US2226784A - Electrolytic cell - Google Patents

Description

Dec. 31, 1940.

E. SORENSEN ELECTROLYTIC CELL Filed Oct. 26, 1938 v 3 Sheets-Sheet 1 N NVENTOR tV/Iar'SOre/Zsen BY 9W. 2

TORNEYS Dec. 31, 1940. E. SORENSEN ELECTROLYTIC 'CELL Filed 'Oct. 26, 195a 3 Sheets-Shet 2 I INVENTOR [mar 507677.562?

E; SORENSEN ELEdTROLYTIC CELL Dec. 31, 1940.

s Sheet s-Shee t 5 Filed Oct. 26, 1938 I INVENTOR 51/707 Jarenaaz 7 BY. $.91, M w

ATTORNEYS Patented Dec. 31, 1940 I Einar Sorensen, Rumi'ord, Maine, assignor to xford Paper Company, a corporation otMaine Application October 26, 1938,-Serial No. 236,999

8 Claims. This inventionrelates toelectrolytic cells of the circulating mercury type for producing chlorine and sodium hydroxide from brine. Such a 5 cell is disclosed in 'my prior patents, Nos.

2,104,677, 2,104,678 and 2,104,679, issued January.

The cell of the present application, in general construction and operation, is similar to the cell disclosed in my prior patents referred to but em- 10 bodies certain improvements hereinafter described and claimed.

The cell disclosed in the above mentioned patents has a decomposing compartment and an oxidizing compartment. Mercury is circulated v in a tortuous path through the decomposing compartment and then over grooved graphite plates located in the oxidizing compartment. The mercury in the decomposing compartment constitutes the cathode of an electric circuit. Graphite plates located above the mercury in the decomposing compartment constitute the,

anodes. Brine is admitted to the decomposing compartment and when an electric current passes between the graphite plates and the mercury,

chlorine is liberated from the brine and part of the mercury forms an amalgam with the sodium of the brine. The mixture of mercury and amalgam flows out of the decomposing compartment into the oxidizing compartment where it passes over the grooved graphite plates. Water is fed into the oxidizing compartment and by the electrolytic actionset up in this compartment the amalgam is decomposed and the sodium reacts with the water to form sodium hydroxide solution. The mercury thus freed of its sodium then enters a pump chamber in which a rotary pump lifts the mercury and returns it to the decomposing compartment. p

The principal object of the present invention is to improve certain details of the oxidizing compartment of the cell shown in my prior patents;

In accordance with the present invention the grooved graphite plates over which the mixture of mercury and amalgam flows in the oxidizing compartment are positioned and supported in a pan preferably, made of black iron although it may be made of, or have a surfacing of, nickel or other material which is sufllciently resistant to the caustic. The pan is removably mounted in the oxidizing compartment and thegraphite plates are removably clamped-in the pan.

It is advantageous to maintain a relatively deep layer of mercury and amalgam flowing through the grooves in the graphite plates in the oxidizing compartments as I have found that by so doing a more thorough decomposing of the amalgam can be obtained. My theory, which explains this result but to which I .do not wish to be limited, is that the amalgam exists I in the mercury as a mechanical 'mix' ture and 5 since it is of lower specific gravity it will rise to the top if given the opportunity. Therefore,

when a deep layer'of mercury and amalgamisy employed the amalgam is given'a chance to rise to the top of the mercury and thus come into .10

contact with the caustic solution and be denuded. Moreover, the greater depthof mercury and amalgam in the grooves provides more contact between the mercury-amalgam mixture and the graphite which is thought to contribute to 16 the. denuding action. In order to regulate the depth of the mercury am-algam mixture flowing over the graphite plates and to insure the presence of av relatively deep layer of it, I provide a mercury seal through which the mercury passes 20 in leaving the metallic' pan, and I provide-the mercury seal with an adjustable over-flow outlet whereby the depth of the mercury flowing through the grooves in the graphite plates can be regulated.

The pan above referred to is so supported in the oxidizing compartment that there is a space under it. During operation of the cell the sodium hydroxide solution surrounds the pan and thereiore some of it occupies the space under the pan. 30 This space affords a convenient and practical location for va heating instrumentality, so I provide a steam pipe, or the like, at this place which may be used to heat the sodium hydroxide solution when this is iound desirable. 35

The improved cell, is shown in the accompanying drawings in which:

Figure .1 is a plan view of the cell with the cover and anodef' assembly of the decomposing compartment removed; 1

Fig. 2 isa longitudinal section through the oxidizing compartment taken on the line 22 of Fig. 3 is a transverse section through the oxidizing compartment taken on the line 3-3 45 compartments taken'on the .line 6-6 of Fig. 1.

The improved cell has an external casing I, 55

preferablymade of steel, which is generally rectangular in shape as shown in Fig. 1. It. is divided into two compartments, by a longitudinal partitionf2. One or these compartments designated 3 is the decomposing compartment, and the other one designated 4 is the oxidizing compartment. As shown at 5 in Figs. 5 and 6 that part of the casing which houses the oxidizing compartment projects downwardly to a lower level than the part of the casing which houses the decomposing compartment.

Brine to be treated enters the decomposing compartment through an inlet 6 (Figs. 1 and 4). The mercury enters the decomposing compartment from the oxidizing compartment at I. Upon reaching the decomposing compartment it first flows through a transverse passage and then longitudinally in a tortuous path sively through channels 9,. l and II, as indicated by the arrows in Fig. 1. The right-hand end of the channel ll communicates with a passage l2 through which the mercury leaves the decomposing compartment and enters the oxidizing compartment. The various passages and channels in the decomposing compartment may be' molded in concrete I3. 2 I

The mercury flowing in a thin layerthrough the decomposing compartment forms the cathode of an electric circuit. It makes electrical contact ,shown in the drawings.

through vertical openings IS in the concrete with metal strips l4 (Figs. 1 and 4) embedded in the concrete. The metal strips [4 are electrically connected to a bus bar I (Fig. 4)

A cover I! for the decomposing compartment (Fig. 4) supports a number of graphite plates l8 which constitute the anode of the electric circuit. The lower faces of the plates 18 lie just above the surface of the mercury flowing'through the channels 8,10 and II. The graphite plates l8 are connected in the electric circuit by conductors not When current passes through the brine betweenthe graphite plates and the mercury, chlorine is liberated from the brine and part of the mercury forms an amalgam withthe sodium' of the brine. The spent brine together with the liberated chlorine is discharged from the decomposing compartment through an outlet Ill. The mixture of mercury and amalgam flows through the passage l2, hereinbefore described, into the oxidizing compartment. The decomposing compartment, in construction and operation, is practically identical with the decomposing compartmentof the cell shown in my prior patents above. referred to and requires no further description. p

The mixture of mercury and amalgam entering the oxidizing compartment through the passage l2 first flows into a well 20 (Figs. 1 and 5) formed in a body of concrete at the right-hand end of the oxidizing compartment. It then passes through a conduit '21 (Figs. 1 and 2)- and up through an elbow 22 and is discharged into the pan 24 hereinbefore referred to. The elbow enters the bottom of the .pan and is fastened to the pan by a lock nut 22'. The lower portion of the well 20, the conduit 2|, andthe elbow 22, form a mercury seal which prevents brine from passing along with the mercury into the oxidizing compartmenta When'the mercury reaches the pan 24 it fiows'over grooved graphite plates, shown at 23, positioned inand supp rted by the pan.

The pan 24 is preferably black iron but it may i v -.be made of, or surfaced with, any material which is resistant to the action of the caustic soda solution formed in the oxidizing compartment. The

under the plates.

pan is supported in the oxidizing compartment at an elevated position to bring the graphite plates to the proper level and to provide a space below the pan for the'purposes hereinafter mentioned. It may be supported on angleirons 25 (Figs. 1 and 2) which span the oxidizing. compartment, and are welded at their ends to the side walls of the casing I. three of these angle irons are shown. The pan may be removably supported by these angle irons by simply resting on them but preferably it is removably clamped to them. Passing transversely over the top of the pan immediately above the angle irons 25 are three angle irons 26 whose extremities are connected t6 the angle irons 25 by.

bolts 21. Under each angle iron 26 there is a clamping element 28, made of any suitable caustic resistant material, which bears on the graphite plates. Tightening of the bolts. draws the angle 1 irons 26 toward the angle irons 25and firmly retains the graphite plates in the metallic pan and firmly retainsthe pan on the angle irons 25.

Additional retaining means for the graphite plates may be providedif so desired by passing transversely under the pan a number of T-irons 29 (Figs. 2 and 3) to the ends of which are welded bolts 21. An angle iron 25' extends transverselyv over the pan above each T-iron and is connected at its extremities to the bolts 21'. A clamping elementZB' is located under each angle iron '26 so that when the angle irons 26" are In the present instance drawn toward the T-irons 28 by tightening' the bolts the graphite plates will be clamped 'in the pan by the clamping elements 28'. I

Inasmuch as the bottom of the graphite plates is uneven, the platesare preferably positioned on a layer of caustic-resistant cement, or similar material, indicated at 23' in Fig. 3'. This material levels the unevenness at the bottom of the plates and equalizes the stress applied by the clamps. It also fills up any pockets under the plates which might lodge mercury or caustic solution that happened to seep through .the plates. This material isalso used to fill in the crevices between and around the edges of the plates to prevent mercury or causticsolution from finding their way The graphite plates may be readily and quickly removed by removing the nuts on the bolts 21 and 21' and then removing the angle irons 26 and 26 and the clamping elements28 and 28. This also permits removal of the pan when the lock nut 22' on the elbow 22 is removed and when the hereinafter described mercury discharge pipe is disconnected. By removing only the nuts on the bolts 21, the pan, with the graphite plates still clamped in it by the bolts 21', may first be removed as a unit if so desired, and the graphite plates later I removed from the pan.

After the mercury flows through the grooves of the graphite plates 23 it is discharged from the pan 24 by apipe 30 (Figs. 1 and 6). This pipe is generally U-shaped and forms a mercury seal which prevents the caustic solution formed in the plates 23 cannbe regulated to maintain in the oxidizing compartment the desired relatively deep layer of mercury. As the mercury leaves the nipple-Sl it flows directly into a pump well 32 molded in a body'ofconcrete at the left-hand'end of the oxidizing compartment. A rotary pump 33 picks up the mercury and discharges it into a transverse trough 34 in the manner described in my prior patents. It is discharged by the trough'into a generally U-shaped pipe 35 by means of which it-is conducted backto the decomposing compartment. The pipe 35 constitutes a mercury seal which allows only mercury to pass into the de composing compartment.

The water that is required in the oxidizing compartment is admitted from a pipe 36 into the pump well 32. It is picked up by the rotary pump and is discharged together with the mercury into the trough 34. The water, of course, floats on top of the mercury in the trough 34 and it is discharged through' a pipe 31 directly into the oxidizing compartment.

In the oxidizing compartment the amalgam is decomposed and the sodium reacts with the water to form sodium hydroxide solution. The sodium hydroxide solution thus formed fills the oxidizing compartment and completely surrounds the pan 24. It flows from the oxidizing compartment through a pipe 40 into the hydrometer 5 compartment 4| of a casing 42 (Fig 1) from which it flows over the upper edge of a partition 43 intoa second compartment 44 and is discharged through a pipe 45 communicating with the bottom of this compartment. The caustic soda solution is maintained at the proper level in the oxidizing compartment by adjusting the level of the upper edge of the partition 43. The space under themetallic pan 24 may accommodate the instrumentality used for heating the caustic solution. In the present instance this is sh'ownas a steam pipe 39 (Figs. 1 and 3). Preferably the caustic solution nowhere comes in contact with any concrete. The bodies of concrete at the ends of the oxidizing compart- 0 ment may be faced with black iron sheets 38 (Fig. 2') to prevent contact of the caustic solution with them. Soine of the advantages resulting from the improvements herein described are as iollows: 45 The cost of the cell is reduced due to the simplicity of installing the black iron pan and the graphite plates. The maintenance cost is reduced as the graphite plates in the black iron pan may be readily removed, repaired or replaced. The pan may be removed without much difiiculty when repairs are necessary. Fewer graphite plates than usual may be used and this makes for economy.

Supporting the pan at an elevated position in the oxidizing compartment provides a space under it in which any foreign impurities that might enter with the water can settle out. This space aiIords a convenient location for the heating pipe where it is immersed in the liquid body of caustic thus insuring uniform distribution of the heat. Moreover, the space under the pan increases the amount of caustic solution in the oxidizing compartment thus providing it with a certain amount of thermal inertia by making it less susceptible to temperature changes. a

The improved cell is capable of producing uncontaminated caustic solution of high concentration. Three of the improvements herein described, i. e., the adjustable overflow outlet for the mercury leaving the oxidizing compartment; theheating pipe; and the pan for supporting the graphite platesin theoxidlzing compartment all contribute toward this result as follows:

The adjustable overflow outlet for the mercury seal enables .the desired relatively-deep layer 01' mercury to be maintainedin the oxidizing compartment thus facilitating denudingot the amalgam and thereby making, it possible to obtain a high strength caustic solution,- The heating p pe lays its part in making it-- a possible to produce caustic solution ofhigh concentration, in' two ways, first, by maintaining-a temperature-in the oxidizing compartment at which the denuding otthe amalgam is most er- 1 fectively accomplished, and second, by prevent- 10 ing.c rystallization oi the high strength caustic after it is produced. -When caustic solution of high strength is being produced the caustic will I crystallize out and deposit unless the solution is heated to approximately -C.. By; the use of 15 the heating pipe the-caustic solution may be, maintained at the proper temperature to prevent such crystallization. 7 The pen eliminates dangenot contamination of the strong caustic solution. If strong'caustic .20 solution is allowed to come in contact with concrete it will dissolve portions of the concrete thereby contaminating the caustic solution. ,The pan eliminates the necessity of setting the graphite plates in concrete as heretofore'andas therefore contamination of the caustic solution by dissolved portions of concrete is avoided, Iclatm: -1. In an electrolyticl cell of the circulating mercury type for producing chlorine and sodium 30 hydroxide from brine the combination of 'an oxidizing compartment, 17; pan in said compartment, graphite in said compartment, said pan-extending in a general horizontal direction and serving as a container for mercury and for said 35 graphite, an inlet for conductingmercury to one part of said pan, an outlet for discharging mercury from another part of the pan whereby substantially the entire flow of the mercury is horizontally over the graphite in the pan from said. 40 inlet to said outlet, means for supporting said pan in spaced relation with the bottom of the oxidizing partment whereby the caustic s p-du solution formed in the oxidizing compartment will occupy the space above and below said pan; 45

'the mercury being discharged from said pan and said compartment without passing into the space below the pan.

2. In an electrolytic cell of the circulating mercury type for producing chlorine and sodium 50 hydroxide from the brine the combination of an oxidizing compartment, a plurality of graphite plates in said compartment, a metallic pan in said compartment, said pan extending in a general horizontal direction and serving as the con- 55 tainer for mercury and for said graphite plates, means for removably clamping the graphite plates in said pan, an inlet for conducting m'ercury to one part of said pan, an outlet for discharging mercury from another part 01 the pan 60 whereby substantially the entire flow of the mercury is horizontally over the graphite plates in the pan from said inlet to said outlet, means for removably supporting said pan in spaced relation with the bottom ofthe oxidizing compart- 65 ment whereby the caustic soda solution formed in the oxidizing compartment will occupy the space aboveand'below said pan, the mercury being discharged from said pan and said compartment withoutpassing into the space below 7t the'pan. e, v

3. Apparatus in-accordance with claim 1 in. which means for heating the caustic soda solution is located in the space below the metallic Dan.

compartment, apan in said compartment, said 4. In an electrolytic cell of the circulating mercury type the combination of an oxidizing compartment, a plurality of graphite plates in said pan extending in a general horizontal direction and serving as a container for mercury and for said graphite plates, an inlet for conducting mercury to one part of said pan, an outlet for discharging mercury from another part of the pan whereby substantially the entire flow of the mercury horizontally. over the graphite plates in the pan from said inlet tosaid outlet, means for supporting said pan in spaced relation with the bottom ofthe oxidizing compartment, at least one member. extending transversely under. the pan, at least one member extending transversely .over the pan, means to draw said members toward each other, and a clamping element disposed between the upper member and the graphite plates whereby the graphite plates will be clamped in the pan when said members are drawn toward each other, the mercury being discharged from said pan and said compartment without passing into the space below the pan.

' 5. In an electrolytic cell of the circulating mercury type the combination of an oxidizing comoverthe pan, means connected to said members to draw the upper member toward the lower member, and means whereby the drawing of the .upper member toward the lower member-clamps the graphite plates in said pan, the mercury being discharged from said pan and said compartment without passing into the space below the vI 6. In an electrolytic. cell of the circulating mercury type the combination of an oxidizing compartment, graphite in said compartment, said pan extending in a general horizontal direction and serving as a container for mercury and forsaid graphite, an inlet for conducting mercury to one part of the pan, an outlet for discharging mercury from another part of the pan whereby substantially the entire flow of the mercury-is horizontally over the graphite in the pan from said inlet to said outlet, a plurality of members spanning the oxidizing compartment and extending transversely under the pan and on which said pan' is supported, and a plurality of members extending transversely over said pan and cooperating .with the /first mentioned'members to clamp the pan thereto, the mercury being discharged from said'pan'. and said compartment without passing intothe space below the pan.

7 In an electrolytic cell of the circulating mercury type for producing chlorine and sodium'hy- I droxide from brine, the combination of an oxicompartment, a receptacle extending in a general horizontal direction in said compartment 1 and serving as a container for said graphite and for mercury, the surface of said receptacle being substantially. unafiected, by sodium hydroxide solution, aninlet for conducting mercury to' one part of said receptacle, a mercury seal through which the mercury is discharged from another part of the receptacle whereby substantially the .dizing compartment. graphite in the oxidizing entire flow of the mercury is horizontally over the graphite in the receptacle from said inlet to said mercury seal, said mercury seal having a vertically adjustableoverflow outlet whereby the mercury in the receptacle may be maintained at a predetermined level and in a relatively deep layer, and means in theoxidizing compartment for heating the sodium hydroxide solution therein, the mercury being discharged from. said receptacle and said compartment without passing into the space below said reteptaclei 8. In an electrolytic cell of the circulating mercury type for producing chlorine and sodium hydroxide from brine the combination offan oxidizing compartment, a pan I in said compartment, graphite in said compartment, said pan extending in a general horizontal direction and serving as -a container for mercuryand for said graphite,

an inlet for conducting mercury to one part of said pan, a mercury seal through which mercury is discharged from another. part of the pan' whereby substantially the entire flow of themercury is horizontally over the graphite in the pan from said inlet to said outlet, means for supporting said pan in spaced relation with the bottom of the oxidizing compartment, whereby the caustic soda solution formed inthe oxidizing compartment will occupy the space above and below said pan, the mercury being discharged from said pan and said compartment without passinginto-the space below the pan.

, EINAR SORENSEN.

CERTIFICATE OF CORRECTION.

, December 51, 19140. EINAR SORENSEN.

Patent 110.. 2, 226,78h.

ofthe aoove numbered patent requiring correction as follows: Page 1, first column, line 55, for the word "compartments" read "compartment-w; page 11., first column, line t9, claim 6 after "compartment," insert -apan in said compartment,-; and that the said Letters Patent should be read with this correction therein that the same may conform to the record ofthe case in the Patent Office.

Signed and sealed this hth day of February, A. D. 1914.1.

It is hereby certified that error appears in the printed specification Henry Van Arsdale, (Seal) a Acting Commissioner of Patents.

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