US2211957A - Method of furnace charging - Google Patents

Description

Aug. 20, 1940- H. n, MacMlcl-IAEL METHOD OF FURNACE CHARGNG Oli'ignal Filed June 2l, 1935 5 Sheets-Sheet l Aug 20y 1940 H. R. MaMlcHAEI.

METHOD OF FURNACE CHARGING Original Filed June 21, 1955 3 Sheets-Sheet 2 A si@ f m 2PC www# mwmq www

INVENTOR. Hugh TL VIf- HichaeL BY am ATTORNEY Aug. 20, 1940. H. R. MacMICHAEL 2,211,957 i l METHOD OF FURNACE CHARGING y Original Filed June 21, 1935 3 Sheets-Sheet 3 F'IQQ.

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vHuh R. MacMchael.

A TTORNEY Patented Aug. 20, 1940 NETE!) STATES aznar orifice f 27,697. Divided and this application August 1,

i939, Serial No. 287,785

2 Claims.

This invention relates to a method of furnace charging and more particularly for the charging of a lead-smelting Scotch-hearthtype of elongated furnace. rThis application is a division of application Serial No. 27,697 of June 21, 1935. Reference is also made to application, Serial No. 124,834, for which this application is a substitute.

The Scotch-hearth type of lead-smelting furnace is commonly built with a crucible Z0 inches wide having a continuous opening over its front side, and over its rear side having a water-cooled wall with longitudinally-spaced tuyre openings therethrough positioned just above the level of the front over-flow level of Crucible. In operation, said crucible is full of molten lead whereon the smelting charge is floated with a charge depth of about a foot at the furnace back side adjacent the tuyres, tapering downwards across the furnace forming a Wedge-like cross-section (see Fig. 9). As heretofore generally built and manually charged, the furnace is worked through said front side opening including the working operations of shoveling in of the fresh charge, of rabbling and of backing or reforming the entire smelting charge, and of the removal of the discarflahle lump-slag product from the furnace.

The charge generally consists of lead sulphide (galeria) ore concentrates in a pulverulent ystate with coke rines as fuel, and certain lay-products.

The continuously-operated furnace is worked on a cycle repeated at intervals of 11A; to 2 minutes, the shorter time being preferable except hitherto as to the endurance of the operator. Following a mechanically quiescent period of a minute or so, the entire charge is rabbled and backed into its normal smelting Wedge-like crosssection. Thereupon, fresh charge is added by the operator from a hand shovel as heretofore charged, which he does with a peculiar swinging motion whereby said charge is skillfully spread over the smelting surface in a'thin, carefully distributed layer, thereby permitting an effective contact of the air blast (supplied through said tuyre opening and emerging through the surv face of the sinelting charge) with the fine particles of the freshly added charge causing an active oxidising or roasting action to take place thereon. in about a minute after charging said roasting effect is about completed and and the furnace is then to be started on another working cycle as above described. Unless the fresh charge is added at the proper time and properly distrib-- uted over the furnace, all or part of the smelting surface may become overheated and an excessive 55 amount of lead will then be volatilized with resultant wasteful expense. So exacting is the operators Work in manual charging, that under otherwise identical conditions a stronger and more skillful operator will commonly get a onethird greater tonnage through a furnace than will a poorer operator, and the same 'skillful operator will do notably better work in cool far vor-able Weather than when it is oppressively hot. Various efforts have been made to substitute mechanical methods and equipment for the charging of the furnace but all such efforts heretofore have been abandoned. p

The general object of this invention is to -provide methods of charging the lead Scotch-hearth furnace mechanically, thereby substantially reducing costs and increasing furnace capacity by maintaining the latter at its best operating rate and condition unhampered by the limitations of human skill and endurance.

Some of the specic objects of this invention are to provide methods for proportioning and assembling the materials makingv up the furnace charge, for controllably distributing the same on a charger to form thereon a unit charge in a thin layer of controllable variable thickness in its different parts and having generally the areal distribution currently required for the furnace, for depositing said unit charge in the furnace generally reproducing therein said predetermined thin layer distributional effect free fromundeable distributional irregularities or ridging effects.

Other objects are to provide methods whereby the separate proportioned elements of a unitv charge may be placed controllably and respectively in superimposed thin layers on said charger and thence deposited in the furnace with a mixeffect thereby to obtain a thorough mixture of the charge elements as deposited in the furnace, while the areal distribution therein of each element is independently controllable by the preceding distribution thereof on said charger.

Another object of the inventionis to provide methods whereby a mechanically-handled unit charge may be placed in the furnace, of manuallycontrollable variable thickness, enabling the op erator tomake charging corrections for irregularities in the running of the furnace after the manner now accomplished in manual charging by a skillful operator. For instance, if one part of the furnace is too cool, he 4may compensate by adding additional fuel in that part. Or if one part has smelted more rapidly so that the charge depth is too little, he may add additional ore and i fuel thereto.

The foregoing and other objects of the furnace-charging methods of my invention may be better' understood'by a consideration of an arrangement adapted to the practice thereof, as set forth in the following description taken in connection with the accompanying drawings forming a part thereof, in which:

Fig. 1 is a diagrammatic plan of the charging system and a furnace.

Fig. 2 is a diagrammatic side elevation of Fig. 1.

Fig. 3 is a longitudinal vertical section through a feeder with part of bin and charger.

Fig. 4 is an elevation on the line 4 4 of Fig. 3 and also an electrical control diagram.

Fig. 5 is a plan of the charger.

Fig. 6 is a side elevation partly in longitudinal cross section of Fig. 5.

Fig. 7 is an end elevation of Fig, 6.

Fig. 8 is an electrical control diagram for the charger movement.

Fig. 9 is a partial cross-section through the furnace and charger viewed on the line 9*-9 of Fig. 1.

Like reference characters denote like parts in the several gures of the drawings.

The furnace |85 has the crucible |04 (see Figs. 1 and 9) over the rear side of which is the wall |52 in the lower part whereof are the longitudinally spaced tuyre openings |53. Over the front side of said crucible |5| is a longitudinally continuous opening underneath the hood |25 generally enclosing the balance of said furnace. In said crucible the space up to the line 12 will 4be occupied in operation by molten lead, and floating thereon will be the smelting charge generally under-lying the line 6| occupying the wedge-like cross-sectional shaded area 1| having a depth of about a foot on the tuyre side and tapering down to almost nothing at the other side of said crucible. Longitudinally adjacent at each end of said Crucible |5| are the dead plates 639 and the slope plates |56 adapted to receive charge deposited outside said furnace Crucible length by the movable charger 206. Said hood |55 is provided with the end extensions |55 having the openings |59 wherethrough said charger 285 may pass.

The charger 200 has a longitudinal frame composed of a left channel 252 and a right channel 263 between which are carried a plurality of spaced sloping flat plates 2M, the bottom. of one said plate overlapping the top of the next in louver fashion. The plates 204 have a slope somewhat less from that of the angle of repose of the charge as it is dropped from the feeders 255 to the charger 200, which slope may approximate a twenty percent grade, sloping downward in the direction in which the charger is moving as it decelerates for dropping its carried charge into the furnace |66. The closure plates 255 and 256 are welded to the channels. 252 and 253 respectively thus making a water-tight space 285a and 2050: respectively adapted to the circulation of water Where this may be found advantageous.

The frame 20| 'u suspended from a plurality of spaced axles 251 carried by the wheels 288. The charger 205 is impartedlongitudinal movement through its end beam 2F19 having a rope `clamp 2| attached to a rope 2| Ioperating over the left end sheave 2|3, the right end sheave 2M, and is driven by the winch 2|6 through the motor 2I1, for travel on track rails 22| and 222 suitably supported.

The motor unit 2|1 is preferably a direct-cur rent compound-wound, variable speed four-toone ratio, reversible motor especially adapted for frequent quick starting and stopping, provided with a solenoid brake 218, and having the automatic control panel 510 actuated by the power contacter 512 (see Fig. 8) for movement to the left toward the furnacel and the panel 51| actuated by the power contactor 513 for movement to the right away from said furnace, each said automatic panel being electrically interlocked (not shown) with the other and equipped for push-button remote control, and having the shunt-neld rheostats respectively 531 and 538 manually adjustable for controlling the speed separately in each direction of said motor 2|1. At its lowest speed the motor 2|1 will be adapted to impart movement to the charger 20|] to the right at a speed of about four feet per second under the control of the panel 51| and the contactor 513, which movement is brought to a stop by the action of the solenoid brake 2l8 on said motor 2|1 when the current is cut off same. At its highest speed said motor 2|1 will impart movement to said charger 200 to the left at a controlled speed up to about sixteen feet per second under control of the panel 510 and the contacter 512, which movement will be controllably decelerated by the solenoid-brake 2 5 with said motor 2|1 said brake being rendered inoperative when current is supplied to said motor 2|1, and by means of adjustable spring or dead-weight pressure becoming operative instantly when the current is cut 01T therc from.

When used in the charging of said Scotch hearth type of furnace, said. plates 254 may be loaded longitudinally generally uniformly as viewed in longitudinal sectional area 262 (see Fig. 3) and with a laterally tapering load 2Min (sec Fig. 9) delivered through the feeder area 243 (see Fig. 4) thereby providing for heavier charging on the more active side of said furnace adjacent said tuyres M5, with generally uniform charging longitudinally.

The belt feeders 250 each have a conveyor belt 25| supported on the idlers 252, a tail pulley 253 and a head pulley 251| all carried on the frame 255, said head pulley 255 being driven by a shaft 256 connected with a geared speed reducer 251 driven from a motor unit 258 all suitably carried on a floor 260 carried by columns 26E supporting bins 262 each having a back plate 263, side plates 264 and the front plate 265 provided with an opening 266er extending between the cheek plates 266 connected by a baffle plate 26'! through which opening the charge or material carried in said bin may pass out under the control of the sector gate 268 carried from the pivots 269 by the levers 21B each having front pivot 21| supported by a turnbuckle 212 suspended from the solenoid magnet 213 supported from the bin front plate 265. Each end of said gates 265i has its support as described and is thereby separately adjustable as to the height of the opening 258:1 left between it and the feeder belt 25|, the turnbuckle 212 being adapted for ample manual adjustment and the solenoid 213 for a limited remote-control electrical adjustment by the manual operation of a switch 214 of which there is one conveniently located for each solenoid 213. Each of the bins 262 has a feeder 250, each arranged in like manner for delivering the charge in said bin by said feeder to the charger 265.

The motor unit 258 is preferably a direct-cur rent compound-wound variable speed motor especially adapted for frequent quick starting and stopping and provided with its integral solenoid brake (not shown) and having an automatic control panel 286' adapted for operation manually and' also from the control system 560, and having a shunt-field rheostat 28| manually adjustable for controlling the speed of said motor 258.

An operation control system generally designated as 566 is adapted for the timed control of the charger and the correlated control of the feeders. A clock-like timer |4 has the rotor 5|5 the speed of which is adjustable for the length of the operating cycle desired. Said rotor 5|5 receives electric current at its center from the relay bus 193, and at each revolution momentarily energizes contact 56| of line 630 energizing the solenoid coil 512e of the relay 512 thereby closing its power current contactor 5121) and its relay current switch 512e through which relay current continues to flow until the stopping relay switch 516C is opened by the operation of the relay 514 energized by the line 63| from the terminal 64| (see Fig. l) as the charger 26|) is to be decelerated and stopped at the left-hand end of its travel into the furnace |65. Said power current contactor receives current from the power bus 495 supplying it to the panel 515 adapted to the control of the motor 211 for moving said charger to the left only, at a speed manually adjustable by the rheostat 531 on said panel 51|).

When said motor 2|1 has stopped after cutting off power from said panel 510, the panel 51| electrically interlocked (not shown) therewith is actuated by said relay line 63| also connecting to the power relay 513 and remaining activated until stopped by the relay 515 energized by the line 632 from the terminal 642 (see Fig. 1) located near right hand end of the charger 200 travel.

In all wiring diagrams only one pole is shown (for simplicity) the other pole being assumed as grounded.

Near the right hand end and on one side of the charger 266 is a lug 585 (see Figs. 1 and 6) adapted to contact with an operating lever 580 of the switch 58| causing the blade 582 to move into contact with the terminal 533 thereby delivering current from the connected relay bus 483 to said terminal. As soon as the said lug 585 moves out of contact with said lever 586, the switch 58| returns to its neutral position by the tension of a spring not shown. The terminal 583 may be located to one side or the other of the switch 58| depending on the direction of travel of the charger 259 at the time when thedesired contact is to be made. There are siX switches 58| respectively connected with the terminals 64|, 642, 543, 621|, Site, and 541 (see Fig. '1) inclusive energiZ-ing the relay lines 63|, 632, 634, 636, and 631, and each of said switches 58| are appropriately located on the charger track angles 22| and 222 (see Fig. 4) relative to the passage along same of the `charger lug marked 58511 on left channel 232 and 58517 on the right channel 203 (see Fig. l) so as to cause the related operating effect to take place at the predetermined point in the travel to the left or to the right of the charger 266.

The terminal 55| is adjustably located near the furnace mi! where deceleration of the charger 25] is to begin, said deceleration causing the carried charge to be discharged with a spreading effect into said furnace lll, said terminal 64| being connected through the line 63| to actuate the stopping relay 515 (see Fig. 8) for opening the relay contactor 512 as above referred to.

The terminal 643 (see Fig. 1) actuated by the charger lug 535% connects by the line 633 to a starting relay 65| (see Fig. 4) for closing the power -contactor 652 controlling the conventional automatic panel 280 for the operation of the motor 258 driving the feeder 256, the speed of whichis controlled through a shunt-field rheostat 26| on said panel, said terminal 643 being positioned on the charger track 22| relativeto they moving charger lug 585a so as to cause the feeders 256 to start delivering charge to the charger 206 at the proper point in its travel to the right away from the furnace |66. The terminal 646 through the line 636 operates the stopping relay 655 causing the feeder 250 to be stopped as the charge receiving length of the charger 20|! `passes to the right of said feeder 256 for l which purpose said terminal 646 is appropriately positioned near the right end of the charge track 22| and isl separated from the terminal 643 by a distance substantially equalto the length to be charged on the charger 200. In like manner the terminal 5M operates to start the second feeder 250 drivenvby its respective motor 258 not separately shown, and the' terminal 641 serves to stop said feeder through means identical in principle with those for the first feeder 25|).

Mode of operation The Scotch-hearth type of lead-smelting furnace requires a thin layer of fresh charge accurately distributed areally over the furnace, generally uniform in thickness longitudinally but tapering olf laterally from the tuyre side of the furnace (see Fig. 9) towards the open side where little of the air-blast comes through. Properly to control the operation and to compensate for preceding irregularities in furnace working conditions, it is essential that the operator be always enabled to control manually the distribution and quantity respectively both ofthe cre and the fuel of each unit charge, although with a mechanically uniformly charged furnace, many successive charges may be formed and deposited without the necessity for the continuous changes of distribution inherently required in manuallycharged furnaces.

The quantity of charge from a bin 262 is adjustable by the average height of the gate opening 25811 over the belt 25|, and by the relative speeds of the feeder 256 adjustable by the motor rheostat 26| on the panel 286, and the speed of the charger 266 on its loading travel to the right adjustable by rheostat 538 on the panel 51|. The charge distribution laterally on the charger 255i is manually adjustable by the turnbuckles 212 independently adjustable on each side of the gate 265. For adding eXtra charge along one side of the charger 26D over some special length thereof and without disturbing the turnbuckle adjustment, one of the switches 214 may be manually operated raising the gate end thereunder, said gate returning to normal position vby gravity as soon as said switch 212 is opened. Said switches may be conveniently located to suit operator.

The terminals 653, 646 and the like are located relative to the charger lug 585a so as to distribute charge over the desired length of the charger, which length will approximate the charge receiving length of the furnace plus a length to allow for charge falling outside the furnace on account of the spreading effect as deposited in said fur- 'fic nace, and so that irregularities in forming and depositing the end portions of the charger may not result in corresponding irregularities in furnace smelting operations.

The charger speed to the furnace will be suitably adjusted in a range generally of ten to sixteen feet per second, and the deceleration of said speeding charger will be adjusted by means of its adjustable brake 2|8 so that a rapid deceleration causes the carried charge to move ahead relative to the slowing charger thereby causing said charge to pass through the louver spaces 24| (see Fig. 3) and to be deposited below. By suitably reg ulating said rate of deceleration, the charge from a fifteen-inch length of plate might be spread over approximately a thirty-inch length of furnace, while conversely said thirty-inch length of furnace would then receive one-half the charge from each ,of two successive said fifteen-inch lengths of charger, thereby effecting a very complete uniform mixture of the layers of materials of which said charge may be composed. More or less spreading effect may be caused dependent on charger-'velocity in feet per second when brake is first applied and on the resultant rate of deceleration in feet per second, both of which are to be adjusted for the desired effect in relation to the handling characteristics of the charge and the result desired in the furnace.

Having made the aforesaid adjustments determining the quantity of each material per unit charge and its distribution on the charger and thereafter as it is deposited in the furnace, the timer 5|4 is set for the time cycle desired, and the charging operation then becomes automatic subject to ready adjustment manually at any time.

Dumping by acceleration would permit of less impact due to less horizontal velocity in the charge particles as they are deposited in the furnace, which, for some ores, may be advantageous as to furnace operation. A spreading effect may be secured by either of these methods such that 'the charge on one lineal inch of the charger may slide off the supporting plate 291i while the charger as a Whole is moving more than a lineal inch, and consequently the said lineal inch of charge may be systematically spread over more than a lineal inch of the furnace, and one lineal inch of the furnace receives part of the charge carried by more than a lineal inch of the charger, it being understood that inch or inches as used here and in the related claims relates to a conveniently referable unit of distance rather than to a precise unit of measurement.

The distributional effect is readily understood by analogy to manual shoveling. As examples, assume that an evenly distributed load of fluent material is placed on a shovel pallet; a skilled shoveler may then swing the shovel along a path so as (a) to discharge said material into a heap, or (b) to spread it along and generally reproduce the distributional effect which prevailed on the shovel pallet, or (c) he may cause it to be spread over a much longer length than the length of the shovel pallet. Or an effect intermediate to the foregoing typical examples may be produced. The charging apparatus of this invention is devised generally to duplicate any of the foregoing described depositing distributional effects from the appropriately loaded charger.

The charge as deposited in the furnace by aforesaid methods tends to be irregularly spread at each end. Therefore, said irregular end charge is to be deposited outside the active smelting length of furnace on the dead-plates |39 and Vthe slope plates |56 to be discarded therefrom.

The term charge throughout the specification and the claims is to be understood as meaning one or more of the elements whether separately or as a mixture which enter into the charging operation, such as ore or concentrate of same, slag, dust, fume, drosses or scrap metallic material, whether primary from outside source or secondary as a by-product of the furnace operation, flux and coke breeze or other fuel.

Some differing charge elements can be mixed and' suitably handled as a mixture while other elements such as ore concentrates and fine coke breeze (fine coke) will not remain uniformly dis seminated in a mixture after handling through fires. I prefer therefore, to handle each such diverse or heterogeneous element through a separate charge bin and feeder. I provide as many feeder and charge bin units as thus necessary, dependent on the number of elements entering the charge, and whether they can most conveniently and efficiently be handled in certain mixtures or separately, the elements in any one charge bin being preferably of a homogeneous nature as to handling. The more or less heterogeneous elements from the plurality of bins may then each be laid in a suitable layer on the charger by the individual feeders, and followed by the unique spreading and mixing action as the charger load is deposited in the furnace, the results thus obtained are uniform and ideal beycnd any possibility of they prior art.

The charging methods and system as described are advantageous where a unit charge is to be accurately measured and accurately distributed and deposited in a furnace with a controlled layer representing a well-mixed proportionate part of each of the elements going into the charge- It is well adapted to the charging of a very long relatively narrow furnace such as a long Scotch hearth for smelting lead ores. The charger may be made in relatively shorter wider units for other types of furnaces or for other uses of forming, transporting and depositing unit charges or mixtures of marials.

While I refer to a furnace as the place in which the charge is to be deposited, the method described is applicable irrespective of the place in or on which the charge is next to be deposited, and the Word furnace used in the specification and claims will be understood as applying to any i charge-receiving means with which my charging syst/ern may be advantageously used.

This application being a substituted application for my previously led application, Serial No. 124,834, which is a division from my original application Ser. No. 27,697 filed June 2l, 1935, carries much of the original description for details of apparatus adapted particularly to the practice of the methods herein described and claimed. However, other apparatus may be adapted to the purpose. Moreover, other modifications will occur to those skilled in the related arts.

Although certain novel features of my invention have been shown and described and are pointed out in the annexed claims, it will be understood that Various omissions, substitutions and changes in the several steps in the process and in its operation, as Well as in the forms and details of the apparatus illustrated may be made by those skilled in the art without departing from the spirit of my invention.

What is claimed is:

1. The method of charging a furnace of the Scotch-hearth type which includes loading a charger having a supporting surface co-extensive Awith the area Ato be charged, said charger having discharge openings; inserting said charger into the furnace in such manner as not to disturb the supported charge; and changing the Velocity of the chargervso as to cause relative movement between the charge and charger so as to cause said charge to pass through the discharge openings in a projected manner.

2. The method of charging a furnace of the Scotch-hearth type which comprises loading a charger in such manner as to form a plurality of substantially unit volumesof charge distributed over an'area substantially co-extensive with the area of the furnace to be charged, moving said charger into said furnace in such manner as to impart momentum to said volumes in the direction of movement of said charger, then decelerating the charger whereby to cause the momentum thus imparted to said Volumes to project said volumes simultaneously on to said furnace to form a thin even layer of vcharge thereon over substantially vits entire area.

` HUGH R. MAcMICI-IAEL.

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