US2793626A - Fuel burning apparatus - Google Patents

Description

May 28, 1957 E. HUBEL FUEL BURNING APPARATUS Filed June 16, 1955 lv f l 1 I ATTORNEY States Patent Oflice 2,793,626 Patented May 28, 1957 FUEL BURNING APPARATUS Ernst Hiihel, Oberhausen, Germany, assignor to The Babcock & Wilcox Company, New York, N. Y., a corporation of New Jersey Application June 16, 1953, Serial No. 362,024

Claims priority, application Germany June 18, 1952 8 Claims. (Cl. 122--235) The present invention relates in general to apparatus for burning ash-containing solid fuels under conditions which result in a high output of high temperature gaseous products of combustion, substantially free of entrained slag or ash particles. More particularly, the invention is directed to a structural arrangement of furnace for burning certain varieties of coal which, due to their high coking characteristics, are preferably maintained in suspension throughout the coking stage and thus until the coke particles are no longer sticky whereupon the particles may be directed into the main combustion zone for movement along walls thereof at increased velocity.

Accordingly, the invention provides for the combustion of solid fuel in successive stages, in successive chambers, with a combustible fuel-air mixture travelling in a helical path through one chamber at relatively low velocity, and in a continuing helical path through a succeeding chamber at increased velocity. Suitably, the transition from one chamber to the other is effected without substantial change of available flow area through the connecting passage or passages. For this purpose, the successive chambers are preferably of cylindrical formation and disposed in concentric relation about a common central axis, with fuel and carrier air being initially admitted to an outer chamber, and the ultimate products of combustion discharged from an inner chamber.

In the operation of cyclone furnaces heretofore constructed, a burning fuel-air mixture is caused to travel therethrough at high velocity and thus remains within the furnace for only a very short period. Thus, for a cyclone furnace of prior construction providing a total heat output of Q:5,000,000 kcal./hr./m. the stay period within the furnace is about one-tenth of a second. Although the coarser fuel particles are retained in the fLlIIlElCt; by the slag film on interior wall surfaces, only a part of the total interior space may be available for active combustion, particularly with coals having strong coking characteristics, due to the progressive heating of the fuel up to the combustion stage, and the degasification, whereby the expenditure of energy to provide high velocities of fuel movement during these preliminary stages is practically wasted.

However, by providing a separate heat insulated chamber through which an incoming coal-air mixture is caused to move at relatively low velocity, with the fuel particles in suspension, ample time is afforded to enable the coal particles to be maintained in suspension until such particles are no longer sticky and the coke skeleton is firm, whereupon the fuel-air stream may be directed into a succeeding chamber, suitably of a cyclone type, in which combustion may be completed. As herein disclosed, the fuel inlet chamber is formed as an integral addition to a cylindrical cyclone chamber and furthermore is arranged concentrically therewith to provide an annular surrounding space. Such an arrangement of inlet chamber results in a saving of space and heat and, despite its spatial restriction, permits variations to be made in its structural formation especially in respect to features affecting the movement of carrier air therethrough.

The various features of novelty which characterize my invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated and described a specific embodiment of my invention.

Of the drawings:

Fig. l is a vertical section of a cyclone furnace constructed as an embodiment of the invention; and

Fig. 2 is a horizontal section of Fig. 1, taken along line 2--2.

As shown in the drawings, a cyclone furnace A, of cylindrical formation about a vertical central axis, provides inner and outer chambers B and C of circular cross section, in concentric arrangement with respect to the axis. The inner chamber B constitutes a combustion chamber of the cyclone type having an upper portion of its cylindrical defining wall 5 conically contracted as at 6 toward a central circular gas outlet 7. A lower portion of wall 5 is similarly contracted at 8 toward a central circular slag outlet 9 at the bottom, from which position wall portions 10 diverge downwardly toward a slag disposal means, not shown, where a known form of seal against infiltration of air is effected.

The outer chamber C is of annular formation about an upper portion of chamber B, with its inner Wall 12 formed in common with portions of wall 5 in :a manner hereinafter described, and its outer wall 14 being formed with an intermediate cylindrical portion 15 concentric with the inner cylindrical wall 5. The upper and lower ends of chamber C are respectively closed by conical upper and lower end wall portions 16 and 17, of which the portion 16 is joined at its upper end to the conical upper end wall portion 6 of chamber B, at the same inclination, and end portion 17 is joined at its lower end to the main cylindrical furnace wall 5.

The outer cylindrical wall 14 of the annular chamber C is formed with circumferentially spaced inlet ports 13 through which, with the aid of nozzles 19, a fluent mixture of solid fuel particles suspended in air is directed into an upper region of chamber C, in approximately tangential relation to the inner surface of wall 14. The inner circumferential wall 12 of chamber C is formed with circumferentially spaced ports 21 which open into the central chamber B from a lower region of chamber C adjacent its inclined bottom wall 17. The ports 21 are formed with opposing sides 22, 22 which converge inwardly toward chamber B so as to direct the burning fuelair streams tangentially into that chamber, in conformity with the directional movement within chamber C. At an elevation below ports 21, the cylindrical wall 5 of chamber B is formed with circumferentially spaced inlet ports 23 through which, from nozzles 24, secondary air is directed into the central chamber B, in approximately tangential relation to the inner surface of its circumferential wall 5.

The entire furnace wall structure is further defined and cooled by means of tubes 25 through which fluid from an exterior source may be circulated; for example, by including such tubes in the circulatory system of an associated fluid heating unit, not shown, suitably in the manner disclosed in U. S. Patent No. 2,594,312.- In the main cylindrical wall 5, below ports 21, the tubes 25 are arranged in a circular row, with suitable intertube spaces at intervals to allow for the installation of secondary air inlet nozzles 24. At a lower elevation, certain tubes 25a are bent inwardly, and then outwardly, to define the lower slag outlet 9, whereas other tubes 25b continue downwardly, as indicated, for connection, with tubes 25a, to a fluid supply means, not shown.

From an elevation subjacent ports 21, every fifth tube 25c, throughout the circumference of wall 5, is continued upwardly to define the upright wall portions 20 between successive ports 21. Above the ports 21, an intermediate portion of each tube 250 is formed with several branches 25d which, as diagrammatically indicated, define the upper major portion of wall 12, between ports 21 and the conical end wall portion 6. From the same elevation subjacent ports 21, the remaining tubes 25s are extended upwardly within the outer wall 14 of annular chamber C. The tube lengths 25c and 25a are also included in the annular upper end wall formations 6 and 16 which surround the gas outlet 7. As will be understood, all such wall cooling tubes may be arranged with their upper discharge ends connected to a suitable outlet header means, or the like.

In each of the outer walls, as above described, the tubes 25 and designated portions thereof are desirably provided in known manner with welded-on studs, and with refractory material 26 filling the intertube spaces and covering the tubes on both sides in their respective rows. A gas tight metallic casing 27 is provided for all exterior furnace wall surfaces.

During operation of the furnace, a solid fuel, such as coal, of relatively small particle sizes, is introduced in a stream of primary air through each of the nozzles 19 which open tangentially into the annular preparation chamber C, suitable provision being made in starting-up for igniting the fuel upon its initial introduction into the chamber. The burning fuel-air streams move in a generally helical path downwardly along the outer circumferential wall 14 where, at the bottom, the burning mixture and slag are discharged through ports 21 into the central cylindrical chamber B, the slag following the slope of the lower wall 17 and gravitating toward and through the bottom outlet 9.

The rotational movement of the fuel-air mixture is maintained in chamber B in the same direction, and the combustion of fuel continued and completed therein, by the tangential introduction of secondary air at high velocity through nozzles 24 which are circumferentially spaced in two rows at an elevation subjacent ports 21. In the course of combustion within chamber B, the helical movement of the burning mixture is continued along wall in an upward direction, with the gases of combustion discharging through the upper central outlet 9, while the slag is deposited in a molten state on adjacent wall areas along which it flows downwardly toward the bottom outlet 9 through which it is discharged.

While in accordance with the provisions of the statutes I have illustrated and described herein a specific form of the invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of other features.

I What is claimed is:

1. A cyclone furnace having walls defining an inner cyclone chamber of substantially circular cross section about an upright axis and an outer fuel inlet chamber of annular formation about said cyclone chamber, said walls including a main circumferential wall extending substantially throughout the height of said furnace and having a portion common to both of said chambers, means for introducing a combustible mixture of ash-containing fuel and air into said annular chamber and'elfecting a helical movement thereof downwardly along the outer circumferential wall of said annular chamber, said common wall portion being formed with circumferentially spaced openings through which the burning fuel-air mixture is directed laterally into a lower-portion 'ofsaid inner chamber, said outer chamber having a ci'rcuini ferentially continuous bottom end wall joined to said common wall portion at a location subjacent said openings, means for introducing secondary air into said cyclone chamber and effecting a helical movement of the burning mixture therein toward the upper end of said inner chamber, and a slag outlet and a gas outlet discharging respectively from a lower and an upper portion of said cyclone chamber.

2. A cyclone furnace having a main circumferential wall extending substantially throughout the height of said furnace and defining an inner cyclone chamber of substantially circular cross section about an upright axis, an outer circumferential wall defining with said main wall an annular outer chamber having an annular lower end wall of upwardly concave conical formation and joined throughout its inner periphery to said main wall at an elevation upwardly spaced from the lower end of said furnace, means for introducing air and ash-containing fuel in suspension into an upper portion of said annular chamber and effecting a helical path of travel thereof downwardly along said outer circumferential wall, said main wall being formed with circumferentially spaced openings through which gases and slag from said outer chamber are discharged into said inner chamber, said openings being arranged superjacent said lower end wall, and nozzle means for introducing secondary air tangentially into said inner chamber at an elevation subjacent said openings for continuing and completing combustion of the fuel, said nozzle means being arranged to maintain the same rotational direction of movement of fuel and gases within said inner chamber as Within said annular chamber, said inner chamber having a slag outlet formed at its lower end and a gas outlet formed at its upper end.

3. A cyclone furnace having walls defining an inner cyclone chamber of substantially circular cross section about an upright axis and an outer fuel inlet chamber of annular formation about said cyclone chamber, said walls including a main circumferential wall having a portion common to both of said chambers, means for introducing a combustible mixture of ash-containing fuel and air into said annular chamber and effecting a helical movement thereof downwardly along the outer circumferential wall of said chamber, said common wall portion being formed with openings through which the burning fuelair mixture is directed downwardly into said inner chamber, means for introducing secondary air into said cyclone chamber and effecting a helical movement of the burning mixture therein toward the upper end of said inner chamber, and a slag outlet and a gas outlet discharging respectively from a lower and an upper portion of said cyclone chamber, said annular fuel inlet cham ber being closed at the bottom with a conical wall converging downwardly toward said main wall and joined thereto directly below said openings, said fuel inlet chamber being closed at the top with a conical wall converging upwardly over said inner chamber in the direction of said gas outlet.

4. A cyclone furnace having walls defining an inner cyclone chamber of substantially circular cross section about an upright axis and an outer fuel inlet chamber of annular formation about said cyclone chamber, said walls including a main circumferential wall having a portion common to both of said chambers, means for introducing a combustible mixture of ash-containing fuel and air into said annular chamber and effecting a helical movement thereof downwardly along the outer circumferential wall of said chamber, said common wall portion being formed with openings through which the burning fuel-=air mixture is directed downwardly into said inner chamber, means for introducing secondary air into said cyclone chamber and effecting a helical movement of the burning mixture therein toward the upper end of said inner chamber, and a slag outlet and a gas outlet discharging respectively from a lower and an upper portion of said cyclone chamber, said annular fuel inlet chamber is closed at the bottom with a wall of upwardly concave formation sloping downwardly and inwardly toward said -main circumferential wall, said openings in said common wall portion having inclined bottom surfaces formed as extensions of the sloping upper surface of said bottom wall.

5. A cyclone furnace as defined in claim 4 and further comprising fluid conducting tubes arranged upright within said main circumferential wall, said etubes being disposed in part between said openings through which gases and slag are discharged from said outer chamber.

6. A cyclone furnace as defined in claim 5 and further comprising other tubes having 'lower portions interspersed with said tubes within said main circumferential wall, said other tubes having upper portions extending within said inclined bottom wall of said annular chamber and continuing toward said upper gas outlet.

7. A cyclone furnace having a main circumferential wall defining a cyclone chamber of substantially circular cross section about an upright axis, an outer circumferential wall defining with said main wall an annular outer chamber having an annular lower end wall of upwardly concave conical formation and joined at its inner periphery to said main wall, means for introducing air and ashcontaining fuel in suspension into an upper portion of said annular chamber and effecting a helical path of travel thereof downwardly along said outer circumferential w-a'll, said main wall being [formed with circumferentiallly spaced openings through which gases and slag from said outer chamber are discharged into said inner chamber and nozzle means for introducing secondary air tangentially into said inner chamber at an elevation subjacent said openings for continuing and completing combustion of the fuel, said nozzle means being arranged to maintain the same rotation direction of movement of fuel and gases within said inner chamber as within said annular chamber, said inner chamber having a slag outlet formed at its lower end and a gas outlet formed at its: upper end, said main wall including a ciroumferentially continuous upper wall portion at elevations above said spaced openings, said furnace further comprising fluid conducting tubes arranged upright within said main wall, said tubes at the elevation of said openings being arranged with single tube lengths disposed in wall portions separating said openings, said singletube lengths at the upper ends of said openings being formed with branches to provide an increased number of fluid conducting tube length portions for said circumferential'ly continuous wall portion above said openings.

8. A cyclone furnace as defined in claim 7 wherein said walll tube branches are restored to single tube lengths in wall portions adjacent said upper gas outlet.

References Cited in the file of this patent UNITED STATES PATENTS 1,180,792 Norrman Apr. 25, 1916 2,625,791 Yellott Jan. 20, 1953 FOREIGN PATENTS 587,240 Great Britain Apr. 18, 1947

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