US3578417A - Vaporizing sulfur from ore by direct contact with heated pebbles - Google Patents

Abstract

THE CONTINUOUS METHOD OF AND APPARATUS FOR RECOVERING SULFUR FROM ORES BY FEEDING SURFACE SULFUR ORE INTO A CLOSED CONVEYOR AND SIMULTANEOUSLY HEATING THE ORE WITH HEATED PEBBLES WHILE SLOWLY MIXING AND CONVEYING THE MIXTURE THROUGH THE CONVEYOR AND HEATING THE ORE ABOVE THE BOILING POINT OF SULFUR TO VAPORIZE THE SULFUR IN WHICH THE VAPORIZED SULFUR IS PASSED THROUGH A CONDENSER FOR RECOVERY. THE DEPLETED ORE AND PEBBLES ARE DISCHARGED FROM THE CONVEYOR AND SEPARATED WITH THE PEBBLES BEING CONVEYED TO A HEATER FOR REHEATING AND REUSE. FOR GREATER EFFICIENCY THE HOT EXHAUST GASES FROM THE PEBBLE HEATER ARE FLOWED IN A COUNTERFLOW HEAT EXCHANGE RELATIONSHIP WITH THE CONTAINER TO HEAT THE MIXTURE. THE CONVEYOR HAVING AN ELONGATE POWER SHAFT POSITIONED LONGITUDINALLY IN THE CONTAINER FOR ROTATIVE MOVEMENT WITH A PLURALITY OF PADDLES POSITIONED ADJACENT THE INTERIOR WALLS OF THE CONTAINER AND CONNECTED BY THE SHAFT FOR ROTATIVE MOVEMENT TO MIX THE ORE AND PEBBLES, MOVE THE MIXTURE ALONG THE CONVEYOR, AND KEEP THE INTERIOR WALLS OF THE CONTAINER CLEANED FOR GREATER HEAT TRANSFER. THE VOLUME OF PEBBLES BEING GREATER THAN THE VOLUME OF ORE IN THE CONTAINER TO MORE EASILY CONVEY THE MIXTURE THROUGH THE CONVEYOR.

D R A W I N G

Description

May 11, 1971 J, M, DALE VAPORIZING SULFUR FROM ORE BY DIRECT CONTACT WITH HEATED PEBBLES Filed June 30. 1969 .A AmANw ATTOR/V'VJ United States Patent Office n3,578,417 Patented May 1l, 1971 U.S. Cl. 23--294 11 Claims ABSTRACT OF THE DISCLOSURE The continuous method of and apparatus for recovering sulfur from ores by feeding surface sulfur ore into a closed conveyor and simultaneously heating the ore with heated pebbles while slowly mixing and conveying the mixture through the conveyor and heating the ore above the boiling point of sulfur to vaporize the `sulfur in which the vaporized sulfur is passed through a condenser for recovery. The depleted ore and pebbles are discharged from the conveyor and separated with the pebbles being conveyed to a heater for reheating and reuse. For greater eiciency the hot exhaust gases from the pebble heater are iiowed in a counterflow heat exchange relationship with the container to heat the mixture. The conveyor having an elongate power shaft positioned longitudinally in the container for rotative movement with a plurality of paddles positioned adjacent the interior walls of the container and connected by the shaft for rotative movement to mix the ore and pebbles, move the mixture along the conveyor, and keep the interior walls of the container cleaned for greater heat transfer. The volume of pebbles being greater than the volume of ore in the container to more easily convey the mixture through the conveyor.

BACKGROUND OF THE INVENTION The recovery of sulfur from sulfur ores that lie on or near the surface cannot be mined by the Frasch process.

In spite of the large amount of known sulfur reserves in such surface ores a lack of commercial exploitation of these ores has occurred because of a problem of economics as well as a problem in processing.

However, the recent increase in the market price of sulfur has increased the potential economic attractiveness of these largely heretofore untapped sulfur reserves. Various processes such as flotation, autoclaving, solvent extraction and others have been attempted, but have been largely unsuccessful. The present process and apparatus is directed to the thermal process of recovering sulfur and operates on the principle of heating an ore containing sulfur to a high enough temperature so the sulfur will be vaporized and driven off. The thermal process avoids many of the disadvantages of other processes.

SUMMARY The present invention is directed to a -method of and an apparatus for recovery of sulfur from surface ores in which the ore is fed into a closed conveyor and mixed with heated pebbles in which the heat from the pebbles raises the ore temperature to above the boiling point of the sulfur creating sulfur vapors which are passed to a condenser and the sulfur recovered. The depleted ore and pebbles are discharged from the conveyor and are separated with the pebbles being conveyed to a pebble heater where they are reheated and reused.

Another feature of the present invention is the provision of utilizing the exhaust heat from the pebble heater which is passed in a counterflow heat exchange relationship with the conveyor for additionally heating the mixture therein.

Another feature of the present invention is the provision of mixing a volume of pebbles greater than the volume of ore in the conveyor, and preferably as much as three or four times greater in order to insure that the mixture can be satisfactorily moved by the conveyor since sulfur becomes quite viscous when heated.

A still further feature of the present invention is the provision of a conveyor which mixes the heated pebbles and ore suiciently to vaporize the sulfur in the ore, but slowly enough so as not to churn up dust which might be carried out with the vapors, and additionally the conveyor removes material from the internal walls of the conveyor container for improving the heat transfer from the pebble heater exhaust gases into the conveyor.

A still further object of the present invention is the provision of a process and apparatus for recovering sulfur from surface ores in which the ore is fed through an air lock into a container and heated pebbles are heated above the boiling point of sulfur and inserted through an air lock and into the container in which an elongate power shaft is positioned longitudinally for rotative movement with a plurality of paddles positioned adjacent the interior walls of the container and connected to the shaft for mixing the pebbles and ore together and conveying the mixture along the container and a condenser is connected to the container for receiving the vaporized sulfur from the container and condensing the sulfur and having an outlet from the container for removing the depleted ore and pebbles with means for separating the pebbles from the depleted ore and may be returned to the heater and reused. In addition, the exhaust gas from the pebble heater may be reused to preheat the pebbles which have been separated from the depleted ore.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of the schematic of the flow process and apparatus of the present invention, and FIG. 2 is a view taken along the line 2 2 of FIG. l.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings and particularly to FIG. 1, the reference numeral 10 generally indicates an apparatus for recovering sulfur and generally includes a container 12 having a conveyor 14 therein, a pebble heater 16, and a condenser 18.

The container 12 is a closed container having an ore inlet line 20 which admits surface sulfur ore from a suitable source such as from a storage bin 22 through a conventional air lock 24` The ore in the storage bin 22 is surface ore which has been ground up prior to storage in bin 22, which normally contains approximately 30% by Weight of elemental sulfur, from which it is desired to extract the sulfur. A pebble inlet line 26 is provided to the container 12 through a conventional air lock 28 from the pebble heater 16 through which pebbles have been fed, such as by gravity. An outlet line 30 from the container 12 is provided through an air lock 32 for removing the mixture of depleted ore and pebbles after processing. Thus, the closed container 12 prevents any air or oxygen from entering the system thereby avoiding any undesirable igniting and burning of the sulfur therein.

The pebble heater 16 may be any suitable and conventional heater, such as a rotary direct tired heater, which is supplied with a fuel, such as gas, from line 34 to heat the heat carrying pebbles to a temperature above the boiling point of sulfur, 832 F., and as high as thermally efiicient, such as 2500 F., and preferably to an approximate temperature of 2200 F. The heat carrying pebbles may be of any suitable material such as stainless steel or ceramic and may be of any convenient size, for example 2 inches in diameter. The heated pebbles flow through the air lock 28 and inlet line 26 to the container 12 to raise the temperature of the mixture to above the boiling point of the sulfur whereby the sulfur is driven off as a vapor.

Preferably, the conveyor 14 includes an elongate power shaft 36 positioned longitudinally in the container 12 for rotative movement by any suitable means (not shown) and includes a plurality of paddles 38 positioned adjacent the interior walls of the container 12 and connected to the shaft 36 by radially extending arms 40. The paddles 38 are slowly rotated, for example only, one revolution per two minutes, to thoroughly mix the mixture of heated pebbles and the ore to drive off the sulfur from the ore, but slowly enough so as not to churn up dust from the ore which might be carried out with the sulfur vapors and contaminate the sulfur. Additionally, the paddles 38 include a slanted portion 42 on the leading edges of the paddles whereby the mixture of the heated pebbles and ore are moved by the paddles from the inlets 20 and 26 toward the outlet 30'.

A still further function of the paddles 38 is to scrape the material adjacent the interior walls of the container 12 for increasing heat transfer into the container 12. That is, the exhaust or flue gases from the pebble heater 16 ow through heater exhaust line 44 and through a heat exchange manifold 46 which is positioned in a counterflow heat exchange relationship with the exterior of the container 12, here shown as enclosing the container 12, to provide additional heat for heating the mixture in the container 12. However, the sulfur in the mixture adjacent the interior wall of the container 12 on vaporization leaves a sulfur free dry powdery gangue which acts as an insulator and retards further transfer of heat to the mass of the mixture. The action of the paddles 38 adjacent the interior walls 13` of the container 12 scrapes and destroys this insulation layer so that heat from the manifold 46 may be more easily transferred through the wall of the container 12 and into the mixture by improving the heat transfer coefficient.

Two difficulties arise in processing sulfur ores. When the ore is heated to just above the melting point of sulfur, 238 F., the liquid sulfur forms a paste with the gangue. Above 320 F., sulfur becomes extremely viscous and makes the material (or paste like mixture) even more difficult to handle. These difficulties are overcome in the present process by mixing the pebbles with the ore in the container 12. Thus, the volume of pebbles inserted into the container is greater than the volume of ore, and preferably the ratio of volume of pebbles to ore is three or four to one. With a greater portion of the mass in the container being formed of the pebbles, the mass can satisfactorily be moved by the conveyor 14. Also, because of these properties of sulfur, it is desirable that the pebble inlet 26 be located adjacent to the ore inlet 20, or if desired, even upstream from the ore inlet 20 to insure that the pebbles may be mixed with the ore to avoid clogging up the conveyor 14.

Sulfur vapor outlets S are provided connected to the container 12 for allowing passage of the sulfur vapors which are driven off from the heated mixture to pass through vapor line 52 and a gas cleaning apparatus 51, if desired, such as a cyclone or electrostatic cleaner to remove contaminants, to a conventional sulfur vapor condenser 18 which may be air or water cooled wherein the sulfur vapors are recovered as liquid sulfur from condenser outlet 54,

The sulfur depleted ore and pebbles are discharged from the container 12 through the outlet 30 and air lock 32 to suitable means for removing the pebbles from the depleted ore such as screen 56. The depleted ore or gangue are discharged through an outlet 58 and discarded. The separated pebbles 11 are fed back to the pebble heater 16, such as through a suitable pebble elevator 60, for reheating and reuse and therefore operate in a closed loop circuit. And if desired, the exhaust gas outlet 44 from the pebble heater 16 may form a heat exchanger 62 with the elevator `60 to preheat the pebbles prior to their entry into the heater 16 from elevator outlet 64.

In operation, ground up surface sulfur ore is continuously fed through air lock 24 and inlet 20, such as from a bin storage 22, into the container 12. Simultaneously, pebbles Which are heated in the heater 16 are continuously fed through air lock 28 through pebble inlet 26 into the container 12 where they are mixed by the conveyor 14 by the action of the paddles 38 to heat the mixture above the boiling point of 832 F. of the sulfur driving off the sulfur as vapors. The mixture of pebbles and ore is moved through the container 12 continuously by the conveyor 14 and additional heat may be supplied from the flue gases from the heater 16 flowing through the heating manifold 46 from line 44. The sulfur vapors are passed through outlets 50 through line 52 to the sulfur condenser 18 where the sulfur is recovered as a liquid from outlet 54. The depleted ore and pebbles are discharged from the container 12 through outlet 30 and air lock 32 to separation means such as a screen 56 with the depleted ore being discarded through outlet 58 and the pebbles being conveyed again to the heater 16 such as by elevator 60 for reheating and reuse. The present process and apparatus operates on a continuous cycle of heating the sulfur ore to a high enough temperature so that the sulfur will be vaporized and driven off without involving the disadvantages in other sulfur recovery processes.

It is believed that the process of the present invention is apparent from the foregoing description of a presently preferred apparatus of the invention. The process, however, comprises the steps of feeding a sulfur ore into a container and preventing air from entering the container, heating heat carrying pebbles to a temperature greater then the boiling point of sulfur, feeding the heated pebbles into the container and the ore whereby the ore is heated and the sulfur is vaporized, removing the vaporized sulfur to a condenser for recovering the sulfur, removing the depleted ore and the pebbles from the container, and separating the pebbles from the depleted ore for reuse. The process also comprehends heating' the pebbles in the range of from greater than 832 F. to 2500@ F., slowly mixing the heated pebbles with the ore to thoroughly heat the mixture without creating undesirable dust in the container. The process further includes the step of removing material from the internal walls of the container as heat is supplied to the external surface of the container from exhaust from the pebble heater to increase heat transfer into the container. The process further comprehends inserting a greater volume of pebbles into the container than the volume of ore inserted therein to reduce the viscosity of the mixture for ease of conveyance through the container.

The present invention, therefore, is well adapted to carry out the objects and attain the ends and advantages mentioned as well as others inherent therein.

What is claimed is: 1. The continuous method of recovery of sulfur from ores comprising,

feeding the ore into an elongate container, preventing air from entering the container, heating heat carrying pebbles to a temperature greater than the boiling point of sulfur and in the range of from above about 862 F. to about 2500 F.,

feeding the heated pebbles into the container and into the ore whereby the ore is heated and the sulfur is vaporized, passing the mixture of ore and pebbles concurrently through said container while agitating the mixture,

removing the vaporized sulfur from said container to a condenser for recovering the sulfur,

removing the depleted ore and the pebbles from the container, and

separating the pebbles from the depleted ore for reuse.

2. The process of claim 1 wherein the ore and heated pebbles are mixed as they are moved through the container but are mixed slowly to prevent undesired dust from the ore from mixing with the vaporized sulfur.

3. The process of claim 1 wherein the exhaust heating gas from heating the pebbles flows in a heat exchange relationship with the outside of the container heating the mixture of ore and pebbles.

4. The process of claim 1 wherein the heated pebbles are fed into the container adjacent the point of admittance of the ore into the container.

5. The process of claim 1 wherein the volume of pebbles inserted into the container are greater than the volume of ore inserted into the container.

6. The continuous process of recovery of sulfur from ores comprising,

feeding the ore into a substantially horizontal elongated container, preventing air from entering the container, heating heat carrying pebbles to a temperature in excess of the boiling point of sulfur and in the range of from above about 862 F. to about 2500 F.,

inserting the heated pebbles into the ore in the container whereby the ore is heated and the sulfur is vaporized,

mixing the ore and pebbles in the container,

moving the ore and pebbles along the container,

removing the vaporized sulfur from the container to a condenser for recovering the sulfur,

removing the depleted ore and pebbles from the container,

separating the pebbles from the depleted ore for reuse.

7. The process of claim 6 wherein the volume of pebbles inserted into the container is greater than the volume of ore.

8. The process of claim 6 wherein the exhaust heating gas from heating the pebbles ows in a counterow, with respect to the direction of iiow of the ore and pebbles through the container, heat exchange relationship with the outside of the container for heating the mixture in the container.

9. The process of claim 8 including removing material from the internal walls of the container for improving the heat transfer through the container.

10. The process of claim 1 wherein the exhaust heating gas from heating the pebbles ilows in a counterflow, with respect to the direction of ow of the ore and pebbles through the container, heat exchange relationship with the outside of the container heating the mixture in the container.

11. The process of claim 10 including removing material from the internal walls of the container for improving the heat transfer through the container.

References Cited UNITED STATES PATENTS Re. 23,318 1/1951 Porter 23-294X 1,535,468 4/1925 Hedges 23-294 1,614,387 1/1927 Pereda 165-107 1,782,225 11/1930 Bacon 23-227 1,900,667 3/ 1933 Raloer 23-227X 1,946,349 2/1934 Brown 23-227X 2,420,376 5 1947 Johansson 263-19B 2,63 6,723 4/1953 Harter 26S-19B 2,872,386 2/1959 Aspegren 26S-19B 2,877,100 3/ 1959 Hartley 23-227X 3,068,091 12/1962 Kirkland 75-36 3,102,792 9/1963 Eads 23-294 FOREIGN PATENTS 353,830 5/1905 France.

NORMAN YUDKOFF, Primary Examiner S. J. EMERY, Assistant Examiner U.S. Cl. X.R.

Images