleted;brine. Brine is preferred because of the overflow into the tank (51)~from the cell (1, 3, or 5) through conduit (43) and the backflow~into the~cell (1, 3, or 5) from the tank (51) through the conduit (43). Frequently, especially at high current density operations, e.g., above about 400 Amperes per square foot, and especially above about 600 or even 800 or more Amperes per square foot, a considerable : ~ :
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exces~ of brlne is fed to the cell, e.g., a 400 percent or 600 percent, o~
even an 800 percent excess of brine is fed to the cell. The excess brine may be recovered through conduit (43) and movable pipe (60) and recycled to the cell with the feed brine.
It is to be understood that although the invention has been described with speciEic reference to specific details and particular em-bodiments thereof, it is not to be so limited in that changes and alter-ations therein may be made which are in the full intended scope of this invention as defined by the appended claims.
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Claims (15)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of operating an electrolytic cell which cell has an electrolyte chamber divided horizontally by a permeable barrier into an anolyte chamber containing a substantially horizontal anode above said permeable barriers, and a catholyte chamber containing a substantially horizontal cathode below said horizontal barrier; which method comprises feeding alkali metal chloride brine to said anolyte chamber; passing electrical current through said cell to generate hydrogen gas on said cathode,collecting the chlorine gas in said anolyte chamber above the anolyte so as to maintain a chlorine gas pad at an elevated pressure in said anolyte chamber; withdrawing the chlorine gas from said anolyte chamber to a liquid-containing tank; discharging the chlorine gas from said cell into the liquid in said liquid-containing tank and maintaining a level of liquid in said liquid-containing tank above the level of anolyte liquor in said cell sufficient to augment the flow of anolyte liquor through said permeable barrier against the pressure of the hydrogen to said catholyte chamber.
2. The method of Claim 1 wherein the bottom of said catholyte chamber is inclined from the horizontal.
3. The method of Claim 1 wherein the chlorine gas is discharged into said liquid-containing tank upwardly into a bubble cap.
4. The method of Claim 1 where an excess of brine is fed to the cell, and the excess brine is recovered with the evolved chlorine gas, and recirculated to the cell.
5. A method of operating an electrolytic cell which cell has an electrolyte chamber divided into an anolyte chamber and a catholyte chamber by a substantially horizontal, permeable barrier, said anolyte chamber being above said permeable barrier and containing an anode sub-stantially parallel to said permeable barrier, said catholyte chamber being below said permeable barrier and containing a cathode substantially parallel to said permeable barrier, whereby electrolyte ill said anolyte chamber passes through the permeable barrier to the catholyte chamber;
which method comprises feeding an alkali metal chloride brine to said cell; passing electrical current through said cell at a current density in excess of the hydraulically unaided flow of electrolyte through the barrier; evolving chlorine gas on the anode; collecting the chlorine gas as a gas pad at super-atmospheric pressure in said anolyte chamber; and withdrawing said chlorine while maintaining the gas pad at an elevated pressure whereby to augment the flow of electrolyte through the permeable barrier to the catholyte chamber.
which method comprises feeding an alkali metal chloride brine to said cell; passing electrical current through said cell at a current density in excess of the hydraulically unaided flow of electrolyte through the barrier; evolving chlorine gas on the anode; collecting the chlorine gas as a gas pad at super-atmospheric pressure in said anolyte chamber; and withdrawing said chlorine while maintaining the gas pad at an elevated pressure whereby to augment the flow of electrolyte through the permeable barrier to the catholyte chamber.
6. The method of Claim 5 comprising withdrawing the chlorine from the anolyte chamber to a liquid-containing tank, and discharging the chlorine gas into said liquid.
7. The method of Claim 6 where an excess of brine is fed to the cell, and the excess brine is recovered from the cell and recirculated to the cell.
8. The method of Claim 7 comprising maintaining a level of liquid in the liquid-containing tank to provide a pressure of chlorine in said anolyte chamber sufficient to aid the flow of electrolyte through the permeable barrier.
9. The method of Claim 6 wherein the chlorine is upwardly discharged into a bubble cap in said liquid-containing tank.
10. The method of Claim 6 comprising varying the level of liquid in said liquid-containing tank whereby to vary the pressure of chlorine in said liquid-containing tank.
11. The method of Claim 5 wherein the pressure of chlorine in said anolyte chamber is greater than 0.5 pounds per square inch gauge.
12. An electrolytic cell which cell has an electrolyte chamber divided horizontally by a permeable barrier into an anolyte chamber con-taining a substantially horizontal anode above said permeable barrier, and a catholyte chamber containing a substantially horizontal cathode below said horizontal barrier; means for feeding alkali metal chloride brine to said anolyte chamber; means for passing electrical current through said cell whereby to generate chlorine on said anode; means to collect chlorine gas in said anolyte chamber whereby to maintain a chlorine gas pad in said anolyte chamber; means to withdraw chlorine gas from said anolyte chamber to a liquid-containing tank; means to discharge chlorine gas from said cell into the liquid in said liquid-containing tank while maintaining a level of liquid in said liquid-containing tank above the level of anolyte liquor in said cell.
13. The electrolytic cell of Claim 12 wherein the bottom of said catholyte chamber is inclined from the horizontal.
14. The electrolytic cell of Claim 12 wherein the means to discharge chlorine gas from said anolyte chamber into said liquid-con-taining tank comprises a conduit From said anolyte chamber to said liquid-containing tank; an upward extension of said conduit into said tank, and a bubble cap above said upward extension above said conduit.
15. The electrolytic cell of Claim 12 including means to vary the level of liquid in said liquid-containing tank.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US460414A US3893897A (en) | 1974-04-12 | 1974-04-12 | Method of operating electrolytic diaphragm cells having horizontal electrodes |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1069462A true CA1069462A (en) | 1980-01-08 |
Family
ID=23828610
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA223,667A Expired CA1069462A (en) | 1974-04-12 | 1975-04-02 | Method of operating electrolytic diaphragm cells having horizontal electrodes |
Country Status (10)
| Country | Link |
|---|---|
| US (1) | US3893897A (en) |
| JP (1) | JPS5248116B2 (en) |
| BE (1) | BE827842A (en) |
| CA (1) | CA1069462A (en) |
| DE (1) | DE2515372C3 (en) |
| FR (1) | FR2267390B1 (en) |
| GB (1) | GB1463289A (en) |
| NL (1) | NL7504094A (en) |
| SE (1) | SE400315B (en) |
| ZA (1) | ZA751804B (en) |
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|---|---|---|---|---|
| JPS534796A (en) * | 1976-07-05 | 1978-01-17 | Asahi Chem Ind Co Ltd | Electrolysis of pressurized alkali halide |
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| FR2426747A1 (en) * | 1978-05-26 | 1979-12-21 | Solvay | Electrolytic cell contg. non-wettable diaphragm e.g. of PTFE - is esp. for electrolysis of alkali metal chloride aq. soln. |
| US4256551A (en) * | 1978-11-02 | 1981-03-17 | Imperial Chemical Industries Limited | Electrolytic process |
| US4204920A (en) * | 1978-12-06 | 1980-05-27 | Allied Chemical Corporation | Electrolytic production of chlorine and caustic soda |
| US4247376A (en) * | 1979-01-02 | 1981-01-27 | General Electric Company | Current collecting/flow distributing, separator plate for chloride electrolysis cells utilizing ion transporting barrier membranes |
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| WO2018193381A1 (en) * | 2017-04-20 | 2018-10-25 | Michael Siegert | Multi-purpose bio-electrical modules and procedures |
| WO2020112024A1 (en) * | 2018-11-26 | 2020-06-04 | Agency For Science, Technology And Research | An electrochemical reactor system comprising stackable reaction vessels |
| CN112725832A (en) * | 2020-12-18 | 2021-04-30 | 阳光电源股份有限公司 | Water electrolysis hydrogen production control method, system and controller |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US2882210A (en) * | 1955-07-01 | 1959-04-14 | George N Jenks | Electrolytic water purification process |
| US3623970A (en) * | 1968-01-30 | 1971-11-30 | Georg Haas | Compact ozonizer for water lines |
| US3736322A (en) * | 1971-07-19 | 1973-05-29 | Lockheed Aircraft Corp | Chlorinator cell with internal pressure regulation |
-
1974
- 1974-04-12 US US460414A patent/US3893897A/en not_active Expired - Lifetime
-
1975
- 1975-03-21 ZA ZA00751804A patent/ZA751804B/en unknown
- 1975-04-02 CA CA223,667A patent/CA1069462A/en not_active Expired
- 1975-04-07 NL NL7504094A patent/NL7504094A/en not_active Application Discontinuation
- 1975-04-09 DE DE2515372A patent/DE2515372C3/en not_active Expired
- 1975-04-10 SE SE7504149A patent/SE400315B/en unknown
- 1975-04-10 FR FR7511235A patent/FR2267390B1/fr not_active Expired
- 1975-04-11 BE BE155328A patent/BE827842A/en unknown
- 1975-04-11 JP JP50044180A patent/JPS5248116B2/ja not_active Expired
- 1975-04-11 GB GB1490975A patent/GB1463289A/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| AU7960575A (en) | 1976-09-30 |
| JPS5248116B2 (en) | 1977-12-07 |
| GB1463289A (en) | 1977-02-02 |
| DE2515372C3 (en) | 1981-02-12 |
| NL7504094A (en) | 1975-10-14 |
| DE2515372B2 (en) | 1980-06-04 |
| BE827842A (en) | 1975-10-13 |
| JPS50143799A (en) | 1975-11-19 |
| SE400315B (en) | 1978-03-20 |
| FR2267390B1 (en) | 1977-11-10 |
| FR2267390A1 (en) | 1975-11-07 |
| US3893897A (en) | 1975-07-08 |
| ZA751804B (en) | 1976-10-27 |
| DE2515372A1 (en) | 1975-10-16 |
| SE7504149L (en) | 1975-10-13 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |