US2709424A - Vapor generator furnace - Google Patents

Description

May 31, 1955 A. SIFRIN VAPOR GENERATOR FURNACE Filed Aug. 4 25, 1951 INVENTOR Judi-ea: Jzfrm BY v I ATTORIEY United States Patent VAPOR GENERATOR FURNACE Andreas Sifrin, Oberhausen, Germany, assignor to The Babcock & Wilcox Company, Rockleigh, N. 1., a corporation of New Jersey Application August 25, 1951, Serial No. 243,606

Claims priority, application Germany September 1, 1950 2 Claims. (Cl. 122-235) The present invention relates to furnaces and more particularly to the construction and operation of furnaces which serve as the firing means for vapor generating apparatus and which are arranged for the combustion of ash-containing solid fuels while providing for the separation and discharge of residual ash in liquid form.

Theinvention is especially concerned with a furnace structure having adjoining primary and secondary furnaces or furnace chambers, of which the primary chamber is provided by a cyclone furnace of the general type disclosed in U. S. Patent Bailey et al. 2,357,301, September 5, 1944. In a primary furnace of the character disclosed in the aforesaid patent, a solid fuel such as coal, in a crushed or coarsely pulverized condition, is burned at furnace chamber temperatures above the ash fusion temperature, whereby the residual ash is maintained in a molten condition so as to permit its discharge and removal from the furnace as a liquid slag.

In cyclone-fired vapor generator installations heretofore constructed, the gases discharging from the cyclone outlet are directed through channel-like passages which are formed between fluid cooled elements whereby, in flowing through such passages, the velocity of the slag-bearing gases is increased and further, the gases are sharply deflected through 90 or 180 prior to entering the radiation chamber in which the major portion of the fluid heating surface is contained. In other prior constructions, the slag-bearing gases from the cyclone chamber are caused to pass through a secondary furnace chamber in a sub stantially rectilinear direction, toward the opposite outer rear wall, whereupon the gases are discharged into an upper radiation space through an opening adjacent the rear wall. Consequently, in such prior constructions, the slag-bearing gases are in constant contact with cooled walls whereby the gases are quickly cooled together with the slag particles entrained therein. Under such conditions, the slag, instead of being deposited in fluid condition at the bottom of the secondary chamber, and being maintained fluid, may continue to accumulate at the bottom of the chamber in a relatively non-fluid mass and thus present serious slag removal difficulties particularly during partial-load operation of units having a plurality of cyclones discharging into a common secondary furnace chamber.

In accordance with the present invention, the hot gases discharging from the primary cyclone furnace are directed into an adjoining unobstructed secondary furnace chamber, of substantially increased volume, wherein the gas stream is caused to follow a U-shaped flow path of considerable length, and relatively free from the cooling effect of inner wall surfaces of the chamber. The gases are discharged through an opening in the roof of the chamber adjacent the end through which the gases enter the chamber. The secondary chamber thus serves as a slagseparating zone wherein as a result of the character of flow path provided, and the maintenance of high gas temperatures at reduced velocities of flow, a further and substantially complete separation of molten slag particles is effected, prior to movement of the gases into contact with the major heat absorbing elements of the unit, the separated slag being maintained in fluid condition at the bottom of the chamber for continuous removal. Moreover, the U-shaped deflection of the gas stream is effected within the wholly unobstructed interior of the secondary chamber and thus within a space devoid of gas deflecting devices or the like whereby the separated molten slag particles are permitted to fall freely to the bottom of the chamber. Provision is made for preventing the escape of slag with the discharging gases.

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 drawing and descriptive matter in which I have illustrated and described an embodiment of the invention.

The accompanying drawing consists of a single side sectional view showing the lower portion of a vapor generating unit in which the heating gases are supplied by a cyclone furnace, or by a plurality of such furnaces, as may be desired.

The cyclone furnace 1 as included in the illustrative embodiment is essentially a horizontally inclined cylinder of Water cooled construction substantially as disclosed in the aforesaid U. S. Pataent 3,357,301. The circumferential walls of the cyclone furnace are defined predominantly by closely spaced tubes 2 which are operatively connected, in known manner, into the fluid circulatory system of the associated vapor generator to be later described. The furnace includes a cylindrical fuel inlet or burner section 4 of reduced diameter into which a stream of crushed coal, for example, is introduced tangentially in a stream of carrier air by means of a primary air-fuel pipe 5. The fuel inlet section 4 is joined to the main body portion of the furnace by a conical transition section 6. A supply of additional air may be admitted tangentially of the fuel inlet section through pipe 7.

The main supply of air is delivered to furnace 1 through a main air duct 8 which opens into a secondary air port 9 arranged intermediate the ends of the furnace in tangential relation to the inner wall surface thereof, and having its total discharge area subdivided into a plurality of sections, each under control of suitable damper means, not shown.

At the opposite discharge end of the cyclone furnace 1, the annular wall 12 is predominantly formed by fluid conducting tubes 13 of such arrangement as to provide a rearwardly flaring throat section 14 of circular cross section by which a central gas outlet 15 is defined. With the gas outlet so arranged, the rearwardly moving whirling stream of burning fuel, air and products of combus' tion is forced to move inwardly and forwardly, and thus abruptly change its direction axially of the chamber, before reaching the gas outlet and without disrupting its whirling movement. Portions of tubes 13 are suitably arranged to form a slag outlet 16 adjacent the lowermost level of furnace 1.

In the operation of primary furnace 1, the fuel and air stream entering through pipe 4 is directed tangentially of the primary burner section 3 so as to impart a whirling motion to the fuel particles while causing them to move in the direction of the outlet 15. The whirling or centrifugal effect is increased by the tangential admission of preheated secondary air through ports 9 and combustion proceeds within the cyclone furnace with the final discharge of combustion gases through the re-entrantthroat passage 15. As the combustible constituents of the fuel particles burn with a high rate of heat release, the temperatures developed Within the cyclone furnace range from 3 about l600 C. to 1800 C. so as to cause the ash constituents of the fuel to become molten and form a liquid slag, some of which adheres to the circumferential walls and forms a complete coverage of the water cooled surface, while the greater portion drains out continuously through the slag outlet 16.

The heating gases generated in the cyclone furnace or furnaces 1, are discharged directly into a secondary furnace or chamber 21 which is formed in the lower portion of a vapor generator, herein only partially disclosed so as to emphasize the more significant features of its construction. As will be understood from the drawing, the vapor generator is formed with upright setting walls which define an interior space of rectangular horizontal cross section, such walls including upright front and rear walls 22 and 23 respectively and opposing side walls 24, 24. of which only one wall 24 is indicated. A reverse arch structure 25 extends forwardly from the rear wall 23 to a point approximately midway between the front and rear walls 22 and 23 so as to divide the vertical height of the interior space into separate intercommunicating chambers, the lower of which is the secondary furnace chamber 21 and the upper of which is a radiation chamber 26 in which a substantial proportion of the heated fluid-conducting elements of the vapor generator are normally contained, such elements being represented in part by wall cooling tubes hereinafter described.

The arch structure 25, in cooperation with the front wall 22, defines a rectangular outlet passage 27 leading into the upper chamber 26, and furthermore includes a forwardly inclined lower arch portion 28 which forms the upper boundary or ceiling of the secondary chamber 21, together with an oppositely inclined upper arch portion 29 which forms the floor of the radiation chamber 26.

The secondary chamber 21 is formed with a floor 31 having front and rear portions, as shown, which are disposed at an elevation below the slag outlet 16 and which converge downwardly at a slight inclination toward a slag discharge opening 32 through which the liquid slag flows out into a water trough 34 or other suitable form of slag disposal equipment.

The enclosing walls of vapor generator chambers 21 and 26 are provided with wall cooling tubes which for each side wall 24, for example, comprise tubes 24:: which extend vertically from a lower side wall header 35. Associated with the front and rear walls of chambers 21 and 26, are separate sets of wall cooling tubes 36 and 37 respectively, of which selected tubes of each set are connected at their lower ends to a lower header 33, and the remaining tubes of each set are connected at their lower ends to a lower header 39. Lower portions of tubes 36 and 37 are arranged in spaced interspersed relationship across the slag discharge opening 32. Suitably, the wall cooling tubes 24a, 36 and 37 are arranged and connected so as to provide a natural circulation of fluid therethrough. For this purpose, it may be assumed that the upper ends of such wall cooling tubes are in communb cation with an elevated steam and water drum, not shown, from which drum suitable downflow connections, not shown, are provided for supplying water to headers 35, 38 and 3?.

From their positions along and adjacent floor 31, the tubes 36 are continued upwardly along the face of the cyclone furnace end Wall 12 Where, as will be understood, portions of tubes 36 are suitably bent in arcuate form to embrace the throat passage 15. From an elevation adjacent the upper margin of wall 12, certain tubes 36 extend rearwardly and upwardly across the gas passage 27 in vertically spaced rows so as to form the lower inclined section of a slag catching grid or screen 41, whereupon the tubes 36 return to a single row arrangement within the upper inclined refractory wall portion 29 of arch 26. The remaining tubes 36, identified as tubes 36a, are extended along the inner face of front wall 22 Above the arch portion 29, the tubes 36am continued in a single row along the inner face of rear wall 23 for direct exposure to the radiation chamber 26.

The tubes 37, from their positions along and adjacent floor 31, are extended toward the rear of chamber 21 where portions of tubes 37 are embedded within an abruptly inclined refractory floor portion 42, and within an upright refractory rear wall portion 43.v Succeeding portions of tubes 37 extend along the outer face of the refractory lower arch portion 28 and are continued at an upward inclination across the gas passage 27, between tubes 36, in spaced interspersed relation therewith, so as to form the-upper inclined section of the slag catching grid 41. As thus arranged, the upper and lower grid sections are separated by a cuneiform space 45 directly adjacent the front wall 22. From their positions in grid 41, the tubes 37 are continued in a single row along the inner face of front wall 22, in interspersed relation with tubes 36a, for direct exposure to the radiation chamber 26.

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

I claim:

1. In a vertically arranged fluid heater furnace having a totally unobstructed lower chamber adapted .to receive the products of combustion in which the combustion of ash-containing solid fuel is substantially completed at temperatures above the ash fluid heated fusion temperature, walls defining said furnace comprising a front upright wall having an opening therein at one elevation for admitting the products of the combustion of ash-containing solid fuel and a separate opening at a lowerelevation for admitting the discharge of molten slag, means defining a floor of said chamber at a level subjacent said slag admission opening, said floor having front and rear portions inclined downwardly toward a slag outlet formed therein adjacent said front wall, a rear upright Wall having an intermediate portion extended forwardly in the form of a reverse arch and defining with said front wall a gas outlet passage from said lower chamber, said walls inclusive of the lower portion of said arch directing said gases within said lower chamber along a horizontally elongated U-shapcd path of which the upper pass terminates in said outlet passage, fluid heating tubes extending along the lower part of the rear wall and thence along the lower side of the arch, and fluid heating wall tubes extending upwardly along said front wall and thence as a screen across said gas outlet passage to said arch and the rear wall.

2. ln a vertically arranged fluid heater furnace having a totally unobstructed lower chamber adapted to receive the products of the combustion of a slag or ash forming fuel at temperatures above the ash fusion temperature, walls defining said fluid heater furnace comprising a front upright wall having an opening therein at one elevation for admitting the products of the combustion of a slag or ash forming fuel and a separate opening at a lower elevation for admitting the discharge of molten slag, a floor forming the bottom wall of said chamber at a level subiacent said slag admission opening, means defining a slag outlet for said chamber in said floor, a rear upright wall having an intermediate portion projecting forwardly in the form of a reverse arch and defining with said front wall a gas outlet passage from .said chamber, said arch having its lower and upper portions inclined upwardly toward said front and rear walls respectively, said walls inclusive of the lower portion of said arch directing said. gases within said chamber along a horizontally elongated U-shapedpath of which the upperpass terminates in said outlet passage, and fluid conducting tubes operatively associated with said front and rear walls and extending at opposite inclinations across said passage in interspersed spaced relation.

References Cited in the file of this patent UNITED STATES PATENTS 1,307,364 Kinyon June 24, 1919 6 Brown Sept. 22, 1925 Clendon Nov. 29, 1927 Caracristi Aug. 13, 1929 Carlson Sept. 16, 1930 Lasker Jan. 23, 1934 Heller Sept. 7, 1937 FOREIGN PATENTS Great Britain Feb. 11, 1948

Claims (1)

1. IN A VERTICALLY ARRANGED FLUID HEATER FURNACE HAVING A TOTALLY UNOBSTRUCTED LOWER CHAMBER ADAPTED TO RECEIVE THE PRODUCTS OF COMBUSTION IN WHICH THE COMBUSTION OF ASH-CONTAINING SOLID FUEL IS SUBSTANTIALLY COMPLETED AT TEMPERATURES ABOVE THE ASH FLUID HEATED FUSION TEMPERATURE, WALLS DEFINING SAID FURNACE COMPRISING A FRONT UPRIGHT WALL HAVING AN OPENING THEREIN AT ONE ELEVATION FOR ADMITTING THE PRODUCTS OF THE COMBUSTION OF ASH-CONTAINING SOLID FUEL AND A SEPARATE OPENING AT A LOWER ELEVATION FOR ADMITTING THE DISCHARGE OF MOLTEN SLAG, MEANS DEFINING A FLOOR OF SAID CHAMBER AT A LEVEL SUBJACENT SAID SLAGE ADMISSION OPENING. SAID FLOOR. HAVING FRONT AND REAR PORTIONS INCLINED DOWNWARDLY TOWARD A SLAG OUTLET FORMED THEREIN ADJACENT SAID FRONT WALL, A REAR UPRIGHT WALL HAVING AN INTERMEDIATE PORTION EXTENDED FORWARDLY IN THE FORM OF A REVERSE ARCH AND DEFINING WITH SAID FRONT WALL A GAS OUTLET PASSAGE FROM SAID LOWER CHAMBER, SAID WALLS INCLUSIVE OF THE LOWER PORTION OF SAID ARCH DIRECTING SAID GASES WITHIN SAID LOWER CHAMBER ALONG A HORIZONTALLY ELONGATED U-SHAPED PATH OF WHICH THE UPPER PASS TERMINATES IN SAID OUTLET PASSAGE, FLUID HEATING TUBES EXTENDING ALONG THE LOWER PART OF THE REAR WALL AND THENCE ALONG THE LOWER SIDE OF THE ARCH, AND FLUID HEATING WALL TUBES EXTENDING UPWARDLY ALONG SAID FRONT WALL AND THENCE AS A SCREEN ACROSS SAID GAS OUTLET PASSAGE TO SAID ARCH AND THE REAR WALL.

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