US2918117A - Heavy fuel burner with combustion gas recirculating means - Google Patents

Description

J. J. GRIFFIN HEAVY FUEL BURNER WITH COMBUSTION GAS RECIRCULATING MEANS Filed Oct. 4, 1956 2 Sheets-Sheet 1 IN VEN TOR BY ids/Wm Dec. 22, 1959 J. J. GRIFFIN 2,918,117

HEAVY FUEL BURNER WITH COMBUSTION GAS RECIRCULATING MEANS Filed Oct. 4, 1956 2 Sheets-Sheet 2 INVENTOR. John J Griffin Affamey lfmAVY FUEL BURNER WITH COMBUSTION GAS RECllRCULATllNG MEANS John J. Griffin, Huntington, N.Y., assignor to Petro- Chem Process Company, Incorporated, New York, N.Y., a corporation of Delaware Application October 4, 1956, Serial No. 613,867

1 Claim. (Cl. 158-1) This invention is concerned with liquid fuel burners in general. More specifically the invention deals with a vertical or upshot type of burner, to be used in furnaces generally and more particularly in commercial types having large heating capacity. Furthermore, the invention is especially concerned with an upshot burner for handling heavy fuels.

In referring to liquid fuels, it is intended to include both fuels that are principally supplied as liquids and then are atomized in the burner, as Well as fuels that are basically solid in their original form, but which have been ground so as to be in powder form or at least in comparatively finely divided particles. The latter solid type of fuel being one which may be ejected from a nozzle in the form of a suspension, such that it acts as a fluid.

It has been found that where heavy fuels are employed, difficulty is encountered in obtaining complete combustion thereof. This is particularly true where the burner is employed as a so-called upshot burner. The problem is especially noticeable in making use of high viscosity high gravity refinery pitches. Such fuels which include relatively large percentages of pitch, produce a situation such that even after the burner is operating under full heat conditions, there is encountered a dripping of unburned fuel which falls back into the primary air supply structure of the burner. This creates a clogging in addition to the messy accumulation of pitchy oils. Thus, the operation is relatively inefficient in addition to providing the operational difficulties already mentioned.

It is pointed out that similar difficulties are to be eX- pected where an upshot burner employs other types of fuels which have heavy constituents, such as some finely divided types e.g. powdered coal and the like.

In view of this situation, it is an object of this invention to provide a superior type of upshot burner for burning heavy types of fuels.

Another object of this invention is to provide im proved structure for an upshot type of burner such that a portion of the combustion products as they leave the stream being ejected from the burner nozzle, are circulated back into the stream of the combustion supporting gases that are being introduced around the burner nozzle.

Another object of this invention is to provide an upshot burner of a superior construction such that no difficulty is encountered in burning the heaviest grades of fuels therewith, and a complete and entire combustion of such fuels is obtained.

Briefly, this invention includes a heavy liquid fuel burner that is comprised of a nozzle means for atomizing a liquid fuel. The burner also being comprised of venturi means surrounding said nozzle means and having an opening at one end thereof for admitting combustion sustaining gas, and an opening at the other end thereof for ejecting combustion products. Further, the burner comprises means surrounding said venturi means for returning some of said combustion products into said venturi means near the throat thereof. Also the said venturi means has a passage near the throat thereof for recirculating the returned portion of said combustion products.

Some embodiments of the invention are described beloW in more detail, as an illustration thereof. These embodiments are hereafter described and illustrated in the drawings, in which:

Fig. 1 is a vertical cross-section view showing a double block type burner mounted in the floor of a furnace or the like, taken along the lines 11 of Fig. 2 looking in the direction of the arrows; I

Fig. 2 is a cross-section plan view taken along the lines 2-2 of Fig. 1;

Fig. 3 is a vertical cross-sectional view of a single block type burner;

Fig. 4 is a horizontal cross-sectional view taken along the line 44 of Fig. 3, looking in the direction of the arrows; and

Fig. 5 is a plan view partly in cross-section, taken along the lines 55 on Fig. 3.

Referring to both Figs. 1 and 2 of the drawings but primarily with reference to Fig. 1, it will be observed that the burner consists of a fuel supply pipe 11 which stands vertically and is centrally located along the vertical axis of the entire burner. At the upper extremity or tip of pipe 11 there is a nozzle 12 that may take any desired form, partly depending upon the type of fuel to be employed. For the purposes of illustration, it will be assumed that the pipe 11 and the nozzle 12 together make up a steam-atomizing type of burner nozzle. It is pointed out that the burner itself will operate equally as well where the atomizer nozzle 12 is of a mechanical type.

Surrounding the entire nozzle, made up of nozzle or fuel pipe 11 and nozzle tip 12, there is a cylindrical block of refractory material 13 which has a venturi passage 14- centrally located therein. It will be appreciated that this cylindrical block 13 may be constructed of other types of heat resistant material as Well as a refractory, e.g., it may be made of stainless steel, among others. Therefore, it is not intended to preclude other materials even though the block 13 is referred to as a refractory as a matter of convenience in the descriptions.

The relative location of this venturi passage 14 and the refractory cylinder 13, with respect to the fuel pipe 11 and its nozzle 12, is such that they are coaxial. The nozzle 12 is centrally located within venturi passage 14, slightly below a minimum diameter, or throat section 15 of the venturi passage 14. The refractory block 13 is supported by a housing structure 19 which may be attached in any convenient manner to an outer layer or skin 20 of the furnace. In the illustrated arrangement, it will be observed that there is welded to the furnace skin 20 a wide band or ring 21 of the same structural material as furnace skin 20. Welded to the lower edge of ring 21, there is an annular disc or supporting plate 22. The housing 19 proper is attached to the disc or supporting plate 22 by any convenient means such as by welding for example. The housing 19 includes an annular disc or ring 23 which lies just beneath and in contact with, the disc 22; a band or short cylindrical side wall member 24, which is welded to ring or disc 23; and a fioor plate or disc 25, which is welded to the lower edge of the wall member 24.

Centrally located in the floor plate 25 of the housing 19 there is an opening or hole 28 which lies directly under, in alignment with the lower end of the venturi passage 14, so as to coincide therewith. Welded or otherwise attached to the floor 25 around the edges of the hole 28, there is a nozzle supporting structure 29 which has a bearing sleeve 30 carried thereby. Bearing 30 in its turn, slidably carries the nozzle pipe 11.

It will be observed that nozzle tip 12 is vertically adjustable in its position, or location, within the venturi passage 14 by means of any convenient mechanical arrangement such as that illustrated. This structure includes a rack 34 that is securely attached to one side of fuel pipe 11 and lies longitudinally there along, and a pinion 35 which engages with the rack 34 for causing a vertical movement or positioning, of the rack by a vertical sliding up and down of the attached pipe 11 upon rotation of the pinion 35. There is also a handle 36 attached to a shaft 37 which carries the pinion 35 securely attached thereto for rotation therewith. Thus, .a mechanical adjustment may readily be made for regulating the flame of the burner if desired, by changing the relative position of nozzle tip 12 within the length of the venturi passage 14.

It will be observed that the refractory material block 13 is cylindrical in general outline, but that there are a plurality of vertically extending notches or passages 40 that are circumferentially spaced from each other around the outside surface of the block 13. At the bottom of each of the passages 40 there is a short radial opening 41 which passes through the refractory block 13 so as to connect each passage40 with the venturi passage 14 somewhat below the minimum diameter or throat section 15. Surrounding the refractory block 13, there is a relatively thin cylindrical cowl 42. This cowl 42 sits closely against the maximum diameter portion of the refractory block 13 and forms the outer wall or boundary of the vertical portion 40 of recirculation passages 40, 41. At the top edges of the cylindrical body portion of cowl 42 there is a frusto-conical ring 43 which is integrally connected to the top edges of the cowl 42, and which extends inward to an extent such that the top edge of the ring 43 lies directly over the inside, or minimum radius curved surface of the recirculation passages 40. Cowl 42 including its inward sloping edge 43, is made of a high temperature resistant material, eg alloy steel, or the like.

Situated coaxially with, and surrounding the upper portion of the burner structure so far described, there is a muflle tube 48 which may be formed of a refractory material and which extends upward through the full depth of a refractory floor-layer 49 of the furnace.

It will be observed that there are primary air openings or ports 52 situated in the mounting structure 29 that supports the fuel nozzle pipe 11. These primary air inlets may be adjustable if desired as by means of the illustrated structure wherein there is an outer layer 53 and an inner layer 54 which are relatively movable in rotation about the bearing 30 so that the size. of the ports or openings 52 may be regulated by setting the outer layer 53 more or less in correspondence with the inner layer 54 in respect to the holes through each. In like manner there is a secondary, or outer air inlet structure that includes a plurality of openings or ports 55 which allow the secondary air to pass there-through into the space surrounding cowl 42 and inside of the mufile tube 48. Here again the effective size of the openings 55 for the passage of secondary air may be made adjustable by providing for relative sliding movement between the inner side wall member 24 and an outer layer 58 that may be attached in any convenient manner such as by slideably resting on a flange 59 which is attached to the floor plate 25 by welding.

Operation The operation of the burner may best 'be described with r'eference'to Fig. 1 where it will be observed that the fuelis forceably ejected in an atomized spray vertically upward from the nozzle tip 12, as indicated in the drawing by the diverging lines shown. As indicated above,

this stream of finely divided particles of fuel may be created in any feasible manner such as by use of a steam atomizing nozzle, or by use of a so-called mechanical type of atomizing nozzle. It will be appreciated that the mechanical type of spray nozzle for liquid fuels, is one where a relatively small sized orifice is employed with a high pressure supply of the liquid fuel introduced thereto. In this way the ejected stream of the liquid fuel is ejected in a forceable manner, but at the same time is broken up into finely divided particles, i.e., is atomized.

The atomized fuel is ignited initially by a conventional gas lighter (not shown) or by inserting a hand torch through the primary air openings 52 into the venturi passage 14.

Such jet stream of atomized fuel induces a flow of intake air that is drawn upward through the venturi passage 14, after it has entered via primary air intake passages 52. A combustible mixture of fuel and air is thus formed within the venturi passage 14, and the flame ordinarily maintains itself beginning a relatively short distance away from the ejection end of nozzle tip 12. In other Words the products of combustion become and remain nascent for some distance while still within the venturi passage 14 and after leaving the same. Then, as these products of combustion continue upward and out of the burner proper toward the muffle tube 48, and the inside of the given furnace or wherever the burner is employed; they pass the top edges of cowl 42, so that the portion of this stream of nascent and other combustion products at its outer edges become diverted by the frusto-conical ring 43 of the cow] back into the recirculation passages 40 around the edges of the refractory block 13 (within which venturi passage 14 is formed). Such recirculation of hot combustion products takes place by reason of standard venturi action wherein a lower pressure is created near the throat section 15 of venturi passage 14. Thus, the frusto-conical ring 43 of the cowl acts substantially as a suction manifold and the diverted portion of the nascent combustion products will be drawn down through the passages 40 and via radial openings 41 into the incoming air stream which constitutes the primary source and surrounds nozzle pipe 11 and the nozzle tip 12. In this manner these hot nascent combustion products cause the primary source of the incoming air stream to be highly heated prior to reaching the lower edges, or beginning, of the burner flame. In this manner the incoming mixture is heated above the vaporization temperature so as to cause complete revaporization of any heavy particles of fuel which are forming and tending or beginning to fall out of the fuel stream. Consequently, there is complete vaporization of the entire fuel employed even though the burner is operated as an upshot burner in a directly vertical position.

In the embodiment of Fig. l, the complete combustion of the fuel employs some secondary air intake through ports 55, as indicated above. This amounts to about twenty to forty percent of the total air intake.

For different grades of heavy fuel the nozzle pipe 11 and its ejection tip 12 may be adjusted but normally, as already pointed out, the tip is always slightly below the venturi throat.

This construction and burner arragement uses mechanical means to adjust the burner nozzle, not particularly to change the flame shape, but to vary the quantity of flue gas recirculated. The heavier fuels will require more recirculated products to insure operation without dripping.

It should be noted that the simple mechanical adjustment of the burner nozzle in this invention can be safely made while the burner is in operation thereby to obtain the optimum conditions for any given fuel.

However, in an emergency if it is necessary to use a light grade of fuel, this may be provided for by raising the nozzle pipe 11 until the ejection tip 12 is at or near the top of the venturi passage and thus eliminate the recirculation effect which would be unnecessary under such conditions.

A modified form of burner in accordance with the invention is illustrated in Figs. 3, 4, and 5. This form of burner is a so called single block type of burner, which means that the entire burner structure is contained in a single unit housing, and all of the combustion supporting air is drawn in at a single air inlet for the burner. Basically the elements of the burner are the same as the elements employed in the inner portion of the above described modification. Consequently, the details of such elements and their functional inter-relation, will not be described again in great detail.

Referring to Figs. 3, 4, and 5, it will be noted that there is illustrated a portion of a furnace floor 62 which has the usual thick layer of refractory material supported by an outer shell 63 of structural material, such as steel or the like. Located in an appropriate opening through the floor 62 there is a cylindrical cowl 64 which may be constructed of any feasible, heat resistant material such as stainless steel. Integrally attached at the upper edge of cowl 64 there is a frusto-conical ring 65 which acts to cause a diversion of some of the nascent products of combustion, in the manner described previously in connection with the first described modification illustrated in Figs. 1 and 2.

concentrically located within the cowl 64, there is a cylindrical block of heat resistant material 68, which has an internal cross sectional configuration on the order of a venturi type of passage, as clearly illustrated. Located around the outer periphery of block 68 there are plurality of axially extending passages formed by grooves 69, which extend from the top of the block 68 downward inside of the surrounding cowl 64 most of the way to the bottom of the block 68. Connecting with the lower end of each of these axial passages 69 there is a corresponding radial opening or passage 70, so that there exists a plurality of passages from the outer edge at the top of the block 68 downward and into the throat of the venturi passage within the block, somewhat below the minimum diameter of this venturi passage.

Attached to the shell 63 of the furnace in any convenient manner, such as by means of a plurality of long bolts 72, there is a supporting plate 73 for holding a burner supply nozzle 74, that is located at the tip of a supply pipe 75. The pipe 75 is supported in any convenient manner on the plate 73; for example, sleeve bearing supports 76 may be employed. Here again, in this modification there is a provision for cylindrical sliding adjustment for the position of nozzle 74 within the burner. Such adjustment may be carried out by any convenient structure, such as the schematic showing of a rack 80 and pinion 81, plus a handle 82 for rotating the pinion 81.

Also supported by the plate 73 there is a plurality of vanes 85, equally spaced around a circle concentrically located around the supply pipe 75. These vanes 85 may be mounted in any convenient manner, such as that illustrated, e.g. by being attached to a shaft 86 at the bottom edge of each thereof. The shafts 86 are secured in place by means of threadably received nuts 87 on the ends thereof. It will be noted that these vanes 85 are set at an angle toward the tangential, all in the same direction around the circle. The purpose of these vanes 85 is to cause the incoming air to be directed generally in a rotational spiraled manner as it is drawn through the burner.

It is pointed out that the particular construction used employs narrow grooves 90 cut out of the block 68 at the peripherial location for each of the supporting bolts 72. This allows easy access to the bolts for mounting and dismounting the burner structure while also reducing the quantity of heat resistant material used in the block 68.

It is ponted out that in this modification, the entire amount of combustion supporting air needed is drawn in at the burner, without any provision for introduction of secondary air. However, in general, the operation of the burner with respect to the recirculation of nascent products of combustion, is substantially as described above in connection with the other modification.

While particular embodiments of the invention have been described above in compliance with the applicable statutes, this is not to be taken as in any way limiting the invention, but merely being descriptive thereof.

It is claimed:

A heavy fuel burner comprising an upstanding atomizer nozzle having an outlet for a stream of atomized fuel at the top thereof directed upward, a cylindrical block of refractory material having an axial venturi passage therein surrounding said nozzle for mixing air with said stream of fuel and ejecting combustion products from the top of said passage, means for supporting said nozzle coaxially within said cylindrical block, said supporting means being located adjacent to the bottom of said venturi passage, means forming primary air inlet openings associated with said nozzle supporting means for admitting air to make a combustible mixture, means for readily adjusting said nozzle axially relative to said venturi passage for obtaining best mixing action and for using the burner with light fuels if necessary, a heat resistant thin cylindrical cowl surrounding said cylindrical block and extending axially above the top of said venturi passage, an upwardly and inwardly extending frustoconical ring formed around the top edge of said cowl to provide a surface for deflecting a portion of the nascent combustion products, groove means forming auxiliary longitudinal passages in the outer surface of said cylindrical block, said groove means being circumferentially spaced around said block, means forming transverse passages radially connecting said means forming auxiliary passages with said venturi passage below the min mum diameter of the throat thereof to complete paths for recirculating said deflected combustion products, a mufile tube surrounding said cowl, and additional air inlet means for supplying secondary air between the inner Wall of said muffie tube and the outside of said cowl.

References Cited in the file of this patent UNITED STATES PATENTS 1,164,854 Oesterlen Dec. 21, 1915 1,737,681 Plassmann Dec. 3, 1929 2,143,259 Clarkson Jan. 10, 1939 2,174,663 Keller Oct. 3, 1939 2,224,544 Keller Dec. 10, 1940 2,333,531 Ferguson Nov. 2, 1943 2,532,740 Speer Dec. 5, 1950 2,601,667 Permann June 24, 1952 2,701,608 Johnson Feb. 8, 1955 2,793,686 Phillips May 28, 1957 FOREIGN PATENTS 704,082 Great Britain Feb. 17, 1954

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