US2282058A

US2282058A - Electrolytic cell

Info

Publication number: US2282058A
Application number: US252634A
Authority: US
Inventors: Ralph M Hunter; Lawrence B Otis; Robert D Blue
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1939-01-24
Filing date: 1939-01-24
Publication date: 1942-05-05
Anticipated expiration: 1959-05-05

Description

R. M. HUNTER ETAL May 5, 1942.

ELECTROLYTIC CELL Filed Jan. 24, 1939 3 Sheets-Sheet 1 III 5 s W M 16 M W m vv m 7 Nm N v nni 5 w m m MM Em I A n A E E E r wfi E E E 3 3 E B E 3 E 3 3 Z Y 2 E E 3 my 3 E 3 F/ E 2 E 3 3 3 E 2 E 3 3 E =3 E 3 a |Y6 MW 5 w May 5, 1942. R. M. HUNTER ETAL ELECTROLYTIC CELL Filed Jan. 24, 1959 3 Sheets-Sheet 3 9 4 5 9 5 w m d; 1; 3w 0 o o M\ o, m 5r 5 W E 0 5 p 0 0 m 0 a E O 7 f L m 5 2 M 4 6 5 5 u, i 5 H 5 1d 5 w .10 z w m; w

INVENTORSI n/ A. ner @2 ago Patented May 1942 T OFFlCE ELECTROLYTIC CELL Ralph M. Hunter, Lawrence B. Otis, and Robert I D. Blue, Midland, Mich assignors to The Dow Chemical Company, Midland, Mich., a corporation of Michigan Application January 24, 1939, Serial No. 252,634

8 Claims.

This invention concerns an improved electrolytic cell for the production of chlorine and caustic soda from brine.

An object of the invention is to provide an electrolytic cell having a low internal resistance, a high power-efficiency, and a low heat loss. Another object is to devise a highly compact cell having large productive capacity per unitfloor area. Still another object is to provide a cell of rugged design which may be readily assembled, and on which maintenance charges are low. A further object is to .design a cell which requires a minimum of investment in associated equipment such as pipe lines, electrical connections, etc.

In attaining these objects, we employ an improved cell of the filter-press, bipolar electrode type. This type of cell, as is well known, consists of a series of abutting frames or unit cells, each comprising one cathode and one anode, the anode of one unit cell being electrically connected within the cell frames to the cathode of the succeeding unit cell. In the present invention, each unit cell is a pocket or interleaved cell. Further, in the invention, the'anode of each unit cell also serves as the partition or separator between successive unit cells.

One form of cell embodying the principles of the invention is shown in the accompanying drawings in which: I

Fig. 1 is a plan view of an electrolytic cell assembly comprising for purpose of illustration four v unit cells and two end units, with the cell cover in place;

Fig. 2 is a transverse sectional elevation of the cell, with cover in place, taken along the line 2-2 in Figs. 1 and 3;

Fig. 3 is a longitudinal sectional elevation of the cell taken along the line 3-3 in Fig. 1;

Fig. 4 is another transverse sectional elevation of the cell, with cover removed, taken along the line 4-4 in Figs. 1 and 3, showing the cathode structure, and showing the cathode removed, exposing the anode partition;

Fig. 5 is a plan view 01' a unit cell;

Fig. 6 is a sectional view of a unit cell, taken along the line 66 in Figs. 2 and 4;

Fig. 7 is a plan view of a single cathode fin showing portions of the cathode covering cutaway; and

tion.

Referring particularly to Figs. 1 to 4, the electro ytic ce c sists oi a s of u t ce ls H (four are shown), and two dummy end cells I2 and I3, all resting on insulating skids I4 and held together between buckstays l5 by tie-bolts 6. All joints between unit cells are made fluidtight by suitable sealing compound.

Each unit cell is enclosed by a frame ll of mm conducting material, such as concrete, in which is mounted an anode partition I8 and a cathode structure I9, dividing the unit cell into an anode chamber 20 and a cathode chamber 2|. Fresh electrolyte is supplied to and gaseous products are withdrawn from the anode chamber 20 through throats 22 opening into a header 23. This header is formed by a cover 24 which extends the entire length of the cell assembly, and rests on each frame between lugs 25, the cover being made leak-proof by sealing compound 26. The header 23 is divided by partitions 21 into a series of header chambers 28, one for each unit cell, the chambers being in communication with one another through an upper gas port 29 and a lower brine port 30 in each partition. Holes 3| in the cover, normally closed with plugs '32, permit cleaning of the throats 22. Gaseous products formed in the cathode chamber 2| are collected through slots 33 into a smaller header 34 formed by hollow heads 35 cast integral with the cell frames I1, and provided with cleaning holes 36 which are ordinarly plugged. Both anode and cathode chambers have

drains

31 and 38, the cathode drain 31 being always open through a suitable liquid seal and the anode drain 38 being opened only when the cell is cleaned. Each unit cell may be handled by metal lugs 39 anchored firmly in the frame l1.

The anode partition 18 in each unit cell, as particularly illustrated in Figs. 3 to 6, is a segmented structure made up of alternate vertical spacers 4|] and vertical boards or plates 4| cast securely at topv and bottom into the concrete frame near one face thereof and extending across the entire frame. Both the spacers 40 and the plates 4| are made of graphite or other electrically conducting chlorine-resistant material; thus providing a maximum effective anode area and an even distribution of current over the anode surface. As will be seen from Fig. 6, the spacers 40 lie in a common plane, but the plates 4| are thin boards extending normally to the plane of the spacers, thus forming a series of anode pockets, into-which the cathode fins hereinafter described may project. As shown in Fig.

3, the anode plates 4| do not extend into the concrete frame throughout their entire' width, but are chamfered at top and bottom to permit free circulation of fluids within the anode chamber. In fabricating a unit cell, the spacers and anode plates 4| are compressed together to form a fluid-tight partition and the concrete cell frame is then cast around the anode structure to hold it rigidly in position.

. As will be evident from the foregoing, the anode structure It! in each unit cell not only is a pocket-type anode, but also serves as the partition between the anode chamber of one unit cell and the cathode chamber of the adjacent cell. That is, the rear side of each anode itself serves as one wall of the cathode chamber of the ad- J'acent unit cell. The construction of the anode II! in each cell is not limited to the preferred segmented structure illustrated, but may take other forms, as for example, a solid graphite partition with parallel vertical graphite boards or vertical rows of pins fixed at regular intervals to one side thereof and extending into the anode chamber to form pockets. In essence, the anode structure according to the invention can be considered as a graphite partition having a plurality of spaced parallel transversely disposed graphite members projecting from one face of said partition. This novel pocketed anode construction is an essential feature in the compactness and efiiciency of the present electrolytic cell.

The cathode structure IQ of each unit cell, shown in assembly in Figs. 3, 4 and 6 and in detail in Figs. 7 and 8, consists essentially of a coarse steel wire screen 42 to which are secured a plurality of inwardly directed vertical hollow fins 43 spaced along the screen at intervals corresponding to the spaces or pockets between the plates 4| of the anode partition l8. The cathode screen 42 is secured at its outer edges to a metal framework 44 which fits into a recess on one side of the unit cell so as to be flush with the face of the frame and is held in place by bolts 45 embedded in the concrete. Th cathode fins 43 are also constructed of metal screen 46 folded to form narrow trough-like pockets open only along one vertical edge and of approximately the same height as the anode plates 4|. These fins are secured at their open edge along the cathode screen 42 by bolts 41 welded at spaced intervals to the inside of the pocket screen 46. To permit ready flow of catholyte and gases formed within the cathode fins 43 into the cathode chamber 2|, narrow slots 48 are cut in the cathode screen 42 to register with the space inside the leaves. This entire cathode assembly need not be made of wire screening but may, of course, be constructed of perforated sheet iron or other suitable foraminous material which is the substantial equivalent of screening. The cathode structure thus comprises a metal screen having attached thereto on one face thereof a plurality of spaced parallel transversely dispersed hollow screen fins. In the assembled cell, all portions of the cathode screen 42 and fins 43 exposed to the anode chamber are covered with a permeable diaphragm 49, such as one or more layers of asbestos paper, which serves to prevent intermixing of fluids from the anode and cathode chambers.

In each unit cell, the cathode fins 43 project into the pockets between the anode plates 4 I, i. e. the cathode fins alternate in closely spaced relation with the anode plates. Each unit cell is thus a pocket or interleaved cell as shown in Fig. 6.. The space between the anode partition I8 and the anode plates 4| and the cathode screen 42 and cathode fins 48 of each unit cell forms the anode chamber 20, and is filled at all times with electrolyte. The space between the cathode screen 42 and the anode partition i8 of the adiacent unit cell is the cathode chamber 2|.

In the assembled electrolytic cell, electrical connection between abutting unit cells in the series is made by a plurality of male and female copper spring clips or contaetors 50 and 5| which fit together by frictional contact as shown in detail in Fig. 8. In the assembly shown, (Figs; 2 to 6), three female clips 5| are secured to each anode plate 4|, and the same number of male clips 50 are secured to the cathode screen ciently flexible for adjusting slight variations in alignment of the frames II when these are assembled into the complete electrolytic cell. In our invention, all electrical contact between unit cells is made within the cell frame, the cathode assembly I 9 of one unit cell and the anode structure l8 of the adjacent unit electrically connected thereto forming in effect a bipolar electrode, no

external connections being necessary.

Electrical energy for the entire electrolytic cell enters and leaves through terminals 52 mounted on the dummy end cells I 2 and I3, and adapted to receive cables from any suitable source of direct current. These terminals 52 extend through the dummy cells to distributor bars 53 which carry the electriccurrent to bus-bars 54 mounted on channel irons 55 embedded in the dummy cell frames. Spring clips 50 and 5|, identical with those employed between unit cells, are mounted on the bus-bars 54 in such positions as to make contact with the corresponding spring clips on the terminal unit cells.

In operating the electrolytic cell, the anode chambers 20 of the unit cells are kept full of electrolyte at all times, and the header chambers 28 are kept partly full, by introducing brine into the header 23 continuously at a controlled rate through one of the holes 3| by means not illustrated. In each unit cell, the brine gradually percolates through the cathode diaphragm 49 into contact with the cathode screen 42 and cathode fins 43, and is there transformed by the electric current flowing through the cell into gaseous hydrogen and a solution of caustic soda. The hydrogen thus liberated in the cathode chamber 2| escapes upwardly through the cathode slots 33 into the small header 34 and is withdrawn through suitable conduits not shown. The caustic soda solution trickles down the walls of the cathode chamber 2| and out the cathode drain 31 to a trough or other collecting means. Likewise during electrolysis, the brine in the anode compartment 20 of each unit cell is transformed at the surface of the anode spacers 40 and anode plates 4| into gaseous chlorine which bubbles upwardly through the anode throats 22 into the intercommunicating header chambers 28 from which it may be removed and collected by any desired means.

Other modes of applying the principle of the invention may be employed instead of those explained, change being made as regard the details aasaoea disclosed, provided the elements stated in any of the following claims or the equivalent of such elements be employed.

We claim:

1. An electrolytic cell series of the bipolar electrode filter-press'type comprising a plurality of unit cells, each unit including in ccmbintion: a frame of non-conducting material; an anode structure secured in the frame and functionin also as the sole partition between the unit cell and the adjacent unit and composed of an imperforate partition having a plurality of spaced parallel graphite members disposed transversely to and projecting from one face of said partition; a cathode structure secured in the" frame and comprising a flat metal screen having secured thereto on one face thereof a plurality of spaced parallel closed hollow screen fins disposed transversely to the screen and entering the spaces between the graphite members projecting from the anode partition; and a permeable diaphragm covering said cathode structure; electrical constructure in each unit cell with the rear face of the cathode structure in the adjacent unit by direct physical contact; and terminals connecting the end unit cells with a source of current.

2. An electrolytic cell series of the bipolar electrode filter-press type comprising a plurality of unit cells, each unit including in combination: a frame of non-:conducting material; an anode structure rigidly secured in said frame and functioning also as the sole partition between the unit cell and the adjacent unit, and composed of an imperforate graphite partition having a plurality of spaced parallel graphite plates disposed transversely to and projecting from one face of said partition; an opposed cathode structure secured in said frame comprising a fiat metal screen having secured thereto on one face thereof a plurality of spaced parallel closed hollow screen fins disposed transversely to the screen and entering the spaces between the graphite plates projecting from the anode partition; and a permeable diaphragm covering said cathode structure; metal electrical contactors connecting the rear face of the anode structure in each unit cell to the rear face of the cathode structure in the adjacent unit by direct physical contact; and terminals for connecting the end unit cells with a source'of current.

3. An electrolytic cell series of the bipolar electrode filter-press type comprising a plural ty of abutting unit cells, each unit including in combination: a frame of non-conducting material; an anode structure rigidly secured wholly within the frame and functioning also as the sole partition betwen the unit cell and the adjacent unit, said structure being composed of an imperforate graphite partition having a plurality of spaced parallel graphite members disposed transversely to and projecting from one face of the partition; an opposed cathode structure secured wholly within the same frame and comprising a flat metal screen having secured thereto on one face thereof a plurality of spaced parallel closed hollow screen fins disposed transversely to the screen and entering the spaces between the graphite members projecting from the aforesaid anode partition; and a permeable diaphragm covering said cathode structure; flexible metal electrical contactors wholly within the assembled cell frame and connecting the rear face of the anode structure in each unit cell frame to the rear face of the cathode structure in the adjacent cell tact means connecting the rear face of the anode frame by directphysical contact; and terminals connecting the end cells with a source of current.

4. An electrolytic cell series of the bipolar electrode filter-press type comprising a plurality of abutting unit cells, each unit including in combination: a frame of non-conducting material; an anode structure rigidly secured wholly within the frame and functioning also as the sole partition between the unit cell and the adjacent unit, said structure being comprised of animperforate vertical graphite partition having a plurality of spaced parallel graphite members disposed transversely to. and projecting from one face of the partition; an opposed cathode structure removably secured wholly within thesame flexible metal electrical contactors wholly within the assembled cell frames connecting the rear face of the anode structure in each unit cell frame to the rear face of the cathode structure in the adjacent cell frame by direct physical contact; and terminalsconnecting the end cells with a source of current.

5. An electrolytic cell series of the bipolar electrode filter-press type comprising a plurality of unit cells, each unit including in combination: a frame of non-conducting material; an anode structure rigidly secured in said frame and functioning also as the sole partition between the unit cell and the adjacent unit, and comprising an imperforate vertical segmented partition consisting of alternate graphite spacers and parallel graphite plates disposed transversely to the plane of the partition and projecting to one side thereof; an opposed cathode structure secured in said frame composed of a vertical flat metal screen having secured thereto on one face thereof a plurality of spaced parallel closed hollow screen fins disposed transversely to the screen and entering the spaces between the graphite plates projecting from the anode partition; and a permeable diaphragm covering said cathode structure; flexible metal electrical contactors connecting the rear face of the anode structure R in each unit cell to the rear face of the cathode structure in the adjacent unit by direct physical and projecting to one side thereof; an opposed cathode structure removably secured wholly within said frame and comprising a vertical flat metal screen having removably secured thereto on oneface thereof a plurality of spaced parallel closed hollow fins of the same screen material disposed transversely to the screen and entering the spaces between the graphite plates project ing from the aforesaid anode partition; and a permeable diaphragm covering said cathode structure; flexible metal electrical contactors wholly within the assembled cell frames connecting the rear face of the anode structure in each unit cell frame to the rear face of the cathode structure in the adjacent cell frameby direct physical contact; and terminals connecting the end unit cells wlth a source of current.

7. An electrolytic cell series of the bipolar elec-' trode filter-press typecomprising a plurality of abutting unit cells, each unit including in combination: a frame of non-conducting material; an anode structure rigidly secured wholly within the frame and functioning also as the sole partition between the unit cell and the adjacent unit and being composed of an imperforate vertical graphite partition having a plurality of spaced parallel graphite members disposed transversely to and projecting from one face of said partition and a plurality of flexible metal electrical connectors secured to the opposite face thereof; an opposed cathode structure removably secured wholly within the same frame and comprising a vertical flat metal screen having removably secured thereto on one face thereof a plurality of spaced parallel closed hollow tins of the same screen material disposed-transversely to the screen and entering the spaces between the graphite members projecting from the anode partition, and having flexible metal electrical connectors secured to the opposite face of said screen and in direct physical contact with the electrical connectors secured to the anode structure of the adjacent unit cell; a permeable diaphragm covering said cathode structure; and terminals connecting the end unit cells with a source of current. v

8. An electrolytic cell series of the bipolar electrode filter-press type comprising a plurality of abutting unit cells, each unit comprising in comaaeaoua bination: a frame of non-conducting material; an anode structure secured wholly within the frame and functioning also as the sole partition between the unit cell and the adjacent unit and comprised of an imperforate vertical graphite partition having a plurality of spaced parallel graphite members disposed transversely to and projecting from one face of said partition; an opposed cathode structure removably secured wholly within the same frame and composed of a vertical flat metal screen having removably secured thereto on one face thereof a plurality of spaced parallel closed hollow flns of the same screen material disposed transversely to the screen and entering the spaces between the graphite members projecting from the anode partition; and a permeable diaphragm covering said cathode structure; flexible metal contactors wholly within the assembled cell frames electrically connecting the rear face of the anode structure in each unit cell to the rear face of the cathode structure in the-adjacent cell frame by direct physical contact; the space within a single unit cell frame between said anode and said connecting the end unit cells with a source oi current.

RALPH M. HUNTER. LAWRENCE B. OTIS. ROBERT D. BLUE.