US1883605A - Steam reheater - Google Patents

Description

Oct. 18, 1932. c. H. @Avy 3&883595 STEAM REHEATER Filed Feb. e, 1951 2 sheets-sneu 2 INVENOR Christo/Uber' H. a BYM- ATTORNEY Patented Oct. 18, 1932 NITED CHRISTOPHER HUMPHREY DAVY, 0F BLACK-IEATH, LONDON, ENGLAND, ASSIGNOR TO THE BABCOCK & WLCOX COMPANY, 0F BAYONNE, NEXV JERSEY, A CORPORA- Tro'n or NEW JERSEY STEAM BEHEATER Application filed February 6', 1931, Serial No. 513,954, and in Great Britain May 14, 1930.

This invention relates to fluid heat exchange apparatus, and is more particularly concerned with steam reheaters.

In steam power plants using multi-stage turbines it has been found advantageous to reheat steam exhausting from one turbine stage and proceeding to a stage of lower pressure. In this way steam may be expanded within the turbine stages without excessive condensation. `When high pressure steam is supplied to the high pressure stage of the turbine it is superheated. During its expansion within that stage it loses its superheat and becomes saturated. Then, before that steam can be advantageously re-expanded in a lower turbine stage it must be reheated.

In actual steam turbine operation an allowable percentage of moisture in exhaust steam is reached at a pressure too high for the steam to be sent to the condenser. To reduce this pressure, and to eectively profit by that loss in pressure, the steam is reheated and then sent to a second, and lower pressure stage of the turbine.

Reheaters proposed for these purposes have been of such construction that a large amount of complicated piping has been necessary to connect them with the communicating turbine parts. It is an object of this invention to overcome such disadvantage.

It is also an object of this invention to provide a reheater construction that is adaptable to handle the low pressure steam being reheated, with a minimum loss of pressure.

The reheating pertaining to this invention is reheating which is done by high pressure, or live steam, transferring heat to low pressure, or exhaust steam, under conditions which involve a large flow volume of the low pressure steam. The present invention aims to present a steam reheater capable of effectively treating such large volumes of low pressure steam.

It is an object of the invention to provide a steam reheater which can be installed in a steam line, and directly connected to the opposite line ends presented by the removal of a short portion of the line.

It is a further object of the invention to provide a steam reheater in which the inlet and outlet pipes for the low pressure steamy Fig. 2 is a transverse section taken on the sectional line 2 2 of Fig. l, and illustrating the relationships of the upper headers of the high pressure steam system.

Fig. 3 isa transverse section taken on the section line 3 3 of Fig. l, and illustrating the uniform distribution of the high pressure steam tubes within the inner shell.

Fig. t is a vertical sectional View illustrating the manner in which the apparatus disclosed in Fig. 1 may be partly dismantled.

Fig. 5 is a detail view embodying an enlarged reproduction of the end of one of the headers 3 as shown in Fig. l, but showing the means for suspending the header.

The illustrative reheater presents a casing 1, which is preferably cylindrical, and is arranged with its long axis transversely to the steam line in which the reheater is inserted. Preferably uniformly distributed over the central part of the interior of the casing are a number of relatively small tubes 2, communicating with the high pressure steam line 7.

Economical overhauling and advantageous flexibility in expansion and contraction are promoted by the expanding of the tubes 2 in a header structure herein shown as a number of separate headers. For example, groups of the tubes 2 at their upper ends are expanded into headers 3, shown in Fig. l as,

arranged in stepped relationship across the reheater. Similar headers i are connected to the tubes in a like manner at the base of the structure.

Connection of the lower headers 4 with the condensate collector header 8 by means of curved tubes la promotes desirable flexibility CJD as between the groups of high pressure steam tubes in their expansion and contraction movements.

The collector header 8 communicates with a reservoir or receiver 10, through the piping 9. This arrangement of elements maintains, by means of a formation in the nature of a U tube structure, a supply of condensate at the base of the high pressure steam system.

The steam and water connections 21 and 22 of the thermostat 23, are connected into the reservoir 10 as indicated in Fig. 1. The thermostat, by controlling a regulating valve 24, determines the discharge of the condensate from the reservoir 10. The regulating valve 24 may, for this purpose, control the steam supply of a turbine which runs the pump discharging the condensate from the reservoir I10, and returning it to the feed line of the high pressure boiler'. The condensate return line is indicated at 20.

In the event that the pump is electrically driven, the thermostat 23 can be directly connected to a suitable rheostat for varying the speed of the electric motor driving the pump. In either of these installations, the level of condensate in the reservoir 10 is maintained substantially constant, although it can be varied within limits if it is so desired.

Returning now to the description of the construction within the casing 1, attention is directed to the funnel shaped plate 11, which acts as a iiuid tight closure between the casing 1, and the tube bank boundary shell 12, also separating the low pressure steam inlet from its outlet. The shell guides the low pressure steam upwardly around and along the uniformly distributed tubes 2.

Within the annular chamber between the Shell 12 and the casing 1, there is a helical baffle or guide 13. This baffle and the adjoining walls of the shell 12 and the casing 1 form a passage of great flow capacity, thereby presenting a minimum of resistance to the flow of the low pressure steam through the inlet 14, around the high pressure steam to the inlet of the shell 12, that inlet being at the lower end of the shell as the structure is illustrated in Fig. 1.

With the arrangement` ust described, there is a minimum loss in pressure of the exhaust steam as it passes through the apparatus. Whatever loss occurs, is not used up in the production of eddy currents around baffles.

It is accompanied by a beneficial effect in the scouring of the walls of the passages through which the low pressure steam moves.

In the structure shown in Fig. 1, a steam and water separator isY formed by the guide 13 and the adjacent walls of the casing 1, and the steam guide shell 12. Any water here separated from the steam may be exhausted through a suitable outlet at the bottom of the apparatus, which is substantially closed to prevent pressure loss of the exhaust steam..

After passing through the inlet 14 downwardly through the aparatus, the low pressure steam proceeds along the wall formed by the headers 4 into the lower end of the shell 12. In proceeding up through the shell 12, it is iiowing in a direction generally the reverse of its downward movement in the chamber outside of that shell. The low pressure steam then passes from the upper end of the shell and through the outlet 15 into a steam line such as a line leading to a lower stage of a steam turbine installation.

In the structure indicated in Fig. 1, economical overhauling of Jthe apparatus is promoted by an arrangement which permits the high pressure steam tubes with their associated connections to be removed upwardly as a unit. F or this purpose the upper part of the casing is formed so as to be readily detachable from the main part of the casing, through the agency of abutting annular flanges 16. IVhen the headers 4 are constructed to accomplish that purpose the drain pipe leading from the header 8 is disconnected and that header, together with the headers 4 will pass up through the shell 12. I/Vhen these headers project beyond the extension of the shell 12 this shell may move as a unit with headers through the casing.

Conversely, the headers 3 may remain fixed 'l' and the easing 1 may be withdrawn downwardly over the headers 4 when the casing top is held stationary. The casing top is provided internally with a bar 24, through openings in which suspending rods 26 are preferably hooked.

By the provision of a pair of these rods for each of the headers 3, the high pr-essure steam system has a flexibility and an adaptability which enables it to respond promptly to temperature variations in the various groups of high pressure steam tubes 2. Replacement of the tubes or headers and other connections is thereby facilitated.

The high pressure steam system provided 1 with an inlet pipe 7 forms part of a fiexible connection to the inlet headers of this system. These flexible connections include the distributing header 6, and tubes 5 expanded into the headers 6 and into a. header structure shown composed of separate inlet headers 3.

By reason of the suspended mounting of the high pressure steam system, there is freedom for expansion and contraction of that system ndependently of the shell 12, or the casing 1, and other associated parts.

IlVhile this invention has been described with regard to the specific structure shown in the drawings, it is not limited thereto, but may result in variations, combinations and sub-combinations of a scope commensurate with the scope of the sub-joined claims.

Vhat is claimed is:

1. A steam reheater comprising, in combination, a casing provided with a low pressure steam inlet and a corresponding outlet, a shell spaced from the casing and open at both ends, closures for the ends of the casing spacedV from the ends of the shell, a plurality l of tubes extending through the shell and substantially uniformly spaced therein, means for guiding low pressure steam from the inlet around the shell in one direction to one end of the shell, and means forming a gas t`ght closure between the other end of the shell and the casing, the outlet communicating with said other end of the shell.

2. A steam reheater, comprising, in combination, a casing, a shell within the casing and spaced from the walls thereof, means joining the casing and shell so as to form a fluid t`ght closure for one end of the pas* sage between them, a portion of the cas-ing forming an exhaust steam inlet near the .closed end of said passage, means for conducting exhaust steam from the inlet around the shell to the open end of the shell, a casing top having an outlet for exhaust steam passing through the shell, live steam conductors extending through the shell, and means connecting said conductors with said top so that the conductors and top may be removed from the remainder of the apparatus as a unit.

3. A steam reheater for heating low pressure steam by means of high pressure steam, comprising, in combination, a. group of high pressure conductors, means for guiding the low pressure steam between the said conductors, a condensate reservoir, means for connecting said reservoir with the lower ends of the conductors to insure the wetness of those parts of the conductors. 4. A steam reheater comprising, in combination, a casing, an open ended shell located within the outer casing and spaced from the walls thereof, means oining the shell and casing so as to form a fluid tight closure for one end of the passage between them, a low pressure steam inlet near the closed end of said passage, means for conducting low pressure steam from the inlet around the shell to its open end', a casing top having an outlet for low pressure steam passing through the shell, high pressure steam conductors extending through the shell, means pendantly connecting said conductors with said top so that the conductors and top may be removed from the remainder of the apparatusas a unit.

5. A steam reheater for heating low pressure steam by means of high pressure steam comprising, in combination, a group of high pressure steam conductors, means for guiding low pressure steam between the said conductors, a condensation reservoir, means for connecting said' reservoir with the lower ends of the conductors, and means for maintaining a minimum water level in the reservoir to insure the wetness of those parts of the conductors.

6. A steam reheater comprising, in oombination, a easing provided at one end with a low pressure steam inlet and a low pressure steam outlet, a bank of high pressure steam tubes forming a dead-end heating unit, an open ended boundary shell enclosing the bank of tubes and having its ends spaced' from the corresponding ends of the casing where inlet and outlet chambers for the low pressure steam arev formed, means maintaining the shell spaced from the Casing and closing one end of the annular chamber between the casing and the shell, means in the annular chamber for directing the incoming low pressure steam in a helical path about the shell to the inlet chamber, and headers for groups of the high pressure steam tubes, some of the headers being mounted in stepped relationship in the inlet chamber and' others mounted in a similar manner in the outlet chamber.

7. In a steam reheater .employing live steam to reheat exhaust steam, a casing capable of insertion in a steam line by removal of a small part of the line, means for delivering live steam to the casing, means including headers in stepped arrangement for guiding exhaust steam through the easing so that it will receive heat from the live steam, and means formed on opposite sides of one end of the casing to afford an exhaust steam inlet on one side and an outlet for that steam on the other side.

8. In a steam reheater using live steam in a dead-end tube bank to heat exhaust steam, a condensate reservoir at the lower end of the tube bank, connections'between the reservoir and the tube bank forming a union in the nature of a U-tube juncture, a pump for exhausting the condensate from the reservoir, and a controller responsive to differences in condensate levels in the reservoir for stopping the action of the pump before the entire supply of condensate in the juncture is exhausted,

9. In a steam reheater employing' live steam to reheat exhaust steam, a bank of dead-end tubes containing the live steam, a thermostat responsive to changes in level of the supply of condensate closing the dead-ends of the tubes, an electric motor driven pump for removing the condensate, and' a rheostat influenced by the thermostat to govern the operation of the pump.

10. In a steam reheater wherein live steam is employed to transfer heat to exhaust steam, an extended casing adapted to be inserted transversely of an exhaust steam line by the removal of a short section thereof,rseparate tubes for presenting separated masses of live steam within the casing, means for reversing the flow of exhaust steam within the casing,

and' means for maintaining condensate in the lower ends of said tubes.

ll. A steam reheater comprising. in combination, a casing provided with a low pressure steam inlet and a corresponding outlet, a shell spaced inwardly from the casing wall low pressure steam from the inlet around the shell in one direction to one end of the shell, and means forming a gas tight closure between the other end of the shell and the casing, the outlet communicating with said other end of the shell and located oppositely of the inlet.

12. A steam reheater, comprising, in combination, a casing, a tube bank boundary shell within the casing and spaced from the ends and the walls thereof, means joining the casing and shell so as to form a fluid tight closure for one end of the passage between them, means forming an exhaust steam inlet into said passage near its closed end, means for conducting exhaust from the inlet around the shell in a helical path to the open end of the shell, a bank of high pressure steam tubes, within the shell, and means 'for maintaining the tubes of said bank substantially uniformly spaced.

13. In a steam reheatcr, a casing provided with an inlet for high pressure steam and an inlet and an outlet for low pressure steam, a bank of tubes Jor the high pressure steam, an inclined header structure at each end of the tube bank, a flexible tubular connection affording communication between the high pressure steam inlet and one of said header structures, a removable closure for one end of the casing, means suspending the header structures and bank of tubes from said closure, a tube bank boundary shell surrounding the bank of tubes, means to cause the low pressure steam to pass in one direction from the inlet to one end of the shell and thence through the shell in the opposite direction, and means for closing one end of the annular chamber formed between the casing and the shell.

14. In a steam reheater employing high pressure steam to heat low pressure steam, a casing provided with separate inlets for high and low pressure steam, and an outlet for the low pressure steam, a heat exchange section comprising a bank of tubes into which the high pressure steam is conducted, separate headers at the inlet of the section, a group of said tubes connected to each header, means for suspending each header at a dilerent level relative to the adjacent headers, an upright distributing header connected to the high pressure steam inlet, superposed parallel tubes connecting the distributing header to the respective separate header to form part of a flexible connection between the high pressure steam inlet and said section, a removable cover to which all of the suspending means are attached, a cylindrical tube bank boundary shell closely fitting and encasing said section, means causing the low pressure-4 rate headers at the base of said section independently movable downwardly.

15. The combination as expressed in claim 1 characterized by a group of stepped headers connected to the upper ends of the tubes, and a group of stepped headers connected to the lower ends of tubes along a line substantially parallel to the line of the upper headers.

16. The combination as expressed in claim 1 characterized by, stepped headers located above the shell and connected to the upper ends of the tubes so as to present a wall of a wide passage leading from the outlet end of the shell to the low pressure steam outlet, and stepped headers located at the lower end of the casing beyond the lower end of the shell and arranged to provide with the lower end of the shell a gradually contracted throat through which the low pressure steam passes to the shell.

CHRISTOPHER HUMPHREY DAVY.

CERTIFICATE OF CORRECT ION.

Patent No. 1,883,605. October 18, 1932.

CHRISTOPHER HUMPHREY DAVY.

Itis hereby certified that error appears in the printed specification ofthe above numbered patent requiring correction as follows: Page 3, lines 90 and91, 'claim 7, strike out the Wors "including headers in stepped arrangement" and f insert the same after "means" in line 89; page 4, line 71, e1aim14, ior "movable" read "m0vably"; and that the said Letters Patent should be read with.

these corrections therein that the same may conform te the record of the ease in the Patent Office.

Signed and sealedthis 17th day of January, A. D. 1933.

l' MJ. (Seal) Acting Commissioner of Patents.

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