US2424495A - Method for vaporizing sulfur - Google Patents

Description

July 22, 1947. J. w. NEELLEY 2,424,495

I METHOD FOR VAPORIZING SULFUR Filed April 12, 1945 INVENTOR. J54/us. 1401452245) ymw q Patented July 22, 1947 METHOD FOR VAPORIZING SULFUR Julius Worth Neelley, Front Royal, Va., assignor to General Chemical Company, New York, N. Y., a corporation of New York Application April 12, 1945, Serial No. 588,035

7 Claims.

This invention relates to methods for vaporizing sulfur.

vaporization of sulfur is effected by burning a portion of a body of molten sulfur to form sulfur dioxide, and utilizing heat thus generated to vaporize the balance of the sulfur. In commercial practice, most of the brimstone used in the industries concerned is vaporized in either of two general types of Vaporizers, a rotary furnace or a stationary vaporizer built of suitable steel and brickwork. Since the rotary furnace is usually operated under negative pressure, feed of pulverized solid brimstone directly into the furnace, e. g. by a screw conveyor, presents no particular difficulty. However, the stationary type vaporizer is ordinarily employed in systems in which for some reason it is desired to effect vaporization of the sulfur under pressure. Heretofore, there have been developed no procedures by which it has been feasible, when operating on a large commercial scale, to satisfactorily feed solid brimstone directly into the vaporizing chamber of a pressure type vaporizer. Accordingly, it has been customary to first melt the sulfur and then introduce the molter sulfur into the vaporizing chamber. This practice requires a separate sulfur melter and associated pipe lines and valves which often become clogged. Usually, extraneous heat such as steam is employed to effect liquefaction of brimstone in the melter.

This invention relates to improvements in the feeding of brimstone particularly to the type of vaporizer operated under more or less positive pressure. A primary object of the invention lies in provision of procedure by practice of which it is conveniently possible to feed solid brimstone directly to a vaporizer chamber which may be operating under positive pressure, and to effect feed of solid brimstone at a rate adequate to facilitate utilization of the vaporizer at its full rated capacity. Further objectives comprise accomplishment of the foregoing, along with utilization of heat present in the vaporizer to efiect melting of the brimstone, and elimination of extraneous sulfur melting equipment and its attendant installation and maintenance costs.

The nature of the invention and its advantages may be understood from the following description taken in connection with the accompanying drawing in which Fig. 1 illustrates in vertical crosssection one form of apparatus in which the improvements constituting the invention may be carried out.

The vaporizer comprises a suitable brick-lined shell l provided with a hopper bottom termi'naring in 3, cleanout drain Air to support the burningwaporizing reaction, e. g. as effected in Gillett U. S. P. 1,832,013 of November 17, 1931, may be introduced under pressure thru pipes |2 arranged so that their air distributors [3 project well below the normal operating level l4 of the pool of molten sulfur maintained in the bottom of the vaporizer. The vaporized sulfur-sulfur dioxide gas mixture formed in the vaporizing chamber gas space 5 is discharged thru a suitable outlet H to the point of use.

Set into the crown of the vaporizer is a cylindrical steel member 20 affording suitable gas-tight support for a sulfur feed conduit 2|. This conduit is designed as to length and diameter, relative to the size of the particular vaporizer, so as to provide a sulfur melting chamber 22 of substantial capacity, the overall length of the conduit and its vertical positioning in the vaporizer being such that the lower end of the conduit projects beneath molten sulfur level I so as to provide a gas seal which prevents ingress to the melting chamber 22 of gas from vaporizer gas space I 5. It will be noted that the major portion of conduit 2! lies within the gas space l5 and the pool of molten sulfur, with the result that the sulfur melting effected in the conduit is brought about by indirect transfer of heat from the gas space l5 and the molten sulfur pool.

Solid crushed brimstone may be fed from a hopper not shown thru feed pipe 25, provided with a control valve 26, into conduit 2|. Pipe 28 opening at one end into chamber 22 affords an ofitake for any gases and vapors collectin in the top of such chamber.

Problems encountered in feeding solid brimstone directly to a vaporizer of the type described may be understood from an appreciation of the results obtained when attempting to operate such a. vaporizer without utilizing the principles. constituting the present invention. For purpose of illustration it may be assumed that the vaporizer of the drawing is cylindrical in horizontal crosssection, has an inside diameter of about 10 feet, a vertical dimension from the crown to the cleanout drain ll of about 8 feet, and that the inside diameter of conduit 2| is about 2 feet. When operatin such a vaporizer under conditions in which solid brimstone charged in thru pipe 25 melted and passed relatively smoothly thru conduit 22 and into the pool of molten sulfur, the apparatus handled approximately 2750 pounds of sulfur per hour. Attempts to raise capacity of the unit by increasing the amount of brimstone fed into conduit 2| were unsuccessful, it being found that chamber 22 became clogged to such an extent as to prevent feed to the vaporizer of any greater quantities of brlrnstone.

In normal operation, temperature of the pool of molten sulfur in the bottom of the Vaporizer is about e o-650 F., and temperature in the gas space i5 is approximately 690-700 F. On the other hand, brimstone as fed thru valve 25 may be at temperature of say '75l00 F., i. e. well below the approximate 240 F. melting point of su1- fur. Thus it will be seen that during passage of the brimstone from the top to the bottom of the conduit 2|, sulfur is heated progressively, by indirect heat transfer from the vaporizing chamber, from temperature of about 75-100 F. to about (MO-650 F. This overall temperature range includes an intermediate temperature range of approximately SOD-450 F, within which range molten sulfur exists in a Very viscous and difificultly flowabl condition. Investigation showed that in the operation so far described, this state of high viscosity of molten sulfur probably existed throughout a substantial linear dimension of conduit 2|, and that the extent of the column of viscous sulfur was so great as to cause the molten sulfur to hang up in the feed conduit and prevent passage of the desired greater quantities of sulfur thru melting chamber 22 and into the sulfur pool.

According to this invention, it has been found that the foregoing difficulty may be overcome and the capacity of the unit greatly increased by agitating the molten sulfur in conduit 2|. While agitation may be effected in any desirable way, conveniently such agitation may be had by means of a suitable gas. Hence, there is provided adjacent the lower end of chamber 22 a gas distributor 35 which, as shown in Fig. 2, may be in the'form of a cross made of say 1 inch diameter pipe having aseries of side perforations indicated at 36. Such distributor may be placed within the lower end of the conduit 2|, in the plane of its lower end, or spaced somewhat beneath as shown in Fig. 1. The gas employed is supplied to the distributor from a pipe 40 having a pressure control valve 4|. Where agitation only is desired within melting chamber 22, any gas may be used, such as CO2 or nitrogen which is inert to the reactions as taking place in the vaporizer chamber proper and in the melting chamber 22.

To secure best results with respect to highcapacity per unit and smooth operation, it is preferred to agitate the molten sulfur in conduit 2| and additionally supply thereto heat which is supplemental to the heat indirectly transferred thru the walls of conduit 2| from the burningvaporizing reaction. Such combined agitation and supplemental heating may be accomplished by use of a gas containing free oxygen, such as air, which elfects generation in chamber 22 of supplemental heat by the burning of a relatively small amount of sulfur in the lower portion of chamber 22.

In obtaining the data given in the following table Column A Column B Column Distance from top of Tempera- Tempcra- Tem eracondult 21 m feet ture in F. ture in F. ture i3 F.

the vaporizer employed was approximately of the dimensions already stated and was equpiped with a feed conduit 2| having an overall length of about 7 feet and an inside diameter of about 2 feet. The temperatures given in columns A and B were taken at points about 8 inches from the vertical axis of the feed conduit, and the temperatures listed in column C were taken at the center of the conduit. The data of column A indicate temperature conditions existing during an average run when no extraneous gas was introduced into the bottom of the conduit. The temperatures stated in columns B and C were taken during an average run of the same apparatus modified only in that air was introduced into the bottom of conduit 2| thru the distributor 35 at a rate of approximately 25 cubic feet per minute NTP. The maximum input of brimstone to the vaporizer when operating under the conditions of column A was about 2750 pounds of sulfur per hour. However, when proceeding in accordance with the preferred embodiment of the invention and using air as the agitating medium, the capacity of the vaporizer was doubled and raised to about 5500 pounds per hour. It will be noted from column A that the approximate 300 450 F. high viscosity temperature range of molten sulfur existed thru a vertical dimension of about three feet. On the other hand, column B shows that a temperature range within which sulfur is viscous extended thru only about 9 inches. Similarly as shown by column C, the temperature range of high sulfur viscosity prevailed thru a vertical distance less than one foot. Column C also shows that the temperature range of high viscosity is a little lower down in the center of the conduit than nearer the circumference of the conduit, as in the case of the data in column B;

While introduction of air into conduit 2| as described affords the marked improvements shown, the exact chemical and physical reactions taking place in the conduit are not completely understood. Hence, although it is believed that the results obtained are attributable to a substantial reduction of the linear dimension of the zone constituted by'the temperature range within lar apparatus at hand, and optimum rates of gas supply to conduit 2| may be determined by test runs. In circumstances in which the presence of appreciable amounts of S02 in vent 28 are undesirable, e. g. where any substantial quantity of S02 in vent 28 may not be economically disposed of, inert gases such as CO2 and nitrogen may be utilized to advantage. In some particular operations it may be necessary, in order to obtain comparable results, to introduce greater quantities of CO2 or nitrogen than would be the case if a gas containing free oxygen were utilized. However, in one instance of operation of the vaporizer above described, good results as to vaporizer capacity were obtained when CO2 gas was introduced into conduit 2| at a rate as low as 14 cubic feet per minute NTP.

In practice of the invention, molten sulfur in conduit 2| may be maintained easily at the level of dotted line 38. Thi makes it possible to feed the solid brimstone from pipe 25 directly into molten sulfur which affords the advantage of preventing the presence, in the top of conduit 2| and in pipe 25, of explosive mixtures of sulfur dust, sublimed sulfur and air.

I claim:

1. The method for burning-vaporizing sulfur by a procedure in which sulfur is fed in solid form to a burning-vaporizing zone thru a sulfur feed conduit which method comprises maintaining a pool of molten sulfur in a burning-vaporizing zone having a gas space, supplying unmelted solid sulfur to said sulfur feed conduit projecting into said pool, a substantial portion of said conduit lying within said gas space and said pool, melting sulfur in said conduit, by indirect transfer of heat from said burning-vaporizing zone, to an extent at least sufficient to effect movement of sulfur thru said conduit and discharge molten sulfur to said pool, and passing thru the sulfur during movement of the same thru said conduit a gas, of the group consisting of inert gas and gas containing free oxygen, in quantity sufficient to substantially increase the rate of supply of molten sulfur to said pool.

2. The method for burning-vaporizing sulfur by a procedure in which sulfur is fed in solid form to a burning-vaporizing zone thru a sulfur feed conduit which method comprises maintaining a pool of molten sulfur in a burning-vaporizing zone having a gas space, supplying unmelted solid sulfur to said sulfur feed conduit projecting into said pool, a substantial portion of said conduit lying within said gas space and said pool, melting sulfur in said conduit, by indirect transfer of heat from said burning-vaporizing zone, to an extent at least suficient to effect movement of sulfur thru said conduit and discharge molten sulfur to said pool, and agitating the sulfur during movement of the same thru said conduit sufficiently to substantially increase the rate of supply of molten sulfur to said pool.

3. The method for burning-vaporizing sulfur under pressure by a procedure in which sulfur is fed in solid form to a burning-vaporizing zone thru a sulfur feed conduit which method oomprises maintaining a pool of molten sulfur in a burning-vaporizing zone having a gas space, supplying unmelted solid sulfur to said sulfur feed conduit projecting into said pool, a substantial portion of said conduit lying within said gas space and said pool, melting sulfur in said conduit, by indirect transfer of heat from said burningvaporizing zone, to an extent at least sufficient to effect movement of sulfur thru said conduit and discharge molten sulfur to said pool, and passing air thru the sulfur during movement of "the same thru said conduit, the quantity of air being such as to agitate and increase the temperature of the sulfur in said conduit sufficiently to substantially increase the rate of supply of molten sulfur to said pool.

4. The method for burning-vaporizing sulfur by a procedure in which sulfur is fed in solid form to a burning-vaporizing zone thru a sulfur feed conduit which method comprises maintaining a pool of molten sulfur in a burning-vaporizing zone having a gas space, supplying unmelted solid sulfur to said sulfur feed conduit projecting into said pool, melting sulfur in said conduit to an extent at least sufficient to effect movement of sulfur thru said conduit and discharge molten sulfur to said pool, and passing thru the sulfur during movement of the same thru said conduit a gas, of the group consisting of inert gas and gas containing free oxygen, in quantity sufficient to substantially increase the rate of supply of molten sulfur to said pool.

5. The method for burning-vaporizing sulfur by a procedure in which sulfur is fed in solid form to a burning-vaporizing zone thru a sulfur feed conduit which method comprises maintaining a pool of molten sulfur in a burning-vaporizing zone having a gas space, supplying unmelted solid sulfur to said sulfur feed conduit projecting into said pool, a substantial portion of said conduit lying within said gas space and said pool, heating the sulfur progressively while passing thru said conduit, by indirect transfer of heat from said burning-vaporizing zone from a temperature below to a temperature above the temperature range within which molten sulfur exists in the viscous condition, whereby there is formed in said conduit a zone of viscous sulfur and whereby molten sulfur is fed to said pool, and passing thru the sulfur during movement of the same thru said conduit a gas, of the group consisting of inert gas and gas containing free oxygen, in quantity sufilcient to decrease the extent of said viscous zone and thereby substantially increase the rate of supply of molten sulfur to said pool.

6. The method for burning-vaporizing sulfur under pressure by a procedure in which sulfur is fed in solid form to a burning-vaporizing zone thru a sulfur feed conduit which method comprises maintaining a pool of molten sulfur in a burning-vaporizing zone having a gas space, supplying unmelted solid sulfur to said sulfur feed conduit projecting into said pool, a substantial portion of said conduit lying Within said gas space and said pool, heating the sulfur progressively while passing thru said conduit, by indirect transfer of heat from said burning-vaporizing zone, from a temperature below to a temperature above the temperature range within which molten sulfur exists in the viscous condition, whereby there is formed in said conduit a zone of viscous sulfur and whereby molten sulfur is fed to said pool, and passing air thru said sulfur during movement of the same thru said conduit, the quantity of air being sufficient to decrease the extent of said viscous zone and thereby substantially increase the rate of supply of molten sulfur to said pool.

'7. The method for burning-vaporizing sulfur under pressure by a procedure in which sulfur is fed by gravity in solid form to a burning-vaporizing zone thru a sulfur feed conduit which method comprises maintaining a pool of molten sulfur in a burning-vaporizing zone having a gas space, supplying unmelted solid sulfur to said sulfur feed conduit projecting into said pool, a substantial portion of said conduit lying Within said gas space and said pool, heating the sulfur progressively while passing thru said conduit, by indirect transfer of heat from said burningvaporizing zone, from a temperature below to a temperature above the temperature range within which molten sulfur exists in the viscous condition, whereby there is formed in said conduit a zone of viscous sulfur and whereby molten sulfur is fed to said pool, and passing air thru said sulfur during movement of the same thru said conduit, the quantity of air being sufficient to agitate and increase the temperature of the sulfur in said conduit and thereby reduce the extent of said viscous zone and substantially increase the rate of supply of molten sulfur to said pool.

JULIUS WORTH NEELLEY.

REFERENCES CITED The following references are of record in the file of thispatent:

UNITED STATES PATENTS Number Name Date 1,409,338 Fenton Mar. 14, 1922. 1,832,013 Gillett Nov. 17, 1931 1,476,523 Kerr Dec. 4, 1923

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