US2305209A

US2305209A - Method and apparatus for solidifying molten sulphur

Info

Publication number: US2305209A
Application number: US363672A
Authority: US
Inventors: Herbert E Treichler; Harry A Swem; James W Schwab
Original assignee: Texas Gulf Sulphur Co
Current assignee: Texas Gulf Sulphur Co
Priority date: 1940-10-31
Filing date: 1940-10-31
Publication date: 1942-12-15
Anticipated expiration: 1959-12-15

Description

" i5 E942. H. E. .TRExcHLER ETAL mg METHOD AND APPARATUS FOR SOLIDIFYINQ MOLTEN SULPHUR Filed Oct. 3l, 1940 2 Sheets-Sheetl INVENTORS ATTO R N EYS 51, @2 H. E. TRElcHLER x-:TAL 2,305,209

METHOD AND APPARATUS FOR SOLIDIFYING MOLTEN SULPH'UB 2 sheets-sheet 2 1 INVENTORSY /S/efer f ezb/er Filed Oct. 3l, 1940 BY 72ml, UM, www fm ATTORNEYS A Patented Dec. l5, 1942 UNITED STATE METHOD AND APPARATUS FOR SOLIDIFY- ING MOLTEN SULPHUR Herbert E. Treiehler, Harry A. Swem, and James W. Schwab, Newgulf, Tex., assignors to Texas Gulf Sulphur Company,

poration of Texas Houston, Tex., a cor- Appllcation October 31, 1940, Serial No. 363,672

6 Claims.

This invention relates to the solidification of proved method of and apparatus for the rapid solidification of molten sulphur in the form of relatively small castings. The invention particularly contemplates the provision of an improved method' of solidifying molten sulphur in which the sulphur solidifles so rapidly that a l considerable portion of the solid sulphur is in the amorphous state. The molten sulphur is advantageously cooled in the form of narrow strips in which only a relatively small surface thereof is in contact with aV supporting surface upon which the sulphur solidifies. In accordance with the invention the molten sulphur is poured in one or more smallstreams over a supporting surface in a plurality ,of overlying layers, one layer being cooled to non-flowing consistency, for example to a more or less solid state, before the next layer is applied.

Sulphur mined by the Frasch process is in a liquid state and must be solidified for shipment. While many proposals have been made for the rapid solidiflcation of sulphur in small solid bodies, none has been successful and the present practice involves cooling the sulphur in bins or vats. The vats are usually of such size that it takes many months to fill and cool them and as a result the interval between mining and shipping is often a year or longer. Sulphur is a poor conductor of heat and in large bodies it cools so slowly that it contains only a tr'ace of amorphous sulphur. The sulphur is accordingly in a friable state and not in a state which can be broken into lumps without an appreciable loss in fines. The casting of sulphur in smallmolds, where the cooling is rapid enough to form a considerable proportion of the amorphous modification, has not been a success because the shrinkage is small and the sulphur sticks to the mold. As the size of the casting is increased, the tendency to stick to the mold surfaces is more and more offset by the increased effect of shrinkage. But while the larger castings overcome some of the tendency for sulphur to stick to the mold, the freezing is so slowthat the amorphous sulphur forms in decreasing proportions as the size of the castings increase. The larger castings accordingly lack the desirable tough dense structure of rapidly cooled sulphur.

molten sulphur and has fo'r its object an im- 'I'his invention contemplates the provision of an improved method of and apparatus for overcoming the aforementioned dimculties and aims to solidify molten sulphur sufficiently rapidly to give it such a dense structure that it is strong enough to utilize the contraction dueto cooling to free itself from the medium on which it is solidified. We have found that when molten sulphur is applied in a number of overlapping layers on a supporting surface in the form of 'elongated narrow bodies or strips with accompanying cooling, that a larger part of the sulphur solidies to the amorphous state, and also that the shrinkage in the longitudinal direction of the strips aids in freeing the solid sulphur from the surface. We may use any suitable surface that will support or contact the sulphur on one side, and we provide relative motion between the surface and the stream of sulphur so that the sulphur will be spread over the surface in a plurality of superposed layers. We have found that a suitable supporting surface is advantageously in the form of a large wheel or rotatable cylinder. The molten sulphur is preferably poured -out of one or more stationary spouts in thin narrow streams onto the rotating exterior surface of the cylinder. The rate of speed of the surface and the rate of ow of sulphur are so controlled, together with the conditions of cooling, that a plurality of overlying layers of sulphur are built up in the form of long strips on the supporting cylindrical surface. The sulphur is preferably poured onto the cylinder near the top thereof and the conditions are so controlled that by the time the sulphur reaches the under portions of the cylinder it has reached non-flowing consistency and, generally, has solidified. 'I'he sulphur on the cylinder is cooled as quickly as practically possible and means are preferably provided to charge. a heat-absorbing fluid, such as steam or atomized water, in contact with the sulphur on the cylinder and also to cool the cylinder itself, preferably on the inside. As the cylinder continues to rotate and the sulphur to be deposited on the exterior surface, one layer or film over another, long circular strips which are approximately rectangular or square in cross section are built up on the supporting surface. On cooling, there is a considerable shrinkage in the longitudinal direction of the strips which cracks them in sections and an internal force causes themA to try to straighten out so that they fall from the cylinder.

The apparatus of the invention comprises means for passing one or more streams of molten sulphur onto a moving surface, advantageously a rotating cylindrical surface, and means for directing a cooling fluid in contact with the sulphur to increase the rate of cooling.

These and other novel features of the invenbe better understood after considering discussion taken in conjunction ,o7 panying' drawings, in which: .nde view ci apparatus embodying the invention;

Fig. is iront end view of the apparatus of Fig. 3 is an enlarged view of a fluid distributor; Fig. Ll i. plan `riew of a, sulphur feeder; Fig. 5 i side view of the feeder of Fig. 4; and Fig. 6 i an end View of the feeder of Fig. 4. The apA aratus illustrated in the drawings is especially eficacious in a practice of the invention and comprises av Wheel or cylinder l having an exterior supporting surface 2 for solidifying the sulphur strips 3. The surface 2 is made of any. suitable thin gage sheet metal which will radiate Iand is resistant to the action of sulphur and does not form black sulphldes, such as galvanized steel, aluminum or stainless steel. The cylinder is rotatably driven n the shaft d by the variable speed motor 5.

:u ratus :for pouring a plurality of uniof molten sulphur over the ace compris a steam jacketed sulphur rank iti, a valve controlled pipe Il for assrig sulphur into the feeder l2 which has an cljustab e weir it for maintaining a uniform level ci sulphur, a steam jacket ld and a plurality spaced spouts iti for pouring the sulphur onto 'The barile it aids in distributing sulpand the excess oi sulphur flows over through the spoutl il and into the ow tank it? from which it is pumped back into the storage tank through the pipe system I9. The strips of sulphur may be cooled indirectly by cooling the inside of the cylinder or directly by charging a heat-absorbing iluid thereover. This may be done with cold air, if the velocity is such that liquid sulphur is not blown from the euri steam and comprises a steam f. ply-ing steam to a plurality of circumferentially spaced steam jets 2l arranged to discharge the steam into housings 22. One row of cooling devices is provided for cooling the l i... scp

strip ci sulphur issuing from each of the spouts The valve il is ado permit enough sulphur to enter the i to keep it filled to the proper level. ,ss oye iows the weir it and enters the t from which it is pumped back into the tenir iii and a constant uniform flow of sulphur is discharged in uniform thin streams from the spouts i5. As the cylinder i rotates, narrow iilms of sulphur are deposited around "le surface As the cylinder rotates, heat is issipated from the sulphur as quickly as possible. While it is possible to adjust conditions so to rely wholly on air cooling to solidify the films of sulphur, we prefer to accelerate cooling by the use of steam as just described.

As the cylinder rotates steam is charged out of the jets 2| into the housing 22 Where it expands forming a mist which passes into contact with the sulphur strips. The cylinder is rotated `at such a speed and the sulphur is applied at such a rate that with each' rotation the lms of liquid sulphur, which are applied near the top of the cylinder, freeze as the cylinder turns downward andare solid enough when they reach the bottom so that no liquid drips from the strips. As the cylinder rotates to a position where the layer of sulphur is about to be covered with another layer, the sulphur in the last completed layer has practically or completely solidified. The continued rotation piles one layer over another. In this manner the strips aregradually built up to form long circular castings, approximately rectangular or square in section, and supported by only one face.

When strips of the desired thickness have been built up, the now of liquid sulphur is stopped and the strips are allowed to cool. Usually only a very few minutes are required for the sulphur to cool sufficiently to cause enough shrinkage in the circular castings so that, when broken, the strips separate readily from the supporting surface and fall from the wheel as it rotates.

Forces which are set up in the cooling of a long circular sulphur casting of this kind and which tend to separate it from the supporting surface, are apparent, from watching the manner in which the casting frees itself from the metal surface as it cools. The casting first ruptures through its small section, then seems to straighten out as it is thrown tangentially from the cylinder. The greatest shrinkage force is obviously in the long dimension of the casting. This force contracts the casting and brings about rupture and decreased overall length. But in addition to this overall circumferential shrinkage, which makes the casting shorter, there is a slightly greater shrinkage in the longer top portion of the casting than in the shorter bottom portion which is in contact with the cylinder. This greater shinkage in the top portion tends to increase the radius of the casting after it has ruptured, and, particularly with thicker sections, seems to assistmaterially in completely separating it from the sulpporting surface. i

In those casting methods in which small molds are used any sulphur which sticks to the mold after the casting is removed must be scraped from it before another casting is poured, for if it is left on the mold it serves to anchor the next casting rmiy to it. In this method any bits of sulphur which may remain on the surface partially fuse into the next strips and are broken from the surface with them. It is not necessary to clean or bui sulphur from the supporting surface.

The application of steam to the cylinder has the additional advantage of keeping the surface moist. A moist surface is desirable when the castings are started as the lm of moisture on the surface causes the rst layer of sulphur applied to freeze so rapidly that most of it is separated for a time from the surface by a nlm of moisture. This procedure materially reduces the amount of shrinkage required to separate the castings from the surface and makes possible a shorter cooling period after the castings are completed. The operation is more efectife when the supporting surface is a true cylinder and when it moves at a uniform rate of speed with no back-lash to break the uniform forward motion.

The rate at which sulphur can be applied varies with the temperature of -the liquid sulphur, the nal cross sectional area of the sulphur castings desired, the diameter of the cylinder, the rate of rotation thereof, and the auxiliary means used to assist in cooling the sulphur. These variables can readily be adjusted experimentally for any particular installation. In one operation we used a cylinder feet in diameter, 3 feet wide, rotated at a peripheral speed of 3.1 feet per second. YNine strips of sulphur were cast at one time', each ll/2 inches thick and'l inch wide from molten sulphur at 247 F. During 23 minutes the cylinder rotated 136 times and 350 pounds of sulphur were cast. In another operation using a similar cylinder which rotated 126 times in 25.5 minutes, three strips were cast at one time, each 1% inches thick and 1% inches wide, from sulphur at 240 F. to produce 156 pounds of castings.

The friability of the castings may be controlled by the methods used to cool the sulphur after it is broken from the wheel. If very tough sulphur is desired the castings are spread out and cooled as quickly as possible so as not to appreciably reduce amorphous sulphur in the product and, as friability varies more or less inversely with the percentage of amorphous sulphur. the degree of friability of the product. The most frlable sulphur produced in this manner does not, however, form as great a porportion of fines as vat sulphursbecause of its uniformly dense non-porous structure.

We claim: 1. A method of solidifying molten sulphur which comprises applying a layer of molten sulphur over a supporting convex rigid surface, cooling the layer to non-ilowing consistency, applying one or more other layers of molten sulphur over the first-mentioned layer and cooling each layer before the next layer isapplied, thereby building up a body of solid sulphur of such size that it is subjected to considerable contraction, and permitting the solid body of sulphur to contract and free itself from the supporting surface. f

2. A method of solidifying molten sulphur which comprises applying a plurality of superposed spaced narrow layers of molten sulphur over a supporting rigid surface and building up long narrow strips of sulphur, cooling each layer of sulphur before applying the next layer, solidifying the stn'ps of sulphur, and permitting the strips to contract and separate from the supporting surface.

3. A method of solidifying molten sulphur which comprises pouring at the same time a plurality of separate narrow streams of molten sulphur over the exterior surface of a rotating rigid cylinder to form a plurality of separate layers of sulphur, said streams of sulphur being sufficiently spaced that the adjacent layers do not flow together, cooling the layers of sulphur sufilclently before the cylinder has completed one revolution that the sulphur does not ilow, continuing to rotate the cylinder to apply one or more similar layers of sulphur over the aforementioned separate layers to build up a plurality of narrow strips of solid sulphur of the desired thickness, interrupting the pouring of molten. sulphur and permitting the strips of sulphur to contract and free themselves from the cylinder.

4. Apparatus for thesolidication of molten sulphur which comprises a. rotatable cylinder, means for pouring a plurality of spaced thin streams of molten sulphur on the exterior surface of the cylinder at the same time, said cylin der being arranged to rotate a plurality of revolutions to deposit a plurality of superposed layers of sulphur one over the other, means for cooling each layer of sulphur, and valve means for interrupting the pouring of molten 'sulphur to permit the sulphur on the cylinder to cool and contract suiliciently to free itself from the cylinder..

5. Apparatus for the solidiflcation of moltensulphur which comprises means for pouring a plurality of thin spaced streams of molten sulphur out of a body of molten sulphur, a supporting surface upon which the sulphur of each stream is deposited in a plurality of superposed layers, means for moying the surface relative to the pouring means, said streams being such distances apart that the sulphur builds up in the form of long narrow strips which are spaced from each other, means for cooling the layers of sulphur. and means for cooling the strips of sulphur after the last layer has been applic to permit the sulphur to contract and'separate rom the supporting surface.

6. Apparatus according claim 5-in which the supporting surfaceis curved and thestrips of sulphur are built up on the convex surface.

HERBERT E. 'IIREICHIER HARRY A. sWEM.

SCHWAB.