US2608959A - Steam generator - Google Patents

Description

C. H. WOOLLEY STEAM GENERATOR sept. 2, 1952 5 Sheets-Sheet l Filed Deo. '50,A 1947 ATTORNEY INVENTR Uffa/'les H. Woo/ley BY Sept. 2, 1952 c. H. WOQLLEYA 2,608,959

STEAM GENERATOR Filed Deo. 30, 194'? 3 Sheets-Sheet 5 fig.;

lNVENTOR m ATTORN EY patented Sept; 2, 1952 STEAM GENERATOR Charlesv H. Woolley, Cranford, N: J., assignor to The Babcock & Wilcox Company, Rockleigh, Y N. J., a corporation of New Jersey Application December 30, 1947, Serial No. 794,633

This invention relates to improvements in fluid heat exchange apparatus, and itis more particularly concerned with the control of superheat in the operation of a high pressure and superheat water tube steam boiler.

The invention is particularly concerned with the'maintenance of superheat within close limits under conditions which involve widely varying boiler loads, and the steam'boiler with which the invention is concerned involves upright steam generating tubes most of which are furnace Wall tubes. A superheater including spaced tubes, receives steam generated in said tubes and subjects it to the heat from furnace gases. It is one object of theinvention to provide such improvements in apparatus of this type that the requirements of modern high pressure and high temperature steam power plants may be effectively met. Such installations, in the interest of high efciencies of associatedv prime movers, operate at high superheats, and, as the associated steam turbines are apt to be damaged by uncontrolled and excessively wide variations in steam temperatures, it is important that such variations be controlled and limited. A more specific object ofthe invention is to provide a particular means for regulating and limiting such variations in superheat in this type of boiler.

For high superheats, and especially for steam generators in which there is a high ratio of heat of superheat to heat of steam generation, a relatively large superheater tube surface is necessary, but `excessive superheater costs are avoided, and the desired high superheats are obtained by locating the superheater in gas Zones in which the temperatures are as high as practical consistent with safe metal temperatures and with the de-V sired conditions of non-adherence of the particles of slag orv ash suspended in the furnace gases.l

The.'` invention also provides means for bypassing furnace gases about superheater surface in order to reduce heat input and control final steam temperature.

This temperature control results in a iiat superheat curve over the upper rating range of the installation within the limits of temperature permissible by the piping, and turbine receiving the superheated steam. f

It .is an object of the invention to provide a superheater of the cross-tube gas flow type, the elements of which are conveniently arranged for accessibility.

Itis also an object of the invention to provide a; gas bypass about a portion of the cross-tube 6 claims. (o1. 122-477) 2 superheater surface which will direct the bypassed gases over all of the economizer water circuits which are correspondingly subjected 4to heating by gases which flow over the entire superheater. j A further object of the invention is to arrange the cross flow superheater elements in vertically and horizontally extending groups so disposed' with respect to dust separating zones that the separated dust may be conveniently collected inand removed from a single transversely'extend`V` ing hopper.

Other objects of the invention will appear` from the following description referring to the accompanying drawings showing a preferred embodi' ment of the invention.

In the drawings:

Fig. 1 is a vertical section through the illustrative steam generator'and superheater installa--k tion;

Fig. 2 is a transverse horizontal section on the line 2 2 of Fig. 1; and

Fig. 3 is a vertical section of a modification'A of the installation shown in Fig. 1. f

The furnace of the steam generator indicated in Fig. 1 is generally rectangularin cross section, and it is vertically elongated, with its walls dened by steam generating tubes having their upper ends connected to the steam and water drum I0. One of these walls l2 is dened by'- the wall tubes I4 having their upper end portions i6 connected to the drum lil as shown, andtheir lower hopper portions I8 connected to the header 20 which may be appropriately joined by.ap' proprlate downcomer connections to the water downwardly toward the hopper 24 from whichl solids depositing from ithe furnacegases are g periodically removed. The wall tubes I9 which` have portions extending the full length of the baille 22 have more widely spaced upper parts 26 and 28, to form a screen across the gas outlet of the furnace. They are connected to thedrum; l0 as indicated at 30 and 32. A

A small number of the tubes along the wall I5 extendingonly part way along the baille/V `2,2

will then have rearwardly bentvparts 34 extend;- lng across the line of gas flow (indicated by the-v arrow 36) to the inlet of the gas pass 38, just above the hopper `24. Others of the tubes along the wall l5 have parts 40 continuing vertically beyond the lower end of the baille 22, rst crossing the inlet to the gas pass 38 and then extending along the wall 42 at one side of the gas pass. Some of these tubes just above the wall section 42 have gas bypass sections such as 44 bent out of wall alignment so as to forman inlet to the gas bypass 4'6. Thisbypass is defined at its right hand side by the vertical wall 48 extending across the banks 50-52 of the economizer tubes and substantially joined to the wall section 42 by the inclined intermediate wall section 54 carried on the diagonally extending tube portions of the connectors between the down flow banks 5U and 5| and the upflow bank 52. The other side of the superheater gas bypass is formed at its lower part by the wall section 56 which is defined by l the upper portions of the tubes extending along the wall section 42. Beyond this wall section 56 and in vertical alignment therewith is a gas bypass wall 60.

- The ow of gas through the bypassv 46'to control superheat is regulated by the operation of thedampers 63 and 64 either with or without operation of the dampers 65-69, the superheater consisting of banks IU-12 of horizontally extending tubes across the lower part of the gas pass 38 and the banks '|4 and 'I6 of vertically extending tubes disposed immediately rearwardly of the screen tubes 26 and 28 extending across the upright furnace gas outlet.

The cross-flow type of superheater, particularly when the elements are arranged vertically, is advantageous in avoiding excessive accumulation of slag or ash, but a disadvantage is often incurred when a bypass to direct heating gases about superheating surface for the purpose of temperature control is involved. The disadvantageV results from the fact that bypassed gases are of comparative high temperatures, particularly when high pressure and superheats are involved and provisions must be made in the arrangement of subsequent heat absorptive surfaces which are usually provided by economizer tubes so that the heat absorption from the higher temperature gases will not disturb the internal cooling iiuid condition of the economizer.

YThe present invention provides an upright high gas temperature superheater section with transverse gas ow thereover, a subsequent lower gas temperature section with cross-tube gas ovv from which the gases flow to a multiple circuit economizer, and a gas bypass leading from a position between the section and directing heating. gases over tube portions of all of the economizer circuits, insuring that all of the' circuits will be subject to corresponding heat inputs not only from the gas flow through the bypass but also from the gases iiowing from the second superheater section.

Thus, with an economizer having cross-tube gas flow over the three banks 50, 5|, and 52, the

V:lirst two being arranged for down iiow of Water leaving the high temperature section are dividedwith a portion flowing through the bypass to flow over all the-economizer section, while the remainder flows over the low temperature section and then over economizer tube portions of the r section.

same circuits as receive heat from bypass gases.

In the high rating positions of bypass dampers 63 and 64, shown in Fig. 1, the gases in the equalization space or cavity 220 will be of the order of 1700 F. for a high pressure installation, a

vportion of the gases as regulated by dampers 63 and 64 will now over all of the circuits of the down ow and upow ec'onomizer sections, while the major portion of the gases flowing from the superheater section 16 will iiow downward to the inlet of the gas pass 38, and then upwardly over the horizontally extending superheater tubes.

The provision of the cavity 220 and the position of the bypass inlet at the lower end of the wall 56 contribute to a reduction in the dust carried by the gases which ow rearwardly through the inlet after having passed downwardly along the wall 56. Bypass gases thus must execute a turn of 180 in the zone of the bypass inlet and this turn will have a tendency to separate the heavier dust particles which will pass on down along the rear wall 42 to be collected in hopper 24 with those particlesy sepa.- rated from the main gas ow.

Steam iiows from the top of the drum I0 through the superheater inlet tube connections Sil-62 to the upright superheaterinlet tube` connections 84- and 86 and thence into the rst row of tubes of the superheater section l0, at the top of that bank. It then flows through the series connected tubes of this bank and into the series connected tubes of the upper partv of the bank '|I. From the tubes of this bank, the steam flows to an intermediate superheater header 92, the steam flow through the tube'banks 10 and 1| to this header being indicated by the arrows 94, 96, 98, and |00.

From the intermediate superheater S2. the steam flows through horizontally extending tubes |02 to the upright tubular sections |04which may be considered as partof the bank of tubes l5. The steam iiows through the upper parte of these tubes as indicated by the arrow |06 to the inlet header |08 for the' second. superheater Fromthat header the steam iiows'r downwardly through upright tubessuch. as ||U and |I2, and theny through thereinainer of the tubes of the bank 14, then. through the crossover tubes 4 and ||8 to the bankof tubesv 16. From the last two rows of tubes |20 and' |22 of' the bank T6, the steam iiows through the horizontally extending tubes of the bank 'I2 to the superheater outlet header |30 from which the steam is appropriately conducted to a point ot' use. Horizontally extending tubes |02 and tubes of bank I2 are at wider transverse spacing thanv tubes of bank 'Il providing lower inter-tube gasA velocities. Gas iiow equalization spaces such as-2|0, 2I2, 2|4, 2|6, 2|8, etc. arev provided rearwardly of the successive banks of superheater tubes. Gas flow conditions are also improvedby the double transverse spacing of the horizontal (wall. The lower portionsV |38 incline so asto form, with the oppositely inclined furnace bailie 22,v gas turning and dust separating space from which solids are discharged from thev furnace gases into the hopper 24. The tubes |36 are conlnected to an upper header |44 which is in turn connected to the drum 0 by other tubesld. The vlower ends of the tubes |36 are connected to the header |48.adjacent the hopper 24. It will be understood of course that all of the .furnace and gas pass walls above mentioned will have appropriate heat insulating or. refractory material associated with the wall tubes so as to close the spaces between the tubes and otherstructed similarly to the walls above indicatedV except that they do not have any inwardly bentA hOpper portions. Forv example, vthe wall'facing' the observer in Fig. 1 is formed by vertical wall tubes connected at their lower ends to the header |10 and extending upwardly past burners |12 and |14 to the horizontal upper header |16 which is joined by appropriate and water drum |0.

At the left hand side of the furnace, there is circulators to the steam indicated an outside casing' wall, orvadditio'nal wall |80 forming a space in which downcomers such as |8| are disposed. These downcomers connect the water space of the drum l0 with lower headers such as the headers |18, 20, and 2|. This outside casing may extend about thelower parts of the installation as indicated at |90. ISI,

and |92. At the upper part of the installation similar casing sections are indicated at 200, 20|, 262, and 203. y

The lower part of the furnace of the illustrative installation is increased involume and capacity by lateral extensions suchas indicated atV 230 and 232 in Fig. 2. The burners, such `as |12 and |14 may be disposed in the water tube walls of these extensions, or, when there isdownward ring, the roof of each extension may'have a group of burners extending downwardly therethrough. VSuch groups of burners are indicated at 234-231, inclusive, at the lower Ypart of'Fig. 2, and by 24U-243, inclusive, at the upper part of this figure. n f L The Yabove indicated arrangement of extensions of the lower part of the furnace also applies tothe modification indicated in Fig. 3 of the drawings, and the construction and arrangement of the furnace, superheater, and economizer of the Fig. 3 modification is also generally similar to the installation indicated in Fig. 1, the banks of economizer tubes 250--252 of Fig. 3 corresponding to the banks of tubes 50-'52-of Fig.'.'1, and the banks of superheater tubes 210-212, 214, and 216, of Fig. 3 corresponding to the banks of superheater tubes 10--12, 14 and 16 of the Fig. 1 installation. In the Fig. 3 modification, the steam and water drum 280 is located toward one side of the furnace and some of the saturated steam tubes 282, leading from the steam space of the drum 280, extend along inthe rear wall 2814 of the cavity 286, which generally corresponds to the cavity 220 of Fig. 1. These tubes 282, at the top of the gas inlet 288 for the bypass 290 have horizontally and rearwardly extending parts 292`bent out of wall formation to afford less restriction between thespace 286 at the rear of the vertical superheater bank 216, andthe bypass. Below the positioniof the tube portionsv 292,' the saturated steam tubes continue with the downwardly inclined portions 294 to connections with the inlet tubes of the bank of. superheater tubes 210, the portions 204 providing support for refractory material which completes the inclined wall at the bottom of the bypass.

The top of this wall is joined to the` upright wall 296 separating the bypass 290 from the main partof the gas pass 238.

Extending across the bypass inlet 288 are upright parts 300 of steam generating tubes, leading from headers at the lower part of the in- Y stallation and corresponding generally with parts of some of the tubes I6 of the Fig. 1 modification. The lower furnace wall parts of thesetubes are indicated at 302 in Fig. 3. Parts of these tubes extend through the dust hopper 304, these parts being indicated at 306 and 308, with the parts 306 bent out of their wall formation in the zone of the hopper. Vtending to the bypass inlet 288, appropriate refractory material is applied to the tubes to pro'- vide the wall section 3|0 separating the zone of the vertical banks 214 and 213 of superheater tubes and the upright gas pass 298.

Extending over the lower part 3|2 of the dus hopper are spaced steam generating tubes 3|.4

leading from the header 3|6 and extending along the rear upright wall 3|6 of the gas pass 298, to

the header 326 which is connected to the steam and water drum 286 by the tubes 3|5.

Some of the furnace wall tubes along the right the roof 328 over the vertical banks of superheater tubes is delineated by extensions of the wall tubes 332.

The Wall ofthe furnace 330 of the Fig. 3 installation opposite the wall tubes 302 includes furnace wall tubes 332 and refractory material 334, the wall tubes being connected to the-water space of the drurn 280. Each of the remaining walls of the furnace includes an upper header such as indicated at 340. This header has'the' corresponding parts of the tubes 282 lead first` horizontally along the roof 344 of the installation to the wall 346. Tubes 342 have parts extending downwardly through the roof 328 and theny through the cavity 266 toa position where they are bent to the right to extend through the wall 3| 6 and thereafter form parts of the bankyofsuperheater tubes 216. Steam iiows downwardly through this bank of tubes and thenthrough the next lower bank of superheater tubes l21| to the intermediate superheater header 350. .From this header steam iiows through rows of tube sections 352 and 364 to other sectionsconstituting 1.

Above this zone and exupright gas pass alongside said furnace wall, said gas pass being provided at its lower part with a gas inlet, means connecting the furnace gas outlet to said gas pass inlet, part of said wall means having its lower portion inclined oppositely and convergently relative to said furnace baille to form therewith an upper hopper through which solids deposited from the gases are caused to move convergently downwardly to a hopper outlet, means forming a second hopper below said hopper outlet and exteriorly of the furnace for the periodical removal of solids collected from the gases, and auxiliary fluid heating devices disposed across the flow of gases above said furnace baille and in said gas pass.

4. In a steam generator and superheater installation, steam generating tubesdeiining boundaries of a furnace, a steam and water drum to which said tubes are connected, means forming a heating gas passage extending horizontally from the upper part of the furnace and having rearwardly diverging top and bottom walls, an upright wall at the rear of said passage, the upright wall including some of said steam generating tubes and non-metallic heat resistant material, a superheater including a bank of vertically disposed serially connected tubes disposed transversely of gas flow in said passage and at a position spaced from said upright rear wall, said gas passage having a gas outlet between the lower end of said rear wall and the lower end of but above said bottom wall, means forming an upright gas pass for upward gas flow from said outlet, upper and lower groups of heat absorbing tubes in said upright gas pass, said upper groups of heat absorbing tubes constituting a feed water heater and including a plurality of circuits with serially connected tube portions extending horizontally from front to rear of said pass, an additional upright wall disposed rearwardly of the i'lrst mentioned upright wall and forming therewith a superheater gas by-pass, said first upright Wall at the rear of the rst mentioned gas passage having an opening therethrough constituting a gas inlet leading to the lower end of the by-pass, and damper means controlling the gas flow through the by-pass.

5. In a steam generator and superheater installation, a furnace, steam generating tubes subject to the heat of the furnace, means forming a heating gas passage leading horizontally from the upper part of the furnace and having rearwardly diverging top and bottom walls, an upright wall at the rear of said passage, the upright wall including some of said steam generating tubes, a convection superheater including a bank of vertically disposed serially connected tubes disposed transversely of gas flow in said passage and at a position spaced from said upright rear wall, said heating gas passage having a gas outlet between the lower end of said rear wall and the lower end of but above said bottom wall, means forming an upright main gas pass for upward gas iiow from said gas outlet, upper and lower groups of heat absorbing tubes in said upright main gas pass, said upper heat absorbing tubes constituting a feed water heater and including a plurality of circuits of serially connected tube portions extending horizontally across gas flow in said main gas pass, an additional upright wall disposed transversely of said upper heat absorbing tube portions and rearwardly of the nrst mentioned upright wall and combining with the latter to form therewith a superheater gas by-pass having an inlet disposed at a level above the level of the lower group of tubes and leading through the rear wall of said first passage to the lower end of the by-pass, and damper means controlling the gas flow through the by-pass, said by-pass having its major transverse dimension substantially equal to the major transverse dimension of the main pass.

6. In a steam generating superheater installation, a vertically elongated furnace including closely disposed steam generating wall tubes which generate substantially all of the steam of the installation, a superheater having a bank of vertically extending series connected tube sections disposed within the space defined by said wall tubes or extensions thereof, the furnace having a gas outlet in which the superheater is positioned, means including some of said wall tubes and forming an upright gas pass the lower end of which is connected to the gas outlet of the furnace, the superheater also including a bank of horizontally extending series connected tube sections disposed across upright gas flow in the gas pass and generally disposed at levels lower than the levels of the major parts of the vertically extending superheater tubes, wall means including heat resistant material and forming a CHARLES H, WOOLLEY.

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

UNITED STATES PATENTS Number Name Date 2,092,299 Black et al Sept. 7 1937 2,255,233 Tollow Sept. 9, 1941 2,293,040 Bailey Aug. 18, 1942

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