US2871832A - Novel method relating to steam generators - Google Patents

Description

Feb. 3, 195s F. l. EFLEY 2,871,832

} NOVEL METHOD RELATING TO STEAM GENERATORS Filed March 12, 1956 INVENTOR.

Frederic I. Epley BY 14 fi ATTORNEY 6 Sheets-Sheet 1 I Feb. 3, 1959 F. EPLEY NOVEL METHOD RELATING TO STEAM GENERATORS Filed March 12, 1956 6 Sheets-Sheet 2 INVENTOR.

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ATTORNEY Feb. 3, 1959 F. I. EPLEY NOVEL METHOD RELATING TO STEAM GENERATORS Filed March 12, 1956 6 Sheets-Sheet 3 INVENTOR.

4 o k 6 A, 6 a W 4 L 5 i 2 5 a a b M C 6 0 u a a a Frederic l. Epley JTTORNEY Feb. 3, 1959 F. l. EPLEY NOVEL METHOD RELATING TO STEAM GENERATORS Filed March 12, 1956 6 Sheets-Sheet 4 INVENTOR.

Frederic l. .Epley Fig. 5.

JTI'ORNEY Fe 3, 1 59 F. l. EPLEY 2,871,832

NOVEL METHOD'RELATING T0 STEAM GENERATORS Filed March 12, 1956 6 Sheets-Sheet 5 INVENTOR.

Frederic l. Epley Fig. 7.

BY (161M A- ATTORNEY Feb. 3, 1959 Filed March 12,1956

F. l. EPLEY 2,871,832

NOVEL METHOD RELATING TO STEAM GENERATORS 6 Sheets-Sheet 6 INVENTOR.

Frederic l. Epley ATTORNEY United State Patent NOVEL METHOD RELATING TO STEAM GENERATORS Frederic I. Epley, Rockville Centre, N. Y., assignor to Combustion Engineering, Inc., New York, N. Y., a corporation of Delaware Application March 12, 1956, Serial No. 570,807

1 Claim. (Cl. 122-4) tremely difficult and as a practical matter impossible to predetermine with precise accuracy the exact quantity of surface necessary to produce the design or required superheat and reheat temperature at the desired or maXimum'load. Furthermore, during operation of the unit the furnace tubes become coated with foreign matter which cannot be removed by soot blowing or other such means so that the heat transfer rate through the tube wall decreases and accordingly the heat absorbing capacity of the furnace will decline causing higher temperature gases to pass over the superheater and reheater thereby raising the superheat and reheat temperature relative to that which originally prevailed for a given load and accordingly making a unit which will have originally been substantially perfectly balanced grossly out of balance. At times it thus becomes necessary to decrease the heat absorbing capacity of the superheater and/or reheater of a steam generator with it being required to effect this decrease without materially changing the heat absorbing capacity of the entire unit in order that the operatingefficiency of the unit may be maintained with this decrease in heat absorption of the superheater and/ or reheater not resulting in a substantial decrease in operating efficiency of the unit. The present invention is directed to a novel method for effecting this result in a most expeditious and economical manner.

The method of this invention is applied to a steam generator having a steam heating means comprised of numerous tubular elements which are subjected to the heating medium of the steam generator and which generator has the usual economizer for heating the feed water introduced into and passed through the steam generating circuit of the steam generator. In accordance with the invention a sufficient number of the tubes of the steam heater are disconnected from the steam heater supply and discharge means (headers) in order to effect the required reduction in heat absorbing capacity of the steam heater and these thus disconnected tubes are then connected in situ so that they become economizer surface thereby effectively preserving the heat absorbing capacity of the generator while decreasing the heat absorbing capacity of the steam heater.

It is an object of the present invention to provide an improved method of decreasing the heat absorbing capacity of the superheater and/ or reheater of a steam generator without materially affecting the operating efficiency of the generator. Other and further objects of the invention will become apparent to those skilled in the art as the description proceeds.

T he invention will be more fully understood from the following description when considered in conjunction with the accompanying drawing forming a part thereof and in which:

Fig. 1 is a vertical sectional view somewhat diagrammatic, of a steam generator capable of having the method of this invention incorporated therewithin.

Fig. 2 is a detailed view of the low temperature section of the superheater and the economizer of this generator and showing the arrangement thereof prior to the application of the method of this invention.

Fig. 3 is a top plan view taken from line 33 of Fig. 2.

Fig. 4 is a vertical section taken along line 44 of Fig. 2.

Fig. 5 is a view similar to that of Fig. 2 but showing the low temperature superheater and economizer after application of this method of the invention.

Fig. 6 is a top plan view taken from line 6-6 of Fig. 5 and showing the interconnection of what were formerly superheater tubes with the outlet headers of the economizer.

Fig. 7 is a sectional view taken along line 77 of Fig. 5 showing the interconnection of the additional stub headers with the economizer inlet heaters and the former superheater tubes and the connection of these former superheater tubes with the economizer outlet headers.

Fig. 8 is a perspective view showing in detail the connection of the former superheater tubes with the economizer outlet header.

Referring now to the drawings wherein like reference characters are used throughout to designate like elements and particularly to Figs. 1, 2 and 3, there is shown therein a steam generator designated generally 10 and which includes a furnace 14 the inner surface of the walls of which are lined with steam generating tubes 16 with the furnace being supplied with fuel and air through the burners 18. A portion of the water in steam generating tubes 16 is converted to steam and the steam and Water mixture passes from the upper ends of these tubes into drum 24 wherein the steam is separated from the water with the water passing downward from drum 24 through downcomers 26 and back into and through tubes 16 with a forced circulation of this Water being provided in the illustrative organization by means of pump 30.

The combustion gases generated in furnace 14 by the burning fuel pass upwardly through the furnace and into the gas pass or passageway 32 which is rectangular in transverse section and communicates with laterally disposed outlet 34 located in the upper region of the furnace. Disposed within the passageway 32 is the superheater of the generator which is divided into two sections that are in serial steam flow relation with low temperature section 36 being disposed in the upper portion of the vertical leg of passageway 32 while the high temperature section 38 is disposed in the horizontal leg of this passageway so'that the combustion gases flow serially over the high temperature and low temperature sections respectively. Saturated steam is supplied to low temperature section 36 from drum 24 through conduits 40 (one being shown) which interconnects this drum with the header 42. Extending from header 42 are the supply conduits 44 which extend downwardly within passageway 32 along the inner surface of the front and rear walls 46 and 48, respectively, of this passageway with the lower ends of these conduits being connected to the two inlet headers 50 of the low temperature section of the superheater.

This low temperature section 36 is comprised of numerous sinuously bent tubes 52 disposed in side-by-side spaced relation across the width of passageway 32 with alternate of these tubes being connected with a different one of the inlet headers 50 and with the upper ends of the tubes being connected with the outlet headers 54. After passing through low temperature section 36 the then partially superheated steam is conveyed from outlet header 54 through conduit 56 to the high temperature section 38 of the superheater where the required degree of superheat is imparted to the steam so that it is at its desired temperature and pressure upon emerging from this section of the superheater. After a portion of the-energy of this steam has been utilized it may be returned for re heating in reheater 57 which is disposed in passageway 32 between the high and low temperature sections of the superheater and is constructed in a manner similar to the superheater.

Positioned downstream of low temperature superheater section 36 relative to combustion gas flow through the steam generator is the economizer 58 which is comprised of numerous sinuously bent tubes disposed in spaced relation across passageway 32 with the planes within which the economizer tubes are disposed being at 90 relative to those within which the low temperature super-heater tubes are disposed. Alternate of the economizer tubes extend upwardly along the inner surface of an opposite one of the side walls 6% of passageway 32 so that these side walls are effectively lined with economizer tubes. Feed water is supplied to economizer 58 from the spaced inlet headers 62. with alternate tubes of the economizer being connected to opposite of these headers and with the headers being supplied by feed pumps in the conventional manner. The opposite ends of the tubes of the economizer are connected into one of the two outlet headers 64 and the feed water is conveyed from these outlet headers of the drum 24 through conduits 66.

With the organization shown in Figs. 2 and 3 all to the sinuously bent tubes 5'2 that are connected intermediate one of the inlet headers 50 and the outlet header 54 of the low temperature superheater section 36 so that these tubes as a group make up or form this section of the superheater.

In order to compensate for minor variations of heat input to the superheater steam above that theoretically required to give the proper superheat temperature at any given load and accordingly in order to maintain the superheat temperature substantially constant a desuperheater 68, which may be of the spray type, is interpositioned between the low temperature section 36 and high temperature section 38 of the superheater. By means of this desuperheater the temperature of the superheated steam may be lowered and accordingly maintained substantially constant even though the heat input to the superheater is greater than that required to give the proper superheater temperature. However, the use of dcsuperheater 56 lowers the overall operating ethciency of the steam generator and when the magnitude of desuperheating necessary to maintain the temperature at its desired value is such as to substantially lower the operating efficiency of the unit it becomes necessary, as mentioned hereinbefore, to decrease the heat input to the superheater to thereby decrease the amount of desuperheating that is necessary. In order to preserve the operating etficiency of the unit when making this change, however, it is of course necessary that the heat absorbing capacity of the entire steam generator remain generally the same.

In accordance with the present invention these objectives are accomplished in a most expeditious and economical manner by converting what was formerly superheater surface to economizer surface with sufficient of the surface being so changed as to give the required reduction of heat input to the superheater. Figs. 4, 5 and 6 show the steam generator of Figs. 1, 2 and 3 after it has been changed in accordance with the method of the invention. In making this change suflicient of the tubes 52 of low temperature superheater section 36 are disconnected from the inlet headers 50 and the outlet headers 54 with a number of the outermost tubes of this superheater section being so disconnected in the illustrative arrangement of Figs. 4-7 and identified as 55 in Fig. 7. The inlets of these disconnected tubes are then connected to one of the stub headers 70 which are disposed in passageway 32 for this purpose and which are connected through conduits 72 to one of the inlet headers 62 of the economizer. The outlets of these disconnected tubes 52 are connected with one of the outlet headers 64 of the economizer as shown so that these tubes become part of the economizer of the steam generator with Figs. 5, 6 and 7 indicating this connection while Fig. 8 shows in detail how it is effected.

It is preferable to convert in this manner the portions of the superheater through which relatively low temperature steam is passing so that there will not be a greater variation than necessary in the temperature differential between the stream of the combustion gases and the steam passing through the tubes prior to the conversion and the temperature differential between these gases and the feed water flowing through the tubes after the conversion is accomplished since if this variation in temperature differential is not too great the variation in heat absorption for the entire unit will not be changed to any substantial extent even though feed water is flowing through tubes through which superheated steam originally passed. It is "for this reason as well as because of the mechanical ease by which the physical change may be made that a portion of the surface of the low temperature superheater in the organization shown is converted into economizer surface.

By means of this change in function of a portion of the surface of the steam generator the heat input to the superheater is decreased, as desired, to bring the unit into balance so that the proper superheat temperature is obtained at any given load with a minimumof desuperheating being required and at the same time the overall heat absorbing capacity of the steam generator is not materially changed with the temperature head between the feed water flowing through these formerly superheater tubes and the combustion gases being sufiiciently near to that which prevailed between the superheated steam and the combustion gases so that the change in heat absorption incident to this change in heat head is not sufiiciently great to make any substantial difference in efficiency of operation. Thus with a minimum of apparatus change and accordingly a minimum cost and outage time of the unit the necessary change required to bring the heat absorbing capacity of the superheater balance is effected with applicants method.

It will be understood that the above description is intended for the purpose of illustration only and that modifications such as will occur to those skilled in the art are possible and are embraced within the scope and spirit of the invention.

What I claim is:

In a vapor generator having a furnace that has its walls lined with steam generating tubes and an off-take for combustion gases extending therefrom having a tube bundle disposed therein forming a convection superheater with the tubes interconnected between inlet and outlet headers and a tubular economizer downstream of the superheater relative to combustion gas flow with this organization being such that a decrease in radiant heat absorption in the furnace causes an increase in the rate of heat absorption of the superheater, the method of maintaining the rate of heat absorption of the superheater within a predetermined range for a given load and counteracting the effect of a decrease in radiant heat absorption in the furnace that increases this rate comprising disconnecting only a small number of the superheater tubes from the inlet and outlet headers, the number being sufiicient to bring this heat absorption of the References Cited in the file of this patent UNITED STATES PATENTS La Mont Aug. 28, 1934 Andrews et a1. June 22, 1954

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