US3418062A - Burner structures - Google Patents

Description

Dec. 24, 1968 J. E. Hovls ETAI- BURNER STRUCTURES Filed Aug. 8, 1966 5 Sheets-Sheet l F igJ 44llt INVENTORS JAWS E. PKDVIS RQLAND L. PFFMAN their ATTQRNE YS De@ 24 1.958 J. E. Hovls ETAL BURNER STRUCTURES 3 Sheets-Sheet 5 Filed Aug. e. 196e INVENToRs JAMES E. Hows ROLLAND L. HOFFMAN BY L/ their ATTORNEY,`

United States Patent O 3,418,062 BURNER STRUCTURES James E. Hovis, Jefferson Township, Allegheny County, and Rolland L. Hoffman, Mount Lebanon Township, Allegheny County, Pa., assignors to Bloom Engineering Company, Inc., Pittsburgh, Pa., a corporation of Pennsylvania Filed Aug. 8, 1966, Ser. No. 571,085 14 Claims. (Cl. 431-350) ABSTRACT OF THE DISCLOSURE There are disclosed means and methods for operating a soaking pit, together with a burner structure for this purpose and for general utility. The burner structure comprises a body member, means mounted on said body member for defining a relatively larger outer ring port and a relatively smaller inner firing port disposed coaxially and inwardly of said outer firing port, first annular air passage means coupled to said outer firing port in bypassing relation to said inner firing port, fuel passage means coupled centrally to said inner firing port, second annular air passage means coupled to said inner firing port and surrounding said fuel passage means, and valve means coupled to each of said first and said second air supplying means, at least said second air passage means being so shaped that combustion air passing therethrough forms a confining envelope around fuel passage means in avoidance of the surfaces of said outer firing port.

The present invention relates to burner structures suitable for use in soaking pit furnaces or the like and to means for operating pit furnaces, more commonly known as soaking pits.

Pit-type furnaces or soaking pits are widely used throughout the steel industry for heating ingots of steel to rolling or forging temperatures. Although obviously not limited thereto, the apparatus and method of the invention will be exemplified in connection with firing and operating soaking pits for heating steel ingots or slabs to rolling temperatures.

In the conventional operation `of a soaking pit, the steel in gots to be heated for the aforementioned purpose usually are positioned in spaced relation in the soaking pit chamber, and the pit is provided with a removable top cover to permit the entry and removal of ingots by suitable ingot handling apparatus. When the soaking pit has been charged with ingots, the cover is positioned upon the coping or rails at the top of the soaking pit, and a combustion system is operated to deliver fluid fuel and combustion air into the soaking pit. In conventional practice, one or more burners are employed to introduce the fuel and combustion air at a relatively high velocity, which fills the soaking pit chamber with flames and hot products of combustion.

In most instances, the soaking pit is of elongated construction and the one or more burners are located on an end wall of the pit. Accordingly, it is important that the burners be capable, at all times and under all operating conditions of the soaking pit, of circulating completely and uniformly the hot combustion gases throughout the pit including the spaces between the ingots. A flue duct is coupled to the soaking pit and to a flue system that leads to a suitable exhaust stack. The flow of combustion products through the flue system usually is regulated by a damper or the like such that an over-pressure is maintained in the soaking pit as long as the cover is positioned thereon and while the ingots are being heated.

In the usual steel making operation, the ingots are delivered to the soaking pits at a temperature substantially below rolling temperature, where they are heated and then soaked at a specified rolling temperature, which may vary Patented Dec. 24, 1968 icc between 2000 F. and 2450" F. The ingots are heated to bring them up to this temperature and then thermally soaked for an additional period to ameliorate temperature differentials therein. A longer or shorter holding period may then follow dependent upon demand for heated ingots at the forge or rolling mill.

A problem then arises from the well-known fact that approximately 6-10 times as much fuel and air capacity is required during the heating period to elevate the ingot temperature from the charging temperature to the ingot rolling temperature than is required near the end of the soaking period to maintain the soaking pit and the ingots therein at the specified rolling temperature, after the ingots are brought to this temperature. In a specific example, the fuel demand can be gradually reduced to about l0-17% after the soaking pit attains the control temperature and the ingots reach the rolling temperature. The fuel demand will remain at about lO%-17% of maximum capacity during any subsequent holding period.

The maximum heating capacity of the soaking pit or furnace is thus established by the fuel requirements of the heating portion of the soaking pit operating cycle. Thus, during the soaking period, it becomes exceedingly diicult, if not impossible with conventional combustion system arrangements to maintain a proper circulation of combustion gases throughout the soaking pit when the fuel and high velocity combustion air are considerably reduced to the soaking or holding requirements.

In conventional combustion arrangements for soaking pits, as the fuel demand is reduced as set forth above, the heating patterns within the soaking pit are distorted inasmuch as the combustion systems are primarily geared to the fuel demand and hot gas circulation requirements of the heating portion of the cycle. Accordingly, as the soaking portion of the soaking pit cycle is commenced, the necessary reduction in fuel demand foreshortens the hot gas circulation through the soaking pit such that the ingots nearer the burner or burners become overheated in order to maintain the required soaking temperature at the far end of the soaking pit, i.e., adjacent the end wall of the soaking pit which is opposite from the burner and flue wall. In some cases the top portions of the nearer ingots begin to melt. The problem becomes more aggravated when the soaking pit is overloaded or is loaded improperly, for example, as in the undesirable, herring-bone pattern.

In one conventional soaking pit heating arrangement a single large burner is utilized and is so constructed as to operate efficiently as a high-velocity burner during the heating portion of the cycle to provide a uniform heating and temperature distribution throughout the soaking pit furnace and the ingots therein. However, when the ingots reach their required working temperature, the single, large burner must be turned down so that it no longer can function as a high-velocity burner, and the hot combustion gases produced thereby begin to short circuit through a path in the nearer or burner end portion of the soaking pit. As a result, the nearer ingots become overheated in order to maintain the ingots adjacent the far end of the soaking pit at the proper working temperature. If the ingots are removed promptly from the soaking pit after a normal length of soaking under proper loading locations, such overheating does not cause any undue difficulties at the rolling mill or in the soaking pit from melting or excessive scaling. In practice, however, the ingots are frequently left for extended holding periods Within the soaking pits until the rolling mill or other working operations are made ready to receive them. Accordingly, the temperature at the burner end wall continues to rise, resulting in severe overheating of the nearer ingots, to the extent that the top portions thereof begin to melt. or if the control is adjacent the burner end, the far ingots will be too cold for proper working. In any event, severe and unnecessary losses occur either as a result of the excessive production of scale at the elevated and prolonged soaking temperatures or of the necessity for reheating cold ingots.

It has been proposed to operate the single, large burner at a greater than minimum fuel requirement for soaking purposes; however, this results merely in the extension of the overheated portion of the soaking pit and in increasing the probability of melting the tops of the nearer ingots. It has also been proposed to operate the burner when on its minimum heating cycle with a greater percentage of excess combustion air, usually up to 30% excess in contrast to the normal above stoichiometiic requirements. Although this method alleviates the problern to some extent, it still does not result in a uniform heating of the pit during the soaking and holding operations. A further disadvantage lies in the fact that fuel consumption is increased.

These difficulties of the prior art are overcome by the present invention, which discloses means of soaking pin operation and burner arrangements for use therein which involve operation at maximum soaking pit capacity during the heating period, but which involve eicient, high velocity operation in the neighborhood of 10-17% of maximum pit capacity during the soaking and holding periods. The heating burner portion of the burner arrangement is operated solely during the heating portion of the soaking pit cycle, while an associated smaller or auxiliary burner structure is operated only during the soaking and/ or hold portion of the soaking pit cycle.

The burner structures, moreover, are each constructed or arranged so that they can discharge hot gases at maximum velocity and heating eiciency along substantially the entire length of the soaking Ipit in order to provide a uniform circulation of hot combustion gases throughout the pit, during any portion of the soaking pit cycle and at the widely varying fuel requirements dictated thereby. The unusual result attained by the disclosed method and apparatus stems from the fact that uniform heating of the soaking pit is attained both during the heating and soaking portions of the operating cycle which has not heretofore been accomplished by known heating arrangements, as stated previously.

In one arrangement of the invention, a pair of relatively larger burners are mounted on the front end Wall of the soaking pit, with each burner having about 50% of rated pit fuel capacity. A soaking and/or hold burner of about 10-17% rated capacity is mounted between the heating burners for purposes of symmetry. In another arrangement of the invention, a single, large burner of maximum rated capacity is mounted on one end wall of the soaking pit and a soaking/hold burner similar to that mentioned in the first example is mounted on the other soaking pit end wall. In the latter example the heating and soaking burners are mounted co-axially or symmetrically in the upper portion of the associated soaking pit end Wall or walls so as to lie in the most advantageous position for uniform circulation of hot gases within the soaking pit. In either example, the soaking/holding burner is not operated simultaneously with the heating burner or burners.

In a further arrangement of the disclosed apparatus, the heating or maximum capacity burner is arranged in a novel fashion Ias an annular structure surrounding the soaking/hold burner structure, and the concentric burner structure is mounted on the front end wall of the soaking pit generally at the location of the single, large conventional burner mentioned above. Several modilications of the concentric burner structure are disclosed herein and are described hereinafter more particularly in the forthcoming detailed description of the invention. At this point, however, it should be noted that each section, i.e., the annular maximum capacity section or the inner soaking or hold section are each arranged for high-velocity operation at their respective fuel capacities. More specifically, means are associated with the inner or low-capacity burner structure for attaining the desired shape of the flame envelope notwithstanding the fact that the concentric burner structure is mounted for firing through a single large port in the soaking pit wall. The concentric burner arrangement is further provided with novel structure or structures for the inletting of Huid fuel and combustion air to the respective parts of the burner structure.

It is of interest at this point to compare the resulting gains in flame energies produced by the method of the invention thus described with severe reduction in flame energies which have hitherto been encountered in conventional soaking pit firing arrangements. As an illustration, the firing of a soaking pit with a single, large high-velocity burner will be discussed. For purposes of comparison, it will be assumed that the burners have a combustion air velocity of 300 per second. As the burner is turned down from its rated capacity in the heating portion to a fuel demand of 16-17% as determined by the heat required during the soaking portion of the cycle, the combustion air is similarly reduced from 300 per second to 50 per second. However, the kinetic energies of the respective flames produced at these operating levels by a single burner will vary as the square ofthe ame velocities. Accordingly, the ame kinetic energies of the burner at its required lower operating level during the soaking period will be only 1/36 that of its rated capacity operation. This tremendous loss of kinetic energy in the flame is obviously insuflicient to carry the hot burner gases to any great distance along the length of a soaking pit. In those soaking pit operations where the fuel demand during the soaking or holding period is even less, for example 10% as` is frequently the case, the flame energy of the single large conventional burner is further reduced to only 1/100 of full capacity operation of the burner.

During the foregoing discussion various objects, features and advantages of the invention have -been alluded to. These and other objects, features and advantages of the invention together with structural details thereof will be elaborated upon during the forthcoming description of certain presently preferred embodiments of the invention and of certain presently preferred methods of practicing the same.

In the accompanying drawings, we have shown certain presently preferred embodiments of the invention together with preferred methods of practicing the same, wherein:

FIGURE 1 is a top plan View, with parts thereof in section, of a soaking pit and burner structure arranged in accordance with the invention and illustrating one method for operating the soaking pit;

FIGURE 2 is a top plan view, partially sectioned, of another soaking pit and burner arrangement of the invention illustrating another novel method of soaking pit operation;

FIGURE 3 is a longitudinally sectioned View of the apparatus as shown in FIGURE 2 and taken along reference line III-III thereof;

FIGURE 4 is a graphical representation of various conditions and problems associated with a typical conventional soaking pit operation;

FIGURE 5 is a longitudinally sectioned view of one form of burner structure arranged in accordance with the invention;

FIGURE 6 is a cross-sectional view of the burner apparatus as shown in FIGURE 5 and taken along reference line VI-VI thereof;

FIGURE 7 is a cross-sectional view of the burner apparatus as shown in FIGURE 5 and taken along reference line VII-VII thereof;

FIGURE 8 is a longitudinally sectioned View of another form of the burner structure of the invention;

FIGURE 9 is a cross-sectional view of the ybur-ner structure shown in lFIGURE 8 and taken along reference line IX-IX thereof; l ,y

FIGURE l0 is alongitudinally sectioned view of still another form of the burner structure of the invention; and

FIGURE ll is a cross-sectional view of the apparatus as shown in FIGURE and taken along reference line XI-XI thereof.

Referring now more particularly to FIGURE l of the drawings, a soaking pit 10 and burner arrangement 12 are illustrated therein in exemplication of one method of operating a soaking pit in accordance with the invention. Usually a battery of soaking pits, for example 10A and 10B, portions of which are shown in FIGURE 1, are operated together. A common gas or fuel header 14 is provided for a number of soaking pits while flue ducts 16 of a pair of soaking pits are coupled to a single exhaust stack (not shown). Usually a recuperator structure (not shown) is mounted in each exhaust duct for preheating the combustion air supplied to the recuperator from a suitable blower. The outlet of the recuperator is coupled to an associated air manifold 18 from which the aforementioned burner arrangement 12, in this example, is supplied by individual conduits 20. In this example, the burner arrangement 12 comprises three burners, 22, 24 and 26, to which fuel, gas or the like is supplied through a branched conduit system 28, the inlet of which is coupled through control valve 30 to the fuel header 14.

The soaking pit 10A or 10B in this example is of elongated generally rectangular construction in plan and t includes masonry side and end walls 32 and 34, respectively, which are backed up by steel plates and other reinforcing structures in the usual manner. The front or burner end wall 34a is provided in its lower portion with a flue port 36, as better shown in FIGURE 3, through which the soaking pit is coupled to its flue duct 16.

An intermediate burner 24 is positioned centrally in the upper portion of the front end wall 34, with side burners 22 and 26 being located closely adjacent thereto and on the same elevation in this example. The intermediate burner 24 is utilized in this example as the aforedescribed soak hold burner and is provided with about -40% of the rated capacity of one of the adjacent burners 22 and 26. The latter burners 22, 26 together constitute the heating burner arrangement of the soaking pit furnace and also together equal the rated heating capacity of the pit furnace. Desirably, the heating burners 22, 26 are of the same size and configuration, The heating burners 22, 26, are preferably utilized as part of this burner arrangement in order to provide overall llame symmetry in the soaking pit and uniform heating and circulation of the atmosphere thereof. The heating burners 22, 26 are therefore operated simultaneously but only during the heating portion of the soaking pit cycle. When the soaking pit has ybeen brought up to soaking or hold temperatures, the heating burners 22, 26 are shut off by means of gas valves 36 and suitable valves (not shown) in the air conduits 20. At this time, the central soak hold burner 24 is turned on to maintain the soaking pit and the ingots therein at the desired rolling or working temperature of the ingots.

Irrespective of their size, however, all of the burners 22-26 are of the high-velocity type and for example can have a combustion air velocity in the neighborhood of 300 per second. Accordingly, when the fuel demand of the soaking pit is reduced to 10-l7% of the maximum or rated fuel demand, which is dictated by the heating portion of the soaking pit cycle, the combustion air which is then introduced solely through the central or smaller burner 24, provides the flame with sufficient kinetic energy to carry the hot gases of the burner 24 substantially along the entire length of the soaking pit in order to ensure cornplete circulation of the hot combustion gases through the pit, as denoted by circulation arrows 38 of FIGURE 3.

The same air circulation pattern is thus attained by the smaller burner 24 as is engendered -by operation of the larger heating burners 22, 26 at their maximum or rated capacities. Referring again to FIGURE 3, when the soaking pit is thus operated in accordance with the invention, short circuiting of the hot gases, for example as denoted by flow arrows 40 or 42, is avoided. The foreshortened circulatory path 42 results in the operation of conventional soaking pits with a single large burner, while the intermediate and equally undesirable foreshortened path 40 represents previous attempts to solve this problem through the use of multiple burners of equal size.

Referring now to FIGURES 2 and 3 of the drawings, another method of soaking pit operation in accordance with the invention is illustrated. In this arrangement, a single large burner 44 of rated soaking pit capacity is mounted in one end -wall 34a, generally at the location occupied by the soaking/hold burner 24 of FIGURE 1. Directly opposite from the rated capacity burner 44 a substantially smaller soak/hold burner 24 is mounted. In this arrangement the large high-velocity burner 44 and the small high-velocity burner 24 can be mounted directly opposite from one another, and desirably are so mounted, on the same soaking pit axis as denoted by reference line III-III. The burners 44 and 24' `are supplied with suitable air and fuel conduits, as better shown in FIGURE 3 of the drawings and are generally similar to those described in FIGURE 1 with the exception that the air and fuel lines 46 and 48 respectively of the soak/hold burner 24 are passed beneath the oor structure 50 of the soaking pit.

As better shown in FIGURE 3, the operation of the larger high-velocity burner 44 during the heating operation includes a soaking pit atmosphere circulation as denoted by ow arrows 38 and is very similar to the pattern described previously and occurring during operation of the heating burners 22 and 26 of FIGURE 1. However, when the soak/ hold burner 24 is operated, after shutting olf the large burner 44, the furnace atmosphere is circulated more or less diametrically therethrough as denoted by ow arrows 52. However, the kinetic flame energy of the high-velocity soak/hold burner 24 is sufficient to substantially fill the soaking pit 10A with hot combustion gases and thereby to heat uniformly the ingots therein during the soaking or hold period.

Referring now to FIGURE 4 of the drawings, the advantageous results of the application of the methods disclosed herein in comparison to conventional or previously proposed methods of operation involving a single highvelocity burner or a number of correspondingly smaller such burners of equal sizes. In FIGURE 4, a number of curves are utilized to provide a comparison between fuel flow and various soaking pit and ingot temperatures. Although the illustrated curves have been somewhat idealized, e.g. to provide smoothness, etc., the curves represent a valid comparison of soaking pit conditions for both conventional and disclosed methods of operation, respectively. Curve 54 represents a comparison of fuel requirements during charge, heat, soak and hold periods of the soaking pit cycle. The vertical, dashed line 56 denotes the optimum time of lingot removal, whereat the ingots are uniformly heated to the ingot rolling temperature as denoted by curve 58. However, the ingots are frequently left in the soaking pit beyond the ideal soaking period, which is denoted in FIGURE 4, giving rise to a holding period denoted in the graph of FIGURE 4 to the right of the vertical line 56. Curve 60 denotes the control temperature of the soaking pit which is slightly higher than the desired rolling temperature.

The plateau 54a of fuel curve 54 denotes the maximum or rated fuel demand of the pit furnace as dictated by the fuel requirements of the heating period. When the pit temperature reaches the control temperature, as denoted by knee 60a of the curve 60, the fuel requirement can be then gradually reduced to about 10-17% of rated capacity as denoted -by the fuel curve portion 54b. After the ingots have reached uniform temperatures throughout, the fuel demand remains during the hold period at about l0l7% of rated capacity as denoted by fuel curve portion 54e.

In known methods of soaking pit operation wherein the hot soaking pit gases are short circuited either along the nearer circuit 42 or the intermediate circuit 40 (FIG- URE 3), the burner end wall temperature and the temperature of the nearer ingots continue to rise during the soaking period as denoted by curves 62 and 64, respectively, when the control sensor is at the far end wall. If the ingots are removed at the end of the soaking period it will be seen that in conventional methods that the temperature 'of the front or nearer ingots has not risen unduly as denoted -by the intersection of the curve 64 with the vertical line y56. In an ideal soaking pit operation, therefore, the use of conventional methods is not particularly disadvantageous.

As pointed out previously, however, the ingots frequently are left in the soaking pit beyond the ideal soaking period giving rise to the holding portion of the FIG- URE 4 graph. When using conventional methods of soaking pit operation, the temperature of the soaking pit burner wall and of the nearer ingots, or :of the intermediate ingots as the case may be, continues to rise as denoted lby curves 62 and 64 respectively. This rise in the holding period, which limit has not always been ob- ..served with the result that the tops of the nearer or intermediate ingots frequently have become melted or washed before the ingots are removed from the soaking pit to the rolling mill or the like. Further disadvantages stem 'from the fact that the ingots are no longer uniformly heated with reference to the entire charge which, of course, gives rise to well-known difficulties in operating the rolling mill or the like. Finally, excessive quantities of scale yare produced by the elevated temperatures of the conventional holding period, and the formation of such scale is still further accelerated in unsuccessful attempts to heat the soaking pit atmosphere more uniformly with conventionally available equipment.

With the operating apparatus of the invention, a uniformly heated atmosphere is attained within the soaking pit `both during the soaking and holding periods. Furthermore, the consumption of fuel is reduced during the holding period by eliminating the necessity of using additional excess combustion air. The soaking pit operational methods and the apparatus therefor are arranged such that the front and rear end wall temperatures can `be maintained essentially the same for an indefinite period of time as denoted by curve 60. It follows then that the ingot temperature likewise can be held uniformly for an indefinite period of time as denoted by curve 58.

Referring now to FIGURES -7 of the drawings7 another exemplary burner arrangement is shown therein which is suitable for use in the soaking pit operation of the invention, but which can be used in other applications requiring burner structures of differing rated capacities. In the present arrangement, the burner 66 includes a body structure 68 which is closed at the 4outlet or llame end by combustion air passage means such as a baille structure denoted generally by reference character 70 and fabricated from either refractory or water-cooled structures. The body 68 can 'be bolted or otherwise secured to a furnace wall 72 by means of its outlet flange 74. When thus secured, the outlet of the body structure is aligned with firing port 76 extending transversely through the furnace wall 72.

The baille structure 70 includes a first annular baille 78 provided with generally longitudinally extending air passages 80 which are, in this example, arranged in an equally spaced annular array around the baille 78. In this example, six such passages are utilized, although it will be obvious that la greater or lesser number can be employed. Positioned inwardly, and in this example axially, of the'annular baille 78 is. a generally tubular inner port block 82, the free inner surface 84 of which defines a second firing chamber or port. A second annular baille 86, which can be constructed Ias mentioned in oonnection with the baille 70, is mounted within the port block 82 adjacent the inner or front end thereof. The second baille 86 is thus likewise provided with an annular array of air passages 88, which in this example are equally spaced land eight in number, as better shown in FIG- URE 6 of the drawings. It will -be understood, of course, that here too a greater or lesser number of air passages 88 can be employed depending upon the application of the invention.

The second or inner annular baille 86, in addition, is provided with a central fuel port 90 into which a fuel conduit 92 opens. In this example, the fuel conduit 92 is mounted concentrically within a combustion air conduit 94 and both thus extend rearwardly through the end wall portion 96 of the body structure 68. The concentric conduits 92, 94 respectively terminate in supply fittings 98 and 100. The fuel supply fitting 100 and the fue] conduit 92 are capable of supplying suflicient fluid fuel as required either by the greater quantity of combustion air supplied through the outer air passages 82 or by the lesser supply through the inner air passages 88. The outer air passages are supplied by a separate air inlet 102 coupled to the 'body structure 68. The inner air passages 88 are supplied, in this example, through the air conduit 94 and the low flow air fitting 98.

In the operation of the yburner structure as illustrated in FIGURES 5-7 of the drawings, it is contemplated that the inner and outer burner sections thereof can 'be operated simultaneously or separately. In the simultaneous operation, combustion will occur b-oth at the inner firing port 84 and at the outer firing port 76 as the fuel respectively comes in contact with air supplied through the inner air passages 86 and the outer air passages 80. When the apparatus of FIGURES 5-7 is operated in accordance with the soaking pit operating method of the invention, for example, it is contemplated that during the heating or maximum fuel combustion portion of the soaking pit cycle, that high-velocity air will be emitted to the firing port 76 through the air passages 80 and that the low flow air to the inner air passages 88 will be shut .olf by closing valve 104. The greater quantity of fuel for this stage of the burner operation is supplied by adjusting throttling valve 106 in the fuel line 108.

In order to cause the fuel issuing from the central fuel opening of the inner bale 86 to substantially fill the outer firing port 76, means are mounted within the fuel conduit 92 for imparting a spin to the incoming fluid fuel. One arrangement for thus imparting the spin includes the use of one or more spiral vanes 110 mounted in the fuel conduit 92 adjacent its outlet end, as better shown in FIGURE 5 of the drawings. The spin thus imparted to the incoming fuel enables a llame front to be established extending across the entire width of the outer firing port 76 adjacent the outer air passages 80. In furtherance of this purpose the air passages 80 desirably are inclined outwardly as shown in the drawings to cause the air envelope and the expanding and non-burning fuel (when no air is issuing from the inner air passages 88) issuing from the inner firing burner 84 to hug the walls or surfaces of the outer firing port 76. On the other hand, the inner fuel passages 88 desirably are not inclined so that, when no air is issuing from the outer fuel passages 80, the inner passage air forms a smaller, constricting envelope about the fuel so that the burning fuel-air mixture issues from the inner firing port 84 in `avoidance of the walls of the outer port 76. At this time, the lower velocity of the fuel passing through conduit 92, in the arrangement of FIGURE 5, will not have sufficient spin imparted thereto by the vanes 110 to cause the fuel to disrupt the mu'ch higher velocity air envelope provided by the inner air passages 88.

When it is desired to operate only the inner burner structure, a suitable stop valve (not shown) is actuated to shut olf the air t0 the burner inlet 102 and the low flow air stop valve 104 is opened to supply air through the inner air passages 88. The smaller cross-sectional area of the air passages 88 introduces air at substantially the same high-velocity into the inner firing port 84, if

desired, 'although the capacity of the inner burner structure is substantially less than that of the outer burner structure. At the same time, the fuel throttling valve 106 is turned down to correspondingly reduce the ow of fuel into the inner firing port 84. As a result, combustion now takes place in the inner firing port 84 anda flame front is established thereacross adjacent the openings of the inner air passages 88 and substantially independently of the outer firing port 76. At the considerably reduced ow velocity of the incoming fuel through fuel conduit 92, the spin imparted by spiral vane or vanes 110 is likewise considerably reduced. Accordingly, the flame envelope does not swell to fill the outer firing port 76 but instead is directed into an elongated configuration by the high-velocity air passing through the inner air passages 88.l With this arrangement then, a high-energy flame can be produced by either of the outer or inner burner sections although the fuel consumptions differ considerably.

Referring now to FIGURES 8 and 9 of the drawings, a modified form of the burner arrangement of FIGURES -7 is illustrated wherein similar components are denoted by similar reference characters with primed accents. In the latter arrangement of the invention, outer and inner tiring ports 76 and 84 together with outer and inner air passages 80' and 88' are provided, and the air passages `are supplied with combustion air, as described above, with reference to FIGURES 5-7. In this arrangement, however, a relatively smaller central fuel conduit 92 is utilized solely for supplying fuel to the smaller or inner ring port 84'. Accordingly the spiral vanes or other spinning means of FIGURES 5-7 are omitted. The fuel for the outer burner section is supplied through a second, larger fuel inlet 112 extending through the body structure 68' and coupled in communication with an annular fuel conduit 114. The fuel conduit 114 for the outer burner section in turn surrounds the inner end portion of annular air conduit 94 for the inner burner section and thus communicates with a plurality of axially extending gas ow grooves 116 formed in the outer cylindrical periphery of the inner port block 82. In order to 'close the fuel grooves 116 where they are otherwise exposed on the inward protruding end of the inner port block 82' the annular fuel conduit 114 is extended thereover to a point where it engages the rear face of the outer baie 78.

In the operation of the burner apparatus as shown in FIGURES 8 and 9, a high-velocity flame can be produced in the outer tiring port 76 only by suitably manipulating fuel and air valves 120 and 122, respectively, which are shown schematically in FIGURE 8. In this arrangement of the invention, it is not necessary to spin the uid fuel when operating the outer burner section inasmuch as the fuel is introduced directly into the outer firing port 76 in bypassing relation to the inner firing port 84 through the fuel passages 116. Where desirable, however, spin can be imparted thereto by canting the fuel grooves 116.

When it is desired to operate the inner burner section only, the aforementioned valves 120 and 122 are shut off and air and fluid fuel are introduced into the inner firing port 84 by suitably manipulating valves 104 and 106', respectively. In the latter operation, a highenergy ame can be established in the inner tiring port 84' in the same manner as described above with reference to FIGURES 5-7.

" Referring now to FIGURES l0 and 1l of the drawings, still another modification of the `burner structure of the invention is illustrated wherein similar components of the preceding figures are identified by similar reference characters with primed accents. In burner structure 124, the baffle and tiring ports arrangement is substantially similar to that illustrated and described in connection with FIGURES 8 and 9 of the drawings. Similarly, the arrangement for supplying high-flow fuel and low-flow fuel,

respectively to the outer fuel openings 116' and to the inner fuel opening 90' are substantially as set forth previously. The burner structure 124 of FIGURES 10 and 1l differs from the burner structure 111 of FIGURES 8 and 9 primarily in the manner of supplying combustion air respectively to the outer air passages 80' and to the inner air passages 88. This arrangement of the invention is adapted particularly to supply such combustion air through a common throttling valve which can Ibe adjusted to supply such combustion air solely to the outer or to the inner air passages, or in varying amounts to both groups of passages when desired.

In this arrangement of the invention, an air conduit 126 extends from an opening 128 in a partition 130 extending transversely across the body structure 68 of the burner 124, as better shown in FIGURE ll. The other end of the air conduit 126 is extended through the annular fuel conduit 114', where it engages the inner face of the inner bafe 86' to communicate with the inner passages 88', as described above in connection with FIGURES 8 and 9.

The body partition 130, in this example, also divides the air inlet port 132 at the inlet end portion and extends to a Valve mechanism mounted on a shaft, one end of which protrudes through the Wall of the inlet 132 to which suitable valve operating means (not shown) are secured to manipulate the valve 134.

In the operation of the invention with the valve 134 disposed in the position evidenced by chain outline 134a,

combustion air is directed entirely into valve body chamber 138 and thence through conduit 126 to the inner air passages 88'. At the same time fuel valve 120 is closed and fuel valve 106 is opened to supply fuel only to the central fuel opening A flame front is thus established in the inner firing port 84 as described previously.

When operation only of the outer burner section is desired, the valve 134 is moved to its chain outline position 134b so that combustion air is introduced only to burner body chamber 140 from which it ows through the outer air passages 80 directly into the outer tiring port 76'. At this time, the fuel valve 106 is closed and the fuel valve is opened to supply fuel through inlet 112 and annular fuel conduit 114 to the annular array of fuel passages 116. In this case, a ame front is established in the outer tiring port 76 as noted previously.

Between the extreme positions 134a and 134b of the valve 134, the latter can be continuously adjusted for the simultaneous operation of both burner sections with the percentage of maximum or rated `burner capacity in one section being varied inversely with that of the other. rIhus, when the valve 134 is near its closed position 13411, i.e., in its solid outline position of FIGURE l0, the inner burner section is operated near its maximum capacity while the outer yburner section is operated near its minimum capacity. In this case, the fuel throttling valves 106 and 120' are accordingly adjusted to supply the appropriate and similar percentages of maximum fuel ow to the respective burner sections.

It will be understood, of course, that remote valve actuating vmeans can be coupled to the air valve 134 and to the fuel valves 106 and 120 to produce corresponding adjustments in the fuel valves 106 and 120', as the air valve 134 is moved between its extreme positions. It is contemplated further that similar valve actuating means can be coupled to air Valves 104 and 122' and to fuel valves 106 and 120 of FIGURE 8 or to the similar valves mentioned in connection with FIGURES 5-7, to provide for similar continuous variation and operation of the inner and outer burner sections of these modifications also.

In order to further exemplify the construction and arrangement of the outer and inner air passages 80 or 80 and 88 or 88 of the burners 66, 111 or 124, reference may be had to the air passages arranged as described and claimed in coassigned Patent No. 3,209,808 to Leon F.

1 1 Conway et al., entitled Soaking Pit Burner or the Like, or in co-assigned Patent No. 3,180,394 of Leon F. Conway, entitled Gas Burner. This and other descriptive matter herein, however, is presented solely for illustrating the invention and is not limitative thereof.

From the foregoing it wi'l be appreciated that novel apparatus for use in operating soaking pit furnaces and that novel and efficient burner constructions have been disclosed herein. It is to be understood, however, that the invention is not limited to the particular application illustrated but'that the method and apparatus can be extended to other applications involving other types of furnaces. Specifically, itis pointed out that the novel iburner structures of FIGURES 5-11 are lnot limited to soaking pit operations, `but instead can be constructed with differing relative fuel capacities of the individual burner sections as required for other applications. It will be understood also that the burner sections of each yburner structure can be operated alone or simultaneously as required and that either or both of the -burner sections of a given burner structure can be operated with higher or lower velocity combustion air than that noted herein depending on the application of the invention. Accordingly, while there have been shown and described certain present preferred embodiments of the invention together with present preferred methods of practicing the same, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

We claim:

1` A composite burner structure comprising a body member having a forward opening defining substantially an outer firing port, a port block mounted within said body member, said port block having an opening therein defining an inner firing port spaced inwardly of said outer firing port, first combustion air passage means extending through said port block and disposed laterally outwardly of said inner firing port, said lfirst air passage means communicating with said outer firing port in bypassing relation to said inner port, second combustion air passage means and fuel passage means coupled to said port block in communication with said inner firing port, and means for supplying fluid fuel to said fuel passage means and for supplying combustion air to said first and said second combustion air passage means, said second air passage means radially surrounding said fuel passage means and being shaped so that said second air passage means is capable of forming an air envelope surrounding said fuel to prevent said fuel when combusting within said inner firing port from filling said outer firing port.

2. The combination according to claim 1 wherein said supplying means include an air chamber defined by said body member and communicating with said first air passage means, and said second air passage means and said fuel passage means include an annular bafileinserted into the inward end portion of said inner firing port, said baflie having a central fuel passage and a plurality of air passages disposed radially outwardly of said fuel passage.

3. The combination according to claim 1 wherein said supplying means include a fuel conduit extending into said body member to the fuel passage means of said inner firing port, and spin means are mounted in said fuel conduit for imparting substantial spin to fuel flowing therethrough to said inner firing port upon the velocity of said fuel being that required to establish a ame front in said outer firing port.

4. The combination according to claim 1 wherein fuel conduit means are coupled respectively to said fuel passage means and to a plurality of generally longitudinally extending fuel channels in said port block, said fuel channels extending through said port block and opening into said outer firing port in by-passing relation to said inner firing port.

5. The combination according to claim 4 wherein said supplying means includes a plurality of coaxial conduits coupled respectively to said fuel channels, said first an'd said second air passage means, and 'said fuel passage means. l H

6. The combination according to claim 5` wherein said body member is divided -by partition means into a" pair of air chambers, one of said airv chambers being disposed for direct communication with one of said rst andrsaid' second air passage means, and the other of said air cham-V bers being coupled to that one of said combustion 'air conduits coupled to the other of said first and said sec'- ond air passage means. `r

7. The combination according to claim 1 vwherein'said port block is bipartite in construction and` includes an outer annular member having said first air passagev means therein and an inner tubular member closely fitted With-v in said annular member and extendingv rearwardly thereof for connection to said second air passage means and said fuel passage means.

8. The combination accolding to claim 7 wherein said port block is of bipartite construction including an annular member having said first air passage means therein and a generally tubular member fitted therein and extend# ng rearwardly of said annularv member for connection to said second air passage means and said fuel passage means, said fuel channels being formed Vat least`in part by a like number of grooves formed upon the outer surface of said tubular member and enclosed by engage?` ment with said annular member. v

9. The combination according to claim 8 wherein re-V mainders of said fuel passages are formed by said tubular member grooves and by the adjacent surface of a conduit forming part of said supplying means and into which the extending portion of said tubular member is closely fitted.

1G. The combination according to claim 1 wherein said port block is of tripartite construction and includes an outer annular member closely fitted withinsaid vbody member and having said first air passage means therein, a tubular member closely fitted within said oute'annular' member and extending rearwardly thereof, said' tubular member defining said inner firing port, and an inner annular member closely fitted within the extended portion of said tubular member, said second air passage means are extended through saidl inner annular member and positioned radially outwardly of its innery opening, and said fuel passage means include the central opening of said inner annular member.

11. The combination according to claim 10 whereina plurality of generally longitudinally extending fuel chanf nels are coupled to said supplying means and to said outer firing port in by-passing relation to said inner firing port, said fuel channels being formed at least partially by grooves formed on the outer surface of said tubular member and enclosed by the adjacent surfaces of said outer annularV member.

12. A- composite burner structure Vcomprising a body member, means mounted on' said body member forA defining a relatively larger outer firing port and a relatively smaller inner ring port disposed co-axially and inwardly of said outer firing port, first annular lair passage means coupled to said outer firing port in lbyypassing relation to said inner firing port, fuel passagemeansfcoupled generally centrally to said inner firing port, second annular air passage means coupled to said inner' lfiring portl and surrounding said fuel passage means, and valve means coupled to each of said first and said second airv supplying means, at least said second air passage means being so vshaped that combustion air when passing therethrough forms a confining envelope around vfuel issuing from said fuel passage means in avodanceof the surfacesgof said outer firing port.

13. The combination according to claim 12 wherein said first passage means include a plurality of air passages inclined radially outwardly of said burner lbody.

14. The combination according to claim 13 wherein said second air passage means include a plurality of elongated air passages disposed generally parallel to the axis of said inner ring port.

References Cited UNlTED STATES PATENTS 8/1916 Hunter 158-109 10/1942 Elder et al. 263-43 5 JOHN I. CAMBY, Primary Examiner.

U.S. Cl. X.R.

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