US2836156A - Tubular vapor generating and vapor superheating units - Google Patents

Description

May 27, 1958 w. F. c. scHAAP TUBULAR VAPOR GENERATING AND VAPOR SUPEBHEATING UNITS 5 Sheets-Sheet 1 Filed Dec. 18.. 1953 4 0 a0 ar a;

*m mm mw mm ATTORNEY y 7, 1958 w. F. c. SCHAAP 2,836,156

TUBULAR VAPOR GENERATING AND VAPOR SUPERHEATING UNITS Filed Dec. 18. 1953 5 Sheets-Sheet 2 F|G. @07 n95 f ATTORNEY May 27, 1958 w. F. c. SCHAAP TUBULAR VAPOR GENERATING AND VAPOR SUPERHEATINGUNITS Filed Dec. 18. 1953 5 Sheets-Sheet 3 /Z4 0 7375 737d 67C FIG.3 NM

FIG.5

ATTORNEY May 27, 1958 w. F. c. SCHAAP TUBULAR VAPOR GENERATING AND VAPOR SUPERHEATING UNITS 5 Sheets-Sheet 4 Filed Dec. 18. 1953 FIG.6

INVENTOR v WILLEM F.C.SCHAAP FIG? ATTORNEY May 27, 1958 w. F. c. SCHAAP 2,836,155

TUBULAR VAPOR GENERATING AND VAPOR SUPERHEATING UNITS Filed Dec. 18. 1953 5 Sheets-Sheet 5 INVENTOR WILLEM CHAAP ATTORN EY nited TUBULAR VAPGR GENERATING AND VAPOR SUPERHEATWG UNET Application December 18, 1953 erial No. 399,115

6 Claims. (Ci. 222-33 2) This invention relates to tubular vapor generating and vapor heating units of the kind comprising a furnace chamber with vapor generating wall tubes and with an outlet for the passage of gases from an upper region of the chamber to a lateral gas pass followed by a downpass, the lateral gas pass containing upright vapor heating tubes and the downpass containing vapor heating tubes extending across the pass. In a unit of this kind deposits falling from the upright tubes may be collected by a hopper or hoppers for discharge to the furnace chamber, so that disposal of deposits dislodged from the tubes is facilitated. In the downpass, however, deposits removed from an upper row of tubes or from an upper tube bank may find lodgement on a lower row of tubes or on the tubes of a lower tube bank within the pass. Such difficulty is aggravated if, as may be the case, the horizontal tube pitch in a lower tube bank is less than that in an upper tube banlc. It is a matter of importance, therefore, to void if possible under all conditions of operation the formation on tubes in the downpass of deposits which when removed form lumps of appreciable size and to this end the deposit forming ma-- terial contained in the furnace gases should be adequately cooled before reaching the downpass. The difiiculty of obtaining adequate cooling is accentuated in vapor generating and vapor heating units for providing high pressure and high temperature vapor, since the extent of the vapor heating surfaces in such units tends to become excessive unless a relatively high gas ten erature at the inlet to the vapor heating surface prevails An object of the invention is the provision of an improved form of unit for the production of vapor at high temperature and pressure and having an arrangement of vapor heating surfaces economical to install and favorable to the maintenance of the vapor heating surfaces in good condition for effecting heat exchange.

In a tubular vapor generating and vapor heating unit of the kind specified the lateral pass extends above and contains vapor heating tubes disposed above the downpass, whilst means are provided for effecting interception of at least the larger pieces of solid matter which fall in the lateral pass towards the downpass.

The invention will now be described, by way of example, with reference to the accompanying partly diagrammatic drawings, in which:

Figure l is a sectional side elevation through a steam generating and superheating unit, taken on the line 171 of Figure 3 and as viewed in the direction indicated by the arrows;

Figure 2 is a sectional side elevation of part only of the unit shown in Figure 1, taken on the line H.II of Figure 3;

Figure 3 is a sectional plan view taken on the line III-III of Figure 1;

Figure 4 is a sectional plan view taken on the line IV-IV of Figure 1;

Figure 5 is a fragmentary sectional plan view of a gas atent v n a r 3.0

i Patented Mag 2?, 15553 pass boundary, as shown in Figure 4, but drawn to a larger scale;

Figure 6 is a sectional plan view taken on the line VIVI of Figure 1;

Figure 7 is a sectional plan view taken on the line VII-VII of Figure 1;

Figure 8 is a sectional front elevation taken on the line VIII-Vill of Figure 7; and

Figures 9 and 10 are sectional side elevations of a modified construction and correspond to the upper right hand parts of Figures 1 and 2 respectively.

A verticall elongated furnace chamber 1 of rectangular cross-section is formed with a hopper bottom 2 and has its front wall 3, rear wall 4 and side walls 5 and 6 lined with contiguous or closely spaced, steam generating, wall cooling tubes. Thus tubes it connected at their lower ends to an inlet header 11 line the front wall of the hopper bottom 2, and thence extend vertically upwards to approximately the mid-height of the furnace chamber, where they are bent inwardly to form an arch 12, above which they return to the plane or" the lower part of the front wall and continue vertically upwards to the roof 13 of the furnace chamber, through which they extend, the tubes being connected at their upper ends to a steam and water drum 14. Tubes 17 connected at their lower ends to an inlet header 18 line the rear wall of the hopper bottom 2 and thence extend vertically upwards to a level above that of the arch 12, and below that of a lateral gas outlet 19 from the furnace chamber, at which level alternate tubes, designated by Hal, are bent forwardly towards the wall 3 to form an arch 2% which extends across the full width of the furnace chamber and which extends approximately a quarter of the depth of the furnace towards the front wall. The remainder of the tubes 17, designated by 17 b, extend vertically upwards as far as the roof 13, at which they are bent forwardly of the furnace chamber and extend towards and through the front wall 3, serving to line the roof 13, and are connected at their upper ends to the steam and water drum 14. Above the arch 20, alternate tubes designated 1711a of the tubes 17:! extend vertically upward to the roof 13, while the remainder of the tubes 17a, designated 17ab, are inclined rearwardly and upwardly to define an upper surface of the arch 2i and to rejoin the tubes 17b beyond which point they extend vertically as two parallel rows of spaced tubes to the roof 13. The tubes a and 17:11:, like the tubes 17b, extend towards and through the front wall 3, serve to line roof l3, and are connected at their upper ends to the steam and water drum 14. The inlet headers 11 and 13 are connected by suitable downcomers, indicated at as, to the drum 14. i

The side walls 5 and 6 are lined in well known manner with closely spaced steam generating tubes 29 (see Figure 3) connected at their lower and upper ends respectively to inlet and outlet headers (not detailed), and suitably connected by downcomers and uprisers to the steam and water drum 14.

Fuel burners 41 are arranged to discharge pulverized fuel and secondary air into the furnace chamber between the tubes which line the lower part of the front wall 3 below the arch l2.

Arranged adjacent the front wall 3 in the alcove 45 above the arch "12 is a radiant superheater 47 comprising hairpin shaped tubes 48 arranged in groups to form tube platens or panels 4? and with their return bends uppermost and extending through the roof 13 of the furnace chamber, the lower ends of each tube being connected respectively to an inlet headerStl and to an outlet header 51. The inlet header 50 is connected to the steam space of the drum 14 by tubes 52 disposed inside the alcove .45 and positioned on the wall side of the platens 49.

half the depth of the downpass 61*.

A lateral gas pass 6il'exte'nds rearwardly from the gas assages outlet 19 and communicates at its rearward end with a wall 4 is, in the form' of a hopper and compriseslitwo wthree parallel-connected gas flow paths extending respectively from a' location above the by-pass 67 to three lateral gas outlets 74a, 74b and 740 arranged at the lower end ofthedownpassrear wall 75. The 'downpass is thus divided into three parts; 61a, 61b and 610 respectively lying between side Wall 77 of downpass 61a and the partitionwall 72, between the partition walls 72and 73,

and between the partition wall 73 and side wall '78 of the downpa'ss 61a Adjustable deflector plates 79a, 79b and 719c'are secured to the wall '75 above the level of the opening 66, the, plates extending across the widths of the "parts 61a," 61b and 61c of the gas pass 61 respectively and each'having an inwardly and downwardly sloping upper surface. A partition wall 82 which serves as the front wall'of the downpass 61 and. as the rear wallof the by-pass 67 is continued downwardlvbelow the outflets 74a, 74b and 74 to the floor S4 of the downpass 61.

Thefby pass 6'7 is connected to an ofiset downward extension; 85 of the'downpass 61 by two tunnels 8613xte ndiug through the central part 61b of the downpass 61,

and the floor 84 i's in the forrnof a plurality of hoppers disposed side ,byside across the'width of the downpass, separate hoppers 9t), 91, 92, 93 and .94 being associated respectively with the downpass parts 61a, 61b and 161s and the two tunnels '86, each of these latter two hoppers being extended sidewardly. at its front'end 'so that'toparts 65a and i651) respectively on eitherside of and 'both downwardly inclined towards atransversely extendgether they include the whole area below the by-pass 67. Thelowei' ends of the by -pass 67 and the'downpass "61' constitute gas, turning spaces disposed above the hoppers.

*of' the rear wall7 5 of the dcwnpass 61, and has connected to it spaced tubes 1t33 which extend vertically upwards to line the rear wall 75,'at the top ofwhich they are bent forwardly to line the roof 165 of the downpass 61 and the roof 107 of the part of the lateral gas pass '60 rearwardly of the, furnace wall 4, these tubes being bent upwardly adjacent the gas outlet 19 to'extend through the roof 107, above which they are connected to a header 168. Other tubes. 169 extend horizontally from the'inl'et header 1% across the downpass 61 to the partition wall 82, and then extend upwardly to a' location adjacent the opening66 to form, with suitable" refractory material, the wall 32. At the opening 66, alternate tubes 109a continue'vertically upwards through the gas pass as a screen of spaced tubes and through the roof 107 of that pass, above which they are connected to the header 168. The remainder 1695016 the tubes 169 tend as a screen of spaced tubes upwardly to and through the roof 1052 of the downpass 61, abovethelevel of across the downpass 61 and across the by-pass 67 to front Wall 111 of the by-pass, and then extend upwardly to line that wall as far asthe opening 66, above which alternate tubes 116a are continued upwardly across the lateral gas pass 66 as a row of spaced tubes and through the root 167, above which they are connected to the header 103. The remainder 1145b of the tubes 119 are bent forwardly above the opening 66 to line the part-65a of the floor of the lateral gas pass 60, and adjacent the lateral gas outlet 19 are bent upwardly to extend as a row of spaced tubes across the lateral gas pass 60 and through the roof 167, above which they are connected to the header 1%. Parts of the tubes 16% and 116:; above the opening 66 are covered with refractory material to define an upward extension 67 of the by-pass 67 while leaving openings 11561, 11515 between tubes 169a and 119a respectively for the downward passage into the by-pass of tooling fallingon the parts 65b, 65:: respectively of the floor of the lateral gas pass 6t). r

The upper parts of the side walls 77 and 73, the partition walls 72 and 73 and side walls 116a, 1165 of the .by-pass 67 are also provided with vapor heating tubes. Thus headers 117, 118, 11 9 and 12% (see Fig. 8) are disposed in the walls 77, 72, '73 and 78 respectively a short distance above the level of the gas outlets 74a, 74b

and 74s, and tubes 121, 122,123 and 124 extend upwardly from the headers 117, 118, .119 and 120 respectively, tubes 1 21 and 124 serving to line thewalls 77, 116a, and i3, 116b respectively, and the tubes 122, 123, together with refractory materiahconstituting the walls 72 and 73. The tubes 121 and 124 which are associated withthe forward ends of the walls 77 and 78 and with the another'in order thatthey may linenot only the side Y 'walls of the gasp'ass 61 and theupward. extension 67 of the by-p ass, but also the whole of the sidewalls of the 7 part of thelateralgas pass 60rea'rwa'rd of the plane of furnace wall .4. At their upper ends, the groups of tubes 121,122, 123 and 124. are connected to headers corre; sponding to the headers 1'17, 118, 119 and 120, such as,

for example, headers 125 and 126 corresponding to headers 118 and filgrespectively; These four upper" headers are connected by tubessuchas 127 to the header 193.

' A convection primary superheaterf is disposed in the part 610 of the downpass 61 and comprises sinuous tubes 136 arranged .in threebanks 137a, 137b and 1370 iin'the part of the downpass below the level of the opening 66, the lower end of each tube 136 being connected to aninlet header 138 disposed in the front wall 111 of'the by-pass 67 and connected by tubes such as 139 to the headers 117, 118,119 and 120.1. Adjacentthe level of the opening 66, alternate pairs .136uYof-the tubes 136 are bent 'upwardly adjac'ent the partition-wall 82and are arranged between the tubes .1091) to help form the part 655 of the floor of the lateralgas pass 69, at the'rearmost end ofwhich they'are'bent upwardly andextend as two rows of'spaced tubes across the rearward end-of thegas'pass 69 to and through the room 105, above which they are reversely bent andenterfthelateral' gaspass .60 to form part of a fourth tube bank 137d of thelprirna ry V superheater, disposed above the floor part65bf1Ihere- :are' bent' rearwardly 1 and inclined upwardly along the 'part 6517 of the floor of the lateral gas 'pass 69,.at the 'rearmostyendof which they are bent upwardly; and 'exi which they are connected to the. header 1tl8. Still other tubes, 110, extend horizontally the inlet heade 100 mainder13j6b of the tubes 13.6 are bent. upwardly at'approximately the mid-depth'of'the dcwnp'ass 61 to extend upwardly as two rows of spaced tubes toandthrough thereof 135,- wherethey rejoin thetubes 136a'to forrn the remainder of the tube bank- 137d. r

In the tube bank 137a, the tubes '13s are angs a anpi tch across 'the width of the gas pass equal'tdtwice the pitch of the tube parts in the banks 137a, 137b and 137a, and are sinuously bent soth'ati each'tubetraverses the height of the lateral gas pass several times, and atthe gforward end of theban'lr 137d,.the tubes.;136:extend upan outlet header 185. ,mary reheater 179 is connected to the exhaust from a a d v throug h '9 and a e rs e y to 1 enter the gas pass rfilabove the by-pas s 67,;the tubes being bent to form :U-tubes consti'iizting a tube bank 13% of the primary superheater. At the forward end of the tube bank 137e, the tubes 136 extend upwardly through the roof 1 97 and are connected to an outlet header 140. A second connection primary superheater 145 is disposed in the part 6 1:: of the downpass 6 1 and like the supe rhe ate r 1p comprises sinuous tubes arranged in banks 147a, M712, 147c, 147d and 147a respectively similar to the banks 137a, 1375, 1370, 137d 1372.

The outlet header 1 3 of superheater 135 and the corresponding outlet header of the superheater 145 are both connected byconduits 159 to an attemperator 151, which may be of any suitable known type, and the outlet for cooled steam from the attemperator is connected by conduits 152 to header 1523 serving as the inlet header for a secondary convection superheater 155 comprising sinuous tubes 156, each counectedat one end .to the-header 153.

The tubes 155 extend downwardly through the roof 107 and aresinuously bent so that each traverses the height of the lateral gas pass several timesto form a first tube bank 157;: disposed in the part of the lateral gas pass 63 above the arch 2t} and between the rows of tubes 17aaand 1711b. At the rearward end of the tube bank 157a, the tubes 156 extend upwardly through the roof 197, and are reversely bent to re-enter the gas .pass 60 above the floor part .6541, where the tubes are again sinuously bent to form a second tube bank l'57bdisposed in the part of the lateral .gas path betweenthe rows of tubes 1119a and 11%. Both the superheater banks 157a and 157i: extend across the full width of the lateral gas pass 69, as indicated clearlyin Fig. 3. At the rearward end of the bank 157b, the tubes rss extend upwardly through the roof 107 and are connected to an outlet header 169 itself connected by a steam main indicated at 161 to the high pressure stage of an associated turbine, not shown.

A convection primary reheater 170 (Fig. 2) is disposed in the part 6112 of the downpass 61 and comprises sinuous tubes .171 arranged-in three banks 172a, 1725 and 172a in the part or the downpass below the level of the opening es, the lower end of each tube 171 being connected to an inlet header 173 disposed outside the rear wall '75 of the downpass. Adjacent the level of the opening as, alternate pairs 3171a ofthe tubes 171 are bent upwardly adjacent the partition wall 82 and are arranged between the tubes 13% to help form the part 65b of the floor of'the lateral gas pass 6t), at the rearrnost end of which they are bent upwardly-and extend as two rows of spaced tubes across'the rearward end of the gas pass 6% to and through the roof 135, above which they are connected to'an outlet header 17 The remainder 171 of the tubes 17-1 are bent upwardly at approximately the mid-depth of the downpass -61 to extend upwardly as two spaced rows of spaced tubes to and through the roof 1%, above which they are connected to the outlet header 17 The outlet header 174 is connected by pipes 175 to the inlet header 13a? of a convection secondary reheater 131 comprising tubes 182, the spacing of which transversely of the gas pass (ad is about twice the spacing of the parts of tubes 71 in the tube banks 172a, 1721: and

172a transversely of the downpass 61. Each tube 182 is lower ends to form a second tube bank 13-35 and returning through the roof 197 above which they areconnected to The inlet header 173 of the pri- 6 i h Pr ure s e o the as oc a e t n while the outlet header 185 from the series connected secondary reheater 181 is connected to ihe inlet of an intermediate pressure stage of the associated turbine.

Although in the embodiment of the'invention described above, the part 6527 of the floor of the gas pass 6% has been described as being composed of tubes 13%, 135a and 171a together with a refractory material 1% (see Fig. 5) which closes the spaces between the tubes, if desired, the reiractory mater al 199 may be omitted, so tiat the door part 6512 of the lateral gas pass 69 is in the form of a grid formed by the spaced tubes. It is necessary that the tubes constituting the grid be so spaced that they are efiective to prevent the downward passage therebetween of any particles of .suflicient size to block the spaces between the tubes of the subjacent superheater or reheater banks.

In addition, the spacing of these tubes must be suficiently close to ensure that a suiiicient proportion of the hot gases flowing into the downpass shall flow over the superjacent superheater banks 137d and 147a and reheater :bank 18317.

The division of the hot gases flowing from the furnace chamber 1 between the parts 63a, 61b and die of the downpass 6i and by-pass 67 is controlled by dampers Zida, 2%!) and Zhhc respectively arranged in the gas outlets 74a, 74% and 74c and by dampers 292a and 26% respectively arranged at the rearmost ends of the two tunnels 86.

The ofiset downward extension 35 of the downpassl contains three economizer heat exchange sections 265a, 295i) and 2950 and is connected at its lower end with a due 26-5 leading to a chimney (not shown). The extension 35 is provided with a hopper shaped bottom part 2-37.

During operation of the unit described, pulverized fuel is supplied to the-burners 41 and the hot furnace gases pass upwardly through the furnace chamber and through the lateral gas outlet 19 into the lateral gas pass 69, where they pass over the tube banks of the secondary superheater 155. The division of the hot gases between the parts 61a, 61b and die of the downpass 61 and the bypass 67 will depend upon the settings of the dampers 2043a, 20% and 2 3th, 232a and 25321). The deflector plates 7%, 79b and 79c serve-to distribute the hot gases over the depths of the gas pass parts 61a, 61b and olc respectively. From the downpass 51 the hot gases pass downwardly through the extension and into the fine 2% whence they pass to the associated chimney.

Vapor generated in the tubes lining the walls of the furnace chamber 1 is separated from the entraining water in the steam and water drum 14, whence the steam flows through tubes 52; to the radiant superheater 47. From the superheater 47 the steam flows through conduit hi1 to the inlet header 3M and thence through the tubes 193, 18% and 11% to the header 1%, through tubes 127 to the upper headers such as and 125 associated with the tubes 1'21, 122, E23 and 124, downwardly through those tubes to the headers 117, 113, 119 and 12d and thence through the tubes 139 to the inlet headers, for example the header 13d, of the primary superheaters and 145. The steam flows through the parallel connected primary superheaters 135 and 145, through the conduits 159 to the attemperator 15E, and thence through the conduits 31 52 to the inlet header 153 of the single secondary superheater 155, and finally passes from the "superheater through the steam main 161 to the high pressure stage of the associated turbine.

Steam exhausted from the high or an intermediate pressure-stage of the steam turbine is supplied to the inlet header 173 of the primary reheater 170, and passes from the outlet header thereof through the pipes 175 to the inlet header of the secondary convection reheater 181, from the outlet header of which it is returnedto an intermediate or low pressure stage of the associated turbine.

'During operation, the temperatures-of superhat and reheat may be controlled by regulation of the quantity of gases flowing through the by-pass 67 upon adjustment of the dampers 202a, 292b, the temperature-of reheat may be controlled by operation of the dampers 'Ztltta, 2%!) and 2090 to regulate the distribution of gases between the parallel-connected side parts 61a and 610 of the downpass 61 on the one hand and the central part 61b on the other, hand. A rapidly effective control of superheat temperature may also be had by means of the attemperator 151. Suitably, automatic control means are provided to eflect adjustment of the dampers and theattemperator in accordance with deviations from predetermined values of the superheat and reheattemperatures.

It is found that in the operation of a unit such as that described, deposits tend to accumulate on the tubular heat exchanger. surfaces. Such accumulations are periodically dislodged by operation of fluid heater cleaners arranged for the discharge of cleaning fluid over the tubular surfaces, and by virtue of the particular gas pass arrangement described and illustrated, when the part 65b of the floor of the gas pass 60 is imperforate, as illustrated in Fig. 5, accumulations dislodged from tubes in the lateral gas pass 60 do not fall onto the tube banks j disposed in the .downpass 61, but are diverted into the chute or by-pass 67 and fall into the hoppers 93 and 94, from which they may be removed as and when desired. Suitable fluid heater cleaners or soot blowers are operable at distributed positions such as 219-220(Figll): Such .a soot blower is indicated by the Snow et a1. Patent 2,110,534, Mar. 8, 1948,01 Patent 2,126,683.

In the alternative arrangement referred to above, in which the refractory material is omitted from the floor part 65b of the pass 60, the larger pieces of dislodged accumulations are caused to fall downwardly through the chute or by-pass 67, and only the smaller pieces, which can fall between the tubes in the downpass 61, are allowed to fall through the floor into the downpass 61. By the correct spacing of the tubes which form the grid, only pieces of such size as will pass between the tubes in the tube banks in the gas pass 61 are permitted to enter the downpass.

Dislodged deposits falling downwardly through the gas downpass parts 61a, 61b and 610 are collected in the hoppers 90, 91 and 92 respectively, from which they may .be removed'as and when desired.

.theldownpass from one side thereof as far as the opposite .side thereof. .ment so far described, and similar. parts are denoted by However, a gas turning space 309 is provided by a protuberance 3 331 built'onto theupper end of the rear wall 75 of the gas pass 61, the space 300 being divided into'three parts by In mostrespects it is similar to the embodithe numerals used in the first'embodiment.

rearward extensions of the walls 72 and 73. The lower end 30; of the protuberance StilJformed as three hoppers forthe'collection of ash separated from the furnace gases as they pass through the. three partsof'the space '300 respectively. I

In this'arran'gernent, the tube bank s' 147d, 147e, 1371!,

137e, 183a and 183 b are all disposed above the part 65b @of the floor of the lateral gas pass 60; the upper ends of' the tubes 10% are continued a s'hortdistance beyond the tubes'103 which linethe downpas s rear wall75 and then extend as a row of spaced tubes'to and through the roof I. a

107; and the tube parts 136a, 136b,.171a and 17Ib are continued towards and extend upwardly adjacent the rear c wall 303 of the gas turning space 300.

In this embodiment, the part 65b of the floor of the lateral gas pass 60 may include refractory material as shown inFig. 5, or the refractory material may. be omitted and the floor left as a grid of suitably spaced tubes.

The operation of the embodiment shown in Figs. 9'and scribed above with reference to Figs. 1 to 8.

In the arrangements described, furnace gases may safely be admitted to the lateral pass at. high tempera- "ture and adequate heat exchange surface is provided for suitably cooling the gases before they reach the downpass. The high temperature of the gases at the inlet to the superb-eater, the transverse flow of the gases over a all the vapor heating tubes and the extension of the lateral pass over the downpass enable a relatively compact arrangement to be achieved. The vapor heating surface arrangement described, utilizing wide tube s'pacing and upright pendent tubes in the pass 60, enables :adequate cleaning means to be installed and to be efiectively used and suitable provision is made for the disposal of matter dislodged from the vapor heating tubes in the gas pass 6! i 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 detailsthereof. It is'rather to be taken as of a scopecommensurate with the scope of f the subjoined claims;

What is claimedis:

1. In a vvapor generating and superheating unit, a furnace having its. walls lined with vapor generating tubes, means firing the furnace with a fuel. resulting in solid particles in suspension in the furnace gases, meansforming a gas pass leading from the furnace, a secondary vapor superheater in an upper part of the gas pass, a

primaryv superheaterin a lower part of the gas pass. and at least partly disposed beneath the secondary superheater, means periodically dislodging solids: accumulations on the secondary superheater, means forming a disposalzone for dislodged solids beyond the primary superheater relative to' gas flow, means formingha pri-.

mary superheater gas by-pass leading from a position beneath the secondary superheater to-said disposalzone whereby accumulations dislodged from=the secondary superheater pass to, thedisposalzone without contacting the primary superheater and gasflow regulating means for controlling the amount of gas flow through thby pass.

2., in a vapor nace having its walls lined with vapor generating tubes,

means firing the furnace. with a fuel. resulting insolid particles in suspension. in the furnace gases, means forming a gasp'alss leading' frorn the furnace,1asecondary vapor superheater in an upper part-of the, gas pass, a

reheater in a lower garter the gas passand attleast partly V disposed 'beneaththe secondary superheater, means periodically. dislodgin'g "solids. accumulations on the second- 7 ary superheater, means forminga disposal zone for discontactingthe reheater, andgas fiow're gulatingl'means for controlling the amount of gas flow through the 'by- 3. In a vapor generating and superheating unit, a furnace having its walls lined withvap'or generating tubes, means firing' the furnace with a fuel resulting in solid particles in'suspension inthe furnace gases, means forining a gas pass 'leading'j from the furnace,fa' secondary vapor superheater'in'an upper part of the gas passja generating and superheatingunit,

primary superheater having a part disposed in: a lower part of the gas pass and at least partly disposed beneath the secondary superheater, m-sans periodically dislodging solids accumulations on the secondary superheater, means forming a; disposal zone for dislodgedsolids beyond the primary superheater relative to gas flow, means forming a primary superheater gas by'pass leading from a position beneath the secondary superheater to said disposal zone whereby accumulations dislodged from the secondary superheater pass through the lay-pass to the disposal zone without contacting the primary superheater, and gas flow regulating means for controlling the amount of gas flow through the by-pass, the by-pass having downwardly converging hopper-like walls at its entrance immediately below the secondary superheater.

4. In a vapor generating and s'uperheating unit, a vertically elongated furnace, means firing the furnace with a fuel resulting in solid particles in suspension in the furnace gases, vapor generating tubes lining the Walls of the furnace, a lateral gas pass leading rearwardly from the upper part of the furnace, upright tubes forming a pendent secondary superheater disposed in the inlet section of said gas pass, other upright tubes forming the pendent section of a primary superheater subject to gas flow in said pass next after the secondary superheater, an inlet header for the primary superheater, means forming a downflow gas pass leading from the outlet of the lateral gas pass, upright partition walls including superheater wall tubes dividing the downflow pass into a middle reheater pass and two symmetrical side passes, a reheater in the middle pass, primary superheater components in said side passes, means including superheater wall tubes forming a gas by-pass for the reheater and primary superheater components, the by-pass leading downwardly from the lateral gas pass at a position forwardly of the downflow pass and having a hopper-like inlet for receiving deposits dislodged from the secondary superheater, means for dislodging deposits from the secondary superheater, hoppers constituting solids disposal zones at the lower ends of the by-pass as well as the middle reheater pass and the superheater side passes, means for independently controlling gas flow through the by-pass as well as the reheater pass and the side passes, means including said superheater wall tubes for conducting superheated steam from the vapor generating tubes to the inlet header for the pendent primary superheater section, steam flow connections whereby steam flows from the pendent primary superheater section to the superheater components in said side passes and then through said components to the secondary superheater, the reheater including a pendent section of upright tubes receiving reheated steam from the reheater in said middle pass, and means including an attemperato-r whereby superheated steam is conducted to the secondary superheater.

5. In a vapor generating and superheating unit, a vertically elongated furnace, means firing the furnace with a fuel resulting in solid particles in suspension in the furnace gases, vapor generating tubes lining the walls of the furnace, a lateral gas pass leading rearwardly from the upper part of the furnace, an inwardly extending furnace wall arch disposed below the inlet to said gas pass, a similar arch extending from the front furnace wall into the furnace at a level below that of the first arch and forming an alcove with the furnace surfaces thereabove, upright tubes forming a radiant superheater disposed in said alcove, upright tubes forming a pendent secondary superheater disposed in the inlet section of said gas pass, other upright tubes forming the pendent section of a primary superheater subject to gas flow in said pass next after the secondary superheater, means forming a downflow gas pass leading from the outlet of the lateral gas pass, upright partition walls including superheater wall tubes dividing the downflow pass into a middle reheater pass and two symmetrical side passes, a reheater in the middle pass, primary superheater components in said side passes, means including superheater wall tubes forming a gas by-pass for the reheater and primary superheater components, the by-pass leading downwardly from the lateral gas pass at a position forwardly of the downflow pass and having a hopper-like inlet for receiving deposits dislodged from the secondary superheater, means for dislodging deposits from the secondary superheater, hoppers constituting solids disposal zones at the lower ends of the by-pass as well as the middle reheater pass and the superheater side passes, means for independently controlling gas flow through the Dy-pass as well as through the reheater pass and the side passes, means conducting generated vapor from the furnace wall tubes to the radiant superheater, means including said superheater wall tubes for conducting superheated steam from the radiant superheater to the inlet header for the pendent primary superheater section, steam flow connections whereby steam flows from the pendent primary superheater section to the superheater components in said side passes and then through said components to the secondary superheater, the reheater including a pendent section of upright tubes receiving reheated steam from the reheater in said middle pass, and means including an attemperator whereby superheated steam is conducted to the secondary superheater.

6. In a vapor generating and superheating unit, a vertically elongated furnace, means firing the furnace with a fuel resulting in solid particles in suspension in the furnace gases, vapor generating tubes lining the walls of the furnace, a lateral gas pass leading rearwardly from the upper part of the furnace, upright tubes forming a pendent secondary superheater disposed in the inlet section of said gas pass, other upright tubes forming the pendent section of a primary superheater subject to gas flow in said pass next after the secondary superheater, an inlet header for the primary superheater means forming a downflow gas pass leading from the outlet of the lateral gas pass, upright partition walls including superheater wall tubes dividing the downflow pass into a middle reheater pass and two symmetrical side passes, a reheater in the middle pass, primary superheater components in said side passes, means including superheater wall tubes forming a gas by-pass for the reheater and primary superheater components, the by-pass leading downwardly from the lateral gas pass at a position forwardly of the down flow pass and having a hopper-like inlet for receiving deposits dislodged from the secondary superheater, means for dislodging deposits from the secondary superheater, hoppers constituting solids disposal zones at the lower ends of the by-pass as well as the middle reheater pass and the superheater side passes, means for independently controlling gas flow through the by-pass as well as through the reheater pass and the side passes, means including said superheater wall tubes for conducting superheated steam from the furnace wall tubes to the inlet header for the pendent primary superheater section, steam flow connections whereby steam flows from the pendent primary superheater section to the superheater components in said side passes and then through said components to the secondary superheater, the reheater including a pendent section of upright tubes receiving reheated steam from the reheater in said middle pass, and means including an attcmperator whereby superheated steam is conducted to the secondary superheater, one wall of said hopper-like inlet being disposed above the primary superheater components and including tubes spaced apart to permit only small particles of dislodged accumulations to pass therebetween and thence to said components.

(References on following page) I 11 References Cited in the file of this 'paiienf 7 T5 V UNITED STATES PATENTS l,

2,027,495 Turner Jan. 14,1936 2,343,112 Hibner et a1. 1%. 29, 1944 12 V Woolley May 15, 1951 Woolley Sept. 2, 1952 FOREIGN PATENTS V Germany Nov. 17, 1943

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