US2485767A

US2485767A - Steam separator

Info

Publication number: US2485767A
Application number: US570555A
Authority: US
Inventors: Ward S Patterson
Original assignee: Combustion Engineering Superheater Inc
Current assignee: Combustion Engineering Inc
Priority date: 1944-12-30
Filing date: 1944-12-30
Publication date: 1949-10-25
Anticipated expiration: 1966-10-25

Description

Oct. 25, 1949. w s, PATTERSON 2,485,767

STEAM SEPARATOR Filed Dec. '50, 1944 2 Sheets-$heet 1 IN V EN TOR. M/ard 5. Pa zzerson Oct. 25, 1949. w. s. PATTERSON STEAM SEPARATOR 2 Sheets-Sheet 2 Filed Dec. 50, 1944 v INVENTOR.

Marc! SPazzaraon Patented Oct. 25, 1949 UNITED S TAT'ES PATENT O F-l'C-E STEAM SEPARA'IOR Ward S. Patterson, 'Chappaqua, N. Y., assignor .to Combustion Engineering-Superheater, Inc., a corporation of Delaware Application December 30, 1944, Serial No. 570,555

4 Claims. 1

This invention relates to separators and particularly to the separation of moisture from steam within .the drum of a steam boiler.

In a water-tube boiler of the natural circulation type and in some forced circulation boilers, onlypart of the water passing through the heated tubes is evaporated into steam to travel along with the water as a more or less heterogeneous mixture. The steam must then be separated from the Water, and the Water recirculated with fresh feed water through the boiler tubes. This separation must be accomplished in such an efiicient manner that the steam is practically dry or free of entrained moisture, because any moisture carried with the steam also carries with it dissolved and suspended solids, which, on evaporation of the water, become deposited on the internal surfaces of the superheaters, on turbine blades, or in valves, etc., Where it is very objectionable.

In steam generating units it has been found that up to a certain output of steam the steam is dry but if this output is exceeded the moisture in the steam increases rapidly. The maximum output at which commercially dry steam 'is obtainable is a function of the drum pressurathe steam space in the boiler drums, the character of *the boiler water and the type of boiler. In an article entitled Boiler capacity has outgrown its terminology published in Combustion of March- 1934, page 11, the chart designated Fig. 1 shows the steam liberation in cubic feet and pounds of steam per hour at various pressures for each cubic foot of steam space in the separation drum of a number of boilers. the limitations of the steaming capacities of drums at that time. It is shown that in a drum not equipped with separating devices steaming capacities generally follow a law for the settling velocities of particles of moisture falling through the steam. Since then various attempts have been made to improve those liberations by installing apparatus of various types within the drum with more or less success.

An object of this invention is to provide im- 1 proved means for the separation of moisture from steam within the steam space of a boiler drum.

' Figure 1 is a transverse sectional view through a steam and Water drum of a steam boiler showing one embodiment of the invention, as viewed on line |l of Fig. 2;

Figure 2 is a partial longitudinal section through the drum taken on line 2-2 of Fig. 1; and

Figures 3 and. 4 are transverse sections, similar This will aid in visualizing ,4

to'Fig. 1, ofother embodiments of the invention.

Figure 1 illustrates the .principal features of the device as applied to a boiler drum in which all of the steam enters the steam space above the water level. The steam and water drum I0 is provided with tube openings ll through which the steam and water mixtureis discharged from the tubes I2 into the drum. An imperforate bafile l3 opposite and close to the tube openings ll directs the mixture of steam and water downwardly through a discharge opening l4 formed by the space between bafile l3 and shell I0. The area of discharge opening I 4 is selected to give a relatively high discharge velocity. Baille I3 is positioned in downward and outward inclination to cause the discharge of the steam-water mixture in the form of a sheet directed against the drum she'll at approximately location A above the water line. The density of the water is much greater than that of the steam so that a heterogeneous mixture no longer exists because as the denser water is thrown against the drum shell the less dense steam is displaced toward the center of the drum thereby causing a primary separation of water and steam. This separation is accomplished in a very small space between discharge opening 14 and location A. To prevent depression of the water level B at a location directly below discharge opening I4 where the steam and water leaving said opening would strike the drum at high velocity, a funnel-shaped or convergent throttling throat I5 is preferably provided. This throat is Jformed by plates I6 and drum Ill. Plate T6 is preferably adjustably movable along the surface of plate ll so as to vary the size of the throat formed between the outer edge of plate l6 and drum I'll. 'By varying the size of throat l5 the amount of water flowing therethrough may be controlled. The water discharging through opening I l and separated from the steam may then pass through throat I 5 or spill over the top edge of bafile plate [7. It has been found that under certain conditions of steam pressure and density satisfactory results may be obtained by omitting plates [6 and I1 and allowing the water discharged from opening [4 to jet directly into the water within the drum and also that the screen "2'2 may be omitted. The steam and any entrained moisture not yet separated therefrom passes toward the center of the drum through the opening 1 8 between the bottom of battle I3 and the top of plate 11 -or the water level and passes into space 20 toward screens 2|. Any steam entrained with the "water and passing downwardly through the throat :l5 rises through Submerged 23 extending to drum I serves as a darn which deflects water flowing against it from above along the drum shell upwardly thereby insuring that all submerged steam in said water will pass upwardly through screen 22 into space 20. A perforate blow-01f pipe 23 is located below and adjacent to the opening between the bottom 24 of -bafile 23 and the baflle 25 which may serve as a continuous blow down. Since the water delivered by the tubes contains a relatively large concentration of solids, and is delivered from opening l4 downwardly toward and in part through the opening just above pipe 26 and since this concentrated water has not as yet been admixed with relatively pure feed water entering through pipe 25a, the location of pipe 26 is most advantageous for a blow down. Obviously the blowolf pipe 23 may also be located submerged within the water between baflle 23 and said surface against which the flow of the mixture issuing from opening l3 passes.

Screens 2| serve several purposes. They are so selected with respect to free area that they offer sufficient resistance to the flow of steam to insure a uniform distribution and uniformly low velocity of the steam within the steam space 23. Screens 2| also deliver the steam uniformly into space 30 beyond. The screens 2| also offer a relatively large contact surface that becomes wetted by the v entrained moisture remaining in the steam, thereby removing said moisture and the relatively low velocity over said screens permits the screens to drain away the moisture. The low velocity in the spaces and 3|] allows a relatively long period of time for settling out of the moisture by gravity, thereby improving the moisture separation efficiency of these spaces. The steam then passes through screens 3| which have a greater resistance than screens 20 in order to maintain a uniform distribution and low Velocity of the steam in space 30 and again to provide a large amount of contact surface for any remaining entrained moisture. The large screens 3| are inclined at a substantial angle from the horizontal to insure good drainage of the moisture from the screens and their lower ends may optionally be submerged in the water. After passing through screens 3| which function like screens 2| to uniformly distribute the steam flowing therethrough, the steam discharges into space 32 prior to passing through screens 33 and thence to steam outlet 34. Screens 33 are inclined from the horizontal and so placed that any remaining moisture extracted by them from the steam and draining down the screens will drop from their lowest edge into a zone of relatively low velocity of steam in space 32 so as not to be re-entrained. It will be noticed that after an effective primary separation in a very small space at the side of the drum where the steam and water mixture enters, the steam passes through the drum through substantially the entire available steam space with a minimum flow velocity.

The drum internals including baffles |3, I6,

I1, 23, and 25 and the screens 2|, 22, 3|, and and 33 extend continuously throughout the length of the drum between end plates 35, located beyond the last tube openings adjacent the ends of the drum. The end plates 35 form enclosures was to confine the flow of the steam to a path around the baflles and through the screens. Obviously the baffles and the various screens may be assembled in narrow sections as shown in Fig. 2, so that they may be removed through the manhole 3B of the drum.

In Figs 3 and 4 part of the steam and water mixture is discharged from tubes |2a entering the drum below the water level. Part of baflles |3a and I3!) are submerged and the entire bafile spaced from the shell to form a passage confining the mixture and leading it to the opening Me.

In Fig. 3 the mixture is discharged against drum Ill as in Fig. 1. In Fig. 4 baflle |3b confines the mixture while directing it upwardly toward a bafile |3c which in turn directs it. against the other side of baffie I31) and toward opening l5. The separation of the steam and water after leaving discharge opening |4a in both Figs 3 and 4 occurs in the same manner as it does in Fig. 1 and thereafter the steam flows toward the steam outlet 34 as described for Fig. 1.

An actual installation of the drum internals made in accordance with this invention has shown that at a steam pressure of 800 p. s. i. about 1950 pounds of steam per hour have been passed through each cu. ft. of steam space and upon leaving the drum contained less than A of 1% moisture. When compared with the 1050 pounds limit shown in Fig. 1 of the article referred to above, it shows the output to have increased to This marked increase is due to a combination of the improvement in the length of time spent by the steam within the steam space of the drum, thereby permitting more moisture to fall out, the effective primary separation within a small space of the steam and water mixture both above and below the water level where the mixture enters the drum, and the subsequent elimination of moisture by its deposit upon the relatively large surface of the several screens which also serve to equalize the flow of steam throughout the steam space. I

What I claim is:

1. In a steam separator having a drum contaming a body of water, tubes connected to discharge a mixture of steam and water at least in part above the water level, and a steam outlet; means forming a smooth surface in said drum located above the water level and remote from said outlet; baflle means mounted opposite said tubes and disposed to direct said steam and water mixture downwardly through the steam space onto said surface at an acute angle thereto; means forming a funnel shaped throat below said surface and extending to a point under the water level; submerged bafile means ofiset toward the center of said drum with respect to said funnel and extending upwardly from adjacent the bottom of said drum toward the water level; a submerged screen extending from the throat of said funnel to adjacent upper end of said second baffle means; a second screen extending through the steam space to a point below the water level dividing it into separate chambers; and other steam separating means mounted intermediate and above said second, screen and the steam ofitalse.

2. In a steam separator having a drum containing a body of water, tubes connected to discharge a mixture of steam and water at least in part above the water level, and a steam outlet; means forming a smooth surface in said drum located above the water level and remote from said outlet; baffie means mounted opposite said tubes and disposed to direct said steam and water mixture downwardly through the steam space onto the surface of the inner wall of said drum at an acute angle thereto in a location adjacent said tubes and above the water level; means forming a funnel shaped throat below said surface and extending to a point under the water level; submerged baffle means offset toward the center of said drum with respect to said funnel and extending upwardly from adjacent the bottom of said drum toward the water level; a submerged screen extending from the throat of said funnel to adjacent upper end of said second baffle means; a second screen extending from said first baflle means through the steam space to a point below the water level; and other steam separating means mounted intermediate and above said second screen and the steam ofitake.

3. In a steam separator having a drum containing a body of water, tubes connected to discharge a mixture of steam and water at least in part above the water level, and a steam outlet; means forming a smooth surface in said drum located above the water level and extending therebelow and remote from said outlet; baffle means mounted opposite said tubes and disposed to direct said steam and Water mixture downwardly through the steam space onto said v surface at an acute angle thereto; submerged baffle means ofl'set toward the center of said drum with respect to said surface spaced from the bottom of said drum and extending upwardly toward the water level; a screen extending through the steam space to a point below the water level dividing it into separate chambers;

and other steam separating means mounted intermediate said second screen and the steam ofitake.

4. In a steam separator having a drum containing a body of water, tubes connected to discharge a mixture of steam and Water at least in part above the water level, and a steam outlet; means forming a smooth surface in said drum located above the water level and extending therebelow and remote from said outlet; baffie means mounted opposite said tubes and disposed to direct said steam and water mixture downwardly through the steam space onto said surface at an acute angle thereto; submerged baflle means offset toward the center of said drum with respect to said surface spaced from the bottom of said drum and extending upwardly toward the water level; a screen extending through the steam space to a point below the water level dividing it into separate chambers; other steam separating means mounted intermediate said second screen and the steam ofitake; a submerged feed water inlet located beyond said second mentioned baffle with respect to said surface; and a blow-off pipe submerged within the water between said surface and said second mentioned bafile means.

WARD S. PATTERSON.

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

UNITED STATES PATENTS Number Name Date 1,946,248 Weigel Feb. 6, 1934 2,091,421 Sherman Aug. 31, 1937 2,232,256 Place Feb. 18, 1941 2,298,287 Frisch Oct. 13, 1942 2,346,672 Fletcher Apr. 18, 1944 2,378,862 Place June 19, 1945