US837576A - Furnace for roasting, &c. - Google Patents

Description

No. 837,576. PATENTBD DEG. 4, 1906. A. V. LBGGO.

FURNACE POR ROASTING, &o.

APPLICATION FILED SEPT.6.1905.

12 SHEETS-SHEET 1 @15M- lig? 0 A. V. LEGGO.

PATENTED DEC. 4, 1906.

PURNAGE FOR ROASTING, &o.

APPLICATION FILED SEPT. 6.1905.

12 SHBETSTSHBET 2.

27206572 for No. 837,576. PATENTBD DBO. 4, i906. A. V.LEGG0.

PURNAGE POR RASTING, 46m.

APPLICATION FILED SEPT. 6. 1905.

12 SHEETS-SHEET 3.

No. 837,576. y

A. V. LBGGO.

FURNACE POR ROASTING, &0.

APPLIOATIDN FILED SEPT. 6.1905.

' 12 SHEETS-SHEET 4.

PATENTED DEC. 4, 1906.

No. 837,576. u PATENTED DBC. 4, 190e. A. v. LEGGO.

FURNACE POR ROASTING, 6m.

APPLICATION FILED SEPT. 6.1905.

12 SHEETS-SHEET 5.

No. 837,576. PATENTED DB0. 4, 1906.

A. V. LBGG0. s

PURNACB PoR ROASTING, aw.

APPLICATION FILED SEPT. .1905.

6 I2 SHEETS-SHBBT 6.

?? i @fm No. 837,576. PATENTED DBG. 4, 1.906. A. V. LEGGO.

FURNACE FOR RDASTING, 6:0.

APPLIUATION FILED SEPT. 6.1905.

12 SHEETS-SHEET '1.

"'/I//l//IIA vllll....,

Elm-- W 4" (2g @aww M fifty;

No. 837,576. PATENTED DEGML 1906.

A. v. LBGGQ.

FURNACE FOR ROASTING, 6m.

APPLIOATION FILED SEPT. e; 1905.

' 12 SHEETS-SHEET 8.

wwf/z* l y A l No. 837576. PATBNTED DBC. 4, 1906.

A. v. LEGGO. FURNACE For; RoAsTING, dw.

APFLIOTION FILED SEPT. 6.1905. 12 SHEETS- SHEET g- No. 837,576. l PATENTBD DEG. 4, 1906. A. v. LEGGO.

PURNACE POR ROASTING, zo.

APPLICATION FILED SEPT. 6. 1905.

12 SHEETS-SHEET 10.

/ Wwf/za i* 0 10.837,576. PATENTED 1350.4, 1906. Y

A. v. LEGGO.

FURNACE FOR ROASTING, 65o.

APPLICATION FILED SEPT. 6,1905.

12 SHBBTS-SHEET 11.

PATBNTBD DBG. 4, 15906.

12 s'HEgTs-SHBBT f2.

A. V. LEGGO.

PURNAGE FOR ROASTING, &0. APPLIOATION FILED SEPT. 6,1905.

UNITED STATES PATENT OFFICE.

ARTHUR VICTOR LEGGO, OF BALLARAT, VICTORIA,- AUSTRALIA.

FURNAOE Fon'noAsTlNe., ao.

To 'all 11i/tom, it may coitcrnli.

Be it known that I, ARTHUR VICTOR LEGGO', a subject of the hing of Great Britam, residmg at- Pendeen, Dawson street, Ballarat, m the State of Victoria and Commonwealth of Australia, have invented an Improved Furnace for RoastmgDesulfur1z lng, hloridizmg, Dehydratmg, or Drying Orcs and other Substances, of which the following 1s a speclficatlon.

My invention has been devised 1n order to provlde a furnace forroast'mg, desulfurizmg,

chloridizing, dehydrating, or dr ling ores or` other substances which shall A e of Great capacity, durability, and eiliciency, While at the same time the expense of'constructing, maintaining, and operating it will be found to be-much less than with any other furnace at present in use.V Moreover, with my furnace by the alteration, exchange, and adjustment of its various parts it can be made to adapt itself to the particular conditions necessary to any kind of roast.

Many of the im rovements hereinafter described are suitable and intended only to meet the conditions eculiar to roastincr certain ores'or certain llinds of roast, While for another dissimilar ore or kind of roast the same improvements are quite unsuitable and the substitution of other im rovements to suit the altered conditions an requirements.

are provided for, and it will be obvious that such alterations will in some cases necessitate the relative positions of ,different parts being suitably altered.

In order that those skilled in the art mayv more readil 'understand my invention, 1t may be wel to set forth some of the disadvantages hitherto experienced in connection with existing roasting-furnaces and Which disadvantages Will be found to be either nonexistent in my furnace or to have been minimized to a great extent.

One of the great disadvanta es of existing furnaces Vhaving superimpose hearths has beenpthe great amount of iue-dustproduced by droppingV the ore from one heart-h to another, said dust being Vcarried off by the draft through the furnace. Moreover, their design and equipment have been such as to limit their capacity, as the Whole of the ore has had to pass over all of theirhearths, and, further, the breaking of the contact of the ore particles at each hearth prevents the conduction of the heat from the hotter particles to the cooler ones at these points.

Specification of Letters Patent. Application filed September 6.1905. Serial No. 277,344.

Patented Dec. 4, 1906.

The disadvantages of sinffle-hearth furnaces are their great cost of construction, their great loss of heat by radiation, and the larve area of Hoor-space necessary for them, with the consequent heavy cost of operating them. A

In all roasting-furnaces there is great loss of heat in the waste gases leaving them and also inthe roasted ore discharged from them, and Where fuel economyis a matter of great moment I provide means, hereinafter described, for utilizing said losses of heat in operating the furnace.

M f furnace consists vof a series of horizontal or s ightly-inclined hearths, one above and each mdependent of the other, each hearth preferably having a separate fire-box at its discharge end, and when cold ores-that is, ores 'containing a low ercentage of sulfurare to be roasted sup iementary or auxiliary fire-boxes may be buii) alternately on either side at any oint or points along the length of said heart s. The said hearths are provided Withrabble-arms, by means of which the ore under treatment is conveyed simultaneously along each t onl one side or arranged hearth in the same direction and, preferably,

at the same rate of speed, so that the ore on eachhearth at any given point is at the same sta e 'of desulfurlzation or roast. The ore to e treated is fed from a hopper onto the feed end of each hearth and is passed along the said hearths by means of the rabble-arms, which are tted to vertical shafts Which pass through the center of each hearth of the furnace. Whenthe ore has traversed the Whole length of the hearth, it passes through an o ening in the side thereof and enters a c ute Which conveys it either outside the furnace or to a combined air-.su erheating and roasted-ore-cooling hearth ereinafter called a coolingchamber) situated below thelevel of the bottom hearth and preferably -at one side thereof.

Thecooling-chamber 1s so arranged and constructed as that the air passed over the heated ore in the hottest -part thereof to cool it is on becoming hot passed either tothe combustion-chamobers or roasting-chambers, Where it assists in the combustion of the fuel or oxidation of the ore in the said roastingchambers. s

In lieu of delivering the ore -either outside of thefurnace .or to: the cooling-chamber I prefer, when a sweet roast vis required and a considerable increase in temperature is nec- IOO IOS

essary to attain it, to deliver the ore from each hearth to a finishing-chamber, which is constructed as an extension of the bottom hearth of the furnace, and from said finish- 5 ing-chamber the ore is rabbled to a dischargearms of superimposed hearth-furnaces cool the excessivel expansion and contraction of'. the metal have affected the joint where the arms 'form a junction with the rabble-shaft, and the consequent leakage entering the furnace has been very detrimental to the satisfactory operation of the furnace.. Now by my invention I provide means whereby any leakage from the said joint may be caught in an annular recess surrounding said `joint and directed :from the bottomthereof to apassage which leads to a vertical channel cast integrally into the thickness of the shaft, and

the water may be withdrawn therefrom by means of a tap placed at the bottom and side thereof. Y A

Each rabble-shaft is usually provided with only one rabble-arm above each hearth, which is quite sufficient in roasting many ores. Some ores, however,y on being heated. assume` a sticky consistency, and in roasting such I provide each rabble-shaft with two rabble-arms above each hearth and soposition the teeth or tines on each arm that the ore left stagnant by those on one will be stirred by those on the other and the teeth being thus spaced farther apart on the two arms than they would be on only one more eifectually stir the ore.

The furnacecan be. heated with either solid, liquid,l or gaseous fuel, or, Where it isy available and desirable, with the waste heat from other metallurgical furnaces, and in certain cases the roasting operation jcan be continued when suflicient heat has been enerated without the addition of 'any fuel, w en fire-boxes or combustion-chambers need notbe added, the sulfur of the. ore being sufficient for this urpose. In the drawingshereto annexed have shown the combustionchambers provided With grates for burning solid fuel, but the e uipment for burning liquid or gaseous fuel, re uird at all, would obviously be simpler an more easily arranged. v'

age of sulfur excessive heat is vgenerated in In roasting ores containing a high percentthe earlier stages of the roas'tand fthe fumes produced are very voluminous. To prevent and provide for'these, 1 use means hereinafter described for removing said gases from their respectivehearths at any intermediate point or points in the length of such hearths. Thesemeans also permit of the use of shallow roasting-chambers ofgreatr length, with their consequent economyin construction, and at the same time help to prevent dusting by lessening the amount, and therefore the velocity, of the draft passedoverthose parts of the hearths adjacent to thethroats. Where thesurfur gases of calcination are required for the manufacture of sulfuric acid, sulfite pulp, &c., and it isv necessary to fire the furnace with fuel, the furnace can'be muffled and the roasting-chambers' heated Iexternally in order to avoid the'dilution of said calcination gases by thegasesy of: combustion' of the fuel.l Such indirect method of firing, however, sometimes prevents the attain-.- ment of a sufficiently high 7temperature to oxidize the last remaining portion ofthe sulfur in the ore when a sweet roast isdesired# as, for instance, in roasting zincblende when it is desiredto utilize the sulfur in the ore for making sulfuric acid, &c., and at the same time the roasted orelis required sweet to suit the after metallurgical operations lon it. In 9 5 such a case yI eliminate nearly all the sulfur from the ore in the muffled chambers, util-. izing said sulfur asaforesaid, and then :immediately pass the ore onto a direct-fired hearth to finish the operation, the direct firing ofl this hearth allowing of the attainment of a sufficientlyl high temperature' for this pur- 4 ose. v VIn the drawings hereto annexed thevsa'me reference-numerals.referto the sameA parts wherever they occur.

Referring to the drawings, Figure lisa longitudinal ,sectionall elevation of the furnace on'thev line a a'Fi;g. 2: fFi 2 is'aJ sectional plan'of the 'furnaceon the ine bb, Fig. 1. Fig. 3 is a plan in section of the coolingchamber.V vFig. 4 is 'a'sectional elevation ofV IOO IIO

ythe cooling-chamber.' Fig. -5 is a vertical i cross-section on the line d d, Fig. 2L fFig. 6 is a'vertical `cross-section of the combustion 115 and cooling chambers on the line e e, Fi s. 2 and 3. Fig. 7 is a sectional elevation o the feed-hop Aer and chutes depending therefrom. i".`8 is a perspective view o a chute (fitted witishutters vand slide) for conveying izo the ore from the roasting-hearths `to the cooling-chamber orfinishing-chamber ordirect to the outside of the furnace. Fig.' 9 is a vertical cross-section of lire-boxes desi led y to obtain a maximum amount of com ustion-space. Fig. 10 is a sectipnal elevation of a hollow Water-rabble shaftand. arm, also.'

in section; Fig. 11 is a plan of Fig. 10. AFig.

12 is a cross-section of the rabble-arm shown in Fig. 10. Fig. 13 is a cross-section ofthe 13o muffled. Fig. 43 is rabble-shaft on the cbliquely-dotted line ff, Figlll. Fig. 14 is a perspective view 'of that ortion of the water-rabble shaft to which is attached the rabble-arm. Fig. 15 is a sectional elevation of another design of water'- rabble. Fig. 16 is a horizontal cross-section of the rabblie shown in Fig. 15. Fig. 17 is a cross-section of the rabble-arm shown in Figs. 15 and 16. Fig. 18 is a sectional elevation of the water-rabble arm and portion of the rabble-shaft, showing other means for circulating the water. Fig. 19 is a plan in section of an air-rabble arm. Fig. 20 is a plan of a combined water and air rabble arm. Fig. 21 is a sectional elevation of another form of air-rabble shaft and arm. Fig. 22 is a sectional elevation of the rabble-shaft shown in Fig. 21 viewed in the direction of the arrow. Fig. 23 is an inverted plan of a double rabble-arm having oblique teeth. Fig. 241s a cross-section of the air-rabble arm illustrated in Fig. 19. Fig. 25 is .a cross-section of Fig. 20. Fig. 26 is a crosssection of" a water-rabble arm. Fig. 27 shows another method of connecting a flat rabble-arm to the rabble-shaft and means for preventing the escape of fine ore down the openings in the hearths to receive theV said shaft. Fig. 28 is a plan of Fig. 27. Figs. 29 and 30 are elevation and inverted plan, respectively, of another solid rabble-arm with teeth removed. Fig. 31 is a perspective view of a chute `(fitted with disks) for conveying the ore from the hearths to thecooling or finishing chamber or direct to the outside of the furnace. Figs. 32 andBS are elevation and plan, res operating in the inc ined chutes shown in Fig. 31. Fig. 34is a perspective view of portion of a rabble-arm inverted with -teeth attached. Fig. 35 is a perspective view of a front tooth. Fig. 36 is a perspective view of a back tooth. Fi. 37 is a perspective view of anyoblique toot Fig. 38 is a longitudinal sectional elevation of the finishinghearth. Fig. 39 is a longitudinal sectional elevation of portion of the furnace, showing arches over the port-holes and part of the arch lowered. Fig. 40 is a plan of Fig. 39. Fig'. 41 is a sectional view of portion of the furnace, showing the rabble shafts and .arms set at an inclination to the roasting-hearths. Fig. 41A is a cross-section of aportion of the furnace, showing meansfor varying the inclination of the rabble-shafts. Fig. 41B is a plan of portion of Fig. 41A. Fig. 42 is a longitudinal sectional elevation of a modified orrn offurnace 'in which the hearths are a sectional plan on the line g g, Fig. 42. Fig. 44 is a longitudinal sectional elevation of the finishin -hearth as used in connection with the modi ed furnace shown in Fig. 42. Fig. 45 is adiagrammatical view, in side elevation, of thewfurnace, finishing-hearth, and cooling-hearth. Fig.

ectively, of the disks v 46 is a diagrammatical plan view of the same, and Fig. 47 is a diagrammatical plan view of the furnace and coolinghearth. Figs, 1, 2, 3, 4, 5, e, 7, 9, 3S, 39, 4o, 41, 41A, 41", 42,43, and 44 are drawn to a smaller scale than the others.'

1 represents the tangular form and andl strengthened furnace, which is of recis constructed of masonry and bound together with suitable stays, straps, and rods. Said furnacexhas two or morev (four being shown in the drawings) separate and independent superimposed horizontal or inclined hearths 2 3 4 5, which can be of any desired length. At the discharge end of each hearth is when required a separate fire-box'or combustionchamber 6 7 89, though it is obvious one combustion-chamber may be made to.serve two or more hearths. Owing to the greater available space for the top and bottom fireboxes 6 and 9 for heating hearths 2 and 5,

. respectively, andthe greater radiation of heat from said hearths, the said fire-boxes Gland 9v are of greater capacity than those between them-viz., fire- boxes 7 and 8 for heating hearths 3 and 4, respectively. 1() is a chamber to contain any non-conducting material to' prevent radiationlof-heat from thetop. combustion-chamber 6. Passing vertically through the center of the furnace 1 area number of rabble-shafts, (four only of which are shown in the drawings, though any number may be used,) numbered, respectively, l1, 12, 13, and 14, fitted with rabble- arms 15, 16, 17, and 1S. These rabble-arms may be bolt- /ed or keyed to the rabble-shafts and the means of attaching the same shown in the drawings permit by the use of suitable tools of their being renewed or replaced from theoutside of the furnace, thereby obviating the necessity for cooling down the furnace to effect repairs. The rabble-shafts can be driven at any suitable speed and are so arranged that when in motion the paths of the arms on each shaft overlap to a greater or less extent the paths of the arms on the shafts next adjacent. Said shafts 11, 12, 13, and 14 are su ported in foot-ste s (which can be adjusted roth vertically an laterally) or in any other approved manner.. I

y In Fig. 1 the rabble-shafts are shown fitted with only one rabble-arm above each hearth. When required, they can, as hereinbefore stated, have two. Where single-arm rabbles are used, they may work all in one direction or alternately in left and right hand directions, the-latter beingb generally preferred. Where double-arm ra bles are used,Y they must `'work alternately in left and right hand directions, so as to avoid the rabble-arms on each shaft coming in contact Vwith those on those next adjacent. The rabble-shaft 11, which is situated 'nearest the combustionchambers 6, 7, `8, and 9, and isd consequently in the hottest part of the 1, is made IOO IlO

- hollow and a continuous supply'of cool water recess 32, which directs an at the junction of the ra .rabble-arms to the passage 33, leading to 'bottom' of the rabble-shaft and attached to the top of the shaft 11 is 'a is fedY to the top yofthe shaft 11 by means of the fixed sup l pie 19- land circulates through said s ia hen it is .more convenient, the wate lfor cooling the rabble shaft and arms can b introduced'through the In thecenter of vertical down-pipe 20. Said down-pipe is closed at the bottom and connected ^at the top 'with' pipe 19 by the stuffing-box 21. Projecting at right angles from the down-pipe 2() and entering the rabble-arms. 15 are pipes 221, which are o en attheir ends.

23 is an over owfpipe. v

the bottom thereof for the purpose of conveying the water therefrom; Y

v26 represents screw-plugs in the ends of On one end ofthe rabble-arm 15. is a spigot I 27, which enters a hole 28 inthe rabble-shaft 11which shaft is thickened at this point.'

ble-shaft' 11 and one or other of the passages 34 and 35, which pass down opposite sides of the rabble-shaft 11 to the bottom of the saidshaft, where y fastened tothe rabble-shaft 11 by means of.

they meet. The rabblelarm -15 islsecurely b oltspassing through the flanges '.29 of the armv 15 and 'the` couplingiece 36, .situated on the opposite side of t e said slraft 11. 4

When there is much leakagegof water from the junctionof said rabble-shaft 11 and said rabble-arm 15, the small space between the edge of the annularring 31 and the flange 29 -when'the arm is in position can evcalked with asbestos fiber or other suitable material.V fThe two assages 34 and 35 are onlyl required when or ,economy in constructionthese *rabble-shafts are made in sections. When these rabble-shafts are east all' in Y one piece, only one of these passages 34- or 3,5

willbe required and the passagesBS .all made Y to lead yto it.

' 37 is a tap` to w1thdraw the contents from the said passages 34 and 35. 38 isa ta' to. withdraw the `water from the rabble-'s aft when same requires 'cleansing of any solid matter deposited in it' without withdrawing the rabble from the furnace. y

It will be observedv by an inspection of Fig'. .13. that there are openings 38a through th projection 3,8b

V24 is a trough having pipe 25 I' attached to The space betweenthe outside of.

leakage of water' on the inside 'of the rabble- J shaftv 11. The said projection `38,b surrounds the bottom of and is for the'purpose` of preventing any lateral motion of the down-pipe 20. The openings 38a through the. projections 38b permit of the Water in portion of the rabble-shaft passing` to the ap 38.- Y Usually betweenthe hollow water-shafts 11 and the furnace land are fitted with solid rabblearms 17 and 18, are other hollow'rabble-shaftsl the upper solid rabbleshafts 13- and 14, which-are situated inthe cooler part' of the 12, carrying hollow rabble-ar1ns 16, through Whicha continuous circulation of cold air asses u ward from the air- supply pipe 39,1

eading om a fan. (Not shown.)

40 represents holes in the bottom and near the ends of the said rabble-arms 16, through which the air passes and assists'in the oxida n tion of the ore passing through the furnace. Said rabble-arms 16 have a core .41 passing .horizontally through and supported in its center by the projections 42.

baid core 41 bears all the stress of the weight of the rabble-arm y and teeth, vand the air passing through the rabble-armpreyents said core 41 from being 'overheated.,. Whe're theI double-arm rabbles are used, the flange 29-of the second rabble-A lace of the couplingiece 36, the flanges o' thetwo rabble-arms ein thus bolted to each other. lWhen theV rabb e-armsl are. comparatively short and great strength is not requiredI at thejoint, they cany be simply screwed intothe rabble'-l shafts or attached in any other more suitable manner.A rabble-arms are hollow a b 'olt may be passed right through the whenon screwing up the nut or nuts of said bolt the arm' or amns are firmly fixed to the shaft.v It will be readily understood thatv the furnace can have any nunxberof either water, air, and solid rabblespr any number of any one .of these kinds of rabbles ywithout any of 'either of the others.

arm simply takes the The temperature of the roasting-chambers 'l As, for instance, where the' 10p arm or arms andthe shaft, l

IIO.

when no fuel is used, or when said roastin -v g .chambers aremuffledand fuel isi used, wil

notgen'erally require' water-rabbles being usedV in them. In such cases air and soli rabbles orsolid rabbles only maybe used.y 43 isa feed-ho per.

ore from the oblique .chutes .45 below.v r

6 represents ho .`zontal chutes connected` to the bottom of thefdepending chutes 45. v

. 47 represents Archimedean screws, which feed the orev from lchutes 46 lon tothe coolest 44 represents` uted rollersto feed the raw hopper 43 to the depending nary mechanical means can be emplo ed for and 51 are hinged shutters at the bottom of the inclined chutes 48. Y'

-52 is a slide in and near the bottom of the main chute 49. 53 represents cams keyed to the rotating horizontal shafts 54, and which said cams bearagainst the arms 55 of the shutters 50 and 51. 56 is aconnecting-rod joining the crank 57 to the slide 52. The arms 55 of the shutters can be so arranged and formed that two of the said shutters may be operated by one of the cams, and obviously any ordioperating the shutters 50 and 51 and t e slide 52j Thev horizontal shaft 58 is rotated at .twice the speed of the horizontal shafts 54, and they may each be operated from the main shaft 59, which imparts motion to the gearing, rotating the rabble- shafts 11, 12, 13, and 14 of the furnace 1 by any means, such as belts and pulleys. The rabble-arms 15 on the rabble-shaft 11, or such other shaft as" may be located at this point, areso arranged in relation to the cams 53 and thecrank 57 that during the rotation of the rabble-arms 15 and immediately before theyreach the inclined chutes 48 the `alternate hinged shutters 50 `or 51 at the bottom thereof are opened the cams 53 and are closed immedlately the ore fed to the inclined chute 48 by the rabble-arms 15 has passed tothe main chute 49, where it falls on'the slide 52,

In the interval between the closing of the shutters 50 and the opening of the shutters 51 the slide 52 is opened and closed vby the rotation of the crank 57, and t1 .e ere resting on said slide 52 falls down-the continuation of the chute 49 to theoutside of the furnace or to the finishing-chamber 60 or. to the cooling-chamber 61. 'By these means any current of air is prevented from passing upward from the main chute 49, at the same time allowing a free passage forthe roasted ore from the roasting- hearths 2, 3, 4, and 5 to the finishing-chamber 6() andthence to the cooling-chamber 6-1 ordirect either to the cooling-chamber or to the outside ofthe furnace, the cooling-chamber when used being laced, preferably, below the level of the ottom hearth 5 and at one side of the furnace and the finishing-chamber when used being preferably a continuation of the bottom hearth,

as shown in Fig. 38.

Itis obvious that the yfinishing-chamber 60 and the cooling-chamber 61 when used may extend in any direction desired.

62 represents adjustable slides fitting over the-opening ofthe inclined chutes 48.

63 represents projections standing upward ing at right angles to the slides 62, over which projections the ore passes from the roastingchambers and through holes 64 in the said slides 62 to the inclined chutes 48. Vhen a more rapid dischar e is desired, the slides 6'2 are Withdrawn, an the ore then passes direct to the inclined chutes 48.

65 is a flue to sup ly air to the furnace 1. This iue crosses andp then runs parallel with the main flue 66, which leadsto the chimneystack (not shown) alongl one side of the dust-` chamber 67 to the downcast 68. Midway across the dust-chamber 67 the Hue 65 enters the hollow baffle-wall .69, Where the air in its passage around horizontal partitions 7() in said wall 69 becomes heated and subseuently enters flue 71 running from the owncast 68 parallel to and entering part 72 of the cooling-chamber 61, in which it becomes superheated. The impact .of the furnace-gases a ainst the hollow baffle-wall 69 1 and the simu taneous cooling of said furnace-I gases also cause any dust in them to be deposited in the dust-chamber 67', from the bottom of which said dust can easily be withdrawn by drawings; but -it is obvious that any number can be used, according to the extent of utilization of heat and deposition of dust desired. When more than one hollow baffle-wall 69 is used, they can be so positioned that the hot furnace-gases will be made to pass alternatelyover and under them or around the alternate sides of them, so as to bring said hot gases. the better in contact with thesurfaces of said hollow baffle-walls 69. The dustchamber 67 is preferably made of large capacity, so as to lessen the speed of the gases through it, thereby giving the dust in them a better chance to settle and the heat in them a better chance of being absorbed by the air passing through the hollow baffle-wall 69.

73 isa Hue to lead the superheated air from the part 72 of the cooling-chamber to the upcast 74. Said due 73 passes above and runs parallel with flue 71 Y 7 3a is a damper to regulate the amount of superheated air passed through flue 73.

75 represents inlets for the passage ofthe superheated air underneath the fire-bars 76 in the bmbustion- chambers 6, 7, 8, and 9.

77 represents inlets to allow the superheated air to enter and pass over the fires in the said combustion-chambers.

78 represents sliding dampers to distribute the supply of air to the inlets 75 and 77.

The air entering the combustion-chambers creates a reducing or oxidizing flame, accordto whichever inlet, 75 or 77, the air passes through. When desired, cold air may also be admitted to the ,combustion-chambers through the adjustable ash-pit doors 137 and through passages 79 at, the back end of the said combustion-chambers.

o ening sliding dampers 100. Only one hol ow baffle-Wall is shown in the IOC IIC

, hearths.

80 is a flue to convey the superheated air from thelgpart 72 ofthe coolingchamber direct to the roasting-heart'hs when required. 80a is a damper to regulate the amount of superheated air passed through'80. 80h represents Vertical l'ues leading from 80 at any point or points.v along the length of the 80@2 lrepresents dampers for -the regulation of said superheated air through the inlets 80d to the roasting-chambers.' lf desired, said lines 80 and 80b can be built into `the thickness of the said furnace-walls. When supplementary iiring along thezside's of the' hearths .is practiced, Vthe `air for com'- bustion can also be supplied from said flue cuits above described.

-' Across the cooling-chamber 61 and about midway of its length is av wall 81, Which di-A' vides 'said cooling-.chamberinto two'pa'rts 72 by flue cooling-chamber.

81 is an opening 83 of any suitable width-and in any desired belower than the hearth of part 72.

and `-82. In part 72 the ore which is dischargedfrom the furnace-hearths 2 3 4 5 orI finishing-hearth .6 0 is partially cooled, the

air used `for that purpose passingwhen heated 73 tothe combustion-chambers or roasting-chambers. Part 82 is simply .a

In Vthe center of said wall height. -Slidin'g'vertically-and smoothly lin lthe opening -83 are two adjustable slides 84 and 85, placed a few inches apart and held pass through the standards 87 and holes (not shown) in the slides 84 and 85. That slide ing-chamber 61.

90 re resents solid rabble-.arms fitted with movab e teeth and attached to the shafts 89 in part 72 of 4the cooling-.chamber v61.-

.91 represents rabble arms` attached to those shafts 89 which are situated in the opposi'te end of the said coolingfchamber 6 1. The rabble-armson either side of the adjustable slides 84 and 85 rotate in opposite directions and are arranged in relation tofeach other, as shown in Fig.; 3. Y

92 1s an ofpenlng for the ingress of cold air to part 82 o the cooling-chamber 61.

93 is an up'cast, through which the air escapes from the part-82 of the cooling-cham- 94 is a discharge-chute through whichthe' Vore is passed from the cooling-chamber 61.

95 is a flue connecting the dust-chamber 67 to themain liuc 66. l

When necessary, a fan can be used to cause thecirculation of air through the c1r-` position bythe pins-86, which E 82 may y 96 is a sliding damper in flue' 95.

97 represents bridge-pieces dividing the hearths 2,

3,4, and 5 from the fire- boxes 6, 7, 8,and 9. v 98 represents the throats `or passages through which -the products of combustion and calcination pass from the furnace t'o the dust-chamber 67. l

y 99 represents sliding dampers in said passages98 to distribute the required amount of draft over each hearth for the proper. oxida-` tion of the ore being roasted upon it. Y v

101 represents port-holes in the sidewalls of the furnace Vabove the level of the hearths for the admission of air when required to assist in roasting the ore and through which observations can be made and-any repairs effected. to the rabbles or interior ofthe furnace thatmay be required.. 102 represents doors over sa'id port-holes.' Said doors 102 c'an'be of any design and When re uire'd means can beprovided in them for a lowing any amount of opening or no opening atall, so that the amount of air let into the roasting-chambers can be accurately adjusted or altogether stopped.

To provide for theexpa'nsion 'of the hearths consequence of the-great heatin the furnace, a slight depression 103 sformed in and l i I 'along the center of the said hearths. The said ,depression 103 allows the hearths to risewlthout comingin contact With the rabbleteeth on the vrabble-arms.

104 represents rectangular projections on the top, and 105 recta ar projections on the bottom, of the rabb e-arms, overwhich the recesses 106, formed in the jaws 107 of the front and back teeth 108 and 109,respec "tively, are passed.

110 represents spacing-bars to keep -the teeth forming any. rowl at given distances.

apart. 111 representsv pins which pass through land hold `the `said spacing-bars 1 V10 to the rabble-arm. y. i

The back lteeth 109 are broader than the Afront teeth 108, and their effect. on passing through the ore is to form deep furrows in it, thereby exposingas great a possible in a given hearth area.'- 'lhe front teeth 108 are narrower and have at their bottom end a broad foot-1 12. These front' teeth 108 immediately preceding, as .they do', the back teeth 109 eectively open up the ridges of ore vforming the `furrows Amade by the back teeth on the previous revolutionv of the rabble,

anda very thorough and frequent exposure ofthe ore 'particles to the oxidizing atmosphere is thereby attained. To connect the said teeth 108 and 109 to the rabble-arms, the jaws 107 are'passed over the arms between the rectangular projections 104 andv and then slid along the arm until the ree cess 106, formed in the jaws 107, covers the said projections, when the 'teeth` 'will be rmly'secured. When the inclinatin'of the loo lic

surface of ore as izo hearths is found to be insufficient to cause the ore to pass through the furnace with sufficient rapidity, I remove some of the end teeth 108 and 109 of the rabble-arms and substi-` i it is desired to retardthe passage of the ore through the furnace, the teeth 113 are reversed, when the required result will be effected.

, When the finishing-hearth 60 is used, the ore discharged from the bottom hearth 5 of the furnace is rabbled over the 'slide 114 (the height of which can be adjusted) in the step 115, formed by lowering the `hearth when extending said hearth to form a finishinghearth.A i

116 represents hollow shafts passing vertically through the center of the finishingchamber 60 and carrying, preferably, hollow water-rabble arms similar to any of those described herein, or these rabble shafts and arms can be cast in one piece, and thereby avoid the necessity for making the joints of arms to shafts within the furnace, and in this case said Shafts 116 need not extend through the finishing-hearth. Said rabble-arms convey the ore (delivered from the furnace-hearths 2, 3,

4, and 5 on to thefeed end of the iinishinghearth) to a discharge-chute (not shown in.

the drawings) in the end of the fim'shingv chamber similar to the discharge-chute 94 in the end of the cooling-chamber. The rabbleshafts 116 are driven in the same manner as the shafts 11, 12, 13, and 14 of the furnace I. The holes in the arch of said finishing-chamber 60 must be of such size and shape as will suit the rabbles to be introduced therein.

In some cases, particularly where a lowarched furnace is being used, I preferto dispense with the rabble-arms 15 and the pipes 22, as described and as illustrated in Figs. 11, 12, and 13 of the drawings, and substi tute therefor a hollow rabble-arm 117, (see Figs. 15, 16, and 17,) having a vertical partition l 18, extending nearly the whole of its length, and a jet 119, which screws into the downpipe 20. The mouth of the said jet 119 completely covers the opening on one side of the' partition 118, and the water forced therefrom passes along one side, round the end, and back the opposite side of the partition 118 to the rabble-shaft 11. On turning the said vdown-pipe 20 in the rabble-shaft 1'1 the jets 119 are disengaged from the openings in the rabble arm 117 and canbe Withdrawn through the top of the rabble-shaft. In some cases I prefer to omit'the pipes 22, 'and in substitution for them I provide the downf pipe 2O witha jet 120., Fi 18, for each rabl'e-arm 15 attached to t e shaft. Said jet 120 does not enter the rabble-arms, but is so positionedthat it directs a stream of water to the center of the hollow rabble-arm, as shown. The water in the down-pipe 20 is maintained at any suitable pressure, and the velocity with whichgthe water enters the rabble-arm from this jet causes a centralcurrent of cool water to flow from the inner to theouter end of the arm, which in turn is heated and displacedby the cool water continuously injected, the heated water from all the arms returning to the rabble-shaft and overflowing through pipe 23. Thus a continuous circulation of water is effected through each arm to keep it cool, andthe down-pipe 20, with the jets 120, can be withdrawn from the rabbleshaft through its top for the purpose of renewal or repairs without interfering-in any way with the rabble shaft or arms in the fur- Where water is scarce and onlya minimum quantity can be employed in the cooling of the rabble shafts and arms, I provide a modi'- fied form of arm 121, (see Figs. 2O and 25,) which has both a water-passage 122 and an air-passage 123. The ,said air-passage 123 surrounds the water-passage 122 and is open in the roasting-chamber at both ends. A circulation of air and water passes continuously through their respective passages, the circulation of water being effected in a similar manner to any of those herein described.

In Figs. 21 and 22, Where I have shown a modified form of air-rabble shaft and air-rabble arm, 124 is the shaft, 125 is the rabble-arm, and 126 represents partitions in the rabbleshaft passing obliquely from one side of the shaft to the other. That portion of the partition 126 which abuts against the vertical partition in the air-rabble arm is made vertical. The vertical partition 1 27 in the rabble-arm extends from the vertical -ortion of the oblique partition 126 in the ra ble-shaft nearly the whole length of the rabble-arm. The junction of the arm to the shaft may be constructed in the same manner as the water-rabble arm and rabble-shaft hereinbefore described.

Cool air enters the bottom of the shaft, and

, it will be seen that the said air must circulate through every division of the rabble shaft IIC and arms before it escapes from the shaft-top,

and ifnecessary to induce the flow of air the shaft-'top can be extended vertically. Any suitable valve may be placed in the top of the shaft 124`for re ulating the amount of airallowed to pass t rough the rabble shaft and arms.

128 (see Figs. 27 and 28,) is a flatrabblearm attached to the rabble-shaft 129 by means of a coupling-piece 130 and is for use in very shallow roasting-chambers.A 131 is an annular recess in the bottom of the arm 128 and couplingiece-130. 132 is a bush built into the heart of the roasting-chamberv and projecting upward into therecess 131 to prevent the ore falling from one hearth to another. Said rabble-arm 128 and shaft 129 areshown solid in the drawings; lbut it is ob water circulated through. them in any 'manner herein described. Y. 133 (see Fig. 23) illustrates a double rab blelarm flttedwith oblique teeth 1 13, those on one larm stirring the ore left stagnantby thse on the other and the teeth on'onearm belng placed at the oppositeangle to those on the other arm, so that whenv in motion the outwardlyfthrowing eiiect of those onthe one arm will-be counteracted by the inwardlythrowing eiiect of those on the other. It is uite obvious that rabbleshafts with `more' t an two rabble-arms attached abdve each hearthm-ay be used, andthe paths of the rab ble-arms of one shaft can overlap thoseof the rabble shaft or shafts next adj aeent without coming into contact so long as the rabbleshafts are made to rotate alternately'in right and left hand directions.

. In the drawings I have shown the rabbleshafts- `11, 12,'13, 1 4, and' Worm and bevel gearing; but it is obvious that other means. can be used, andwhenmore convenient they can be driven from beneath the furnace instead of from above it, asshown. g '1' The hearths 'may have a shallow ste or steps introduced at'any point, or points a ong', their length when it is desired thatthe' ore operated by the rabble arm or arms below` said' step orstepsshall not return said orev back toward the feed end of said hearths.

' In'order to obtain a maximum amountof combustion-space, a modified form orconf struction-and arrangement of fire-boxes is illustrated irl-F ig. 9, Where 6, 7, 8, and 9 are the fire-boxes.' 76 represents the rire-bars: 134 represents holes for the passage of air to i andthe escapeof ashesfrom the inner ends the alteredof the fire-b of fire-boxes can of oxes. It will be seen that the inner ends ofl the fire-v boxes or combustion- chambers 6, 7, 8, and 9 overlap and the {ire-doors 136 are on alter.- nate sldes of the furnace structure. When .this arrangement of fire-'boxes is used'and the air for combustion is heated, as hereinbefore passages 75 and 77 must be modified to suit positions-of the -ash- pits 135 and 7 8and 9. When the air for nre-boxes 6,

can be simply combustionis not heated, it.

allowed to owin from the atmosphere through eitlder'o'rboth of passages 75 and 77, or instead' of entering under the fire-bars'b'y passages 75 it canenter through passages 79 and through thefront oi ash-pit -135 by the adjustment. of d oors 137 This arrangement course be used When required on 'either' side of the `furnace at any point or points along the length of the furnace as Well as at the end. y

89 operated by 135 represents ash-pits.

vv-62 represents the slides `in I,the top thereof.

-1'38repre`sentsf disks keyed to' averti cal sha-ft 139. 140 is a ldisk keyed to a'vertical shaft l141. Said shafts'13'9 and 141v arefoperated by' the same mechanical means and. at"the same rate oi speed. 142-representsheles in said disks 138. Said holes 142v are situated on opposite sides'of the shafts'.v 139. in each alternate chute. 143 represents holes in disk 140. ,144 represents openings in the edges oi lthe said disks 1 38 and 140, to receive a piece ofthn metalv plate to adjustably close the holes I142 and' 143in. the v*disks 138andj1l-0 'when desired.- As willfb'e vWellf'*uil'd'lltoori, when this'niethod is used the ore assing Vdown the inclined chutes 48 passesthrough lthe holes 1112 in any two alternate .disks1'38 v whensaid-holes 142 are in linewithjqsaid chutes/18.- v.After passingfthrough thev'said 140 inthe main chute. When either ofthe holes143 in thesaid disk .140 is in line with direct vto the outside 'ofthe furnace. "Itis and 51 and slide 5 2, hereinbefore describe lwith the slide 52 orl the. shutters 50 and -5 1 4140. In Figs. method I in `which lsha ow roasting-chambers are-repoints ineach troasting-chamber,/and at ,the

leyel, the. depression causedl by lowering t ev brick larches 4being Vmade up by thickening lmaterial.`

.V146 v(see Fig. 2)re resents chutes ini the salt' to the ore on'the hearths'during the later or anyother stage of the roast .when a chlori- 'dizing roast is being eil'ected.Y The salt may be fed automatically from a hop `er situated above the furnace to the hearths l by anyordinary mechanical means, and the ore can, if deslred, be discharged direct from'fthe roast-I -inghearths into pits to after chlorinate.

The introduction of carbon into the roastingthe'main chute 19, the ore" therein passe'sf'to the coolingchamber ornishing-chamberjormay/be used in combination dis k '39' and 40 I have'illust-ratedthe .em loy of constructing a-'furnace the roasting-hearth may vary at different the said arches or by iilling with sand or other holes 142.in the said disks it falls on the" disk 1 'obvious that instead .0f using the disks 138 and. '140, as above described, or the shuttes quired. The arches 145 over the portfholes 101 are at right angles to the length ofthe IIO I zo "side ofthe furnace 1 orthe introduction of y

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