US2754807A

US2754807A - Waste heat vapor generator

Info

Publication number: US2754807A
Application number: US246802A
Authority: US
Inventors: Charles S Smith
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1951-09-15
Filing date: 1951-09-15
Publication date: 1956-07-17
Anticipated expiration: 1973-07-17
Also published as: GB709329A

Description

July 17, c s s n- WASTE HEAT VAPOR GENERATOR Filed Sept. 15, 1951 3 Sheets-Sheet 1 FIG.1

ATTORNEY C. 5. SMITH WASTE HEAT VAPOR GENERATOR 3 Sheets-Sheet 2 July 17, 1956 Filed Sept. 15, 1961 00 OOOOOPDO O OOOOOOOOOOOOOOOOOOOOOOO INVENTOR CZzar/es S Smz'zfiz ATTORNEY July 17, 1956 c. 5. SMITH 2,754,807

WASTE HEAT VAPOR GENERATOR Filed Sept. 15, 1951 s Shets-$heet' a Z7 0- n I) 774 I 45" i L Fl G. 3

INVENTOR CharZesSSmiilz Y ATTORNEY United States Patent WASTE HEAT VAPOR GENERATOR Charles 'S. Smith, Westfield, N. J., assignor to The A Babcock & Wilcox Company, Rockleigh, N. J., a corporation of New Jersey The present invention relates in general to vapor generators and more particularly to the construction and operation of steam generators of the water tube type arranged for the absorption of heat from waste gases carrying troublesome non-gaseous materials in suspension and furthermore comprising obnoxious gaseous constituents. For the purpose of the present disclosure it may be assumed that the source of such gases is a known type of metallurgical furnace, for example, a smelting furnace of the reverberatory type, as utilized in the smelting of materials bearing copper and other metals. The gases discharged from a copper smelter furnace, for example, are of sufficiently high temperature to make it desirable to recover the heat that might otherwise be lost, suitably by directing the gases through a form of heat exchange apparatus such as a water tube boiler. However, such gases, which are available at temperatures ranging upwardly to about 2270 F., are heavily loaded with sticky slag particles and sulphurous fumes so that their use in the usual form of vapor generator involves severe operating difficulties. of copper bearing materials in a reverberatory furnace, the customary process utilizes natural draft produced by a high chimney to effect withdrawal of the gaseous products from the combined furnace and boiler, and requires the maintenance of a low draft of about 0.05 in. at the outlet of the smelting furnace. Thus, the draft loss through the boiler section must be kept to a reasonably low figure, because of chimney limitations, if the desired subatmospheric pressure conditions are to be maintained in the boiler section. However, in heat recovery apparatus heretofore employed in conjunction with smelting processes, positive pressure conditions have prevailed within portions of the furnace and also within gas passes of the associated waste heat boiler. As a result of such positive pressure conditions, there has heretofore been a substantially continuous discharge of sulphurous fumes from upper portions of the waste heat boiler setting. Furthermore, when lance doors were opened to dislodge slag from the various heat ab- ,sorbing'surfaces, the discharge of fumes was increased to an almost intolerable degree.

In general, therefore, an object of the present invention is to provide a form of waste heat vapor generator wherein positive gas pressure conditions within all gas flow regions are substantially obviated. Moreover, it

is'my purpose to provide a distinctive arrangement of the various heat absorbing elements whereby the accumulation of slag thereon is reduced to a minimum,

and the cleaning of such elements greatly facilitated.

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

abetter understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings Moreover, in the smelting ,and descriptive matter in which I have illustrated and described an embodiment of my invention.

tube bank 25 header 34 through Of the drawings:

Fig. 1 is a sectional side elevation of a vapor generating unit embodying the various features of my invention;

\ Fig. 2 is a sectional plan view of the illustrated vapor generating unit, taken along line 2-2 of Fig. l; and

Fig. 3 is a sectional front elevation of the unit taken along line 33 of Fig. 2.

In more detail, Figs. 1-3 illustrate an embodiment of my invention in the form of a steam generating unit particularly adapted for operation as a waste heat water tube boiler deriving heat from high temperature heating gases which are delivered thereto from an associated copper reverberatory furnace or smelter as hereinbefore described.

The illustrative emboodiment of my invention comprises a fluid cooled setting having upright

lateral walls

10, 10 and 12, and an inclined upper arch wall or roof 13, which define a gas receiving furnace chamber 14, the roof 13 having an intermediate portion 31 of relatively steep inclination, of about 60, whereas other portions have a maximum inclination of about 30. High temperature heating gases, from a copper reverberatory furnace, not shown, are admitted to chamber 14 through a gas inlet passage 15 which is provided by a flue 16 suitably joined to front wall 12. The lower portion of chamber 14 is formed as a hopper having a steeply inclined rear wall 17 directed downwardly and forwardly toward an ash pit 18 having side and end walls provided with cleanout openings and doors 19 as indicated.

A two-drum natural circulation boiler 2t} is positioned at the rear of the setting directly adjacent the dampercontrolled gas outlet flue passage 21. The boiler 20, as illustrated, is arranged for single-pass gas flow therethrough in a generally horizontal direction, and comprises upright boiler tubes arranged in horizontally spaced

banks

23, 24 and 25, and connected at their upper and lower ends to upper and

lower drums

26 and 27 respectively. As seen in Fig. 2, the tubes 23a, 24a and 25a of the respective banks are arranged in rows extending parallel to

drums

26 and 27 and also in other rows extending parallel to the

setting side walls

10, 10. At the rear of the setting, below gas outlet 21, the boiler wall 28 is spaced from the major portion of the rear so as to provide an additional gas flow space 29 leading to the gas outlet 21, alternate tubes 25b having rearwardly offset portions to line and support the wall 28. A dust hopper 30 is provided between the lower drum 27 and the lower end of wall 28.

A continuous multiple loop type superheater 32 is arranged forwardly of the boiler unit 20 with tubes 32a forming interconnected loops which are connected at opposite ends to vapor inlet and

outlet headers

34 and 35 respectively. Tubes 32a are arranged in rows paral lel to side walls It} and, in a transverse direction, in rows parallel to the steam and water drum 26, similar to boiler tubes 23a, 24a, 25a, except at somewhat tubeto-tube spacings. Steam is conducted from drum 26 to steam inlet tubes 36. A hopper 37 having downwardly converging front and rear walls 38 and 39, is positioned below the superheater 32 and the front boiler bank 23, the front wall 38 having its upper end sealed to the upper end of wall 17 at the rear of chamber 14, and the rear wall 39 having its upper end sealed to the lower boiler drum 27.

The side walls 10, forwardly of boiler 20, are fluid cooled throughout by upright tubes 10a and 10b of different lengths which are arranged in single rows along the dicated in Fig. 1. In each side wall 10, the wall cooling tubes a and 1012 are connected at their upper ends to a common upper side wall header 41 disposed at an elevation corresponding to that of the lower half of drum 26. At their lower ends, the longer tubes 10a are connected to a lower side wall header 42, adjacent the bottom of the setting, and the shorter tubes 1%, to a lower side wall header 43 disposed at an elevation corresponding to that of the lower half of drum 27. Water is supplied to each side wall header 42 through

downcomer tubes

46 and 47, and to each side wall header 43 through downcomer tubes 48, all of which

downcomer tubes

46, 47 and 48 have upper inlet ends connected to the lower boiler drum 27. Both upper side Wall headers 41 are suitably connected to the upper boiler drum 26 through riser tubes 49.

The lower inclined furnace wall 17 is lined with cooling tubes 17a having opposite ends connected to lower and

upper headers

51 and 52 which are respectively arranged at substantially the same elevations as the lower

side wall headers

42 and 43. Water is supplied to lower downtake header 51 through the remaining downcomer tubes 47.

The inclined upper furnace wall or roof 13 is lined with wall cooling tubes 13a which have their lower ends connected to a front wall header 54, and their upper ends to upper drum 26, with downcomer tubes 56 forming external water supply connections from drum 26 to header 54.

At the rear of furnace chamber 14, and forwardly spaced from superheater 32, vertically extending

tube platens

57 and 58 are arranged to divide the total horizontal width of available gas flow space into a multiplicity of separate relatively narrow fluid cooled passages 59 through which the incoming slag-laden gases must flow prior to entering the considerably narrower gas lanes provided by the tubes of superheater 32 and of boiler 20. The

platens

57 and 58 are disposed in vertical planes parallel to side walls 10 with the tubes 57a and 58a thereof arranged vertically throughout the height of chamber '14 through which they extend. The platens are also arranged in sets or groups which are horizontally spaced in the direction of gas flow through the furnace.

As seen in Figs. 1 and 3, the majority of platen tubes 57a and 58a are extended downwardly through the inclined rear wall 17 and are connected at their lower ends to horizontal inlet headers 61 which are positioned directly below the respective platens. Platens nearest the side walls 10 include longer tubes 57b and 5817 respectively which are connected at their lower ends to side wall headers 42. In each rearward platen 58, the four rearrnost tubes 58a have lower end portions 580 which are bent toward the rear of the platen and connected to the transverse header 52 at the top of wall 17. Furthermore, in all forward platens 57, the foremost tubes 57a include lower portions 57c which are extended downwardly along the inclined rear furnace wall 17, between groups of wall tubes 17a, and connected at their lower ends to header 51. At the top of furnace 14, the

platen tubes

57a, 58a, and 57b, 58b, are extended vertically to positions above roof 13 where tubes 57a, 5311, are connected at their upper ends to platen headers 62, while the remaining tubes 57b, 58b, in platens nearest the side walls, are connected to the upper side wall headers 41. The lower platen headers 61 are supplied with water through downcomer tubes 63 which have upper inlet connections with the lower boiler drum 27. The upper platen headers 62 are suitably connected to the upper drum 26 through riser tubes 64.

In view of the unusually high slag content of the heating gases, openings may be provided at suitable locations in the enclosing wall structure to permit the insertion of lances or blowers in order to reach surfaces on which slag or dust particles may tend to collect; such openings, as indicated in Fig. 1, including circular openings 65 and 67, for example, for the accommodation of soot blowers for blowing dust from walls and tubes, respectively, andalso vertically elongated rectangular openings or ports 68 and 69 for the insertion of a hand lance or other slag or dust dislodging tool. Openings 69, of

which only one is shown, extend through the steeply inclined arch wall portion 31 and are horizontally spaced in a row across the width of the furnace at locations directly opposite the respective platens 57, thereby affording access to the platens throughout the greater portions of their heights. However, in a boiler unit of the particular arrangement herein disclosed, the deposition of viscous slag occurs mainly in a region preceding the main convection heating surfaces of the unit such as are provided by the boiler 29 and superheater 32. Cooled and solidified slag particles are collected in the hopper bottom of furnace 14, and in

hoppers

37 and 30 beneath the superheater and boiler, this slag being in a form which facilitates handling for remelting in the smelter furnace.

The improvement in operation is attributed to the provision of a completely water cooled furnace structure to which the furnace gases radiate heat whereby the temperature of the gases is rapidly reduced to an extent of about 1000 F., with an accompanying reduction in temperature of entrained slag particles; the provision of a deep furnace hopper formation below the relatively long upwardly inclined flow path of gases traversing the furnace chamber 14; and furthermore, as a significant contributing factor, the provision of multiple gas flow paths between the horizontally spaced, vertical, fluid cooled

tube platens

57 and 58. As a result of the high temperature drop in the furnace, the sticky slag particles are chilled sufficiently to prevent their accumulation on the furnace walls, and the deposition of viscous slag is mainly confined to the leading edges of the platens where it accumulates in wedge-shaped masses which project forwardly to a thickness or depth of about six inches. The front half of this accumulation is soft and plastic While the remaining rear portion is hard and solidly attached to the tubes. As a result of this concentration of slag accumulation, of limited amount, the time and labor required for periodic lance cleaning of the unit has been almost eliminated, in distinct contrast over the extent of such cleaning operations required in waste heat boilers heretofore similarly employed for waste heat recovery in the smelting industry, the soot blowers being adequate for the dislodging of dust which may collect on the walls and tubes. Moreover, with all convection heat absorbing surfaces arranged in a single substantially horizontal gas flow passage and providing straight and parallel gas flow paths through all heat absorbing sections, the draft loss through the entire unit is maintained at a low enough value 'to maintain negative pressures throughout the setting and thereby permit the unit to be operated con tinuously at maximum load without the risk of fumes escaping from within the setting.

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. A waste heat vapor generator comprising, in combination, wall means forming a gas passage arranged for single pass flow of slag laden heating gases therethrough in a generally horizontal direction, upright fluid heating tubes disposed in the gas passage, a chamber at the inlet end of said passage in which said gases are initially received, said chamber having upper and lower walls, means in said chamber forming a multiplicity of unidirectional fluid cooled passages through which said gases are directed prior to contacting said fluid heating tubes, said means comprising horizontally spaced fluid cooled platens arrangedparallel to one another in the direction of flow of said gases and formed of mutually contacting upright tubes aligned in the direction of gas flow and extending through a lower wall of said chamber, and means connected to the lower ends of said platen tubes for directing cooling fluid therethrough.

2. A waste heat vapor generator as defined in claim 1 and further comprising other tubes extending along said lower wall between said platens, said other tubes having lower end portions interspersed with said selected platen tubes and connected in common therewith to said fluid directing means.

3. A low draft loss waste heat vapor generator comprising a setting arranged for single pass flow of slag laden heating gases therethrough in a generally horizontal direction, said setting comprising walls defining a furnace chamber adapted to receive said gases and walls defining a passage through which said gases are conducted from said furnace, one of said walls constituting an upright front wall of said furnace chamber and providing an inletthrough which said gases are horizontally received, other walls forming upper and lower boundaries of said passage and directing said gases along an upwardly inclined path from said chamber, a heat exchanger having upright tubes disposed across said passage and defining a plurality of parallel gas flow lanes through which said gases are directed in a single pass, vertically extending tube platens arranged parallel to the sides of said furnace at intervals across the width of said furnace and terminating at elevations exteriorly of said upper and lower boundaries, said platens forming a plurality of single pass gas flow lanes each of greater width than the gas flow lanes of the heat exchanger, and means connecting said platens and said heat exchanger tubes to form parallel natural circulation flow paths of a common fluid circulating system, said connecting means comprising upper and lower headers to each of which tubes of a plurality of said platens are connected.

4. A waste heat boiler comprising fluid heating tubes disposed in a gas passage arranged for single pass flow of slag laden heating gases therethrough in a generally horizontal direction, a chamber adapted to initially receive said gases and providing the inlet end portion of said passage, means defining the upper and lower boundaries of said chamber and passage comprising an upper and a lower wall each inclined upwardly and rearwardly in said gas flow direction, fluid heating tubes associated with each of said walls and upper and lower headers to which the corresponding ends of said lower wall tubes are connected, said headers extending transversely of said gas flow direction, and horizontally spaced fluid cooled platens arranged between said headers forwardly of said boiler tubes and parallel to one another in the direction of flow of said gases, said platens comprising tubes having lower ends connected to one of said headers.

5. A waste heat boiler as defined in claim 4 wherein said platens are arranged in horizontal succession paralleling the flow of said gases and wherein tubes of the respective platens are separately connected to the respective headers associated with said lower wall.

6. A waste heat vapor generator comprising fluid heating boiler tubes disposed in a gas passage arranged for single pass flow of slag laden heating gases therethrough in a generally horizontal direction, an upper and a lower drum to which said tubes are connected for circulation of fluid therethrough, a chamber arranged forwardly of said tubes and constituting the inlet end portion of said passage, means defining the upper and lower boundaries of said chamber and passage comprising an upper and a lower wall each inclined upwardly and rearwardly in said gas flow direction, upright walls arranged at opposite sides of said chamber and comprising upright fluid heating tubes together with lower side wall headers to which said side wall tubes are connected, horizontally spaced fluid cooled platens arranged forwardly of said boiler tubes in parallel relation to said side walls and comprising vertically extending tubes of which selected 6 tubes are connected to said side wall headers, and means for separately supplying fluid to other tubes of said platens.

7. A waste heat vapor generator comprising fluid heating boiler tubes disposed in a gas passage arranged for single pass flow of slag laden heating gases therethrough in a generally horizontal direction, a chamber arranged forwardly of said tubes and constituting the inlet end portion of said passage, upright walls arranged at opposite sides of said chamber and comprising upright fluid heating tubes together with lower wide wall headers to which said side wall tubes are connected, horizontally spaced fluid cooled platens arranged forwardly of said boiler tubes in parallel relation to said side walls and comprising vertically extending tubes of which selected tubes are connected to said side wall headers, and means for separately supplying fluid to other tubes of said platens.

8. A waste heat vapor generator comprising fluid heating boiler tubes disposed in a gas passage arranged for single pass flow of slag laden heating gases therethrough in a generally horizontal direction, an upper and a lower drum to which said tubes are connected for circulation of fluid therethrough, a chamber arranged forwardly of said tubes and constituting the inlet end portion of said passage, said chamber and passage having an upper and a lower boundary wall each inclined upwardly and rearwardly in said gas flow direction, fluid heating tubes associated with each of said walls and sloping upwardly and rearwardly in conformity therewith horizontally spaced fluid cooled platens arranged forwardly of said boiler tubes and comprising upright tubes having fluid inlet ends and fluid outlet ends arranged exteriorly of said chamber respectively below and above said lower and upper walls, fluid conducting means connecting said lower drum to the lower ends of tubes associated with the lower inclined wall of said chamber, and fluid conducting means separately connecting said lower drum to the fluid inlet ends of tubes of said platens.

9. A waste heat vapor generator as defined in claim 8 and further comprising fluid conducting means separately connecting said upper drum to the lower ends of tubes associated with the upper inclined wall of said chamber and passage.

10. In a single pass gas flow waste heat vapor generator; a roof, side walls and a front wall enclosing a furnace chamber and a following gas passage; the front wall including upright vapor generating tubes and com structed with an opening through which the high temperature waste heat gases are received in the generally horizontal direction; vapor generating tubes included in the roof and the side walls; a bottom for the vapor generator including a plurality of solids receiving hoppers arranged in sequence from the gas inlet to the gas outlet of the unit so that the entire bottom of the unit consists almost wholly of this arrangement of hoppers; a bank of upright fluid heating tubes arranged transversely of gas flow toward the rearward portion of the gas passage, and arranged in a multiplicity of lines generally parallel to the gas flow and forming a multiplicity of unobstructed uni-directional gas flow lanes therebetween; a plurality of platens of upright tubes disposed between the furnace chamber and said bank of fluid heating tubes; the platens being constructed and arranged so that the platens form a plurality of single pass gas flow lanes extending generally in the direction of gas flow, these lanes being much wider transversely of gas flow than the first mentioned single pass gas flow lanes; and means forming a gas outlet for the unit disposed rearwardly, in a gas flow sense, of said bank of fluid heating tubes.

11. In a low draft loss waste heat vapor generator including a setting arranged for single pass flow of particle laden heating gases therethrough in a generally horizontal direction; said setting comprising a roof, a bottom, a front wall and a rear wall defining a furnace 7 .Qharnber and a single pass gas flow passage through which the gases are conducted from the furnace chamber; the front wall of the setting arranged to form an o ening zthrough which the waste heat gases are .generally horizontally received; an upper steam and water ,drum'disposedat the upper part of the unit; a submerged :drum disposed toward the lower portion of the unit; said roof and side walls including vapor generating tubes connected :into a fluid circulation circuit including said drums; a bank of fluid heating tubes directly connecting .said drums and arranged in rows the tubes of which are aligned in the rows in the direction of gas flow so as ito form a multiplicity of single pass unobstructed gas flow ;lanes through the bank of tubes; the bottom of the unit including, and consisting almost whollyof, a plurality of hoppers-having downwardly converging walls for the colzlection of solid particles separated from the gases; one of said inclined hopper walls including vapor generating ,tubesand iacing the oncoming gases as they proceed directly from the gas inlet; means connecting the inclined ,hopper wall tubes into the fluid circulation of the generator; a plurality of upright tubular platens formed by upright and closely arranged tubes disposed transversely of gas flow, the platens being arranged on such wide centers transversely of ,gas flow that they form unobstructed single pass gas flow lanes forwardly of said bank of tubes; the gas flow lanes formed by the platens being much wider than the single pass .gas flow lanes through the .fluid heating tubes; the lower ends of the tubes forming said platens extending through the inclined hopper wall facing the oncoming heating gases and the gas inlet; means for connecting the various upright vapor generating tubes and the platen tubes into the fluid circulation of the unit; ,and means associated with the rear wall of the setting to form a gas outlet for the unit.

References Cited in the file of this patent UNITED STATES PATENTS 1,743,326 Davy Ian. 14, 1930 2,242,762 Shellenberger May 20, 1941 2,268,559 Bailey Jan. 6, 1942 2,336,833 Badenhausen Dec. 14, 1943 2,594,312 Kerr et a1. Apr. 29, 1952

Claims

1. A WASTE HEAT VAPOR GENERATOR COMPRISING, IN COMBINATION, WALL MEANS FORMING A GAS PASSAGE ARRANGED FOR SINGLE PASS FLOW OF SLAG LADEN HEATING GASES THERETHROUGH IN A GENERALLY HORIZONTAL DIRECTTION, UPRIGHT FLUID HEATING TUBES DISPOSED IN THE GAS PASSAGE, A CHAMBER AT THE INLET END OF SAID PASSAGE IN WHICH SAID GASES ARE INITIALLY RECEIVED, SAID CHAMBER HAVING UPPER AND LOWER WALLS, MEANS IN SAID CHAMBER FORMING A MULTIPLICITY OF UNDIRECTIONAL FLUID COOLED PASSAGES THROUGH WHICH SAID GASES ARE DIRECTED PRIOR TO CONTACTING SAID FLUID TUBES, SAID