US2017480A - Metallurgical furnace - Google Patents

Description

Oct. 15, 1935. P. B. TONNAR 2,017,480

METALLURGICAL FUNACE Original Filed May 13, 1932 5 Sheets-Sheet 1 SIM Benton R4111 5 TON/VA 7? abtozmig 5 Oct. 15, 1935.

Original Filed May'lS, 1932 P. B. TONNAR METALLURGICAL FURNACE b Sheets-Sheet 2 illIaI LJL F140! ,5? TON/VAR WZM Oct. 15, 1935. P. B. TONNAR 2,017,430

METALLURGICAL FURNACE Original Filed May 15, 1952 s Sheets-Sheet 5 B1015 70mm? Oct. 15, 1935. P. B. TONNAR 2,017,480

METALLURGICAL FURNACE Original Filed May 15, 1932 5 Sheets-Sheet 4 fig-4 3m enfor PAl/Z B, TON/ A 7? (I ttorneg s Oct. 15, 1935. P. B. TONNAR 2,017,480

METALLURGICAL FURNACE Original Filed May 13, 1932 SSheets-Sheet 5 Patented Oct. 15, 1935 .'UNlTED STATES METALLURGICAL FURNACE Paul B. Tonnar, Cleveland, Ohio Continuation of application Serial No. 611,022, May 13, 1932. This application August 17, 1932,

Serial No. 629,249

7 Claims.

This invention relates to metallurgical furnaces and more particularly to improved open hearth furnace construction and to improved methods and apparatus for firing such furnaces.

Inthepresenttypes of open hearth furnaces the fuel, if of a nature not requiring preheating, and the air for its combustion, are introduced through suitable ports in one end of the furnace and the products of combustion are caused to pass out of the other end of the furnace through similar ports and then through suitable checkerwork in which a large part of their contained heat is stored.

At intervals of about fifteen minutes, this operation is reversed and the air is caused to pass first through the checker-chamber previously mentioned in which it is preheated and then through the ports where it joins with the fuel, then into the furnace and the products of combustion then pass out of the furnace through the ports by which the air entered during the previous cycle, and then through the checkerwork at that end of the furnace to heat it so that it may preheat the air when the furnace is again reversed.

In cases where the fuel used is producer gas or other low heat value gas, or under circumstances where it is desirable, the checker chambers are so divided that the fuelgaS may enter the furnace through one part and be preheated while the air for its combustion is passing through and being preheated by the other part of the checkers.

In these cases the outgoing hot gases pass, part through one section of the checkers and the balance through theothei' section, so that both sections shallbe'hot and prepared to preheat both the gas and air when the furnace is reversed.

In other cases, where heat value fuels are used, these fuels, whethef'solid, liquid or gaseous, are not preheated but are introduced into the current of preheated air as it enters the end of the furnace, in such a manner as to produce the most advantageous combustion possible under the circumstances.

From this description of the standard open hearth furnace of the present time, it will be readily understood that all definite control of the direction of the flame is impossible as the entering ports for the air and fuel are subjected to the intense heat of the outgoing gases when the furnace is reversed, and as all of the fuel must enter through one port, its intimate mixture with the air is impossible and the flame is accordingly long and often extends or persists to the further end of the furnace and even into the outgoing flues and checkers.

As a-modern open hearth furnace is usually more than sixty feet in length, and as the flame always passes in only one direction at a time, its 5 impingement on a solid charge to be melted is from one direction only.

In conventional practice, during the early stages of the heat, scrap or other solid components of the charge are piled high on the furnace 1o hearth. Duringthese early stages it is desirable to fire as hard as may be possible to more quickly reduce the solid materials to the molten state in order to minimize the loss of metal by oxidation.

A fuel such as oil, tar or coke oven gas entering 15 the furnace from a single port or burner, at considerable velocity, is deflectedfrom the surfaces of the solid materials toward the roof upon which it may impinge with very detrimental-effect. This action is due to the relatively short distance be- 20 tween the fuel port and the piled charge, to the large volume and high velocity of the flame of burning gases, and to the fact that mixing of the fuel with the air is relatively slow, so that combustion is still taking place when the flame im- 25 pinges on the roof with destructive effect.

Frequently the rate of firing may be severely limited by the ability of the roof to withstand the temperature and erosive effects of high rate firing without failure. v

The invention herein described contemplates an open hearth furnace wherein any combustible mixture which hereafter will be deemed as a suitable fuel in the presence of air adequate for substantially complete combustion, may be used. For example, oil, tar or coke oven gas is projected into the furnace through the medium of an adjustable firing port from a fuel tube disposed within the nose piece of the firing port, and is burned'with preheated air introduced with or about it. This mixture is delivered to the furnace chamber through a plurality of firing ports in a plurality of directions.

The firing ports are so designed that they may be easily swiveled, either horizontally or vertically, to the end that the flame from each may be accurately directed against that part of the charge where it will do its work most effectively and may be redirected from time to time toward other points so that during the entire period of making a heat the flame from each flring port may perform its function to the best advantage. 'When making up the bottom, between heats, the firing ports may also be so moved as to direct the flame from each against that part of the bottom requiring the most intense temperature.

During the melting of the charge, but more particularly after the stock is all melted, the several firing ports may all be directed so that the flame from each may be tangent to an imaginary circle more or less concentric with the furnace, ,or so as to produce a turbulent or cyclonic action of the combustible mixture and its products with a resultant rapid and complete combustion and a more intimate contact of the gases with the bath and a more complete absorption of the heat by the furnace charge. It is desirable to maintain a localized zone of combustion directly above the central part of the charge degree, and accordingly when using my invention the furnace may be fired to its maximum toward the surface of the solid materials with-.

out the liability of the combustible mixtures reaching the roof in an unburned state.

In open hearth furnace operation physical and chemical limitation of combustion are such that the differential of temperature between the flame and the bath is relatively small. Owing to the more intimate and rapid mixing and the consequent more rapid combustion, a greater heat release is accomplished in a given furnace volume. This obviously has the effect of increasing the temperature of the flame, thus increasing the differential of temperature above )mentioned, causing the operation of refining the steel to be accomplished in much less time and more efiiciently than is usual by the older methods.

This application constitutes a continuation of my application, Serial No. 611,022, filed May 13,

Other advantageous features will appear in the following detailed description which, considered in conjunction with the accompanying drawings, sets forth the preferred embodiment of my invention, wherein:

Figure 1 is a plan view partly in section of an open hearth furnace including the regenerator chambers therefor employing my invention;

Figure 2 is a front elevation partly in section taken along the line 22 of Figure 1;

Figure 3 is a side elevational sectional view taken along the line 33 of Figure 1;

Figure 4 is a top plan view partly in section illustrating a modified form of my invention wherein a suitable recuperator is provided to preheat air for continuous operation;

Figure 5 is a modified form of my invention wherein suitable regenerators are provided to preheat both air and gas;-

Figure 6 is a sectional "view taken on the line 6-15 of Figure 5;

Figure 7 is a sectional view taken on the line 'I'I of Figure 5;

Figure 8 is a sectional view illustrating a modifiedadjustable firing port adapted to be used with my modified furnace structure.

With reference to the accompamring drawi 8 and particularly Figures 1 to 3 inclusive, there is illustrated the preferred embodiment of my invention comprising an open hearth furnace designated in its entirety by the numeral I and including the regenerators 2 and 3. The open 5 hearth furnace I is of the usual construction and includes a front wall 4, back wall 5 and bulkheads 6 and 1, which define a refining chamber 8 having a hearth 9 disposed therein. The bulkheads 6 and I which are situated at opposing 1o ends of the refining chamber 8 are identical in construction and comprise a single downtake flue 10 having firing ports M with fuel tubes H associated therewith disposed on each side thereof. The term firing port hereinafter used is deemed to designate the entire adjustable umt through which the fuel and air are projected into the furnace chamber. The downtake flues ID are adapted to connect the chamber 8 with the slag 'pockets l2 and convey the products of combustion from the refining chamber to the regenerators 2 and 3.

The provision.of but a single flue in the bulkheads of the furnace through which the products of combustion are conveyed from the laboratory or chamber 8 permits the hearth to be built up at the ends. These built up ends will not allow the charge to boil over into the downtake flue and slag pockets. Furthermore, it is not material to the operation of this furnace whether or not the walls of this flue become eroded as the velocity, direction and control of the flame is not dependent on its size or construction as the firing ports through which the combustible mixtures are introduced into the chamber are entirely independent in their operation from the discharge ports. I

The bulkheads 6 and I are connected with the front and back walls of the chamber by suitable walls l3. Disposed adjacent the exterior of each of the walls I3 is a firing port I4, the nose of which projects therethrough and communicates with the interior of the furnace. Each of the firing ports l4 has associated therewith a fuel tube or burner II. The firing ports are adjustable and may be so directed and redirected as to cause a flame projected thereby to melt the stock to the best advantages at all times during the melting period of operation and may later be again redirected so as to produce a "tangential system of firingover the charged material. This system produces violent cyclonic action and turbulence of the combustible mixtures directly over a portion of the charged material and assures rapid and complete combustion thereof within the furnace chamber. Each firing port may be adjusted to project the combustible mixture independent of the other firing ports and co-operation between firing ports may be such as to divert the flames from their original pro- .jected direction.

The firing ports II are so adjustable that they may be disposed at any angle with relation the bottom of the furnace. On sintering the furnace bottom, it may onlybe necessary to usethe flames from one or two firing ports, and these can be made to sweep the entire surface of the hearth. The provision of firing ports as disclosed in my invention provides a continuous firing of the furnace at all times during its operation. Furthermore, the direction and intensity of the flame can be controlled at all times. A plurality of short flames disposed so as to create a turbulence or change in direction of the com- 76 bustible mixture is eifecti've in obtaining a more complete combustion.

Adjacent the end of each of the downtake flues ll) of the respective bulkheads 5 and 1 a slidable valve l5 and I5 respectively is disposed to preclude the flow of products of combustion from the chamber 8 during certain periods of the op eration of the furnace. The valves l5 and I5 are slidably mounted in water cooled guide members l1 and I8 respectively, secured in the walls of each of the flues ill.

The exhaust flues l terminate at their lower ends in slag pockets or pits |2. Each of the regenerator units 2 and 3 is identical in design, and is of the usual construction, the chamber of which is provided with checker brick which absorb a portion of the heat from the waste gases which pass alternately therethrough from the furnace, and give up heat to the cold air passing through the previously heated chamber to the firing ports l4, communicating with the interior of the open hearth chamber 8.

The waste gases are exhausted from the regenerator chamber through ports 23 and conveyed to either a waste heat boiler or stack (not shown) through flue 36 as desired. In conveying the air to the flring port and in turn directing the same into the furnace chamber the hereinabove procedure is reversed, the cool air is introduced into the regenerator chambers through either the valve 20 or 2| and in passing therethrough is heated. The heated air is conveyed from the uppermost part of the regenerator through flues 24, 25, 25, 21, 28, and 29 to the firing port M where the air and fuel mixture is ejected into the laboratory chamber 8 of the furnace in such volumes and at such velocities as are commensurate with the most efficient operation of the open hearth furnace. Y

Adjacent the end of each of the flues 25 is provided a water cooled slidable valve 30 or 3| respectively which valves are vertically actuated by any suitable means in guide members 32 disposed in the side walls of the flue.

The firing ports l4 and related structure as depicted in Figures 1 and 3 are disclosed in detail and claimed in my co-pending application, Serial No. 627,922 filed August 8, 1932.

These firing ports l4 are adjustably mounted exteriorly of the furnace walls, on pedestals 33 forming the upper ends of the vertical flues 29. The firing ports are preferably formed of sheet metal with refractory lining and adjustably carried in brackets 34 mounted on a turntable 35 suitably sealed against air leak.., the same projecting into or through the walls l3 of the furnace proper, suitably sealed clearance being provided in the walls about the ends of the nose portion of the firing ports to permit considerable amount of vertical and lateral adjustment, thus making it possible to direct the combustible mixture from the firing port as desired. The fuel tubes mounted in the adjustable firing ports l4 and movable therewith assure the ever present and close proximity of the air supply to the fuel emitting from the firing port, resulting in a more ready and perfect combustion thereof.

In the operation of the open hearth furnace herein disclosed which embodies my invention, the valve IS in the downtake flue ID of the bulkhead 6, valve 3| in the preheated air flue 25 and stack valve 38 are closed. Cold air is adapted to be introduced into the regeneratorunit 2 through valve 23 and ports 23 and in passing therethrough is heated. The heated air is conveyed from the regenerator 2 to the firing port l4 through flues 24, 25, 25, 21, and 28 and upwardly through the vertical flues 29. The preheated air along with. the fuel referred to as.

combustible mixture is directed into the furnace I through the four firing ports at an angle so that a vortex is formed directly above the charge by the burning gases producing violent cyclonic action and turbulence, or the firing ports may be directed to project the flame in any other direction which will effect the most economical operation of the furnace. Adjacent streams of combustible mixtures projected in the same general direction across the furnace may be converged, or streams of combustible mixtures from opposite direction may impinge upon each other whereby the streams of combustible mixtures are diverted from the original projected direction. The burned gases are conveyed from the furnace chamber through valve l6 and the downtake flue In of bulkheads 1, slag pocket l2, through the regenerator unit 3, and thence conducted through the ports 23, valve 39 and flue 31 to any suitable means of disposal, either to a stack or waste heat boiler (not shown) as the case may be. At such time as the checkerwork of the regenerator unit 2 has released the greater part of its absorbed heat, valves I8, 30, and 38 are closed and valves l5, 3|, and 39 are opened and cold air is admitted through valve 2| and inlet ports 23 to so the regenerator unit3 where it is heated and conveyed therefrom to the firing ports l4 through suitable conduits or flues as hereinabove referred to.

Referring now to Figure 4 there is illustrated a modified form of my invention comprising an open hearth furnace 39 including a chamber 40 having exhaust ports or downtakes 4| disposed at opposite ends of the chamber. Associated with the downtake flues are suitable slag pockets 40 42 and flues 43 which are adapted to convey the products of'combustion from the downtake to a suitable recuperator 44. The products of combustion pass from the recuperator through flue 45 to a stack or waste heat boiler (not 45 shown). Air is introduced into the recuperator by a blower 46 and in passing therethrough is heated. The heated air is then conveyed from the recuperator to the flring ports 41 through flues 48, 49, and 50, 50.

In the operation of the modified form of my invention wherein a recuperator is provided in the place of regenerator chambers, the products of combustion pass continuously from the chambers 40 through downtakes 4| disposed at each 5 end thereof, and heated air continuously passes from the recuperator 44 to the firing port 41.

With reference to Figures 5 to 8 inclusive there is illustrated an open hearth furnace organization which may be of the same construction as shown in Figure 1 except that it is adapted to operate with producer gas or the like which is preferably preheated before being introduced into the furnace and used as fuel. The regenerators 2 and 3 are'preferably formed with two longitudinal chambers 5|a and 52, the former to preheat the air and the latter to heat the gas. The gas to be preheated is introduced from gas supply duct 1| into a flue 53, which conveys the same to the regenerator chamber 52. The gas is heated while passing therethrough and is conveyed therefrom to the firing port l4 through flues 54, 55, 55, and 51 and the inner flue 55 of concentric vertically disposed flues. The air to be heated is introduced into a conduit 76 59 through a valve 60 and is conducted to the chamber 5| of the regenerator wherein it is heated and conveyed ;to the firing port l4 through fiues 6|, 62, 63, 64 and through vertical flue 85. Valves 66 are provided in the flue leading from the slag pockets i2 to the regenerators and are closed when gas and air are heated in the regenerators Sid and 52 and are opened when hot furnace gases are permitted to pass therethrough to heat the checkerwork disposed therein. Similarly the valves 61 and 68 are ,open or closed to direct the hot burned gases from the regenerators to the stack or waste heat boiler. Valves 69 and iii are disposed in the fiues 54 and BI respectively and are closed when the valves 66 are opened to direct the hot gases from the furnace chamber through the regenerator and prevent the escape thereof into the fiues leading to the firing ports.

It will be seen that I have provided a furnace wherein there is a continuous non-reversing firing during the heating and treating of a charge and wherein the numerous disadvantages of present open hearth practice as hereinabove set forth have been minimized and in many instances entirely eliminated.

.Althmigh theforegoing description is necessarily of a detailed character in order to completely set forth this invention, it is to be understood that the specific terminology is not intended to be restrictive or confining and it is further understood that various re-arrangements of parts and modifications of structural detail may be resorted to without departing from the scope or spirit of the invention as herein claimed.

I claim:

1. An open hearthfurnace having a refining chamber, outlet ports disposed at opposite ends of the furnace for continuously conveying waste gases from the chamber, inlet ports for discharging streams of air into the chamber disposed in pairs on opposite sides of each outlet port, means for projecting fuel into the chamber within each of said air streams and means; for adjustably the chamber through the outlet ports, and means 'for varying the angle of projection of the combustible mixtures into the furnace.

3. An open hearth furnace having a refining chamber of generally rectangular formation, downtake exhaust fiues located at opposite ends of the chamber and serving only as passages for continuously conveying waste gases from the chamber, and inlet ports for continuously discharging combustible mixtures into the chamber simultaneously with the escape of waste. gases 5 disposed on opposite sides of each exhaust flue and arranged to continuously discharge the said mixtures from opposite ends of the fin'nace at converging angles toward the central portion of 10 the chamber.

4. An open hearth furnace having a refining chamber of generally rectangular formation, downtake exhaust fiues located at opposite ends of the chamber and serving only as passages for 15 the escape of waste gases from the chamber, and movably mounted inlet ports for discharging combustible mixtures. into the chamber simultaneously with the escape of waste gases from the chamber, said inletports being dis- 20 posed on oposite sides of each exhaust flue.

5. An open hearth furnace having a refining chamber of generally rectangular formation, downtake exhaust fiues one at each end of the chamber and serving only as passages for the 25 escape of waste gases from the chamber, and firing ports located at opposite ends of the furnace on each side of the respective exhaust flues and having a nose portion projecting thru the wall of the furnace, said ports being adjustable 30 to vary the angle of projection of the nose portion.

6. An open hearth furnace having a refining chamber of generally rectangular formation, down-take exhaust fiues located at opposite ends 35 of the chamber and serving only as passages for continuously conveying gases from the chamber and firing ports for continuously introducing fuel into the chamber simultaneously with the escape of waste gases through said exhaust ports. 40 said firing ports being disposed on opposite sides 01' each exhaust fiue and adjustable to continuously introduce fuel from opposite ends of the furnace at converging angles towards the central portion of the chamber; 45

7. An open hearth furnace having a refining chamber of generally rectangular formation. down-take exhaust fiues located at opposite ends of the chamber and serving only as passages for continuously conveying gases from the chamber and adjustable means for continuously introducing fuel into the chamber simultaneously with the escape .of waste gases through said exhaust ports, said means being disposed on opposite sides of each exhaust fiue and arranged to continuously introduce fuel from opposite ends of the furnace at converging angles toward the central portion of the furnace.

PAUL B. TON'NAR.

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