US1685226A - Heating high-temperature apparatus - Google Patents

Description

sept. z5, 192s. 1,685,226

C. L. BURDICK HEATING HIGH TEMPERATURE APPARATUS Filed June 25, 1926 /6/ INVENT R BY QM .'l ,wml/)Www M ATTORNEYS Patented Sept. 25, 1928.

UNITED STATES 1,685,226 PATENT OFFICE.

CHARLES LALOR BURDICK, OF NEINl YORK, N. Y., ASSIGNOR T GUGGENHEIM BROTHERS, 0F NEW YORK, N. Y., A. GOPABTNERSHII'.

4fnnnzriivci HIGH-TEMPERATURE APPARATUS.

Application led June 25, 1926.

'.l'his invention relates to high temperature apparatus such as furnaces and more particularly metallurgical furnaces. The invention has for its object the `provision of improved electric heating for such hightemperature apparatus, and more particularly kthe invention aims to provide improved electri-c heating vfor metallurgical furnaces of the multiple hearth type. Y

Heretofo're, one of the chief difficulties with electric heating elements for metallurgical furnaces and the like has been their i-naccessibility so that when replacements were re l qui-red, it has been necessary to interrupt the operations of the furnace. Moreover, the

usual materials of whichheating elements are' made will not withstand the corrosive action of certain gases and materials introduced or generated within the furnace.

The present invention contemplates the provision of an improved electric heating unit for metallurgical furnaces, andv more particularly for circular furnaces such as the multiple hearth furnaces. In accordance with the invention the electric heating or resistance element is enclosed within a protective tube and suitably mounted within the furnace# The arrangement of 'support is such that in case'any replacement is required, either the entire tube and element may be taken out and andther complete unit put in its place, or if only thelheating element requires renewal, the element may be withdrawn from the tube and another put in its place. A plurality of these heating units in the same furfnace may be connected'electrically in series or in parallel, and the renewal, in whole or in lpart, of a single unit can be easily made without interfering with the operation of the '40v furnace.

, The heating units of the invention are particularly applicable to multiple hearth furnaces, sluch as the Wedge or MacDougal furnaces. In these furnaces, the hearths are so arranged that. there is no opportunity for repair work within the furnace while operating at high temperatures and for this. reason electrical heating has not heretofore been considered practicable.

The novel features of the invention will be best understood from the followingy description taken in conjunction with the ac-' companying drawing, in which Fig. 1 is a sectional elevation of a single hearth. or heating chamber in a. multiple Serial No. 118,413.

hearth furnace provided with the improved electrical heating means ofthe invention;

Ifig. 2 is a cross section of the furnace of rgenerally along the section line lposed shaft 3 extends vthrough appropriate central openings in the hearths and is adapted to be rotated by an appropriate source of power (not shown). i

'.lhe shaft 3 carries radially disposed arms 4 positioned above each of the hearths. Flows or serapers 5 are attached to the arms 4. The plows 5 are arranged to move the charge on adjacent hearths in opposite dire'c tions towards appropriate discharge openings. such as 6 and 8 in Fig. l.

In accordance with my present invention, a plurality of electric heating units 9 are radially disposed in cach heating or working' chamber 7 of the furnace, and hence above each of the superposed hearths. The hea-ting units extend through appropriate openings inthe cylindrical side wall of the furnace 'and are supported within the furnace by hangers or brackets 10. A removable bushing or other appropriate packing means 13 seals the space between the outer end of each heating unit and the furnace wall.

The heating unit com-prises a protective tube or casing 14 within'whiclris appropriatcly mounted the electric heating element 16. The heating element is supported within the protecting tube by insulating discs 15, of porcelain, lava rock, asbestos fiber, or other appropriate material. The terminals 11-12 f of the heating element extend beyond the .open end of the tube 14 and are appropriately connected to the source of electric energy. In Fig.l 2 of the drawing, the sin heating elements 1G are electrically connected in series and to the source of electric energy (not shown).

The heating element 16 is spaced from the interior walls of the enclosing tube 14." The element is so constructed as to generate a progressively increasing amount of heat from the center towards the periphery of the heating chamber. In a circular furnace, if the heating element throughout the length of the protect-ing tube be of uniform construction, more heat Will be generated and dissipated per square foot of hearth area near the center of the furnace than at the circumference. In order to obviate this difficulty and to maintain a uniform temperature over the entire` hearth, the number of coils per foot of the heating element are in proportion to the distance from the center of the furnace. For example, a heating element supported radially within a twenty-foot diameter furnace would have ten coils or turns of resistance Wire or ribbon per footat the `circumference and five turns per foot at a dist-ance of five feet from the center and three turns at a distance of three feet from the center. T he actual number of turns or coils will vary with the amount of heat, size of Wire, temperature required, etc., and the example just given is merely to shovvl that the area to be heated under the element is proportional to the distance from the center of the furnace and that the variation in the number of turns or coils Will vary in this same proportion or in an otherwise compensated manner.

The Wire or ribbon swerving as the resistance or heating element 16 is so mounted that no part of itv touches the protecting tube let. The material for the heating elements may be of any of the standard metals or alloys as,l

for instance, nichrome Wire or ribbon. The protecting tubes are made of any material that will withstand the temperature and the harmful effect of gases, dust, and other materials present in the heating chambers during the operation of the furnace. Tubes made of 30% ferro-chrome have been found satisfactory for' use in the reduction of certain metallic oxides, the metals from which react or alloy with iron or copper etc. 'Ihe tubes may also be made of quart-Z, carborundum, and other appropriate refractories.

The heating units of the invention are of particular advantage in multiple hearth furnaces, as Well as in other furnaces in which the hearth is circular. Thus, the Aheating units are conveniently supported Within the furnace and may be'conveniently removed, in Whole or in part, when replacements are necessary, Without interfering with the operation of the furnace. Moreover, the heating elements are of such construct-ion and so arranged that the circular hearth is uniformly heated over its entire area by the heat generated in and dissipated tothe hearth by radiation and by conduction through gases. The

invention permits the use of the multiple hearth furnace in operations for which it was heretofore unsuited, as, for example, the reduction of metallic oxides, such as tin oxide, either by gaseous reduction or by solid reducing agent.

I claim:

1. The combination with a high temperature apparatus having a heating chamber of circular section of electric heating units comprising a plurality of elongated electric heating elements each radially disposed in said chamber and of such construction that the amount of heat generated by said element progressively increases from the center towards the perphery of said heating chamber.

Q. rI`he combination with a multiple hearth furnace having substantially circular heating chambers, of a plurality of electric heating units radially disposed in each of said chambers, each of said units comprising an electric heating element mounted Within a protective casing of heat refractory material, the heating element being removable from its' protective casing and from the furnace and the heating unit being removable as a whole from the furnace Without interrupting the operation thereof.

3. The combination with a multiple hearth furnace having substantially circular heating chambers, of a-plurality of electric heating units radially disposed in each of said chambers, each of said units comprising an electric heating element mounted Within a protective casing of heat-refractory material, the heating element being removable from its protective casing and from the heating chamber and the heating unit being removable as a whole from the heating chamber Without interrupting the operation of the furnace, said heating elements being of such construction that the amount of heat dissipated therefrom progressively increases from the center towards the periphery of the heating chamber.

4. A heating unit comprising a helical coil of gradually increasing pitch from one end to the other mounted within a casing of heat refractory material in spaced relation to the walls of said casing.

5. A furnace comprising a series of superposed heating chambers, and a plurality of heating elements mounted within each chamber adjacent the top thereof and extending from points adjacent the side Walls to the centraly portion of the chamber.

In testimony whereof I affix my signature'.

oHARLEsLALoR BURDICK.

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