US1912455A

US1912455A - Method and apparatus for roasting ores

Info

Publication number: US1912455A
Application number: US473837A
Authority: US
Inventors: Harold O C Ingraham
Original assignee: General Chemical Corp
Current assignee: General Chemical Corp
Priority date: 1930-08-08
Filing date: 1930-08-08
Publication date: 1933-06-06
Anticipated expiration: 1950-06-06

Description

.arts of the Patented June 6, y

UNITED STATES momo. or meneur, 'or Gmuwrcn. 4 or New roux, n. Y.; a couronnes or Nrw You CHEMICAL GOIIPANY,

PATENT .ol-FICE nn'rnoumn minnares 7non. noname onEs appumm ma una s, mo. serial m. um?.

invention relates to a method and apparatus for roasting ores', and is particulary 1K directed to a m od and apparatus for t e roastingof those ores whic require the employment of extraneous heat to effect the roasting operation.

Heretofore, furnaces employed for the roasting of ores such as zinc blend which require t satisfactorily complete the roasting thereof have been \customarily equipped with suitable mules associated directly with the roasting hearths. Such furnaces employing muilied hearths have been heated by the burning of natural gas of other suitable fuel, and in many installations,` it has been common ractice to utilize producer gas as a source of y eat. InV the former instance, the utilization of natural gas or other hydrocarbon fuel is a direct charge against the roasting operation. In plants vvwhere the latter method vis employed, it is necessa to rovide producer gas generators anassocia apparatus. The

necessity for suc equipment increasesthe cost of roasting not only in the capital investment, but in `maintenance after installation.

This invention contemplates/'the combus;

gas preferably preheated, in the muilies` such roasting furnaces, theutilization ofthe heat generated bv the combustion of the sulfur to supply the extraneous heat necessary for eiciently effectingl the roasting operation, and the subsequent employment in the sulfurous gases formed by the combustion` of the sulfur in the muilles.

By employing the combustion of sulfur as the source of extraneous heat ,in accordancel with the present invention, it becomes posslble tosupply the extra heat required at a muchlower operating .cost than heretofore since the sulfur dioxide gas reduced is in itself awaluable product and] may be,used for example in the production of sulfuric acid e application of extraneous heetste b the contact process, or in accordance with t e preferred method of practicing my invention,` maybe mixed with the sulfur dioxide ugas-stream produced by the roasting of the s fide ore undergoing roasting in the furnace in which the sulfur 1s be' burnedto supply the extraneous heat requi AB thus mixlng the two steams of sulfur dioxi e gas the volume of sulfur dioxide produced is of course greatly augmented and in addition is ordinarily enriched in SO, content ly reason of the fact that the sulfur dioxi e gas from the combustion of the sulfur will ordinarily'be richer in SO, content than the gas from the ore roasting'. A further advanta e of the combustion of sulfur to provide t e extraneous heat required is that the danger of leaka of air or inert products of combustion romthe heatin iues into the roaster hearths, or leakage of S5, gas from the roast- -inghearths into the muilles, withattendant d tion of the roaster gas o r loss of valuable SO, into the waste products of combustion as necessarily occurs when carbonaeeous fuels are used to supply the extraneous heat, is entirely obviated when sulfur is burned in th muilies because the sulfur dioxide gas produced is of substantially the same com osition as the 4sulfur dioxide gas produced m the ore 4roastin .A vOperating ,and maintenance' costs are t us reduced since the necessity heretofore of constructing and maintain 22 of Fig. 1. n

The numeral 10 indicates orally a ver tically disposed multi-heart roasting furnace of the general type known as the Herreshol roaster. The furnace includes a plurality of superposed

roasting hearths

11, 12, 13, 14 and 15. The top of the roasting chamber is closed oi from the atmosphere by the drying deck 16, andthe bottom of the roasting chamber is formed by the cinder floor 17. The roasting hearths each have associated therewith the

mailles

18, 19, 20, 21 and 22. The top and bottom of each muille are formed respectively by the iloor of the next u per roasting hearth, and the arched top o the lower roastin chamber. The outer vertical walls of the urnace and the circular members 23 constitute the side walls of the

inuiiles

18, and 22, and the vertical walls of the

muilies

21 and 19 are formed by the circular brick-

work

24 and 25. As is usual in roast- 31. The sha ing furnaces of the kind described, alternate hearths are arranged with peripheral and central openings to facilitate the passage of the ore through the roaster from top to bottom.

The shaft indicated generally at 26 is rotatably supported at its lower end by means not shown, and is arranged to revolve in the opening 27 in the lower arched wall 28 and in the upper bearing 29 which is roperly secured a ainst lateral movement Ey mem# bers not s own extending a'cross the top of the furnace. The shaft 26 includes the cenf tral air passa e 30, and the annular passage 26 has associated therewith a suitable number of rabble arms indicated generally at 32, 33, 34, and 35. Each rabble arm is constructed in a manner known in the art, so that air under suitable pressure-in the central passage 30 is conducted to the end of each rabble arm by a passage 36, and then returned to the main annular passage 31 in the shaft 26 through a passage as indicated at 37 on the rabble arm 32. Babble

arms

32, 33 and 34 are each rovided with the customary plows or teet arranged to work the ore toward the vertical passages adjacent the periphery of the furnace as theshaft 26 rotates and the roastin of` the ore proceeds.; The lowson the rabb e arms associated with heart 11, 13 and 15 are op lositely arranged so as to work the ore towa the central passages through the hearths of the furnace as the shaft 26 rotates: Y

The annular passage 31 in the shaft 26 is connected at its upper end to a cross conduit 40 thro h a series of slots indicated at 41. The con uit 40 is securely supported on the top of the furnace shell by members not shown. The ends of the conduit 40 open into the circular bustle 42 restin on the upper end of the furnace wall. The ustle 42 1s in turn connected` to a series 4of assages or ducts 43 in the vertical walls of t e furnace, which pa r s terminate at their lower ends in a bustle 44 constructed about the lower end of the furnace surrounding the muille 18.

'where interrupte yother cross members not shown which serve .feed hoppers 62. The hop) The conduit 40 is provided with an outlet 45 having a suitable control damper 46.

The ore hopper 50 is attached toand supported by a bracket 51 which is suitably secured and held in the position indicated by cross members not shown. The lower end of the hopper 50 is provided with a circular sleeve outlet 52 which is verticall adjustable with respect to the lower end o the holpper'and a horizontal shelf 53 formed by t e orizontal portion of the bracket 51. The wiper blade 54 is fixed to and rotates with the shaft 26. It will be understood that the space above the d ing deck 16 is open except by the conduit 40, and

to support the bearing 29, bracket 51, conduit 40, and the hopper 50.

A rabble arm 60, constructed similarly to the other rabble arms, is attached to thel upper end of the shaft 26 and includes plows 61 which, on rotation of the shaft, gradually A work the ore outwardly over the totp of the drying deck and into the secon a ore ers 62 jre each `provided with an adjusta e sleeve' 63, the vertical osition of which is con/trolled and regulated) by the stem 64y threaded into and supported by suitable bracket attached to the furnace wall and not shown inthe drawing. It will be understood that the rotation of the stems 64 changes the dsition vertically of the lower end of the's eleves 63 with respect to the surface of the hearth 15. Wiper members 65 are connected to the ends of each of the rabble arms 35 and are arranged to pass under the ends of the sleeves 63 on each rotation of the shaft.

The construction of the muille 19 is shown in Fig. 2. The circular muille is provided with a radial baie 66 which extends vertically from the upper surface of the arch 67 of the lower roasting chamber u wardlv to the under side of the hearth 12. e baille 68 is similarly arranged except that the up er half of the baiHe is c ut oil and its upper e` ge does not abut the lower side of the hearth 12. The baille 69 pro'ects downwardly fromthe under side of t e hearth 12, its lower edge terminating approximately mid-way between the hearth 12 and the arch 67 as clearly shown lll in Fig. 1. In the present embodiment of the the necessary air for the burning and volatilization of sulfur therein may be supplied by any suitable means and I have not described the sublimer in detail since suitable subllmers are known in the art. The vapor chamber of the sublimer is connected to the inlet 71 of the muille 18 through a conduit 72. As shown in Fig. 1, the end of the pipe 72 passes into and through the bustle 44. At the inlet 71 air from the bustle 44 and gas from the sublimer 70 are mixed and introduced into the muflle 18. After passing completely around the muilie 18 the gases leave through the outlet pipe and are introduced into the next higher muilie 19 through the inlet 76. In a similar manner the gases circulate through the muflie 19 and leave the muille throu h the exit pipe 77, and are thence lead into t e nluiiie 20 through the inlet T8. After passage of the gas through the mutile 20, the gases are discharged from the furnace through the outlet pipe 79 and are conducted to suitable conversion apparatus.

The operation of the improved method and apparatus is as follows:

Sulfde ore such as zinc blend is fed into the hopper 50 by any suitable mechanism. By proper adjustment of the sleeve 52, a pile of ore is maintained on the horizontal shelf 53. On each revolution of the shaft, a predetermined quantity of ore is swept oil' the shelf 53 by the wiper 54 and dropped onto the drying deck 16. On further rotation of the shaft 26, the ore is gradually worked outwardly over the drying deck and into the feed hoppers 62. The ore drops from the hoppers 62 through the sleeves 63 to the surface of the hearth 15, andis deposited thereon in small piles similar to those formed on the shelf 53 under the primary hopper 50. On rotation of the shaft 26, the Wipers 65 on the ends of the arms 35 sweep small portions of ore out from under the sleeves 63, at which time such portions are picked up by the plows of the rabble arm 35 and are gradually worked toward the center of the hearth 15. As the roasting of sulfide ores in furnaces of the type described is well understood, further detailed mention of the roasting operation per se is unnecessary. It is suilicient to say that the gases formed by the roasting of sulfides contain sulfur dioxide as the principal useful'constituent. The gaseous products are drawn off from the furnace through the outlet indicated at 10'. After theore has passed successively over the roasting hearths, itis discharged from the furnace through the i cinder outlet 17 During the roasting operation, air under suitable pressure is introduced into the center conduit 30 of the shaft 26, and, in the manner well known in the art, iscirculated through the rabble arms and, back into the annular passage 31 of the shaft 26. It will 4be understood that such circulation of air bustle 42. The heated air then passes down- Wardly through the several vertical passages 43 and is thus introduced into the bustle 44 surrounding the lower muflie 18. It will be apparent that as the air passes downwardly through the ducts 43, its temperature Will be further increased by the amount of heat extracted from the Walls of the furnace. In the event that more air is needed to effect proper cooling of the rabble mechanism than is necessary for the combustion of the gases in the mufiles as hereinafter described. the surplus heated air can be discharged from the conduit 40 through the. outlet 45 by suitable manipulation of the damper 46.

As mentioned, according to the preferred mode of operation of the invention, the sublimcr 70 is of the type in which sufficient quantities of air are introduced to effect combustion of a small quantityr of the sulfur and a vaporization of a large amount of sulfur by the heat generated bv the combustion of the smaller portion. The resulting gas mixture rich in sulfur vapor is introduced into the muile 18 through the muille inlet 71. At the inlet, the gases from the sublmer are mixed with preheated air from the bustle 44 to effect a complete combustion of the sulfur in the gases, during the passage of the gas mixture through the several muilles of the shaft furnace. 0n admission of the preheated air and sulfur containing gases, combustion of the resulting gas mixture is initiated in the mullle 18 and proceeds as the mixture is circulated through the mnlile with the consequent goneration of large quantities of heat. The combustion of thesulfur and the generation of heat continues as the gas mixture passes successively through the mnilles 18. 19 and 20. B v the time the combustion of the sulfur is complete. as will be the condition after the gas passes through the muflle 20. the resulting gas. containing sulfur dioxide, is discharged from the roaster through the outlet 79, and may be conducted to a contact sulfuric acid plant designed for the use of brimstone burner gas. It will be noted that the burning gas mixture enters each muile on one side of a full baille 66 and passes completely around the circumference of the furnace and is discharged from the maille on the opposite side of the full baille. Thus the full benefit of the heating effect of the burning "gases is obtained and imparted to the roasting ores on the adjacent hearth.

Although the present invention is applicable to the roasting of all types of sulfide ores in which extraneous heat is required, the invention particularly contemplates the roasting of zinc sulfide, for the efficient roasting of which a temperature of about 1,600O F. should be maintained in the furnace, partielllarly on the lower hearths thereof. By the use of preheated air, it is possible to maintain temperatures of QOOLQQOO F. in the

inutiles

18, 19 and 20, with the consequent maintenance of a temperature of at least 160()O F. on the roasting hearths of the furnace.

It will be understood that instead of passing the sulfur gases througli the

muiiies

18, 19 and 20 in series as described, it is possible to divide the gas stream from the sublimer into two or more portions and burn part of the gas in each mufile. In some instances, it may also be desirable to conduct the burning of sulfur gases in a greater or lesser number of muflies than described in the specific embodiment of the invention set forth.`

A modified mode of operation of the invention contemplates the utilization of the gases from the roaster, discharged from the outlet 10', and the gases discharged from the muiiie through the outlet conduit 79 in separate apparatus. This procedure may be adopted where for any reason it is not desired to mix the gases from the outlet 79 with the gases issuing from the roaster through the outlet 10.

I claim: i

1. The process of roasting sulfide ores requiring the application of extraneous heat to effect an efficient roasting thereof which comprises i1 itiating the roasting operation, generating a sulfur containing gas mixture, adding a heated combustion supporting gas to such mixture, and burning the resulting gas mixture in indirect heat exchange relation with the ore undergoing roasting, whereby the heat generated by the-j; burning of the sulfur furnishes extraneous heat for the roasting of the ores.

2. The process of roasting sulfide ores requiring the application of extraneous heat to effect an efficient roasting thereof which comprises initiating the roasting operation, generating a sulfur containing gas mixture, preheating a combustion supporting gas, adding such preheated gas to the/*sulfur containing gas mixture, and burning the resulting gas mixture in indirect heat exchange relation'with the ores undergoing roasting, whereby the heat generated by the burning of the sulfur furnishes extraneous heat for the roasting of the ores.

3. The process of roasting sulfide ores requiring the application of extraneous heat to effect an efficient roasting thereof which comprises initiating the roasting operation, generating a sulfur containing gas mixture, circulating a combustion supporting gas in heat exchange relation with the ores undergoing the roasting operation, adding such preheated gas to the sulfur containing gas mixture, and burning the resulting gas mixture in indirect heat exchange relation with the ores undergoing roasting, whereby the heat generated by the burning of the sulfur furnishes extraneous heat for the roasting of the ore.

4. The process of roasting a zinc sulfide ore which comprises initiating the roasting operation, and burning sulfur in indirect heat exchange relation with the ore undergoing roasting, whereby the heat generated by the burning of the sulfur furnishes extraneous heat for the roasting of the ore.

5. The process of roasting a zinc sulfide ore which comprises initiating the roasting operation, generating a sullfur containing gas mixture, and burning sulfur in such mixture in indirect heat exchange relation with the ore undergoin roasting, whereby the heat generated by t e burning of the sulfur furnishes extraneous heat for the roasting of the ore.

6. The process of roasting a zinc sulfide ore which comprises initiating the roasting operation, generating a sulfur containing gas mixture, adding a heated combustion supporting gas to such mixture, and burning the resulting gas mixture in indirect heat exchange relation with the ore undergoing roasting, whereby the heat generated by the burning of the sulfur furnishes extraneous heat for the roastin of the ore.

7. The process o roastin a zinc sulfide ore which comprises initiating the roasting operation, generating a sulfur containing gas mixture, preheating a combustion supporting gas, adding such preheated gas to the su fur containing gas mixture, and burning the resulting as mixture in indirect heat exchange relation with the ore undergoing roasting, whereby the heat generated by the burning of the sulfur furnishes extraneous heat for the roastin of the ore.

8. The process o roasting a zinc sulfide ore which comprises initiating the roasting operation, generating a sulfur containing gas mixture, circulating a combustion supporting gas in heat exchange relation with the ore undergoing the roasting operation, adding such preheated gas to the sulfur containing gas mixture, and burning the resulting gas mixture in indirect heat exchange relation with the ore undergoing roasting, Whereby the heat generated by the burning of the sulfur furnishes extraneous heat for the roasting of the ore.

9. The process of roasting sulfide ores re quiring the application of extraneous heat to effect an eiiicient roasting thereof which comrises initiating the roasting operation, and urning sulfur in indirect heat exchange relation with the ores under oingl roasting, whereby the lieat generated y t e burning of the sulfur furnishes extraneous heat for the roasting of the ores.

10. Apparatus for roasting ores comprising a furnace including a roasting chamber, means for feeding ore into said chamber, wherein the roasting of such ore is initiated, a sulfur sublimer for generating a sulfur containing gas mixture, a gas connection between the sublimer and the roasting chamber for introducing said mixture into the furnace and initiating the burning of such gas mixture therein, so that the heat generated by the burning of the sulfur furnishes extraneous heat for the roasting of the ore.

11. Apparatus for roasting ores comprising a roasting hearth, a muilie associated therewith, means for generating a sulfur containing gas mixture, and means for burning sulfur in such mixture in the muie.

12. Apparatus for roasting ores comprising a roasting hearth, a muiile associated therewith, means for generating a sulfurcontaining gas mixture, means for preheating a combustion supporting gas, means for mixing the iirst mentioned gas and the preheated combustion supporting gas, .and means for introducing the resulting gas mixture into the muiile and initiating the burning of such gas mixture therein.

13. Apparatus for roasting ores comprising a roasting hearth, a muie associated therewith, means for generating a sulfur containing gas mixture, means associated with the hearth for preheating a combustion supporting gas, means for mixing the first mentioned gas and the preheated combustion supporting gas, and means for introducing the resulting gas mixture into the muilie and initiating the burning of such gas mixture therein.

14. Apparatus for roasting ores comprising a multi-hearth roasting furnace, a muiile associated with each hearth, means for generating a sulfur containing gasmixture, means for introducing the gas mixture into one muflie and initiating the burning of the gas mixture therein, and means for circulating the burning gas through another mulile.

15. Apparatus for roasting ores comprising a multi-hearth roastin furnace, a muiile as sociated with each heart means for generating a sulfur containing gas mixture, means for preheating a combustion supporting gas, means for mixing the first mentioned gas and the preheated combustion supporting gas, means or introducing the resulting gas mixture into one muiiie and initiating the burning of such gas mixture therein, and means for circulating the burning gas through another muiile.

16. Ap aratus for roastin ores comprising a mu ti-hearth roasting urnace, a muie associated with each hearth, means for generating a sulfur containing gas mixture, means associated with a hearth for preheating a combustion sup orting gas, means for mixing the first mentioned gas and the preheated combustion supporting gas, means for introducing the resulting gas mixture into one muiiie and initiating the burning of such gas mixture therein, and means for circulating the burning gas through another muie.

17. Apparatus for roasting ores comprising a multi-hearth roasting furnace, a muiile and rabbling mechanism associated with each hearth, means for generating a sulfur containing gas mixture, means for circulating a combustion supporting gas through the rabbling mechanism, whereby such mechanism is cooled and the gas preheated, means for mixing the first mentioned gas and the preheated combustion supporting gas, means for introducing the resulting gas mixture therein, and means for circulating the burning gas through another muiiie.

18. Apparatus for roasting ores comprising a plurality of superposed` roasting hearths and associated supporting walls, a mulile associated with each hearth, rabbling mechanism for moving the roasting ores suc- Vcessively over the several hearth, means for `circulating a combustion supporting gas through the rabbling mechanism whereby the mechanism is cooled and the gas preheated, a bustle adjacent a inutile, means for conducting the preheated gas to the bustle including passages arranged in the wall of the furnace, a sulfur sublimer, a connection between the sublimer and the bustle, means for introducing a mixture of the gas from the sublimer and the preheated combustion supporting gas from the bustle into the adjacent mule, whereby the combustion of the as mixture is initiated, means for circulatu ing the burning gas through a plurality of muiiies, and means for withdrawing the gas from the last muiiie of the series, whereby the sulfur in the gas mixture burned in the muiiies is converted to sulfur dioxide and the heat of combustion imparted to the roasting ores in the associated hearths.

19. The process of roasting suliide ores requiring the application of extraneous heat to effect an efficient roasting thereof which comprises initiating the roasting operation, generating a sulfur containing gas mixture, and burning sulfur in such mixture in indirect heat exchange relation with the ores undergoin roasting, whereby the heat generated by t e burning of the sulfur furnishes extraneous heat for the roasting of the ores.

20. The process of roasting sulfides requirin the application of extraneous heat to e ect eiicient roasting thereof which comprises initiating the roasting operation in a 13 lll roasting zone, separutelfy m1xture rich 1n free sul u Lemus generating a. gas r vapor at a pomt l and t erein burning sulfur vapor o such mixture in conj unctlon with the roasting o eration so that the heat generated by t e burning of the sulfur furnishes extraneous heat for the roastn o ration. l0 h Irwitness whereo have hereunto set my HAROLD O.` C. INGRAHAM.

CERTIFICATE OF CORRECTION.

Patent No. 1,912,455. June 6, 1933.

HAROLD O. C. INGRAHAM.

It ia hereby certified that error appears in the printed specification of the above nimbered pateut'requiring'correctiou as follows: Page I, liuc 15, for "of" second occurrence read "or"; page 5, line 88, claim 17p` after "mixture" insert the ywords 'intoT one muffle and initiating the burning of 4auch gas mixture"; and line 96, claim I8, for "hearth" read "heartha"; aud that the eaid Letters Patent should be read with these corrections therein that the same may conform to the'reconl of the case in the Patent Office.

Signed and sealed this 15th day of August, A. D. 1933.

M. J. Moore.

(Seal) t Acting Conlnissioner of Patente.