US2513328A - Steam generator - Google Patents

Description

y 50 J. H. JACOBS 2,513,328

STEAM GENERATOR Filed Dec. 22, 1945 5 Sheets-Sheet 1 gOQOOQO...

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INVENTOR John H. Jacobs ATTORNEY J- H. JACOBS STEAM GENERATOR July 4, 19.50

3 Sheets-Sheet 2 Filed Dec. 22, 1945 INVENTOR John H. Jacobs ATTORNEY y 1950 J. H. JACOBS 2,513,328

STEAM GENERATOR Filed 22. 1 5 s Sheets-Sheet s INVENTOR John H. Jacobs m ATTORNEY Patented July 4, 1950 UNITED E S OFF CE 2,513,328 STEAM GENERATOR John H. Jacobs, F'anwood, N. JL, assignor'to The Babcoclt & Wilcox Company, Rockleigh; N. 1., alcorporation of New Jersey Application December 22, 1945', Serial No. 636,908

3 Claims. 1.

This invention relates to a pulverized coal fired'steam generator in which the'major portion of the steam is generated by heat radiantly transmitted to'furna'cewalltubes. It is an im'- provernent'inthe' type of 'vapor generator utilizing the open-pass method ofchilling of molten ash carried from the furnace with the products of combustion.

An object of the invention is the enhancement of the separation of molten ash in the high temperature gas'zones of the furnace.

A further object of the invention is to increase the flexibility of operation in that ash bearing fuels having ash of high fusing and melting temperaturecharacteristics can be sep'- arated'an'd'discharged from the furnace at comparatively low ratings of unit steamoutput.

A further object of theinvention is the attainment of high rates of heat transfer to radiantly heated st'eam generating tubes, whereby an'optimum extent of heat absorbing surface is required-to accomplish radiant cooling of'furnace gases.

These objects and others are attained by a steam generator in which a high temperature combustion zoneis provided adjacent a molten slag discharge port, with a-subsequent high temperature combustion gas zone bounded by steam generating tubes of high heat absorptive capacity in open radiant heat transfer relationship to the first zone, followed .by ashieldedbpen-pass gas and ash chilling zone discharging the residual products of combustion to the convection heat absorbing Water and steam heating surfaces which are presented primarily by economizer and superheating tubes.

Various features of novelty of" the invention are pointed out with particularity in the claims annexed hereto and forming a part of this specification, and, for a better understanding of the invention and the specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

In the drawings:

Fig. l is a vertical section through a high capacity steam generating installation of the open pass type, constructed in accordance with the teachings of the invention;

Fig. 2 is a View in the nature of a vertical section through the furnace floor and adjacent steam generating tubes opposite the burners;

Fig. 3'is a horizontalsection on the line 3-3 Fig. 4 is a vertical section on the line 4'4 of Fig. 2;

Fig 5*isavertical section of a modified steamv generator, within the scope of the invention;.

Fig. 6 is" a fragmentary horizontal section on. theline fi -6 of Fig. 1' and indicatingth'e' refractory linedfurnace wall construction employed in the-high temperature zone of the furnace;

Fig; 7 is a fragmentary horizontal section on the line l-l of Fig. 1, showing the bare tube wall construction of the furnace chamber;

Fig. 8 is a fragmentary horizontal section on the line 8 8 of- Fig. 1 showing the finned tube construction of the'wall between the high temperature furnace and the open pass;

Fig. 9 is a vertical section on the line 99 of Fig. 1, showing the furnace gas outlet at the upper part of the furnace chamber 10 in elevation; and- Fig. 10' is a partial horizontal section on the line 1 W of Fig. 1.

The steam generating installation indicated in Fig. 1 of the drawings includes an upwardly extending elongated high temperature furnace chamber Hi to which'pulverized solid fuel is introduced at the lower portion. The boundary surfaces are delineated by upright heat absorbing steam generating tubes ll' communicating at their upper ends with the steam and Water drum [4 and at their lower ends with the submerged header or'drum IS. The circulatory system including the tubesis completed by one or more large diameter external water downcomers, such as l8, connecting the steam and-Water drum [4' and the lower drum It.

The hightemperature furnace chamber l'flhas a comparatively high temperature zone extending transversely of the chamber and havinga highly refractory walllining, as indicated at 20; carried on the inner faces of the tubes It. This lining extends to a position abovethe burners and has a controlling influence upon the heat flow from the high temperature zone to the covered" tube portions. It also acts to minimize tube metal wastage resulting f'romconstituents of'the molten ashoccurring in this zone. A similar highly refractory covering '22 covers the other tube portions 23" which are-extensions of the front wail tubes l3; forming a heat resistant floor to support' a pool of separated molten ash resulting fromthe combustion of pulverizedfuel'introduced to the furnace with high temperature air'byv the turbulent type burners 24and 261.

The burners provide for quick ignition and rapid combustion of thefuel with the high tem zone of substantially rectangular cross-sectional;

flow area from which the gaseous products of combustion are discharged through the laterally positioned tube screened outlet 34 tothe top of the open pass 36. The construction of the upper portion of the furnace H1 is distinctive in that the tubes H are closely spaced to provide a substantially closed bare metallic lining for the side and front walls, while the rear wall 38 which is common to the furnace l and the open pass 36 is formed of ;more widely spaced tubes (such as 859!!) with metallic space closures 4| as indicated by Fig. 8 taken along section 88 of Fig. 1.

, The upper portions of the tubes of wall 38 are bent out of alignment at their upper ends to pro-v vide a gas outlet from furnace 10 to gas pass 35 while screening the latter from radiant heat transmission from the upper portion of furnace Ii]. These tubes are connected at their upper ends to the. steam and water drum which is located above and between the furnace l0 and the open'pass 36. The walls of the open pass are delineated by highly heat conductive steam gencrating tubes connected in a circulatory arrangement with the steam and water drum.

, Below the level of the molten slag outlet 30 and below the open pass 36 is an ash and slag discharge pit 4!) for the disposal of solids separated fromthe gases passing downwardly through the open pass and turning as indicated by arrow 42 into the pass 44 of the convection section. As shown, this convection section consists of banks 52-55 of spaced convection superheater tubes arranged as horizontal coil sections extending across the path of the gases. The superheater inletv header 60 is connected by the tubes 62 and {54 to the steam space of the steam and water drum l4, and saturated steam passes from the header 60 through the series connected tubes of the superheater banks 52 and 53 to the intermediate outlet header 66. From that outlet header, the steam passes through the conduit 68 to an attemperator 10 for controlling the final steam temperature.

From the attemperator, the steam passes through a conduit 12 to the inlet header 14 of a second section of the superheater consisting of the. banks of tubes 54 and 55. From this section, the steam passes to the outlet header l6 and thence to a point of use.

In the. illustrative steam generating and superheating installation, where superheat temperatures of the order of 900 to 950 F. are desired, it is essential to provide heating gas temperatures at the superheater gas inlet high enough to provide sufficient temperature differential between the gas and the tube metal to economically attain sufficient heat transfer. On the other hand, in the interest of decreased outage for cleaning as well as operation at substantially uniform high superheat temperatures it is most important that an external heat insulatin accumulation of slag or ash originating from the productsof combustion on the superheater tubes be avoided as far as economically possible. The ash constituents of the products of combustion are to be eliminated, in so far as economically desirable, before the heating gases contact the superheating surface, while retaining the gases at temperatures of the order of 2000 F. at which deposits of residual ash particles will be at a minimum and the gas temperature is sufficient for effective superheater performance.

The present invention accomplishes these objects by eflecting a high degree of radiant heat absorption and a separation of a major portion of the molten ash constituents of the products of combustion, in the high temperature furnace zone, and then utilizes the open pass cooling of gases and gas borne ash particles for further reduction of temperature and gas ash content to a degree acceptable as heating gases for the convection superheater.

In the operation of the present steam generating installation the turbulent combustion in the higher temperature zone in the lower portion of the furnace can be considered to give an-adiabatic combustion temperature of the order of 3600 to 3700 F., thereby insuring a gas temperature in that zone which will enhance the molten ash separation due to the proximity to the Slag pool but will also be effective in maintaining the superposed open Zone of the furnace at high gas temperature as the result of radiant heat transfer. With the high temperature gases moving upwardly through the upper zone, which is surrounded by highly effective metallic walls, a high rate of heat transfer to the walls is attained and the molten ash deposited thereon is maintained in a highly fluid condition permitting it to flow downwardly to the pool without material accumulation on the wall surface. With the arrangement shown the gas temperature reduction will be to a temperature corresponding approximately to the melting temperature of the fuel ash and the open-pass will reduce the temperature down to the desired level.

With the arrangement as above discussed, I have found that in addition to accomplishing the desired degree of gas temperature reduction and ash separation, a materia1 reduction in the extent of radiant water cooling surface necessary is attained. This reduction may in certain cases, depending upon the characteristics of the fuel, amount to as much as 17% of radiant heat absorbing surface as compared with shielded surface arrangement for the gas cooling zone beyond a high temperature combustion zone, with a corresponding reduction in cost.

A reduction in furnace draft loss also results from the specified arrangement of operative elements of the hightemperature furnace.

Figs. 2', 3, and 4 show the details of one of the fluid cooled slag outletsfor the high temperature furnace section at the burner zone. Such an outlet is indicated at inFig. 3, and the associated arrow 82 indicates the general flow of fluid slag to the outlet. Some of the tubes such as 85-90 of the heat absorbing wall 38 common to the furnace chamber in and the open pass 36 have portions near the furnace floor 22 which are bent outwardly as indicated in Fig. 3 to form the slag outlet 85]. The positioning of these tubes at the slag outlet is further. indicated in Fig. 2 and Fig. 4 shows a body 8| ;of highly refractory ceramic material disposed on the lower sections of the bent portions of the tubes 85- -9!) to form a continuation of the upper surface of the furnace floor 20 for slag flow over the outletgbarrier presented; by the: series connected tube: sections 9.-l:--l of the hind; cooled! coil indicated -generally by the: numerali um This coil: is supplied witln water: or other fluid' under such: tempera t'urev andi'rate of. flow" conditions: damage by the. high temperature slag: is substantially" pr-e' vented; Such fluid enters the coil inlet l l 2 a nd, after proceeding through the sections of the coil passes. out through the outlet M 4- as-' indicated. by the arrows l l fi and I I -B=.in-Figi 2'.

Referringagainto Fig.1), the gases after leav-- ing the banks of superheater tube's ..5255 pass" across the banks: of tubes-' fifl il \vhichare economize-r tubes; -Thereaf-t'er, the gases pass through the airheater' tubes Mir-connectingthe tube sheets I22 and I24 Thence the gases-pass from the outlet I=2-6 to a stacls The duct work sectionsi tall-M2" and the airheater casement-sections 13A I 35 direct air from the airheater inlet I40 over the air-heater tubes in the first air pass M2, and then around the bafiie- M4 to the entrance: 1 46 of the seconda-ir pass I48. After passing over the air tubes in this second air pass, the gases turn as indicated by the arrow I50'and pass throughthe last air pass i52, through the ductworksections H2 and I30, and then to thesecondary-airchamber Fig. 1' alsodiscloses headers Milt-482+! 8% for the side wall tubes. The lower headers are connected either to the lower water drum l6 and the upper headers such as 18''}! and lMiar-e con nected to the steam and water-drum M;

The modified steam generator illustrated in Fig. has a high temperature furnace chamber section 239 the boundary surfaces of which are formed by steam generating: tubes such as those defining the walls 2M and 203'. These tubes are connected into a circulatory system including steam and water drum 20-2, the header 2M and the submerged drum or header'2ll6.

Above the high temperature furnace chamber 20!! is the furnace chamber 240; the wall tubes of which are subject to radiation from the high temperature chamber 206. This results in increased rates of heat absorption through the tubes defining the secondary chamber 2H), and, when pulverized fuel is utilized by the burner 2 l 2, the residual solids along the walls of the chamber 2 I U are maintained in a fluid state.

From the top of the furnace chamber 2H1, the gases flow in the direction of the arrows 2M and 2l6 into the top of the open pass 220. In this pass the gases flow downwardly toward a solids deposition zone 22I toward which fused slag from the furnace floor 224 flows through the outlet 226.

The open pass 220 is separated from the furnace chambers 208' and H0 by .a common heat absorbing wall 230 formed by steam generating tubes such as 232 and 236 directly connecting the drums 202 and 206 as shown. Preferably, at least the furnace sides of the tubes of the walls 230 are covered with a highly refractory material and the slag outlet 226 is formed in a manner similar to that previously described in connection with the description of the steam generator of Fig. 1.

Between the flue 240 and the gas turning zone 242, the gases pass upwardly through the gas pass 244 over the tubes of the superheater sections 246 and 249, as well as tubes of the economizer Section 248. At the inlet of the convection section: gas pass 2M; the gasespass over a fluid cooled screen" 25c formed by partSmf steamL-gene crating tubes which directly connect the steam and water drum 232 and the lower headen 252 as= indicated- 1h the drawings.

What is claimed is:

1. In a vapor generator, rows-of upright-vapor generating tubes delineating a vertically elongated and; unobstructed combustion chamber of" rectangular horizontal cross-section; fuel burnersat the lowerpart of the combustion chamber and firing the latter with a high temperature ignition-section at the lower part of the-'combus tion chamber, the combustion chamber extendingi vertically toan extent several times the=height of the high temperature section without" such' diminution in the horizontal cross -section aresuof: the combustion chamber as to create substany tially higher gas velocity; additional rowsof up'-' right vapor generating tubes combining withsome of the first mentioned tubes. to: delineate a vertically elongated upright open gas pass theinlet-of which communicates withthe combustion chamber at the top of the latter, said operr passinlet being positioned laterally oi the upper zone of the combustion chamber which is delineated" by substantially completely metalsurfaces pre sented by the upper portionsofsome of the first mentioned tubes, one of said-first mentionedrows of tubes delineating a separating wallcommonto the combustion chamber and said gas pass'; the vertical? height of the opengas pass-being of the same order as the verticalheight of the combus-- tion chamber, means constituting aconvectionsection and including a gas pass the lower end of which is in gas flow communication with the open pass at-substantially the same level as that of the high temperature section of thecombusa tionchamber, other vapor generating tubes delineating a combustion chamber-floor norma-l"- ly retaining a pool ofmolten ash deposited from the fuel, said fuel burning means normallydirecting burning fuel across said slag po'oland toward a; slag discharge opening throughsaid separating wall, the slag dischargeopeni'n'g being disposedoutsidethe main path of' furnace gases from the combustion chamber to the convection section, the metallic walls of the first mentioned rows Of tubes being directly exposed to the products of combustion throughout the major portion of the combustion chamber height and also directly exposed to radiant heat of said high temperature ignition section, and means maintaining fluid circulation through said tubes.

2. In a vapor generator, rows of upright vapor generating tubes delineating a vertically elongated and unobstructed combustion chamber of rectangular horizontal cross-section, fuel burners at the lower part of the combustion chamber and firing the latter with a high temperature ignition section at the lower part of the combustion chamber, the combustion chamber extending vertically to an extent several times the height of the high temperature section without such diminution in the horizontal cross-section area of the combustion chamber as to create substantions of the first mentioned tubes, one of said first mentioned rows of tubes delineating a separating wall common to the combustion chamber: and said gas pass,'the vertical height of the open gas pass being of the same order as the vertical height of the combustion chamber, means constituting a convection section and including an upright gas pass the lower end of which is in gas;

burning. fuel across said slag pool and toward, a slag discharge opening through said separating wall, theslag discharge opening being disposed outside the main path of furnace gases from the combustion chamber to the convection section,

the metallic walls of the first mentioned rows of tubes being directly exposed to the products ofv combustion throughout the major portion of the,

combustion chamber height and also directly, exposed to radiant heat of said high temperature ignition section, and means maintaining fluid circulation through said tubes.

3. In a vapor generator, rows of upright vapor generating tubes delineating a vertically elongated and unobstructed combustion chamber of rectangular horizontal cross-section, fuel burners at the lower part of the combustion chamber and firing the latter with a high temperature ignition section at the lower part of the combustion cham ber, the combustion chamber extending vertically to an extent several times the height of the high temperature section without such diminution in the horizontal cross-section area of the combustion chamber as to create substantially higher gas velocity, additional rows of upright vapor generating tubes combining with some of said first mentioned tubes to delineate a vertically elongated upright open gas pass the inlet of mentioned rows of tubes being directly exposed which communicates with the combustion chamber at the top of the latter, said open pass inlet leading from the combustion chamber at a position where the inlet-faces metallic walls formed by the highly heat conductive upper portions of the first mentioned tubes, one of said first mentioned rows of tubes delineating a separating wall common to the combustion chamber .andsaid gas pass, the vertical height of the open gas pass being of the same order as the vertical height of the combustion chamber, means constituting a convection section and including an upright gas pass the lower'end of which is in gas flow communication with the open passv at a level substantially the same as that of. the high temperature section of the combustion chamber, other vapor generating tubes delineating a; combustion chamber fioor normally retaining a pool of molten ash deposited from the fuel, said fuel burning means normally directingburning fuel across said slag pool and toward a slag discharge opening through said separating wall, the lower portion of said separating wall being inclined to thereby face downwardly toward the slag pool and form .a lower portion of said high temperature section extending toward the gas burning zone belowthe open pass and the convection section, the slag discharge opening being disposed outside the main path of furnace gases from the combustion chamber to the convection section, the metallic walls of the first to the products of combustion throughout the major portion of the combustion chamber height and also directly exposed to radiant heat of said high temperature ignition section, and means maintaining fluid circulation through said tubes.

- JOHN H. JACOBS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Bailey Jan. 6, 1942 Certificate of Correction Patent No. 2,513,328 July 4, 1950 JOHN H. JACOBS It is hereby certified that error appears in the printed specification of the above numbered patent requiring correct10n as follows:

Column 8, line 26, for the word burning read. turning;

. and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Oifice. Signed and sealed this 23rd day of January, A. D. 1951.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

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