US2984468A - Spray desuperheater - Google Patents

Description

May 16, 1961 M. H. KUHNER SPRAY DESUPERHEATER 2 Sheets-Sheet 1 Filed Aug. 26, 1958 Q mm @v INVENTOR. max F1. ffuhner H OT ey May 16, 1961 M. H. KUHNER 2,984,468

SPRAY DESUPERHEATER Filed Aug. 26, 1958 2 Sheets-Sheet 2 5449779 4 3 max Fifi-9321227 45 fifii? United States Patent SPRAY DESUPERHEATER Max H. Kuhner, Worcester, Mass., assignor to Riley Stoker Corporation, Worcester, Mass., a corporation of Massachusetts Filed Aug. 26, 1958, Ser. No. 757,368

1 Claim. (Cl. 261-79) This invention relates to a spray desuperheater and more particularly to apparatus for controlling the temperature of superheated steam by the introduction of water into the steam.

In many situations the steam which emerges from the superheater of a steam generating unit is at a temperature considerably higher than is desirable for use in the steam turbine. For that reason, it is the usual practice to introduce into the line leading to the turbine a so-called steam desuperheater, one of the common types of which involves the introduction of a spray of water into the steam flow. In this device the water droplets are converted into steam which is superheated by the steam already in the line, thus removing heat from the steam in the line and lowering its temperature. The most common design of desuperheater makes use of an adjustable valve whose outlet resides in the steam line and is provided with an orifice for projecting water in the form of a spray into the steam flow; the orifice is adjustable and in many cases is of the so-called needle valve type. As can be readily imagined, the valve is subjected to very severe service, since it is situated in an area of very high pressure and temperature. Since the valve is necessarily introduced into the main pipes leading to the turbine, a breakdown of the valve is a very serious thing and causes the complete shut-odwn of the steam generating unit. Such shut-downs have occurred quite often in the past because of the fact that the valve is quite intricate and is readily rendered inopera tive by corrosion and by erosion of the orifice surfaces. These and other difficulties experienced with prior art devices of this type have been obviated in a novel manner by the present invention.

It is an outstanding object, therefore, of this invention to provide 'a spray desuperheater permitting adjustment of the amount of water spray but which nevertheless is subject to a minimum of 'corrosion or erosion.

Another object of this invention is the provision of a steam desuperheater system which is practically foolproof and which will seldom require a shut-down of the steam generating unit because of inoperativeness of the desuperheater.

Another object of the invention is the provision of a desuperheater making use of a very simple and rugged spray nozzle.

To the accomplishment of the foregoing and related ends, the invention, then, comprises the features hereinafter fully described and pointed out in the claim, the following description and drawings setting forth in detail a certain embodiment of the invention, these being indicative, however, of but one of the various ways in which the principles of the invention may be employed.

In said annexed drawings:

Fig. l is a sectional view which is schematic in part of apparatus embodying the principles of the present invention;

Fig. 2 is a sectional view of the apparatus taken on the line II-II of Fig. 1;

Fig. 3 is a sectional view of the apparatus taken on the line III-III of Fig. 1; and

Fig. 4 is a sectional view of the apparatus taken on the line IV--IV of Fig. 1.

Referring first to Fig. 1 wherein is shown the general features of the invention, the spray desuperheater indicated generally by the reference number 10, is shown associated with a tube 11 leading from the superheater of a steam generating unit (not shown). It will be understood that throughout this application references to a superheater and associated elements also refer to a reheater which is, of course, only a specialized form of superheater. The tube 11 is connected at right angles to the axis of the steam header 12 leading to a turbine (not shown); the tube 11 is welded adjacent one end of the steam header 12. The under end of the steam header 12 is enclosed by hemispherical heads 13 which in turn is provided with an inspection opening 14 coaxial therewith closed by a cap 15 which is welded thereto. The tube 11 is welded to the steam header 12 so as to surround a steam opening 16 which is located at and somewhat spaced from the head 13. A vane support ring 17 of a generally annular shape, as is best shown in Fig. 2, is located adjacent one end of the steam opening 16 and is welded to the inner surface of the steam header 12. A similar vane support ring 18 is mounted in the tube centrally of the opening 16 while a third vane support ring 19 is Welded at the opposite end of the opening 16. The three support rings support a scroll 21 having one end 22 which touches the surface of the steam header 12 and another end 23 which is somewhat spaced therefrom, as is evident in Fig. 2. The opening 16 extends around the periphery of the tube to the level of the center line and is somewhat ovoid in shape, the tube 11 extending upwardly around the sides of the steam header 12 to enclose this opening. Extending between the vane support rings 17, 18 and 19 in the portions thereof not occupied by the scroll 21 are steel deflector vanes 24, 25, 26, 27 and 28, vane 25 only being shown in Fig. 1, the remainder of the vanes being shown in Fig. 2. The vanes are inclined, as is evident in Fig. 2, to give a clockwise motion to the steam flow as it enters the space defined by the scroll 21. Vane support ring keys 29 and 31 are located in the upper part of the tube.

The liner 21 extends lengthwise of the steam header 12 only slightly beyond the length defined by the vane support rings 17 and 19, and from the end thereof which faces away from the head 13 is a tubular liner 32, which in a general way constitutes an extension of the scroll 21 that is not open at the bottom. The liner 32 is fastened to the upper inner surface of the steam header 12 by means of a liner spacer 33 which only extends part-way around the liner, as is evident in Fig. 3. At the other end of the liner 32 its outer surface has welded thereto skid bars 34 which are spaced around its surface and provide for supporting the tube within the steam header 12 but maintaining a spacing therebetween while allowing longitudinal sliding due to thermal expansion. Supplemental liner spacers 35 and 36 are welded between the liner 32 and the inner surface of the steam header 12 in the lower portion thereof to provide with the spacer 33 complete support for one end of the tube.

The liner spacer 33 is notched to receive in a slidable manner the keys 29 and 31 which are welded to the inner surface of the steam header 12. Locating blocks 37, 38 and 39 are welded to the inner surface of the steam header 12 in position to contact the liner spacers 33, 35 and 36 respectively. The liner 32 and its associated equipment is welded to the scroll 21 and the associated vane support rings and vanes so that the entire assembly forms a single unit.

Extending through the steam header 12 in the upper portion thereof at a position somewhat spaced from the opening 16 is an opening 41 which is aligned with a similar opening 42 in the liner 32. Welded to the tube in the portions surrounding the opening and-extending upwardly therefrom is a tubular supporting fitting '43 having an inwardly extending portion 44 which merges with an inwardly extending nozzle 45. The outer surface of the stem 45 and the inner surface of the fitting 43 define a steel insulating space 46 of the elongated annular form having of course access to the interior of the steam header 12. Extending into the stem from the exterior of the portion 44 is a bore 47 which is provided with a counterbore 48 at its outermost portion to receive a water pipe 49. The bore 47 terminates just short of the lower end of the stern, which lower end is located slightly below the axis of the steam header 12. Exactly on the axis of the steam header 12 the stem is provided with a venturi-shaped orifice 51 which extends from the bore 47 to the exterior of the stem and faces in the direction away from the entrance of the tube 11 into the steam header 12. Extending from the wall of the stem opposite the orifice 51 within the bore 47 is a nose 52 which extends into the orifice to approximately the mid-point thereof. As has been stated, the orifice is of a venturi form and has a flared portion which opens into the bore 47 and another flared portion which opens outwardly of the stem; the nose 52 resides in the first-mentioned flared portion and has its end located in the point of the venturi of minimum diameter. The surface of the nose 52 and the surface of the orifice 51 are coated with Stellite or other hard material. As is best evident in Fig. 4, the cross-sectional shape of the exterior of the nozzle 45 is a teardrop shape and has its portion of greatest curvature facing downstream in the steam header 12, or in the direction away from the entrance of the tube 11. The orifice 51 opens on this portion of greatest curvature. A number of circular'apertures 53 extend through tlge wall of the liner 32 at the end adjacent the opening 1 The water pipe 49 is connected by a Y-fitting 54 into a branch pipe 55 and a branch pipe 56. The branch pipe 55 contains two shut-01f Valves 57 and 58 and between them is located a pressure-controlled variable orifice valve 59.

In a similar manner the branch pipe 56 contains two shut-off valves 61 and 62 between which lies a variable orifice valve 63. The branch pipes 55 and '56 merge again into a water pipe 64 leading to a source of water under highpressure (not shown). 'It will be understood that the adjustable orifice valves 59 and 63 are of the type which are controlled though remotely by use of pneumatic pressure, or the like, and are connected into a superheat control system of the usual type making use of the temperature of output superheated steam to main tain this temperature at a constant preselected value irrespective of load on the'unit.

The operation of the apparatus will now be readily understood in view of the above description. Superheated steam enters the apparatus'through the tube 11; it will be assumed that this steam is at greater temperature than the desired final steam temperature leaving the steam header '12 and entering the turbine. As the steam enters the steam header 12 at right angles to its axis it passes over the vanes 24, 25, 26, 27 and 28 and is directed into a swirling action within the scroll 21 and the liner 32 in a clockwise direction as the apparatus is viewedin Fig. 2. A small amount of steam enters the space between the scroll 21'and the liner 32 and the insidewall of the steam header 12, forming a steam jacket therebetween. The steam then moves surely below the scroll '21 into the liner 32 and passes over the nozzle 45 lengthwise toward the turbine. At the same time water is entering the bore 47 in the nozzle 45. This water originates in the pipe 64. and passes through one of the branches 55 and 56; if the valves '62-'and 61 are'shut,

then the valves 57 and 58 are open, the water will pass through the branch pipe 55 and through the adjustable orifice valve 59 into the pipe 49 and the nozzle 45. This water is on a higher pressure than the steam pressure in the steam header 12 and passes between the nose 52 and the orifice 51 which are in such a way as to produce a spray of water downstream in the liner 32. The steam which is passing axially is in a 'high state of turbulence due to the action of the vanes and it mixes readily with the water spray. The water and steam mix to produce a superheated steam at a lower temperature than the steam which originated in the tube 11. Any expansion or contraction of the liner 32 is taken care of by the sliding action between the skid bars 34 and the inner wall of the steam header 12. It should be noted that in assembling the apparatus the hemispherical head 13 is removed and the assembly of the scroll 21, the liner 32, the vane supporting rings 17, 18 and 19 and the vanes are slid into the steam header 12 from that end. The keys 29 and 31 should be in notches in the vane supporting rings 17, 18 and 19 and the notches in the liner spacer 33. Eventually the liner spacer 33 strikes stops which are welded on the inner surface of the steam header 12 and the whole unit is located so that the aperture 41 in the steam header 12 and the aperture 42 in the liner 32 are aligned. At that point the vane supporting ring 17 is tack-welded to the inner surface of the tube to hold the whole unit in place. Then the hemispherical head 13 is welded to the tube. There should be very little reason for the dismantling of the apparatus, but as is readily evident, this is not a difiicult matter due to this method of assembly. If, for any reason, the orifice in the valve 59 becomes clogged, it is possible to shut off the valves 57 and 58 and open the valves 61 and 62 so that water flows through the branch pipe 56 rather'than the branch pipe 55. Then it is possible to remove the valve 59 and replace it or repair it.

The above construction has a great many advantages. First, a spray nozzle of this type can be designed to insure good mechanical atomization of the water throughout a range of water flow of one to 'ten. The internal spray assembly presented here has replaceable parts. It is permanently installed and tamper-proof. The spray nozzle shank can be machined from a solid alloy steel forging with the portions subjected to steam flow of teardrop cross-section to present minimum resistance of the type of steam passing over it. That section of the shank enclosed by the fitting 43 is formed of circular cross-section of maximum strength. A steam jacket is provided around the spray nozzle shank to insulate it from the pressure parts of the steam header 12 and the welded nozzle to prevent thermal stresses on the welded joints by temperature differences betweenspray water and steam. Surfaces subjected to possible wear by water erosion are covered with Stellite. The elements of the assembly are completely shop-assembled and assembled by welding. Shop-fabrication of the welded joints insures perfect alignment, ideal control-of welding and proper stress-relieving following the completion of all t in position at the spray nozzle or stem 'and is permitted to expand and contract independently 'of the steam header 12, with its discharge end carried on the skid bars.

The apertures 53 provided near the upstream end-ofthe spray header.

right angle to produce turbulence. Because complete It is of interest, also, to note that the" steam 'to be cooled enters the steam header 12 at a atomization cannot be expected at water flow rates below approximately 10% of the maximum, a breakup and thorough mixing of water driplets are assisted by turbulence of the steam passing across the spray nozzle. The steam entering the header at an angle is given a spin by the directional vanes which are formed with an extension of the spray liner and these vanes and their supporting scroll or liner can be of heavy welded construction and formed of alloy steel.

Other modes of applying the principles of the invention may be employed, changes being made as regards the details described, providing the features included in the following claim are the equivalent of such being employed.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent, 1s:

A spray desuperheater, comprising a spray header, an entrance tube connected to the header to admit superheated steam at a right angle to the axis of the header, a spray nozzle extending into the header at a right angle thereto at a position spaced along the header in the direction of steam flow, the nozzle having a fixed orifice aligned with the axis of the header and facing downstream, means producing turbulence in the stream of steam as it enters the header, and means external of the header for adjusting the flow of water to the nozzle, the said means producing turbulence consisting of a scroll extending partially around the inner surface of the header opposite the entrance of the tube thereto, the scroll being in a position separated from the inner surface of the header by a gradually increasing amount from one edge to the other, supporting rings maintaining the scroll in the said position spaced from the said inner surface of the header, and vanes extending axially of the header at the entrance of the tube to the header, the 'vanes having substantial angles of attack to the flow of steam in the tube and inclined in the same general direction to produce a swirling of the steam in the scroll.

References Cited in the file of this patent UNITED STATES PATENTS 1,961,956 Bleibtreu et al. June 5, 1934 2,155,986 Wheaton Apr. 25, 1939 2,409,088 Weits et al Oct. 8, 1946 2,550,683 Fletcher et al. May 1, 1951 2,688,943 Wickland Sept. 14, 1954

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