US2944955A

US2944955A - Purification device for alkali metal cells

Info

Publication number: US2944955A
Application number: US802346A
Authority: US
Inventors: Arthur L Fentress
Original assignee: Ethyl Corp
Current assignee: Ethyl Corp
Priority date: 1959-03-27
Filing date: 1959-03-27
Publication date: 1960-07-12
Anticipated expiration: 1977-07-12

Description

l mqkQ July 12, 1960 A. L. FENTRESS I llllllll ll TTT-TTTTT T nited States Patent PURIFICATION DEVICE FOR ALKALI METALj CELLS Arthur L. Fentress, Baton Rouge, I.a., assignor to Ethyl Corporation, New York, N.Y.,' a corporation of Delaware Filed Mar. 27, 1959, SertNo. 802,346 2 Claims. c1. 2 04-245) drical steel cathode. Within the annular'portion formed between the anode and cathode. isusually inserted a foraminous metal-diaphragm. During electrolysis the chlor'ine' is evolved from the anode and-is removed from the upper portion of the cell through a' gas dome situated above the anode. The alkali metal, or sodium, which is separated from the salt, is displaced to the upper portion of the cell and is manifolded within an annular collecting chamber and removed through a vertical take-off line or riser. pipe communicating with the cell exterior. V Because of the high temperature requiredto melt alkali metal salts, particularly sodium chloride, it is customary to add a secondsalt thereto to lower its melting point. Generally, a fused mixture of calcium chloride and sodium chloride is employed for the manufacture of sodium. This inevitably results in the problem of removing the calcium metal from the sodium metal. The. preponderance of the calcium metal is normally removed by passing the sodium metal upward through the cool riser pipe prior to discharge. The sodium metal solution gradually cools'iduringits upward ascent thereby producing precipitation of the low solubility calcium metal. Most of the calcium metal precipitated falls or is returned to the bottom of the electrolytic cell where it dissolves. Inevitably, however; some calcium metal tends to deposit on the inner wall of the riser pipe. If such deposits were not removed,'they would eventually cause the complete pluggage of the riser pipe. It is therefore essential that these deposits be removed. customarily therefore, tickler devices'are used to dislodge the calciumdeposits. Automatically. driven tickler devices are described, for example, in US. Patents 2,770,364, 2,770,592, and 2,861,- 938. '[hese devices usually comprise a cleaner assembly operatively connected to a drive mechanism. The cleaner assembly usually consists of a plurality of cleaner blades or scrapers mounted so as to act upon the inner walls of the riser pipe, over its entire length, and to dislodge forming, or already formed, calcium deposits. Generally, the blades or scrapers are aflixed to a shaft whose axis corresponds to the center of the riser pipe and extends through the pipe from above and is capable of rotation and limited vertical movement. Various drive mechanisms have been proposed for these devices.

In all such devices, however, there is a common tendency for the devices'to function for a period and then to fail. After the tickler fails, or ceases to function, a newcleaner assembly must be inserted into the operating oell. The duration of time within which a tickler will continue to properly function before it must be removed from the cell is referred to-as= tickler life. Tlckler life 10 ings in money and operating labor.

ice

for present commercial ticklers is of extremely short duration. When an automatic tickler fails to function it is essential that the tickler be fairly promptly placed back in operation to prevent a complete pluggage of the riser 5 pipe. To remove the pluggage it must be chipped away by hand and a new cleaner assembly placed in the operating cell. Since a single cell installation contains a large number of cells it is apparent that this is a quite costly operation. Extension of tickler life means large sav- Obviously then, extension of tickler life is a very desirable goal.

Accordingly, it is an object of the present invention to provide a new and improved automatic tickler or cleaning assembly capable of operation for extended periods Without functional failures. It is also an object of the present invention to provide a new and improved tickler which will greatly decrease operating cost. A further object is to provide apparatus for the most effective cleaning of the riser pipe walls than has heretofore been possible; A more specific object of a highly preferred embodiment is to provide mechanism capable of exerting a variable cleaning action automatically correlated with the degree of adhesion of fouling deposits. The details of the apparatus and of preferred embodiments will be more readily understood from the following description and by reference to the accompanying Figures 1-3, wherein? Figure l is a generalized elevation illustrating the relation' of the assembly of the present invention to the fused salt electrolysis cell for which it is intended,

Figure 2 is an elevation, in partial cross section and on a larger scale, of the cell riserpipe having the apparatus of the invention and operating means incorporated therein,

and

Figure 3 is cross section AA showing the cleaner blades in greater detail. This figure also illustrates the preferred embodiment of the invention, as hereinafter defined.

These figures will be better understood from .the following description.

40 The apparatus comprises generally the combination, with a cell riser pipe, of an automatic tickler assembly which includes a cleaner device extending into the said vertical riser pipe, and having motor means operatively connected therewith for imparting vertical reciprocation 5 and rotational motion of the said device within the riser pipe. The present invention provides an improved cleaner consisting of an elongated member or central shaft, of length approximately equal that of the riser pipe, with a plurality of arms mounted on the said member which project at substantially right angles therefrom and are spaced along the said member. Upon the extremities of the arms are afiixed arcuate cleaner blades. The leading edges, or the edges in the direction of movement, are beveled. Each of the blades are adjacent and arced to correspond to the curvature of the inner wall of the riser pipe. The summation of the vertical dimensions of the said blades is substantially equal to the vertical dimension of the riser pipe such that upon rotation of the cleaner device the entire inner surface area of the riser pipe is 00 swept clean.

A more highly refined embodiment, described more mully hereinafter, provides arms which are slightly flexible at operating temperature. Thus when the blades, when moved in either a vertical or horizontal direction,

come into contact with a nonreadily severable formation the position of the leading or cutting edge relative to the formation acted upon is not permitted to yield or ride over the formation. Instead the position of the cutting edge is preserved and force is brought to bear upon the formation. In all embodiments a slicing action is i brought to bear upon the formation because of the simui- Patented July 12, 1960- taneous rotation and vertical motion of the elongated member.

The features and advantages will be better understood from the following detailed description of the invention and of its preferred embodiment. v

The general disposition of the apparatus of the present invention and .a sodium cell is illustrated by Figure l as above mentioned. Referring to Figure 1, the principal components of a cell include a cell body 11 comprisingan external steel shell lined with refractory brick orlining. A centrallymoun-ted carbon anode 12 is surrounded by a cylindrical cathode 13, having lugs 14 projecting through the cell walls and providing for connectionjto bus bars 15 supplying the electric current. Similarly the current is fed to the anode 12 by an anode bus bar 1 6. A dome and collector assembly 17 is mounted centrally above the anode-cathode electrodes and includes a chlo rine dome 18 in the form of an inverted generally conical member and a sodium collecting conduit 19. 'The chlorine dome terminates in a chlorine discharge line; 20 to transfer the gaseous chlorine to subsequent operations. The sodium collecting conduit 18 meets and is connected to the rise pipe 21. The riser pipe, here shown only in external view, is an elongated steel tubeprovided with fins 22 on at least a portion of the external portion. Surmounting the riser pipe is the guiding and. actuating. as.- sembly discussed and describedin detail hereafter. The fins 22 on the exterior portion of the riser pipe improve the dissiptation of heat from the interior of the pipe and its contents. Sodium discharge from the cell is d-ischarged through a connecting line 25 from the riser pipe andfeeds a receiving box 26 which is a container for tern porary holdup of the sodium, the sodium being then passed through a discharge spout 27 to a transfer vessel or container. I

In operation, the cell contains, up to a level approximately intermediate the full vertical elevation of the chlorine dome 18, fused electrolyte chlorides or a bath 31. This molten bath includes not only sodium chloride but appreciable quantities of calcium chloride. dium and chlorine as released in the annular space he tween the anode 12 and cathode 13 and rise on opposite sides of a diaphragm 32. The sodium collects in the channel 19 and flows to the entrance of the riser pipe 21.

It then rises in the riser pipe 21 and is discharged through line 25 to the receiver 26 and thence through the nozzleto a transfer container, not shown. The heat lossfrom the riser pipe through the fins 22 results in precipitation of calcium at and on the interior wall of the riser pipe 21.

The details of construction and operation of the improved tickler will be more readily understood by reference to Figure 2. This is an elevation on larger scale than Figure l and is also a partial section showing the relation of an automatic tickler, particularly the cleaner device, with the riser pipe 21. The driving mechanism can be one of several kinds. It can be: a pneumatic piston-cylinder combustion or an electrically driven device for example. A preferred pneumatic actuated device is fully described in US. Patent 2,770,364. The cleaner device includes a central shaft or elongated member 41 upon which is mounted a plurality of arms 42 projecting outwardly at substantially right angles therefrom. The

arms 42 preferably project outwardly from the shaft 41 so as to be in one vertical plane, each arm 42 being alternatively placed on opposite sides of the shaft 41 and 180 apart, and support cutter blades 43 as hereinafter defined. It will be understood however that other ar rangements of the arms are possible, subject to the condition that the width of the arcuate blades 43, spacing, etc. are such as to define contiguous cutting paths upon the riser pipe walls in conformity with the frequency of reciprocation and rotation of the assembly. Afiixed to the extremities: of thesev arms 42. are arcuate cleaner bledesa43'. The; blades 43: have beveled"v edges 63. at leastv The so in the direction of movement, and beveled so that the sharper edge is inclined toward the adjacent riser pipe wall. The blades 43 are arced to correspond to the curvature of the inner wall of the riser pipe 21 and the lengths of the arms 42 are such as to place each of the blades 43 adjacent the inner walls of the riser pipe 21. Generally a clearance of about 0.125 inch is allowed between the cutter blades 43 and the riser pipe inner wall. The arcuate blades 43 are usually made from rectangular members having a lengthzwidth ratio of from about 1:1 to about 3:1. The thickness of the blades 43 is usually from about 0.125 inch to about 0.75 inch. The cutting edges 63 of the blades 43 are preferably beveled to define an angle of from about 30 to about 45, the angle being that angle formed between a line extended perpendicularly from the shaft 41 to the apex of a cutting edge 63 and the face of that edge 63. Generally,

also, it is essential. that the blades 43 be spaced apart at such intervals that rotation of the shaft '41 causes the blades 43 to define contiguous "paths along the inner su'r-' face of the riser pipe 21; the summation of such paths being generally equal in vertical dimension to 'th'e v'er'tic'al dimensions of the inner surface of the riser pipe2'1. H

Figure 3 illustrates an even more highly refined and preferred embodiment wherein the arms 42 are designed to permit flexing thereof upon the blade 43 encountering a non-readily severable calcium metal formation. Thus, Figure 3 shows section AA taken from Figure 2. "The arms 42 and blades 43 are shown by solid lines in 'theif normal pos'ition of rotation, and 42 and 43 -111 a moment during rotation just after-the cutting edge 63; of the blade 43 has encountered an obstacle 70'. The broken" lines, though the anglefof deflection is highly exaggerated,

show the position which'the 42 and blade 43;; would normally occupy butffo r the obstruction 70', assuming.

that the normal position of the am 42 is spaced 180 from the arm 42 Thus, when the cutting edge 63;.

comes into contact with the obstacle 70 and fails to sever it from the inner wall of the riser pipe 21 the forward I 70. Further flexing of the arm 42. exerts force of the edge 63 upon theobstacle and tends to cause the edge 63 to dig deeper into the obstacle 70. Usually the force is suflici'ent' to dislodge the obstruction, after which time the arm 42 assumes its normal position.

As illustrative of the increased tickl'er life and im proved. 'efliciency of the apparatus in commercial" installations, in a typical sodium cell shop a battery of. the automatic tickle'rs herein described was placed in operation and carefully observed for an extended period of 63 days, while concurrently the remaining cells of the shop were operating with the conventional tickler. The results showed an 8.3 day average life for the tickler of the present invention and a 5.7 day average life for. the conventional tiekler. These results are highly significant, showing an improvement of greater than a 45 percent increase in tickler life.

Having fully described the apparatus of the invention, what is claimed. is: v

1. In a fused salt electrolysis cell, having a riser pipe extending above the cell for concurrently discharging sodium metal, for coolingand. precipitating the calcium.

impurity and returning same. to the cell, and having in.

combination with said riser pipe an automatic tickler assembly which includes a cleaner device extendinginto the vertical-riser pipe, and. motor means operatively connected therewith for imparting vertical reciprocationv and rotational motion of the cleaner device within said riser said member, and arcuate. cleaner." blades; having edges:

beveled. in: the. direction: of rotational motion and the edges inclined toward the riser pipe wall, afiixed to the extremities of said arms, said blades being adjacent to and arced to correspond generally to the curvature of the inner surface of the riser pipe, the summation of the vertical dimensions of said blades being substantially equal to the vertical dimension of the riser pipe whereby rotation of the cleaner cleans substantially the entire internal area of the riser pipe.

2. In a fused salt electrolysis cell, having a riser pipe extending above the cell for concurrently discharging sodium metal, for cooling and precipitating the calcium impurity and returning same to the cell, and having in combination with said riser pipe an automatic tickler assembly which includes a cleaner device extending into the vertical riser pipe, and motor means operatively connected therewith for imparting vertical reciprocation and rotational motion of the cleaner device within said riser pipe, the improved cleaner having an elongated member of length approximately equal that of the riser pipe, a plurality of arms mounted on said member projecting at substantially right angles therefrom and spaced along said member, and arcuate cleaner blades, having beveled edges in the direction of rotational motion and the edges inclined tw ward the riser pipe wall afiixed to the extremities of said arms, said blades being adjacent to and arced to correspond to the curvature of the inner surface of the riser pipe, the summation of the vertical dimensions of said blades being substantially equal to the vertical dimension of the riser pipe whereby rotation of the cleaner cleans substantially the entire inner area of the riser pipe, the said shafts upon which are mounted the cutter blades are sufliciently flexible at operating temperatures, both vertically and horizontally, that when the leading edge of a cutter blade encounters a non-readily sever-able forma- 7 tion, the said shaft yields but does not permit the posi- UNITED STATES PATENTS 20 2,390,115 McNitt Dec. 4, 1945 2,770,364 Honea Nov. 13, 1956 2,861,938 Glascodine .J Nov. 25, 1958

Claims

1. IN A FUSED SALT ELECTROLYSIS CELL, HAVING A RISER PIPE EXTENDING ABOVE THE CELL FOR CONCURRENTLY DISCHARGING SODIUM METAL, FOR COOLING AND PRECIPITATING THE CALCIUM IMPURITY AND RETURNING SAME TO THE CELL, AND HAVING IN COMBINATION WITH SAID RISER PIPE AN AUTOMATIC TICKLER ASSEMBLY WHICH INCLUDES A CLEANER DEVICE EXTENDING INTO THE VERTICAL RISER PIPE, AND MOTOR MEANS OPERATIVELY CONNECTED THEREWITH FOR IMPARTING VERTICAL RECIPROCATION AND ROTATIONAL MOTION OF THE CLEANER DEVICE WITHIN SAID RISER PIPE, THE IMPROVED CLEANER HAVING AN ELONGATED MEMBER OF LENGTH APPROXIMATELY EQUAL THAT OF THE RISER PIPE, A PLURALITY OF ARMS MOUNTED ON SAID MEMBER AND PROJECTING AT SUBSTANTIALLY RIGHT ANGLES THEREFROM AND SPACED ALONG SAID MEMBER, AND ARCUATE CLEANER BLADES HAVING EDGES BEVELED IN THE DIRECTION OF ROTATIONAL MOTION AND THE EDGES INCLINED TOWARD THE RISER PIPE WALL, AFFIXED TO THE EXTREMITIES OF SAID ARMS, SAID BLADES BEING ADJACENT TO AND ARCED TO CORRESPOND GENERALLY T O THE CURVATURE OF THE INNER SURFACE OF THE RISER PIPE, THE SUMMATION OF THE VERTICAL DIMENSIONS OF SAID BLADES BEING SUBSTANTIALLY EQUAL TO THE VERTICAL DIMENSION OF THE RISER PIPE WHEREBY ROTATION OF THE CLEANER CLEANS SUBSTANTIALLY THE ENTIRE INTERNAL AREA OF THE RISER PIPE.