US2805649A - Fluid heater furnace - Google Patents

Description

Sept 10,.1957 H. SElDL ETAL 2,805,549

' FLUID HEATER FURNACE;

Filed Sept. 11, 1955 INVENTORS fiererz Seid/ BY flndreasfi'f'rin ATTORNEY FLUED HEATER FURNACE Herbert Seidl and Andreas Sift-in, Oberhausen, Rhineland,

Germany, assignors to The Babcock & Wilcox Company, New York, N. Y., a corporation of New .lersey Application September 11, 1953, Serial No. 379,674 Claims. (Cl. 122-235) The present invention relates to a multi-chambered furnace structure which includes as its firing means a cyclone furnace suitably of the form disclosed in U. S. Patent 2,594,312. The furnace chambers are formed with fluid conducting tubes which may be arranged, for example, as fluid heating elements of a vapor generating unit. As disclosed in the patent, a fuel burning furnace of the cyclone type is especially adapted for the burning of ash-containing solid fuel in a coarsely pulverized or granular" form and under conditions which result in furnace temperatures above the ash fusing temperature, whereby the residual ash is converted into molten slag for continuous discharge from the furnace.

As customarily constructed, a cyclone type furnace is of circular cross section and horizontally arranged, and comprises a primary furnace chamber through which the burning fuel and air are caused to move in a substantially helical path along the circumferential Wall. The fuel is rapidly reduced to gaseous products of combustion which are discharged from the furnace through a central throat passage at one end, and to molten slag which drains through a lower slag outlet, usually at the same end.

A cyclone furnace, when used as the heating source for a vapor generating unit, is customarily arranged to discharge into a secondary furnace chamber which is of special construction to eliminate substantially all the remaining ash and slag particles in the high temperature heating gases and, furthermore, to cool the heating gases below the initial deformation temperature of the fuel ash before the gases contact with any bare fluid heating surfaces which lie beyond the secondary chamber. Slag entering from the cyclone furnace, or furnaces, is discharged from the secondary furnace through a bottom.

slag outlet. Suitably, all gases discharging from the secondary chamber are directed through a slag collecting grid or screen and thence into an adjoining chamber of increased cross sectional area wherein the walls are formed with fluid conducting elements which are arranged to receive heat by radiation. In passing into the larger radiation chamber it is possible for the gases to continue along their original flow path and thus fail to completely fill the radiation chamber, particularly if the latter increases in cross section along the path of the gases. As a result, the gases are insufliciently cooled during their passage through the slag screen and thus are not freed of molten slag particles which then are deposited on surfaces Within the succeeding chamber.

The present invention therefore provides a particular form of furnace structure whereby gases flowing from the secondary chamber are caused to be distributed throughout the total extent of the slag screen and also throughout the total cross section of the succeeding radiation chamber. For a secondary furnace having opposing upright walls which are continued as walls of a wider radiation chamber, one of such walls may be formed with a gas inlet into the secondary chamber and the opposite nite I tare atent Patented Sept. 10, 1957 wall formed with an inwardly projecting portion whereby gases are deflected and thereby distributed throughout the radiation chamber. Such a projection may be arranged either in advance of the slag screen, or at a downstream position with respect thereto. If one such wall of the secondary chamber lies in a plane with the corresponding Wall of the radiation chamber, whereas the opposing wall diverges therefrom in the direction of gas flow, thus forming a progressively widening inlet section of the radiation chamber, then the inwardly extending wall projection is more effective if it is arranged on the planar wall which is common to both chambers, and preferably at the upstream side of the slag screen.

The various features of novelty which characterize 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, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawing and descriptive matter in which a certain specific embodiment of the invention is illustrated and described.

The accompanying drawing is a vertical sectional view showing the lower part of a fluid heater furnace constructed as an embodiment of the invention.

In more detail, the drawing shows a multi-chambered furnace structure which includes a primary, cyclone furnace A arranged as the source of heating gases for a vapor generator furnace B which, in a lower portion, is formed with a secondary furnace C arranged to receive all products of combustion from cyclone furnace A. As will be understood, the cyclone furnace A may represent one of several cyclone furnaces arranged in horizontal succession and all discharging into the single secondary furnace C. The upper portion of furnace B is formed as a radiation chamber D which is arranged to receive all gaseous products of combustion from secondary furnace C.

The cyclone furnace A is of the general character disclosed in said U. S. Patent 2,594,312 and thus is formed with a main cylindrical fluid cooled wall 2 which defines an inner combustion chamber 3 of generally circular cross section about a horizontally arranged central axis. A frusto-conical wall portion 4 toward the outer end provides a fuel inlet section into which, from a fuel inlet chamber 5, solid fuel particles in suspension are introduced in a high velocity whirling stream of primary air. Secondary combustion air is introduced into chamber 3 through a series of nozzle ports 7 which are directed tangentially of the circumferential wall 2. At the inner end of cyclone furnace A, a fluid cooled wall 8, arranged at right angles to the cylindrical wall 2, is formed with an inwardly projecting throat section 9 by which a central gas outlet 10 is defined. A slag outlet 12 is formed in a lower portion of end Wall 8. I

The vapor generator furnace B is of rectangular cross section in a horizontal plane, and formed with an upright outer wall 14 having a lower vertical portion 15 horizontally spaced from the inner end wall 8 of the cyclone furnace A, the wall portion 15 forming the outer wall of secondary furnace chamber C. The bottom wall or floor of chamber C is formed with a slag outlet 16 and a connection shaft 17 through which the slag is dicharged beneath the surface of water in trough 18 from which the disintegrated slag is removed by suitable means, such as a scraper belt 19.

The secondary furnace chamber C opens upwardly into a radiation chamber D of increased horizontal cross section, the gases flowing through an upwardly expanding flue passage 21 of which the front and rear walls 23 and 24 are respectively extended to form corresponding walls of chamber D; the front wall 23 being inclined forwardly 3 and upwardly over the cyclone furnace or furnaces 3, and the vertical rear wall 24 coinciding with wall 14 and thus lying in a plane with the vertical outerwall 15of secondary chamber C. A tubularslag screen 25 extends across the gasjllow passage 21 at an upward inclination toward the front wall 23. Directly below the slag screen, a portion of :the rear furnace wall 14 is formed with a wedge-shaped projection or arch 26 which extends approximately half-way across the secondary chamber toward the inner wall 8, the projection suitably being positioned at an elevation intermediate the cyclone furnace gas outlet and the inclined front wall 23 of passage 21. In the arrangement shown, the projection 26 is formed with its upper inclined portion joined to ,wall 24 at the lowermost end of slag screen 25, and thus at a common elevation with the lower end of the inclined front wall 23. The wall projection 26 is formed with horizontally spacednozzles 27-through which, from a conduit 23, air or cooled combustion gases may be directed into the heating gas stream discharging from the secondary furnace C.

The furnace structure, as shown, is formed throughout with fluid cooled walls and thus includes tubes which suitably may serve as fluid conducting elements of an associated vapor generating unit. Accordingly, there is providcd a bottom liquid supply header 2) from which tubes 31 extend upwardly along a margin of the slag outlet 16, thence along a bottom wall portion of chamber C, and upwardly along the upright cyclone furnace end wall 8, the tubes 31 having portions suitably bent and arranged to form the central gas outlet 10 and also the lower slag outlet 12. The upper portions of tubes 31 are continued in a row along the inner face of wall 23. Other tubes 32 extend upwardly from header 29 along a margin of slag outlet i6, thence along a bottom wall portion of chamber C, and upwardly along the upright outer wall of secondary chamber C, the tubes 32 also extending along the inclined lower and upper surfaces of arch 26. Above the arch, certain tubes 32 are continued at horizontal spacings along the vertical wall 24 whereas the remaining tubes 320 are extended forwardly and upwardly in staggered arrangement to form the two lowermost tube rows of slag screen 25. Upper portions of tubes 32a are grouped in a single tube row 34 which extends parallel to tubes 31 along the inclined inner face of wall 23. Additional tubes 35, having their lower inlet ends connected to drum 29, are arranged upright exteriorly of the setting to the elevation of slag screen where intermediate tube portions 35a are extended forwardly and upwardly, parallel to tubes 32a, to formthe two upper tube rows of slag screen 25. Upper portions of tubes 35:: are combinediwith tubes 32a in the single tube row 34 parallel to wall 23.

The opposing side walls of furnace Bare, in known manner not shown, formed as upright fluid cooled walls,

suitably of planar formation, with wall tubes arranged in rows and covered at their inner sides with refractory material 36 to an elevation above the slag screen 25, where entrance is made into the radiation chamber D. The front and rear wall tubes 31 and 32 are similarly embedded in refractory 36 up to the level of chamber D in which tubes associated with all walls are directly exposed to radiant heat of the chamber. Suitably, all tubes of slag screen 25a're individually covered with refractory material as indicated.

As will be understood, the lower drum 29 may also serve as a liquid supply means for tubes in the side walls of furnace B, and similarly,,for tubes associated with the circumferential walls of cyclone furnace A.

In operation of the furnace described, gases entering the secondary chamber C are directed toward the outer vertical wall 14 and thus tend to follow the plane of that wall in discharging to higher elevations. However, by providing the projecting arch 26, the upfiowing gases are deflected thereby toward the front wall 8 which at higher elevations is continued as wall 23 in upwardly diverging relation to wall 14. As a result, the gases entering the upwardly expanding passage 21 are distributed throughout the total cross section of that passage so as to contact the total exposed area of the slag screen 25, and thereafter to fill the upper radiation chamber D.

While in accordance with the provisions of the statutes we have illustrated and described herein a specific form of the invention now known to us, those skilled in the an will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by our 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 fluid heating unit comprising means defining a cyclone furnace of substantially circular cross-section having a gas outlet in one end thereof, means for burning a slag-forming fuel in said cyclone furnace, walls including fluid cooled tubes, defining a vertically elongated furnace having an upper radiant chamber and a lower secondary furnace chamber opening to said gas outlet, said walls including opposed upright walls, means forming an arch extending from one of said upright walls and cooperating with the opposite upright wall to define a substantially restricted gas opening to the lower portion of the radiant chamber, the upper portions of said upright walls extending divergently upwardly from said arch to the upper portion of said radiant chamber thereby providing a gas flow passage in the lower portion of the radiant chamber of gradually increasing horizontal crosssection, and a slag screen including fluid cooled tubes extending completelyacross the lower portion of the radiant chamber in the path of the gas flow from said gas opening and having its lowermost portion disposed above said arch, said arch being arranged relative to said opposite upright wall to deflect the upfiowing gases toward and in impacting relationship therewith and to substantially narrow the flow path of said gases thereby effecting uniform distribution of the gases through the lower portion of the radiant chamber and over substantially the entire screen.

2. A fluid heating unit comprising means defining a cyclone furnace of substantially circular cross-section having a gas outlet in one end thereof, means for burning a slag-forming fuel in said cyclone furnace, walls including fluid cooled tubes defining a vertically elongated furnace having an upper radiant chamber and a lower secondary furnace chamber opening to said gas outlet, said walls including upwardly extending horizontally spaced inner and outer walls, means forming an arch at an elevation above said gas outlet extending from said outer wall and cooperating with said inner wall 'to define a substantially restricted gas opening to the lower portion of the radiant chamber, the upper portions of said inner and outer walls extending divergently upwardly from said arch to the upper portion of said radiant chamber thereby providing a gas flow passage in the lower portion of the radiant chamber of gradually increasing horizontal cross-section, and a slag screen including fluid cooled tubes extending completely across the lower portion of the radiant chamber in the path of the gas flow from said gas opening and having its lowermost portion disposed superjacent said arch, said arch being arranged relative to said inner wall to deflect the upflowing gases toward and in impacting relationship therewith and to substantially narrow the flow path of said gases thereby effecting uniform distribution of the gases through the lower portion of the radiant chamber and over substantially the entire screen.

3. A fluid heating unit comprising means defining a cyclone furnace of substantially circular cross-section arranged with its major axis substantially horizontal having a gas outlet in one end thereof, means for burning a slag-forming fuel in said cyclone furnace, walls including fluid cooled tubes defining a vertically elongated furnace having an upper radiant chamber and a lower second ary furnace chamber laterally adjacent and opening to said gas outlet, said walls including upwardly extending horizontally spaced inner and outer walls, means including portions of the fluid cooled tubes of said outer wall forming an arch at an elevation above said gas outlet extending from said outer wall and having vertically spaced lower and upper inclined portions converging inwardly from said outer wall and co-operating with said inner Wall to define a substantially restricted gas opening to the lower portion of the radiant chamber, the upper portions of said inner and outer walls extending divergently upwardly from said arch to the upper portion of said radiant chamber thereby providing a gas flow passage in the lower portion of the radiant chamber of gradually increasing horizontal cross-section, said outer wall having its upper portion along said gas flow passage in substantially co-planar alignment with its lower portion along said secondary furnace chamber, and a slag screen including fluid cooled tubes inclined upwardly toward said inner wall and extending completely across the lower portion of the radiant chamber in the path of the gas flow from said gas opening, said slag screen having its lowermost portion disposed superjacent said arch, said arch being arranged relative to said inner wall to deflect the upflowing gases toward and in impacting relationship therewith and to substantially narrow the flow path of said gases thereby effecting uniform distribution of the gases through the lower portion of the radiant chamber and over substantially the entire screen.

4. A fluid heating unit having as its firing means a cyclone furnace of generally circular cross-section about a substantially horizontal axis, walls defining a vertically elongated furnace having an upper radiant chamber and a lower secondary furnace chamber, said secondary furnace chamber being arranged adjacent said cyclone furnace and having an upright inner wall formed with a gas outlet from said cyclone furnace and an upright outer wall spaced from said inner wall, said inner and outer walls having upper portions diverging upwardly and forming opposing walls of a tapering gas flow passage opening to the upper portion of 'said radiant chamber, the upper portion of said radiant chamber being of greater horizontal width and cross-section than said secondary chamber, said outer wall having its upper portion along said passage in substantially co-planar alignment with its lower portion along said secondary furnace chamber, said inner wall having its upper portion inclined upwardly and forwardly in upwardly diverging relation to said outer wall, and a tubular slag screen extending across said tapering gas flow passage, said outer wall of said secondary furnace chamber being formed with a wedge-shaped projection arranged to deflect upflowing gases toward said inner wall for effecting distribution of said gases throughout the total extent of said slag screen within said passage, said slag screen being formed of tubes arranged in vertically successive rows inclined upwardly and forwardly across said passage, with the lowermost portion of said slag screen lying adjacent the uppermost portion of said wedge-shaped projection.

5. A fluid heating unit as defined in claim 4 and further including nozzles extending through said wedgeshaped projection for directing gaseous fluid into the upwardly flowing gases of combustion.

References Cited in the file of this patent UNITED STATES PATENTS 2,594,312 Kerr et al Q Apr. 29, 1952 2,709,424 Sifrin May 31, 1955 FOREIGN PATENTS 834,123 Germany Mar. 17, 1952

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