US3435598A

US3435598A - Vapor and liquid drum including cyclone separator

Info

Publication number: US3435598A
Application number: US360665A
Authority: US
Inventors: Earl E Coulter; Lowell E Johnson; Thomas M Modrak
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1964-04-17
Filing date: 1964-04-17
Publication date: 1969-04-01
Anticipated expiration: 1986-04-01
Also published as: NO115030B; DK114490B; NL6504754A; SE314084B; GB1100845A

Description

J .April 1,1969 ETAL 7 3,435,598 7 VAPOR AND LIQUID DRUM INCLUDING CYCLONE SE PARATOR Filed April 1'7, 1964 Shet of :s

'INVENTORS Earl E. Couher Lowell E.Johnson Thom M. Modrak .v ATTORNEY p 1969 E. E. COULTER ETAL 3,435,598

VAPOR AND LIQUID DRUM INCLUDING CYCLONE SEPARATOR United States Patent 3,435,598 VAPOR AND LIQUID DRUM INCLUDING CYCLONE SEPARATOR Earl E. Coulter, Akron, and Lowell E. Johnson and Thomas M. Modrak, Alliance, Ohio, assignors to The Babcock & Wilcox Company, New York, N.Y., a corporation of New Jersey Filed Apr. 17, 1964, Ser. No. 360,665 Int. Cl. F22b 37/32; B04c /04; B01d 47/02 US. Cl. 55-424 6 Claims This invention relates in general to the construction and operation of apparatus for separating liquids from gases and more particularly to separating apparatus adapted for use in the steam space of a steam and water drum of a marine type steam generating unit for the removal of suspended moisture and solids from the outgoing steam.

The importance in steam generation of providing clean dry steam has long been recognized, but as the operating pressure and capacities of steam generators have markedly increased, the need for removal of moisture and impurities from the steam to a greater degree has become more important to avoid harmful deposits in the associated superheater and/or turbine. This is particularly true where the circulating water of the steam generator contains a high concentration of solids introduced for the purpose of preventing internal corrosion of the pressure parts. Small particles of the solid material are present in the moisture carried by the steam entering the boiler steam and water drum, and unless removed from the steam before its exit from the drum, would deposit in the superheater and/ or associated turbine, thereby increasing outage and maintenance of this equipment and lowering turbine efficiency and output.

The production of steam that is free from boiler water and its attendant solids is usually more difficult to attain in marine practice than in stationary practice, for the problem of swelling of the Water is more accentuated in the former owing to the fact that a marine type steam generator is subject to ship pitch and roll and is more subject to sudden changes in load. Swelling of the water affects the water level extensively and can produce priming, that is, the discharge from the steam and water drum to the superheater of steam containing quantities of water in suspension.

Thus the general object of the present invention is the provision of steam and water separating equipment possessing the virtues of compactness, simplicity, reliability and ability to provide steam that is free from boiler water and its attendant solids under the most severe drum water swelling conditions that can be anticipated. The steam and water separating apparatus of the invention is further characterized by its ready accessibility for inspection, maintenance and repair; its ability to be removed quickly for access to tubes connected to the steam and water drum; and its capacity to deliver steam-free water to the downcomers of the circulation circuits, thereby providing optimum circulation head.

In accordance with the invention, the steam and water drum of a steam generator is provided with steam and water separating apparatus comprising a substantially cylindrical horizontally arranged whirl chamber and a separated water discharge conduit having its inlet end connected to the circumferential wall of and opening to and extending along substantially the entire length of the whirl chamber and its outlet end opening into the Water space of the steam-water drum, with each end of the whirl chamber being formed with a separated steam outlet opening to the vapor space of the drum, and with a perforated plate covering the inlet end of the separated water discharge conduit. Provisions are made for passing ICC steam-water mixtures generated in the riser circuits of the steam generator tangentially into the whirl chamber along substantially the entire length thereof and effecting a whirling path of steam-water travel therein along the circumferential Wall of the whirl chamber at a velocity suflicient to centrifulgally separate the steam from the water and to cause almost all of the separated water to discharge through the perforated plate and water discharge conduit into the water space of the drum. Separated steam is directed axially of the whirl chamber through the steam outlets thereof to the vapor space, and then through corrugated scrubber plates before it passes to the superheater and turbine.

The various features of novelty which characterize our invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which we have illustrated and described a preferred embodiment of the invention.

Of the drawings:

FIG. 1 is a vertical section of increased scale along line 11 of FIG. 2 of a steam and water drum of a steam generator incorporating steam and water separating apparatus'constructed in accordance with the invention;

FIG. 2 is a plan section of reduced scale taken along line 2-2 of FIG. 1;

FIG. 3 is a vertical section of reduced scale taken along line 3--3 of FIG. 1;

FIG. 4 is an enlargement of one of the steam and Water separating devices of FIG. 1; and

FIG. 5 is a front view of the separator of FIG. 4.

In the construction illustrated in the drawings, the steam and water separating equipment of the invention is disposed in a horizontally arranged steam and water drum 10 of a steam generating unit having a normal water level slightly below the centerline of the drum separating an upper steam space 12 from a lower water space 14. Feedwater enters the water space of the drum by way of a perforated pipe 16 then flows downwardly through downcomer tubes 18 to the riser circuits of the unit. Steam and water mixtures generated in the riser circuits pass through riser tubes 20, only a few of which are illustrated, connected to the drum along the length thereof for discharge to a water-tight inlet compartment 22 extending longitudinally of the drum to positions spaced from the ends thereof and circumferentially along the lower portion of the drum from a position on one side of the drum above the horizontal centerline thereof to the corresponding position on the opposite side of the drum. Compartment 22 is formed in most part by a series of curved plates 24 inwardly spaced from the inner drum wall and supported by brackets 26 secured to the drum wall, with opposite ends of compartment 22 being closed by plates 28 extending between and secured to the drum wall and plates 24.

In accordance with the invention, drum 10 is provided with two rows of steam and water separator 32 disposed along the length and at opposite sides of the drum and in most part within the steam space 12. Each separator comprises a substantially cylindrical horizontally disposed chamber 34 arranged in steam space 12 with its longitudinal axis extending parallel to the longitudinal axis of drum 10 and having its circumferential boundary wall formed by a plate 36 and its opposite ends partly closed by plates 38, with each plate 38 having a circular throat 40 arranged eccentrically of and projecting into chamber 34 and forming a separated steam outlet 42 opening to steam space 12. Cylindrical chambers 34 of each row are coaxially arranged, with their corresponding steam outlets 42 also being coaxially aligned. Each outlet 42 is so eccentrically arranged relative to its corresponding chamber that its horizontal axis is disposed slightly below the corresponding axis of the chamber and its vertical axis is spaced a short distance from the corresponding axis of the chamber in the direction of the vertical center-line of the drum. Each separator is provided with a fluid supply duct 44 of substantially rectangular cross-sectional area having its inlet end opening to and forming a part of compartment 22 and it discharge end opening tangentially into corresponding chamber 34 along the entire length and on the drum wall side of the chamber at about the level of the horizontal axis of the chamber. Each duct 44 is so arranged relative to each of the outlets 42 of the corresponding chamber that a line drawn through the center of each outlet 42 and the center of the corresponding end wall 38 will make an angle of approximately 45 with the tangential side of duct 44. Ducts 44 of each row are formed in part by a metal plate 46 extending along the length of the drum, having its lower end connected to adjacent plate 24 to form an extension of compartment 22, and having its upper portion terminating in most part at and connected to the circumferential wall of each chamber 34. Since each duct 44 is essentially an extension of compartment 22 there is very little dissipation of the velocity head energy of the steam-water mixtures as they pass through compartment 22 to chambers 34.

Separated water is discharged from each chamber 34 by way of a corresponding duct or conduit 48 having its discharge end opening into the water space 14 at about the level of feed pipe 16 and its inlet end connected to the circumferential wall of the chamber and opening to the bottom and extending along the entire length of the chamber, with each duct 48 having an upper portion 48A of gradually decreasing rectangular cross-section in the direction of flow and a lower portion 483 of uniform rectangular cross-section. Each duct 48 should be long enough to reach below the minimum expected drum water level to assure that its discharge end will not be exposed under any operating condition. The inlet end of each duct 48 is covered by a plate 50 connected to and forming a part of the circumferential wall of the corresponding chamber 34, and provided with staggered rows of circular holes throughout its extent for passage of separated water to the corresponding duct 48.

The thickness of the steam-water mixture tream whirling along the circumferential wall of each chamber 3'4 is not uniform. A large percentage of the volume of the steam-water mixture entering each chamber 3'4 is occupied by steam. As the steam is separated the volume of the mixture, and therefore the thickness, is reduced until only solid water and a minimum stream thickness is produced just ahead of the corresponding perforated plate 50. Hence the vortex formed inside of each chamber 34 is not concentric with the chamber. Thus while the steam outlets 42 are eccentrically located relative to corresponding chamber 3 4, they are substantially concentrically located relative to the vortex formed by the high velocity whirling mixture to reduce the separator pressure drop and to minimize the entrainment of water with the separated steam discharging through outlets 42 to the steam space of the drum.

Separated steam discharging from the separators in each row is directed upwardly by U-shaped guide devices 54 associated with outlets 42 and comprising upwardly inclined plates or legs 52 extending between next adjacent chambers 34 tangentially to the bottom of the corresponding outlets 42 thereof and weld-united to the end walls of the corresponding chambers. Troughs 56 are disposed between next adjacent chambers 34 and clamped to the upper ends of plates 52 and to the circumferential walls of the corresponding chambers, thus forming extensions of plates 52. The cross portion of each flow guide device 54 comprises a plate 58 so shaped as to extend outside of and along the circumferential and end walls of each chamber of the corresponding separator row in sealing relation therewith and to provide leg portions 58A disposed between next adjacent chambers 34 and extending tangentially to the bottom of the corresponding out-lets 42 thereof, with leg portions 58A being integrally connected to the lower ends of plates 52. A plate 60 constitutes the other leg of each of the guide devices 54, extends along the length of the drum generally parallel to plates 52, and has its upper end secured by clamps to the drum wall in sealing relation therewith and its lower end integrally connected to plate 58. Guide devices of the character above-described are also associated with outlets 42 at the extremities of each separator row.

Guide devices 54 permit a large leeway in drum water level above normal without carry-over and also prevent the high velocity separated steam from impinging on the drum water surface as it passes upwardly from outlets 42.

Plate 46 of each separator row is formed with upper extensions 46A weld-united to the end walls 38 of chambers 34 and to the leg portions 58A of plate 58, with end plates 62 weld-united to

corresponding plates

46, 58 and 60 and forming continuations of plates 28. Thus in each row of separators,

plates

46, 58, 60 and 62 cooperate with the drum wall and the peripheral walls of the chambers 34 to form an upper closure for and extension of compartment 22.

Perforated plates 64 are arranged across the path of the separated steam discharging from troughs 56, extend along the length of the drum, and are inclined downwardly in the direction of the center of the drum. Each plate 64 projects over and adjacent to the troughs 56 of the corresponding separator row and is suitably supported by brackets 66 connected to the drum wall. Plates 64 serve to even out along the length of the drum the flow distribution of the steam discharging from the separators, to intercept entrained moisture in the separated steam, and to limit the size of droplets that can reach the secondary scrubber equipment.

Beyond plates 64, separated steam passes upwardly through a secondary steam scrubber section 68, and thence through a steam outlet 70 to the superheater, not shown, of the steam generator. Scrubber section 68 is formed by a series of closely spaced corrugated sheet metal plates arranged side by side in vertical planes parallel to the general direction of steam flow to define a series of narrow undulating flow channels.

In the operation of the steam and water separating equipment above described, the steam-water mixtures generated in the riser circuits and collected in compartment 22 pass tangentially into chambers 34 by way of ducts 44. Each duct 44 is proportioned and arranged to provide a fluid inlet velocity over the required load range of a magnitude sufficient to establish a vortex within the corresponding chamber 34, to cause centrifugal separation of the water from the steam and the discharge of almost all of the separated water through corresponding perforated plate 50 and conduit 48, and to cause recirculation of the remaining separated water within the chamber. In each chamber the steam and water densit relation in conjunction with the kinetic energy of the steam-water mixture produce a strong vortex so that a separating force, many times greater than gravity, is set up. Separated steam, collecting in the central portion of each chamber, discharges axially through corresponding outlets 42, then is directed upwardly by flow guide devices 54 to and through perforated plates 64, and then passes through scrubber section 68 for removal of the last traces of moisture before discharging from the drum by way of outlet 70. Meanwhile, the heavier water, thrown outwards by centrifugal force, moves downwards in each whirl chamber 34 along the circumferential wall thereof and is forced out through corresponding perforated plate 50 and duct 48 to the water space 14 of the drum for return through the downcomers to the riser circuits.

Each plate 50 is proportioned and arranged to provide a pressure drop of a magnitude suflicient to assure the maintenance of a water film over the upstream surface of the plate. This film forms a seal for the prevention of carry-under, i.e., entrainment of steam with the separated water discharging to the water space 14, which, if carried into the downcomers 18, reduces the force available to produce circulation. Thus, a certain amount of water is continually recirculated within each chamber 34. If water flow increases, the thickness of the water film will increase. This will result in an increase in the centrifugal pressure and in the amount of water forced out through perforated plate 50 of each chamber until an equilibrium condition is again reached at which substantially all the water entering each chamber 34 is being discharged. So, in effect, separators 32 are self-compensating with respect to water loading. This feature of the invention permits satisfactory operation over a wide range of loads.

Perforated plate 50 of each chamber 34 also prevents any disturbance in the corresponding water discharge duct 48 from affecting the operation of the chamber. Once separated water has been discharged from the chamber, perforated plate 50 acts as a barrier to backfiow. Since substantially all of the steam is separated within the chambers 34 and there is always a water film over perforated plate 50, there is little or no steam carryunder. Therefore, the separated water can be discharged into the water space 14 well below the drum water level where it does not cause any disturbance of the drum water surface. This is important, for experience indicates that drum water surface disturbances can be a source of carry-over of moisture in the steam leaving the drum.

By way of example and not of limitation, we have found that highly effective separation is attained with each separator formed by 14 gauge plate and having a whirl chamber 34 of 9" ID. and 7" long, 4%" ID. outlets 42, a fluid supply duct 44 having a discharge end measuring 1%" x 7", and a separated water duct 48 having an inlet extending along an arc of about 45 at the bottom of the chamber, with a plate 50 of 20 gauge plate having rows of side staggered 6" diameter holes arranged to provide 51 percent open area.

What is claimed is:

1. In a steam and water drum normally having a water level separating a steam space from a water space and containing means forming an inlet compartment arranged to receive water-steam mixtures, a water-steam separator in said drum comprising means forming a substantially cylindrical horizontally arranged whirl chamber, means forming a separated water discharge conduit having an inlet end connected to the circumferential wall of the whirl chamber and opening to and extending along the length thereof and an outlet end opening to said water space at a position beneath the water level of the drum, said conduit constituting the only outlet for discharge of separated water from the whirl chamber, a perforated plate covering the inlet end of said conduit, means for passing the water-steam mixtures from said compartment tangentially into said whirl chamber along the length thereof and effecting a whirling path of water-steam travel therein along the circumferential wall of said chamber at a velocity sufficient to centrifu-gally separate the steam from the water, to cause most of the separated water to discharge through said perforated plate and conduit into the water space and to cause recirculation of the remainder of the separated water in the whirling path, said perforated plate being proportioned and arranged to provide a pressure drop of a magnitude sutficient to assure the maintenance of a water film over said plate to inhibit carry-under of steam to said water space, and means forming an outlet for separated steam arranged at one end of said whirl chamber and opening to said steam space.

2. In a steam and water drum nonmally having a water level separating a steam space from a water space and containing means forming an inlet compartment arranged to receive water-steam mixtures, a water-steam separator in said drum comprising means forming a substantially cylindrical horizontally arranged whirl chamber, means forming a separated water discharge conduit having an inlet end connected to the circumferential wall of the whirl chamber and opening to the bottom and extending along the length thereof and an outlet end opening to said water space at a position beneath the water level of the drum, said conduit constituting the only outlet for discharge of separated water from the whirl chamber, a perforated plate covering the inlet end of said conduit, means for passing the water-steam mixtures from said compartment tangentially into said whirl chamber along the length thereof and effecting a whirling path of water-steam travel therein along the circumferential wall of said chamber at a velocity sufficient to centrifugally separate the steam from the water, to cause most of the separated water to discharge through said perforated plate and conduit into the water space. and to cause recirculation of the remainder of the separated water in the whirling path, said perforated plate being proportioned and arranged to provide a pressure drop of a magnitude sufficient to assure the maintenance of a water film over said plate to inhibit carryunder of steam to said water space, and an inwardly projecting throat forming an outlet for separated steam eccentrically arranged at each end of said whirl chamber and opening to said steam space.

3. In a steam and water drum norm-ally having a water level separating a steam space from a water space and containing means forming an inlet compartment arranged to receive water-steam mixtures, a water-steam separator in said drum comprising means forming a substantially cylindrical horizontally arranged whirl chamber, means forming a separated water discharge conduit having an inlet end connected to the circumferential wall of the whirl chamber and opening to and extending along substantially the entire length thereof and an outlet end opening to said water space at a position beneath the water level of the drum, said conduit constituting the only outlet for discharge of separated water from the whirl chamber, a perforated plate covering the inlet end of said conduit, means for passing the water-steam mixtures from said compartment tangentially into said whirl chamber along substantially the entire length thereof and effecting a whirling path of water-steam travel therein along the circumferential wall of said chamber at a velocity sufiicient to centrifugally separate the steam from the water, to cause most of the separated water to discharge through said perforated plate and conduit into the water space and to cause recirculation of the remainder of the separated water in the whirling path, said perforated plate being proportioned and arranged to provide a pressure drop of a magnitude sutficient to assure the maintenance of a water film over said plate to inhibit carry-under of steam to said water space, and an inwardly projecting throat forming an outlet for separated steam eccentrically arranged at one end of said whirl chamber and opening to said steam space.

4. In a steam and water drum normally having a water level separating a steam space from a water space and containing means forming an inlet compartment arranged to receive water-steam mixtures, a Water-steam separator in said drum comprising means forming a substantially cylindrical horizontally arranged whirl chamber, means forming a separated water discharge conduit having an inlet end connected to the circumferential wall of the whirl chamber and opening to and extending along substantially the entire length thereof and an outlet end opening to said Water space at a position beneath the water level of the drum, said conduit constituting the only outlet for discharge of separated water from the whirl chamber, a

perforated plate covering the inlet end of said conduit, means for passing the water-steam mixtures from said compartment tangentially into said Whirl chamber along substantially the entire length thereof at a position to one side of and adjacent to and angularly spaced from the inlet opening of said conduit and effecting a whirling path of water-steam travel therein along the circumferential wall of said chamber at a velocity suflicient to centrifugally separate the steam from the water, to cause most of the separated water to discharge through said perforated plate and conduit into the water space and to cause recirculation of the remainder of the separated water in the whirling path, said perforated plate being proportioned and arranged to provide a pressure drop of a magnitude sufficient to assure the maintenance of a water film over said plate to inhibit carry-under of steam to said water space, and an inwardly projecting throat forming an outlet for separated steam eccentrically arranged at each end of said whirl chamber and opening to said steam space.

S. In a steam and water drum normally having a water level separating a steam space from a water space and containing means forming an inlet compartment arranged to receive water-steam mixtures, a Water-steam separator in said drum comprising means forming a substantially cylindrical horizontally arranged whirl chamber, means forming a separated water discharge conduit having an inlet end connected to the circumferential wall of the whirl chamber and opening to and extending along substantially the entire length thereof and an outlet end opening to said water space at a position beneath the water level of the drum, said conduit constituting the only outlet for discharge of separated water from the whirl chamber, a perforated plate covering the inlet end of said conduit, means for passing the water-steam mixtures from said compartment tangentially into said whirl chamber along substantially the entire length thereof at a position to one side of and adjacent to and angularly spaced from the inlet opening of said conduit and effecting a whirling path of water-steam travel therein along the circumferential wall of said chamber at a velocity sufficient to centrifugally separate the steam from the water, to cause most of the separated water to discharge through said perforated plate and conduit into the water space and to cause recirculation of the remainder of the separated water in the whirling path, said perforated plate being proportioned and arranged to provide a pressure drop of a magnitude sufficient to assure the maintenance of a water film over said plate to inhibit carry-under of steam to said water space, an inwardly projecting throat forming an outlet for separated steam eccentrically arranged at each end of said Whirl chamber and opening to said steam space, and a U-shaped guide device associated with each steam outlet for positively directing the separated steam to the upper portion of the drum.

6. In a steam and water drum normally having a water level separating a steam space from a water space and containing means forming an inlet compartment arranged to receive water-steam mixtures, a water-steam separator in said drum comprising means forming a substantially cylindrical horizontally arranged whirl chamber, means forming a separated water discharge conduit having an inlet end connected to the circumferential wall of the whirl chamber and opening to and extending along substantially the entire length thereof and an outlet end opening to said water space at a position beneath the water level of the drum, said conduit constituting the only outlet for discharge of separated water from the whirl chamber, a perforated plate covering the inlet end of said conduit, means for passing the water-steam mixtures from said compartment tangentially into said whirl chamber along substantially the entire length thereof at a position to one side of and adjacent to and angularly spaced from the inlet opening of said conduit and effecting a whirling path of water-steam travel therein along the circumferential wall of said chamber at a velocity suflicient to centrifugally separate the steam from the water, to cause most of the separated water to discharge through said perforated plate and conduit into the water space and to cause recirculation of the remainder of the separated water in the whirling path, said perforated plate being proportioned and arranged to provide a pressure drop of a magnitude suflicient to assure. the maintenance of a water film over said plate to inhibit carry-under of steam to said water space, the inlet end of said conduit being so constructed and arranged relative to the whirl chamber that the separated water makes a sharp change in direction of flow as it passes from the chamber to the conduit, and an inwardly projecting throat forming an outlet for separated steam eccentrically arranged at one end of said whirl chamber and opening to said steam space.

References Cited UNITED STATES PATENTS 2,232,265 2/1941 Place 2,763,245 9/ 1956 Place 55-396 2,782,772 2/ 1957 Blaser 55459 2,895,566 7/1959 'Coulter 55 3,022,859 2/ 1962 Sexton 5'5-90 3,165,387 1/1965 Place 55 FOREIGN PATENTS 534,305 12/1956 Canada.

FRANK W. LUTTER, Primary Examiner.

BERNARD NOZIOK, Assistant Examiner.

Claims

1. IN A STREAM AND WATER DRUM NORMALLY HAVING A WATER LEVEL SEPARATING A STEAM SPACE FROMA WATER SPACE AND CONTAINING MEANS FORMING AN INLET COMPARTMENT ARRANGED TO RECIEVE WATER-STEAM MIXTURESS, A WATER-STEAM SEPARATOR IN SAID DRUM COMPRISING MEANS FORMING A SUBSTANTIALLY CYLINDRICAL HORIZONTALLY ARRANGED WHIRL CHAMBER, MEANS FORMING A SEPARATED WATER DISCHARGE CONDUIT HAVING AN INLET END CONNECTED TO THE CIRCUMFERENTIAL WALL OF THE WHIRL CHAMBER AND OPENING TO AND EXTENDING ALONG THE LENGTH THEREOF AN AN OUTLET END OPENING TO SAID WATER SPACE AT A POSITION BENEATH THE WATER LEVEL OF THE DRUM, SAID CONDUIT CONSTITUTING THE ONLY OUTLET FOR DISHCARGE OF SEPARATED WATER FROM THE WHIRL CHAMBER, A PERFORATED PLATE COVERING THE INLET END OF SAID CONDUIT, MEANS FOR PASSING THE WATER-STEAM MIXTURES FROM SAID COMPARTMENT TANGENTIALLY INTO SAID WHIRL CHAMBER ALONG THE LENGTH THEREOF AND EFFECTING A WHIRLING PATH OF WATER-STEAM TRAVEL THEREIN ALONG THE CIRCUMFERENTIAL WALL OF SAID CHAMBER AT A VELOCITY SUFFICIENT TO CENTRIFUGALLY SEPARATE THE STEAM FROM THE WATER, TO CAUSE MOST OF THE SEPARATED WATER TO DISCHARGE THROUGH SAID PERFORATED PLATE AND CONDUIT INTO THE WATER SPACE AND TO CAUSE RECIRCULATION OF THE REMAINDER OF THE SEPARATED WATER IN THE WHIRLING PATH, SAID PERFORATED PLATE BEING PROPORTIONED AND ARRANGED TO PROVIDE A PRESSSURE DROP OF A MAGNITUDE SUFFICIENT TO ASSURE THE MAINTENANCE OF A WATER FILM OVER SAID PLATE TO INHIBIT CARRY-UNDER OF STEAM TO SAID WATER SPACE, AND MEANS FORMING AN OUTLET FOR SEPARATED STEAM ARRANGED AT ONE END OF SAID WHIRL CHAMBER AND OPENING TO SAID STEAM SPACE.