US2822786A - Multiple cyclone furnace unit - Google Patents

Description

Feb. l, 1958 J. KLLING 2,822,786

MULTIPLE CYCLONE] FURNACE UNIT vlnea July 2o, 1955' INVENTOR BM ATTORNEY United States Patent MULTIPLE CYCLONE FURNACE UNIT Johann Klling, Oberhausen, Rhineland, Germany, as-

signor to The Babcock & Wilcox Company, New York, N. Y., a corporation of New Jersey The present invention relates in general to a combus tion apparatus in which a furnace of the slag tap type is fired by means of cyclone burners or furnaces, each of which is generally of the form ydisclosed in U. S. Patent No. 2,594,312, Kerr et al. It is known therefore that a fuel burning component of the cyclone type comprises a cylindrical furnace especially adapted for the burning of ash-containing solid fuel in a coarsely pulverized or granular form, and particularly under conditions which result in furnace temperatures above the ash fusing temperature whereby the residual ash can be continuously discharged from the cyclone furnace as a molten slag. The gases of combustion are discharged through a central outlet at one end, whereas the slag is separately discharged through a bottom outlet at the same end. Two or more of such cyclone furnaces may suitably be formed about horizontally extending axes and furthermore may be arranged to discharge into an adjacent secondary furnace in a generally horizontal direction and thus constitute, for example, the source of heat for an associated vapor generating unit. Slag collected within the secondary furnace is discharged therefrom through a bottom outlet.

In a multiple furnace unit of this type, for full capacity operation, all of the cyclone furnaces are operated simultaneously so that each furnace carries a proportionate part of the total load. For a minimum load condition, one of the furnaces may be operated at its rated fuel load capacity while the remaining cyclone furnaces are idle. It is therefore desirable to utilize cyclone furnaces of relatively small diameters so as to enable an adequate cyclonic action to be maintained in the respective combustion chambers and particularly in that chamber which is selected for separate operation at the minimum load condition.

Heretofore, with a plurality of cyclone furnaces arranged to discharge into a common secondary chamber, of generally rectangular cross section in a horizontal plane, the cyclone furnaces have been arranged in one or more horizontal rows and, in each of such rows, have been symmetrically arranged with respect to a vertical plane midway between opposing side walls of the chamber. The heating gases entering the secondary chamber are deflected downwardly toward the floor of the chamber wherein there is formed a bottom outlet through which slag received from the respective cyclone furnaces may be discharged to the exterior of the unit. The gases are discharged through an upper opening into an adjoining radiant heat absorbing chamber and thence through a succeeding chamber or passage in heat transfer contact with convection heat absorbing surfaces of the unit.

In the secondary chamber, due to the varying temperature conditions at different operating capacities, the temperatures in the vicinity of the bottom outlet may not rbe high enough to maintain a continuous discharge of molten slag therethrough, particularly when operating under partial load conditions, with possibly only a single cyclone furnace in operation. Various measuresvhave been suggested for maintaining secon-dary furnace temperatures sufficiently high in the vicinity of the slag outlet so as to permit continuous discharge of molten slag at all operating capacities. For example, the secondary chamber could be partitioned into separate compartments, corresponding to the number of cyclone furnaces, but with such an arrangement, each compartment would have to discharge into a separate, exterior slag-collecting space which would necessarily` be sealed against the infiltration of air into the furnace. Moreover, the partition walls would have to be fluid cooled and thus formed with fluid conducting tubes which would have to besuitably arranged and connected so as to cooperate with the fluid circulatory system of the associated Avapor generating unit. It would also -be possible to dispense' with the partitions and to provide only a single slag outlet but, with such an arrangement, the slag discharging from the separate cyclone furnaces would have to llow along paths of different lengths and, in the most unfavorable case, slag flowing along the path of maximum length would arrive at the single slag outlet in a highly viscous state and thus initiate a complete blocking of the slag discharge opening.

The present invention therefore provides a multiple cyclone furnace unit wherein, with two or more cyclone furnaces arranged to discharge into a single secondary furnace, there is provided in the floor of the secondary furnace a single slag outlet which is so positioned as to be intensely heated by gases discharging from that par` ticular cyclone furnace which is selected for maintaining partial load operation. For this purpose, although it is not absolutely necessary that the path of such heating gases be the shortest, it is nevertheless important to Vprovide an arrangement in which the llame is caused to sweep directly across the furnace end of the outlet. j

The various features of novelty which characterizeV the 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, advantages and specific objects attained by ence should be had to the accompanying descriptive matter in which certain specific of the invention are illustrated and described.

Of the drawings: Fig. l is a vertical section of a fluid heater furnace constructed as an embodiment of the invention;

Fig. 2 is a diagrammatic vertical section of Fig. l taken along line 2 2, showing a particular arrangement of cyclone furnaces;

drawings and embodiments Fig. 3 and Fig. 4 are diagrammatic verticalsections similar to Fig. 2, cyclone furnaces.

arranged for use in a vapor generating unit, for example,

as an integral component of the total assembly. `Such a furnace suitably includes a vertically elongated ,furnace section A of substantially rectangular formation in a horizontal plane and, as seen in Fig. 2, further includes as its firing means a plurality of cyclone furnacesY l and 2 which are mounted in the front upright wall 3, in horizontally spaced symmetrical arrangement relative to a vertical plane midway between upright side walls V4 and 5. The cyclone furnaces 1 and 2 are formed about par.- allel axes which extend horizontally in a common plane.

As customarily constructed, each cyclone furnace 1, or 2, is of circular cross section and horizontally arranged, substantially as disclosed in the aforesaid Patent 2,594,- 312. Each cyclone furnace is formed with fluid cooled walls and comprises a cylindrical combustion chamber 6 which is red with a crushed or granular fuel, such as bituminous or semi-bituminous coal, the fuel being de'- Patented Fear 1, s`

its operating its use, refer livered thereto in a whirling stream of preheated primary or carrier air from a fuel inlet chamber 7 at the outer end. Preheated air at high velocity is supplied to each cyclone chamber 6 through tangentially arranged secondaryv air inletsV 8 which are 'disposed along the length ofthe chamber. A whirling stream of tertiary air may also beisupplied to the fuel inlet chamber 7 in an axial direction from an outer whirl chamber 9. The products of combustion from cyclone furnaces 1, 2 ow into an adjoining secondary furnace chamber 12 which is formed at the bottom end of furnace section A. The upright front wall 3, as shown, forms the inner end walls of cyclone furnaces 1, 2 and further includes reentrant throat portions 13, 13 which define circular outlets 14, 14 through which the gases of combustion are discharged axially from the respective cyclone furnaces 1 and 2. Slag in a molten state is discharged from the'respective furnaces'l, 2 through bottom outlets 15, 15 which are formed in the cyclone end wall portions of wall 3.

The secondary chamber 12 is formed with a fluid cooled reecting arch 16 by which the gas streams discharging from cyclone furnaces 1, 2 are deected toward the furnace floor 17 where their direction of ow is substantially reversed so as to cause the gases to pass upwardly through a tubular slag screen 18 which is formed asa lower rearward continuation of tubes forming the arch 16. Above and beyond the screen 18, the gases flow through a radiant heat absorption chamber 19 having walls formed, for example, with vapor generating tubes 2,1. The chamber 12 is formed with a single slag outlet 23, suitably of circular cross section, and vertically aligned with the lower depending portion of arch 16.

Ae hereinbefore explained, the position of the slag outlet 23l is directly related to the arrangement of cyclone furnaces so as to maintain a continuous discharge of slag from the secondary chamber 12 at all loads, and particularly including the minimum load condition with only one cyclone furnace in operation. Accordingly, as indicated in Fig. 2, with two cyclone furnaces 1, 2 horizontally spaced in a common horizontal plane, and symmetrically arrangedvbetween side walls 4 and 5 with respect to a central plane of symmetry, a single furnace 1 may be selected as the one to remain in operation at low loads, in which case a singleslag outlet 23 is positioned directly below the cyclone furnace 1 in a vertical plane with its slag outlet 15, and thereby provideA the shortest possible flow path for slag into outlet 23, particularly under the minimum load condition. As a further advantage, the heating gases from furnace lare continuously brought into contact with the upper perimeter of slag outlet 23. In addition, secondary furnace tloor portions 17a and 17b are inclined downwardly toward outlet 23 to further promote the discharge of slag.

Fig. 3 shows a modiled furnace construction in which two cyclone furnaces 1a and 2a are arranged at one elevation, substantially as shown for furnaces 1, 2 in Fig. 2, whereas a third cycloneY furnace 25 is arranged at a higher elevation, with its horizontal axis in the` vertical plane of symmetry. In this modification, the cyclone furnace 1a is selected as the single furnace to be maintained in operation for minimum load requirements and thus determines the location of slag outlet 23a. which, as in the Fig. 2 construction, is positioned adjacent a side wall 5a, and directly below the furnace 1a in a common vertical plane therewith, thereby providing the shortest possible path for slag flowing toward outlet 23a. In this embodiment, the secondary furnace is also formed with oppositely inclined oor portions 17a and 17h which converge downwardly toward the single slag outlet 23a.

Fig. 4 shows a further modification in which two cyclone furnaces 1b and 2b are symmetrically arranged in an upper horizontal plane Whereas a third cyclone furnace 26, for minimum capacity operation, is arranged in the vertical plane of symmetry at a lower elevation. In this form, the slag outlet 23h is located( midway between the side walls 4b and 5b and thus in a common vertical plane with the centrally positioned cyclone furnace 26 which is intended for separate operation at minimum load in addition to being available for operation under higher load conditions. As in other embodiments, oppositely arranged floor portions 17e, 17e converge downwardly toward outlet 23b to facilitate the drainage of slag from the furnace.

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.

What is claimed is:

l. A multiple furnace unit formed with upright walls dening a furnace chamber having as its firing means a plurality of substantially spaced cyclone furnaces cylindrically formed about axes of substantially horizontal and parallel arrangement, one of said upright walls being arranged transversely of said axes and constituting the tiring wall of said furnace chamber, an additional two of said walls being arranged parallel to said axes and forming opposing side walls of said chamber, each of said cyclone furnaces having a central gas outlet and a lower slag outlet each formed in said tiring wall and opening into said furnace chamber, said furnace chamber being formed with a bottom wall in which there is provided a single slag outlet disposed in the same vertical plane as the slag outlet from a selected one of said cyclone furnaces, said bottom wall slag outlet being disposed in a location swept by the gases discharged from said selected cyclone furnace, said bottom wall being inclined downwardly from at least one of said side walls to the position of said bottom wall slag outlet, a reecting arch extending downwardly within said chamber from a front wall position above said cyclone furnaces to a position inwardly spaced from the gas outlets of all said furnaces whereby gases issuing from said cyclone furnaces are deflected downwardly into the vicinity of said bottom slag outlet, and means for delivering a slag forming solid fuel-and-air mixture simultaneously to each of said cy clone furnaces forV effecting full load operation of said unit, said means being selectively operable for delivering a combustible fuel-and-air mixture to only said selected one cyclone furnace for effecting partial load operation of said unit, said selected one cyclone furnace having its slag outlet disposed substantially nearer to said bottom slag outlet of said furnace chamber than the slag outlet of any other one of said cyclone furnaces.

2. A multiple furnace unit formed with fluid cooled upright walls defining a furnace chamber of substantially horizontal rectangular cross section, one of said upright walls being arranged as the firing Wall of said chamber and an additional two of said upright walls being arranged as opposing side walls of said chamber, a plurality of substantially spaced cyclone furnaces formed about substantially horizontal and parallel axes and mounted in said ring wall, each cyclone furnace having a central gas outlet and a lower slag outlet opening into said furnace chamber, said cyclone furnaces being arranged at separate elevations at different distances from one of said side walls, said furnace. chamber having a bottom wall formed with a single slag outlet therein arranged in the same vertical plane as the slag outlet of a selected one of said cyclone furnaces, said bottom wall slag outlet being disposed in a location swept by the gases discharged from said selected cyclone furnace, a reflecting arch having an upper portion inclined downwardly from said firing wall at a position above said cyclone furnaces and having a continuing lower portion substantially upright and disposed in the path 0f gases discharging from said cyclone furnaces for directing such gases into the vicinity of said bottom wall slag outlet, said lower portion of said arch being disposed substantially in a plane with said bottom wall slag outlet, lsaid bottom wall of said chamber sloping downwardly from at least one of said side walls to the position of said bottom slag outlet, and means for supplying a slag-forming solid fuel-and-air mixture simultaneously to each of said cyclone furnaces for effecting full load operation of said unit, said means being selectively operable for supplying a slag-forming solid fuel-and-air mixture to only said selected one cyclone furnace for effecting partial load operation `of said unit, said selected cyclone furnace having its slag outlet disposed substantially nearer to said bottom slag outlet of said furnace chamber than the slag outlet of any other one of said cyclone furnaces.

3. A multiple furnace unit as defined in claim 1 wherein said cyclone furnaces are disposed at a common elevation, said one cyclone furnace for partial load operation being disposed adjacent one of said side walls, and said bottom wall being inclined downwardly toward said bottom slag outlet from the opposite one of said side walls.

4. A multiple furnace unit as defined in claim 1 wherein said cyclone furnaces are arranged at separate elevations in staggered relation.

5. A multiple furnace -unit as defined in claim l wherein Said cyclone furnaces include two cyclone fur naces arranged at one elevation adjacent the respective side walls of said chamber, said one cyclone furnace for partial load operation being arranged at a separate lower elevation intermediate the positions of said two cyclone furnaces.

References Cited in the le of this patent UNITED STATES PATENTS 2,196,377 Bailey Apr. 9, 1940 2,357,301 Bailey et al. Sept. 5, 1944 2,357,303 Kerr et al. Sept. 5, 1944 2,367,193 Blizard Jan. 16, 1945 OTHER REFERENCES B & W Bulletin, G67-A of 1950, page 39.

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