US2868179A - Fuel burning apparatus - Google Patents

Description

Jan. 13, 1959 o. LOTZ FUEL BURNING APPARATUS 2 Sheets-Sheet 1.

Filed May 31, 1952 INVENTOR Otto lozfz BY M ATTORNEY FIG.1

Jan. 13, 1959 o. LQTZ 2,868,179

FUEL BURNING APPARATUS Filed May 31. 1952 2 Sheets-Sheet 2 FIG.2

INVENTOR ATTORNEY United States PatentG FUEL BURNING APPARATUS OttoLotz, Oberhausen, Germany, assignor to The Babcock & Wilcox Company, New York, N. Y., a corporation of New J ersey.

Application May 31, 1952, Serial No. 290,876

2 Claims. (Cl. 122-235) The present invention relates to fuel burning apparatus in which the primary. combustion space is suitably providedby a cyclone. furnace or furnaces generally of the type disclosed in U. S. Patent No. 2,357,301. The apparatus is thus especially adapted for burning ash containing solid fuels in a relatively coarsely pulverized or granular condition, with combustion being effected at furnace chamber temperatures above the ash fusion temperature. whereby there is maintaineda discharge. of incombustible ash residue from each cyclone furnace as liquid slag. The cyclone furnaces are suitably formed about horizontally extending axes and furthermore are arranged to discharge into an adjacent secondary furnace in a generally horizontal direction, thereby constituting the source of heat for an associated vapor generating unit.

The granular fuels normally used in such cyclone furnaces have particle sizes of and under, and contain as a result of the fuelcrushing operation a proportion of dustlike particles, known as fines. The fuel and air mixture is introduced in the combustion chamber through a tangential inlet arranged to effect a whirling motion of the fuel and air mixture in a helical path axially of and toward the opposite end of the furnace. In operation the entering fuel and air stream is rapidly ignited and the centrifugal effect of the whirling stream causes the ash particles releasedfrom the burning fuel particles to deposit in a molten condition on the furnace wall and form a film or layer of molten slag thereon on which the larger fuel particles are caught and burned.

In prior embodiments of horizontally arranged cyclone furnaces, the gases of combustion are caused to enter a lower part of the secondary furnace at one side of a steeply inclined dividing wall or arch by which the gases are reflected downwardly toward the floor of the secondary chamber, the flow of gases continuing. in an upward direction at the downstream side of thearch and thence into a radiation chamber where heat of the gases is transferred to fluid conducting elements disposed at elevations beyond the arch. Due to the bilateral heating, this intermediate wall is subject to ahigh degree of wear which is difiicult to detectby observation. It also obstructs all free observation of the openings through. which the furnace gases and the slag pass from the primary combustion space into the secondary chamber. In certain prior forms, a cyclone furnace has been arranged about a vertical axis in which case, if the gases are discharged downwardly, the secondary chamber boundary opposite the cyclone gas outlet must be formed as a slag bottom. If the gases from a vertical cyclone are discharged upwardly, it is necessary to provide an increased height of secondary chamber above the cyclone. Hence, neither of these forms of cyclone furnaces constitutes a prototype either for the task of protecting the gas reflecting wall against excessive wear when the axial position of the cyclone is approximately horizontal, or for possibly enabling observation to be made of the cyclone furnace operation.

The present invention therefore provides a secondary chamber of which the rear wall is positioned directly op- 2,868,179 Patented Jan. 13, 1959 ing arranged at locations approximately opposite the slag outlets of individual cyclone furnaces.

The foregoing measure is applicable also when several cyclone furnaces, which are formed about parallel axes and with gas outlets at one end, are arranged alongside of one another at a common level. The secondary chamher and possibly the radiation chamber may then be subdivided according to the number of cyclone furnaces, suitably by upright fluid cooled Walls formed at least in part by fiuid conducting tubes of the associated vapor generator. In this manner, during partial load operation, the

heat output from each cyclone furnace in service will be confined mainly to the respective portion of the heat absorbing chamber into which the gases are discharged. For thispurpose, it may also be advantageous to make the cubic capacity of each secondary chamber section smaller than that of the corresponding cyclone furnace chamber.

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 an embodiment of the invention.

Of the drawings:

Fig. 1 is a vertical sectional view of a cyclone furnace. installation constructed in accordance with the invention; and

Fig. 2 is a partial vertical section of the furnace shown in Fig. 1, taken along line 2 2.

Figs. 1 and 2 illustrate a cyclone furnace installation: in which horizontally arranged cyclone furnaces 5 constitute the source of heat for an associated vapor generating. unit of which only the lower portion is shown. Each cyclone furnace 5 is formed with a circular cylindrical boundary wall 6 which is constructed in known manner of fluid conducting cooling tubes of the unit, suitably lined. with a refractory composition at the inner side of the wall.

The coarsely ground ash-containing solid fuel is sup, plied to each cyclone. furnace 5 in a high velocity-stream ofprirnary air whichis introduced tangentially into thev cyclone burner or head 7 through a conduit 8. The. fuel-air mixture rapidly ignites and the burningstream: fio-ws longitudinally of the cyclone chamber in a helical.

r tions, the ash content of the fuel is rapidly released in a molten condition and, due to the centrifugal effect thereon, is deposited in a layer at the perimeter of the chamber to provide a sticky surface on which the larger fuel particles are caught and burned. The lighter fuel particles burn mainly in suspension while in the whirling stream along the circumferential wall. The slag coating or film which forms on the furnace walls rapidly reaches an equilibrium thickness and, as additional slag is. deposited on the walls, the excess molten slag will flow to the bottom of the chamber and discharge through a bottom slag outlet 12, suitably formed in the upright furnace end wall 13 which separates the cyclone chamber from the secondary furnace 14.

. The upright wall 13, being common to both the primary and secondary furnaces, is formed with a series of reentrant throat sections, as shown, each of which defines an outwardly flaring outlet 16 through which the gases of combustion are discharged from a cyclone furnace directly into the adjacent secondary furnace or chamber 14, the bottom of which is formed with slag outlets 17 through each of which slag drains into a gas tight shaft 18 having its lower end immersed in a pool I of water in trough 19 to a suflicient depth for the shaft to be maintained under water seal. A scraper belt 21 is installed in each trough 19 for removing the granulated slag. The secondary chamber 14 includes an outer rear wall 23, substantially parallel to wall 13, and formed with closable openings 24 therein directly opposite the slag outlets 12 from the respective cyclone furnaces 5 which, as illustrated, are formed about horizontally inclined parallel axes and arranged alongside of one another at a substantially common elevation. Opposing walls 13 and 23 are lined with tubes 13a and 23a, as shown, having their lower ends communicating with header 25 from which a cooling fluid is directed therethrough. Water or other cooling liquid is supplied from header 25 to cooling tubes 6a which are associated with circumferential walls of cyclone chambers 5.

As seen in Fig. 2, the secondary furnace 14 is formed with tube cooled side walls 26, as shown, and furthermore is subdivided by tube walls 27, 28, 29 into four compartments A, B, C and D. Each slag shaft 18 is arranged symmetrically relative to each pair of cyclone furnaces 5, so that it receives the slag draining from two such furnaces. The bottom wall or floor of the secondary furnace is formed with successive tube-cooled portions 30 of opposite slope so as to converge down-,

wardly in pairs toward each slag discharge outlet 17. The slag openings 12 of the respective cyclones are arranged sufliciently close above the floor of the secondary furnace to enable gases discharging from the cyclone furnaces to sweep the floor panels 30. The cooling tube walls 27 and 29 are divided at the top to form slag screens or slag catching grids 31, 32, 33, 34. The tubes of slag screens 32, 33 combine with tubes of the central wall 28 to form a tube wall 35 which vertically traverses the radiant chamber 36 arranged above the secondary chamber 14 and the cyclone furnaces 5. In the upper portion of the shaft forming the radiant chamber 36 there are arranged tube panels 37 of a steam superheater of the fired steam generator, the panels 37 being spaced far enough apart so that as little slag as possible will deposit on their tubes. The outer walls of radiant chamber 36 are formed as upper extensions of fluid cooled walls defining the secondary chamber 14, the rear and sidewalls 23 and 26 continuing vertically, and the front walls 13 including a rearwardly inclined portion 38 extending over the cyclone furnaces 5. The outflow tubes of slag screens 31, 34 are suitably extended through upper portions of side walls 26 for connection to uptake headers 39 as shown.

It will be understood, without further detailed disclosure, that all fluid conducting tubes and headers associated with the foregoing embodiments may be connected in known manner to insure the continuous flow of cooling fluid therethrough, for example, by including such pressure parts in a natural fluid circulation system.

While in accordance with the provisions of the statutes I have illustrated and described herein the best form and mode of operation 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 my invention may sometimes be used to advantage without a corresponding use of other features.

I claim:

1. Fuel burning apparatus comprising cyclone furnaces formed about horizontally extending parallel axes at a common level, each of said furnaces having a central gas outlet and a lower slag outlet formed in an end wall of each furnace, a secondary chamber of relatively narrow cross section axially 'of said cyclone furnaces and receiving gases and slag discharging therefrom, a radiant chamber extending above said common level and receiving said gases from said secondary chamber, and means including upright. cooling tube walls for sub-dividing said secondary chamber into gas flow compartments corresponding in number to the number of said cyclone furnaces whereby gases and slag from individual furnaces are discharged into the respective compartments, said upright walls having tubes arranged with portions extending across upper ends of said compartments and forming slag screens in the path of gases passing to said radiant chamber.

2. Fuel burning apparatus according to claim 1 wherein the compartments associated with two successive cyclone furnaces are formed with floors inclined downwardly toward one of said upright tube walls and terminating in horizontally spaced relation to one another adjacent the lower end of said one wall for defining a separate lower slag outlet discharging under liquid seal to an exteriorly positioned slag disposal means.

References Cited in the file of this patent UNITED STATES PATENTS 2,166,199 Shoemaker July 18, 1939 2,244,144 Drewry June 3, 1941 2,357,301 Bailey et al. Sept. 5, 1944 2,357,303 Kerr et al. Sept. 5, 1944 OTHER REFERENCES B and W Bulletin G 67-A of 1950, page 39.

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