US 3510115 A
Description (OCR text may contain errors)
May 5, 1970 FQEX ETAL 3,510,115
ROTARY MELTING FURNACE WITH PERIPHERAL COOLING MEANS Fil ed Feb. 2, 1968 2 Sheets-Sheet 1 F I INVENTOR HE/ A BMW/7mm RIBCMT 1161/7/75 MM: F051; 24w? meoz/r/ou/l/ BY (v at/6 4466 ATTORNEYS M. FOEX ETAL May 5, 1970 ROTARY MEL'I'ING FURNACE WITH PERIPHERAL COOLING MEANS 2 Sheets-Sheet 2 Filed Feb. 2. 1968 QNQE INVENTOR 175V!!! W W/44m; Awe-:7 2507 MMC F225?" ATTORNEY United States Patent Int. Cl. li27b 7/08 US. Cl. 26333 Claims ABSTRACT OF THE DISCLOSURE A rotary melting furnace comprising a rotary cylindrical shell having a horizontal axis and two conical extremities pierced by axial openings, a stationary casing which surrounds said shell, systems for cooling said shell by means of a cooling fluid and means for driving said shell in rotation. The cooling systems comprise spray tubes disposed around the periphery of the shell in axially parallel relation thereto and tube sections which terminate at the conical extremities of the shell, the liquid which has served to cool the conical extremities of the shell being recovered by centrifugation and caused to run over the cylindrical portion of the shell.
The present invention relates to a rotary melting furnace fitted with rotation and cooling systems designed to obviate any further need for flexible seals, the coefficients of friction of which give rise to considerable losses of mechanical power While also limiting the production capacity of the furnace. The systems under consideration do not set any limitation either on the capacity or the dimensions of the furnace and accordingly permit the construction of rotary furnaces on an industrial scale.
In point of fact, in rotary furnaces which are heated by thermal sources to high temperatures (solar heat, plasma torches or any other high-temperature heat generator), the charge of material to be melted and/or partially sintered fills a metallic vessel of circular section provided with a jacket in which a consequent stream of cooling water or any suitable cooling liquid is circulated.
In furnaces of this type, the thermal flux penetrates into a central cylindrical cavity of small diameter which is formed along the refractory material and begins to melt this latter at the surface as soon as the melting temperature is reached. The need to obtain high temperatures (of the order of 3000 C.) within the material and even higher temperatures within the heat sources entails a very high thermal flux. In order that the metal jacket or casing which contains the charge of refractory material to be melted should be protected from the melting process, two solutions are contemplated.
In the first solution, provision can be made for an annular thickness of charge which is such that the temperature of the non-cooled metallic wall is maintained in the vicinity of 80 to 100 C., thereby making it possible to operate the furnace without disturbing the human or material environment. But in this case, this annular thick ness would vary according to the thermal conductivity of the material to be melted since the value of this latter at high temperature can fluctuate within a ratio of 3 to 4:1 in the case of refractory oxides. In addition to substantial thicknesses of refractory materials, it would therefore be necessary to employ metallic cylinders having a diameter which Would correspond to the nature of the material to be melted. These two added difficulties there- Too fore preclude the use of this system which is of limited practical interest.
On the other hand, the second solution which consists in cooling by circulation of water or any other suitable coolant the cylindrical metal jacket or casing which contains the charge of refractory material to be melted permits the use of a single metallic shell having a fixed diameter. However, said shell must rotate at relatively high speeds (250 to 500 revolutions per minute) in order that the molten material should be retained under the action of centrifugal force on the wall which is still in the solid state and which is in turn caused to melt by said material. But in this case, at such angular velocities, the linear velocities of the metallic shell increase considerably with its radius, that is to say with the quantity of molten materials produced by the rotary furnace.
However, the liquid coolant contained within a rotating metal jacket of this type must be admitted into the double wall which constitutes said jacket, then be discharged therefrom through stationary supply tube sections which are placed at its periphery and connected by means of flexible seals. An arrangement of this kind results in substantial friction which increases with the diameter of the furnace and therefore with its production capacity. The friction referred to becomes not only a source of considerable loss of mechanical power for driving the furnace in rotation but also sets a limitation on any increase in production capacity on an industrial scale, as could readily be calculated from the angular velocities mentioned above and with the coefficient of friction of known seals.
The present invention makes it possible to overcome this loss of power and especially the limitation which would be imposed on the volume of production of this type of furnace. In fact, the rotation and cooling systems with which the furnace according to the invention is equipped make it possible to dispense with flexible seals.
More specifically the rotary melting furnace according to the present invention which comprises a rotary cylindrical shell having a horizontal axis and two conical extremities pierced by axial openings, a stationary casing which surrounds said shell, systems for cooling said shell by means of a cooling fluid and mean for driving said shell in rotation, is characterized in that said cooling sys tems comprise at least one annular zone which is concentric with the moving shell, said annular zone being connected to a pipe for the admission of the cooling fluid and adapted to communicate on the one hand with spray tubes disposed around the periphery of the shell in axially parallel relation thereto and on the other hand with tube sections which terminate at the conical extremities of the shell, the liquid which has served to cool said conical ex tremities of the shell being recovered by centrifugation and caused to run over the cylindrical portion of the shell.
Further properties and advantages of the present invention will become apparent from the following description of one embodiment of said furnace which is given by way of explanation but not in any sense by way of limitation,
reference being made to the accompanying drawings, in
FIG. 1 illustrates the melting furnace in accordance with the invention;
FIG. 2a illustrates the furnace together with its fixing assembly;
FIG. 2b is a top view of the furnace which is equipped with four plasma torches.
The furnace in accordance with the invention as shown in detail in FIG. 1 comprises a moving unitary casing 1 which has the shape of a horizontal cylinder, an axis of rotation 00' and two conical extremities. There are formed at the center of said extremities circular openings 2 and 3 which are employed for the purpose of heating the furnace and pouring molten refractory materials which may also be refined. A second stationary casing 4 surrounds the moving portion 1. The movement of rotation of said moving portion about the axis with respect to said stationary casing is carried out by means of two ball-bearings 5 and 6 which are disposed at each extremity of the cylinder.
The cooling fluid (such as water, for example) is admitted at the top of the stationary casing 4 through tubes such as the tube 7 which feed two annular zones 8 and 9. Said zones serve to distribute the cooling fluid on the one hand to spray tubes 10 which are disposed around the periphery of the moving casing and parallel to its axis and, on the other hand, to short tubes 11 which open onto the terminal conical portions of the cylinder.
At the axial center of the furnace, there is located a free zone 12 in which the plasma is heated (primarily by radiation) and which is followed in the direction of the casing 1, first by a fusion zone 13, then by a gradual and decreasing-sintering zone 14.
The moving casing 1 is driven in rotation about the axis 00' by means of a gear system consisting of a pinion 15 (the driving means having been omitted from the figure) and a ring gear 16 which is rigidly fixed to the casing 1.
The cooling liquid is discharged at the base of the apparatus through an opening 17.
The cylindrical portion of the furnace is powerfully cooled by means of the spray tubes 10, then by the cooling liquid which is caused to flow upwards by centrifugation from the terminal conical portions, then runs over the metallic cylinder 1.
The cooling liquid which serves to cool the terminal conical zones by means of the short tubes 11 flows up under centrifugal action without any need to provide seals at 18 which would absorb a substantial amount of mechanical energy. Cylindrical assemblies such as 19 for the rotating portion of the furnace and cylindrical assemblies such as 20 for the cooling spray tubes make it possible to increase the length of the furnace if necessary and therefore to increase its production capacity.
In FIG. 2a, the furnace which is illustrated diagrammatically at 21 is mounted in clamping collars 22. The furnace is balanced by means of a counterpoise 23 constituted by the motor set from which the furnace is driven in rotation. The complete assembly is fixed on a column 24 which permits of azimuthal position-setting. The column is in turn fixed on a conventional frame 25 which permits of positional adjustment.
In the case of heating of the furnace by means of plasma torches 26, FIG. 2b shows the arrangement which can be adopted for said torches.
It will be understood that the present invention has been described in the foregoing by way of explanation but not in any limiting sense and that any detail modifications can be contemplated without thereby departing either from the scope or the spirit of the invention.
What we claim is:
1. A rotary melting furnace comprising a rotary cylindrical shell having a horizontal axis and two conical extremities pierced by axial openings, two outer members secured to said conical extremities defining two outer chambers, a stationary casing which surrounds said shell, systems for cooling said shell by means of a cooling fluid and means for driving said shell in rotation, characterized in that said cooling systems are stationary and comprise at least one annular zone which is concentric with the moving shell, said annular zone including a plurality of pipes for the admission of the cooling fluid to a plurality of spray tubes disposed around the periphery of the shell in axially parallel relation thereto and to a plurality of peripheral tube sections within said outer chambers which open at the conical extremities of the shell, the liquid which has served to cool said conical extremities of the shell adapted to be recovered by centrifugation through said outer chambers and caused to run over the cylindrical portion of the shell, and means communicating with the lower part of said zone to discharge said liquid.
2. A rotary melting furnace in accordance with claim 1, characterized in that the rotary cylindrical shell and the spray tubes consist of, at one of the extremities thereof, replaceable pieces whereby the production capacity of the furnace may be varied.
3. A rotary melting furnace in accordance with claim 1, characterized in that the moving shell is rotatably mounted inside the stationary casing on ball-bearing raceways.
4. A rotary melting furnace in accordance with claim 1, characterized in that the means for driving the shell in rotation comprise a driving pinion which is adapted to cooperate with a ring gear which is rigidly fixed to said shell.
5. A rotary melting furnace in accordance with claim 1, characterized in that said furnace is mounted in clamp ing collars and balanced by a counterpoise on a fixing column which permits of positional adjustment of said furnace.
References Cited UNITED STATES PATENTS 644,926 3/1900 Kelling et a1. 164297 X 939,817 11/1909 Edison. 3,257,196 6/1966 Foex 266-33 X FOREIGN PATENTS 182,488 7/1955 Austria. 8,768 2/ 1957 Germany.
ROBERT D. BALDWIN, Primary Examiner U.S. Cl. X.R.