US3189007A - Steam generating unit - Google Patents

Description

June 15, 1965 M. H. KUHNER 3,139,007

STEAM GENERATING UNIT Filed Sept. 23. 1963 MAX H. KUHNER INVENTOR.

United States Patent This invention relates to a steam generating unit and,

i more particularly, to apparatus arranged to produce steam for use in an electrical generating turbine.

In the art of generating steam, one of the outstanding problems is that of obtaining pure steam. It is the usual practice to separate the steam from the boiler water in a separating vessel known as a steam-and-water drum, the water falling to the bottom of the drum for recirculation through the boiler and the steam rising to the top eventually to progress to a turbine. In most cases, however, after leaving the drum, this steam is first subjected to further heating to superheat it. Whether the steam flows directly to the turbine from the drum or is subjected to a superheating step, it is important that no particles of water pass out of the drum with the steam. It is also important that certain chemicals, such as dissolved silica, do not leave the drum with the steam because this would result in a coating of the superheater or turbine surfaces and destroy their eifectiveness. Many schemes have been provided in the past for purifying steam in the drum, but they have been, as a rule, quite expensive and have been economically unfeasible for boilers of smaller intermediate size where cost is an important consideration. These and other difiiculties experienced with the prior art devices have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a steam generating unit containing a steam separating apparatus which is extremely effective in operation and yet is low in cost.

Another object of this invention is the provision of a steam generating unit containing steam cleaning apparatus which is simple and uncomplicated in construction and which is relatively free of maintenance problems.

A further object of the present invention is the provision of a steam generating unit having steam cleaning equipment which may be readily installed and replaced through a manhole in the steam-and-water drum.

It is another object of the instant invention to provide a steam cleaning apparatus which is simple and uncomplicated in concept and which will not be rendered inoperative by salt deposits or the like.

It is a further object of the invention to provide a steam separator which is inexpensive to manufacture and which is capable of a long life of useful service with a minimum of care.

With these and other objects in view, as will be ap parent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.

The character of the invention, however, may be best understood by reference to one of its structural forms, as, illustrated by the accompanying drawings in which:

FIG. 1 is a vertical transverse sectional view of a steam generating unit embodying the principles of the present invention,

FIG. 2 is a perspective view of a steam separator forming part of the invention,

FIG. 3 is a longitudinal vertical sectional view of the apparatus taken on the line IIL-III of FIG. 1,

FIG. 4 is a perspective view of a steam condenser portion of the apparatus, and

FIG. 5 is a perspective view of a steam release portion of the invention.

3,1891%? Patented June 15, 1955 Referring first to FIG. 1, wherein is best shown the general features of the invention, the steam generating unit, indicated by the reference numeral 10, is shown as comprising a steam-and-water drum 11 having boiler downcomer tubes 12 extending from its lower portion, riser or steam release tubes 13 extending into one side, and steam oiftake tubes 14 extending from the upper portion. The steam olftake tubes 14 are connected to a superheater and from the superheater to a turbine (not shown). Within the steam-and-water drum 11 is a body 15 of water having an upper surface 16 located generally below the centerline of the drum. Also located in the drum are a primary separator 17, steam condensers 18, and a steam separator 19. The drum is provided with a manhole 21, a chemical feed pipe 22, and a continuous blow-down pipe 23.

The primary separator 17 is mounted immediately in front of the steam release tubes 13 and consists of a series of channel irons 24 arranged in staggered relationship supported at their upper ends on the inside surfaces of the wall by means of a bracket 25 and having their lower ends extending below the surface 16 of the body 15 of water. This construction is shown particularly well in FIG. 5.

The condensers 18 are clearly shown in FIG. 4. A large feed water pipe 26 receives fresh feed water from the feed water pump (not shown). Connected to the upper portion of the pipe 26 are a series of hairpin-shaped pipes 27 having discharge nozzles 28 mounted on their lower or discharge ends which reside below the surface 16 of the water. The intermediate parts of the pipes 27 are provided with fins 29 which act as extended surface elements. The pipes 27 are spaced side-by-side and the fins 29 extend laterally sufficiently so that there is little or no space between them. It is interesting to note that the nozzles 28 are located below the surface 16 of the body 15 of water and are directed at various angles to promote proper distribution of the water within the drum.

Referring to FIGS. 2 and 3, it can be seen that the steam separator 19 consists of a main housing 31 which is of tubular form and which has a generally spiral shape. The housing is formed from a first semi-circular metal sheet 32 and a second semi-circular metal sheet 33 which are held in fixed relation by end plates 34 and 35. a The top edges of the first and second sheets 32 and 33 are spaced radially apart to provide an inlet slot 36. The bottom edges are separated slightly to provide a water outlet slot 37. Elongated plates 3% and 39 fill in the slot at the ends adjacent the end plates 34 and 35, respectively, so that the slot 36, as is evident in FIG. 2, occupies substantially less than the entire length of the housing 19. Located generally coaxially of the main housing 31 is a dry pipe 41 which is an elongated tube of circular crosssection having open ends and a steam outlet conduit 42 which is located in its central portion and which extends horizontally through the wall of the second sheet 33 of the housing 31. Underlying the water outlet slot 37 is an enclosed trough 43 from which extends at least one elongated vertical pipe 44 whose lower end is located well below the surface 16 of the body 15 of water. It should be noted, of course, that the water outlet slot 37 is arranged so that the edge of the first sheet 31 is slightly raised above the edge of the second sheet 33, for a purpose which will be explained more fully hereinafter. Furthermore, as is evident in FIG. 1, although the dry pipe 41 is generally coaxial of the main housing 31, its axis is slightly above the axis of the first sheet 31 and slightly to the left of it, thus providing a generally diminishing spiral effect in the passage from the entrance inlet slot 36 around the dry pipe and back to the slot again.

A sheet metal bafile or wall 45 is fastened to the inside surface of the drum 11 immediately above the steam sepa arator 19, extends at an angle, then vertically downwardly, and then horizontally to the left (in FIG. 1) to terminate immediately above the top of the fins 29 of the condensers 18. A second wall 46 is fastened to the inner surfaces of the drum lliatthe other side-of the superheater-tubes 14, advances downwardly at an angle and then horizontally to jointhe vertical portion ofthe wall 45. The, wall 45' and the wall 46, therefore, form an elongated enclosure 47 surrounding the ends of the steam oiftake tubes 14. Furthermore, the steam outlet conduit 42 not only extends through they wall of the vhousing 31: but also extends through the wall 45 into the enclosure. 47. i 7 The operation of the apparatus will now bereadily understood in view of the above description. In the usual way,-water leaves the body 15 ofwater and passes downwardly through the boiler downcomer tubes 12. Eventu ally, after passing throughthe boiler and being subjected to heat from hot products of combustion, steam is generated in the tubes and a mixture ofthe water and steam leaves the riser orsteam release tubes 13. In the ideal situation, of course, pure steam would leavethe steam release tubes but, as a practical matter, considerable water falls out of, the tube ends into the body 15. The steam, however, rises and passes laterally over the .top of the surface 16 of the body 15, through the channel irons 24 of the primary separator 17 where a considerable portion of retained water is knocked down and falls into the body 15. The steam continues laterallyacross' the drum in the area of its. horizontal diameter. passes, over the condensers 18. The steam, when it strikes the plates 24, is condensedbecause of the cold feed water which enters the system through the feed water pipe 26 and passes through the pipes 27 for discharge into the body 15. This cold feed water cools the fins 18 as well as the surface of the pipes and the steam passing over these cold surfaces condenses to a certain extent, making the surfaces wet, so that particles of chemical, foreign between the surface of the first sheet 32 :of the main housing 31 of the steam separator 19 and'the inner surface of the drum 11. The steam entersthis wedge-shaped pasage and, eventually, is ledto the slot 36 in the steam separator. 7 I

Now, the flat slot 36 is dimensioned both-in its width and its length in such a mannerthat steam flows through it at avelocity atdesign load of approximately 75 feet-per second; this particular value has proved to be successful in practice. Passing through the slot, the steam, lpresumably with some water still retained, passescounterclockwise in'the space between the outer surface of the dry pipe 41 and the inner surface of the main housing 31. At the extremely high velocity, describedabove, centrifugal force throws the heavier elements, particularly the .water particles outwardly, so that they glide along the inner surface f the housing. Eventually,;the material reaches the slot '37land because of the factlt ha-t the upper edge of the slot 37 is above the lower edge, the'thin layer of water on the inner surface of the second sheet 33 of the housing passes through the slot and is separated by this dividing line or knife edge from the rest of the material flowing around the housing. The remainder of the material is mostly steam and continues around and, at the same-time, moves axially outwardly toward the ends of the housing. At these ends it is abletoenter the ends of the dry pipe'41 and flow inwardly lengthwise 0 thedry pipe to the central steam outlet. conduit 42.

Eventually, it

4 The steam passes through the conduit, through the wall of the housing 31, then through the wall into the enclosure 47. From the enclosure the steam enters the tubes 14 and passes on either to the superheater or to the turbine, depending on the particular arrangement of the boiler. The water which passed through the water outlet slot37 does so with extremely high kinetic energy. The water drops into the trough 43 and then passes downwardly through the pipe 44 into the body 15 of water. The kinetic energy in this water produces an extremely high downward pressure in this pipe, thus assuring that there will be no suction action which would have a tendency to draw water up through the pipe from the-body 15 into the pipe and possibly up .intothe' steam separator itself. Such a drawing of Water into the steam separator, ofcourse, wouldpromote-steam carry-over int-o the tubes 14, which is the condition that it is most desirable to avoid. In otherwords, the presentapparatus not only separates the water particles which are left in the steam after they leave the condensers '18 butrallso guarantees that no further waterwould be added.

. By the practice of the present invent-ion, it has been found that water of extremely high purity enters the tubes 14 and there is no danger of Water being carried over into these tubes with consequent damage to the superheater and turbine. Generally speaking, such water would contain very high amounts of chemicals, such as salts, which, if deposited on the inner walls of the superheater, would eventually cause destruction of the superheater because of reduction of heat transfer ability, since the salt acts as an insulation. Such salt deposits on the turbine destroy the carefully-formed aerodynamic surface of the turbine blades and destroys the ,efiiciency of the turbine. It should be noted that the fact-that the passage between'the main housing and the dry .pipe reduces in cross-sectional area from the slot 36 around the dry pipe produces a tendency in the steam to rnove axially outwardly of the dry pipe so that it is able to enter the open ends of the dry pipe which lie Iadjacent the end plates 34 and 35 of the housing. .Ascan be seen at the upper part, there is a small space between the upper surface ofthe dry pipe 41 and the firstsheet 32 ofv the housing and some steam will pass around and recirculate j around the circuit once-more, but there is'noharm in this the separator.

recirculation. p

It can be observed that this construction isquite simple and foolproof. There are no .intricate or moving parts to'be rendered inoperative by salt deposits and the apparatus will work well, even when some of the dim'ensions have been changedby the deposits which normally take place in a boiler drum. Also, it may be observed that the housing 31 is of small enough diameter-thatit may be readily removedthrough the, manhole 21 in case replacement is necessary. Connections, such as the pipes 44 and so on, are, of course, removed before such removal from the drum is attempted. In other words, it requires onlyv a short time and "relatively little expense to replace It'is obvious that minor changes may be madein the form and construction of the invention without departing fromthematerial spirit thereof. It is not, however,

desired to confine theinvention to the exact form herein shown and described, but it is desired to include all such as properly come within the scope claimed. I The. inventionhaving been, thus described, what is claimed as 'newand desired to secure by Letters Patent, is:

1. Av steam generating unit, comprising 7 (a) a steam-and-water drum of generally elongated cylindricalform, (b) a steam separator housing of elongated tubular -form lying in the drum with its-axis parallelxto the axis of the drum, the housing having'closed ends, (c) a dry pipe lying withiniand spacedfrom the housing generally coaxial thereof, the pipe being shorter than the housing-andhavingatleast one open end V extending to a point immediately adjacent to the end of the housing,

(d) a steam oft-take conduit located on the dry pipe at a position substantially removed from the said open end, the oft-take conduit extending from the pipe and through the housing,

(e) means forming an entrance slot extending longitudinally of the housing,

(f) a water outlet slot extending longitudinally of the housing diametrically opposite the inlet slot,

(g) a drain trough underlying the housing to receive water from the outlet slot, and

(11) means forming a passageway surrounding the dry pipe leading from the outlet slot to the entrance slot to cause steam which does not flow from the inlet slot to the inside of the dry pipe to join steam entering the entrance slot for the first time.

2. A steam generating unit as recited in claim 1, wherein the drum has a horizontal axis and the separator housing is located in the upper portion of the drum.

3. A steam generating unit as recited in claim 1, wherein the dry pipe is open at both ends and the steam cit-take conduit is located midway between the ends.

4. A steam generating unit as recited in claim 1, wherein the entrance slot lies in a radial plane and the housing provides an edge which is spaced radially outwardly of the main body of the housing, the edge and the slot being directed toward the oncoming steam.

5. A steam generating unit as recited in claim 1, Wherein the water outlet slot is defined by an edge directed toward the oncoming steam and spaced radially inwardly of the adjacent portion of the housing.

6. A steam generating unit as recited in claim 1, wherein the housing is formed of two semi-cylindrical sheets of diltercnt diameter joined in facing relationship, the slot being formed by the differences in diameters of the two sheets, and wherein the dry pipe is coaxial of the sheet of larger diameter.

References Cited by the Examiner UNITED STATES PATENTS 2,409,625 10/46 Haase 55-442 2,824,551 2/58 Taggert 122-459 2,918,139 12/59 Silverrnan 55449 PERCY L. PATRICK, Primary Examiner.

KENNETH W. SERAGUE, Examiner.

Claims (1)

1. A STEAM GENERATING UNIT, COMPRISING (A) A STEAM-AND-WATER DRUM OF GENERALLY ELONGATED CYLINDRICAL FORM, (B) A STEAM SEPARATOR HOUSING OF ELONGATED TUBULAR FORM LYING IN THE DRUM WITH ITS AXIS PARALLEL TO THE AXIS OF THE DRUM, THE HOUSING HAVING CLOSED ENDS, (C) A DRY PIPE LYING WITHIN AND SPACED FROM THE HOUSING GENERALLY COAXIAL THEREOF, THE PIPE BEING SHORTER THAN THE HOUSING AND HAVING AT LEAST ONE OPEN END EXTENDING TO A POINT IMMEDIATELY ADJACENT TO THE END OF THE HOUSING, (D) A STEAM OFF-TAKE CONDUIT LOCATED ON THE DRY PIPE AT A POSITION SUBSTANTIALLY REMOVED FROM THE SAID OPEN END, THE OFF-TAKE CONDUIT EXTENDING FROM THE PIPE AND THROUGH THE HOUSING,

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