US2897795A

US2897795A - Plural furnace single drum steam generating unit

Info

Publication number: US2897795A
Application number: US542314A
Authority: US
Inventors: Will H Rowand
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1955-10-24
Filing date: 1955-10-24
Publication date: 1959-08-04
Anticipated expiration: 1976-08-04

Description

Aug. 4, 1959 w. H. ROWAND PLURAL FURNACE SINGLE DRUM STEAM GENERATING UNIT Filed Oct. 24, 1955 5 Sheets-Sheet l E i \i INVENTOR.

Wi H H. Rowand ATTORNEY Aug. 4, 1959 PLURAL FURNACE SINGLE DRUM-STEAM GENERATING UNIT Filed Oct. 24, 1955 W. H. ROWAND To TURBINE 5 Sheets-Sheet 2 FIG? INVENTOR.

y Rowand WATTORNEY Aug. 4, 1959 PLURAL FURNACE SINGLE DRUM STEAM GENERATING UNIT Filed Oct. 24, 1955 w. H. ROWAND 2,897,795

5 Shegts-Sheet 3 (II-.2) CT:

ram

GTIID L11:

' m EID (III!) INVENTOR.

BY Will H. Rowand .ATTORNEY Aug. 4, 1959 W. H. ROWAND Filed Oct. 24, 1955 5 Sheets-Sheet 5 3 1s ECONOMIZER J 302 -314 v FEEDWATER L4; 1 I 36 28 I IL IL I i I I'\ l i i I l I l l 1s 21 19 I 20 1 l I l A 1 I l 10 1x i I I I I i i l L4o 86 104 08 :1a4 136 m 1 201 AAAAAAA m. h INVENTOR.

Will H. Rowand BY United States Patent P Will H. Rowand, Short Hills, NJ., assignor to The Babc'ock & Wilcox Company, New York, N.Y., a corporation of New Jersey Application October 24, 1955, Serial No. 542,314

Claims. (Cl. 122-406) This invention relates to high capacity steam generating units of the water tube type particularly enhancing the efficiency of an electric power generating station of which the unit is a The invention is exemplified in a steam generating installation having a steam reheating unit and a steamsuperheating unit enclosed in casings spaced apart longitudinally of a single steam and water drum which forms a part of the fluid circulating system of each unit. Each unit has its own separately fired furnace the Walls of which include steam generating tubes receiving heat from the furnace gases and discharging steam and water mixtures which pass to the steam and water drum. A first unit includes a gas heated steam heater which is at least predominantly a steam superheater from which high pressure and high temperature steam passes to the high pressure stage of a steam turbine. A second unit includes gas heated steam heating means which is at least predominantly-a steam reheater normally receiving lower pressure exhaust steam from a steam turbine stage, and heating that exhaust steam to a predetermined tempera- ,ture for delivery to a low pressure or intermediate turbine stage. The different units include separately controlled gas temperature and gas flow controlling means for attaining such diiferent gas temperature and/or flow conditions that the superheated steam and the reheated steam are maintained at a predetermined temperature or temperatures throughout a wide range of steam generation. Separately fired fuel burning means vary the steam generation rates in the and the heating gas controlling means include gas recirculating means extracting heating gases from one or more of the units downstream (in a gas flow sense) of its steam heating means and introducing the withdrawn gases into one or more furnaces of the units. Regulation of such gas recirculation attains such dilferential control of steam superheat and reheat temperatures that those temperatures are maintained :at a predetermined value, or values. In one example of the invention one steam generating unit has its own separate gas recirculation system controlled so as to maintain a predetermined superheat temperature,

and a second unit has its own gas recirculation system for maintaining a predetermined reheat temperature. These systems may be automatically controlled from a plurality of pertinent operative variables such as representations of changes in rate of steam generation and representations of final superheat and/or reheat temperature.

One of the units may be termed a superheater unit and another unit may be termed a reheat unit, the units having interconnected water circulation systems on account of which interconnection differential firing or differential gas control may be advantageously effected to .atttain optimum reheat and superheat temperature controls without consideration of differential furnace gas pressures which may result from such difierential control.

The interconnection ofthe water circulation systems for the units is such that optimum concentration conditions are promoted and minimum flow of water longitudinally of the drum to the downcomers is attained along with uniform temperature and adequate flow of water to the steam generating tubes of the different units. Such inter-connection involves, in one instance, a plurality of large diameter downcomers leading from distributed positions along the length of the drum with each downcomer having an upper branch leading from a different position longitudinally of the drum and having a lower branch leading to a different group of furnace wall steam generating tubes.

The invention is set forth in concise terms in the appended claims, but for a complete understanding of the invention, its uses and advantages, recourse should be had to the following description which refer to the accompanying drawings in which a preferred embodiment of the invention illustrated. 4

In the drawings:

Fig. 1 is a view in the nature of a perspective view of the arrangement of elements of the invention, indicating in dotted lines, the outlines of the plurality of steam generating units associated with the single steam and water drum;

Fig. 2 is a diagrammatic view in the nature of a vertical section showing the general arrangement of the components of one of the steam generating of Fig. 1;

Fig. 3 is a view in the nature of a plan, or horizontal section showing the separated steam generating units and their relations to the single steam and water drum;

Fig. 4 is a schematic plan of the riser and drum connections for the difierent units; and

Fig. 5 is a schematic front view of the drum with its associated downcomers, gauge glasses, and feedwater control system.

In the drawings, Figure 1 shows in dot and dash lines the two high capacity and high pressure

steam generating units

10 and 12. These units are separately encased or enclosed as indicated in Figure 3 and they are spaced apart lengthwise of the steam and Water drum 14 which extends past, or across, both steam generating units.

The steam generating tubes of each of the

units

10 and 12 discharge steam and water mixtures into the drum 12 where the steam is separated firom the water, prerferably by rows of whirl chamber type separators of the type indicated in the United States patent to Fletcher and Rowand 2,289,970. The separated steam passes from the drum 14 to a high pressure steam turbine of a power plant or to another point of use. The separated water passes downwardly firom the water space of the drum through downcomer means herein shown as the large diameter downcomers 18-21. These downcomers lead from positions distributed along the length of the drum as indicated in Figure 1, thereby minimizing the path of travel of water longitudinally of the drum. This result is therefore promoted and enhanced, and, simultaneously, the circulatory flow from the drum through downcomers is equalized or made more uniform by the arrangement of upper downcomer branches shown in Figure 1. For example, the downcomer 18 has a branch '24 (shown in dash lines) extending from a position along. the downcomer 18 and below the drum 14 to the position indicated at 26 wherein it communicates with the water space of the drum Eat a point adjacent the steam gen-- erating unit 12 and remote from the connection of the downcomer 18 to the drum 14.

Likewise the downcomer 20 has an upper branch 28 leading to the left hand end of the drum at a position indicated at 30 in Figure l. The upper branch 32 of the downcomer 21 leads to connection with the drum at the position 34 remote from the position at which the down-- comer 21 is connected to the drum. Similarly, also, the downcomer 19 has an upper branch 36, communicating with the downcomer 19 at one end and communicatingflat. itsother end with the right hand end of the drum at the position 38. I

The above indicated arrangement of the downcomers with their branches not only minimizes the flow of water lengthwise of the drum and-promotes equalization of water flow from the drum, but it also has an equalizing effect upon the fluid circulations of the composite steam generating units and 12 whereby they are tied together in 'a single circulatory system. 'l he downcomer 18 has a branch lower 40 from which water may flow through one or more conduits 42 to the header'44 from which a row of steam generating Wall tubes 46 (see Fig. 2) lead npwardly toward the steam and watermixture receiving chamber 48 of the drum 14. Some of these tubes lead through the tubular sections 50-52 of the arch 54 extending inwardly of the combustion chamber 56 of the steam generating unit 10. Beyond the tubular sections of the arch the flow continues through the screen tubes 70, the roof tubes 72, the header 74 and the circulators 76 to the drum chamber 48. The fiowof fluid from the remainder of the steam generating tubes leading from the header 44 is upwardly through the header 60, the screen tubes 62, the header 64, and the circulators 66 to the mixture chamber 48.

Part of the lower downcomer branch 40 may serve as a side wall header from which a row of steam generating tubes 80 of a side wall of the steam generating unit 10 may lead up'wardly to the upper side wall header 82 from which steam and water may flow to the drum 14 through one or more appropriate circulators 84 (see Fig. 1.).

From the lower end of the downcomer 18 another branch 86 extends beneath the steam generating unit 10 and the flow of water continues from the downcomer 18 through .the branch 86 and then through one or more conduits such as 88 to the side wall header 90 of the steam generating unit 10. Simultaneously a part of the water flowing through the branch 86 passes through one or more conduits 91 to the header 92 from which (as indicated in Fig. 2) the water flows through the furnace floor tube section 94 and then through the front Wall tubular sections 96 to a header 98, and thence through the circulators 100 to the mixture chamber 48 of the drum 14. t

The downcomer 19 has a branch 104 through which water flows to the header 92 through one or more conduits 106.

A second branch 108 leads from the lower end of the downcomer 19 beneath the steam generating unit 10 where it has one or more conduits 110 leading to the header 44.

A similar arrangement of lower branches is provided for the

downcomers

20 and 21 on the side of the installation adjacent the steam generating unit 12. In this arrangement the downcomer 21 has two

lower branches

120 and 122, with the latter having at least a part of its flow continuing to the header 124 through one or more conduits 126. A part of the flow through the branch 120 continues through one or more conduits 128 to a side wall header 130 at the far side of the steam generating unit 12, providing for the flow of water to the lower end of the side wall steam generating tubes similar to the tubes indicated at 80 in Fig. 2. The remainder of flow through branch 120 continues through one or more conduits 132 to the header 124.

The downcomer 20 has the

lower branches

134 and 136. The former may have conduits connecting it to a furnace side wall header 138 and other conduits 140 leading to the rear wall header 142 for the steam generating unit 12.

The branch 1 36 of the downcomer 20 has one or more conduits 144 leading from that branch to the header 142. With the above indicated arrangement of components the provision of a plurality of circulators (such as 66 and 84) leading from each upper furnace wall header of each unit to the drum, with some of the circulators from each upper header leading to one portion of the drum adjacent one unit, and the remainder of the circulators from the. same header leading to the drum at a position adjacent the other unit. Fig. 1 shows

circulators

66 and 66 as leading from the same upper walltube header 64 to widely spaced positions lengthwise of the drum, the circulator 66' leading from the unit 10 to a position in the drum adjacent unit 12. The pertinent arrangement of circulators leading from the upper furnace wall headers of the different units to ditferent positions in the drum is schematically illustrated in Fig. 4, to a greater extent. In this figure the side wall header 250 for the unit 12 has one or more circulators or circulatory conduits, such as 252 leading from that header to positions along the drum adjacent the unit 12, such as the position 256. Other circulators, such as 254, lead from the header 250 to drum positions toward the opposite end of the drum adjacent the unit 10, one of such positions being indicated by the numeral 258. Likewise the other side wall header 260 at the upper part of the unit 12 has one or more circulators 266 leading from that header to positions such as the position 268 along the drum 14. This header 260 has other circulators, such as 262, leading to the drum at positions such as 264, adjacent the unit 10.

Similarly, the rear wall header 270 at the upper part of the unit 12 has one or more circulators such as 272 connecting the header to positions in the drum adjacent the unit '12, such positions being exemplified by the position 274. One or more other circulators, such as 276, leading from the header 270, lead to positions toward the opposite end of the drum and adjacent the unit 10, such positions being exemplified at 278. Similarly, one or more circulators 282 lead from the header 280 at a position adjacent the unit 12 to a position of connection, 284 with the drum 14, adjacent the unit 12. One or more other circulators such as 286 lead from the header 280 adjacent the unit 12 to drum positions, such as 288, adjacent the unit 10 and toward the opposite end of the drum. 7

The header 290 also has one or more circulators such as 292 leading from a position along the header 290 adjacent the unit 12 to drum positions adjacent that same unit, such a position being indicated at 294. Centrally disposed circulators 295-298 connect the mid portions of the

headers

280 and 290 with the mid portion of the drum 14.

From the description relating to Fig. 4, it is to be understood that an arrangement of headers and circulators similar to that above described, is related in a similar manner to the unit 10. This arrangement of flow circuits from the risers of the units to the drum may be referred to as cross-over connections between the risers of the different units and adjacent sections of the drum.

The above described arrangement of downcomers with their upper branches connected to the drum 14 is also indicated in Fig. 5 of the drawing. This figure also discloses a gauge glass 300 disposed mid-way the length of the drum and operatively connected with a feedwater regulating valve 302. i

The operative connections between the gauge glass 300 and the feedwater regulating valve 302 are represented by a low water level line 304, and a high water level line 306 leading to a control unit 308, which has one or more appropriate control lines, such as 310, openatively connected to the control component 312 for the feedwater regulating valve 302. This system operates in a well known manner to open the valve 302 to increase the flow of feedwater to the drum 14, when the water level as indicated by the gauge glass 300 is below an optimum level. The valve 302 may-be closed when a predetermined high water level is indicated by the gauge glass 300.

The feedwater flow through the valve 302 continues through the line 314 through the economizer 316, and then through the line 318 to the drum 14.

Referring now to the steam generating units it will be understood that they are similar in construction to that indicated in Fig. 2. Each unit has a casing, or enclosure including a front Wall 150, a rear wall 152 and side walls 154 and 156 (Fig. 3). Fig. 2 also indicates the casing as having the lower parts 160-163 enclosing the vvindbox 166 for the burners 168-170, and a part of the duct' work leading to the windbox from an appropriate air heater. The casing also includes upper parts 172-175 co-actingwith side wall casing sections to form the roof of the unit and to enclose the drum 14 and the circulating connections at the top of the unit.

Although the two generating units are similar in construction they difier in thatthe .steam heating components of the unitare superheating components Whereas the similar steam heating components of the unit 12 are predominantly reheater units. Fig. 2, is a vertical section through the fig. 710. unit wherein the heating gases pass from the combustion chamber 56 over and between the platens 180 of the secondary or high temperature superheater 182, each of these platens being formed by U tubes leading from the inlet header 184 to the outlet header 186. The gases then pass over the return bend series connected tubes of the other secondary superheater section 188. Thence the gases. pass between the screen

tubular sections

70 and 62"and across the horizontally spaced upright tubes 190 constituting a part of the primary superheater. Beyond these tubes the gases pass downwardly through the downflow gas pass 192 between the rear wall. 152' and the combustion chamber wall along the steam generating tubes 46. In this downward flow the gases pass over the banks of tube 194496 leading from the header 198 and constituting another part of the primary superheater. The gas flow then continues ,across the banks,v of

tubes

200 and 202 of the economizer. The gases turn in hopper 204 at the bottom of the down flow gas pass and continue through the flue 206 to a stack, with part of the gases being withdrawn by the recirculating gas fan 208 through the inlet duct 210 and discharged along the floor 212 of the combustion chamber 56 through the recirculated gas outlet ductwork 214 which is in communication with outlet of the fan 208 through the duct 216.

Steam separated from the mixtures entering the drum 14 pass from the steam space of the drum through one or more superheater supply tubes 220 to the header 222 from which a row of tubes lead downwardly and form the gas pass roof tube sections 224 and the gas pass rear Wall sections 226. The steam flow continues to the header 228 at the bottom of the gas pass and thence through appropriate conduits 230 to the primary superheater inlet header 198. From that header the steam passes through the banks of

tubes

196, 195, and 194 and thence through the upright tubular sections 232 and their connected tubular sections 234 to the inlets of the bank of tubes 190. From these latter tubes the steam flow continues through header 236 and thence through one or more conduits 238 to the inlet header 184 of the secondary superheater section 182. From this section the steam flow continues through the header 186 and one or more conduits 244 to the inlet header 242 of the secondary superheater section 188. From the outlet header 240 of this section the superheated steam passes to a point of use, for example the inlet of a steam turbine.

Thelstearn generating unit 12 has a primary superheater-section similarto that of the number 10 unit, but its, banks of tubes 188 and 182' (Fig. 3), although similar in construction ,to the

secondary superheater sections

188 and 182 of the fig. 10 unit, constitute a reheater, with its inlet receiving exhaust steam from one turbine stage and .its outlet connected to the inlet of a lower pressure turbine stage.-

Likewise the platens of the fig. 12 unit are similar to the platens 180 of the secondary superheater of the fig. 10 unit, but these platens 180 of the number 12'unit constitute part of a reheater. Each platen may be in series 'With a reheater section 188' or alternatively, the platens 180' may constitute a separate reheater so that thelnumber 12 unit has two reheaters associated therewith. Although the invention has been described with reference to the details of the construction of the preferred embodimentit is to be understood that the invention is not limited to all of the details of that embodiment. The invention is, rather, to be considered as of a scope commensur'ate with the claims.

What. is claimed is: l

1. In a steam generating installation, a steam and water drum, first and second steam generating units spaced apart lengthwise of the drum and adjacent thereto,,each of said units extending along approximately one-half the length of said drum, a furnace for each unit, each furnace having steam generating furnace wall tubes from which steam and water mixtures normally flow to the drum, separate fuel burning means for the furnace of each unit, steam heating means in said units, water circulation means connecting the water space ofthe drum and the inlets of the steam generating means, means including a feedwater regulating valve providing for the flowvof feedwater to the drum, a gauge glass disposed at a position approximately one-half the length of said drum and between said units, and means initially influenced by the liquid level in the gauge glass for controlling the feedwater flow.

2.- In a steam generating installation, a steam and wa ter drum, first and second steam generating units having separate enclosing casings spaced apart lengthwise of the drum and adjacent thereto, each of said units extending along approximately one-half the length of said drum, a furnace for each unit, each furnace having steam generating wall tubes from which steam and water mixtures normally flow to the drum, separate fuel buming means for each unit, steam heating means in said units, water circulation means including downcomers cross-connecting the water spaces at opposite end portions of the drum and the inlets of the steam generating tubes of the difierent units, cross connected circulatory means connecting the outlets of the steam generating tubes of each unit to a part of the drum remote from that unit and adjacent the other unit, means providing for the flow of feedwater to the drum, a gauge glass connected to the water and steam spaces of the drum at a position approximately one-half the length of said drum and between said units, and means initially influenced by the liquid level in the gauge glass for regulating the feedwater flow.

3. A vapor generating plant comprising a pair of vapor generating units, each of said units having walls defining a vertically elongated furnace chamber, a row of vertically arranged vapor generating tubes lining a wall of said furnace chamber, a horizontally arranged lower header connected to the lower ends of said generating tubes, a horizontally arranged upper header connected to the upper ends of said generating tubes, and means for independently firing said furnace chamber, an elevated horizontally arranged liquid and vapor separating drum extending continuously along the upper ends of both of said vapor generating units parallel to the plane of said vapor generating tubes and substantially coextensive with the distance between the outer side walls of said vapor generating-units, jand means'for maintaining a fluid circulation betweenthe vapor generating tubes of bothof said vapor generating units and said separatingdrum comprising downcomer' pipes arranged to connect each of said lower headers at laterally spaced points to corresponding portions in one-' half length of said elevated separating drum, abranch pipe connecting each of said downcomer pipes at a point above the level of the corresponding lower headto a portion of said separating drum remote from said first connection and in the remaining half-length of'the drum receiving the downcomer pipes connected to said other vapor generating unit lower header, whereby liquid from longitudinally spaced portions of said'separating' drum is separately collected in each downcomer pipe' and circulator tubes connecting each of said upper headers to said elevated separating drum. 7 1 a 4. A vapor generating plant comprising a pair oi vapor generating units, each of said units having walls defining a vertically elongated furnace chamber, a row of vertically arranged vapor generating tubes lining a wall of said furnace chamber, a horizontally arranged lower header connected to the lower ends or said generating tubes, a horizontally arranged upperheadercon nected to the upper ends of said generating tubes, and means for independently firing 'saidfu'rnace chamber, an elevated horizontally arranged liquid and vapor separating drum extending continuously "along the upper ends of both of said vapor generating units parallel to the plane of said vapor generating tubes and substantially coextensive with the distance between the outer side walls of said vapor generating units, and means for maintaining a fluid circulation between the vapor generating tubes of both of said vapor generating units and said separating drum comprising downcomer pipes arranged to connect said lower headers at laterally spaced points to corresponding portions of said elevated sep arating drum, and a circulator tube connecting each of said upper headers to a corresponding portion in onehalf length of said elevated separating drum, and an additional circulator tube connecting each of said upper headers to a portion of said separating drum'remote from said first connection and in the remaining half-length of the drum receiving a circulator tube connected to said other vapor generating unit upper header.

5. A vapor generating plant comprising a pair of vapor generating unitsyea'ch of said units. having ,walls defining a vertically elongated furnace chamber, a row of vertically'arranged vapor generating itubes'lining a wall of said' furnac'e'chamber, a horizontally arranged lower header connected to the lower ends of 'said generating tubes, a'horizontally arranged upper header connected to the upper'ends of saidgenerating tubes, and means for independently firing said furnace chamber, an elevated horizontally arranged liquid and vapor separating drum extending continuously along the upper ends of both of said vapor generating units parallel to the plane of said vapor generating tubes and substantially coextensive with the distance between the outer side walls of said vapor generating units, and means for maintaining a fluid circulation between 'the vapor generating tubes of both of said vapor generating units and said separating drum comprising downcomer pipes arranged to connect said lower headers 'at laterally spaced points to corresponding portions of said elevated separating drum, a branch pipe connecting each of said downcomer pipes at a point above the level of the corresponding lower header to a portion of said separating drum remote from said first connection and adjacent to the downcomer pipes connected to said other vapor generating unit lower header, whereby liquid from longitudinally spaced portions of said separating drum is separately collected in each downcomer pipe, and a circulator tube connecting each of said upper headers to a corresponding portion in one-half length of said elevated separating drum, and an additional circulator tube connecting each of said upper headers to a portion of said separating drum remote from said first connection and in the remaining half-length of the drum receiving a circulator tube connected to said other vapor generating unit upper header.

References Cited in the file of this patent I UNITED STATES PATENTS 2,285,442 Kerr June 9, 1942 2,302,931 Arnold Nov. 24, 1942 2,325,384 Emmet July 27, 1943 2,781,028 Armacost Feb, 12, 1957 2,781,746 Armacost et al, Feb. 19, 1957 FOREIGN PATENTS 1,045,900 France July 1, 1953