US2707457A - Air heating system for power generators - Google Patents

Description

y 3, 1955 J, H. BAYARD 2,707,457 AIR HEATING SYSTEM FOR POWER GENERATORS Filed April 22, 1950 Fit 0 W67 INVENTOR.

United States Patent AIR HEATING SYSTEM FOR POWER GENERATORS Julius H. Bayard, Charleston, S. C., assignor to Foster Wheeler Corporation, New York, N. Y., a corporation of New York Application April 22, 1950, Serial No. 157,544 6 Claims. (Cl. 122-1) This invention relates to heat exchange apparatus and more particularly to a preheater system for a vapor generator.

It is usual in vapor generators to heat feed water therefor in an economizer positioned in heat exchange relationship with gases from the furnace of the vapor generator which, in turn, lowers the temperature of said gases. If the temperature of the feed water entering the economizer is of such degree that the heat removed from the gases does not lower the gas temperature to the desired degree an air heater is positioned in heat exchange relationship with gases beyond the economizer in the direction of flow of the gaes. Since the specific heat of the exhaust gases in relationship to the air is low, the size of the air heater is normally very large.

In accordance with the present invention, a portion of the feed water, all of which water is normally preheated to a degree less than the desired final temperature in a feed water heater by indirect heat transfer from steam, for example from the exhaust steam of a turbine, is passed in indirect heat exchange relationship with air to be used to support combustion in the furnace of a vapor generator, or for other uses. The portion of the feed water passing in heat exchange relationship with the air is cooled as the air is heated. After cooling in the air heater, said one portion of the feed water is passed to the inlet of one section of an economizer which economizer comprises two sections, said one section of the economizer being located beyond the other section of the economizer in the direction of flow of combustion gases from the furnace so that said gases pass in heat exchange relationship with said other section prior to passing in heat exchange relationship with the one section. In flowing through said one section of the economizer, the one portion of the feed water is reheated and regains a part or all of the heat given up to the air flowing through the air heater. Since said one portion of the feed water is relatively cool when it enters the one sec tion of the economizer, the gas temperature of the combustion gases from the furnace is greatly reduced as it passes in heat exchange relationship with said one section of the economizer. After flowing through the one section of the economizer, said one portion of the feed water is passed into the other section of the economizer together with the other portion of the feed water passing from the feed water heater. Both portions of the feed water then flow through said other section of the econornizer and thence into the vapor generator. A proportioning control valve is provided for controlling the portion of the feed water flowing to the air heater and the portion flowing directly to said other section of the e'conomizer.

The present invention provides apparatus for preheating feed water and preheating air for a vapor generator in which the temperature of the flue gases of a vapor generator may be controlled and in which expansion tanks and the like are not necessary.

This invention also provides apparatus for preheating 2,707,457 Patented May 3, 1955 air and feed water for a vapor generator in which separate feed water pumps are not required and in which the possibility of air heater fires are greatly reduced and in which the air heater may be positioned in any desired location.

The invention will be understood from the following description when considered in connection with the accompanying drawing forming a part thereof and in which the single figure is a somewhat diagrammatic transverse vertical section of the apparatus of the present invention.

Referring to the drawings, the apparatus of the pres ent invention is disclosed as embodied in a vapor generator comprising a setting 10 having vapor generating surface therein with an upper steam and water drum 11 associated therewith together with a lower water drum 12 in the lower part of the setting in substantial vertical alignment with said upper drum. Drums 1]. and 12 are connected by a substantially vertical bank of steam generating tubes 13 having a central battle 14 extending from said lower drum upwardly to a point short of the upper drum. At one side of the bank of tubes 13 is a furnace or combustion chamber 15 fired, as shown, by a plurality of burners 16. The root and side wall of chamber 15 is lined by water tubes 17. At the opposite side of bank 13 is a gas outlet passage 18 which communicates with gas inlet 19 of flue or stack 20. The flue has a gas outlet 21 which acts as a gas outlet for the setting.

An economizer 22 having an upper or one section 23 with a feed water inlet 24 and a feed water outlet 25 is positioned in flue 20. Economizer 22 has a lower or other section 26 over which gases from gas passage 18 pass prior to flowing in heat exchange relationship with upper section 23. Lower section 26 of the economizer has a feed water inlet 27 and a feed water outlet 28. Feed water outlet 28 is in communication with the water space of drum 11 through a conduit 29.

As shown, feed water to be used in the vapor generator, which feed water may be condensate from a con-' denser, not illustrated, enters a feed water preheater 30 through a feed conduit 31 and fiows through a plurality of tubular members 32 in said heater. The water flowing through tubular members 32 is heated by steam, for example steam exhausted from a turbine, not shown, which steam enters the feed water preheater through steam in let 33 and passes therefrom through outlet 34 after flowing in heat exchange relationship with tubular members 32. Feed water heated by flowing through tubular members 32 passes from the preheater through an outlet conduit 35 and into the inlet of feed liquid flow controlling means which, as shown, is a proportioning control valve illustrated diagrammatically at 36. Control valve 36 has a proportioning valve member 37 which is operable to proportion the feed water between an economizer feed line 38 and an air heater feed line 39. Economizer feed line 38is in communication at one end thereof with one outlet of valve 36 and at the opposite end with inlet 27 of economizer section 26, while air heater feed line 39 is in communication at one end thereof with another outlet of valve 36 and at the opposite end with inlet 40 of an air heater 41.

Air heater 41 comprises a plurality of tubes 42 extend ing transversely of air conducting means or air conduit 43. Adjacent tubes are connected by return bends 44 and 45 so that feed water entering the air heater through inlet 40 passes in a continuous path of flow from the lower tube to the upper tube thereafter to pass from the air heater at outlet 46. As shown, tubes 42 have extended surface members 47 thereon. Air conduit 43 is in communication above air heater 41 with a source of air to be heated and extends below said air heater and into communication with the furnace 15 through burners 16.

Feed Water which has passed through air heater 41 flows therefrom through outlet 46 and into the one section 23 of economizer 22 through conduit 43 which communicates at one end with outlet 46 and at the opposite end with inlet 24- of economizer section 23. Feed water which enters section 23 of economizer 22 through inlet 24 flows therethrough and thence into section 26 through outlet 25, conduit 49 and economizer feed line 38.

In operation, gases of combustion from combustion chamber 1.5 flow therefrom into bank of tubes 13 and are directed upwardly by baflie 14 over some of the tubes thence downwardly over the remainder of the tubes and into gas passage 18. From gas passage 18, the gases flow through outlet 19 thence in heat exchange relationship with the tubes of economizer section 26 and thereafter in heat exchange relationship with the tubes of economizer section 23.

Feed water to be heated for the vapor generator passes into feed water preheater 30 through feed conduit 31 and is heated therein thereafter to pass therefrom into outlet conduit 35. Proportioning control valve 36 is set so that a desired portion of the heated feed water passes directly to economizer portion 26 and another desired proportion of the heated water flows to air heater 41.

By controlling the proportion of feed water passing through air heater feed line 39 and through air heater 41 to economizer section 2.3 through conduit 48, the temperature of the flue gases passing through outlet 21 may be controlled. The feed water passing through air heater 41 is cooled considerably by the air flowing through conduit 43, said water entering economizer section 23 at a relatively low temperature. For example, the temperature of the feed water passing into proportioning control valve 36 would be approximately 390 F. and would pass through economizer feed line 38 thereafter to enter economizer section 26 at approximately that temperature. The proportion of the feed water flowing through valve36 into air heater 41 would enter the air heater at approximately 390 F. and would be cooled in the air heater to approximately 180 F. at outlet 46 by air which enters conduit 43 at about 100 F. and after flowing in heat exchange re lationship with tubes 42 of air heater 41 enters the furnace or combustion chamber 15 through burners 16 at substantially 340 F. The feed water entering section 23 through conduit 48 would therefore be at approximately 180 F. Exhaust gases entering flue gas inlet 19 of the flue 20 would be, for example, 600 F. and first flow over economizer section 26 and thereafter over economizer section 23 thereby becoming cooled to approximately 320 F. at flue outlet 21. 23 would be passed into conduit 38 at substantially 390 P. which would be approximately equal to the temperature of the proportion of the feed water flowing from valve 36 through economizer feed line 38 to economizer Feed water flowing through section section 26. All of the feed water entering economizer section 26 would, therefore, be at substantially 390 F. and would be heated to approximately 460 F. at outlet 28 of economizer section 26.

Inasmuch as changes may be made in the form, location and relative arrangement of the several parts of the apparatus disclosed without departing from the essential characteristics of the invention, it will be understood that the invention is not to be limited excepting by the scope of the appended claims.

What is claimed is:

1. In vapor generating apparatus comprising a vapor generator having a setting, a furnace in the setting, means for firing the furnace, said setting having a gas outlet in communication with the furnace and through which gases of combustion flow from the setting, vapor generating surface in the setting in heat exchange relationship with said gases of combustion prior to the flow of said gases from the setting gas outlet, aneconomizer for heating liquid for said vapor generating surface, the economizer being positioned in heat exchange relationship withgases of com bustion flowing from the setting after passing in heat exchange relationship with said vapor generating surface, the economizer having a plurality of sections, one section thereof being positioned beyond another section in respect to the flow of said gases to the setting gas outlet, said economizer sections each having an inlet through which liquid enters the section and an outlet through which liquid passes from the section after flow therein, the outlet of said one economizer section being in communication with the inlet of said other economizer section, conduit means communicating with the outlet of said other economizer section and the vapor generating surface, an air heater comprising air conducting means through which air to be heated flows and a tubular path of flow having a liquid inict and a liquid outlet, the liquid outlet being in communication with the inlet of said one economizer section, said tubular path of flow being disposed in heat exchange relationship with air passing through said air conducting means, a feed liquid preheater having a feed liquid inlet through which feed liquid to be heated enters the heater and a feed liquid outlet through which heated feed liquid flows from the heater, an economizer feed liquid conduit in communication with the inlet of said other economizer section and with said preheater outlet, an air heater feed liquid conduit in communication with the inlet of the air heater tubular path of flow and with said preheater outlet, and control means for controlling the flow of heated feed liquid from said preheater to the air heater tubular flow path and from said preheater to said other economizer section.

2. In vapor generating apparatus comprising a vapor generator having a setting, a furnace in the setting, means for firing the furnace, said setting having a gas outlet in communicating with the furnace and through which gases of combustion flow from the setting, vapor generating surface in the setting in heat exchange relationship with said gases of combustion prior to the flow of said gases from the setting gasoutlet, an economizer for heating liquid for said vapor generating surface, the economizer being positioned in heat exchange relationship with gases of combustion flowing from the setting after passing'in heat exchange relationship with said vapor generating surface, the economizer having a plurality of sections, one

section thereof being positioned beyond another section in respect to the flow of said gases to the setting gas outlet,

said economizer sections each having an inlet through which liquid enters the section and an outlet through which liquid passes from the section after flow therein, the outlet of said one economizer section being in communication with the inlet of said other economizer section, conduit means communicating with the'outlet of said other economizer section and the vapor generating surface, an air heater comprising air conducting means through which air to be heated flows and a tubular path of flow having a liquid inlet and a liquid outlet, the liquid outlet being in communication with the inlet of said one economizer section, said tubular path of flow being disposed in heat exchange relationship with air passing through said air conducting means, a feed liquid preheater having a feed liquid inlet through which feed liquid to be heated enters the heater and a feed liquid outlet through which heated feed liquid flows from the heater, an economizer feed liquid conduit in communication with the inlet of said other economizer section and with said preheater outlet, an air heater feed liquid conduit in communication with the inlet of the air heater tubular path of flow and with said preheater outlet, and a liquid proportioning control valve so disposed in relationship to said preheater outlet as to control the proportionof heated feed liquid flowing from said preheater to the air heater tubular flow path inlet and to the inlet of said other economizer section.

3. In vapor generating apparatus comprising a vapor generator having a setting, a furnace in the setting, means for firing the furnace, said setting having a gas outlet in 6 communication with the furnace and through which gases of combustion flow from the setting, vapor generating surface in the setting in heat exchange relationship with said gases of combustion prior to the flow of said gases from the setting gas outlet, an economizer for heating liquid for said vapor generating surface, the economizer being positioned in heat exchange relationship with gases of combustion flowing from the setting after passing in heat exchange relationship with said vapor generating surface, the economizer having a plurality of sections, one section thereof being positioned beyond another section in respect to the fiow of said gases to the setting gas outlet, said economizer sections each having an inlet through which liquid enters the section and an outlet through which liquid passes from the section after flow therein, the outlet of said one economizer section being in communication with the inlet of said other economizer section, conduit means communicating with the outlet of said other economizer section and the vapor generating surface, an air heater comprising air conducting means through which air to be heated flows and a tubular path of flow having a liquid inlet and a liquid outlet, the liquid outlet being in communication with the inlet of said one economizer section, said tubular path of flow being disposed in heat exchange relationship with air passing through said air conducting means, a source of heated feed liquid, an economizer feed liquid conduit in communication with the inlet of said other economizer section and with said source, an air heater feed liquid conduit in communication with the inlet of said air heater tubular path of flow, and control means for controlling the flow of preheated feed liquid from said source to the air heater tubular flow path and from said source to the other economizer section.

4. In vapor generating apparatus comprising a vapor generator having a setting and a saturated vapor space, a furnace in the setting, means for firing the furnace, gas passage forming means in communication with the furnace to receive gases of combustion therefrom, an

economizer in said passage in heat exchange relationship 1 with gases flowing therethrough, the economizer having a plurality of sections, one of said sections being positioned beyond another section in the direction of flow of gases through the passage, the outlet of said one economizer section being in communication with the inlet of said other economizer section, the outlet of said other economizer section communicating with said vapor generator, an air duct in communication with said furnace to conduct heated air thereto, tubular means arranged to form a tubular path of flow and disposed in heat exchange reiationship with said air flowing to the furnace, the outlet of said tubular path of flow being in communication with the inlet of said one economizer section, means for preheating feed liquid, said last-mentioned means being in communication with the inlet of said other economizer section so as to deliver heated feed liquid thereto, said inlet of the tubular flow path also being in communication with the preheated feed liquid means to receive heated feed liquid therefrom, and control means constructed and arranged to control the flow of preheated feed liquid from the preheated feed liquid means to said tubular flow path and also to the other economizer section.

5. The apparatus of claim 4 wherein the control means comprises a movable liquid proportioning control valve so disposed in relationship to said preheated feed liquid means as to control the proportion of preheated feed liquid flowing therefrom to the tubular flow path and to other economizer section said valve being movable in one direction to increase the flow of liquid to the tubular flow path while decreasing the flow to said other economizer section and movable in another direction to decrease the flow of liquid to the tubular flow path while increasing the iiow to said other economizer section.

6. in vapor generating apparatus comprising a vapor generator having a setting and a saturated vapor space, a furnace in the setting, means for firing the furnace, gas passage forming means in communication with the furnace to receive gases of combustion therefrom, an economizer for heating liquid for said vapor generator, the economizer being positioned in heat exchange relationship with gases of combustion flowing from the setting after passing in heat exchange relationship with said vapor generator and comprising a plurality of sections, the outlet of one economizer section being in communication with the inlet of the other economizer section, the outlet of said other economizer section communicating with said vapor generator, an air duct in communication with said furnace to conduct heated air thereto, tubular means arranged to form a tubular path of flow and disposed in heat exchange relationship with said air flowing to the furnace, the outlet of said tubular path of flow being in communication with the inlet of said one economizer section, means for preheating feed liquid, said lastincntioned means being in communication with the inlet of said other economizer section so as to deliver heated feed liquid thereto, said inlet of the tubular flow path also being in communication with the preheated feed liquid means to receive heated feed liquid therefrom, and control means constructed and arranged to control the flow of preheated feed liquid from the preheated feed liquid means to said tubular flow path and also to the other economizer section.

References Cited in the file of this patent UNITED STATES PATENTS 1,235,928 Sargent et a1 Aug. 7, 1917 1,285,201 iacobus et al. Nov. 19, 1918 1,753,363 Coghlan et al. Apr. 8, 1930 1,833,130 Roe Nov. 24, 1931 1,975,519 Rudorff Oct. 2, 1934

Claims (1)

1. IN VAPOR GENERATING APPARATUS COMPRISING A VAPOR GENERATOR HAVING A SETTING, A FURNACE IN THE SETTING, MEANS FOR FIRING THE FURNACE, SAID SETTING HAVING A GAS OUTLET IN COMMUNICATION WITH THE FURNACE AND THROUGH WHICH GASES OF COMBUSTION FLOW FROM THE SETTING, VAPOR GENERATING SURFACE IN THE SETTING IN HEAT EXCHANGE RELATIONSHIP WITH SAID GASES OF COMBUSTION PRIOR TO THE FLOW OF SAID GASES FROM THE SETTING GAS OUTLET, AN ECONOMIZER FOR HEATING LIQUID FOR SAID VAPOR GENERATING SURFACE, THE ECONOMIZER BEING POSITIONED IN HEAT EXCHANGE RELATIONSHIP WITH GASES OF COMBUSTION FLOWING FROM THE SETTING AFTER PASSING IN HEAT EXCHANGE RELATIONSHIP WITH SAID VAPOR GENERATING SURFACE, THE ECONOMIZER HAVING A PLURALITY OF SECTIONS, ONE SECTION THEREOF BEING POSITIONED BEYOND ANOTHER SECTION IN RESPECT OMIZER SECTIONS EACH HAVING AN INLET THROUGH WHICH LIQUID ENTERS THE SECTION AND AN OUTLET THROUGH WHICH LIQUID PASSES FROM THE SECTION AFTER FLOW THEREIN, THE OUTLET OF SAID ONE ECONOMIZER SECTION BEING IN COMMUNICATION WITH THE INLET OF SAID OTHER ECONOMIZER SECTION, CONDUIT MEANS COMMUNICATING WITH THE OUTLET OF SAID OTHER ECONOMIZER SECTION AND THE VAPOR GENERATING SURFACE, AN AIR HEATER COMPRISING AIR CONDUCTING MEANS THROUGH WHICH AIR TO BE HEATED FLOWS AND A TUBULAR PATH OF FLOW HAVING A LIQUID INLET AND A LIQUID OUTLET, THE LIQUID OUTLET BEING IN COMMUNICATION WITH THE INLET OF SAID ONE ECONOMIZER SECTION, SAID TUBULAR PATH OF FLOW BEING DISPOSED IN HEAT EXCHANGE RELATIONSHIP WITH AIR PASSING THROUGH SAID AIR CONDUCTING MEANS, A FEED LIQUID PREHEATER HAVING A FEED LIQUID INLET THROUGH WHICH FEED LIQUID TO BE HEATED ENTERS THE HEATER AND A FEED LIQUID OUTLET THROUGH WHICH HEATED FEED LIQUID FLOWS FROM THE HEATER, AN ECONOMIZER FEED LIQUID CONDUIT IN COMMUNICATION WITH THE INLET OF SAID OTHER ECONOMIZER SECTION AND WITH SAID PREHEATER OUTLET, AN AIR HEATER FEED LIQUID CONDUIT IN COMMUNICATION WITH THE INLET OF THE AIR HEATER TUBULAR PATH FO FLOW AND WITH SAID PREHEATER OUTLET, AND CONTROL MEANS FOR CONTROLLING THE FLOW OF HEATED FEED LIQUID FROM SAID PREHEATER TO THE AIR HEATER TUBULAR FLOW PATH AND FROM SAID PREHEATER TO SAID OTHER ECONOMIZER SECTION.

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