US2104678A

US2104678A - Electrolytic cell

Info

Publication number: US2104678A
Application number: US81344A
Authority: US
Inventors: Sorensen Einar
Original assignee: Oxford Paper Co
Current assignee: Oxford Paper Co
Priority date: 1935-10-01
Filing date: 1936-05-23
Publication date: 1938-01-04
Anticipated expiration: 1955-01-04

Description

Q MK 5 sheets-sheet 1 v INVENTOR' m'. kfz Z ATTORNEYS.

E. SORENSEN ELECTROLYTIC ,CELL

original Filed oct. 1, 1935v Jan. 4, 1938.

Jan. 4, 1938. E. soRENsEN Z04y578 y ELECTROLYTIC CELL i Original Filed 0G13. 1, 1935 5 ShGe'tS-Shet 2 llllll may@ f4 fa ATTO R N EYS jan. 4, 193.- E. soRENsEN ELECTROLYTIC CELL Original Filed Oct. l, 1935 3 Sheets-Sheet 3 INVENTOR M /M BY v M ATTORNEYS,

Patented Jan. 4, 1938 UNITED STATES EIECTBOLYTIC CELL Einar Sorensen, Rumi'ord, Maine, assignor to Oxford Paper Company, a corporation oi Maine original appncaaon october 1, 1935,'ser1a1 No.

1936, Serial N0. 81,344

Divided and this application May 23,

- 4mm. (creci-53)r This application is a division of my copending application Serial No. 43,027 iiled October 1, 1935. The invention relates to electroiytic cells for producing chlorine and sodium hydrode from 5 brine. Such a cell isdisclosed in my prior Patent #1,613,966, issued January l1, 1927. The cell of the present application, in general construction and operation, is 'similar to the cell of my prior patent, but embodies certain improvements hereinafter described and claimed.

The cell disclosed in the above-mentioned pat- 'ent comprises a casing having a longitudinal partition which divides the cell into a decomposing compartment and an oxidizing compartiment. Brine, to be treated, enters the decomposing compartment, the oor of which is-covered with a slowly moving layer of mercury which constitutes a cathode. Graphite plates located above the mercury constitute the anode. Electric current passing between the graphite plates and the mercury liberates chlorine from the'brine and the mercury forms an amalgam with the sodium of the brine. The amalgam iiows out of the decomposing compartment into the oxidizing compartment where it passes over notched graphite plates. Measured quantities of water are fed into the oxidizing compartment. By the action set up in the oxidizing compartment the amalgam is decomposed and the sodium reacts with the water to form sodium hydroxide solution. The mercury thus freed of its sodium Vthen enters a pump chamber in which a rotary pump lifts the mercury and returns7 it to the decomposing compartment. 3.', This application is directed particularly to the anode and cover assembly of the decomposing compartment, the object being to improve the construction and functioning of that part of the apparatus.

An electrolytic cell embodying the invention is shown in the accompanying drawings, but it is to be understood that the anode land cover assembly comprehended by this invention may be used with cells differing very materially :from 5 the one illustrated. The particular cell shown in the drawings is an improvement upon the cell shown in my prior patent above referred to not only with respect to the cover and anode assembly herein claimed, but also as to certain other features disclosed but not claimed herein but claimed in my parent application Serial No. 43,027, above referred to, and in other divisions of the apparent application, Serial No. 86,725, led June 23, 1936; Serial No. 93,580, iiied July 31, 5 1936 and Serial No. 97,884, iiled Aug. 26, 1936.

In the drawings: l

Figure 1 is a. plan View of the cell with the cover and the anode assembly of the decomposing compartment removed to expose to view the interior construction of this compartment; 6

Fig. 2 is a longitudinal section through the decomposing compartment taken on the line 2-2 of Eig. l. In this view the cover and the anode assembly are in place;

Fig. 3 is a longitudinal section through the 1Y0 oxidizing compartment taken on the line 3-3 of Fig. 1;

Fig. 4 is a detailed sectional view of one end of the oxidizing compartment taken on the line Y 4 4 of Fig. 1; 15

' Fig. 5 is .a sectional view similar to Fig; 4

taken on the line 5-5 of Fig. 1;

Fig. 6 is a transverse section taken on the line 6-6 of Fig. 1; 'e

Fig. 7 is a transverse section taken just to the 20 rear of the section of Fig. 6, i. e., on the line 1-1 of Fig. 1;

Fig. 8 is a transverse section taken just to the -rear of the section of Fig. 7, i. e., on the line 8-8 of Fig. 1, and v Fig. 9 is a. transverse section taken on the -iine 9 9 of Fig. l. Y

The improved cell has an external metal casing l which is generally rectangular in shape as shown in Fig. 1. It is divided into two compart` 30 ments by a longitudinal partition 2. One of these compartments, designated 3, is the decomposing compartment and the other one designated 4 is the oxidizing compartment. As best shown in Figs. 6 to 9, inclusive, that part of the 35 metal casing -which houses the oxidizing compartment projects downwardly to a lower level than the part of the casing which houses the decomposing compartment. This is indicated at 5 in Figs. 6 to 9. The metal casing is lined 40 along the inside walls and over the bottom with concrete 6 and is properly molded to form the various passages and seals hereinafter described.

vBrine to be treated enters the decomposing compartment through an inlet 1 (Figs. 1 and 2). 45 The mercury enters the decomposing compartment from the oxidizing compartment at 8. 'Ihe mercury passes in a thinlayer over the bottom of the decomposing compartment in the manner to be hereinafter described and is discharged 50 through the passage 9 (Figs. 1 and 9) into the oxidizing compartment. The mercury in the decomposing compartment forms the cathode of an electric circuit,- the anode being graphite plates I9 supported with their lower faces just above 55 1 peripheral pockets 2I (Fig. 6) to which the mercompartment.

In the oxidizing cell the mercury amalgam passes over the notched graphite plates I2. Measured quantities of water arev fed into this compartment by means to be hereinafter de-A scribed to maintain in this compartment a predetermined density and to compensate for the water consumed in the displacement action. The displacement action which takes place in this cell frees the amalgam of its sodium and causes the sodium to unite with the water to form sodium hydroxide solution. The sodium hydroxide solution is withdrawn from the oxidizing compartment through a. pipe I3 (Figs. l and 9) which discharges into the lower end of receptacle I4. This receptacle has a vertical partition I5 dividing it into two compartments. The sodium hydroxide solution enters the bottom of the right hand compartment (asviewed in Fig..l) and flows over the upper edge of the partition I6 into the left hand compartment. It is then discharged through an outlet pipe I6 in the bottom of the left hand compartment. In the right hand compartment there may be located a hydrometer I1 (Fig. 9) by which the density of the sodium hydroxidesolution may be measured. The level of the sodium hydroxide solution in the oxidizing compartment is determined by the elevation of the upper edge of the partition I5. lTherefore, the level of the sodium hydroxide solution in the oxidizing compartment may be varied, if desired, by raising or'iowering the receptacle I4 and thereby raising or lowering the elevation of the upper edge of the partition I 6. This` may be effected by providing the pipe I3 with a removable section I8 which/may be `re placed by a longer or shorter section.

.The mercuryfreed of its sodium passes into a pump well, I9. A rotary pump 20 lifts the mercury from the well and dischargesit at a higher elevation where it ows into the passage 8 bf the decomposing compartment thereby completing the cycle. The pump has a series of cury is admitted through peripheral openings 22. It is discharged from these' pockets through openings 23 (Figs. '1 and 8) in the lateral wall of the pump. It is then caught in the manner 'hereinafter to be described and passed on to the decomposing compartment. The mercury pump is operated by a sprocket wheel 24 connected by means of a chain 2,5 (Fig. v6) to a sprocket wheel 26 (Fig. 3) on a drive shaft 21 driven in any suitable manner. A

The water to be supplied to the oxidizing compartment first enters la receptacle 28 through a pipe 29. A pipe 30 having anelbow 3i at its outer end, which forms a small bucket, is oscillated so that it dips down into the water in the receptacle 23 and then as the pipe rises the water flows through the pipe and is discharged from the inner end 32 of the pipe into another compartment 33 of the receptacle 23. The pipe 30 is mounted on a horizontal shaft 34 to the outer end of which is 'connected an arm 36. 'I'his arm is engaged and deflected by a projection 36 associated with the sprocket wheel 24 so that every time the sprocket wheel makes one'revolution the pipe`33 is lifted to scoop up a small portion of water and dump it in the compartment 33.

From the compartment 33 the water passes through a pipe 31 directly into the pumpvwell I3. The pump picks up both the mercury and the water and the manner in which the water and mercury are separated so that the water is delivered to oxidizing compartment and the mercury delivered'to the decomposing compartment will be hereinafter described.

As thus far described the electrolytic cell is substantially the Isame in construction and oper- The use of steel instead of cast iron greatly reduces its cost. Convenient and inexpensive manufacture isA made possible by maintaining straight lines throughout its construction. 'Ihe casing is shaped to conform with the mercury flow arrangement.

A three point support is used for 4,the cell in order to maintain even bearing andv to facilitate releveling of the cell should this become necessary. The three supports are shown at 31, 33 and 39 in Figs. 2, 3 and 9. As best shown in Fig'. 9 each support comprise a hemisphere 43, preferably made of metal, the flat side of which is secured to the bottom of the casing I and the curved surface of which rests in the opening 4I of a metallic member 42 which might conveniently be a pipe flange. The member 42 rests on a glass insulating plate 43 which in turn is supported on top.of the cell leg 44. The three point support insures'that the cell will be hrm and -steady notwithstanding any irregularities in the floor. If it is desired to relevel the cell this may be done by replacing thepipe flange 42 or the 4glass plate 43 with a thinner or thicker one at any of the three supports where it is desired to make the adjustment.

Thedecomposing compartment 3 is constructed in such a manner as to provideand maintain a continuous, undivided flow' of a. uniformly thin layer of mercury through the compartment at a suitable distance-from the anodes and in conv formity with their area. The floor of the decomposing compartment is divided into three

adjacent channels

45, 46 and 41 (Fig. l) by a pair of longitudinally extending

ribs

43 and 43. These ribs may be molded from the concrete which lines the casing of the decomposing compartment, as best shown in Figs. '1, 8 and 9. The outermost channel 45 communicates with the 'transverse passage 3 through which the mercury enters the decomposing compartment. The

channels

45 and 46 communicate with each other at the right hand end of the cell, as viewed in Fig. 1, and the

channels

46 and 41 communicate with each other at the left hand of the cell, as viewed in this figure. 'I'he right hand end of the channel 41 communicates with the passage 3 through which'the mercury leaves the decomposing compartment. The mercury, therefore, follows a tortuous' passage as follows: From the entrance passage 3 it passes-to the right (as viewed in Fig. 1). through the channel 46. then to the left through `channel 46, and then tothe rightthrough channel 41 and is then conducted by the passages into the'oxidizing compartment.

'I'he floors of the

channels

45, 46 and 41 are level Iin both directions which necessitates a slight head of mercury at the inlet of the first channel in order to obtain a ow of mercury through the compartment. By using level instead of pitched oors the amount of mercury which it is necessary to use maybe greatly decreased and still maintain ilow of a continuous undivided and uniformly thin layer of mercury through the combined lengths of the channels.

By reference to Figs. 7, 8 'and 9 it will be seen that the channel 46 is at a lower level than the channel 45,' and the channel 41 is at a lower level than the channel 46. At the right hand end of where the mercury and amalgam cascades to the level of the passage 9. These steps, or drops, facilitate the flow of the mercury and decrease.`

the total amount of mercury necessary for operation of the cell.` They also cause an eilicient mixing of the amalgam with the free mercury.'

This mixing of the amalgam and the free mer-V cury is further promoted by the change in direction of flow as the mercury and amalgam pass from one channel to the next. l

It will be noted that the mercury is not subdivided at the entrance end of the decomposing compartment into several parallel streams which ow in the same direction through the decomposing compartment as in the cell disclosed in my prior patent, but there is one undivided stream which follows a tortuous path through the decomposing compartment. This makes it possible to eliminate the dams which have sometimes been found necessary at the outlets of the channels when the mercury is subdivided and flows through the channels in the same direction. When the mercury is thus divided between a plurality of channels the mercury has insufdcient ow through any one of the channels to maintain a uniform and continuous layer of mercury over the channel oors unless dams are used. Moreover, the ilow'of the mercury in that type of cell is not positive in action because deposition of graphite and other impurities cause scum formation at the inlet to the channels thus causing uneven distribution of the mercury between the channels and thus results in too much mercury flow through certain channels while too little flows through others. Positive and uniform fiowof the mercury is obtained by the channels communicating in series rather' than in parallel. In the improved cell herein disclosed the rate of flow of the mercury through .the decomposing compartment is controlled by the amount in excess of that necessary to cover the floor of the channels of the. decomposing compartment and the slotted graphite plates of the oxidizing compartment.

The anodes do not rest upon projections on the floor of the decomposing compartment as in the-y cell of my prior patent, but are rigidly fastened to, and suspended from, the cover of the decom-l posing compartment and form a unit therewith. The cover of the decomposing compartment is' shown at 53 (Fig. 2). It may be made oi light materiaL such as impregnated'brc. Inasmuch as thecover is called uponto support the anodes,

Ait is preferably reinforced by transversely extendingangle irons 64 and longitudinally extending angle irons 65. The cover 53 is supported at its `edges on the concrete'walls of the cell by means of fibre strips 56. As the anodes'wear down, the bre strips A56V may be removed one. at a time, thus lowering the anodes and restoring the proper Aspacing between them and the mercury cathode.l Each graphite anode i0 is rigidly secured to the cover 53 by *a graphite lead 51 threaded at both ends. The lower end of the lead 51 is screwed into the anode i0, as shown at 58 and the upper end of the lead passes through an opening in the cover 53 land -isV clamped to the cover by a fibre nut 591 Inthe particular cell shown in the drawings thereare three anode plates in each channel v'thfus making nine alltogether. The three anode plates ofeach transverse row are electrically connected by means oi a metallic conducting strip 60 (Figs. 2 and 9) which is secured to the graphite leads 51 by means of stud bolts 6i. Three bus bars 62 conduct current to the three transverse rows oi.'` anodes.

- The cover and anode assembly may be easily removed as a unit when it is desired to clean the cell. The cover is much lighter than the con- ]crete covers vheretofore used thus facilitating its removalu` Due to the fact that all joints in the cover assembly prevent substantial infiltration of air it is possible to produce higher concentration chlorine gas.

bedded inthe concrete oor of the decomposing compartment are a series of transversely extending metal bars or strips 63 (Figs. l and 2) These are supplied Vwith current by a bus bar 64. Bolt terminals 64a are screwed and .welded to the transverse bars 63 and extend through the metal container and are secured to the bus bar 64 by means 'of nuts 64b. Over each metal bar 63 the concrete oor is provided with a series of holes 65 by means of which the mercury makes contact with the bar.v The path of the current is therefore from the bus bar 64 to the bolts 64a, to the transverse bars 63, then to the mercury cathode, through the .brine to the graphite anodcs i0, then through the leads 51 and connecting strips 60 to the bus into the glass tube 68 by a small glass pipe 63 communicating 'with thebrine supply pipe. vThis arrangement serves the purpose of sealing the brine inlet thus preventing air from entering the cell. It also minimizes electric current leakage as the brine is caused to fall through the air for a short distance in a somewhat dispersed column as it leaves the discharge end of the small glass pipe 69.

After the mercury leaves the decomposing compartment and before it enters the oxidizing com- `l partment it forms a seal and thereby prevents brine from passing lfrom the decomposing compartment to the oxidizing compartment. This seal is therefore vcalled the brine seal and is constructed as follows: At the right lhand end of the oxidizing compartment 4 (aspviewed in Fig. l)4

CII

there is a pit or well molded\in the concrete lining. In plan view this well is relatively narrow longitudinally of the cell and is relatively long transversely of the cell. The bottom of the well is'tapered to form la V as shown at 1I in Fig. 9, the taper being in such a direction that the mercury passing from the decomposing compartment through the passage 9 will flow down one of the arms ofthe V. Y

' The well 1li forms one of the chambers of the brine seal, the other chamber, shown at 12 (Figs. 1 and 3) being a pit located in the oor of the oxidizing compartment. The bottom of the well 10 communicates with the pit 12 through an opening 13 extendingthrough the wall 14 that separates the well 1U from. the oxidizing compartment. It is obvious from this arrangement that a body of mercury will be maintained in the

chambers

10 and 12 of the seal at a constant level. As the mercury is continuously fed into'the well 10 it is continuously discharged from the pit 12 into the oxidizing compartment. The body of mercury maintained in this manner by the

seal chambers

10 and 12 prevents any brine fromA entering the oxidizing compartment.

It will be noted that the mercury enters the well 10 in the lengthwise direction of the well but in a direction transverse to the axis of the opening 13. The mercury thus passing into the vwell 10, down one side of the V-shaped, bottom trate and remove the dispersed or broken up mercury for otherwise it will pass into the oxidizing compartment through the seal and may entrain some of the brine. Furthermore, any dispersed mercury which ilnds its way into the oxidizing compartment will remain in suspension in the sodium hydroxide solutiony and pass oif .with it thereby causing a continuous loss of mercury. The outer wall of the Well 10 has a norl mally closed pipe 15 extending through it which communicates with the interior of the well and aiords a convenient outlet for the wash water during wash-ups. Moreover, by discharging the wash water through the pipe 15 it is prevented from entering the oxidizing compartment.

In the oxidizing compartment hydrogen gas is liberated when the sodium is freed from the amalgam and unites with water to form sodium h'ydroxide solution. In order to prevent entrainment of caustic by the hydrogen gas thus liberated, an oil layer 16 (Fig. 3) is formed by iloating on the surface of the caustic liquor an oil which is completely inert toward the caustic. Prevention of entrainment of caustic by the hydrogen gas which is liberated to the cell room atmosphere is an important consideration from a health standpoint. It also decreases the loss of caustic.

In passing from the oxidizing compartment into the pump well, the mercury forms a second seal called the caustic seal because it prevents caustic from passing along with the mercury to the pump well. This sealcomprises a pit 11 molded Y in the concrete door oi' the. icompartment and a pit 1l molded in the v crete oor of the pump well (Pigs. 3 and 5). Communication between these two pits is established by a passage 19 in the wall Il which separates the oxidizing compartment from the pump well. The body of mercury maintained in the chambers 11 and 1I at a constant level constitutes a seal similar. to the one previously described. As the mercury is continuously fed into the compartment 11 it is continuously discharged from the compartment 1l into the well of the mercury pump but no caustic can pass into the pump well.

As previously stated the rotary mercury pump 20 picks up the mercury in the pump well and also the water which has been fed to the pump well by the water bucket 3| already described. The mercury and water, discharged through the lateral openings 23 in the side wall of the pump, falls into a transverse trough il (Figs. 1, 3, 5 and 7) which conducts them to a third mercury seal called the water` seal because it prevents the Water from passing along with the mercury into over the edge l5 of the pit I3 (Fig. 6) and then passes into the transverse passage 8 which conducts the mercury to the first channel of the decomposing compartment. The water held back by the seal l--ll and which oats on top of the mercury as it passes through the trough Ii is conducted through a short passage 8i and discharged directlyto the oxidizing compartment (Figs. 1 and 8).

The trough Il is so arranged as to minimize splash of the mercury as it is discharged from the pump 20. splashing of the mercury at this point would be harmfulas it would cause breaking up or dispersingof the mercury or would also augment vaporization. Prevention of vaporization of the mercury is very important'from a health standpoint. A spill plate 81 (Figs. 1 and 3) extends from the bottom of the trough Il to a point 'closely adjacent the discharge outlets 2l of the pump to prevent spill of the mercury back into the pump well. 'I'he water in the trough Il (supplied by the oscillating bucket Il' to the pump well and delivered by the pump. tc the trough 8l) acts as a cushion for the falling mercury. It also acts as a wash and a. submerging cover for the mercury during its travel to the water seal 82-83--84.

A As previously described the oscillating water bucket 3| supplies a uniform and measured quantity ofwater to the oxidizing compartment. As the water is ilrst delivered to the pump well it keeps the mercury in the pump well and in the pockets of the pump covered. with water and thereby prevents vaporization of the mercury and the consequent'contamination of the room atmosphere.

Iclaim:

1. An electrolytic cell having a decomposing,

compartment and an oxidizing compartment through which mercury'may be circulated, a removable cover for the decomposing compartment made of light fibrous material, a plurality of metallic reinforcing bars strengthening said cover, and a plurality of anodes rigidly secured tc the cover and supported solely thereby and rqnovable with the cover as a unit.

2. An electrolytic cell having a decomposing compartment and an oxidizing compartment through which mercury may be circulated, a removable cover for the decomposing compartment made of light fibrous material, reinforcing means associated'with the cover adapted to resist bendfing thereof, and a plurality of anodes rigidly secured to the cover and supported solely thereby rigidly secured to the cover and supported solely thereby and removable with the reinforced cover as a unit.

4. An electrolytic vcell having a decomposing compartment and an oxidizing compartment through which mercury may be circulated, a removable cover for the decomposing compartment made of light fibrous material, a reinforcement strengthening the cover comprising one set of angle irons extending across the top of the cover and a second set of angle irons superposed on the first set and extendingat right angles thereto, and a plurality of anodes rigidly secured to the cover and supported solely thereby and removable with the reinforced cover as a. unit.

EINAR soRENsEN.