US1929502A - Process of treating sulphide materials - Google Patents

Description

Oct. 10, 1933.

S l. LEVY El" AL PROCESS OF TREATING SULPHIDE MKIERIALS Filed June 6, 1931 Patented Oct. 10, 1933 UNITED STATES PROCESS OF TREATING SULPHID MATERIALS Stanley Isaac Levy, Ottershaw, Kingston Hill, and William Somerville Millar, deceased, late of Middlesex, England, by Henry Dering,executor, Tregenna, Cherry Orchard, Staines, England, assignors, by direct and mesne assignments, to Sulphide Corporation of New York, a corporation of Delaware Application June 6, 1931, Serial No. 542,572, and in Great Britain July 26, 1930 9 Claims.

It has heretofore been proposed to treat sulphide materials such as minerals, ores, concentrates, mattes etc. with chlorine for the purpose of obtaining elemental sulphur and the chlorides of the metals. -In place of chlorine, sulphur chloride or ferric chloride, or mixtures of these separately or together with chlorine, with or without inert gases, may also be employed. Chlorine or a chlorinating medium may be recovered from the metal chlorides formed, by electrolysis or by oxidation; methods of recovery by electroly sis yield chlorine itself, methods of recovery by oxidation yield chlorine or ferric chloride, or mixtures of these, associated with nitrogen and inert gases, where air is employed for the oxidation treatment.

The chlorinating treatment may be carried out at relatively low temperatures, so that the chlorides formed are obtained in the solid state, and sulphur vapour driven off comparatively free from metal chlorides, or at higher temperatures, so that the chlorides formed are molten or partly or even completely vaporized in which case the sulphur driven ofl! will be associated with the metallic chlorides.

The present invention is concerned with chlorination of sulphide materials particularly sulphide iron ores at temperatures such that the metal chlorides formed are not melted, the sulphur driven off being unaccompanied by any considerable amounts of metal chlorides. In carrying out this treatment, it has generally been .attempted to employ the chlorinating gases either in counter-current to the sulphide material travelling through the furnaces, or by passing them through one or more stationary furnaces or beds containing the sulphide material;

We have found that such methods sometimes give rise to serious diiiicul ties, especially when, as is generally the'case, iron is present in the sulphide material to be treated when chlorine gas is being used as the chlorinating agent ferric chloride is always present near the point of entry of the chlorinating. gases; this is volatilized partially or completely at the temperature prevailing, and passing through the charge is reduced'by unchanged sulphide material, forming ferrous chloride and sulphur.- In this way, iron is removed from one part of the charge as ferric chloride, and deposited again in another part as ferrous chloride, as a result of which reaction, the furnace rapidly becomes blocked up. Where sulphur chloride is employed as a chlorinating medium, ferric chloride is not formed to the same extent, but in this case the charge tends to stick or ball together in sucha way as to prevent reaction. This may be due in some way to the increased quantity of sulphur which has to be carried as vapour in the gases when sulphur chloride is employed. Further difficultiesarise in all chlorination operations from the increase in bulk which takes place as the result of the formation of metal chlorides which have considerably lower densities than the sulphides from which they are formed. Another possible factor is the high ,crystallising power of the chlorides, which may cause them to build up together at the moment of formation. Whatever the cause may be, it is often found that if chlorinating gases be passed in counter-current to sulphide material moving through a furnace, or through stationary beds of such material, difliculties due to sticking and blocking very rapidly arise.

It has been attempted to overcome these difficulties by mixing the sulphide material with sand or other inert materials, but this device does not completely avoid the difficulty and introduces the disadvantage that large quantities of inert material must be handled.

The object of the present invention is to overcome these troubles and provide a method of working by which sulphide material may be treated, preferably when in motion through a furnace, without any difficulty arising. We have found that if chlorine, preferably as a mixture with inert gases, together with sulphide material, be caused to travel through a suitable furnace in the same direction, at temperatures within the range BOW-500 C., the charge remains dry and I granular, converts smoothly and rapidly and shows no signs of sticking'or blocking. The same effect is obtained when any other gaseous or vaporized chlorinating medium or mixture is employed in this way. 7

Our improved method may be carried out in any known type of furnace through which the solid is caused-to pass, and which provides effective contact between the solid and the gases. A convenient type for our purpose is a rotating tube furnace, the chlorinating gases being caused to enter at the same end as the sulphide material, and the gases carrying the sulphur vapours being drawn off from the end at which the chlorinated material is discharged. Another very convenient form is the superposed hearth furnace, through which the material is caused to pass by means of rabbles carried on arms moving over each hearth, such as the well-known Herreshofl, Wedge and MacDougall furnaces. In these, the solid material is fed in at the top and raked over each hearth, descending after traversing each to the one below, and finally leaving the furnace at the bottom. In this case, the chlorinating gases are led in at the top, and caused to pass, together with the solid, over each hearth in succession, finally leaving the furnace at the bottom..

We may also use furnaces of the tunnel kiln type, in which the solid passes from one end to the other of a long tunnel, either in separate waggons, or on a bed formed by a moving chain or the like. With this type of furnace it is useful to cause the gases, which pass through in the same direction as the sulphidematerial to circulate in' addition vertically upwards and downwards through that material by means of suitable arrangements of fans and baflles; an added advantage of this type is the possibility of close temperature control at all points by the use of heating or cooling or heat-exchange devices for the gases, in conjunction with the fans and baffles.

Another convenient form of furnace is a stationary cylindrical tube or kiln, through which the solid material is caused to pass by means of a screw, or of teeth or rabbles supported on arms fixed to a rotating axial shaft running through the furnace.

With very finely divided solid material, it is possible to obtain effective chlorination by the use of a jet furnace. In this form, the pulverised material is caused to pass through a fine jet by means of inert gas under pressure. The chlorinating gases are supplied to the furnace through an annulus round the jet, or openings adjacent to it, and pass through in the same direction as the cloud of solid particles. The chlorinating gases are preferably introduced at a moderately elevated temperature, generally ZUOVG 350 C., so that the reaction is initiated as soon as possible after the solid has left the jet.

Whatever form of furnace be adopted, the chlorinating gases and the finely divided sulphide material are caused to pass through in the same direction. In passing through the furnace, the solid continually exposes fresh surfaces to the gases; a smooth and regular reaction is obtained, in which the chlorinating agent or agents displace sulphur from the sulphide material. The sulphur is vapourized, and carried through and away from the furnace in the vapour form. We prefer to employ as chlorinating medium a mixture of chlorine with inert gases, so that sulphur may be removed in the vapour. form when the reaction is carried out at temperatures below its boiling-point. The operation is carried out most smoothly at temperatures within the range 330-'- 400 C., but no serious difficulties due to blockage or sticking occur within the range 300-500 C. At other temperatures, dimculties similar to those met in operating counter-current fiow or stationary bed methods have been encountered. The reactions are exothermic, and the temperature is most simply controlled by adjustment of the rate of feed of the reagents.

The exit gases are preferably removed at a temperature within the range 350-400 C., so that no important quantities of metal chlorides are present in the vapourized condition. The chlorinating gases will usually contain inert gases, so that the sulphur will be retained in the vapour state at temperatures below its boiling point, in accordance with well known scientific laws. If no inert gases are present, it is necessary to operate at a temperature above the boiling point of sulphur, and to remove any metal chlorides carried away with the sulphur by subsequent treatment.

Whilst the sulphide material may be completely chlorinated in this way in one passage through the furnace, we have also found it convenient, in order to obtain flexibility in control, to operate in such a way as to chlorinate the sulphide material to the extent of at least about and ordinarily to the extent of say to and to complete the chlorination by passing the nearly converted material so obtained through a second furnace, through which the gases discharged from the first, strengthened or not by fresh addition of chlorine or chlorinating media, are caused to pass in counter-current. In this way, the exit gases may be stripped down to mere traces of chlorine-or chlorine compounds and practically pure sulphur separated by causing them to pass through appropriate condensing apparatus, whilst at the same time the sulphide material is completely chlorinated.

This method of operating is illustrated diagrammatically in Fig. 1. The sulphide material for example, a sulphide-iron ore enters the first furnace A through the hopper B and conveyor C. The chlorinating gases enter at D and pass through' the furnace in the same direction BE as the solid, leaving the furnace at F, and passing through the inclined conduit FG to the second furnace H. The highly chlorinated material leaves the first furnace A at E and enters the second furnace H, passing through in the direction EJ and finally leaving the system by the conveyor K. The gases entering the second furnace H at G pass through in the direction GL in counter-current to the solid, leaving the furnace at L and passing by way of the dust chamber M and condenser N to fan P', by which they are discharged to atmosphere. The sulphur liberated by the reaction is carried off in the gases and collected in the condenser N, from which it fiows by seal 0 to storage.

In another modified method a proportion of the gases to be used for chlorination .is passed through the second furnace in counter-current to highly converted solid material; the exit gases from the second furnace, together with the remainder of the fresh gases to be used for chlorination, are passed through the first furnace in the same direction with .the fresh sulphide material, whereby the gases are stripped of chlorine compounds as before, whilst the sulphide material is chlorinated to the extent of 8090%, and then passes to the second furnace, in which the chlorination is fully completed by the further treatment with the proportion of fresh gases.

This method is illustrated diagrammatically in Fig. 2. The sulphide material enters the first furnace A by the hopper B and conveyor C, passes through in the direction CD, leaves by the hopper D and passes through the second furnace G in the direction EF, finally leaving by the hopper and conveyor H. A suitable proportion of the chlorinating gases enters the second furnace G at J, passes through in counter-current to the solid material in the direction FE, and then by way of the conduit EKL to thefirstfurnace A. The remaining proportion of the fresh chlorinating gases enters the first furnace A at L also, and the combined gases pass through the first furnace A in the same direction CD as the solid material, eventually leaving the system by way of the dust collector M, condenser N and fan P as before.

The essential feature in the treatment is that the chlorination of the fresh sulphide material should be carried to a high degree in a furnace through which the solid is caused to pass and exposed to the action of a stream of chlorinating gases moving in the same direction. Once a high "degree of conversion has been attained, the danger of sticking or blocking is much reduced, and counter-current operation may be employed if desired for the purpose of obtaining complete conversion of the sulphides to chlorides and of removing from the gases carrying the sulphur vapours substantially the whole of the chlorine or chlorine compounds.

We claim:

1. In the recovery of sulphur from sulphide materials containing iron, the process which comprises treating such material with a chlorinating medium to form ferrous chloride and displace the sulphur content thereof in elemental form, and subjecting said sulphide material and the chlorinating medium to the same progressive heat treatment.

2. A process of chlorinating sulphide material containing iron for the production of elemental sulphur and the formation of metal chlorides which comprises passing the sulphide material progressively through a furnace accompanied by a chlorinating medium, the amount of said medium being such as to insure the formation of ferrous chloride and the displacement of the sulphur content of the material in elemental form, and separating the sulphur from the chlorides produced.

3. In a process of subjecting sulphide material containing iron to a chlorinating treatment in a furnace for the production of elemental sulphur and the formation of metal chlorides, the step which comprises feeding the chlorinating medium and the sulphide material through the furnace in the same direction, while so controlling the amount of said chlorinating medium as to insure the formation of ferrous chloride and the displacement of the sulphur content of the material in elemental form, and separating the sulphur from the chlorides produced.

4. A process of chlorinating sulphide material containing iron in a furnace for the production of elemental sulphur and the formation of metal chlorides, in which the iron content of said material is converted to ferrous chloride with displacement of sulphur in elemental form, consisting in passing the sulphide material progressively through a furnace accompanied by a chlorinating medium in such proportion as to chlorinate the. material to the extent of at least 75% conversion of the iron to ferrous chloride and completing the chlorination operation by passing further chlorinating medium necessary to complete the conversion of the sulphide material through asecond furnace through which the partly chlorinated material is caused to pass in the opposite direction to such chlorinating medium.

5. A process of chlorinating sulphide material containing iron in a furnace for the production of elemental sulphur and the formation of metal chlorides, in which the iron content of said material is converted to ferrous chloride with displacement of sulphur in elemental form, consisting in passing the sulphide material progressively through a furnace accompanied by a chlorinating medium in such proportion as to chlorinate the material to the extent of at least 75% conversion of the iron to ferrous chloride, passing the material therebyl'partly chlorinated through a second furnace, passing the remainder of the chlorinating medium necessary for conversion of the partly chlorinated material through the said second furnace in counter current to such partly chlorinated material and passing the exit gases from the second furnace with any remaining chlorinating medium through the first furnace.

6. A process of chlorinating sulphide material containing iron for recovery of sulphur consisting in causing the sulphide material and a gaseous chlorinating medium to pass through a furnace in the same direction, while so controlling the amount of said chlorinating medium as to insure the formation of ferrous chloride and the displacement of the sulphur content of the material in elemental form, and separating the sulphur from the chlorides produced.

7. A process of chlorinating sulphide material containing iron for recovery of sulphur consisting in passing the sulphide material progressively through a furnace accompanied by a gaseous chlorinating medium in such proportion as to chlorinate the material to the extent of at least 75% conversion of the iron to ferrous chloride and completing the chlorination operation by passing further chlorinating medium necessary to complete the conversion of the sulphide material through a second furnace through which the partly chlorinated material is caused to pass in the opposite direction to such chlorinating medium. a.

8. A process of chlorinating sulphide material containing iron for recovery of sulphur consisting in passing the sulphide material progressively through a furnace accompanied by a gaseuos chlorinating medium in such proportion as to chlorinate the material to the extent of at least 75% conversion of the iron to ferrous chloride and passing the material thereby partly chlorinated through a second furnace and passing the remainder of the chlorinating medium necessary for conversion of the partly chlorinated 125 material through the said second furnace in counter current to such partly chlorinated material and passing the exit gases from the second furnace with any remaining chlorinating medium through the first furnace. 130

9. A process of chlorinating sulphide material containing iron for recovery of sulphur consisting in causing the sulphide material and a gaseous chlorinating medium to pass through a furnace in the same direction at a temperature 55 range of BOO-500 C., the amount of said medium being such as to insure the formation of ferrous chloride and the displacement of the sulphur content of the material in elemental form.

STANLEY ISAAC LEVY, Henry Bering, Executor of the Last Will and Testament of William Somerville Millar, Deceased.

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