US2877748A

US2877748A - Once-through vapor generator

Info

Publication number: US2877748A
Application number: US518182A
Authority: US
Inventors: Jantscha Robert; Kolling Johann
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1955-06-27
Filing date: 1955-06-27
Publication date: 1959-03-17
Anticipated expiration: 1976-03-17

Description

March 17, 1959 R. .QIANTSCHA AL 2,877,748

ONCE-THROUGH VAPOR GENERATOR Filed June 27, 1955 FIG. 2

IN VEN TORS ROBERT JANTSCHA BY JOHANN KOLLING ATTORNEY United States Patent O ON CE-THROUGH VAPOR GENERATOR Robert Jantscha and Johann Kolling, Oberhausen, Germany, assignors to The Babcock & Wilcox Company,

New York, N. Y., a corporation of New Jersey Application June 27, 1955, Serial No. 518,182

2 Claims. (Cl. 122459) This invention relates to forced flow tubular boilers. In the generation of steam during forced flow through a gas heated tube system the greatest ditficulties are experienced in the part in which the last remnants of water are evaporated, the so called transition zone. It is known to protect this part by disposing it in a region of rela tively low flue gas temperature. This, however, entails distributing the injurious effects over a larger heating surface. As an alternative, feeding with surplus water and the use of a separator has been adopted. The whole of the surplus water may be discharged if the percentage used is not too great. Otherwise water is returned to the feed pump. Since the separator makes a transition zone unnecessary, the difficulties connected with such a zone are avoided.

The present invention includes the method of generating steam, according to which most of the water to be vaporized is evaporated and the generated steam is super heated in heat exchange means subjected to hot gases and the remainder of the water to be vaporized is evaporated by heat exchange with the superheated steam.

The invention also includes a forced flow, tubular v boiler comprising a vaporizing stage exposed during operation to hot gases followed by a second vaporizing stage arranged to operate with vapor generated and superheated in the unit as the heating medium.

The invention moreover includes a forced flow, once through, tubular boiler comprising a vaporizing stage exposed during operation to hot gases and adapted to effect most of the evaporation, followed by a second vaporizing stage adapted to complete the evaporation and arranged to operate with vapor generated and superheated in the unit as the heating medium.

By heating the transition zone with superheated steam the difiiculties normally experienced with a transition zone are to a great extent eliminated. Moreover, this solution possesses the advantage that operation may be either with or without surplus water.

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. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawing and descriptive matter in which is illustrated and described a preferred embodiment of the invention.

In the drawings:

Figure 1 is a diagram illustrating the invention;

Figure 2 is a sectional elevation of a surface heat exchanger, a mid portion being broken away; and

Figure 3 is a sectional plan view taken partly on the line 33 of Figure 2.

Fig. 1 shows a steam economizer 1 discharging to a tube system 2 of a surface heat exchanger 4, the complementary element of which is a pressure vessel enclosing the tube system. Between the outlet of the tube system 2' and the inlet to the vessel of the heat exchanger 2,877,748 Patented Mar. 17, 1959 4 is connected the superheater 3, while the outlet from the vessel is connected to the superhcater 7.

During operation, the residual water content of the steam flowing from the steaming economizer 1 through the tube system 2' is evaporated through heat exchange with superheated steam flowing from the superheater 3 through the vessel of the heat exchanger 4.

In Figures 2 and 3, which show a suitable form of surface heat exchanger for use in the boiler of Figure l, a pressure vessel or tube shell 13 comprises four

tube sections

14, 15, 16 and 17 welded together, the

tube sections

14, 15 and 17 being of somewhat greater diameter than the tube section 16. The outer ends of the

sections

14 and 17 are dished and are formed respectively with

nozzles

18 and 19, while the

sections

14 and 15 are severally formed with

nozzles

20 and 21.

The tube system 2' comprises a tube plate 22 welded to the tube section 15 adjacent the weld between that section and tube section 14. Welded to the tube plate 22 are the ends of tubes 23, arranged as a circular bank, and at their other ends the tubes are reduced in diameter and are welded to a tube plate 24 of slightly less diameter than the tube section 16. At the side of the tube plate 24 remote from the tube bank is formed a chamber by means of a hemispherical reversing hood 25 welded to the tube plate and in communication with the chamber and extending through the tube plate 22 to the nozzle 18 constituted by the outer end thereof is a coaxial tube 26 Welded to the tube plates and to the tube section 14. The flow area through the tube 26 is approximately equal to the sum of the flow areas through the tubes 23.

The use of four tube sections in the formation of the pressure vessel has been adopted in order to facilitate manufacture. During assembly, after the tube system comprising the

tubes

23, 26, the

tube plates

22, 24 and the hood 25 and the

tube sections

15, 16 and 17 have been welded together, the tube system is introduced into the said tube sections and the tube plate 22 is welded to the tube section 15. Finally, the tube section 14 is placed in position and welded to the tube section 15 and the end of tube 26.

In use, the nozzle 19 is connected to the steaming economizer 1 so that the steam and water mixture flows upwardly in the vessel 13 around the tubes 23 to the nozzle 21, which is connected to the superheater 3. The outlet from the superheater 3 is connected to the nozzle 20 so that the superheated steam flows downwardly through the tube 23 to the chamber between the tube plate 24 and the hood 25 and then on through the tube 26 to the nozzle 18, which is connected to the superheater 7.

Generally, the direct contact heat exchanger or the surface heat exchanger will be arranged outside the boiler casing in proximity to the sections of heating surface associated therewith. In some instances a plurality of surface heat exchangers may be arranged in parallel with one another.

The invention may be applied to an existing force flow, once through boiler having a transition zone by utilizing the transition zone as a'superheater of the steam which effects evaporation of the residual water.

In the above description no mention has been made of the regulation of the supply of feed water, of heating, of constant water level or of final steam temperature, as methods of effecting such regulation are known.

While in accordance with the provisions of the statutes, there is illustrated and described herein specific embodiments of the invention, those skilled in the art will understand that changes may be made in the form of the invention covered by the claims, and that certain features of the invention may sometimes be used to advantage without a corresponding use of the other features.

What is claimed is:

1. In a once-through type vapor generator including a heat source, a conduit presenting heating surfaces wherein a vaporizable fluid is heated until there is a vapor-liquid mixture consisting of predominantly vapor and the last remnants of liquid, an indirect heat exchanger out of contact with the heat source and arranged to receive said vapor-liquid mixture, a vapor super heater receiving heat from said source and having its vapor inlet connected to one side of said heat exchanger, and means for passing superheated vapor from the exit of said superheater through said heat exchanger to effect the complete evaporation of said last remnants of liquid from said mixture and to also partially superheat the resulting vapor.

2. In a once-through type vapor generator including a heat source, a conduit presenting heating surfaces wherein a vaporizable fluid is heated until there is a vapor-liquid mixture consisting of predominantly vapor and the last remnants of liquid, an indirect heat exchanger out of contact with the heat source and arranged to receive said vapor-liquid mixture, a primary vapor superheater receiving heat from said source and having its vapor inlet connected to one side of said heat exchanger, means for passing superheated vapor from the exit of said primary superheater through said heat exchanger to effect the complete evaporation of said last remnants of liquid from said mixture and to also partially superheat the resulting vapor, and a secondary superheater in contact with the heat source and con nected to said heat exchanger for final heating of the vapor issuing from said primary superheater.

References Cited in the file of this patent UNITED STATES PATENTS