US2877747A - Liquid-vapor separating drum - Google Patents

Description

.1. Jf'HAPPELL LIQUID-VAPOR SEPARATING DRUM March 17, 1959 3 Sheets-Sheet 1 Filed Aug. 19, 1955 ATTORNEY March 17, 1959 HAPPELL 2,877,747

. LIQUID-VAPOR SEPARATING DRUM Filed Aug. 19, 1955 3 Sheets-Sheet 2 INVENTOR. John J. Happell ATTORNEY March 17, 1959 J. J. HAPPELL I LIQUID-VAPOR .SEPARATING DRUM 3 Sheets-Sheet 3 Filed Aug. 19, 1955 FIG. 7

F I G. 6

' Iolnilllliltlln71:11?!

INVENTOR. John J. Happeli l I rlllllll/ IHI - m1 1 v V v 1 w 4 a FIG.5

ATTORNEY United. Saes Patent 2,877,747 LIQUID-VAPOR SEPARATING DRUM John J. Happell, Oak Ridge, Tenn, assignor to The Babcock & Wilcox Company, New York, N. Y., a corporation of New Jersey Application August 19, D55, Serial No. 529,520

8 Claims. (Cl. 122-435) The present invention relates in general to an improvement in a vapor-liquid separating drum, and more specifically, it relates to an improved feed water heating ar rangement within the drum.

In some modern vapor generating units, it is essential that the vapor separating drum be disposed at a remote position relative to the heat exchange portion of the vapor generator. An example of this type of vapor generator is shown in the copending application of Davies et al., Serial No. 428,038, filed May 6, 1954. It is a characteristic of these vapor generators that the ratio of liquid circulated to vapor entering the separator is low, i. e. of the order of one to four, and that the ratio is lowest at the highest load of the unit. It is a further characteristic of this type of vapor generating unit that it is subject to rapid change of vapor demand requirements. Such rapid load changes result in widely varying liquid level within the separating drum, and this creates severe structural problems.

One of the greatest problems in vapor generators of this type arises when the unit is operating at its maximum load. At this time the ratio of liquid to vapor in the system is lowest, where, upon a rapid reduction to a low load, there occurs a very rapid reduction in liquid level. This lowering of the level occurs because the large volume heat exchanger is filled with the vapor being generated" but upon reduction of load, the vapor generation rate is small. This sudden reduction in vapor production rate causes the exchanger to become filled with liquid flowing from the drum and reducing the liquid level therein. Under these conditions the liquid level might disappear out of the drum. During this period, however, the feed liquid for the vapor generator is being sent into the drum and if special provisions are not made, the cool feed liquid would come in contact with the heavy walls of the drum thus subjecting the walls to a severe temperature change with the resultant large thermal stress. Thus the rapid liquid level reduction creates an operating problem which, if not recognized and properly accounted for, would destroy or at least reduce the service life of the vaporliquid drum.

The present invention is directed to a vapor-liquid separating drum which has a normal liquid level separating a vapor space from a liquid space and with the liquid level subject to substantial decreases in elevation during the operation of the drum. Within the drum there is a feed liquid inlet arranged to discharge feed liquid at a level below the normal liquid level. There is a vaporliquid contacting means arranged to receive feed liquid and to bring the liquid into direct heat transfer relationship with vapor in the drum when the liquid level is below the discharge level of the liquid inlet. The vaporliquid contacting means comprises a number of obtuse angled conical trays vertically arranged one below the other with each tray having an inclination of its bottom portion oppositely inclined from the adjacent tray and 2,877,747 Patented Mar. 17, 1959- path during the heating process. Further, there is provided baflie means for limiting the travel of the cool feed liquid to prevent the liquid from contacting the walls of the drum during the feed liquids initial period in the drum.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification, but 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 there is illustrated and described a preferred embodiment of the invention.

' Of the drawings:

Fig. 1 is a vertical section of a vapor-liquid drum embodying the present invention;

Fig. 2 is a top view of the drum of Fig. 1; Fig. 3 is a plan section taken on the line 3--3 of Fig. 1; Fig. 4 is a plan section taken on the line 4-4 of Fig. 1; Fig. 5 is a vertical section of the vapor contacting means;

Fig. 6 is a plan section taken on the line 6-6 of Fig. 5; and Fig. 7 is a plan section taken on the line 7-7 of Fig. 5. A vapor-liquid drum It) is vertically elongated having the straight cylindrical section 12, the upper head 14 and the lower hemispherical section 16 defining a volume in which there is a normal liquid level 18 separating the upper vapor space 20 from the lower liquid space 22.

The drum is arranged to be fed a vapor-liquid mixture by the inlet nozzles 24, with the vapor-liquid entering an inlet chamber 25 within the drum defined by the annular baffle 26 which is spaced from the cylindrical wall 12 of the drum 10 and with the inlet chamber being further defined by the top and bottom baflies 28 and 30. A plurality of cyclone type vapor-liquid separators 32 are disposed in a circle about the circumference of the drum and arranged to have their tangential inlets 34 receive the vapor-liquid mixture from the inlet chamber 25. Each' of the separators 32 causes the vapor-liquid mixture to whirl at high velocity, thus allowing centrifugal force to separate the light vapor from the heavier liquid. This separation is enhanced by the skimming bafiles 36. The liquid passes down the separator and out the radially inward directed outlets .38 into the liquid portion 22 of the drum. The separated liquid then mixes with the saturated liquid in the drum with the mixture passing through a vortex eliminator 40 and down the downcomer 42.

The separated vapor passes out through the top of they cyclones into the vapor space 20 during which travel the vapor is scrubbed in a multiple plate corrugated-type scrubber element 44, and is further scrubbed by passing through perforated plates 46. The scrubbed dry vapor thenleaves the drum by the outlet 48.

The drum is arranged with a combination vent and pressure indicator connection 50 at the top of the drum, two safety valve outlets 52, an inspection manhole fitting 54, and a blowdown pipe 56.

Feed liquid enters the drum through the nozzle 58 and the inlet pipe 60 which is arranged as a thermal sleeve in the inlet portion and which has upright end portion 62 positioned longitudinally on the central axis of the drum. The discharge end 63 of the feed pipe points upwardly in thedrum. Disposed on the end portion of the feed pipe is a liquid-vapor contacting or direct heat exchanger tion to cause the cascading feed liquid to take a zig zag means 64 comprising a plurality of vertically arranged obtuse angled conical perforated trays arranged one below the other. Each of the trays is oppositely inclined relative to the adjacent tray and each tray is arranged so' that its greatest perforated area is in its lowermost part. For example, the downwardly inclined tray 66 of Fig. 6

has the perforations near its outer periphery while the upwardly inclined tray 68 of Fig. 7 has the greatest area of perforations near its inner periphery. There is a downwardly directed bafile on the discharge end of the feed pipe comprising a cylindrical wall 70 and a cap or flat end portion 72 into which the feed liquid discharges and turns 180 degrees to fall onto the tray 66. This baffle prevents the feed liquid from passing up between the separators 32 into the vapor space 20. v

The discharge end 63 of the pipe 62 is some distance below the water level 13 so that when the liquid level is normal the cool feed liquid will be merely dispersed in the saturated liquid of the liquid space 32. However, when the level is substantially decreased the vapor-liquid contacting means is exposed to the vapor of the drum and during such periods the construction of the vapor liquid contacting means insures that the feed liquid will be broken up into a multiplicity of small diameter streams which take a zig zag course passing through the alternately inclined perforated trays. Thus large areas of the cool liquid are exposed to vapor with the resultant heating of the liquid and condensation of vapor.

A cylindrical baffle 74 which is longitudinally disposed of the drum and substantially tangent to the inner portions of separators 32, prevents the lateral movement of the feed liquid to eliminate the cool feed liquid from contacting the drum wall.

During the initial period when the cool liquid is inthe drum and being heated either by the vapor when the level is low or by the saturated liquid when the level is normal, thermal shield baffle 76 protects the entire hemispherical end 16 from thermal shocks due to the cool incoming liquid feed. This bafile 76 consists of thin plate which is spaced from the lower portions of the drum wall and is secured in place in such a way as to increase the thermal resistance adjacent the wall end to prevent rapid temperature changes of the wall to reduce the thermal stress therein.

The present invention thus involves means for preventing thermal shock on the wall of the vapor liquid drum during periods when the liquid level in the drum is considerably depressed below the normal liquid level and during the time the feed liquid inlet to the drum is exposed to and heated by the vapor. This is accomplished by a plurality of vertically arranged perforated trays placed one below the other such that the liquid is broken into small streams and takes a zig zag path as its passes in contact heat exchange with the vapor. Thus the feed liquid means are provided for heating the feed liquid to a temperature approaching that of the wall.

Further, the invention contemplates baffle means in conjunction with said vapor-liquid contacting means to prevent the cool feed liquid from contacting the thick walls of the drum during the initial period of the cool liquid in the drum. Thus the combined action of the baffies and contacting means will result in the rapid heating of the incoming cool feed liquid and thus reducing any temperature stress effects in the drum.

Moreover, there is provided balfie means in the lower portion of the drum to prevent cool feed liquid from rapidly changing the temperature of the drum wall irrespective of the position of the liquid level in the drum.

The vapor-liquid contacting means and drum protecting bafile means provides a solution for the operating problem of vapor-liquid drums which are subject to liquid level variations to the point where practically the entire drum is empty of liquid and allows safe operation of such a drum during these periods of low level.

While in accordance with the provisions of the statutes,

I have illustrated and described herein a specific form of the invention now known to me, those skilled in the art will understand that changes may be made in the form of the apparatus disclosed without departing from the spirit of the invention covered by my claims, and that certain features of the invention may sometimes be used 4 to advantage without a corresponding use of the other features.

I claim:

1. In combination, a vertically elongated vapor-liquid separating drum having a normal liquid level in the upper one-half of said drum separating an upper vapor space and a lower liquid space, said drum being subject to substantial decreases in liquid volume whereby the liquid level drops to substantially the bottom of said drum, vapor-liquid separating means arranged in said drum to discharge separated liquid at substantially the bottom of said drum, a feed liquid inlet pipe arranged with an outlet in the central portion of said drum at a position subjacent said normal liquid level, separate vapor-liquid contacting means of extensive contacting surface area immediately adjacent and below said feed liquid pipe outlet arranged to bring feed liquid into contact with vapor to heat the liquid by condensing the vapor, and means for limiting the travel of cool feed liquid to prevent the cold liquid from contacting the walls of said drum.

2. In combination, a vertically elongated vapor-liquid separating drum having a normal liquid level in the upper one-half of said drum separating an upper vapor space and a lower liquid space, said drum being subject to substantial decreases in liquid volume whereby the liquid.

level drops to substantially the bottom of said drum, vapor-liquid separating means arranged in said drum to discharge separated liquid at substantially the bottom of said drum, a feed liquid inlet pipe arranged with an outlet in the central portion of said drum at a position subjacent said normal liquid level, separate vapor-liquid contacting means of extensive contacting surface area immediately adjacent and below said feed liquid pipe outlet arranged to bring feed liquid into contact with vapor to heat the liquid by condensing the vapor, and means for limiting the travel of cool feed liquid to prevent the cold liquid from contacting the walls of said drum, said vaporliquid contacting means comprising a plurality of perforated trays vertically arranged one below the other.

3. In combination, a vertically elongated vapor-liquid separating drum having a normal liquid level in the upper one-half of said drum separating an upper vapor space and a lower liquid space, said drum being subject to substantial decreases in liquid volume whereby the liquid level drops to substantially the bottom of said drum, vapor-liquid separating means arranged in said drum to discharge separated liquid at substantially the bottom of said drum, a feed liquid inlet pipe arranged with an outlet in the central portion of said drum at a position subjacent said normal liquidlevel, separate vapor-liquid contacting means of extensive contacting surface area immediately adjacent and below said feed liquid, pipe outlet arranged to bring feed liquid into contact with vapor to heat the liquid by condensing the vapor, and means for limiting the travel of cool feed liquid to prevent the cold liquid from contacting the walls of said drum, said vaporliquid contacting means comprising a plurality of perforated trays vertically arranged one below the other, each tray having a bottom portion shaped as a frustum of a cone the included angle of which is obtuse.

4. In combination, a vertically elongated vapor-1iquid separating drum having a normal liquid level in the upper one-half of said drum separating an upper vapor space. and a lower liquid space, said drum being subject to substantial decreases in liquid volume whereby the liquid level drops to substantially the bottom of said drum, vapor-liquid separating means arranged in said drum to discharge separated liquid at substantially the bottom of said drum, a feed liquid inlet pipe arranged with an outlet in the central portion of said drum at a position subjacent said normal liquid level, separate vapor-liquid contacting means of extensive contacting surface area immediately adjacent and below said feed liquid pipe outlet arranged to bring feed liquid into contact with vapor to heat the liquid by condensingthe vapor, and means for limiting the travel of cool feed liquid to prevent the cold liquid from contacting the walls of said drum, said vaporliquid contacting means comprising a plurality of perforated trays vertically arranged one below the other, each tray having a bottom portion shaped as a frustum of a cone the included angle of which is obtuse, each tray having the inclination of its bottom portion oppositely inclined from the adjacent top and bottom trays.

5. In combination, a vertically elongated vapor-liquid separating drum having a normal liquid level in the upper one-half of said drum separating an upper vapor space and a lower liquid space, said drum being subject to substantial decreases in liquid volume whereby the liquid level drops to substantially the bottom of said drum, vapor-liquid separating means arranged in said drum to discharge separated liquid at substantially the bottom of said drum, a feed liquid inlet pipe arranged with an outlet in the central portion of said drum at a position subjacent said normal liquid level, separate vapor-liquid contacting means of extensive contacting surface area immediately adjacent and below said feed liquid pipe outlet arranged to bring feed liquid into contact with vapor to heat the liquid by condensing the vapor, and means for limiting the travel of cool feed liquid to prevent the cold liquid from contacting the walls of said drum, said vapor-liquid contacting means comprising a plurality of perforated trays vertically arranged one below the other, each tray having a bottom portion shaped as a frustum of a cone the included angle of which is obtuse, each tray having the inclination of its bottom portion oppositely inclined from the adjacent top and bottom trays, each of said trays having its largest perforated area at its lowermost portion to cause the cascading feed liquid to take a zig zag path during the heating process.

6. In combination, a vertically elongated vapor-liquid separating drum having a normal liquid level in the upper one-half of said drum separating an upper vapor space and a lower liquid space, said drum being subject to substantial decreases in liquid volume whereby the liquid level drops to substantially the bottom of said drum, a plurality of vertically arranged cyclone type vapor-liquid separators disposed in a circle about the circumferential wall of said drum, said separators being arranged to discharge separated vapor into the vapor space and separated liquid into the liquid space of said drum, a feed liquid inlet pipe arranged with an outlet in the central portion of said drum at a position subjacent said normal liquid level, separate vapor-liquid contacting means of extensive contacting surface area immediately adjacent and below said feed liquid pipe outlet arranged to bring feed liquid into contact with vapor to heat the liquid by condensing the vapor, and means for limiting the travel of cool feed liquid to prevent the cold liquid from contacting the walls of said drum.

7. In combination, a vertically elongated vapor-liquid separating drum having a normal liquid level in the upper one-half of said drum separating an upper vapor space and a lower liquid space, said drum being subject to substantial decreases in liquid volume whereby the liquid level drops to substantially the bottom of said drum, a plurality of vertically arranged cyclone type vapor-liquid separators disposed in a circle about the circumferential wall of said drum, said separators being arranged to discharge separated vapor into the vapor space and separated liquid into the liquid space of said drum, a feed liquid inlet pipe arranged with an outlet in the central portion of said drum at a position subjacent said normal liquid level, separate vapor-liquid contacting means of extensive contacting surface area immediately adjacent and below said feed liquid pipe outlet arranged to bring feed liquid into contact with vapor to heat the liquid by condensing the vapor, and means for limiting the travel of cool feed liquid to prevent the cold liquid from contacting the walls of said drum, said vapor-liquid contacting means comprising a plurality of perforated trays vertically arranged one below the other, each tray having a bottom portion shaped as a frustum of a cone the included angle of which is obtuse.

8. In combination, a vertically elongated vapor-liquid separating drum having a normal liquid level in the upper one-half of said drum separating an upper vapor space and a lower liquid space, said drum being subject to substantial decreases in liquid volume whereby the liquid level drops to substantially the bottom of said drum, vapor-liquid separating means arranged in said drum to discharge separated liquid at substantially the bottom of said drum, a feed liquid inlet pipe arranged With an outlet in the central portion of said drum at a position subjacent said normal liquid level, separate vapor-liquid contacting means of extensive contacting surface area immediately adjacent and below said feed liquid pipe outlet arranged to bring feed liquid into contact with vapor to heat the liquid by condensing the vapor, and means for limiting the travel of cool feed liquid to prevent the cold liquid from contacting the walls of said drum, said last named means including longitudinally disposed bafiie plates arranged to contain the cool feed liquid in the central portion of the normal liquid space of said drum during the feed liquids initial period in said drum.

References Cited in the file of this patent UNITED STATES PATENTS 37,258 Miller Dec. 23, 1862 669,667 Smith Mar. 12, 1901 958,845 White May 24, 1910 2,300,852 Wood Nov. 3, 1942 2,654,351 Ammon Oct. 6, 1953 2,669,975 Frisch Feb. 23, 1954 2,708,981 Armacost et al. May 24, 1955 FOREIGN PATENTS 1,069,632 France July 9, 1954

Images