US2030734A - Furnace construction - Google Patents

Description

Feb. 11, 1936.; D EN@ 2,030,734

FURNACE CONSTRCIION Filed June 18, 1932 5 Sheets-Sheet l BYMMYZM ATTORNEYS Feb. 11, 1936.` D BAIRD 2,030,734

FURNACE CONSTRUCTION 1 Filed June 18, 1932 5 sheets-sheet 2 10 18 46 47 @pg-Z- l" 3 f "I u o I I. f/ .WIW 4g 55 INVENTOR ATTORNEYS Feb. 11, 1936.

D. BAIRD FURNACE CONSTRUCTION Filed June 18,

1932 5 sheets-shed 5 INVENTOR udley 'rd Ml/M y L ATroRNEYS Patented Feb. 11, 1936 PATENT OFFICE FURNACE CONSTRUCTION Dudley Baird, Berkeley, Calif., assigner to Nichols Copper Company, New York, N. Y., a corporation of New York Application June 1s, 1932, serial No. 611,965

2 Claims.

This invention relates to furnaces adapted for various dewatering, drying and roasting operations, and the objects of the invention include y the provision of alfurnace which will be inexpensive and relatively simple in construction and highly eflicient under various conditions of operation. I

Furnaces embodying this invention are particularly adaptable for drying materials such as pyrites, sand, gravel, etc., generally at comparatively low temperatures and preferably out of contact with the gaseous products of combustion of 4the fuel used to heat the furnace.

Various further and more specific objects, features and advantages will clearly appear from the detailed description given below and taken in connection with the accompanying drawings which form a.'v part of this specification and illustrate, merely by way of example, various preferred embodiments of the invention.

Tlfie invention consists in such novel features, arrangements and lcombinations of parts as may be shown and described in connection with the furnaces hereinl disclosed lby way of example only, and as illustrative of preferred embodiments.

In the drawings, Fig. 1 comprises a vertical sectional view partly broken away through a. furnace comprising one embodiment of the lnven.

tion;

Fig. 2 is a vertical sectional view showing a pair of adjacent rotatable and xed hearths;

Fig. 3 is a cross sectional view taken on the line 3-3 of `Fig. 2;

Fig. 4 is a cross sectional view taken on the line 4-4 of Fig. 2; I

Fig. 5 is a vertical sectional View showingthe stationary hearths in cross section, and the rotatable hearths in front view, and showing heating means located in the chamber between the hearths; l

Fig. 6 is a vertical sectional view of a furnace of the type shown in Figs. l to 5, without the provision of means for heating the hearths;

Fig. l is a cross sectional view taken substantially on the line 'I-'l of Fig. l6;

Fig. 8 is an enlarged view of the connection between a rotatable hearth and the central rotatable shaft;

Fig. 9 schematically illustrates a drying furnace arrangement in which hot air is forced through the furnace and the water, etc. from the material dried is condensed and removed from the air, after which it is again heated and forced through the furnace;

Fig. 10 is a vertical sectional View showing a modilled construction of the type of furnace shown in Figs. 1 to 5;

Fig. 11 is a sectional view on the line II-II c* Fig. l0;

n Fig. 12 is a sectional View on the line I2I2 of Fig. 11;

Fig. 13 is a view corresponding to that in Fig. 10 10of a modified construction of the furnace shown ln Figs. 6, 7 and 8; and

Fig. 14 is a transverse section on the line Il-Il of Fig. 13.

This invention relates to the general class oi. 15 furnaces disclosed in the patent to Edward J. Fowler (deceased), No. 1,852,646, dated April 5,` 1932, and may be conveniently used in connection with a calcining furnace operatively associated therewith, as shown in said patent.

The body of the furnace may comprise a cylindrical casing or sheet metal shell as at III, insulated exteriorly by a sheath of asbestos or the like II. The shell may be made of steel, brass, various alloys, or special high temperature alloys, depending upon the use intended, and may be mounted upon columns I2. The lower portion or hot gas chamber of this shell may be lined with brick or any suitable heat resisting material I3 so that it may constitute a combustion chamber when the furnace is used as a roasting furnace, or it may constitute Va reservoir for preheated air or inert gases or the like admitted thereto through the hot air inlet I4, in which latter caseY the lining I3 may be made of any suitable insulating material. The lower end ofthe shell is suitably closed as indicated at I5. At the top of the hot gas chamber and resting on the lining I3, or suitably secured tothe shell, is a discharge trough I6 which communicates with a. discharge spout I1 which may be provided with a discharge door normally kept closed by gravity or spring pressed means to prevent air from entering the furnace through the spout.

Within the shell II), Figs. 1 to 5, a plurality of vertically spaced or superposed hollow hearths may be provided as at I8 and I9. The hearths I8 are supported on and movable with a rotatable shaft 20 which is preferably hollow and which is supported at its lower end on a step bearing 2| and is held centrally in the shell at its upper end in a framework 22 of any suitable construction, and which may also include a cover and sealing means, and means insulating the upper end of the cylindrical shell. The shaft may also pass through centrally of the bottom wall of the hot gas chamber, in proper sealed relationship thereto as will be described later. As shown in Fig. 1, the rotatable shaft may comprise an upper hollow section 23 which is flanged at its lower end and secured by stud bolts to the upper wall of the uppermost rotatable hollow hearth I8. The upper end of the section 23 of the shaft is provided with enlarged portions, one of which engages a suitable packing gland or sealing ring `24 to prevent inlet of air or the escape of hot gases atthis point. The other enlarged shaft portion forms a bearing area in a sleeve 25 suitably secured to the top frame member 22 and which, in connection with a telescopically arranged sleeve 26, constitutes a stuffing box for the upper end of the shaft and providing a swivel connection for connecting a non-rotatable inlet pipe 21 to the interior of the shaft section 23. A liquid, Vapor or gaseous heating medium, for lexample steam, may be admitted through this inlet for internally heating the shaft and hearths.

The shaft 20 may also comprise sections 28 which connect successive rotatable hearths I8 together, and a section 29 which is connected to the lower rotatable hearth and hasvan enlarged bearing area operating in a stufllng box comprising a sleeve 39 suitably mounted in the bottom wall I5, and a sleeve 3l cooperating with the sleeve 30 to form a gas tight joint if desired. lThe sleeve 30 extends upwardly, as indicated at 32, some distance above the lining I3 so as to protect the shaft against any heated material that may have dropped into the not gas chamber. If desired, the sleeve 32 may be extended upwardly to a point close to the lower rotatable hearth, to protect the shaft 20 against heat and also if desired to provide for passage of cool air to cool this portion of the shaft, suchair being admitted through spaces provided for the purpose between the sleeves 3l and 32. The lower end 33 of the shaft may be embraced by a swiveled connection 34 for a condensate outlet 35i for carrying off any condensation, in case, for example, the heating fluid is steam. The interior of the hollow shaft sections registers with openings in the walls of the hearths to provide passages for steam through the shaft and hearths. Secured tothe section 33, which may be solid, is a beveled gear 36 which meshes with a beveled gear 31 driven through a reduction gear mechanlsm 38 from a pulley 39 operated in any suitable manner from a source of power.

As shownA in Fig. 1, doors as at 40 areprovided whereby access may be had to the several hearths i and to the hot gas chamber.

As indicated more particularly in Fig. 2, each rotatable hearth I8 may be of the double conical shape shown. The upper wall of this hearth may be of any other suitable shape, and may be horizontal or inclined inwardly or outwardly depending upon the drying problem. Although the lower wall of the 'movable hearth may be of any convenient shape, it is preferable, however, to make 'this of the shape shown so that it will be substantially parallel with the upper wall of the fixed hearth I9 directly below it, thus providing spaces of the same height throughout between the rotatable and fixed hearths, This shape of the hearths also facilitates the construction, removal and replacement of the in" movable rabble plates 44 which, in accordance with the disclosure shown in Fig. 2, may be carried by the lower wall of the rotatable hearth and which preferably are quickly detachable therefrom. For

l to the other hearths.

which the rabble plates are secured removably 5 and adjustably by any suitable means, such as screw bolts.

The movable hearths may be provided with a. disk-like baille plate 46, Fig. 2, which may be spaced from the upper and lower walls of the hearth by radial ribs 41 preferably cast integral with the bafiie plate and walls, such ribs and disk terminating short of the periphery of the hearth and the ribs terminating at their inner ends substantially in line with the interior of 1 the shaft 20. By means of this construction the heating fluid entering through the inlet 2l, Fig. l, is carried down through the shaft sections and outwardly along the interior of the upper walls of the movable hearths, and inwardly along 2 the lower walls of such movable hearths and then on to the succeeding shaft sections and hearths, as indicated by arrows in Fig. 2.

As shown in Figs; 1, 6, 9 and 13, the upper end of the furnace may be provided with a feed inlet 2 hopper 48 which is preferably kept lled with -material in order to prevent the hot air within the furnace from escaping at this point. Material fed in through the feed inlet 48 is deposited on the upper hearth I8 from which it may be 3 fed by means of a feed scraper blade 49,v Figs.

1 and 5, which may be arranged in a non-radial position, as shown, and which may be adjustable in a sleeve 50 suitably secured to the shell I0, and which may be held in adjusted position by 3 means of screw bolts 5I. By adjusting the scraper blade 49 the rate at which the material is fed may be controlled. If desired, several of the members 49 may be used, either fixed or adjustable in position, and, moreover, like members may be used in connection 4with the other rotatable hearths, if so desired.

The fixed hearths I9 are preferably of the shape shown and are secured in any suitable manner to the shell I0. However, these hearths may be 4 of different cross sectional shapes and may be horizontal orA inclined inwardly or outwardly depending upon the drying problem. These hearths are preferably hollow, as indicated to form a heating chamber to whichsteam or other 5 heated fluid or liquid may be supplied through an inlet pipe 55. Steam outlet pipes are ndicated at 56, and the same are preferably connected to a steam trap. Y

As indicatedin the various figures, the lower 55 wall of each xed hearth carries one or more, preferably a plurality, of rabble plates 51 which may be detachably and adjustably secured thereto :in the same manner in which the rabble plates are secured to the rotatable hearths I9.

It is also within the province of certain aspects of this invention to employ electric heatingunits for the hearths, or to provide means for heating the air or gases which come in contact with the material to be dried.

The lower rotatable hearth I8, Fig. 1, is preferably provided with a plurality of scraper blades 5B which may be secured thereto in the same manner in which the rabble plates are secured As indicated in Fig. 1, preheated air or gas, or the like, may be admitted through the hot air inlet I4 and if desired the air may be heated in a steam chest, as indicated at 59, Fig. 9. After entering through the hot air inlet I4, the air 75 passes over and through the material -as it is moved from hearth to hearth, and then leaves the furnace through an air outlet 60, which may be connected to a stack (if the air is not to be reused), or as indicated in Fig. 9, to a pipe 6|.

which extends to an exhaust fan 62 for forcing the air into a condenser 63 in which the water, etc. in the air is condensed and removed, the air being then forced through a pipe 6I into a steam chest or re box, where it is again heated for circulation through the furnace.

The arrangement shown in Fig. 9 is also particularly desirable if it is necessary to use an inertheating fluid, such for example as carbondioxide, which may be recirculated through the system without loss.

1f desired, one or more of the spaces between the hearths may be heated by a system of radiation pipes 65, as shown in Fig. 5, the hot fluid being supplied from the pipe 55 which supplies fluid to the fixed hearths.

The outside diameter of the hearths I8 and the diameter of the opening on the hearths I9 is preferably such as to provide large areas for the passage of large volumes of heated gases at low velocity so that the ascending gases will not carry off fine particles of the material being dried. This provision gives the apparatus alarge drying capacity.`

According to certain phases of the invention, as indicated in Fig. 6, the central shaft, indicated at 10, may be made of one piece "and the rotatable hearths 'Il may comprise upright cones and may be constructed without provision for heating by steam shownin connection with the above described examples. For purposes of convenient assembly and replacement of the movable hearths, each movable hearth may be provided with a hub 12 formed with a key seat for receiving a key 13 which lies in a cooperating key seat in an enlarged portion 14 on the shaft.

The lower end of the key may contact with a shoulder 'l5 at the end of the key seat'in the enlarged portion of the shaft, and 'may be provided with a head 'I6 which is engagedby the hub 12 on the rotatable hearth to support the rotatable hearth on the shaft. The shoulder 15 preferably extends the same distance or to a lesser distance horizontally than the enlarged portion 14 so that the hearths may be moved over the shoulders into the proper position on the shaft. A feed blade 49, as previously described, may cooperate with the upper hearth to feed the material from such hearth. Each of the rotatable hearths may be provided with pairs of downwardly extending ribs 11 to which rabble plates 'I8 are preferably secured removably, and may be secured adjustably if desired.

The stationary hearths shown at 80 may be secured to the shell lll by any suitable'means and their upper surfaces are preferably of inverted conical shape, in order to facilitate movement of the material from the outer portion of the hearth to the central opening in the hearth. The lower surface of the xed hearths 80 may be provided with ribs, as in the case of the movable hearths, to which the beveled rabble plates 8| may be secured removably, or both removably and adjustably if so desired.

With the construction shown in Figs. 6 to 8, as also with the construction shown in Figs. 13 and 14, hereinafter described, the necessary heat for drying the material under treatment may be supplied either Aby admitting preheated air or other hot gases through the opening I4 at the base of the furnace or under some circumstances, fuel may be burned within the space at the base of the furnace or within an adjacent re box as indicated at 59 in Fig. 9, to provide the necessary heat. In cases where either of these heating arrangements is feasible, it may be unnecessary to resort to the more expensive hollow shaft and hollow hearth constructions above described. However, the constructions embodying the use of hollow shafts and hearths and heating conduits, make possible a very accurate and uniform regulation of the heating conditions throughout the furnace, which is an important advantage with certain materials and makes possible a more uniform product. A1so, of course, where the internally heated shaft and hearths are used, the heating fluid together with any products of combustion from the fuel used for heating, are kept out of contact with the material under treatment.

In the several views of the drawings only two or three hearths of each type are indicated,Y but it will be understood that a much larger number of the superposed hearths may be used in practice, the number depending upon the amount of drying action necessary with the particular material being treated. It will be also noted that in the various drawings different numbers of rabble plates and scraper arms are indicated. Where it is intended to advance the material very slowly over each hearth, only a single pair of scraper plates may be necessary in cooperation with each of the hearths. However, in most cases, it is preferable to use a comparatively large number of rabbles in connection with each hearth so as toproduce as many streams of falling material as conveniently possible and so that the material as it drops from hearth to hearth is widely distributed, whereby lall of the particles will freely contact with the ascending hot gases. That is, with the large number of the scraper plates or rabbles, the action approaches the desirable production of a substantially continuous curtain of the falling material through which the hot ascending gases must pass.

Referring particularly to Figs. 2 and 10it will be noted that the lower surfaces of the hollow hearth constructions, including also the hollow spokes 82 'of the hearths I9a, are all inclined downwardly toward the fluid outlets. This insures the rapid draining away of the condensate which might otherwise accumulate and clog the passages.

By means of the constructions shown, provision is made for facilitating the movement of the material to be dried through the furnace which includes the provision of rotatable outwardly inclined hearths alternating with inwardly inclined fixed hearths, both of which hearths may, if desired, be equipped with rabble plates, as shown,

arranged at proper angles to slowly move the material from hearth to hearth. Aczess to the various hearths may be had through doors in the shell for the purpose of replacement or adjustment of rabble teeth.

By constructing the movable and rotatable hearths after the manner disclosed in Figs. l, 2 and 5, the various hearths may be readily heated by any hot fluid such as air,r steam, oil or water. The temperatures of the various hearths, as well as of the heated air which is circulated over the hearths may be regulated and varied if desired by the use of steam valves located so as to effect the desired control. Since the temperature of the various hearths and of the circulating air may be controlled within wide limits, the furnace may be used for drying a wide variety of materials at temperatures to eiiecta proper `drying operation of the particular material. operated on. The adjustable feed scraper and rabble plates permit of controlling the rate at which the material is fed through the furnace and the length of time during which the material is on any one of the hearths.

Referring now to the construction of Figs. 1G to 12, one of the main differences between this modification and that shown in Figs. 1 to 5 is that the hearths i911, which correspond to the hearths i9 in Figs. 1 to 5, are rotatable with the shaft 2o to which they are connected by hollow spokes 82 which communicate with the hollow interior of the hearth ita and with the hollow interior of a hub 83 suitably secured to the flanged sections 28 of the shaft 20. As shown in the drawings, there may be six spokes 82 and the hub 83 may be provided with webs 84 so constructed that air descending through the shaft 20 into the hub will be directed through alternate vspokes 82 into the chamber of the hearth isa the hearths may be heated by the single stream of hot fluid circulated through the central shaft. Thus substantially uniform heating of adjacent lhearths may be easily accomplished-and controlled merely. by controlling the ow of heating fluid into the central shaft. Also with this construction the spacing between adjacent hearths may be easily and permanently fixed by designing the several shaft sections of proper length. 40

The hearth I Sa' may be-constructed of the particular shape shown, or may be of any other suitablecross sectional. shape, the upper surface of which preferably is a surface of revolution which may be horizontal or inclined inwardly toward the hub or outwardly away from the hub. The

, hearth I9a may be provided with an upwardly extending flange 85 at its outer periphery overlapping a downwardly extending flange on a circular deflecting member 86 secured .to the shell i0 lof the furnace to prevent material fed from the hearths I8 from dropping between the hearths i9a and the shell i8, and for preventing the gases from passing up around the peripheries of these hearths.

As shown in Fig. 10-scraper plates 49a adiusta-f the arm of the plate 49h maybe closed by a closure` plate 49o. y

\.Referring now to the modification shown in Figs. 13 and 14, this construction differs principally from that shown in Figs. 6, 7 and 8 in that the hearths 80a corresponding to the hearths 88 in Fig. 6 are mounted for rotation with the shaft same manner in which -the hearths 1| in Fig. 6 are held on the shaft.. The outer periphery of the hearth 80a. is preferably provided with a flange 85, as in Fig. 10, overlapping a flange Ona deflecting and sealing member 86 as in the modication shown in Fig. l0. The material is scraped olf from the hearths 'l la by scraper plates 49a and oil! the hearths 88a by scraper plates 48h, as shown.

With the constructions such as shown in Figs. 6 and 13, the heating iiuid may be most economically and effectively passed upwardly through the furnace countercurrent to the material being treated, although under some circumstances, particularly where it is desired' to have a high temperature at the top of the furnace, the heating iiuid may be forced downwardly in the same direction of flow as followed by the material treated. With the constructions such as shown in Figs. 1 and 10 for example, the heating uid within the hollow shaft and hearths may be conveniently passed downwardly and through the furnace to insure proper draining away of the condensate. However, with these constructions it will also be understood that the heating fluid might be conducted in either direction, depending upon the temperature conditions desired at the initial and final stages of the process.

While the invention has been described with respect to certain particular preferred examples which give satisfactory results, it will be understood by those skilled in the art, after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope of the invention, and] it is intended, therefore, in the appended claims to cover all such changes and modifications.

What is claimed as-new and desired to be secured by Letters Patent of the United States is:

l. In a furnace of the character described,`a hollow rotatable shaft, an annular hollow hearth, hollow spokes communicating with the hollow interior of said hearth, a hollow hub communicating with said spokes, and a web construction within said hub whereby heating fluid conducted through said shaft against said web will be directed through 'some of said spokes into the hollow interior of said hearth and returned through other spokes into said hub and said shaft.

2. A furnace construction comprising a plurality of superposed hearth members, a central vertical shaft for rotatably carrying said hearth` members, alternate hearth members being provided lwith central openings for discharging material therefrom to the succeeding hearths, means for advancing the material-over said hearths and for discharging the same through said central openings of the hearth members provided with such openings and from the peripheries of the remaining hearth members, whereby the material is advanced outwardly and inwardly respectively on alternate hearths and from hearth to hearth down through the furnace, said shaft comprising a series of hollow sections, each section extending from one hearth member to the next, the hearth lmembers over which `the material is passed outwardly as well as those over which the material is passed inwardly being formed with cavities for providing a passage for temperature controllingnfluid extending from'each hollow shaft section into the midportion of the hearth member below, thence outwardly substantially to the periphery of such hearth member, thence back t0 the mid portion'of the hearth member and into the shaft section below.

p DUDLEY BAIRD.

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