US1628471A - Feed-water heater - Google Patents

Description

May 10-, 1927.- 8. A Moss FEED WATER HEATER 'Filed April 1924 inventor. Sanford A. Moss, by i His Attorney- Patented May 10, 1927.

UNITED STATES SANFORD A. MOSS, OF LYNN, MASSACHUSETTS,

ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

FEED-WATER HEATER.

Application filed April 18, 1924. Serial No. 707,517,

The present invention relates to feed water heating systems for boilers and the like, and more particularly to systems of this type in which steam, extracted froma turbine, is

utilized as ,the heating medium.

The object of my invention is to provide an improved system of this character and for a consideration of what is believed to be novel and the invention, attention is directed 1 to the accompanying drawing, description thereof and the appended ,claims.

In the drawing, the figure is a diagram- 'matical representation, partly in section, of a feed water heating system in accordance with the invention. 7

Referring to the drawing, 1 is a multistage turbine having an inlet 2 at the high pressure end through which steam is supplied and having an exhaust hood 3- at the low pressure end directly connected with a surface condenser 4 which receives the exhaust steam. The condenser has the usual hotwell 5 in which the condensed steam collects and a hot-well pump 6 for removing the condensate from the hot-well, the intake side of the pump being connected by a conduit 7 with the bottom of the hot-well.

The pump is driven by a direct-connected electric motor, as indicated at 8, although it may, in certain installations, be driven by other means. Asthe turbine 1 may and usually does form part of a'turbo-generator unit, its auxiliaries such as the pumps used in connection with the turbine condenser, ma in connection with a system'embodying t e invention, be provided with motor drive so that ower for their opera- I tion may be taken rom the turbo-generator. The motor drive of auxiliaries simplifies the layout and operation of the installation and is the preferred form of drive.

I Thedelivery side of the hot-well pump 6 a is connected by a conduit line 9 with a coiled, perforated pipe 10 located within the upper end of a sealed tank 11. The tank 11 and pipe 10 form a casing ands ray inlet nozzle respectively for a'sealed spray heater.

'- The condensate from the condenser hot-well vided in the tank sudden loss of 5 is supplied to the heater by the hot-well pump 6 through theconduit line 9, and falls '5 from nozzle 10 in a spray to the bottom of the tank. Y

The heater is mounted below and adjacent the turbine and is connected with a turbine stage in which approximately atmospheric pressure exists when the turbine is carrying normal load. In the present example such a stage is indicated at 12 and is connected with the heater by a conduit 13 leading from the bottom wall of the turbine through a removable cover late 14 at the top of the tank. Steam f i'om the stagepass'es into the heater tank by induction and condenses as it comes into contact with the s ray of condensate falling from nozzle 10.

onduit 13 is made short and of consider-- able area so that the pressure on heater, casing 11 will be substantially the same as that on the turbine stage to which it is connected.

Enough steam is withdrawn to heat the condensate up to the temperature'of the steam at the existing pressure. The condensate and condensed steam form as hot Water in the bottom of the heater tank. The hot water then serves as a supply source'for a boiler feed pump 15 to draw upon. This pump is connected with a drain basin 16 in the bottom of the tank, by a conduit 17.

Since the pressure inthe heater is substantially atmospheric, the hot-well pump 6 30 and the boiler feed water pump 15 may be of the usual type employed in connection with feed-water systems. This renders the heater readily adaptable to any turbine installation having a stage in which substantially atmospheric pressure exists at normal loads and having the usualsurface condenser and hot-well and boiler feed pumps in connection with it.

Occasions may arise which would cause a vacuum in the condenser and a consequent increase in pressure throughout the turbine. In order that the pressure within the heater casing 11 may not reach an excessive value, a relief valve 18 is pro- Cover Hand is set to-open when a pressure within the tank is reached which is in excess of that caused by the greatest overload on the turbine. The pres sure within the heater is then maintained substantially atmospheric, but the heater in terior is not connected with the atmosphere except when the relief valve 13 opens 'to relieve the pressure.

It is desirable to maintain a certain quantity of heated water in the bottom of the heater casing 11 to provide a constant supply for the boiler feed pump 15. In this connection the heater tank may be increased or decreased in size with respect to that indicated in the drawing to provide the required storage capacity. Variations in flow from the hot-well and in the demand for boiler feed water must also be provided for. In the case that the condensate from the hot-well pump is not supplied to the heater at the rate at which the boiler teed pump 15 removes the same from the heater, for example during light loads, or when startin the system, makc-up water may be supplied to the heater tank by any suitable means, preferably through a spray nozzle 19 located within the heater tank below the main spray nozzle 10. This auxiliary spray noz zle is then connected with any suitable snpply source by a conduit 20 in which, within the tank, a controlling valve 21 is located. This valve is normally closed and is operated by the movement of a float 22 connected with it by an arm 23.

When the water level is normal, that is, at somepredetermined level providing a sufficient reserve supply for the feed water pump, the float rests on the surface of the water and holds the valve 21 closed. As the water level rises above the normal value, the float continues to hold the valve closed and may become partially submerged. As the water level falls below normal, however, the float follows and opens valve 21 correspondingly, permitting the auxiliary supply to feed into the heater from nozzle 19. The spray from this nozzle is heated, like that from nozzle 10, by contact with the steam from the turbine stage. When the water level has reached the normal value, the auxiliary supply is cut off by the closing of valve 21 by the action of tloat When the. condensate supplied to the heater is in excess of that removed by the boiler feed pump, as in the case when the loud on the turbine is heavy, the water level in the bottom of the heater tank will rise. To keep the level from reaching an excessively high limit under such conditions, that is, to keep the upper limit of the water level well below the lower spray nozzle 19, an outlet valve Ql is positioned within the tank at a predetermined high water level and connected with a second or high water float 25 in such a manner that it will be opened ean ra by the float when the float is raised by a ris" ing water level. In the present example, the float is carried onv the end of an arm 26 which is pivoted in the wall of the tank to permit the float to move substantially verticallyl The valve 2st is operated by a plunger stem, the outer end of which is pivotally connected with the float arm 26. l dovement of the float is transmitted to the valve by the arm. The weight of the float is sutiicient to hold the valve closed until the float is buoyed up by the high water level. The valve is then opened and the excess water passes out of the heater through said valve and a conduit 27 connected therewith. 'lhis conduit serves to conduct the discharged water to any suitable drain (not shown). The outlet of the conduit is provided with a, check valve 28 to prevent inrush of air to the heater in case the pressure therein falls below atmospheric pressure while the valve 24: is open. The conduit 27 is formed as a stand pipe having a vertical section 29 ot' su'llicient length to provide a pressure head which will insure the discharge of excess water from the heater tank a ainst atmospheric pressure. The heater tank is provided with a water gauge 30 through which the water or condensate level may be observed.

The boiler feed water pump 15 is, in the present example, driven by a direct connected motor 31, this being at present considered the most desirable form of drive as mentioned in connection with hot-well pump 6. The discharge or delivery side of pump 15 is connected with a delivery conduit 32 which leads to a boiler (not shown) in which the heated condensate is to be used. A valve 33 is inserted in this conduit to regulate the flow of condensate or feed water from the pumps As the pressure in the heater issubstantially atmospheric, the boiler feed" pump may be that ordinarily and regularly used in a boiler feed water line. The same pump may thus be used to remove the-heated mixture from the heater and to supply the boiler.

In connection with the extraction of steam from the turbine stage 12, means are provided for trapping moisture or water entrained in the steam and delivering the same to the heater. In the present example the conduit 13, connecting the turbine stage 12 with the heater, leads into an annular trough or groove 3-1 formed within the turbine casing. #This groove is provided on the low pressure side of the stage with a sharp annular rib covering the ends of the buckets in such a manner that water thrown off by the buckets is caught thereby, separated from the steam flow, and'directed into the lit) groove 34:. From the groove 34 the water or moisture is conducted into the outlet con duit 13 and passes into the heater. The heat contained in the water removed from the dicated at 41 and its discharge at 41". In

stage is thus added to the condensate in the heater and the efliciency of the succeeding turbine stages is appreciably increased by the removal of the.entrained water. The

heater casing 11 is provided with an auxiliary inlet conduit 35 through which additional heating steam may be supplied to the heater.

The condensate supplied to the sealed spray heater 11 by the hot-Well pump 6, and the boiler feed Water delivered to the boiler feed water line 32 by boiler feed pump 15 is heated by one or more heaters of the closed or pressure type inserted in the condensate and boiler feed water lines. In the present example one heater of this type is provided in each of said lines and supplied with heating steam from suitable turbine stages, a high pressure heater being connected with a high pressure stage of the turbIne to heat the boiler feed water and a low pressure heater being connected with a low presure stage to heat the condensate from the hot-well.

In this arrangement 36 is a high pressure stage and 37 is a low pressure stage, provided with annular fluid-directing ribs 38 and grooves 39 after the manner of the atmospheric pressure stage 12. The ribs and grooves in each of these stages serve as a separating means for removing from the steam the entrained water of condensation,

and may be regarded as representing any suitable separating means adapted for use in a turbine stage. The water of condensation, together with the steam, passes from each of these stages through conduits leading from the lowermost points in the grooves 39. Each of said conduits is connected with and discharges into a casing forming-a closed heater chamber.

The high pressure stage 36 is connected by a conduit 40 with a high pressure closed heater 41. This heater is a surface type heater as opposed to the sealed spray heater 11 and may be of any suitable type. It is interposed in conduit 32, its inlet being inthe present instance the usual heater tubes are indicated diagrammatically at 42. The steam condenses in imparting its heat to the feed water in tubes 42 and, together with the water extracted from the stage, forms in the bottom of the heater as condensate.

This condensate is returned to the next lower stage heater, in this case to the sealed spray heater 11, by a conduit 43 controlled by a suitable steam trap The steam trap is set to discharge before the water level reaches the lowermost horizontal portion of the tubes 42. The residual heat contained in this water is thus added to the feed water supply in the heater tank 11.

The low pressure stage 37 discharges through a conduit 45 into a similar closed. heater 46, this being designated as a low pressure heater. In this heater the tubes are indicated at 47. The steam extracted from stage 37 condenses in imparting its heat to the water flowing through tubes 47 ter or hot-well condensate, it will be readily appreciated that additional heaters may be added in the same manner as those shown either to the higher or the lower pressure stages of the turbine. The heating system shown in the present example should be taken only as an illustration of one embodiment of the invention, being that which is at present considered the most desirable.

The, auxiliary-heaters 41 and 46ers most readily adapted to heating the hot-well condensate and boiler feed water and hence have been shown as being utilized for that a purpose.

In accordance with the invention, it will be seen that a sealed spray heater is associated with a stage of a turbine in which the pressure is nearly atmospheric under all load conditions, and that the casing of this heater is connected directly with the turbine casing. By this means the pressure in casing 1 1 will be the stage pressure in stage 12 of the turbine at all times.

The hot-well pump is connected between the spray heater and the condenser, and delivers the entire condensate as rain or spray into the heater. Since the region into which the s ray is discharged is at or about atmosp leric pressure, the type. of hot-well pump ordinarily used in connection with surface condenser installations is entirely suitable and no extra pump or special met-ha nism is required. The hot-wellpulup itself is used to supply the heater.

On the way -to the atmospheric pressure heater, the condensate from the hot-well is passed through tubes in one or more closed heaters connected with one or more turbine stages between that to which the atmospheric pressure heater is connected and the condenser end of the turbine. The condensate produced in each heater is passed to the next lower stage heater through a suitable steam trap and in the case of the last or lowermost heater, to the interior of the condenser.

The liquid in the sealed spray heater, from which the boilerfeed water. is-taken, consists of condensate from the turbine stage with which it is connected, heated water from the hot-well pump and condensate from any heater between this point and the upper end of the turbine. This liquid passes into the boiler teed pump and is pumped by it directly to the boiler. The ordinary type of boiler feed water pump may be utilized. in connection with the sealed spray heater, thus eliminating any special pu mp or appliance.

The boiler feed water on its way from the spray heater to the boiler is passed through one or more closed heaters using steam extracted from the higher pressure stages of the turbine. The condensate from each of these heaters is passed to the next lower heater and from the last one to the sealed spray heater through suitable steam traps.

The teed water for a boiler provided by a system in accordance with the invention comprises 1. Water furnished by the hotwell pump.

2. Condensation from steam in the sealed spray heater.

3. Entrained moisture thrown out from the turbine stage connected with the sealed spray heater.

4. Make-up water if necessary.

5. Entrained 'moisture thrown out from the turbine stages connected with the closed pressure heaters.

6. Condensate from any other source fed into the system at any suitable point.

Thus, it will be seen that provision is made for utilizing heat from all available sources to heat the feed water, without resorting to complicated apparatus and without making any material changes in the apparatus ordinarily used with boiler feed systems not involving a heating means.

In accordance with the: provisions of the patent statutes, the principle of operation of the invention has been described, together with the apparatus which is now considered to represent the best embodiment thereof, but it should be understood that the apparatus shown is only illustrative and that the invention may be carried out by other means.

\Vhat I claim as new and desire to secure by Letters Patent of the United States, is:

l. A spray heater for use with a multistage extraction steam turbine for heating feed water, comprising a closed tank adapted to contain a supply of heated liquid, an inlet conduit of relatively large cross section connected with the tank through which is admitted extraction steam of substantially atmospheric pressure, a spray inlet nozzle in the tank through which liquid to be heated is supplied, a second spray inlet .nozzle in the tank, means connected with the secondnamed nozzle for supplying thereto additional liquid to be heated, and a conduit connected with the tank for conducting therefrom excess liquid, said conduit having an extension below the point of connection with the-tank providing a vertical length eaaavi.

suilicient to. create a liquid head having a pressure greater than atmospheric pressure.

2. A spray heater for use with a multistage extraction steam turbine for heating feed water, comprising a closed tank adapted to contain a supply of heated liquid, an inlet conduit of relatively large cross section con.- nected with the top of the tank through which is admitted extraction steam of substantially atmospheric pressure, a spray inlet nozzle in the tank adjacent the top through which liquid to be heated is sup plied, a second spray inlet nozzle in the tank. below the first-named nozzle, a. conduit connected with the second-named nozzle for supplying thereto additional liquid to be heated, a normally closed valve in said conduit, means responsive to a certain low liquid level in the tank for opening said valve, a conduit connected with the tank for conducting theretrom excess liquid, said conduit having an extension below the point of connection with the tank providing a vertical length sufficient to create a liquid head having a pressure greater than atmospheric pressure, and a delivery conduit connected with the tank for conducting heated liquid therefrom.

3. A spray heater for use with an elastic fluid prime mover which provides extraction heating fluid at substantially atmospheric pressure, comprising a closed tank adapted to contain a supply of heated liquid and provided with a heating fluid inlet conduit, means for supplying a ray of liquid to be heated to the interior 0% the tank, an auxiliary supply conduit connected with the tank for supplying thereto additional liquid to be heated, a normally closed valve in said conduit, means responsive to changes in the li uid level in the tank connected with said va ve to open the same when a certain lower-than-normal level is reached, and an outlet conduit connected with the tank for withdrawing excess liquid therefrom, said conduit having an extension below the tank of a vertical length sufficient to create a liquid head having a pressure greater than that of the atmosphere.

4. A spray heater for use with an elastic fluid prime mover which provides extraction heating fluid at substantially atmospheric pressure, comprising a closed tank adapted to contain a supply of heated liquid and provided with an inlet conduit through which is supplied said heating fluid, means for supplying a spray of liquid to the interior of the tank in contact with the heating fluid whereby the liquid is heated, an auxiliary supply conduit connected with the tank for supplying thereto additional liquid toibe heated to maintain a storage of liquid in the tank, a normally closed valve in said conduit, means responsive to chan liquid level in the tank connecte with said es in the Y duit connected with the tank for withdraw ing excess liquid therefrom, said conduit having an extension below the tank of a Vertical length sufficient to create a liquid head having a pressure greater than that of the atmosphere, a non-return valve in said conduit which direction. of the prevents flow therein in-the tank, and a delivery conduit 10 connected with the tankfor conducting heated fluid therefro In Witness Whereof,'I have hereunto set my hand this 15 .day of April, 1924:.

SANFORD A. Moss.

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