US2086972A - Furnace - Google Patents

Description

July .13, l957- L.. wlLsoN Y 2,086,972

' FURNAGE Filed May 51, 1935 i 2 sheets-shea 1 July 13, 1937. L. WILSON 2,086,972

FURNACE Filed May 51, 1935 2 Sheets-Sheet 2 2 FJ-rig. 3. 5 20 `40 to the combustion chamber.

Patented July `13, 1937 UNITED STATES PATENT OFFICE FURNACE Lee Wilson, Cleveland, Ohio Application May 31, 1935, Serial No. 24,266 2 claims. '(Cl. 26e-5) My invention relates to metallurgical furnaces and, in particular, to furnaces especially adapted for annealing.

In my prior Patent No. 1,952,402, I have dis- 5 closed an annealing furnace for annealing steel sheets, for example, which is indirectly heated by combustion gases traversing heat-exchange tubes mounted therein. It is common practice, in using a furnace of that type, to place a charge l of material to be annealed on the base of the furnace after removing the bell or cover. A heatconducting inner cover is then placed over the charge and the furnace cover itself finally lowered into position..

l It has been thought impractical heretofore to heat a ,furnace of the bell or cover type directly by contact of combustion gases discharged therein with the charge of material, because of the rapid deterioration of the inner covers when subjected ,no directly to the scouring effect of the jet of hot combustion gases discharged by the ordinary gas burner.

I have invented a furnace operating on the principle of directly heating the charge by hot" in a space apart from that defined by the innerv 0 walls of the cover, and circulate the gases from the combustion space into contact with the inner cover enclosing the charge. vI further withdraw gases from the interior ofthe furnace after passing over the inner cover, and mix-.them with the fresh combustion gases being delivered into the furnace to reduce slightly the temperature thereof and thereby prevent excessive deterioration of the inner-cover. If the fuel employed is blast furnace gas or producer gas, I supply it direct If natural gas is employed, I supply it rst to a partial combustion zone with a limited supply of air. The gas burns 'partially there with a luminous flameand then passes over into a complete combustion zone where 45 additional air is supplied forfurther combustion e 50 the flow of such gases upwardly around the inner cover, to prevent overheating the upper portions' of thefcharge. l l

A present preferred embodiment of the invention with a modification is illustrated in the ac- 55 companying drawings, in which:

zones 24 and complete combustion zones 25 there- Figure 1 is a transverse sectional view through the furnace of my invention;

Figure 2 is a partial sectional View taken along the line II-II of Figure 1; the line I-I of Figure 2 indicates the plane on which the sectional 5 view of Figure 1 is taken; e

Figure 3 is a partial central longitudinal sectionalview taken along the line III-III of Figure l; and

Figure 4 is a view similar to Figure 3 showing a l0 modified form of the invention. n

Referring now in detail to the drawings, the furnace4 comprises a base or a hearth I Il and a bell or cover II. The base I0 includes arefractory floor I2 Abuilt up on a structural framework 15 I3, and a charge-supporting plate I4. The charge, in this instance,`a pile of sheets, is indi- Vcated at I5 and is enclosed within an inner cover I6 disposed thereover. `The lower edge of the cover I6 cooperates with a sand seal I'I on the base. The base has a sealing channel I8 adapted to cooperate with a sealing flange I9 depending from the cover IL". v

The cover II comprises a refractory-lined enclosure having an open bottom, side walls 20, end walls and a roof 2 I, assembled within a structural framework 22. In each end of each of the side Walls 20 and adjacent the lower edge thereof, a combustion chamber 23 is disposed. The combustion chambers 23 include partialcombustion kSome of the ports 29 are provided with closures 30 operable by handles-3| extending through the side walls of the cover. The LVflow of gases through the ports 29, 'of course, may be controlled byoperating theI closures or valves 30. e y Inlet ports 32 permit gases to be drawn from the interior of the cover into the zone 25, for v mixture with the gases delivered thereto from` the zone 24. Inspirators 33 project through the v end walls of the cover intothe complete combustion zones and are connected to any convenient source of air under pressure, such as a blower. ,The air jets created by the inspirator 33 induce gases from the interior of the cover through the ports 32 into the zones l25, from whichthey are 55 again discharged into the space within the furnace. Exhaust ports 34 are disposed substantially centrally of the end walls 20' adjacent the lower edges thereof and communicate with stacks 35.

In order to prevent overheating of the upper portions of the charge as a result of the natural tendency of the hot combustion gases to rise to the top of the furnace cover, I provide dampers 36 hinged at 31 to the inner walls of the cover. Operating linkages 38 extend through the walls of the furnace whereby the dampers may be adjusted from the exterior thereof.

The furnace cover is also provided with braces 39 operable from the outside of the furnace by levers 4U and links 4I, into engagement with the in'ner cover for providing lateral'support therefor. The braces are more fully described and claimedin the copending application of Albert W. Herman, Serial No. 11,235, led March 15, 1935, for Method and apparatus for annealing; matured in Patent No. 2,058,450, dated Oct. 21, 1936.

While the operation of the invention will probably be apparent from the foregoing description, it will be briefly reviewed here. cover Il is first lifted and the charge l5 disposed on the plate I4. The inner cover I6 is then placed over the charge and the' cover il is lowered thereunto. The braces 39 are then advanced into engagement with the inner cover and the dampers 36 adjusted to the proper positions. The gas supply for the burners 26 is then turned on and the burners are lighted through openings 42. The supply of air for the burners 26 is regulated so that partial combustion only of the gas will take place in the zones 24. The air jets created by the inspirators 33 induce .the partially burned gases from the zones 24 into the zones 25, Where further combustion takes place `with the air supplied by the inspirators. After complete combustion, the gases are discharged through the ports 29 at rates depending on the adjustment of the valve closures 30. discharged through the ports 29 circulate upwardly to the extent permitted by the adjustment of the dampers 36 and around the ends of the inner cover I6. A portion of the gases is returned to the zones through the ports 32 because of the inducing effect of the inspirators 33. The other portion of the gases in the furnace chamber is nally discharged through the ports 34 and stacks v35. The charge l5 is rapidly brought up to annealing temperature by the heating action of the combustion gases playing over the surfaces of the cover I6. The effect of the gases induced through the ports 32 is to cool slightly the gases burning in the zones 25 so that the deteriorating effect of the latter upon the inner cover, when discharging through the ports 29, is not as great as it otherwise would be. Longer life for the inner covers is thus assured. without material impairment of the rate of heating or reduction of the nal temperature attained.

Figure 4 illustrates a slightly modified form of construction in which the partial combustion zones are omitted. The fuel gas, in this case, blast furnace gas or producer gas, issupplied to the complete combustion zones 25 from a supply pipe 43 through headers 44 and connections 45. The'` air inspirators 33 extend-throughf-the con.- nections 45 and the headers 44. The operation of The furnace The gases' this modification is very similar to that of the one already described. Blast furnace gas, because it has a lower thermal content than natural gas, can be safely delivered through the ports 29 immediately after the initial combustion. The air for combustion, of course, is supplied through the inspirators 33. Lighting openings 46 are disposed just in advance yof the inspirators 33. Recirculation of the'combustion gases from the furnace to the zone 25 is effected by the inspirators 33 of the modified form of the invention by the same manner as in the structure first described and, in substantially all other respects, the two types of furnace are similar. One further point of difference, however, is in the discharge port. these ports are shown at 41 and are in the base i0 adjacent the ends thereof. Refractory blocks 48 are provided for closing the ports 41 when desired but, in normal operation, of course, the ports 41 will be in communication with the space within the furnace. This feature of the invention is particularly useful in connection with the invention described and claimed in my eopending application Serial No. 23,251, for Method and apparatus for annealing, led May 24, 1935.

It will be apparent from the foregoing that the invention provides a novel and advantageous solution for the problem of heating bell type furnaces' directly by combustion gases discharged thereinto. By causing combustion of natural gas fuel to occur in spaced zones, and by recirculating gas from the interior of the furnace to the combustion zone discharging thereinto, I am able to avoid or greatly minimize the destructive action which the ordinary gas burner would have on the inner cover if disposed closely adjacent thereto, as it would necessarily have to be. The cost of the heat-exchange tubes heretofore employed is avoided, and rapid and thorough heating insured by the direct contact of the hot gases with the inner cover enclosing the charge to be annealed. The dampers, of course, prevent overheating the top of the charge and may be so adjusted aste insure uniform temperature conditions throughout the latter at all times.

Numerous other changes in the construction illustrated and described herein, of course, may be made without departing from the spirit of the invention or the scope of the appended claims.

I claim:

1. In a furnace, a base or hearth, an openbottomed cover removably disposed thereon, a second cover disposed over the first-mentioned cover, a damper pivotally mounted on the inner :i

wallof the second cover and adapted at least partially to close the space between the covers. and means for operating the damper from the exterior of the second cover.

2. In a furnace, a base or hearth. an openbottomed cover removably disposed thereon, a second cover disposed over the first, means for supplying hot gases within the second cover at a point adjacent the base, a damper pivotally mounted on the wall of the second cover interiorly thereof, for controlling the upward ow of said gases, said damper being movable whereby at least partially to close the space between the covers, and means for operating the damper from outside the second cover. f

ALEE WILSON.

In the modification of Figure 4,

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