US2812212A - Liquid fuel burner - Google Patents

Description

'Nw-"5 1957 c. E. ROGERS ET AL 2,812,212

LIQUID FUEL BURNER Filed April 17, 1951 Y ll y Mn,-

Mana. ATTORNEY Unted States Patent l2,812,212 Patented Nov. 5, 1957 hice LIQUID FUEL BURNER Application April 17, 1951, Serial No. 221,458

4 Claims. (Cl. 299-114) The present invention relates to liquid fuel burners, and more particularly to fluid atomizing fuel burners for erosive liquid fuels. Y

vIn Ythe successful combustionof a liquid fuel it is desirable to atomizepthe fuel to a fine mist so that combustion air canbe intimately mixed therewith to complete the `combustion process. .Some liquid fuels, such as the residual liquors resulting from acellulosicpulping process, are so erosive, as to reduce the atomizing effect of one or more of the atomizer parts, necessitating frequent replacement-of those parts. Residual liquors resulting from the sulphitecooking process are particularly erosive due t'oA dissolved and suspended solid matter therein and also frequently contain brous material which tends to plug small diameter liquor flow passages in atomizer parts.

'In accordance with the present invention we provide a liquid fuel'burner assembly constructed and arranged to successfullyV atomize erosive liquids without excessive wearlon theatomizer parts. This is accomplished by a novel arrangement of atomizing fluid ow passageways `arranged to intersect a high velocity flowing stream of the 'liquid to Vbe atornized.` The atomizing effect is accomplished out of ydirectcoritact with the confining liquid flow passageway. In addition 'the liquid ow passageway is relatively unobstructed and not susceptible to pluggage due to the presence of fibrous materials in the liquid. The substitution of our burner atomizer assembly has resulted in 'a manifold increase inVK the life of burner parts when compared with the burners heretofore known. Moreover this increased life and avoidance `of excess wear is accomplished while maintaining a degree of atomization at least comparable with the atomizing assemblies of the prior art. f

The .various fea'turesof novelty which characterize our invention are pointed out with particularity in the claims Vannexedto and Iforming a part of this specification. For abetter understandingof the invention, its operating advantages and specific objects attained by its use, reference should be had'tolthe accompanying drawings and descrip .tive-'matter in which wehaveillustrated and described a preferred embodiment vof lour invention.-

.Fig. Al is an elevational' view, partly in section, of a vapor generation unitand furnace incorporating the burn- -ergofthe presentinvention; 'A

Fig. 2 is an enlarged section elevation of the liquid fuel burner; *Figk3 is a further enlarged longitudinal section of the atomizer assembly of the liquid fuel burner;

Fig'. 4 is an end"view of one'element of the atomizer taken on the yline` 4-4 of Fig. 3;, n

Fig. 5 is a longitudinal `section of a modified form of atomizer assembly; y Fig. `6 is an end view of- 'an-element of the atomizer taken ,on the line 6 6 of Fig. 5; and 'Fig..71is an* end view ofthe atomizer tip shown in Figi/5. i

In the illustrated embodiment of the invention the burner is associated with a furnace 10 constructed and arranged for the combustion of a pulp residual liquor resulting from the digestion of cellulosic material in a relatively pure magnesium base cooking liquor. The residual liquor from this process is particularly erosive to burner atomizers and the usual type of steam atomizing burner has had a useful life measured in hours, and when constructed with expensive alloy parts a life not exceeding a few days at best. In this process the residual liquor is preferably burned in suspension and a high degree of spray atomization and thorough mixing with combustion air is highly desirable to complete the combustion process and to cause the conversion of the magnesium in the liquor to a reactive form of magnesium oxide.

Referring to Fig. 1 the furnace 10 is substantially completely lined with high alumina refractory materials. High combustion temperatures are attained in this furnace. As shown, the rear wall 11 of the furnace consists of refractory blocks supported upon fluid cooled tubes 12 with a gas outlet 13 in the rear wall positioned upwardly adjacent the furnace floor 14. The furnace iloor is formed of hollow tile 15 covered with high aluminum refractories, with preheated air delivered to the' front portion of the floor through a valved duct 17, passed through the hollow tiles and discharged into the upflow open pass 18 of an associated vapor generator 2).

.Residual liquor at a concentration of 50 to 60% solids is delivered to the upper portion of the furnace 10 through burner ports 16 positioned in opposite side walls of the furnace. The residual liquor is atomized by the burners, as hereinafter described, mixed with air, and the combustible matter therein burned in suspension within the furnace it). Leaving the furnace outlet 13 the cornbustion gases generatedin the furnace are passed through a series of fluid cooled upright open gas passes V18, 21 and 22 and pass through the convection pass 23 of the vapor generator. Thereafter the gases pass through an air heater 24, and are treated in a supplementary system for the separation of the MgO solids in the gases and for the absorption of sulphur oxides in a wash liquid (not shown). As disclosed in U. S. Patent No. 2,354,175 the time-temperature relationship during the combustion of the residual liquor is quite important in attaining a reactive magnesium oxide solid residue.

Advantageously the combustion air used in the furnace 1@ is preheated to assist in an efficient and rapid combustion of the organic matter in the residual liquor. Air from the forced draft fan 25 is passed through the air heater 24 into a duct 26 for distribution to the furnace i@ through the valved branch duct connections 17, 27 and 2S. 'The duct connections 28 extend upwardly on opposite sides of the furnace to open into a horizontally disposed distributing manifold 3l)k which is provided with a series` of discharge pipes 31 extendingl between the tubes forming the roof of the gas passes 18 and 21and arranged to discharge into the gas stream passing into the gas pass 21. The duct connections 27 likewise extend from the duct 26 to an enclosed housing 33 surrounding the burner ports on the opposite sidesY of the furnace.

Each of the burner ports 16 is provided with an air register and a liquid fuel vatomizer assembly, whereby the fuel and air 'are delivered to the furnace 10 through each port. A vertical elevation (taken along the centerline of a burner port and in a plane perpendicular to the side wall of the furnace) of an individual air register and atomizer assembly is shown in Fig. 2. A ring member v34 having an inwardly tapering surface, and provided with Vcover plate 37 of the air housing y33 is spaced from-and generally parallel to the casing 36, and is connected theretolby a circular series ofbrackets 38. A circular series otcurved air directing blades .40, `each mounted on an individual axis, are interconnected by linkage for simultaneous adjustment from a common exterior lever 39. The blades canbe closedto cut otfairilow totheifurnace, and-canrbe adjustably openedto regulate the quantityof air passing therethrough. Thus inail open (positions, the air-stream passing between adjacent blades140 is given a swirling motion.

'In addition, a slotteddiftusion cone 41 `is positioned in the burner port 16 by the barrel 42 of the liquid fuel burner. The combination of the blades 40 and the diffusion cone 41 `directs the -ow of combustion air` through the port in arwhirling `movement of the air mass surrounding and impinging upon a fine spray of liquor discharged' from `the atomizer tip 43 of the burner. in the embodiment of Fig. 2, the barrel 42 is formed of an elongated `tubular member projecting through a cover plate 44 which is bolted to the `plate 37. The barrel is centered so as to be Vsubstantially coaxial with respect to the member 34, and is exteriorly provided with the conventional coupling provisions for the separate ad.- mission of both liquid .fuel and atomizing fluid, as indicated generally at 4S. The atomizing fluid may be steam, or other gaseous or vapor fluid.

The atomizing assembly of the burner tip 43 is shown in detail in Figs. 3 and 4, and includes an inner and an outer tube 46 and 47, respectively. The tubes are coaxial and define separate passageways 48 and 50 for the liquid fuel and the atomizing fluid. In the arrangement shown, the passageway 48 conducts the liquid fuel while the passageway 50, Abetween the tubes 46 and 47, is utilized for the flow of a tluid, such as steam, used to atomize the liquid in the burner tip. A sprayer head or nozzle 51 is threaded to the end portion of the tube 46 and is provided with a flanged end portion 52 circumferentially engaging an inner shoulder 53 formed in the end portion of the tube 47. The nozzle 51 serves to center and to maintain the desired end-spacing relationship between the tubes 46 and 47. In theconstruction shown an open sided annular chamber 54 is machined in the face of the flanged end portion 52, with a circumferential series of drilled ports 55 providing flow communication between the passabeway 50 and the chamber 54.

An atomizing plate 56 and a tip member 57 are assembled in series abutting relationship to the nozzle 51, and maintained in position by a cap member 58 which is threaded onto the outer end portion of the tube 447. An inwardlyextending flange 60 of the cap member 58 engages a correspondingly recessed outer portion of the tip 57 to maintain coaxial alignment of the assembly and to provide a substantially unobstructed flow path for the lliquid fuel passing through the passageway 48.

As shown in Figs. 3 and 4, the atomizing plate 56 `is formed with an open sided annular chamber 61 on the `face thereof, `and a circumferential series of drilled openings 62 extend from the chamber through the body of the plate 56 in a direction parallel to the axis of the central bore or throat 63.

A plurality of slotted passageways 64 are formed in one face` of the plate 56, extending from the chamber 61 inwardly to the confining wallof the throat 63. While .the centerline of each passageway lies in a plane parallel to the axis of the throat and the member 51, the planes of the centerlines of individual passageways are not in parallelism. In the construction shown in the drawings `the passageways 64 are elongated in a direction parallel to the axis of the throat and are milled in the plate 56 from the `face thereof to a depth corresponding with the depth of the annular chamber 61. Since the atomization effectiveness of the fiuid passed through the passageways `64 to intersect the stream of liquid flowing through the :throat 63 is greatly influenced by the velocity of the presvsure fluid jets dischargedfrom the passageways, thetdimansions and number of-jets will vibe selected to attain the desired results with a preferred ow rate of fluid. While in the embodiment shown, the passageways 64 are rectangular in cross-section for ease of fabrication, it will be understood the cross-sectional shape can be varied without adversely affecting the atomizing efficiency of the apparatus.

As shown in Fig. 4, the passageways 64 are arranged in pairs with the intersection of the centerlines of each pair occurring within the throat 63 at a position intermediate the circumference and the longitudinal axis of the throat. With lthe arrangement shown and described, the pairs of intersecting jets tend to establish a series of swirls in the liquid stream, with the number of swirls corresponding with the numberof pairs of passageways provided in the plate 62. In addition, the jets promote an effective spinning effect within the'liquid stream so that on emerging from the throat the liquid is thoroughly atomized. The action of the jets on the liquid stream tends to compress'the ,stream and to minimize the erosive contact of the swirling Aliquid .upon thetconning walls.

Each pair of passageways 64, such Vas 64A and 64B, yis arranged twith the centerline of the `passageway 64A spaced from and parallel to a radial line intersecting ,the longitudinal axis of the throat 63, while the centerline of the passageway 64B intersects 1the centerline of passageway 64A `within `the throat with `an included angle of the order of 30 to 36.

The tip 57 isprovided with an outwardly flaring conical surface 65 diverginggfrom the circumference of the throat 63 at an angle of approximately 25 to 30. The tip member is subjected to some internal wear with the expansion ofthe atomized liquid stream in discharging from the atornizer.

In a modified Vform of the invention, as shown in Figs. 5, 6 and 7, the tip is provided with a series of fluid jets which tendto recompress the discharging atomized liquid stream and protect the inner surface of the tip member against erosion.

Referring to Figs. 5 and 7, the tip member 70 is pro- -vided with four equally spaced ports 71 opening attheir inner ends to the chamber 61 of the adjoining plate 56 and extending through the .body of the tip to discharge into the atomized liquid stream discharging through the throat 73 of the atornizer. The ports 71 converge, with their longitudinal axes lying along 4the surface of a right cone having a base angle of 60, and `with'the axisof each displaced 30 from a line drawn from the apex ofz the cone to the base and passingthrough one end of the port. The jet impulse of the fluid passing through the ports '71 and impinging on the atomized liquid stream discharging through the throat 73 is directed in the same direction as the swirl imposed by the fluid jets `discharging through the passageways 64.

It is sometimes of advantage tolrestrict `thecross-seotional area of the throat in ithe atomizing plate, partie ularly when `the burner is normally operated at a liquid flow capacity less than the maximum. Such a restriction is shown in the modified constructionof plate 56 4shown in Fig. 5, where the throat '13 -is provided with conically tapered inlet end portion 72, and a cylindrical mixing portion 74 of smaller diameter than the passageway 48. Otherwise the plate 56 is provided with kthe ports 62, chamber 61 and passageways v64, as in the plate 56 con struction previously described.

By way of example and not of limitation, an atomizer of the type described hada capacity of approximately 3600 pounds per hour of sulphite liquor having a solids content of approximately 60%. The liquor was delivered to the burners at a pressure of 60 poundsper square inch gauge, and a temperature of 230 F. The throat 63 of the burner was 2%.; inches in diameter, and 8 passageways 64 were used, each of -which was 1/s" long and -had a width of .016. Steam, at a-pressure of 100 pounds per square inch gauge,-was used as the atomizing fluid.` lEven though the sulphite liquor was highly erosive the `burner was used continuously for over two months without an appreciable reduction in the atomizing effectiveness of the atomizer. Other designs of burners had previously been used under identical operating conditions and comparable atomizing eliiciencies, but the effective life of such burners had never exceeded a period of approximately two days.

While in accordance with the provisions of the statutes we have illustrated and described herein the best form and mode of operation of the invention now known to us, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the vspirit of the invention covered by our claims, and that certain features of our invention may sometimes be used to advantage without a corresponding use of other features.

We claim:

1. As an article of manufacture, a sprayer plate comprising a disk having a central bore with merging frustoconical and cylindrical portions, means defining an annular groove in one face of said disk radially spaced from and surrounding the cylindrical portion of said central bore, a plurality of orifices extending from said groove to the other face of said disk, and a plurality of circumferentially spaced passageways extending inwardly from said groove to the cylindrical portion of said central bore, the passageways of each pair positioned with their centerlines intersecting at an acutevangle within and at a diameter less than the diameter of the cylindrical portion of said central bore.

2. As an article of manufacture, a sprayer plate comprising a disk having a central bore, means defining an annular groove in one face of said disk radially spaced from said bore, a plurality of orifices extending from said groove to the other face of said disk, and a plurality of circumferentially spaced passageways extending inwardly from said groove to the central bore of said disk, alternate passageways positioned with their centerlines tangent to a circle of less diameter than the diameter of said central bore, the remaining passageways positioned with their centerlines tangent to a second circle of lesser diameter than said first mentioned circle.

3. A liquid fuel burner comprising walls deiining coaxial passageways for liquid fuel and steam respectively, a sprayer plate operatively connected to said passageways and having a central bore forming a continuation of said liquid fuel passageway, an annular groove in one face of said sprayer plate radially spaced from and surrounding said bore and in communication with said steam passageway, a plurality of circumferentially spaced steam iiowv passageways leading from said annular groove to' said bore, alternate passageways positioned with their center-V lines tangent to a circle of less diameter than the diameter of said central bore, the remainingpassageways positioned with their centerlines tangent to a second circle of lesser diameter than said iirst mentioned circle, and a discharge tip coaxially engaging said sprayer plate and having internal surfaces diverging outwardly from the bore of said sprayer plate.

4. A liquid fuel burner comprising walls defining coaxial passageways for liquid fuel and steam respectively, a sprayer plate operatively connected to said passageways and having a central bore forming a continuation of said liquid fuel passageway, an annular groove in one face of said sprayer plate radially spaced from and surrounding said bore and in communication with said steam passageway, a plurality of circumferentially spaced steam iow passageways leading fromv said annular groove to said bore, alternate passageways positioned with their centerlines tangent to a circle of less diameter than the diameter of said `central bore, the remaining passageways positioned with their centerlines tangent to a second circle of lesser diameter than said iirst mentioned circle, a discharge tip coaxially engaging said sprayer plate and having internal surfaces diverging outwardly from the bore of said sprayer plate, and means forming a series of ports in said tip arranged to project converging jets of steam into the liquid fuel `discharging through the diverging internal surfaces of said discharge tip.

References Cited in the tile of this patent UNITED STATES PATENTS 1,100,141 McConnell June 16, 1914 1,462,680 Bliss July 24, 1923 1,526,006 Mersch Feb. 10, 1925 1,843,821 Joslyn Feb. 2, 1932 1,884,931 Voorheis Oct. 25, 1932 2,117,388 Woolley May 17, 1938 2,240,161 Mueller Apr. 29, 1941 2,306,141 Richardson Dec. 22, 1942 2,335,317 Sherman Nov. 30, 1943 2,576,373 Wetzel Nov. 27, 1951 FOREIGN PATENTS 150,761 Great Britain Sept. 6, 1920 322,257 Great Britain Dec. 5, 1929 465,691 Great Britain May 13, 1937

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