US2374742A

US2374742A - Electrically heated drum-type furnace

Info

Publication number: US2374742A
Application number: US496797A
Authority: US
Inventors: Gallusser Hans
Original assignee: Individual
Current assignee: Individual
Priority date: 1942-06-22
Filing date: 1943-07-30
Publication date: 1945-05-01
Anticipated expiration: 1962-05-01

Description

y 1, 1945- H. GALLUSSER ELECTRICALLY HEATED DRUM-TYPE FURNACE Filed July 30, 1943 lFaienied May 1,1945

ELECTRICALLY HEATED DRUM-TYPE FURNACE Hans Gallusser, Geneva, Switzerland Application July 30. 1943, Serial No. 496,797 In Switzerland June 22, 1942 3 Claims.

Drum-type furnaces are generally employed for performing chemical reactions between solid and gaseous bodies. In the case of an exothermic reaction, the heat created may be used I for maintaining the temperature necessary for the reaction within the furnace, whereas for an endothermic reaction, the heat required for the reaction as such as well a the heat-losses of the furnace must be replaced. I

In known drum-type furnaces it has been tried to generate the necessary heat by means of electrical resistances mounted within the furnace. This however did not prove successful, because such resistances deteriorate too quickly. For this reason, this method of heating cannot be practically applied, especially not for high temperatures of reaction, such as 900-1100 C.

It has also been tried to generate the necessary heat within the furnace by means of electrical arcs. This method of heating however cannot be employed for reactions requiring even and exactly constant temperatures, because of the too high temperature of the arc, because of the danger of sintering, because of uneven heat-distribution and because of the impossibility of accurately regulating the temperature by means of electrical arcs,

The present invention concerns an electrically heated drum-type furnace which eliminates the afore-mentioned disadvantages. It is of the known rotating type and has aslightly inclined longitudinal axis and differs from the known drum-type furnace inasmuch as it is provided over at least one part of its length with electrical transformers. The wired core-legs of the latter penetrate the furnace and its secondary consists of a metallic cylinder, preferably of iron, which forms a part of the inner wall of the furnace.

This arrangement makes it possible, to generate the heat in great beating-surfaces, the temperature of which can be accurately regulated and controlled. Due to the great heating-surface within the furnace, the heat is evenly distributed from the inside towards the outside so that there exists a relatively small temperature-difference between the heating element and the heated body. For this reason, dangerous overtemperatures cannot exist, provided that the temperature has been correctly regulated in the first place.

The drawing attached show schematically an example of this invention for a three-phase alternating current system. 7

Figures 1 and 2 show a heating element in ionsitudinal and in cross-section.

Fig. 3 shows on smaller scale a drum-type furnace with two heating elements according to Figs. 1 and 2.

The body A of the heating element is cylindrical and consists of an outer envelope i, a layer 2 of heat insulating material and an inner mantle 3. The body A is provided with a magnetic core 4 for a three-phase alternating current system, which is'arranged in such a way, that its primary windings '8 are wound upon the core-leg 5 which penetrates the cylinder diametrically. Each core-leg 5 is located within a protecting tube 1, open at both ends and subdivided electrically in the direction of its longitudinal axis, this protecting tube I. being surrounded by a layer of heat-insulating material a. Thi layer a is located between the protecting tube 1 and a closed. metallic mantle 9, preferably of iron, which forms the secondary of the transformer and at the same time a part of the interior wall of the furnace. Over one end of each core-leg 5 of the magnet core 4 there is provided a ventilating fan ill for the purpose of cooling the primary windings 6 and the core-leg 5.

The body A is provided with spur-rings ii around its circumference, by means of which it bears against spur-wheels l2 and isthu able to execute a. rotating movement.

Fig. 3 shows a drum-type furnace composed of two heating elements A and the two pre-heaters B and C. These latter consist each of a cylindrical body with an outer envelope, an inner mantle and a layer of heat-insulating material arranged between the outer envelope and the inner mantle.

As will be noticed from the drawing, the two pre-heaters have a smaller diameter than the heating elements.

The body A, B, C of the furnace is slightly inclined towards the horizontal plane and the transformers of the two heating elements A are displaced with respect to each other.

The two open ends of the furnace are arranged rotatably in two stationary bearings I 3, It, the latter being provided with stuffing means to prevent leakage of gas during rotation. Each bearing l3, it forms part of a closed hollow body It, viz IS. A gas-intake I1 is connected to the hollow body I, whereas a gas-exhaust i8 is connected to the hollow body IS.

A canal or chute 20 communicating with the hopper l9 protrudes into the open end of the preheater C.

The lower part of the hollow body I! forms a hopper and is connected to the chute 2| which in turn communicates with the storage-bin 22.

The transformers are fed over slip-rings 28 mounted on body C.

The furnace according to this invention functions as follows:

When energizing the primary windings 6, an induction current is produced in the metal-cylinder 9, heating the latter. Because of- 'it being electrically subdivided, no induction-current is induced'in the protection tube 1. The heat generated is transmitted to the interior of the drumtype furnace. By means of regulating the voltage, the temperature in the interior of the furnace may be adjusted to the desired value. On the left side the gas is carried to the furnace by means of the gas-intake l1. It then flows through the furnace and leaves the same at the right hand side -by means of the gas-exhaust H3. The ma= teriai to be heated reaches the furnace on the right hand side by means of the chute 2| and the hopper l9. As a consequence of the heating and of the rotation of the furnace the material.

to be heated will slowly wander through the furnace in the direction towards the left hand side and leaves the furnace again through the chute 2| to reach the bin 22.

In the pre-heater C the material is pre-heated by means of the hot gases coming from the heating elements A. The temperature, necessary for the reaction is reached within these heating elements. At its intake side in the pre-heater B, the gas is also heated by means of the hot material leaving the heating elements. This same gas is then heated to the temperature of the re action within the heating elements in order that the chemical reaction may take place.

It is to be noted, that the furnace is rendered sufficiently tight at both ends by means of the material filling the chutes 2B and 2| as to permit the use of light gases, such as hydrogen, without danger of leak-losses. In the arrangement according to this invention, the heat-losses are at a minimum.

The body of the furnace may naturally also consist of more than two heating elements A. and the transformers may be designed for singleor multiphase operation.

What I claim is:

1. In an electric furnace. a cylinder through which material to be treated extends axially, means for rotating said cylinder about its axis, said cylinder having an inner liner of metal, a tube extending transversely through the cylinder, an electromagnetic winding having a core located in said tube and serving as the primary of an induction heater, the secondary of which is comprised 'by the cylinder liner, and means for supplying electricity to the primary windings during rotation of the cylinder.

2. In an electric furnace, a cylinder through which material to he treated extends axially, means for rotating said cylinder about its axis, said cylinder having an inner liner of metal, a plurality of tubes extending transversely through the cylinder, electromagnetic windings having cores located in said tubes and serving as the primary of an induction heater, the secondary of which is comprised icy the cylinder liner, and means for supplying electricity to the primary windings during rotation of the cylinder.

3. In an electric furnace, a cylinder through which material to he treated extends axially, means for rotating said cylinder about its axis, said cylinder having an inner liner of metal, a tube extending transversely through the cylinder, an electromagnetic winding having a core located in said tube and serving as the primary of an induction heater, the secondary of which is comprised by the cylinder liner, means for supplying electricity to the primary windings during rotation of the cylinder, and a preheating chamber connected gas tightly at an axial end of said 40 cylinder.