US2182218A

US2182218A - Furnace for heating

Info

Publication number: US2182218A
Application number: US225125A
Authority: US
Inventors: James C Woodson
Original assignee: Lee Wilson Engineering Co Inc
Current assignee: LEE WILSON ENGINEERING Co; Lee Wilson Engineering Co Inc
Priority date: 1938-08-16
Filing date: 1938-08-16
Publication date: 1939-12-05
Anticipated expiration: 1956-12-05

Description

Dec. 5, 1939. J c WOODSON 2,182,218

FURNACE FOR HEATING Filed Aug. 16, 1938 2 Sheets-Sheet l INVENTOR James C. WoodSon Dec. 5, 1939. r J c. w ooDsbN 2,182,218

FURNACE FOR HEATING Filed Aug. 16, 1938 2 Sheets-Sheet 2 WW AW Av 30 I INVENTOR James C. Woodson Patented Dec. 5, 1939 UNITED STATES PATENT OFFICE FURNACE FOR HEATING Application August 16,

3 Claims.

This invention relates generally to the heating of materials in furnaces and has particular reference to a furnace for and method of heating materials such as strip metal in coils.

The annealing of strip steel in coils has now become the accepted practice in the industry. Various methods and apparatus have been devised for expediting this step in the processing of sheet steel, but the operation remains a costly and time-consuming one at best. I have discovered that heat supplied to strip in coils penetrates the interior of the mass largely by conduction inwardly from the edges; i. e., axially of the coil, instead of radially thereof through the layers formed by the successive turns of the coil. Following up this discovery, I have invented a novel furnace and method particularly adapted for heating strip in coils.

In a preferred practice of the invention, I

subject the sides of the coil to direct radiation and supply heat to the ends of the coil by convection and conduction. The apparatus which I have invented for carrying out this method comprises a furnace having a hearth, side walls, and

a roof with heat exchange tubes mounted interiorly thereof, preferably in spaced relation along the side walls. In order to increase the radiation surface, I form the tubes of hairpin shape and mount them so they extend upwardly along the side walls and then downwardly thereof. Burners supply fuel to the tubes for combustion therein. Openings in the tubes adjacent the ends remote from those into which the bumers extend allow the combustion gases to be dis- 85 charged into the interior of the furnace after passing through the tube. An exhaust duct below the hearth and suitable connections thereto permit ,these gases to be drawn over the coil which is disposed on a support spaced above the hearth,

to supply heat to the edge of the strip by convection and conduction.

The following detailed description of the invention refers to the accompanying drawings illustrating a preferred embodiment and practice of the invention. In the drawings Figure 1 is a partial longitudinal section through one form of furnace constructed in accordance with the invention, for the practice of the method herein disclosed; and

Figure 2 is a transverse section through said furnace.

Referring now in detail to the drawings, a furnace I0 of the so-called cover type comprises a base i I forming a hearth and a heating cover I2. 65 The base is composed of refractory brick I3 laid 1938, Serial No. 225,125

up on a bottom sheet I4 supported on structural frame members l5. The base is disposed on any suitable foundation or. working floor IS.

The cover I 2 comprises side walls I! and a roof l8 which are also built up on refractory brick 5 within a housing formed by structural frame members I9 and sheathing plates 20. The cover is removably disposable on the base II, the lower edge of the cover being provided with a bearing plate 2| adapted to rest on the top flange of a 10 beam 22 extending along the sides of the base. A sealing channel 23 also extends around the sides of the base and is adapted toreceive a sealing flange 24 depending from the bottom edges of the cover. 15

Charge supports 25 are carried on the base and spaced slightly thereabove by pillars 26. The supports 25 may conveniently be in the form of heavy cast metal discs and preferably having a peripheral sealing channel 21. The pillars 26' permit the circulation of high combustion gases under the charge support for heating the latter by convection as will be explained further hereinafter. A plurality of supports 25 may be arranged on the base in one or more rows, depending on the desired capacity of the apparatus. The supports 25 are adapted to receive charges of material to be heated in the form of coils such as that indicated at 28. The coils are disposed on the supports while the heating cover I2 is removed from the base H. Protective covers 29 are disposed over the individual coils with their lower edges seated in the channel 21. These covers protect the coil from atmospheric oxidation on removal of the heating cover after the coils have been heated to the desired temperature for annealing. The heating cover, of course, is lowered over the coils and protective covers and deposited on the base to effect such heating. Pipe connections 30 extend inwardly and upwardly through the base I! and the supports 25 for supplying a non-oxidizing atmosphere in the space within the covers 29.

Heat exchange tubes 3! are mounted in spaced relation along the side walls H for radiating heat 4,5 to the tubes 29 and thence to the coils 28. The tubes 3| are preferably of hairpin shape as shown and have elbows 32 at one end extending outwardly through the side walls ll. As shown, the tubes are mounted substantially vertically. 50 Burners 33 extend into the elbows 32 for supplying fuel thereto for combustion with air induced into the tubes. The burners are supplied from manifolds 34 and each burner has a control valve 35 as well as a spark gap igniter 36. A string thereon by the suspension 32a and a hook adapted to engage the bend in the tube. The ends of the tubes 3| remote from those into which the burners 33 extend are open to permit the high combustion gases to be discharged into the space within the heating cover I! after traversing both legs of the tubes.

An exhaust duct 31 extends longitudinally of the furnace beneath the floor "5. Connecting pipes 38 extending through the base II and depending therefrom cooperate with ports 39 branching from the duct 31. Annular sealing cups 40 extend around the ports 39 and receive the lower ends of the pipes'38. By means of these pipes and the duct 31, the hot combustion gases discharged from the open ends of the tubes 3| blow around the protective covers 39, under the charge supports 25, and thence downwardly through the pipes 38 to the duct 31 to a suitable discharge stack.

As will be apparent from the foregoing description, the tubes 3| are heated to radiant temperature by the combustion of gases therein and supply heat by direct radiation to the covers 29 which, when sufliciently heated, radiate heat to the sides of the coils 28. This heat soaks into the coil radially thereof by passing through the layers formed by the successive turns of the coil. The hot combustion gases discharged from the open ends of the tubes 3| and flowing under the supports exhaust heat to the supports by convection and the latter transmit-heat directly to the coilsby conduction. This heat soaks upwardly through the coil by conduction axially thereof from the lower edge of the coil toward the upper edge. The downward flow of the combustion gases also has the effect of heating the refractory brick composing the hearth or base II to a temperature such that they radiate heat to the charge supports for conduction into th coils.

The invention thus provides a method and apparatus for heating coils more efiiciently than anything of the kind known previously with which I am familar. The tubes 3|, being of hairpin shape, present a substantial radiating surface for delivering heat to the coils at the sides thereof. It will be understood, of course, that the tubes 3| also radiate heat to the refractory lining of the side walls which, on being heated sufliciently re-radiate such heat through the coils. By heating the coils from the lower end thereof by convection and conduction, furthermore, the heating stage of the annealing cycle is expedited considerably, reducing the time and fuel consumption heretofore involved in this operation and increasing the production obtainable with a given amount of equipment.

Although I have illustrated but a preferred embodiment and practice of the invention, it will be understood that changes therein may be made without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. A metallurgical furnace comprising a base covered with a refractory layer, a charge support on said base, means mounting said support in vertically spaced relation to said base, an outlet through said layer below said support, a cover disposable on said base, said cover having substantially vertically disposed hairpin-shaped heat-exchange tubes mounted on the inner surface of the wall of the cover, each tube having a burner in one end and an opening near the other, whereby hot combustion gases traversing said tubes heat a charge on said support by radiation and flow under the support to said outlet thereby heating the support by convection.

2. In a furnace, a base, a charge support mounted on said base and spaced thereabove, a cover removably disposable over said base and support, hairpin-shaped heat-exchange tubes mounted on the inner surface of the walls of said cover, burners extending into said tubes, said tubes having openings therein whereby the hot combustion gases traveling therethrough are eventually discharged into the interior of said cover, and an outlet for said gases below said support and extending through said base, whereby the outfiowing gases sweep across the lower surface of said support.

3. An annealing furnace comprising a base, a charge support, means mounting said support in spaced relation to said base, an outlet through said base below said support, a cover disposable on said base, a plurality of hairpin-shaped heatexchange tubes mounted on the inner surface of the wall of said cover, a burner in one end of each tube and an opening adjacent the other end whereby combustion gases after traversing said tubes are discharged into said furnace and flow across the lower surface of said support and through said outlet.

JAMES C. WOODSON.