US3209808A - Soaking pit burner or the like - Google Patents

Description

Oct. 5, 1965 L. F. CONWAY ETAL 3, 8

SQAKING PIT BURNER OR THE LIKE IN VEN TORS AEO/V t CONWAY 4? BY WALTER Rum/y 3 Sheets-Sheet 2 bN Q x m. w x R 1 a. 6 AHH 1 u f n R T m. OM. d e l 1 F Oct. 5, 1965 L. F. CONWAY E TAL SOAKING PIT BURNER OR THE LIKE 3 Sheets-Sheet 3 Filed April 16, 1962 INVENTORS LEO/V F. CONWAY 9 BY WALTER KUD/N United States Patent 3,20?,808 SOAKING PIT BURNER OR THE LIKE Leon F. Conway, Whitehall Borough, and Walter Rodin,

Baldwin Borough, Pin, assignors to Bloom Engineering Company, line, Pittsburgh, Pa., a corporation of Pennsylvania Filed Apr. 16, 1962, Ser. No. 187,748 3 Claims. (Cl. 158-7) This invention relates to a burner capable of bettering performance in a soaking pit or other furnace, using combustion air, preferably preheated, and gaseous fuel in the form of fuel gas or atomized fuel oil, for combustion; energy of the combustion air being employed for relatively rapid mixing and for widespread dispersion of hot gases to obtain relatively rapid and uniform heating in all parts of the soaking pit or other furnace. More particularly, this invention pertains to such a burner for top-fired rectangular soaking pits or the like, usually with one-way firing using one or two relatively large burners.

A one-way top fired soaking pit, for example, is relatively economical of plant area particularly when utilizing a recuperator for the preheating of combustion air. A practice of this invention in such a soaking pit indicates that ingots can be heated to finish temperature and soaked uniformly much faster than heretofore has been thought possible, by use of a burner device disclosed herein. Thereby, there is a greatly increased tonnage per turn of uniformly hot, soaked ingots without an increase in the speed of gas circulation in the furnace. The soaking time from the moment that the steel control temperature is reached in the soaking pit is exceptionally short and there is uniformity of temperature from top to bottom of a respective ingot and among ingots in a particular pit. Heretofore, it was routine experience in such soaking pits using prior burners, to have ingot tops reach the desired steel temperature first and then have to increase soaking time while cutting back on fuel input until the lower portions of the ingots reached temperature and soaked, necessitating an ingot schedule in some cases even for a particular pit because of non-uniformity of temperature among ingots in that pit.

It appears, without this invention being limited thereto, that flame and hot gases from a burner of this invention are thrown around and widely dispersed promptly with portions of the heated gases going down and around at relatively steep angles with resultant acceleration in heating and soaking, decreased importance of selection of a temperature control location in the furnace, inhibition of risk of ingot washing or hot spots, and, markedly shortened heating and soaking time required for a given charge before the steel is ready to be taken out, or to be held at finish temperature with reduced fuel input to the burner. Therefore, pit efiiciency and production of ingots at finish temperature ready for rolling or other treatment in the steel plant, are greatly promoted. Burners disclosed herein are an improvement upon the invention disclosed in copending application for US. Letters Patent Serial No. 504,014 filed April 26, 1955 and assigned to the assignee hereof.

Other objects, features and advantages of this invention will be apparent from the following description and the accompanying drawings, which are illustrative only, in which FIGURE 1 is a sectional view in elevation of a rectangular one-way top-fired soaking pit taken along line line 1-1 of FIGURE 2, utilizing a single burner embodiment of this invention;

FIGURE 2 is a sectional view in elevation taken along line IIII of FIGURE 1;

FIGURE 3 is a sectional view in elevation of the burner 3,2695% Patented Get. 5, 1965 used in the soaking pit of FIGURES 1 and 2 taken through the axis thereof on line IlIlII of FIGURE 2;

FIGURE 4 is a partial view in elevation looking at the inner end of the burner shown in FIGURE 3 generally along line IV-IV of FIGURE 3;

FIGURE 5 is a sectional view of the refractory bafile of the burner shown in the preceding figures taken along line VV of FIGURE 4;

FIGURE 6 is a sectional view, similar to that shown in FIGURE 3, of a further burner embodiment of this invention; and

FIGURE 7 is a view in elevation looking at the inner end of the burner shown in FIGURE 6 generally along line VIIVII of FIGURE 6.

Referring to FIGURES 1 to 5, inclusive, of the drawings there is shown therein a rectangular one-way topfired soaking pit 10 having a single burner 11 of this invention mounted in the upper part of the firing end of furnace 10. Furnace 10 comprises front and back refractory lined walls 12 and 13, respectively, refractory lined side walls 14, a refractory hearth 15 adapted to receive a plurality of ingots 16 to be heated and soaked, and a removable refractory lined cover 17 which is opened at least whenever ingots are to be charged into the furnace, or discharged therefrom. The lower part of the front firing wall 12 is provided with a flue opening 18 leading to a flue 19 through which effluent gases from the interior of the soaking pit 11 are exhausted. Structural steel framing 24 is used to bind the furnace structure in the usual way.

Front wall 12 may be provided with a pair of thermocouple well positions 20 for thermocouples 21 to indicate the temperature of steel at that end of the pit. Additionally, thermocouple positions 22 may be provided in suitable refractory wells at the opposite end of the pit for thermocouples 23 to indicate steel temperature in that general location. It is common to provide such thermocouple control positions 20 and 22 adjacent the level of ingot tops in such a soaking pit and to intercom nect the thermocouples by a selector switch so that a temperature indication from any one, or from more than one, may be obtained in conventional furnaces to locate the hottest thermocouple location which then can be used as the control station to prevent overheating of the furnace and the work therein in the form of ingots, or other shapes. Although the description herein relates to the practice in connection with the heating and soaking of steel ingots 16, it will be recognized that burner devices of this invention may be used with other types of soaking pits and with other types of furnaces and, further, that other kinds of metal, or even non-metallic materials, may be heated by such burner devices. And, other thermocouple locations may often be found in such pits. However, heating is so relatively uniform and rapid that need for several thermocouple positions is avoided and location of a thermocouple used for control may be almost anywhere in the pit up to the ingot top level.

Burner 11 comprises, in the illustrated embodiment being described, a burner body having a metal shell 25 and a refractory lining 26. The burner is adapted to be fastened by a perimetral flange 27 to the metal shell of furnace 1i Burner 11 has an air body portion 28 and a combustion air inlet 29 at right angles thereto for connection to a combustion air conduit 31 by means of the respective flanges 31, such combustion air being the bulk combustion air at the desired air fuel ratio for the operation of burner 11 and any furnace, such as soaking pit 10, to which the burner is attached. The axis 32 of air body portion 28, which is cylindrical in cross section, is in axial registry with a port 33 in a conventional forward-firing refractory port block 34 set in the firing wall12 of pit 1 13.

The back end of burner 11 is provided with an axial opening 35 removably closed by a mounting plate 36 lined with refractory 37 and having a smaller axial opening 38 for a fuel tube 39 coaxial with axis 32. Fuel tube 39 as shown is adapted to supply a fuel ga including, without limitation, natural gas, coke oven gas, hydrocarbon gas and low calorie gas at suitable, including relatively low, velocity and pressure. The outer end of fuel tube 3? is fixed as by welding in an annular mounting plate 49 held in registry with an inlet fitting 41 to which fuel gas is supplied through a conduit 42, the outer end of fitting 41 being blanked off by a plate 43. Thus, upon admission of fuel gas through conduit 42 when the requisite valve or valves are open to the desired extent, such fuel gas will pass through the interior of fuel tube 39, which acts as a nozzle, and is radially spaced from the inside of air body portion 28. As shown, fuel gas is admitted squarely into fitting 41 at right angles thereto; however, the fuel gas may be whirled in fitting ill and tube 39, preferably in the same direction the combustion air is whirled when discharged, by offsetting conduit 42 to introduce the fuel gas tangentially into fitting 41 to one side of axis 32. The combustion air enters inlet 29 and passes axially along the outside of fuel tube 39 generally in the direction of arrows 44- through the annular passageway inside air body portion 28 and around tube 39 to ward a refractory baffle 45.

Refractory baffle 4-5 is an axially thick preferably circular disc extending across the front or inner end of burner 11 and sealed in place by an annular layer of refractory cement 46. Baflie 45 has a planar back face 47 normal to axis 32 and an axially straight central opening 48 extending therethrough for fluid fuel discharged by fuel tube 39, the inner end of which, if desired, may rest in the outer end of cylindrical opening 48 or extend to a position adjacent the front face of baffle 45. Preferably, such front face of baflie 45 comprises a planar rim portion 49 having flat surface and a central portion 50 having a frusto-conical surface relatively widely flaring in the direction of port 33, opening 48 intersecting and defining the smaller rear edge of surface 59.

The bulk combustion air, comprising all of the combustion air in the case of the use of fuel gas as fuel, passes through. the annular passage in air body portion 23 and through tangential combustion air jetting openings 51 extending through baffle 45 between the front and back faces thereof in circumferentially spaced relation to axis 32 and opening 48 and spaced transversely outwardly from said opening 48. As shown more fully in FIG- URE 5, each such combustion air opening 51 preferably has a straight axis 52 and a rounded entry edge 53 to minimize turbulence. The length of each opening 51 relative to its cross sectional area and the quantity of air passing therethrough is sumcient to jet combustion air passing through each such opening 51 in the direction of its respective axis 52 upon leaving exit edge 54. Thereby, the jetted combustion air is whirled, in a counterclockwise direction in the embodiment shown in FIGURE 4 indicated by arrows 55, because such straight axes 52 are generally tangentially positioned relative to an imaginary generally cylindrical shape coaxial with and surrounding opening 43 and fuel tube 39. In the illustrated embodiment, the inner ends of axes 52 intersect an imaginary circle comprising the edge between portions 49 and 50 of the front face of baffle 45, and the rear ends of axes 52 intersect at slightly smaller imaginary coaxial back circle on the back face of baffie 45. Thus, openings 51 not only produce a combined whirl of directed jets in the same direction of rotation which also has some flaring tendency as the jetted air leaves the exits 54. The intersection of a portion of openings 51 with dished surface 3 of the front face of baffle 45 in the illustrated embodiment produces scalloped rearwardly extending portions 540 of the exit edges of those openings 51 and appears to act to shorten the path and time of admixing fuel from opening 48 and air leaving the exits 5 so that flame hugs the front face of baflie at all rates of fuel feed to burner if and projects into soaking pit to. It will be apparent that the axes 52 may be bent instead of straight and also that adjoining combustion air openings may have different relative inclinations and/ or that there may be more than one ring of combustion air openings around the fuel discharge opening 4-8. If desired, burner 11 may be provided with a pilot light opening 56 extending through the burner wall and baffle for a pilot lighter 57.

In operation, a conventional air gas ratio controller is usually employed with conventional instrumentation one or more including temperature sensing indicators, such as thermocouples 21 and 23, to show when steel ingots in pit it have reached finish temperature above which the steel would tend to become overheated and possibly damaged. Ingots charged to soaking pit 10 may be at any level of temperature depending upon the length of elapsed track time between casting of the ingots and charging them into the pit. With a fresh charge in the pit, the burner 11 would be turned up, in a normal operation, to maximum fuel firing rate to heat the freshly charged ingots to finish temperature as rapidly as possible and then turn down the burner during soaking to minimum fuel rate (minimum fire) as rapidly as possible, provided, that the finish temperature at the end of the soaking turndown period in each ingot is relatively uniform from the outside to the inside thereof, from the top to bottom thereof, and, from ingot to ingot in the same soaking pit. With the embodiment of FIGURES 1 to 5, any of the thermocouples shown may be selected for control because, without intending to be limited to such explanation, it appears that flame and combustion gases from burner 11 are thrown in all directions and penetrate into all corners. Further, the axial furnace temperature gradient from one end of furnace it) to the other appears to reach a maximum mid-way between those ends and when the selected heating control temperature is reached and fuel and combustion air are turned down, a much greater turndown rate may be used and still achieve finish temperature throughout uniformly soaked steel ingots in the pit 10. That faster cutback during the soaking period will take place hereunder in lesser time apparently because during the heating stage of the furnace operation, the uniformity of heating produces concurrency and uniformity of soaking, in respect of each ingot and in respect of respective ingots in soaking pit 10 in a particular charge, to greatly foreshorten (halving it in some cases) what heretofore had been acknowledged to be a representative length of soaking time required between the time when the fuel began to be cut back and the achievement of the minimum fuel rate used to indicate the ingots were ready for removal from the pit. In other words, it appears that a burner device of the instant invention enables each ingot and the collective ingots to be heated so uniformly that there no longer is a fully or dangerously hot ingot part or ingot relative to other parts or ingots in the soaking pit to require further heating time for such other parts or ingots to take place during soaking of the first-mentioned ingot part or ingot. Such irregularity was so common in prior practices that regular schedules for the introduction and removal of ingots in a pit charge were arranged. Indeed, when the temperature control responds in a practice of the instant invention, indicating selected furnace temperature has been reached due to a drop off in the absorption rate of thermal units by the steel, the zone in pit It) adjacent flue opening 18 and near the bottom of the ingots nearest that flue opening, appears to be just about as hot as any other and about the same as the temperature of the zone near the hearth :at the far end of the furnace adjacent to end wall 13.

The burner embodiment in FIGURES 6 and 7 illustrates a combination fuel burner of this invention utilizing atomized fuel oil, or fuel gas, or both, as the relatively gaseous fuel and, if selected, a modified form of refractory baffle, parts in the embodiment of FIGURES 6 and 7 corresponding in construction and function to parts in the earlier described embodiment being provided With the same reference numerals with the addition of a prime accent thereto, respectively. Thus, burner 11', as shown, is provided with an annular back plate 43 which has a central opening drilled therein and tapped for a conventional emulsion type mixing and atomizing nozzle 60 which receives fuel oil through a pipe 61 and an atomizing fuel such as steam or compressed air through a pipe 62, the emulsion type mixture passing through an emulsion tube 63 and heat-resistant tip 64 for atomized discharge through a central axial orifice 64a in its inner end. Such atomized fuel is discharged uniformly around the axis of the burner and is drawn laterally across front face portion 50 of refractory baffle 45' by the force of the jetting air streams issuing from the tangential combustion air openings 51'. As shown, more of the whole front face of baffle 45' is dished with a somewhat planar ri-m portion 49' at right angles to axis 32'. Emulsion tube 63 and tip 64 may be mounted in cantilever position by virtue of the rigid mounting of the rear end of tube 63 in member 60. Burner 11' is also provided with a fuel gas connection comprising conduit 42' and fitting 41' and surrounding emulsion tube 63 within fitting 41' and fuel tube 39', for use when fuel oil may not be available as a matter of economics or supply; or, fuel gas may be burned along with atomized fuel oil in an operation of burner 11'. Generally, if burner 11' is operated on fuel gas alone as the fuel, the emulsion tube 63 and tip 64 would be withdrawn by disconnection of atomizer 60 from plate 43 and a pipe plug inserted in the drilled and tapped opening in plate 43' to close that opening. The action of burner 11' is virtually the same whether firing on fuel gas cycle, or fuel oil cycle, or a combined gas-andoil cycle, the dished surface portion 50 tending to even out differences between the respective fuels used and obtain the immediate precipitation of flame and combustion gases into the whole of the soaking pit including the bottom portion of the furnace. Burner 11 may also be fitted up as and operated as such a combination oil-and-gas burner. Burner 11 and burner 11 are primarily designed to use a relatively high calorie gas when operating on fuel gas such, for example, at natural gas, or coke oven gas, at relatively low pressure and velocity; the combustion air, on the other hand, being jetted through the combustion air openings in the baffle for discharge in a tangential and directional manner at relatively high velocity. Such combustion air for such a relatively high B.t.u. value gas may be hot or cold combustion air, that is, it may or may not be preheated before it is supplied to the interior of the burner around the fuel tube.

Various changes may be made in details of the illustrated embodiments and still other embodiments provided without departing from the spirit of this invention, or the scope of the appended claims.

We claim:

1. A burner mechanism for a soaking pit furnace or the like, comprising, in combination, a forward-firing port block having a port extending into said furnace, a burner having a body having a horizontal cylindrical air body portion, a thick circular refractory bafile to fit within and extend across the inner end of said air body portion at right angles and in sealed relation thereto, said baffle having a planar back face and a front face comprising an inwardly widely flaring surface central portion and an annular planar surface rim portion, a central fuel tube extending along the axis of said air body portion to said baffle and radially spaced from the inside of said air body portion, said baffle having a central axial fuel opening therethrough in registry with said fuel tube leading to the center of said central portion and a plurality of tangential combustion air openings having straight axes the inner ends of which substantially intersect an imaginary circle at the junction of said central and rim portions and the surface of said port and the outer ends of which substantially intersect a slightly smaller coaxial imaginary circle on said back face, the length to diameter ratio of said combustion air openings being sufficient to form axially directed jets of combustion air therethrough, said combustion air openings extending in the same direction of rotation, said combustion air openings having a rearwardly scalloped edge portion coincident with said flaring surface.

2. A burner mechanism for a soaking pit furnace or the like, comprising, in combination, a forward-firing port block having a port extending into said furnace, a burner having a body with a cylindrical air body portion, a thick refractory baffle to fit transversely within and extend across the inner end of said air body portion at right angles and in sealed relation thereto, said. baffle having a planar back face and a front face having at least a planar portion, a central fuel tube for fluid fuel extending along the axis of said air body portion to said baffle and radially spaced from the inside of said air body portion, said baffle having a central axial fuel opening therethrough coincident with said fuel tube which extends at least up to said central axial fuel opening, said baffle further having a plurality of tangential combustion air openings having straight axes the inner ends of which substantially intersect the surface of said port in an imaginary circle positioned concentrically around and radially spaced from said central axial fuel opening, said combustion air openings having their outer ends substantially intersecting an imaginary circle on said back face concentrically around and radially spaced from said fuel tube, the length to diameter ratio of said combustion air openings being sufiicient to form jets of combustion air issuing from the inner ends of said combustion air openings in the direction of the respective axes thereof, said combustion air openings extending in the same direction of rotation.

3. A burner for a soaking pit furnace or the like as set forth in claim 2, in which the exit ends of said combustion air openings are circumferentially spaced from one another and radially spaced from both said central axial fuel opening and the periphery of said baffle, and, in which each of the said straight axes of said combustion air openings makes an angle of about 25 with a generally axially extending intersecting line, respectively.

References Cited by the Examiner UNITED STATES PATENTS 820,235 5/06 Moore 1581.5 X 1,086,715 2/14 Irish 1581.5 1,789,772 1/31 Phelan 1581.5 1,841,023 1/32 Finke 158---1.5 X 1,910,735 5/33 Zikesch 28 2,333,531 11/43 Ferguson 15811 2,375,625 5/45 Conway 158-7 2,518,800 8/50 Lester 11028 2,781,756 2/57 Kobe 158-1.5 X

FOREIGN PATENTS 918,699 10/54 Germany.

310,899 4/29 Great Britain.

752,333 7/56 Great Britain.

819,977 9/59 Great Britain.

77,284 5/33 Sweden.

FREDERICK L. MATTESON, JR., Primary Examiner.

JAMES W. WESTHAVER, Examiner.

UNITED STATES PATENT OFFICE 57 CERTIFICATE OF CORRECTION Patent No. 3,209,808 October 5, 1965 Leon F. Conway et a1.

appears in the above numbered pat- It is hereby certified that error said Letters Patent should read as ent requiring correction and that the corrected below.

Column 5, line 11, for "fuel" read fluid Signed and sealed this 27th day of September 1966.

(SEAL) Attest:

ERNEST W. SWlDER Attesting Officer EDWARD J. BRENNER Commissioner of Patents

Claims (1)

1. A BURNER MECHANISM FOR A SOAKING PIT FURNACE OR THE LIKE, COMPRISING, IN COMBINATION, A FORWARD-FIRING PORT BLOCK HAVING A PORT EXTENDING INTO SAID FURNACE, A BURNER HAVING A BODY HAVING A HORIZONTAL CYLINDRICAL AIR BODY PORTION, A THICK CIRCULAR REFRACTORY BAFFLE TO FIT WITHIN AND EXTEND ACROSS THE INNER END OF SAID AIR BODY PORTION AT RIGHT ANGLES AND IN SEALED RELATION THERETO, SAID BAFFLE HAVING A PLANAR BACK FACE AND A FRONT FACE COMPRISING AN INWARDLY WIDELY FLARING SURFACE CENTRAL PORTION AND AN ANNULAR PLANAR SURFACE RIM PORTION, A CENTRAL FUEL TUBE EXTENDING ALONG THE AXIS OF SAID AIR BODY PORTION TO SAID BAFFLE AND RADIALLY SPACED FROM THE TINSID OF SAID AIR BODY PORTION, SAID BAFFLE HAVING A CENTRAL AXIAL FUEL OPENING THERETHROUGH IN REGISTRY WITH SAID FUEL TUBE LEADING TO THE CENTER OF SAID CENTRAL PORTION AND A PLURALITY OF TANGENTIAL COMBUSTION AIR OPENINGS HAVING STRAIGHT AXES THE INNER ENDS OF WHICH SUBSTANTIALLY INTERSECT AN IMAGINARY CIRCLE AT THE JUNCTION OF SAID CENTRAL AND RIM PORTIONS AND THE SURFACE OF SAID PORT AND THE OUTER ENDS OF WHICH SUBSANTIALLY INTERSECT A SLIGHTLY SMALLR COAXIAL IMAGINARY CIRCLE ON SAID BOACK FACE, THE LENGTH TO DIAMETER RATIO OF SAID COMBUSTION AIR OPENINGS BEING SUFFICIENT TO FORM AXIALLY DIRECTED JETS OF COMBUSTION AIR THERETHROUGH, SAID COMBUSTION AIR OPENIN GS EXTENDING IN THE SAME DIRECTION OF ROTATION, SAID COMBUSTION AIR OPENINGS HAVING A REARWARDLY SCALLOPED EDGE PORTION COINCIDENT WITH SAID FLARING SURFACE.

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