US3387784A - Burner for fluid fuels - Google Patents

Description

B. G. WARD, JR

BURNER FOR FLUID FUELS Cri@ June 11, 1968 inal Filed NOV. 26, 1962 Inventor' gert GA/QrdJr Unit States Patent O 3,387,784 BURNER FOR FLUID FUELS Bert G. Ward, Jr., Niles, Ill., assigner to Chemetron Corporation, Chicago, Ill., a corporation of Delaware Continuation of appiication Ser. No. 240,695, Nov. 26, 1962. This application (1ct. 27, 1966, Ser. No. 590,096 7 Claims. (Cl. Z39-132.3)

This application is a continuation of application Ser. No. 240,095 tiled Nov. 26, 1962, now abandoned.

This invention relates in general to apparatus for burning fluid fuels in a confined area. More particularly, this invention relates apparatus for burning gases in large volumes and at high velocities for melting and refining scrap metals, while maintaining the noise level of combustion at a minimum.

The gas burner is in wide use in the metallurgical field for supplementing the source of heat in various types of furnaces such as the open hearth, the reverberatory type and the electric furnace. In such capacities it functions to: reduce total heat or melting time; increase furnace operation; reduce overall electric power consumption in the instance of an electric furnace and also reduce electrode consumption; and increase furnace availability. To make the gas burner an effective tool in such an operation it must be capable f developing flame temperatures in the range of 3,000-5,000 F. and for substantial periods of time. Large volumes of combustible gases, such as natural gas, are mixed with an oxidizing gas, such as oxygen, in order to effect the desired temperatures. The burner is, by necessity, operated inside the furnace. As a consequence of this type of combustion, a deafening noise is created which not only is detrimental to the auditory nerve, but in some instances has caused employees to refuse to work in those areas where the burners are operating.

This invention provides an apparatus whereby the desired temperatures and B.t.u.s of combustion can be obtained over requisite periods of time without the objectionable noise factor commonly associated with the operation of burners concerned with in this invention.

It is therefore an object of the present invention to provide apparatus for burning fluid fuels without creating excessive and detrimental noise.

It is still a further object to provide apparatus for burning iluid fuels at low noise levels which is simple, efficient and inexpensive.

It is still another object of the present invention to provide apparatus for burning gaseous fuels in a confined area and at high velocities and temperatures with a minimum amount of noise.

A still further object is to provide a versatile apparatus for combusting uid fuels at low noise levels which is adaptable to various kinds of fuels.

Other objects and advantages of this invention will become more apparent as the following description proceeds when taken in conjunction with the accompanying drawing in which:

FIGURE 1 is a top plan view of the novel burner of the present invention.

FIGURE 2 is a sectional view taken along line 2-2 of FIGURE l.

FIGURE 3 is an end view at the discharge end of the present burner.

Essentially, the method of the present invention for burning combustible fluid fuels with a minimum amount of noise is to direct a stream of fluid fuel in a substantially linear manner and to simultaneously direct a stream of oxidizing gas for the fuel coaxially with respect to the stream of combustible fuel. Portions of the normally interface region of the streams are circumferentially separated from one another as the streams are being directed 3,337,754 Patented l.Future 11, 1968 in a parallel manner. In addition to the directing of the two streams in the aforesaid manner, it has been found that best results are obtained when the oxidizing gas is directly centrally of the combustible fuel and at a velocity greater than that of the fuel. The faster velocity of the central stream tends to draw the huid fuel into the oxidizing stream and since the streams are being directed in a parallel manner, and adjacent portions of them are temporarily separated from one another, a gradual intermixing is effected over a considerable length of the ilame with a consequent, substantial reduction in noise.

Other features which have been found to influence the diminution of noise are the relative velocities of the two streams as Well as their cross sectional areas. For example, when the combustible gas is natural gas and the oxidizing gas is oxygen, the oxygen stream is directed centrally of the natural gas and at a velocity of about three and one half times that of the natural gas. At the same time the cross sectional area of the natural gas stream should be about twice that of the oxygen stream. These relative dimensions not only supplement the reduction of noise during combustion of natural gas but provide a 2:1 ratio by volume of oxygen to natural gas which is best suited for burning the gas.

By employing the novel apparatus of the present invention one can obtain the required temperatures of 3000-5000" F. as well as a capacity of 25 million B.t.u.s per hour. These temperatures and B.t.u. capacities of course require that large volumes of fuel be combusted and the following data is representative of the actual operating conditions of the present apparatus:

TABLE I Run Cu. Ft. of Natural Oxygen, Cu. Ft. Ratio of Oxygen Numbers Gas Per Hour Per Hour to Natural Gas l1, 625 17, 500 1.5 12,175 17, 500 1. 45 11, 750 18, 750 1. 65 13, 000 18, 750 1. 44 12, 500 16, 250 1. 37 13, G00 19, 500 1. 5 13, 000 20, 000 1. 57 13, 750 19, 250 1. 4 1a, ooo 19, 500 1. 5 13, 750 20, 000 1. 45

While the large volumes of gases listed in Table I were being burned, the noise level of the burner'was so low that it was not possible to detect by ear its operation over the usual sounds normally associated with steel mill operations. No complaints were registered by workmen in the mill where the burners were being operated and this is true even though several burners were being simultaneously operated, as is customary in this art.

It will be noted from Table I that the preferred coinbustible fluid fuel utilized in the present process is natural gas. However, other iiuid fuels Whether of the strictly gaseous, liquid or particulate type can also be employed in conjunction with an oxidizing gas. Representative of the gaseous class are hydrogen or propane; illustrations of the liquid fuels are fuel oil, pitch or tar; and representative of the solid particulate kind is pulverized coal. Mixtures of the foregoing can obviously be employed in the same manner as the fuels would be alone. While substantially pure oxygen is the preferred oxidizing gas for the combustion of the foregoing mentioned fluid fuels, and mixtures thereof, other gaseous oxidizing materials can also be employed such as air and fluorine and their mixtures.

In one embodiment of the present apparatus, the oxygen stream is centrally directed with respect to the fluid fuel. While this particular order has been found to offer the best results, especially when the oxygen stream has a faster velocity, the fluid fuel can be placed centrally and the oxygen directed therearound. Irrespective of the 3 order, for optimum results, one stream should have a faster velocity than the other.

The drawing illustrates the apparatus which has been found best to carry out the foregoing apparatus. Burner 1f) is formed of three concentrically positioned pipes 11, 12 and 13 composed of black iron. Outer pipe 13 has two rounded end portions 17 and 18 and is welded to pipe 12 at those points designated by the numeral 15. Central pipe 11 forms a chamber 20 supplying an oxidizing gas through burner and terminates a short distance inwardly from the jointure of pipe 12 and the rounded end portion 1S of pipe 13. The area along the inside of pipe 12 between the ends of pipes 11 and 12 forms the nozzle portion 21 of the present burner. Disposed between pipes 11 and 12 and extending a short distance into nozzle portion 21 are a plurality of copper tubes 23. All of these tubes have substantially the same inside and outside diameters and are aligned in a parallel manner with the longitudinal axis of the burner. This is best shown in FIGURE 3. Pipes 23 are abutted against each other around central chamber 26 and in chamber 25, formed between pipes 11 and 12, which supplies a combustible fluid fuel to the nozzle end. These pipes have their ends in transverse alignment and are suitably secured between pipes 11 and 12 in chamber 25, by brazing pipes 2-3 to the outer surface of pipe 11. Shirns can be employed in addition to brazing if desired to effect contact between pipes 23 and the surfaces of pipes 11 and 12. The abutment of pipes 23 around the outside surface of pipe 11 provides a multiplicity of small triangular passages 26 immediately adjacent pipe 11 and around the periphery thereof.

Nozzle portion 21 is cooled by means of concentric cooling chamber 3ft formed between concentric pipes 12 and 13. A laterally extending water inlet pipe 32 with elbow 33 communicates with chamber 30 at the nozzle portion and serves to convey cooling water to the nozzle. The heated water leaves the burner near the rear section by means of outlet pipe 31,. Elbow 33 as well as outlet pipe 31 are welded to pipe 13 as indicated by weld 34 surrounding pipe 31. The same manner of attachment is employed for securing gas inlet pipe 35 to pipe 12 and consequently' in communication with chamber 25 which attachment is made in the area of its exposure and outside pipe 13.

A fluid tight engagement between pipes 11 and 12 is provided by stufling box 37 and flanges 3S and 39 which also serve to concentrically align pipe 12 with pipe 11 at the rear of the burner. Stufiing box 37 includes a curved collar 4f) welded at 41 to ange 38 and having a threaded portion 42 for engaging a threaded skirt section 43 of screw cap 44 which slides over pipe 11. A resilient packing 45 including O-ring 45a is force fitted between collar 40, pipe 11 and cap 44. Flanges 38 and 39, the latter being welded to pipe 12 at 57, are joined together by means of cap screws 55. Gasket 56 provides the necessary fluid tight seal. As shown in FIGURE 1, an oxidizing gas is supplied to pipe 11 by means of T 46 to which the end opposite pipe 11 plugged at 4S which can serve as an opening for steam purging.

The relative sizes of the pipes composing burner 10` are major factors since, as previously explained, the burner is designed to carry out the herein described process where the volumes and velocities of the gases are of importance, as well as their proximity to one anotherduring combustion. Central oxygen tube 11 is a standard one inch pipe having an internal diameter of approximately 1.049 inches while pipe 12 is also a standard size having an internal diameter of about two and one half inches. Pipes 23 are a standard one quarter inch with an internal diameter of about .364 inch and a Wall thickness of about .OSS inch as compared with a wall thickness of .133 inch for pipe 11. Comparing the area of chambers and 25 after pipes 23 are placed in chamber 25 one will find that the remaining area or the area of pipes 23 as well as the triangular portions 26 and 5d are a little over two times or approximately 2.262 times larger in area than chamber 20.

A better understanding of the importance of the foregoing described dimensions can be had through an explanation of the operation of the burner and the flow of fluid materials therethrough. Oxygen inlet pipe 47 is in communication with a suitable supply of oxygen and also has a means for regulating and measuring the flow of oxygen to chamber 2). In a similar manner, gas inlet pipe 35 is connected to a suitable source of natural gas and also a regulatory and metering lmeans. Since the foregoing mentioned regulatory and metering mechanisms are of the standard variety, they are not shown in the drawing. With cool water flowing into chamber 30, oxygen and natural gas are introduced from their respective sources into chambers 29 and 25, respectively. To give the desired volumes of the two gases as they emerge from the nozzle portion 21 from the burner, oxygen is introduced at a rate sufficient to give it a velocity of about three and one half times that of the natural gas passing through chamber 25. This increased velocity of the oxygen when coupled with the fact that the area of chamber 25 is about twice as large as chamber 20 will give a net volume of about one and one half times as much oxygen as natural gas as the streams emerging from their respective chambers. The longitudinal configuration of chambers 20 and 25 as well as their parallel relationship with respect to each other will impart to the oxygen and natural gas a parallel and coaxial flow pattern. An expansion of the materials takes place immediately in front of the burner as is shown in FIGURE 2 of the drawing which gives the characteristic flame-like pattern to the gases. The fact that the central oxygen stream has a faster velocity than the surrounding natural gas stream will draw the natural gas into the oxygen gradually over a considerable distance. The distance of course is determined by the relative velocity of the two gases as well as the cross sectional areas which have been previously described. Not only does the directing of the natural gas and the oxygen streams in the described parallel manner effect a gradual intermixing with a consequent reduction in noise but, additionally, that portion of the natural gas emerging from between the small triangular portions 26 will be in closer contact with the oxygen stream than the gas emerging through and from tubes 23. At the same time, the gas passing along the inside portion of tubes 23 most adjacent to the exterior wall surface of central pipe 11 is farther removed from the outermost surface of the oxygen stream than the natural gas passing along the immediate exterior wall of pipe 11. This difference of course is the thickness of the wall of tube 23 which is only about .O88 of an inch. However, this difference is sufhcient to prevent an immediate intermixing of portions of the gases until they are a considerable distance from the burner. It will thus -be seen that it is the natural gas which passes through the triangular portions which is drawn into the central oxygen stream first, then gas passing through those portions of tubes 23 most adjacent to pipe 11, and finally, the gas from the more remote areas of tubes 23 and the larger triangular sections 50. By having tubes 23 contacting the outside of pipe 11 an alternating contacting and noncontacting barrier is in effect formed with pipe 11. It is apparent that tubes 23 serve to effect a faster velocity for portions of the otherwise normal interface of the two streams in a circumferentially distributed manner with respect to the central stream.

Tubes 23 not only impart a linear and parallel direction to the natural gas stream but they also serve to evenly distribute the natural gas around the oxygen stream. As a consequence of this, the llame has a smooth firing effect and is not as erractic as when, two parallel concentric pipes are employed alone. The smooth firing of course also aids in reducing the noise of combustion.

While the natural gas and oxygen streams emerging from burner 1o under the conditions herein described, and the gas `being combusted, a flame of about ten feet in length is produced which is caused by the gradual intermixing of the two gas streams over the designated ten foot length. Even tho-ugh the burner is operated inside a confined area, such as a furnace, the noise is so minimal that it is not obvious under the customary mill operations.

lt will be noted in FIGURE 2 of the drawing that tubes 23 extend a short distance into nozzle portion 21 and beyond tube 11. This particular arrangement can be altered by aligning the ends of tubes 23 with tube 11 or reversing the described pattern and having tube 11 extend beyond the ends of tubes 23. However, the preferred arrangement is to have tubes 23 somewhat extending beyond tube 11 since the natural gas passing through tubes 23 will be withheld longer from mixing with the oxygen stream. Neither is it essential that pipe 12 extend beyond tubes 23 nor oxygen pipe 11. The extension shown in the drawing does tend to constrict the outer most portions of the natural gas stream and prevent it from diverging outwardly.

lt has been determined that the flow of a gas through a one inch pipe, such as pipe 11, at a velocity greater than 1080 ft./ sec. will cause noise. Thus the liow rate through pipe 11 must be less than this velocity. The minimum useful rate for iiow through central pipe 11 is about 230 ft./sec. lt has been found that the best operating flow rate for the oxygen is between 230 and 950 ft./sec. and about 800 ft./sec. has been found to work best. Thus in run number one of Table 1 where the oxygen is introduced at 17,500 cu. ft. per hour, the velocity of the oxygen is about 810 ft./sec. This velocity is considered optimum in the present design of the burner.

In describing the placement of tubes 23 in chamber 2S reference was made to the fact that the tubes are brazed to the outer wall surface of pipe 11. This fabrication offers the advantage of allowing complete removal of pipe 11 as well as pipes 23 for replacement or cleaning without disturbing the outer wall of the burner defined by pipe 13 which in most instances is permanently mounted in a furnace.

From the foregoing description of the present burner it is apparent that there is provided apparatus for the combustion of fluid fuels at high temperatures and with high B.t.u. capacities which effects a reduction in noise which prior to this invention was not possible. The present burner can be fabricated without the need of special tools or materials and also has a minimum number of parts. lt occupies a relatively small amount of space in a furnace since it is only four inches in diameter in its largest transverse cross section and less than 42 inches in length as measured from the gas inlet to the face of the burner.

It will be apparent that certain modifications and changes will be necessary for adaptation to specific materials from time to time as will `be suggested to those skilled in the art. it is intended that all such modifications and changes as come within the spirit of this invention are intended as being within its scope as best defined by the appended claims wherein there is claimed:

1. A burner for burning combustible fluid fuels in large volumes with minimum noise comprising a first central chamber and a second chamber adjacent and concentric with said first chamber, combustible fluid fuel and oxidizing gas inlet means independently communieating with said first and second chambers at one end of each said chambers, said chambers opening away from said inlet means in a nozzle portion for deiiverisg a Afiuid fuel stream and an oxidizing gas stream, la pluraL ity of tubular members disposed in said second chamber in longitudinal yalignment with said chamber and forming with the outer wall of said first chamber a first concentric row of a plurality of triangular spaces between said tubular members and said wall in the nozzle portion as well as a second concentric row of triangular spaces defined between outer surfaces of said tubular members spaced from said first row triangular spaces, said tubular members constructed and arranged in said second chamber to permit passage of one of said streams through said tubular members and all of said triangular spaces and cooling means associated with said chambers to cool said nozzle portion.

2. The burner as defined in claim 1 wherein said first 'and second chambers are formed from two concentrically disposed pipes and said tubular members are secured only to the surface of one of said pipes, so that the smaller cenral pipe can be easily removed from said burner.

3. The burner as dened in claim 1 wherein said tubular members are abutted against each other around said central chamber.

4. The burner as defined in claim 1 wherein all of said tubular members have substantially the same inside and outside diameters.

5. The burner as defined in claim 4 wherein said inlet means communicating with said central chamber is oxygen inlet means and said inlet means communicating with said second chamber is natural gas inlet means.

6. The burner as defined in claim 5 wherein said second cham-ber with said tubular members has a cross sectional area about twice as large as that of said central chamber.

7. The burner as defined in claim 6 wherein said cooling means is an outer concentric chamber in communication with a supply of cooiing Water and defining a concentric wali portion extending beyond said tubular members.

References Cited UNITED STATES PATENTS 1,204,359 1l/1916 Kemp et al. 158-109 1,341,266 5/1920 Deemar 158-99 1,721,381 7/1929 Ellis 239-425 2,015,934 10/1935 Hepburn.

2,034,932 3/1936 Whitcomb et al.

2,308,902 1/1943 Weller 15S-117.5 X 2,360,548 10/1944 Conway 15S-117.5 2,369,235 2/1945 Jaros 158-104 2,655,986 10/1953 Pennington 239-105 3,076,642 2/1963 Dhenein 266-41 FREDERTCK L. MATTESON, JR., Primary Examiner.

H. B. RAMEY, Assistant Examiner.

Claims (1)

1. A BURNER FOR BURNING COMBUSTIBLE FLUID FUELS IN LARGE VOLUMES WITH MINIMUM NOISE COMPRISING A FIRST CENTRAL CHAMBER AND A SECOND CHAMBER ADJACENT AND CONCENTRIC WITH SAID FIRST CHAMBER, COMBUSTIBLE FLUID FUEL AND OXIDIZING GAS INLET MEANS INDEPENDENTLY COMMUNICATING WITH SAID FIRST AND SECOND CHAMBERS AT ONE END OF EACH SAID CHAMBERS, SAID CHAMBERS OPENING AWAY FROM SAID INLET MEANS IN A NOZZLE PORTION FOR DELIVERING A FLUID FUEL STREAM AND AN OXIDIZING GAS STREAM, A PLURALITY OF TUBULAR MEMBERS DISPOSED IN SAID SECOND CHAMBER IN LONGITUDINAL ALIGNMENT WITH SAID CHAMBER AND FORMING WITH THE OUTER WALL OF SAID FIRST CHAMBER A FIRST CONCENTRIC ROW OF A PLURALITY OF TRIANGULAR SPACES BETWEEN SAID TUBULAR MEMBERS AND SAID WALL IN THE NOZZLE PORTION AS WELL AS A SECOND CONCENTRIC ROW OF TRIANGULAR SPACES DEFINED BETWEEN OUTER SURFACES OF SAID TUBULAR MEMBERS SPACED FROM SAID FIRST ROW TRIANGULAR SPACES, SAID TUBULAR MEMBERS CONSTRUCTED AND ARRANGED IN SAID SECOND CHAMBER TO PERMIT PASSAGE OF ONE OF SAID STREAMS THROUGH SAID TUBULAR MEMBERS AND ALL OF SAID TRIANGULAR SPACES AND COOLING MEANS ASSOCIATED WITH SAID CHAMBERS TO COOL SAID NOZZLE PORTION.

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