US2856904A - Method of superheat control in a vapor generator with oppositely vortiginous flame burners - Google Patents

Description

2,856,904 METHOD OF SUPERHEAT CONTROL IN A VAPOR GENERATOR WITH L. W. HELLER Oct. 21, 1958 OPPOSITELY VOR'I'IGINOUS FLAME BURNERS 3 Sheets-Sheet 1 Filed April 25, 1954 FIG.1

ATTO RN EY 1958 w. HELLER METHOD OF SUPERHEAT CONTROL IN A VAPOR GENERATOR WITH Filed April 23, 1954 OPPOSITELY VORTIGINOUS FLAME BURNERS 3 Sheets-Sheet 2 OOOOOOOOOUOOOOOOOOOOOOOOO OOOODOOOOOOO 0000 000000 00 000 FIG.2

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IITIVENTOR Zen 1s WfieZ/er ATTORNEY 2,856,904 METHOD OF SUPERHEAT CONTROL IN A VAPOR GENERATOR WITH Oct. 21, 1958 w. HELLER OPPOSITELY VORTIGINOUS FLAME BURNERS 3 Sheets-Sheet 3 Filed April 23, 1954 ZOEbwm wzrzmmzmw mwimxmmmam 29.8528 522E INVENTOR ,[eW/s Wfi e/ier xPEmzmmmsm mPEmmmEPFE ATTORNEY United States Patent if METHOD OF SUPERHEAT CONTROL IN A VAPOR GENERATOR WITH OPPOSITELY VORTIGI- NOUS FLAME BURNERS Lewis W. Heller, Lower Makefield Township, Bucks County, Pa., assignor to The Babcock &. Wilcox Com pany, New York, N. Y., a corporation of New Jersey Application April 23, 1954, Serial No. 425,137

g 4 Claims. (Cl. 122-478) This invention relates to a fluid heat exchange method and apparatus for carrying out that method. More specifically, the invention relates to a method of and apparatus for effecting the control of heat transfer to the opposite fluid cooled walls of a furnace heated by flame or gaseous products of combustion, in a unit for generating superheated vapor at high temperatures and pressures and maintaining a predetermined high vapor superheat temperature over a wide range of vapor generating rates.

i The invention involves the effective attainment of the above results, by burning ofthe fuel in the combustion zone with the burning fuel projected in oppositely whirling streams of high temperature combustion elements,

with radiant transfer of heat in the combustion zone for,

vapor generation, with the absorption of heat for superheating generated vapor, and with the introduction of recirculated gases from a position beyond the superheating zone to the combustion zone in such relation to the oppositely whirling streams of combustion elements that the eflect of the whirling combustion elements and the recirculated gases are coordinated 'in improved control of the heat input to opposite walls of the furnace. The invention involves such coordination that there may be equalization of gas flow along the opposite walls and thereby equalization of heat transfer to the opposite walls,

In one embodiment of the pertinent method the recirculated gases are introduced into a combustion zone at a position upstream of the fuel burning zone, in a gas flow sense, and the stream of recirculated gases is divided and directed toward opposite heat absorbing and fluent heating tubes of opposite side walls of the combustion zone.

Use of the invention, in some instances, attains concentration of the recirculated gases along opposite furnace walls, and such concentration may be particularly advantageous where the opposite Walls have similar radiant superheater sections with the rates of heat absorption subject to control by flow of recirculated gases over those sections.

Also, the use of the invention with such concentration of gases along opposite furnace walls may be effective in superheat control by the effect upon a division of the total heat absorption between superheater absorbed heat and vapor generating absorbed heat. This division of the total available heat must vary with different loads if a predetermined superheat temperature is to be maintained, and such variation may be promoted by the opposite wall concentration of recirculated gases made possible by the invention.

Where opposite furnace walls involve similar radiant superheater sections the use of the invention promotes equalization of heat transfer to the radiant superheater sections, and such equalization of heat transfer may be further enhanced by the prevention of unequal deposits of solid material upon the opposite walls.

The invention -is clearly set v forth in the claims annexed hereto, but for a complete understanding of the Patented Oct. 21, 1958 ice Fig. 2 is a multiple level plan section as indicated at 22 of Fig. 1, showing a symmetrical arrangement of the horizontally adjacent fuel burners;

Fig. 3 is a vertical section on the line 33 of Fig. 1 showing an arrangement of burners for opposite rotating air introduction.

-Fig. 4 is a diagrammatic sectional elevation of a modified vapor generating and superheating unit having convection and radiant vapor superheaters; and

Fig. 5 is a diagrammatic elevation taken at right angles 1 to Fig. 4.

Figs. 1 and 2 of the drawings illustrate a steam generating and superheating unit including a furnace 10 having front and'rear walls 12 and 14 and opposite side walls 16 and 18, the walls including steam generating tubes adapted, in normal operation, to discharge steam and water mixtures into drum 20. The lower ends of the vapor generating wall tubes have connections with the lower drum 22, such connections including headers 2426, and suitable downcomers leading from the drum 22 to the headers 24--26.

Although the furnace 10 is a hopper bottom furnace having downwardly sloping bottom walls 28 and 30 converging into an ash discharge throat 32, it is to be considered/that the invention may also be quite applicable to furnaces of different bottom construction, such as a flat bottom slag tap furnace.

The drums 20 and 22 are appropriately connected by banks of steam generating tubes and 102, associated with refractory bafiles 104 106 to .provide for the multiple pass gas flow indicated by the arrows'108110.

The drum 20 is provided with appropriate vapor and liquid separating devices so that separated vapor may pass through conduits and 122 to convection superheater 36 which has an intermediate header 124 and outlet header 126.

Some of the heating gases, after passing upwardly through the last gas pass over the bank of tubes 102, pass through the duct or breeching to the regenerative air heater 132 in which the air supplied by the duct 131 is heated to pass through the'ductwork elements 136 and 138 to the burners. After passing through the air heater, the heating gases pass through the ductwork element 134 to a stack or induced draft fan.

The furnace is fired along the wall 12 by groups of oppositely vortiginous flame burners. These groups are indicated in Fig. 3 as A and B. The burners shown are arranged in one horizontal row with the burners 60 and 62 constituting group A and burners 64 and 66 constituting group B. The burners 60 and 62 have their secondary air vanes 68 and 70 so arranged and set as to provide the clockwise turbulence or rotation of the secondary air, as indicated by arrows 72 and 74 in Fig. 3. The burners 64 and 66 have their secondary air vanes 76 and 82 arranged and set as to provide for counter-clockwise rotation of the secondary air and consequent similar rotation of combustion elements within the furnace.

Figs. 1' and 3 indicate the arrangement of burners within a secondary air chamber 90 with fuel being supplied to the separate burners through the separate tubes such as 92. The burners are arrangedto fire horizontally. through the front furnace wall 123 The'y'are designed to burn a fluent fuel preferably pulverized coal which is supplied in an air-borne stream through the pipes 92. Each pipe'92 leads to acentral primary air and coal nozzle 93 3 terminating in the outer part of the'corresponding burner port. Heated secondary air'for combustion is provided under superatrnospheric pressure by conduit 138 leading. to tlie jwindboxor secondary air chamber 90. .Eachthe wind'oox 90 through the vanes to the circular burner ports 105. r

The vanes 68 and 70, 76 and 82rare pivoted at positions where the secondary air is directed into the central, space of each burner in a direction generally tangential, whereby a rotatingair stream about the airborne coal stream from nozzles 93 will discharge through ports 195 into the furnace. Each burner thus delivers a vortiginous secondary air stream embracing the stream of airborne pulverized coal and, with normal operation of burning fuel, the flame and gaseous products of combustion are directed away from the burner ports as vortiginous gaseous streams.

In the Fig. 3 arrangement, the burners 6062 have their respective vanes 68 and 70 so arranged and adjusted that the rotation of the secondary air and the subsequent flame or products of combustion will be in a clockwise direction, as indicated by arrows 72 and 74. The burners 64 and 66 have their vanes 76 and 82 arranged to provide a counter-clockwise air and flame rotation, as indicated by arrows 78 and 82. The action of the burners in this arrangement promotes efficient use of a given quantity of furnace gases and promotes the attainment of equalization and balancing of the heating effects on the opposite furnace walls, and such effects are attained by burners for either coal, gas, oil or any one of the fluent fuels.

Partially cooled heating gases extracted from the flue or ductwork 130 of the unit at 34, downstream of the superheater 36, are directed to the furnace through the ducts 3841 by a fan 37, for the purpose of controlling the heat absorption of the fluid cooled furnace walls. The recirculated gases are introduced into the lower portion of the furnace at an elevation below the row of burners. In the hopper bottom unit shown in Fig. l, the gases pass through duct 41 between the lower spaced ends of the tubes of the hopper wall 30 and then upwardly through the throat 32. As the introduced recirculated gases are at a temperature considerably below the temperature of the newly developed gaseous products of combustion initially issuing from the burners, the recirculated gases are heavier and will therefore spread out over the furnace bottom, the mass of such recirculated gases in the hopper bottom increasing upwardly during the continued delivery of more recirculated gases.

As the flow of recirculated gases is increased there is an increase of the total gas flow over the superheater and the other convection surfaces, such total gas flow including the combustion elements directly or newly issuing from the burners, and the recirculated gases.

When the amount of recirculated gases introduced into the furnace is less than the amount of newly developed gaseous products (or the combustion elements issuing directly from the burner) the former are forced upwardly so that they tend to pass upwardly along the furnace walls at positions where the furnace space is not subject to the high velocity gas flow of the newly developed products of combustion, as, for example, along the opposite side walls 16and 18.

The turbulent'flow of the flame and gaseous products of combustion occurring as a result of the character of secondary air introduction to the burners sets up a furnace gas fl'ow'pattern. which has an. effect upon the upward recirculated gas flow along opposite furnace walls. If all of the burners-have their vanes arranged to give clock wise rotation to the issuing combustion products, an unbalance between the recirculated gas flows upwardly along the inner faces of walls 16 and 18 will occur. This would involve, for example, a retardation or inhibition of the gas flow along the wall 18, and an increase of the gas flow along the wall 16. By having the groups of burners 60, 62, and 64, 66 arranged to deliver secondary air in turbulent streams of opposite rotations, the tendency to unbalance of recirculated gas flow, due to flame rotation, is avoided. Thus, more uniform or equalized I flow of recirculated gases along the opposite walls 16-18 will occur, with a consequent more uniform and effective modification of the heat transfer to those walls.

When the superheater includes opposite radiant wall tube sections, such as 200 in Figs. 4 and 5, receiving steam from the convection superheater 36 the pertinent prevention ofunbalance in furnace side wall heating'has a direct effect upon the final steam temperature and eliminates the necessity for specific provision for steam mixing at the outlets of the radiant superheater sections. It also tends to minimize metal temperatures of the radiant superheater sections to prevent superheater damage.

The wall tube radiant superheater sections of Figs. 4 and 5 are indicated as having connections 208 leading from. the outlet of the convection superheater 36. An atteinperator 210 is included in these connections. In

the modification indicated in Figs. 4 and 5, it is also to be noted that the radiant superheater sections are connected in parallel.

Although the invention has been described with reference to the details of preferred embodiments, it is to be understood that the invention is not to be considered as limited to all of the details thereof. it is rather to be taken as of a scope commensurate with the scope of the subjoined claims.

. What is claimed is:

l. A vapor generating and superheating unit comprising vertical front, rear and opposite side walls arranged to define a vertically elongated furnace chamber of rectangular horizontal cross-section, fluid heating tubes similarly constructed and arranged in said opposite side walls, means defining'a convection heating pass opening to the upper portion of said furnace chamber, a convection vapor superheater in said heating pass, means for withdrawing relatively cool heating gases from said heat ing pass at a point downstream of said superheater and introducing the withdrawn gases into the lower part of said furnace chamber substantially across the entire width of said furnace chamber, and means for firing said furnace chamber comprising a row of horizontally spaced vortiginous circular fluid fuel burners in said front wall at the left and right sides of the center line thereof and arranged to discharge horizontally into said furnace chamber at an elevation above the level of said withdrawn gas introduction, the fuel burners in said row being even in number and each of the left side burners being arranged to discharge a burning fuel stream whirling in one direction and each of the right side burners being arranged todischarge a burning fuel stream whirling in the opposite direction, to equalize the flow of withdrawn gases upwardly along the fluid heating tubes in the opposite side walls of said furnace chamber and thereby reduce the furnace chamber radiant heat absorption and increase the convection superheating effect.

2. A vapor generating and superheating unit comprising vertical front, rear and opposite side walls arranged to define a vertically elongated furnace chamber of rectangular horizontal cross-section, fluid heating tubes similarly constructed and arranged in said opposite side walls, means defining a convection heating pass opening' to the upper portion'of said furnace chamber, a convection vapor superheater in said heating pass, means for withdrawing relatively cool heating gases from said heating pass at a point downstream of said superheater and introducing the withdrawn gases into the lower part of said furnace chamber substantially across the entire width of said furnace chamber, and means for firing said furnace chamber comprising a row of horizontally spaced vortiginous circular fluid fuel burners in said front wall at the left and right sides of the center line thereof and arranged to discharge horizontally into said furnace chamber at an elevation above the level of said withdrawn gas introduction, the fuel burners in said row being even in number and each of the left side burners being arranged to discharge a burning fuel stream whirling in a clockwise direction and each of the right side burners being arranged todischarge a burning fuel stream whirling in a counterclockwise direction, to equalize and expedite the flow of withdrawn gases upwardly along the fluid heating tubes in the opposite side walls of said furnace chamber and thereby reduce the furnace chamber radiant heat absorption and increase the convection superheating effect.

3. A vapor generating and superheating unit comprising vertical front, rear and opposite side walls arranged to define a vertically elongated furnace chamber of rectangular horizontal cross-section having an ash hopper at the lower end thereof with its longitudinal axis arranged parallel to said front wall, vapor generating tubes similarly constructed and arranged in said opposite side walls and hopper, means defining a convection heating pass opening to the upper portion of said furnace chamber, a convection vapor superheater in said heaitng pass, means for withdrawing relatively cool heating gases from said heating pass at a point downstream of said superheater and introducing the withdrawn gases into the lower part of said hopper substantially across the entire width thereof, and means for firing said furnace chamber comprising a row of horizontally spaced vortiginous circular fluid fuel burners in said front wall at the left and right sides of the center line thereof and arranged to discharge horizontally into said furnace chamber at an elevation above the level of said withdrawn gas introduction, the fuel burners in said row being even in number and each of the left side burners being arranged to discharge a burning fuel stream whirling in a clockwise direction and each of the right side burners being arranged to discharge a burning fuel stream whirling in a counterclockwise direction, to equalize and expedite the flow of withdrawn gases upwardly along the fluid heating tubes in the opposite side walls of said furnace chamber and thereby reduce the furnace chamber radiant heat absorption and increase the convection superheating effect.

4. A vapor generating and superheating unit comprising vertical front, rear and opposite side walls arranged to define a vertically elongated furnace chamber of rectangular horizontal cross-section, a pair of radiantly heated vapor superheating tube sections similarly constructed and arrangedv in said opposite side walls, means defining a convection heating pass opening to the upper portion of said furnace chamber, a'convection vapor superheater in said heating pass, means for connecting said convection vapor superheater to said radiantly heated vapor superheating tube sections for parallel flow of vapor therethrough, and means for firing said furnace chamber comprising a row of horizontally spaced vortiginous circular fluid fuel burners in said front wall at the left and right sides of the center line thereof and arranged to discharge horizontally into said furnace chamber at the elevation of said radiantly heated vapor superheating tube sections, the fuel burners in said row being even in number and each of the left side burners being arranged to discharge a burning fuel stream whirling in a clockwise direction and each of' the right side burners being arranged to discharge a burning fuel stream whirling in a counter clockwise direction, to equalize the flow of gases upwardly along the opposite side walls of said furnace chamber.

References Cited in the file of this patent UNITED STATES PATENTS 1,943,286. Burg Ian. 16, 1934 2,087,972 Keller July 27, 1937 2,213,185 Armacost Sept. 3, 1940 2,229,643 DeBaufre Jan. 28, 1941 FOREIGN PATENTS 503,778 Belgium June 30, 1951 371,985 Italy June 12, 1939

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