US2414848A - Steam generator - Google Patents

Description

J. P. BADEVNHAUS'EN 2,4M,4

STEAM GENERATOR Filed March 3, 1944 Patented Jan. 28, 1947 STEAM GENERATOR John Phillips Badenhausen, Philadelphia, Pa.

Application March 3, 1944, Serial No. 524,865

3 Claims.

This invention relates to steam generators and the following description, taken in connection more particularly to apparatus for preventing priming of the same.

Many steam generators now in use, in addition to the customary steam drum or steam and water drum, have a large lower water drum or mud drum which in many instances is of the same or even of larger diameter than the steam drum or the steam and water drum. In the operation of such steam generators, it frequently happens that the steam pressure in the steam generator, instantaneously and by reason of sudden steam demands, may drop ten or fifteen pounds. This drop in internal pressure may not even be noticeable on the pressure gage because of its rapidity cr for other reasons. In steam generators having large mud drums, the large' volume of water in the boiler tubes and in the mud drum has a high expansion potential and substantial portions of the water tend to flash into steamimmediately upon the occurrence of the pressure drop. The sudden ash into steam of the large quantity of water results in efforts of the steam contained in the water to find relief, The water and the steam released therein travel together upwardly through the tubes to the steam drum or steam and water drum, in many instances through the downcomer tubes. Considerable quantities of steam and water may be forced through the superheater without vaporization. The discharge of the water may cause considerable difficulties by carrying solids in solution or in suspension into various parts of the power plant and the water may damage the blading of the turbine.

In accordance with the present invention provision is made for reducing the amount of water which is capable of causing flash generation of steam upon reduction of pressure while maintaining adequate fluid available to feed the tubes and maintain proper circulation.

In accordance with the present invention also, provision is made for separating and segregating a considerable quantity of the water in the mud drum or water drum which is capable of contributing to the priming whereby the operation of the boiler will be greatly improved.

In accordance with the present invention also provision is made for the correction of priming difliculties in boilers now in use.

Other advantages of the invention will be ap-A parent from the annexed specification and claims.

The nature and characteristic features of the I invention will be more readily understood from with the accompanying drawing forming part hereof in which:

Figure l is a vertical central sectional view through a conventional steam generator indicating the manner of use of the present invention;

Fig. 2 is a fragmentary transverse sectional view through a mud drum showing the manner of installing the apparatus in accordance with the present invention;

Fig. 3 is a fragmentary longitudinal sectional view showing certain details of construction; and

Fig. 4 is an enlarged fragmentary longitudinal sectional view showing further details of construction,

It will, of course, be understood that the description and drawing herein are illustrative merely, and that various modifications and changes may be made in the structure disclosed without departing from the spirit of the invention.

Referring more particularly to Fig. l of the drawing a boiler IIJ of conventional type is illustrated for purposes of explanation of the invention. The boiler I0 shown is of the Stirling type,

with a chain grate Stoker I'I although it will of course be understood that the invention is not restricted to use of boilers of this specic type or fired in this manner. The boiler III illustrated preferablyincludes a lower water drum or mud drum I2, a front upper drum I3, an intermediate upper drum I4 and a rear steam and water drum I5, the drums I3, I4, and I5 being preferably arranged with their axes parallel t0 that of the lower drum I2. The lower water drum or mud drum I2 may have the usual manholes I6 at the ends thereof.

Banks of spaced steam generating riser tubes II are provided extending from the water drum or mud drum I2 to the front upper drum I3, the tubes Il being exposed to the radiant heat oi combustion.

Banks of spaced riser tubes I8 for steam generation are provided connecting the lower water drum or mud drum I2 to the central drum I4 and banks of spaced downcomer tubes I9 are provided Afor connecting the steam and water drum I5 with the lower water or mud drum I2.

The drum I3 and the drum I4 are preferably connected by a bank of tubes 2li extending there between below the water level thereof and by a bank of tubes 2| extending therebetween above `the waterv level thereof. The drum I4 is also preferably connected to the drum I5 by a bank of tubes 22 extending therebetween above the water level 3 thereof. The drum I5 has a steam delivery pipe '23 connected thereto for the discharge of the steam generated in the steam generator and for the delivery of the steam to a superheater 24, preferably mounted in the space between the bank of tubes I 'I and the bank of tubes I8.

Suitable baies and 26 are .provided for dividing the interior space into a plurality of passes and for directing the gases in heat eX- change relationship with the tubes of the bank of tubes I?, the tubes of the bank of tubes I8 and the tubes of the bank of tubes I 9. The exhaust gases of combustion are discharged through a duct 28 to an induced draft fan (not shown) for discharge to a stack (not shown).

The combustion chamber 21 may be provided with any suitable means for supplying heat for steam generation and, in the particular boiler illustrated, chain grate stoker I I is shown diagrammatically.

In accordance with the 'present invention an interior casing or shell 30 is provided and is mounted in the lower water drum or mud drum 2 for the purpose of confining the major portion of the water contained in the water drum or mud drum i?? as hereinafter pointed out. The interior casing or shell 3) is preferably cylindrical in shape and is constructed of parts capabie oi' insertn through the manholes I of the drum for assembly within the interior of the drum For this purpose a plurality of plates e. are provided, the plates SI preferably being curved in transverse cross section so as `to be substantially concentric with the drum I2 when mounted in position. These plates 3l also preferably extend from one end of the drum I2 to the other end of the drum l2 and have franges 32 at their for engagement by end cover plate members as illustrated in Fig. 3. lIhe plates are supported at suitable intervals along their length by posts iii welded or otherwise secured to the drum ifi. The posts s4 preferably have reduced end sections for the reception of the plates 3| and the reduced end sections 35 have slots .for engagement by tapered wedges or kers 3i for locking the plates SI in position. The end cover plates 33 are preferably secured to the flanges 52 of the longitudinal plate members EI in a similar manner by keys 31 extending through slots in the end members 35a.

The interior casing or shelle is preferably open at the bottom as at 3Q for access of water into the interior of the casing si! and a plurality of small openings 35 are provided in the upper plate sections 3i for the slow discharge of steam formed within the shell or interior casing 30 as hereinafter pointed out.

he manner of use of the apparatus in accordance with the present invention will now be explained. The posts 3Q are preferably mounted `in the drum I2 and the shell 33 is assembled by placing the respective plate sections 3| in position with their longitudinal side edges overlapping. The tapered Wedges or keys 31 are inserted and forced into locking engagement the end cover plates 33 are mounted and secured in position by Wedges or keys 37.

With the shell or interior casing 33 in place in the interior of the water drum or mud drum the steam generator ma;1 be operated in the customary manner for the production of steam and for the delivery therefrom through the steam main 23 to the superheater 24. The water passing, downwardly through the downcomer tubes I or otherwise supplied to the drum I2 will pass around the exterior of the shell or interior casing 30 to the lower ends of the tubes I'I and of the tubes I5. If the pressure in the steam generator drops, by reason of increased demand for steam, and even if' this pressure drop is of very short duration there is an immediate tendency of the water to ash into steam at the reduced pressure. This occurs even without the necessity for supplying additional heat lthereto from the combustion gases.

For steam at a pressure of the order of 225 pounds per square inch, the volume of a pound of steam is of the order of approximately times that of the volume of the water at the same pressure. For steam at a pressure of the order of 1200 pounds or 1400 pounds per square inch, the volume of a pound of steam is of the order of fteen times that of the volume of a pound of water at the -sarne pressure. It will thus be seen that upon the occurrence of a pressure drop even of a few pounds there is a considerable tendency of the water in all parts of the boiler to dash into steam and increase its volume. Such increase heretofore has been eiective to impel water and steam in the tubes I'I, the tubes I8, and particularly in the downcomer tubes IS, upwardly with resultant priming. The shell or interior casing B connes the major part of the water in the water drum or mud drum I2. Upon a drop in pressure the steam which tends to form within the shell or casing 30 is retained therein and is discharged or relieved at a slow rate through the openings 40 in the upper part of the shell 30. The opening 39 at the bottom is also preferably such as to prevent the rapid displacement of the water and the static head of the water outside the shell or casing 3!! tends to prevent the rapid discharge at this location. The only water available to ash into steam and pass upwardly in the steam generator is that contained in the tubes of the banks of tubes I 1, i8 and i9 and l outside the casing 30 in the water drum or mud drum I2. This quantity of water is relativel's7 small and is not sufficient to cause any priming.

I claim:

1. In a steam generator having a steam drum and a water drum and banks of tubes extending between said drums and connected thereto at their terminal ends, the combination of means for preventing priming of said steam generator, said means including an interior closed water confining casing mounted within said water drum for reducing the effective volume of water therein capable of causing priming, said casing being spaced from the walls of said water drum and from the terminal ends of said tubes for permitting the free flow of water around said casing and with respect to the terminal ends oi said tubes, said casing having end cover members for closing the ends of said casing, and said casing having a restricted water access opening at the bottom thereof for preventing the rapid discharge of water confined within said casing.

2. In a steam generator having a steam drum and a water drum and banks of tubes extending between said drums and connected thereto at their terminal ends, the combination of means for preventing priming of said steam generator, said means including an interior closed water confining casing mounted within said water drum for reducing the effective volume of water therein capable of causing priming, said casing being spaced from the walls of said water drum and from the terminal ends of said tubes for permtting the free flow of water around said casing and with respect to the terminal ends of said tubes, said casing comprising curved plate members carried by the wall of said drum and longitudinally disposed with respect thereto, and end cover members for closing the ends of said casing. and said casing having a restricted water access opening at the bottom thereof for preventing the rapid discharge of water conned within said casing.

3. In a steam generator having a steam drum and a Water drum and banks of tubes extending between said drums and connected thereto at their terminal ends, the combination of means for preventing priming of said steam generator, said means including an interior closed water conning casing mounted Within said Water drum for reducing the eiective volume of water therein capable of causing priming, said casing being spaced from the walls of said Water drum and from the terminal ends of said tubes for permitting the free flow of Water around said casing and with respect to the terminal ends of said i tubes,` said casing comprising curved plate members carried by the wall of said drum and longitudinally disposed with respect thereto, and end cover members for closing the ends of said casing, and said casing having a plurality of restricted openings at the upper part thereof for the slow discharge of steam formed within said casing and a restricted water access opening at the bottom thereof for preventing the rapid discharge of the Water conned within said casing.

JOHN PHILLIPS BADENHAUSEN.

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