US2131665A - Rotary muffle furnace - Google Patents

Description

P. JORDAN ROTARY MUFFLE FURNACE Filed June 9, 1957 4 Sheets-Sheet 1 MMMM K AQ PAUL 4012 DAN by Ms aflorneys Sept. 27, 1938. P: JORDAN 2,131,665

ROTARY MUFFLE FURNACE Filed June 9, 1957 4 Sheets-Sheet 2 Fig.2

Lava a 18 2 3/ lnventor: PAUL. JORDAN 0 ms dfarneys' Sept. 27, 1938. P. JORDAN 2,131,665

- ROTARY MUFFLE FURNACE Filed June 9, 1957 4 Sheets-Sheet 4 .ll llllHlH Inventor: PAUL JORDAN Patented Sept. 27, 1938 UNITED STATES ROTARY MUFFLE FURNACE.

Paul Jordan, Frankfort-on-the-Main, Germany, assignor to American Lurgi Corporation, .New York, N. Y., a corporation of New York Application June 9, 1937, Serial No. 147,332

In G

15 Claims.

versely to the axis of the mufiie, or longitudinally thereto only, have already been constructed with the longitudinal joints of the mufile supported on bricks projecting from the masonry of the furnace shell. These bricks, usually wedgeshaped. have also been provided with a recess for the reception of a lug formed from projections provided on the longitudinal edges of each muflle segment.

While mufile furnaces so designed are suitable for calcination, they are not suitable for the melting of material containing metal, since the L joints could not heretofore be made tight against liquid metal.

The lack of tightness is due to the differing amounts of axial and circumferential expansion occurring in the individual structural parts. When the furnace is heated up, the masonry in the iron shell expands more than the muffle inside the furnace. The bricks projecting inward from the furnace lining, which are intended to hold the mullie in position and at the same time to calk the joints where the muffle segments abut together by their firm hold on the projections on the longitudinal edges of the muffle sections, recede more from the joints of the muffle segments, under heat expansion, than the muffle approaches under the expansion of its own bricks. Thus they are not capable of holding the projections of the muffle sections tightly together at high temperatures.

The main object of the present invention is to overcome this disadvantage, and this is accomplished by connecting the internal muffle, whether composed of a plurality of segmental parts or of one or more mutually adjacent tubular sections, directly with the shell by yielding parts, preferably in such wise that the muffle is brought into bearing with counter-bearing elements provided on the inner side of the furnace shell, by means of the yielding parts, which exert a thrust or a pull on the mufile.

For example, there may be disposed in the ermany June 10, 1936 masonry of the furnaceshell two or more rows of bricks projecting into the interior of the furnace. On the side opposite the rowsof bricks, spring plungers or similar pressure-exerting means are provided, preferably likewise in multiple-rowed arrangement, which act on the mufile and press it it against the rows of bricks. The springplungers are yielding, so that they will always hold the muffie sufficiently firmly to preclude any displacement relative to the shell, but under heavy loading they can yield, preventing'destruction of the muflleby excessive pressure. Or, the plungers or other yielding holding means are pressed againstthe muffle by springs which act between the plungers and the furnace shell. 15

In the drawings Figure 1 is a section through a mufile furnace according to the preferredembodiment of the present invention, taken along the line AB of Fig. 2;

Figure 2 is a longitudinal section through the muflle furnace;

Figure 3 is a cross-section showing details of the brick arrangement;

Figure 4 is a longitudinal section through the same;

Figure 5 is a plan view of the same;

Figure 6 is a perspective view of a from the muffle furnace;

Figure 7 is a section through Figure 8 showing a modified brick arrangement;

Figure 8 is a plan view of Figure '7;

Figure 9 is a modification of Figure 2; and

Figure 10 is an enlarged detail of a portion of Figures 2 and 9.

The mufile' in. this example is sub-divided in cross-section into five segments, as shown in Figure 1. The muflle may also be sub-divided perpendicular to the axis of rotation, so that two or 7 more tubular sections are formed, each of which 40 is composed of five segments I, constructed for example of silicon carbide. The inner lining 2 of the iron furnace shell 2a is constructed of fire clay or the like, and is provided with five ribs made of preferably wedge- shaped bricks 3, 4, and 5.

Between the shell 2a and the lining 2 there is also preferably provided a heat-retaining layer 2b, constructed for example of insulating bricks. The bricks 3 are preferably'equipped with shoes 3a, of silicon carbide for example, placed between the mufiie and the bricks, to aiford the mulfle a broader bearing surface. To guard against displacement of the shoes on the bricks, the contact surfaces preferably have a dovetail form.

piece cut The bricks 4 and 5 are preferably held in the masonry, as shown in Figures 3, 4 and 5, by disposing bricks 6 between the bricks 4 and 5 in each row; the bricks 6 are preferably also wedgeshaped. However, the bricks 6 do not completely fill the space between bricks 4 and 5 in each row, but leave spaces I free between them. The bricks 4 and 5 are of such shape that, in each row, the mutually confronting lateral surfaces of the bricks 4 and 5 are parallel to one another for one-half of the height of the brick.

In the space bounded by the parallel surfaces rise the projections 8a of the shoes 8. The shoes 8 are pressed against the internal mufile by the plungers 9, which are urged thereagainst by the springs II], the pressure of which may be adjusted by means of nuts or screw caps Illa. The shoes 3a of the bricks 3 form the counter-bearings for the mufiie, and the springs Iil insure that the muflle is always pressed against these counterbearings.

The fire ducts I8 are formed by pairs of ribs constituted of bricks 4 and 5, or 3 as the case may be, and by the muffle wall and the lining of the drum shell. The plungers can be further protected against overheating by a suitably resistant loose block I I. Instead of forming the ribs with the bricks 4 and 5, it is of course possible to make them of undivided bricks 33 provided with suitable perforation or molded-in opening 34 as shown in Figures '7 and 8, so that instead of pairs of bricks 4 and 5 single bricks are: used. The number of segments and consequently of bearing o rows and of fire ducts can of course be varied within wide limits.

The muille according to the present invention is distinguished by other advantages in addition to the reliable fastening to the furnace shell. It has the further considerable advantage that it can be made of a large number of segments or other shaped pieces, and that neverthelessthe joints, particularly those running parallel to the axis of rotation of the muflle, are dependably tight against molten materials. 'In order to insure the tightness of the joints circumferential to the muffle, additional special measures can be applied if necessary. This also can often be dispensed with, for example if the muffle is not subdivided longitudinally, or if fusion takes place in only one section of the muffle and the molten material does not reach the circumferential joints.

If sufficiently long mufile segments'are used, it is possible in many cases, by suitably inclining the furnace, to avoid having any circumferential joint touched by liquid metal, that is to say, a metal bath is formed only in the lowest section of the muffle.

But if the zone of fusion has to be greater than the possible or advantageous structural length of a mufile section, and if the calking of the circumferential joints against the fire ducts offers special difficulties, it is possible according to the invention, in order to prevent liquid metal from penetrating into the fire ducts, to use a special form of muffle segment which confines any passage of metal to those points of the circumferential joints which are located over one of the ribs formed by the bricks 3 or 4 and 5. For this purpose the sectional pieces of the muffle wall are made, for example trough-shaped.

As shown in Figure 6, the trough-shape can be obtained by equipping the sections I2 on their circumferentially running edges with inwardly extending projections or rims I4. In this manner there are formed a number of compartments corresponding to the number of consecutive sections in the axial direction. The liquid metal present in one of the compartments of the furnace can flow into the adjoining compartment only through the matched openings I3 in the abutting rims I4 of two sections or segments I2, and so long as no opening is lower than the surface of the bath it will be confined to its own compartment of the muffle.

The height of the flange-like rims I4 and the depth of the cut-outs I3 can be determined to suit the kind and quantity of metal in the compartment. The mufile segments I2 can be further reinforced with internal or external stiffeners I5, which when internal serve also as turning devices and when external improve the heat absorption.

7 When materials or mixtures are treated which are not required to be protected from contact with fire gases except at high temperatures, the furnace can also be so constructed as shown in Figure 2, so as to have one part, say the lower part in an inclined furnace, serve as muffle furnace, and the other part as direct-heated or combination-heated furnace. In such case the heating gases may be led by means of pipes II, from the fire ducts I8 of the muflle into the part of the inclined furnace which serves as preheating or drying section for the material to be treated. The pipes I! may be of heat and corrosion-resisting metal or refractory material, and when passing through the lowest point still project beyond the level of the charge. With this arrangement direct transmission of heat from the heating gas to the material treated is accomplished.

The fire ducts I8 may end over the highest pipe II as shown in Figure 9, so that the removal of the gases takes place through the furnace and the upper furnace-head. But as shown in Figure 2 it is also in many cases advantageous to pass one part of the furnace gases through the upper part of the furnace and to use another part for the external heating of the whole upper portion of the apparatus. The internal and external heating can also be effected in this case by other heating media than those serving for the heating of the muffle.

The length of the indirectly and directly heated zones of the furnace may differ greatly and will be adapted to the type of process being carried on. If for example it is desired to reduce material containing iron oxide to iron sponge or powder with the aid of gases, which are brought in for example through the conduit or pipe 40 through the lower furnace-head and through the opening 2I, it will be advantageous to have the indirectly heated zone begin at the point where the reduction from F6203 to FeO is nearly or entirely completed. 7 The reduction from FeO to Fe then follows in the indirectly heated part of the furnace, possibly at higher temperature. The gases of reduction leaving the indirectly heated zone through the pipe section I'I shown in Figure 9 are burned in the directly heated zone, mainly in the upper part thereof, air being supplied, preferably in stages, through openings 36 distributed along the length, and advantageously also about the circumference, of the furnace shell, and when so burned heat the charge to the necessary temperature.

The lower furnace-head shown by way of example in Fig. 2 can, depending on circumstances Serve for the-taking off of the metal, for the removal of residues, for the supply of heating medium, etc., or simultaneously for'several of such purposes or all of them. The metal flows'continuously, for example through the'opening's l9 pierced through a number of places in the lower end wall Isa, into the duct in the furnacehead, and which removes the metal by siphon action. If residues or slags are present which float on the metal, they can be brought out through the pipe 2| into the down-pipe 22, through which they reach the bunker 26. On the down-pipe 22 is placed the bell or cover 23, having a water trough 24 which forms a gas tight seal between the bunker and the open air. The bunker 26 can be emptied by opening the sliding ate 25.

The supply of heating medium to the fire ducts of the muffle may be received through the pipe 2'! into the annular space 30, which is closed off from the furnace by the sliding surfaces or labyrinths 28, 29 shown in Figure 10, and is connected with the fire ducts l8. The combustion air is brought into the fire ducts by way of the damper-adjustable air nozzles 31. The muille in all its various possible embodiments can also lie horizontally. In particular, when so arranged, it can be operated by charges. The gas outlets can also be located at other points of the mufile or of the fire ducts, or even of the upper directly heated portion of the furnace. If the closure 4! in Figure 9 be opened, then gas will flow out of the muffle at this point. In this way for example, a continuous operation of the muffle is possible. The muffle cross-section can be circular, oval, angular, or of other shape. This cross-section can be different at different points of its length.

The muflie furnace according to the present invention has an exceedingly manifold field of application. For example it is suitable for the melting out of metals from ashes. drosses, and other materials containing metals together with impurities; for the reduction of oxides to metal with indirect and combined indirect and direct heating; for the calcination and drying of materials which cannot be allowed to come into contact with heating gases at any but low temperatures, if at all; for the volatilization of elements, e. g., metals, or of oxides and other compounds; for the effecting of chemical reactions, such for example as chlorination and the volatilization of chlorides; and for other like uses.

I claim: i

1. Rotary mufiie furnace comprising a muffle to receive the material to be treated and a shell carrying said mufile, said furnace being heated during rotation by fire ducts disposed between the mufile and the shell, and radially yielding parts associated with said shell and muffle for directly connecting said mufiie to said shell.

2. Rotary mufile furnace comprising a muflle to receive the material to be treated and a shell having counter bearings, said furnace being heated during rotation by fire ducts disposed between the muiiie and the shell, and radially yieldable parts pressing said muffle against the counter bearings.

3. Rotary mufile furnace comprising a mufile and a masonry shell having inwardly projecting bricks forming bearings for said muflle, and radially spring pressed plungers carried by said shell urging said muifle against said bearings.

4. Rotary muffle furnace comprising a muille and a masonry shell having inwardly projecting portions, and spring pressed plungers carried by said shell for urging said muffle radially against said inwardly projecting portions, said'plungers and said portions having bearing parts, andshoes interposed between said muffle and certain of said bearing parts. 7

5. Rotary mulile furnace comprising a mufiie and a masonry shell having inwardly projecting bricks forming bearings for said muffle, shoes engaging said mulfle and carried by pairs of bricks, and plungers mounted between said pairs: of bricks and radially spring pressed against said shoes.

'6. Rotary muffle furnace comprising a mufile and a shell having counter bearings, said mufile consisting of joined sections, and spring pressed plungers carried by said shell and urging said muflle radially against said counter bearings and resiliently holding the joints together.

'7. Rotary mufiie furnace comprising a muffle and a shell having counter bearings, said mufile consisting of joined sections having inwardly directed annular projections, and resilient means carried by said shell urging said muffle against said counter bearings.

8. Rotary mufile furnace comprising a muffle and a shell having counter bearings, said muflle consisting of sections having interfitting joint surfaces, and resilient means carried by said shell radially urging said muflie against said counter bearings and thereby tightening said joints.

9. Rotary muffle furnace comprising a muflie and a shell having counter bearings, and spring pressed plungers carried by said shell urging said muflle against said counter bearings, said mufiie having inwardly directed annular projections interrupted at points where the muilie rests on said counter bearings.

10. Rotary muffle furnace comprising a muffle and a shell having counterjbearings, and yieldable means pressing said muffle against said counter bearings, the inner surface of said shell,

the outer surface of said muflle, and the lateral surfaces of said counter bearings defining fire ducts for said furnace. V

11. Rotary muffle furnace comprising a muffle having longitudinal ribs, and a shell having counter bearings, and spring pressed plungers carried by said shell and urging said muflle against said counter bearings.

12. Rotary muffle furnace comprising a muffle constructed of heat and corrosion resisting metal, a shell having a refractory lining with inwardly projecting portions forming counter bearings, and radially yieldable means carried by said shell pressing said muflle against said counter bearings.

13. Rotary furnace comprising a muille and a shell having a lining and counter bearings, and yieldable means pressing said mufile against said counter bearings, the inner lining of said shell, the outer surface of said muille, and the lateral surfaces of said. counter bearings defining fire ducts, said furnace having a part constructed and arranged for direct heating and connected to said muffle, and means for passing heating medium into the interior of said furnace between said fire ducts and said part constructed and arranged for direct heating and connected to said muifle.

14. Rotary furnace comprising a muffle and a shell having counter bearings, and yieldable means pressing said muffle against said counter bearings, the inner surface of said shell and the outer surface of said muifle and said counter bearings defining fire ducts, said furnace having a part constructed and arranged for direct heatfurnace have a part constructed and arranged for direct heating and connected to said muffle, said furnace having separated outlets for the removal of solid, liquid and gaseous substances.

PAUL JORDAN.

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