US1017839A - Recuperative roasting-kiln. - Google Patents

Description

J. ZBLLWEGER.

REGUPERIATIVE ROASTING KILN. APPLICATION FILED JAN. 9, 1911.

1,017,839. Patented Feb.20,1912.

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UNITED STATES PATENT OFFICE.`

JOHN ZELLWEG-ER, OF ST. LOUIS, MISSOURI.

RECUPERATIVE ROASTINGr-KILN.

To all 'whom it may concern:

Be it known that I, JOHN ZELLWEGER, a citizen of the United States, residing at St. Louis, Missouri, have invented a certain new and useful Improvement in Recuperative Roasting-Kilns, of which the following is a full, clear, and exact description, such as will enable others skilled in the art to which it appertains to make and use the same.

This invention relates to kilns such as are used for roasting ore.

When ore, such as zinc sulfid known as zinc blende is heated in a roasting kiln in the presence of air, its components are oxidized into the products zinc oxid and sulfur dioxid. If the sulfur dioxid is to be utilized in the manufacture of sulfuric acid it should form at least 5% of the total roast gases treated for such purpose, and should be associated with little or no carbonaceous gases such as carbon dioxid. Mutile kilns produce the results above-mentioned but such kilns are not entirely satisfactory on account of the excessive expense in furnace material, fuel and labor. Y

The main object of my present invention is to provide a mechanical roaster which is so designed that a large percentage of sulfur dioxid will be separated from the fire gases in the kiln and delivered in concentrated form without unnecessary dilution. To this end I have designed a kiln which is so constructed that the carbonaceous fire gases are withdrawn from the hot part of the kiln chamber which contains the ore that is nearly roasted, and fresh air, is supplied to the fresh ore so as to oxidize the fresh ore under the iniiuence of heat produced by the burning ore, the fresh air being preferably heated before it is supplied to the fresh ore so as to accelerate the oxidizing process.

Another object is to provide a roasting kiln having a recuperator that causes part of the heat from the outgoing fire gases to be returned back into the kiln chamber, the recuperator preferably consisting of fire flues and air chiots arranged adjacent each other so that the heat which is conducted through the walls of the fire flues will heat the air in the air ducts and suitable suction-producing devices for causing fresh air to travel through said air ducts and enter the cooler part of the kiln chamber and also causing the fire gases in the kiln chamber Specification of Letters Patent.

Application filed January 9, 1911.

Patented Feb. 20, 1912.

Serial No. 601,709.

to be withdrawn therefrom through said fire flues.

Another object of my invention is to provide a roasting kiln which is so designed that the heat which is conducted through the roof and hearth of the kiln chamber is utilized to heat air that oxidizes the fresh ore, and also to heat the fuel that is used to desulfurize the partially roasted ore, the fuel being preferably supplied to suitable burners by means of fuel iues arranged under the hearth of the kiln chamber.

Another object is to provide a roasting kiln having means of novel construction for preventing the ore along the sides of the hearth from cooling. And still another object is to provide an ore-stirring apparatus of novel construction.

Other object-s and desirable features of my invention will be hereinafter pointed out.

Figure 1 of the drawings is a vertical transverse sectional view of an annular recuperative roasting kiln constructed in accordance with my invention, taken' on approximately the line I-I of Fig. 2, said view also showing a vertical longitudinal section of the kiln chamber and recuperator taken through the center of same, as indicated by the section lines II-II of Figs. 1 and 2; Fig. 2 is a horizontal sectional view, the lower right hand part being taken on the line III-III of Fig. 1, the left hand parton the line IV-IV of Fig. 1, and the upper right hand part on the line v V of Fig. 1; Fig. 3 is a longitudinal sectional view of the ore-stirrer; Fig. 4c is a cross sectional view of said stirrer; Fig. 5 shows part of the shaft on which the stirrer is mounted; and Fig. 6 illustrates the key bar that secures the stirrer to its shaft.

I have herein illustrated my invention embodied in an annular roasting kiln of the type shown in my prior U. S. Patent No. 976,769, dated November 22, 1910, but I wish it to be clearly understood that my present invention is not limited to annular kilns for it is applicable to various other types of kilns.

Referring to the drawings which illustrate the preferred form of my invention, A designates a segmental annular kiln chamber or roasting chamber provided at its receiving or charging end with a door 1 and at its rear end, or discharge end, with a door 2, both of Which are normally closed. The inner side Wall 3 of said kiln chamber is provided with a horizontally disposed slot for receiving a radially-disposed stirrer shaft 1 having a stirrer S which moves the ore over the hearth, and a truss B is provided for supporting the arched roof 5 of the kiln chamber, the outer Wall and the hearth of said kiln chamber being designated by the reference characters 6 and 7, respectively. The horizontal slot in the inner side Wall 3 of the kiln chamber is closed by the annular shield plate 8 through which the stirrer shaft t projects, and suitable means is provided for sealing the edges of said shield plate so as to prevent air from entering` the kiln chamber through the horizontal slot which said shield plate covers. The shield plate 8 is braced by a number of horizontally-disposed brace' rods 9 that project radially from a bearing member 10 which is supported on a vertical shaft 11 at the center of the kiln, and the lower edge of said shield plate rests on rollers 12 Which are rotatably mounted on stationary bearings arranged outside of the inner Wall 3 of the kiln chamber. The stirrer shaft 4 is also journaled in the bearing member 10, and any suitable means may be used for rotating said shaft and for causing said shaft to travel around the vertical shaft 11 as an axis so as to move the stirrer S longitudinally of the hearth on Which the ore rests. The means herein shown for rotating` the stirrer shaft consists of a driven gear 13 that meshes with a miter gear 14 on the stirrer shaft 4, and the means for bodily moving said stirrer shaft around the kiln consists of a traction gear 15 on said shaft that meshes with a circular cog track 16. Most of the parts previously described are similar in general characteristics to the corresponding parts of the kiln shown in my patent above referred to and operate in a similar manner, but I will now describe the features that distinguish my present invention from the kilns that have heretofore been in use.

Instead of arranging the burners throughout the entire length of the kiln chamber, as has heretofore been the general practice, I arrange the burners in such a manner that the ore is subjected to artificial heat or lire gases only When it is traveling through the latter portion or rear portion of the kiln chamber after most of the sulfur has been extracted. The ore in the front portion of the kiln chamber is not subjected to artiicial heat except When the kiln first started but air is supplied to this portion of the kiln chamber to oxidize the fresh cre and thus produce heat, this heat gradually accumulating and raising the temperature of the ore to such a degree that the ore in the presence of air loses more than 80% of its sulfur under the influence of its own heat during its travel over the front portion of the hearth. Then the contents of the sulfur in the ore has been reduced to about 8%, the heat produced by its oxidation has to be supplemented by heat from fuel, and toward the end of the-roasting process it has to be maintainedl entirely by artificial heat from fuel. Therefore, I arrange the burners in the kiln chamber in such a manner that the ore is subjected to artificial heat only when it is traveling through the rear portion of the kiln chamber, and I have designed the kiln in such a manner that the fire gases from this artificial heat do not mingle with the sulfur gases extracted from the ore that is traveling over the front portion of the hearth. Consequently, my improved kiln not only delivers a larger percentage of the sulfur gases in suitable condition to be used in the manufacture of sulfurie acid, but it is also inexpensive to operate.

The burners 17 are preferably arranged in ledges or curbs 1S at the sides of the hearth 7, as shown in Fig. 1, and in the rear portion of the kiln chamber A over which the recuperator extends, as hereinafter described. The front portion of the kiln chamber A, shown in the lower righthand corner of F ig. 2, is not provided With burners that are used when the kiln is in full operation, but this portion of the kiln chamber is provided With auxiliary burners 17EL that are used when the kiln is first started and Which are cut out of service after the kiln chamber has become heated. The burners 17 and 17a communicate with fuel fines 19 and branch flues 19a arranged under the hearth 7, as shown in Fig. 1, and air ports 2O are arranged adjacent the burners, as shown in Fig. 1, to supply air thereto, each burner being preferably provided With a suitable controlling valve Q1 of any preferred type or design, the valves herein shoivn being slide valves that are provided With handles 21a. l/Vhile I prefer to arrange burners at both sides of the hearth a single set of burners at one side of the hearth could be used if desired, and instead of arranging said burners in the ledges or curb at the sides of the hearth they could be arranged in the side walls of the kiln chamber. I prefer the construction herein shown, however, for it facilitates the introduction of the tire into the kiln chamber and the curbs 1S hold the ore far enough aivay from the side Walls of the kiln chamber to prevent the ore from cooling.

The recuperator consists of a plurality of segmental-shaped fire fines 22, and air ducts' Q3 arranged over the roof 5 of the latter half or rear portion cf the kiln chamber in Which the greatest degree of heat is attained, the air ducts being arranged between the fire flues and extending parallel to same.

These fire flues 22 communicate with a chimney 24 or other suitable suction-producing device, as shown in Fig. 2, so thatthe fire gases in the rear portion of the kiln chamber will be drawn upwardly through ports 22aL in the roof of the kiln chamber, thence longitudinally through said iire iues in the direction indicated by t-he arrows to the ports 22b which lead to the chimney 24, the outlet ports 22a for the fire gases being located adjacent the middle of the kiln chamber. The front ends of the air ducts 23 aie open, as shown in Fig. 1, so that air will pass into said ducts and travel through same in the direction indicated by the arrows in Fig. 2, to inlet ports 23a that are formed in the roof of the kiln chamber at a point intermediate the front end of said chamber and the outlet ports 22a through which the fire gases escape from the kiln chamber. The sulfur gases extracted from the ore in the front portion of the kiln chamber are withdrawn from said chamber by means of an exhaust fan 25 or other suitable suctionproducing device that communicates with a discharge port 26 formed in the roof of the kiln chamber adjacent the charging end of same, as shown in Fig. 2, said suction device also operating to draw the air through the air chiots 23 of the recuperator and into the kiln chamber.

lhile I Aprefer to construct the kiln in the manner herein shown, it will, of course, be understood that the length of the iire flues and air ducts of the recuperator, and the location of the ports in the roof of the kiln chamber could be varied without departing from the spirit of my invention. Therefore, I do not wish the terms front and rear portion of the kiln chamber or hearth to be construed as meaning the front and rear halves of the kiln chamber or hearth.

'Ihe two exhausting or suction devices 24 and 25 produce a neutral Zone in the kiln chamber A between the outlet ports 22a for the fire gases and t-he inlet port-s 23L for the fresh air, in which neutral zone the ow of gases is slow and changeable in direction if the fresh air supply is limited. By admitting a surplus of air, however, part of this air will ow to the ire ports 22a and leave the kiln chamber while the other and larger part of the air will flow over t-he fresh ore on the front portion of the hearth and oXidize it. It will thus be seen that the tire gases dov not mingle with the sulfur gases in the front portion of the kiln chamber for said fire gases are withdrawn from the kiln chamber at a point about halfway between the ends of same, and the sulfur gases are withdrawn from the kiln chamber at the front or charging end of same. rIhe withdrawal of the hot ire gases from the middle portion of the kiln chamber would cause a loss of heat if said gases were discharged direct-ly through a chimney, but in my improved kiln the heat from said gases is utilized to heat fresh air that is supplied to the kiln chamber to oXidize the fresh ore, a large part of the heat in the out-going fire gases passing through the partition walls between the fire flues 22 and the air ducts 23 and thus being taken up by the ingoing air. By having the fire gases and the fresh air low in opposite directions through the recuperator it is possible to heat the ingoing air to near the temperature of the outgoing fire gases, especially if the recuperator is arranged over the hot part of the kiln chamber, as herein shown. By introducing fresh heated air into the front portion of the kiln chamber, the desulfurization of the ore is greatly accelerated and consequently more sulfur is saved.

Any suitable kind of stirrer can be used but I prefer to use a stirrer S of the kind herein shown because such a stirrer distributes the ore evenly over the hearth and does not work it to one side o-r the other. Said stirrer consists of a plurality of sections 27 that are adjustably mounted on the shaft 4, each of said sections having a hub that is provided with radially projecting blades. The shaft 4 is provided with a seat or guideway for a key-bar 28 that consists practically of a number of keys integrally connected together, the inner one of these keys having parallel sides, the second one a slight taper, and the third one twice the taper of the second. The hubs of the sections 27 have key seats which conform to the general shape of the keys on the key-bar but the width of the key seats in the second and third sections is slightly greater than the width of the keys which coperate with said sections. The key seat in the shaft 4 is not tapered but it is so designed that the key-bar can be moved longitudinally of the shaft, the means herein shown for adjusting the key-bar consisting of a threaded eXtension 28a on the key-bar passing through a yoke 29 on the shaft and having a nut 28b mounted thereon. 'By moving the key-bar inwardly the wings on the second section will be arranged at a dierent angle with relation to the wings of the first section and the wings of the third section will be arranged at still a greater angle with relation to the wings of the first section, the pressure which the ore eXert-s on the wings or blades of the stirrer operating to hold the different sections of the stirrer in adjusted position.

While I prefer to construct the recuperator in the manner previously described, it will, of course, be understood that the same result could be obtained *in various other ways. For example, a large air duct or flue could be arranged between the roof of the kiln chamber and a fire flue, and suitable outlet ports or passageways provided for permitting the fire gases in the rear portion of the kiln chamber to enter said fire flue, and suitable inlet ports provided for causing jets of air to enter the front portion of the kiln chamber. Furthermore, while I have herein shown the kiln chamber as a continuous chamber having two portions, which for the sake of clearness I have designated the front portion and the rear portion, I do not wish it to be Vunderstood that my broad idea is limited to the exact construction herein shown for the same results could be accomplished in various other ways. Therefore, I wish the terms front and rear portions to be construed as meaning the cool and hot portions of the kiln chamber respectively, irrespective of whether said two portions are arranged in the same horizontal plane or in different horizontal planes.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

l. An ore roasting kiln comprising a kiln chamber, means for subjecting ore in a portion of said kiln chamber to the radiating heat of fire gases within said chamber, means for withdrawing said fire gases from this portion of the kiln chamber, means arranged outside of the kiln chamber for causing fresh air to be heated by the outgoing fire gases and to be introduced into a different portion of the kiln chamber so as to oxidize the ore and produce heat therein, means for withdrawing the gases produced by the oxidation of said ore, and means for moving the ore through said kiln chamber.

2. An ore roasting kiln comprising a kiln chamber, means for supplying air to the ore in the front portion of said kiln chamber so as to oxidize same, means for thereafter subject-ing said oxidized oreto radiating heat from tire gases within said chamber, and means for preventing said fire gases from mingling with the gases in the kiln chamber that are extracted from the fresh ore during the process of oxidizing same.

8. An ore roasting kiln comprising a kiln chamber, means for conveying ore through said kiln chamber, means for extracting the main portion of one of the constituents of said ore in one part of the kiln chamber and conducting it .out of said kiln chamber, means for subsequently subjecting the ore to the radiating heat of fire gases within another part of the kiln chamber so as to roast said ore, and means for preventing the tire gases inside of one part of the kiln chamber from -mingling with the gases inside the other part of the chamber that are extracted from the ore in this part of the kiln chamber.

4. An ore roasting kiln, comprising a continuous kiln chamber that is adapted to receive ore, means for roasting the ore in one part of said chamber in the presence of air so as to oxidize the components of same, means for collecting and withdrawing from the kiln chamber the major portion of one of the components produced by oxidizing the ore, means for causing said ore to be subsequently acted upon by fire gases within the chamber, and means for preventing the admixture in the kiln chamber of the fire gases and the gases that are extracted from the ore during the first stage of the process. v

5. An ore roasting kiln, comprising vva kiln chamber that is adapted to receive ore, means for introducing fire gases into the rear portion of said chamber so as to cause the ore in this portion of the chamber to be roasted by the heat which radiates from the lire gases within the chamber, means outside of said chamber for transferring part of the heat from said fire gases to air, means for supplying this heated air to the front portion of the chamber to oxidize the ore therein, and means for preventing the roast gases in the front portion of said kiln chamber from mingling with t-he fire gases Within the rear portion of said chamber.

6. An ore roasting kiln, comprising a kiln chamber that is adapted to receive ore, means for introducing fire gases into the rear portion of said chamber so as to cause the ore in this portion of the chamber to be roasted by the heat which radiates from the fire gases within the chamber, means out-side of said chamber for transferring part of the heat from said fire gases to air, means for supplying this heated air to the front portion of the chamber to oxidize the ore therein, and means for withdrawing from the front portion of the kiln chamber the gases that are produced by oxidizing the ore therein.

7. In an ore roasting kiln, a kiln chamber through which ore is conveyed, means for supplying fire gases to the rear portion of said chamber, means for extracting said ire gases from the rear portion of said chamber, and means for causing air to absorb the heat from said extracted fire gases and flow into the remaining or front portion of said chamber so as to oxidize the ore therein.

8. An ore roasting kiln, comprising a kiln chamber through which ore is conveyed, burners Vin the rear portion of said chamber which supply lire gases thereto, fire iues communicating with outlet ports for said fire gases arranged intermediate the ends of said kiln chamber, said fire flues being located over the kiln chamber, means for causing the lire gases to travel outwardly through said flues, and means for causing fresh air to travel adjacent said flues and ab sorb heat from same and then pass into the front portion of the kiln chamber so as to oxidize the ore therein.

9. In an ore roasting kiln, a kiln chamber through which ore is conveyed, burners in the rear port-ion of said chamber for supplying fire gases thereto, a recuperator consisting of lire flues and air ducts arranged adjacent each other, said fire flues communicating with outlet ports in the kiln chamber through which the fire gases from the rear part of the kiln chamber escape and said air ducts communicating with inlet ports through which fresh air is admitted to the front portion of the kiln chamber, and means for inducing drafts through said lire flues and air ducts. j

10. An ore roasting kiln, comprising a kiln chamber through which ore is conveyed, burners arranged in the rear portion of said chamber for supplying fire gases thereto, a recuperator arranged over this portion of the kiln chamber and consisting of parallel lire flues and air ducts arranged in proximity to each other, the roof of the kiln chamber being provided with outlet ports for the fire gases that communicate with said fire flues and also inlet ports for the fresh air that communicateswith said air ducts, means communicating with the opposite ends of said fire flues for inducing a draft through same, and a suction-producing device that communicates with the charging end of said kiln chamber.

11. In a roasting kiln, a kiln chamber having inlet ports for fire gases and for air, a collective outlet port for the fire gases arranged about halfway between the ends of said chamber, inlet openings for air arranged near said collective outlet port, and an outlet port for sulfur gases adjacent the charging end of said chamber, each of said outlet ports communicating with separate exhaust or suction-producing devices.

12. In a roasting kiln, a kiln chamber having inlet ports for fire gases to part of the kiln chamber, an air duct which communicates at one end with the atmosphere and at its other end with the remaining part of said kiln chamber, and an outlet port for said fire gases arranged some distance away from the point at which said air duct communicates with said chamber. Y

13. In a roasting kiln, a kiln chamberhaving inlet ports for gases and for air, a recuperator located over the rear part of said chamber and having fire flues and air ducts arranged adjacent each other, the fire flues connecting at one end with the kiln chamber at a point intermediate the ends of same and at the other end with a suctionproducing device, and the air duct-s of said recuperator communicating at one end with the atmosphere and at the other end with the front part of the kiln chamber at a point between the charging end of the kiln chamber and the point where said fire llues connect with said chamber.

14. In a roasting kiln, a recuperator located over a part of the kiln chamber that is heated and having lire flues and air ducts arranged adjacent each other, the fire lues connecting the heated part of the kiln chamber with a chimney and the air ducts connecting the atmosphere with a different part of the kiln chamber which is relatively cooler and through this chamber with an eX- haust fan or similar device.

15. In a roasting kiln, a kiln chamber having curbs or ledges projecting from the side walls toward the hearth, and burners arranged in said curbs or ledges.

16. In a roasting kiln, a kiln chamber having curbs or ledges arranged adjacent the sides of the hearth so as to hold the material away from the side walls of the kiln chamber, and burner ports arranged in said ledges that communicate with a fuel Hue.

17. In a roasting kiln, a stirrer comprising a rotatable shaft, a plurality of members adjustably mounted on said shaft and each provided with radially projecting wings that engage the material on the hearth of the kiln, said members being adapted to be rotated relatively to the shaft and to each other so as to arrange the wings on one member at a different angle with relation to the wings of an adjacent member, and a device for securing all of said members to the shaft.

18. A stirrer for a roasting kiln, comprising a rotatable shaft, a plurality of members mounted on said shaft and each consisting of a hub provided with a plurality of radially projecting wings, and a key-bar for securing all of said members to said shaft, said key-bar and members being so constructed that the members can be a'djusted so as to arrange the wings of onev member at a different angle with relation to the wings of an adjacent member.

19. An annular roasting kiln, comprising a segmental-shaped kiln chamber, means for conveying material through said chamber, means for supplying fire gases to the rear portion of said chamber, a recuperator arranged over the roof of the rear portion of said chamber and consisting of fire flues and air ducts arranged adjacent each other, outlet ports inthe roof of said chamber that communicate with said fire llues, and inlet ports arranged intermediate said outlet ports and the charging end of said chamber for establishing communication between said air ducts and the front portion of the kiln chamber, an exhausting device communicating with the outer ends of said lire lues, and an exhausting device communicating with the charging end of said kiln chamber.

20. An annular ore roasting kiln, comprising a segmental-shaped kiln chamber. means for feeding -ore over the hearth of said chamber, a fuel flue arranged under a portion of said hearth, burners communicating with said 'fuel time for supplying lire gases to the rear portion of said kiln chamber, a recuperator consisting of discharging fire flues that communicate With the rear portion of said chamber, and air inlet ports that communicate with the front portion of said chamber, a suction-producing device communicating with said fire flues, and a suction-producing device that communicates With the charging end of said kiln chamber.

21. In an annular roasting kiln, a substantially annular or segmental-shaped kiln chamber provided in one of its side Walls with a horizontally disposed slot, an annular-shaped shield plate for closing said slot, a stirring apparatus comprising a member that projects through said shield plate into said kiln chamber, and a plurality of friction-reducing devices mounted in stationary bearings and operating to support said shield plate.

22. In an annular roasting kiln, a substantially annular or segmental-shaped kiln chamber provided in its inner Wall with a horizontally disposed slot, an annularshaped shield plate for closing said slot, a stirring apparatus comprising a member that projects through said shield plate into said kiln chamber, a plurality of rollers mounted in stationary bearings adjacent the inner Wall of said kiln chamber for supporting said shield plate, a rotatable bearing member arranged adjacent the center of the kiln, and braces for connecting the shield plate to said bearing member.

23. In an annular roasting kiln, a sub.- stantially annular' or segmental-shaped kiln chamber provided in its inner Wall With a horizontally disposed slot, an annularshaped shield plate for closing said slot, a plurality of frictionreducing devices mounted in stationary bearings arranged adjacent the inner Wall of said kiln chamber for supporting said shield plate, a rotatable bearing arranged adjacent the center of the kiln and provided with radially disposed braces Which are connected to said shield plate, a stirrer arranged in said kiln chamber, la shaft for said stirrer supported by said shield plate and rotatable bearing,

and means for moving said shield plate in a circular path.

24. A roasting kiln, comprising a kiln chamber, means for introducing iire into the rear portion of said kiln chamber, a fire flue, an air duct or flue arranged on top of the roof of said kiln chamber so as to cause the air which passes through same to become heated, means for permitting the air in said air duct to enter the front por tion of the kiln chamber, and means for creating a draft or suction in the front portion of the kiln chamber.

25. An ore roasting kiln, comprising a kiln chamber, means for causing fire gases to travel through a port-ion of said chamber and then escape therefrom so as to heat the orc in this portion of the kiln chamber', means for utilizing heat from the outgoing fire gases for heating air which is supplied to a different portion of the kiln chamber that contains fresh ore, this heated air acting to oxidize the fresh ore and produce heat in this portion of the kiln chamber, means for collecting the gases produced by the oxidation of the ore, and means for moving the ore through the kiln chamber so as to cause the oxidized ore to be subsequently heated by the fire gases first referred to.

26. An ore roasting kiln comprising a kiln chamber, means for causing ore in a portion of said kiln chamber to be acted upon directly by artificial heat Within said chamber, a flue through Which the spent heat can escape, means arranged outside of the kiln chamber for transferring part of this spent heat to air and supplying this heated air to ore in the remaining portion of the kiln chamber so as to oXidize the ore and produce heat therein, means for Withdrawing the gases produced by the oxidation of said ore, and means for moving the ore through said kiln chamber.

In testimony whereof I hereunto aiiix my signature in the presence of two Witnesses, this sixth day of January 1911.

lVnLLs L. CHURCH, y GEORGE BAKEWELL.

Copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents,

Washington, D. C.

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