CA1168422A - Sulfur-melter apparatus having sloping bottom and automatic shutoff therefor - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
SULFUR-MELTER APPARATUS HAVING SLOPING
BOTTOM AND AUTOMATIC SHUTOFF THEREFOR

An apparatus for melting powdered sulfur is disclosed. The apparatus comprises a covered hopper having a sloping expanded surface area bottom with a heating element directly thereunder and means for collecting and recovering the molten sulfur in communication therewith. The apparatus minimizes problems of sulfur bridging and is preferably portable. It finds preferred application supplying molten sulfur for the on-site preparation of concrete coatings, sealants and the like.
A device for automatically shutting off a sulfur melter when its supply of sulfur is exhausted or when sulfur bridging has occurred is also disclosed. The shutoff uses a temperature value sensed at the top of the melter's sloping melter bottom and shuts the heat off when the sensed temperature exceeds a preset value related to sulfur's melting temperature. The device avoids jamming and maintenance problems inherent in the use of mechanical level controls in a powdered/molten sulfur environment.

Description

SULFUR-MELTER APPARATUS HAVING SLOPING
BOTTOM AND AUTOMATIC SHUTOFF THEREFOR

BACKG~Ou~O ~ r~ luv~ o~

Field of the Invention This invention relates to an apparatus for melt-ing powdered sulfur and an automatic temperature shutoffcontrol therefor.
Background In a common child's chemistry experiment, pow-dered sulfur is placed in a metal spoon, heated over a flame and melted. So it would seem that the melting of powdered sulfur on a commercial industrial scale would be a simple business. In fact, however, it is made more difficult by the properties of the sulfur. When heated, sulfur not only begins to melt but also forms solid sulfur bridges which prevent the powder from reaching the heated surface and taking the place of molten sulfur as it is withdrawn. One solution to the problem of bridging has been to apply physical pressure to the sulfur powder with a piston so as to force the powder into contact with the heater surface. Such a device involves having moving parts in a hostile powdered/molten sulfur environment is not generally desirable because of maintenance and has not proven successful because of jamming and start-up diffi-culties. Another approach has been to apply extra heat to melt the bridge. This is frustrated by sulfur' 6 substan-tial flammability, energy inefficiencies the unacceptable release of sulfur vapors, and the low thermal conductivity of solid sulfur.
; U.S. Patent 4,171,200 discloses a process and apparatus for melting sulfur from massive solid storage blocks as are produced in refineries, gas treatment plants and the like. Such an apparatus serves a different pur-pose than does the present invention as it is fixed in place at the sulfur storage block to convert the solid block into a more-easily-transported molten form. The ~' present invention generally is embodied as a smaller portable unit such as would be useful for field application of molten sulfur-based coatings for concrete. The industry standard device as exemplified by United States Patent 4,171,200 employs electric heat or a fluid heat transfer medium. This is very suitable for a fixed unit but is ill-suited for a portable on the job unit which is to be used at nonelectrified sites. Moreover, a two-phase indirect heater with boilers and heat transfer fluid circulation system does not lend itself to the rapid start-up that is desired for mobile equipment and job site use.
_UMMARY OF THE INVENTION
The present invention seeks to eliminate or reduce the foregoing disadvantages by providing a simple fast-starting portable sulfur melter that minimizes the problems presented by sulfur bridging.
In accordance with the present invention there is provided a sulfur powder melting apparatus comprising covered sulfur-containing hopper means having a heat transmitting bottom sloped at an angle from 10 to 70 from horizontal, heating means located beneath said bottom to heat said bot-tom and melt sulfur in contact therewith, molten sulfur collecting means communicating with said bottom and located at the lower end of said bottom sloped at an angle of from 10 to 70 and molten sulfur discharge means exitin~ said molten sulfur connection means.

, 2 The heating element is located beneath the 05 sloping bottom. While electric, steam, hot oil or the like heating elements can be used in the subject melter, if desired, it is generally most efficient and economical to use combustion heating such as gas or oil burners.
These preferred heating elements offer the additional advantage of employing self-contained portable fuel sour-ces. The heating elements may be controlled manually or may be controlled by one or more theremostats monitoring the molten sulfur's temperature.
In addition, the present invention provides a control system which monitors the temperature of the sloping bottom and automatically shuts off or shuts down the heating element when a preset temperature is exceeded as would occur either if the powdered sulfur supply became exhausted or on those infre~uent occasions when large particles of sulfur managed to bridge the melter's sur-face. This control system is especially important because failure to promptly shut down the heat either when the sulfur load is exhausted or when sulfur bridging has occurred, can lead to overheating and fires.
As discussed above the present sulfur melter comprises a covered hopper for containing the sulfur and having a sloping extended surface bottom that is posi-tioned at an angle of from 10 to 70 from horizontal and a heating element located beneath the sloping bottom so as to apply sulfur-melting heat directly to the sloping bottom. The lower edge of the sloping bottom is adapted to collect the molten sulfur and communicates with means for removing the molten sulfur from the melter. The sloping bottom causes the molten sulfur to run downhill.
The present control system comprises locating temperature measuring means in the hopper at or about the sloping bottom's upper end, measuring the temperature at that location and, when that temperature exceeds a preset tem-perature related to the melting point of sulfur, as would occur either if the powdered sulfur supply becomes ~; exhausted or if the sulfur managed to substantially bridqe ~r the melter's bottom surface, automatically shutting off or O5 shutting down the heating element. Although any workable preset temperature may be employed, generally a preset shut-down temperature of about 300F or greater, up to a~out 375F, preferably about 315F to about 355F is employed. For reference, the melting point of sulfur is 252F such that the preset temperature is 48F to 123F
above it and preferably 63F to 103F above it.
The invention will be further described in the following Description of Preferred Embodiments which is to be read in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is an isometric view of a sulfur melter of this invention incorporating the shutoff system of the present invention;
FIG. 2 is an elevational cross-sectional view of one embodiment of the sloped bottom of a melter of this invention taken at line 2-2' in FIG. 1 and showing the placement of the heat sensor employed in the shutoff sys-tem of the present invention;
FIG. 3 is a cross-sectional plan view taken at line 3-3' in FIG. 2 of a sloped bottom of a melter of the invention;
FIG. 4 is a cross-sectional view taken at line 4-4' in FIG. 3 of the lower end of the sloped bottom of a melter of the invention; and FIG. 5 is an isometric view of an alternate sloping bottom for use in a melter of this invention.
- DESCRIPTION OF PREFERRED EMBODIMENTS
Referring to FIG. 1 a melter employing the pre-sent invention is shown. It includes a lower frame 11 which supports combustion box 12 which in turn engages and supports melter hopper 14. Hopper 14 includes sidewalls 15 and 16, front wall 17, back wall 19, and cover 20 to which is affixed, via hinge 21, cover door 22 through which powdered sulfur to be melted is added. Cover 20 also carries hopper vent pipe 23. The bottom of hopper 14 ~r ~G~

is defined by sloped planar bottom surface 24 which is 05 joined to walls 15, 16 and 19. The angle at which bottom section 24 meets sidewalls 15 and 16 is between about 10 and about 70 from horizontal, preferably between about 15 and about 60 from horizontal. Bottom 24 has an expanded surface provlded by a plurality of added ridges 25 affixed thereto parallel to the slope of hopper bottom 24. The front (lower) end of ridges 25 and bottom 24 do not contact front wall 17 but instead communicate with molten sul~ur collection trough 26. Trough 26 runs into and empties via discharge spout 27. A heating element, herein embodied as burner assembly 29, is located in com-bustion box 12 below bottom 24 so that in operation its output heats bottom 24 and ridges 25. Bottom 24, and any surface-expanding attachments thereto are fabricated of a heat-transmitting noninsulating material, preferably a

2~ metal such as steel or aluminum, so that heat from burner 29 is readily transmitted to the sulfur in contact there-with. As this embodiment is a portable one, it is suit-ably gas fired. Gas supplied from tank 30 is delivered through valve 31 and line 32 to burner assembly 29.
Burner assembly 29 is ignited by means not shown. The low sulfur level temperature sensor 33 is located in tube 34 positioned in hopper 14 at the top end of sloping bottom 24. The end of t~he tube 34 inside hopper 14 is sealed.
The other end extends out of hopper 14. Sensor 33, suit-~ 30 ably a thermocouple or the like is positioned inside 34 ; and is connec~ed via lead 35 to adjustable thermostat 36 which directs valve controller 37 to close valve 39 there-by shutting off burner 29 when the -temperature sensed by sensor 33 exceeds a preset value as occurs when the level 35 of sulfur in hopper 24 drops below tube 34. Flue 38 carries away products of combustion generated by burner 29.
Sulfur melted at the surface of bottom 24 of hopper 14 runs down sloped bottom 24 into trough 26 and 40 out through discharge spout 27. Trough 26 and spout 27 are heavy gauge metal so that heat from burner 29 conducts ~6~

to them and keeps them at a temperature above sulfur's melting point. Spout 27 discharges molten sulfur into lower mixing pot 40 that is surrounded by insulation or heater 41 ~or use in coating preparations. Other coating components such as fillers, resins, and the like are added to pot 40 as well and therein mixed with the molten sulfur using agitator 42 driven by motor 44 via drive shaft 45.
The resulting coating mixture is taken off through draw pipe 46 equipped with valve 47 and thereafter applied as required.
In FIG. 2 the sloping bottom area of a melter and the position of the temperature sensor of this invention is detailed. Melter hopper 14, enclosed by front wall 17, back wall 19 and sloping bottom 24 with ridges 25 is mounted over combustion box 12 vented by flue 38. Burner assembly 29 is mounted on box 12 and supplied gas via gas line 32. The flow of gas to burner 29 is regulated by tank valve 31 and low sulfur level shutoff valve 39 controlled by valve controller 37 in response to signals sent by thermostat 36 in turn in response to tem-peratures sensed by temperature sensor 33 located in sen-sor tube 34 positioned at the top end of the top surface of bottom plate 24. optionally a third valve 48 could be positioned in line 32 to control the temperature of the bulk molten sulfur by regulating the flow of gas based on temperature sensed by sensor 49 positioned in the melt area but somewhat away from bottom 24. Sulfur melted on bottom 24 runs down and passes through trough entrance 50 which very suitably contains holes 51 that permit molten sulfur to pass but generally restrict solid particles and hold them up on bottom 24 until they melt. The molten sulfur then enters trough 26 and exits via discharge spout 27, as previously described.
In FIG~ 3, the relationship and location of the surface-extending ridges 25 on bottom 24 of melter hopper 14 is shown~ ~opper 14 is enclosed by walls 14, 15, 16 and 19. Ridges 25 run in the direction of the slope of bottom 24 and terminate at trough opening 50 such that the 01 _7_ molten sulfur can pass through trough 26 to spout 27 for discharge. Also shown in FIG. 3 is the position of low 05 sulfur level sensor 46 within sensor tube 34. Flue 38 is also shown.
FIG. 4 illustrates details of trough entrance plate 50, It shows that plate 50 runs between walls 15 and 16 and carries a plurality of holes 51 and is posi-tioned at the lower edge of hopper bot-tom 24 and ridges 25 so that the molten sulfur that runs down sloping bottom 24 can pass through holes 51 into the trough 26 (not shown).
FIG. 5 illustrates two variations of the sloping bottom melter of this invention. It shows an embodiment wherein bottom 24 is more than one plane which several planes are angled toward one another and together slope toward the molten sulfur collection trough. Also shown in FIG. 5 is an alternate expanded surface bottom wherein a plurality of grooves 52 are cut in bottom 24 in place of the ridges previously illustrated. Although not shown, any similar corrugations or rippling which increased the bottom's surface by at least 25% over its linear area would be suitable.
It will be understood that although the sloping bottom melter apparaus of this invention has been described and illustrated with reference to particular embodiments, those skilled in the art will readily appre-ciate variations that can be introduced in the apparatus while still remaining within the purview of the invention described hereinabove, and set forth in the claims.

Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A sulfur powder melting apparatus comprising covered sulfur-containing hopper means having a heat transmitting bottom sloped at an angle from 10° to 70°
from horizontal, heating means located beneath said bottom to heat said bottom and melt sulfur in contact therewith, molten sulfur collecting means communicating with said bottom and located at the lower end of said bottom sloped at an angle of from 10° to 70° and molten sulfur discharge means exiting said molten sulfur collection means.

2. The sulfur powder melting apparatus as defined by Claim 1 wherein said heating means is a combustion heating means.

3. The sulfur powder melting apparatus as defined by Claim 2 wherein said combustion heating means is a gas burner.

4. The sulfur powder melting apparatus as defined by Claim 1 wherein said sloping bottom has an expanded surface area.

5. The sulfur powder melting apparatus as defined by Claim 4 wherein said sloping bottom contains ridges parallel to the direction of its slope.

6. The sulfur powder melting apparatus as defined by Claim 4 wherein said sloping bottom contains grooves parallel to the direction of its slope.

7. The sulfur powder melting apparatus as defined by Claim 4 wherein said molten sulfur collecting means comprises means for preventing the concurrent collection of solid sulfur particles.

8. The sulfur powder melting apparatus as defined by Claim 4 wherein said means exiting said molten sulfur collecting means discharges into mixing means in which said molten sulfur can be admixed into a coating composition.

9. In a sulfur powder melting apparatus comprising covered sulfur-containing hopper means having a heat transmitting bottom sloped at an angle from 10° to 70° from horizontal, heating means located beneath said bottom to heat said bottom and melt sulfur in contact therewith, molten sulfur collecting means communicating with said bottom and located at the lower end of said bottom sloped at an angle of from 10° to 70° and molten sulfur discharge means exiting said molten sulfur collect tion means the improvement which comprises an automatic shutoff for said heating means, which shutoff comprises temperature sensor means located at or about the top surface of the upper end of said sloped bottom and connected to means for shutting off the heating means when the temperature sensed by said sensor exceeds a preset temperature related to the melting point of sulfur.

10. The sulfur powder melting apparatus as defined by Claim 9 wherein said heating means is a combustion heating means.

11. The sulfur powder melting apparatus as defined by Claim 10 wherein said combustion heating means is a gas burner.

12. The sulfur powder melting apparatus as defined by Claim 11 wherein said preset temperature is a temperature in the range of from 48°F to 123°F above the melting temperature of sulfur.

13. The sulfur powder melting apparatus as defined by Claim 11 wherein said preset temperature is a temperature in the range of from 63°F to 103°F above the melting temperature of sulfur.