US1134846A - Process of preventing the escape of sulfur dioxid in smelting sulfid ores. - Google Patents

Description

Y W. A. HALL. PROCESS OF PREVENTING THE ESCAPE 0F SULFUR DIOXID IN SMELTING SULFID ORES'.

APPLICATION FILED JUNE 39. m3. RENEWED MAR. 1, 1915.

1,134,846 Patented A r. 6, 1915.

TO GAS WASHER v WILLIAM A. HALL, OF YORK, N. Y.

PROCESS or PREVENTING 'rnn escape or sunru' elnrox rn in smnn'rine sumrrn onus.

' raiser-sha es, 11915..

Application filed June 30, 1913, Serial No. 776,620. neaewea'nare'n 1, 1915. Serial No. 11,328.

To all whom it may concern 1 Be it known that I, TILLIAM A. HALL, citizen of the United States, residing at New York, in the county of New York and State of New York, have invented or dis .free sulfur, and, if desired, the subsequent] separation and recovery of this elemental sulfur from the exit gases, in a commercial form, thereby obtaining a valuable by prodnot.

The present invention relates to a process for the recovery in elemental and commercial form of the sulfur evolved from pyrites in the operation of smelting copper in the well known water jacketed pyritic smelters used for the purpose, and for preventing the discharge of noxious sulfur dioxid fumes from the furnace into the atmosphere.

In the manner in which the operation of pyritic smelting is at present conducted the only portion of the sulfur that is of use as fuel is that portion commonly known as the non-volatile which is below the pyrrhotite (Fe S state (generally considered as the Fe, FeS state). All the sulfur content of the pyrites above this Fe, FeS state, that is to say all of the volatile sulfur and a part of the non-volatile sulfur is separated from the pyrites and discharged without being of any use as a fuel in assisting the operation. At a certain zone in the furnace th1s separated portion of the sulfur existsin the furnace gases in an elemental condition, in the form of heavy sulfur fumes. This zone is approximately about 2% ft. above the slag forming nucleus, or 51} ft. above the twyers and perhaps 7 to 8 ft. below the top of the charge. Higher up in the furnace at or near the top of the charge where 1t meets with atmospheric air, this sulfur vapor burns fiercely to S0,. Could the current of fumes and gases issuing from the top of the furnace be hermetically sealed against the outer air, then this volatile sulfur would pass 011 in the elemental state and could be collected, but this has heretofore never accomplished owing to the necessity if-giving a freedischarge of the air blown in. through the tvvye'rs and consequent products .of combustion. Often from 5000 to 10000cubic feet of air is blown in per minute, and this is-greatly increased in volume within the furnace-owing'to its expansionupon heating to the temperature in the-focus. If th-is-- air=and products of combustion were not given a most free vent,-

the operation of -the furnace would be checked, I in any case there is naturally a greatinrush of-a'ir accompanying the feeding in of the pyrites charge.

If thehermetic sealing were possible, the discharge would contain much sulfur dioxid fromthe combustion taking place in the lOWQP-Pbfbififlflf the furnace, and although a certain portion of sulfurcould be recovered, :the sulfur vapor would be contaminated bythe presence-of much sulfur dioxid which in itself would be a great nuisance if permitted to escape into the outer air. Furthermore there would be lost a considerable sulfur value in this-sulfur dioxid. .In accordance with the present invention I condense and recover substantially all of this sulfur i. erboththat existing as elemental sulfur, that existing as S0,, in the gases and this I may accomplish by admitting a reducing flame, preferably with steam, into the upper level of the furnace. In case a furnace having a hermetically-sealed head is used, there is not sufficient inrush of false air, at the top of the furnace to do any great harm. Moreover enough internal pressure is created inthe furnace, by the expansion of theair blown in through the twyers, and the gases evolved in the decomposition of the pyrites, to prevent the above mentioned inrush of air, even if the reducing flame is not blown in at the upper level, but the sulfur already existing as S0, would be lost. By passing the products of combustion carrying. the elemental sulfur in suspension through separating devices hereinafter described, I can recover the sulfur. This reducing gas can be Water gas or air and Water gas obtained from a gas producer and containing much carbon monoxid and hydrogen, although other varieties of gas can be used. This gas flame serves a three-fold purpose: (1) it prevents oxidation of the sulfur vapor, (2)

it reduces the sulfur dioxid to suliur and (3) it imparts a'desirable high'temperature at the upper level of the furnace necessary to bring about this reduction, a's'the sulfur" dioxid cannot be deoxidized by reduction I excepting at very much higher temperaturesthan exist normally in the upper portion of the furnace. T his-reducing gas may be ad- 'mittedat 'aboutpthe normal level of the py ritic charge, thereby preventing the contact of free air with the top ofthe charge, but if. desired may be introduced at a lower. Also under certain-conditions, such as the employment of-a reducing gas poor;-

level.

inhydrogen, it is found desirable to admit along" with the reducing gas, a certain amount of steamor water vapor in order 7 to produce a certain amount of sulfureted hydrogen,- which is a practical agent for decomposing the sulfur dioxid present, said steam also decomposing any carbon oxysulfid (COS) that may be formed, but I do not care to limit myself to the use of this steam for under certain conditions (as for' instance where a little sulfur-dioxid may be allowed to escape) it may not be found necessary. The sulfur then contained in the gases leaving the upper part of the furnace is all, or substantially all, in the condition of elemental sulfur and can be readily separatedfrom' the nitrogen, carbon dioxid and other productsof combustion by any suitable means, as for instance by passing the entire volume of fumes through a gas washer or' condenser of the well known Theisen type or any other suitable gas washer designed specially for the extraction of solid and sticky matter from furnace gases. Such a device can be operated in a manner to create no back pressure on the ,furnace.

One diderence between the present haven tion and those described in my copending applications 725,024, filed Oct. 10, 1912; 770,946, filed May 31, 1913, and 773,456, filed June 13, 1913, which cases also show and claimthe treatment of sulfid ores with a reducing flame, is this that in the present case the reducing flame is not primarily used for decomposition of the pyrites c. e. the sep aration of the bulk of thesulfur from the pyrites or other ore and its volatilization are either from the action of steam on the hot menace pyrites, or by the action oi the hydrogen of the gas on'the pyrites. Also the stable equivf'alent for the bulk of the iron in the present case is not nascent oxygen obtained from the decomposition of water, but is atmospheric oxygen from the air admitted through the twyers and the silica of the quartz which is always used-in pyritic smelting.

The preferred temperature to be maintained by the reducing flames at the top of the ore charge may be stated asabout 700 (1., or a little over. It is obvious that the ore mustnot' be heated to 900 (3., or over, since it would then become molten, and any amount'of melting would cause it to sinter, and cause trouble.

Theprocess may be carried out in a furnaceas shown by way of example in the accompanying drawings, in which a modified structure of the ordinary water-jacketed pyritic smelter is illustrated,

In said drawing the charge is admitted through the doors 1, or in any other suitable manner, which doors should be capable of being tightly closed when ore is not being charged into the furnace. The air for the combustionof the sulfur of the orev is admittedthrough suitable twyers 2, connected with a belly pipe 3, in the usual manner, the charge of ore in' the lower part of the fur- .nace is maintained at the usual smelting temperature, and they gases, ascending through the vcharge. contain free sulfur, some $0 and CO and a large amount of free nitrogen, and are drawn 03 in the usual manner through the pipe 4, to which is connected a flue 5, carrying the gases to a gas washer, of any approvedtype. A stack 6 may also be provided for allowing the entire fumes and gases to pass into the atmosphere, "should the gas washer become temporarily 1 clogged up, or should repairs be necessary to the 'gas washer. This part of the process is all well known and old, and does not need any elaborate description here.

The line 7 of the drawing represents what may be termed the normal level of the charge of ore and flux in the furnace, al-

though this will vary more or less, and may at times be considerably above the blast lamps to be now referred to.

Slightly above the normal charge level of the furnace charge I provide suitable blast lamps 8'which I connect with a supply of airand gas 9 and 10 respectively, through which I introduce a reducing flame, for accomplishing the purposes above referred to.

If desired steam may also be introduced through either the pipe 9 or 10, along with the gas or air, or through a pipe 11, suitably connected with one or more of these blast lamps, or may be supplied to the furnace by independent pipes, but as stated above-the introduction of steam is to some extent op blast twyers 8 may be used for admitting- 1 gas alone, without any air, should it be found that quite large amounts of false air are entering through the charging doors, or otherwise. I may also prevent the entrance of false air to a very large extent, by allowing the gases in the smelter to be under more or less pressure.

The reduction of the S0 may or may not be completed within the furnace itself. In case material amounts of steam are used with the reducing flame some H s is formed, which will travel along with the gases still containing S0 and the reaction between these two will take place after the temperature has fallen somewhat, which will be out side the furnace itself, but before the gases reach the gas washer. In case the reducing flame does not contain much hydrogen and an insuflicient amount of steam is introduced with the flames, considerable COS may be formed. which will be acted upon by steam introduced into the exhaust flue leading to the gas washer, said steam decomposing the COS, according to the reaction which H 8 will reduce any SO still present in the. gases, in accordance with the reaction Accordingly it is advisable to carefully regulate the reducing flames for the complete ultimate reduction of all the S0,, without leaving material amounts of H 8 in the gases leaving the washer.

In all places in the process where steam-is referred to, it is obvious that water, in suitable amount could be used, since the temperatures are such as to convert such Water into steam, and the use of the term steam in the appended claims is intended to cover the use of water or any material which would be the equivalent, such as aqueous solutions.

I disclaim the treatment of the gases, after leaving the smelting furnace, with reducing gases, or with a bed of coke or the like, for the recovery of sulfur therefrom.'

prises introducing a reducing gas flame, into the upper level of the furnace, at a point near the normal charge level therein, said flame being capable of reducing a part at least of the sulfur dioxid to elemental sulfur, while preventing the access of suflicient air to the gases leaving the smelting furnace to oxidize any considerable quantity of the elemental sulfur existing in, or produced in said gases, until the temperature of said gases has fallen below the temperature at which free sulfur will oxidize, and separating the elemental sulfur from said gases.

2. A process of recovering elemental sulfur in smelting pyritic ores, and for preventing the escape of noxious gases, which comprises introducing a reducing gas flame together with steam, into the upper level of the furnace, at a point near "the normal charge level therein and under conditions capable of reducing a part at least of the S0 in the exit gases, and thereafter separating the elemental sulfur from the gases.-

3. A process of preventing the escape of noxious gases in smelting, which comprises the subjecting an upper layer of the sulfid ore charge, to the action of a reducing gas, while at a high temperature, and avoiding the presenceof suflicient free air at that point to reoxidize the elemental sulfur.

4. In smelting sulfid ores, the step of preventing the escape of sulfur dioxid which comprises reducing the same, by the introduction of reducing gases, into the upper part of furnace at a point materially above the focus, and while avoiding the presence, at that point, of sufficient free oxygen to reoxidize said reduced sulfur.

5. In smelting sulfid ore, the step of introducing a reducing flame into the furnace, at a point near the normal charge level therein for reducing sulfur dioxid, and while avoiding the presence, at that point, of suflicient free oxygen to reoxidize said reducedsulfur.

6. In smelting sulfid ore, the step of introducing a reducing flame, together with steam, into the furnace, at a point near the normal charge level therein at which point an excess of sulfur dioxid is present, for reducing a part at least of said sulfur, and while avoiding the presence of substantial quantities of free oxygen at that point.

7 In smelting sulfid ores, the step of introducing a reducing flame into the furnace, at a point near the normal charge level therein, for reducing the sulfur dioxid and introducing steam into the gases and fumes leaving the furnace.

8. In smelting sulfid ores, the step of subjecting the upper layer of the ore charge, to the substantially continuous action of a reducing flame.

9. A process which comprises smelting a sulfid ore charge in a blast of air, while premeeeee venting free access of the top of the ore In testimony whereof I have afixedl my charge to the action of air, ancl while subsignature, in presence of two Witnesses. jecting an upper layer of said ore charge, WllLLllAlfl A. HALL. to the action of a reducing flame, capable of Witnesses: 5 reducing at least the major portion of the A. B. FOSTER,

sulfur dioxid therein, into elemental sulfur. A. M. PERKINS

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