US2217594A

US2217594A - Fluid heat exchange apparatus

Info

Publication number: US2217594A
Application number: US188922A
Authority: US
Inventors: Charles E Lucke
Original assignee: Babcock and Wilcox Co
Current assignee: Babcock and Wilcox Co
Priority date: 1938-02-05
Filing date: 1938-02-05
Publication date: 1940-10-08
Anticipated expiration: 1957-10-08

Description

Oct. 8, 1940. C '5 KE; 2,217,594

FLUID HEAT EXCHANGE APPARATUS Filed Feb. 5, 1938 I64 I 1 8 I30 /32 33: C/mr/sflucke 194 A dEaJQR-W ATTORNEY.

Patented Oct. 8, 1940 UNITED STATES PATENT OFFICE FLUID HEAT EXCHANGE APPARATUS Application February 5, 1938, Serial No. 188,922

9 Claims.

This invention relates to fluid heat exchange apparatus, and it is more particularly concerned, in one of its phases, with a water 'tube boiler so associated with a superheater that high superheats may be attained without excessive variations in superheat under varying boiler load conditions.

Further objects of the invention will appear in the accompanying description which is to be read in connection with the associated drawing,

in which:

Fig. l is a diagrammatic view in the nature of a vertical section through a boiler and superheater installation in which there is a single vertical open pass between a bottom furnace exit, and the superheater.

Fig. 2 is a view similar to Fig. 1, but showing a modification in which there are two open passes arranged side by side and disposed between the superheater and the furnace.

Fig. 3 is a diagrammatic view in the nature,

of a vertical section througha boiler and superheater installation provided with a plurality of open passes and provided with regulators for controlling the gas flow through the open passes to the superheater.

In water tube boilers of the prior art, and especially those associated with convection superheaters, the stem temperature rises with an increase in boiler load and usually the variation with load is greater where water wall furnaces are used. It is one object of this invention to eliminate such variation of steam temperature.

The invention is concerned with boiler furnaces provided with water walls and operated at high furnace temperatures, and, furthermore, with boilers which have gas radiation passages defined by water walls and disposed between the furnace exit and the point of entrance of the gases to a chamber in which a bank of convection tubes is located. The purpose of these gas radiation passages is to cool the gases to a temperature suitable for entrance to the chamber in which the gases pass over the tube bank. My invention is concerned with a method of control of superheat for such boilers.

The gas radiation passages, such as the passages I 0 and. 12 of Fig. 3, between the furnace exit l4 and the tube bank entrance ii, are so proportioned as to width and length that by gas radiation to their water walls, supplemented by some convection heat transfer, the heat lost by the gases during the time of flow of the gases through those passages is sufficient to reduce the gas temperature to the desired amount, especially at full load. Under these conditions, saturated steam from the steam and water drum 20 has its temperature raised by the superheater l8, and, with such a combination, the superheat, if correct at full load, is too low at light load; or, if

correct at light load, is too high at full boiler load. My invention aims to correct such conditions and to accomplish its object by varying the degree of gas cooling effected by the gas radiation passages beyond the furnace, and it accomplishes this result independently of the variation of the temperatures of the furnace gases as they pass from the furnace.

The temperatures of the furnace gases as they discharge from the furnace also decrease or increase with decrease or increase of load, and when these gases pass directly from the furnace over a bank of convection tubes including the superheater, they are usually at temperatures differing from the temperature necessary to produce the desired superheat with a certain existing ratio of gas weight to steam weight. By my invention the temperature of the gases is changed in the gas radiation passage between their point of exit from the furnace and their point of entrance to the tube bank. The gas temperature is so regulated and changed that the gases'are hotter at light load or colder at full load than would otherwise be the case, the adjustment of gas temperature being made with reference to the superheat desired. In water tube steam boilers of the type illustrated in the drawings, there is a definite or normal path for the gases between the furnace exit and the tube bank, and the cooling of the fumacegases takes place as they proceed along this path. My invention involves the additionof one or more gas paths which may be provided with a regulator for so controlling the flow of gases that the gases proceed only through the normal path, or, selectively, and depending upon the desired superheat, the gas flow is divided between the normal path and a control path. Again, under other conditions of load and desired superheat, the gases may be caused to pass entirely along the control path. These multiple paths provide different degrees of gas cooling between the furnace exit, and the tube bank, or superheater entrance.

Referring to Fig. l of the drawing, there is a single vertical open pass 30 receiving furnace gases through the outlet 32 at the bottom of the furnace 34. The superheater 36 is located in a water wall chamber 38 beyond the open pass or gas radiation passage 30 and is connected therewith by a gas'flow passage 40. This passage, as well as the outlet 32 from the furnace 34, is-pro-. vided by the bending of some of the water tubes 44 and 46 'out of the plane of the

water walls

48 and 50. The normal path of flow of the furnace gases is from the furnace 34 through the outlet 32,- then upwardly through the gas radiation chamber and through the top entrance 40 to the chamber 38in which the bank or tubes constituting the superheater 36 is located. Along this normal path the furnace gases are subjected to cooling mainly by reason of gas radiation to the fluid cooled surfaces of all of the walls of the gas radiation passage 30.

With further reference to the embodiment of the invention indicated in Fig. 1 of the drawing, I provide a second and shorter gas control path in which the gases pass from the top of the furnace. In this instance, the gas outlet 60, provided by bending some of the tubes of the wall 48 out of the plane of the wall, is opened by movement of the regulator 62 from its full-line position to'its lower and open position 64, indicated by the dotted-lines in the drawing. When the furnace outlet is closed and the regulator 62 is in the position indicated in full-lines, all of the furnace gases must traverse the full length of the gas radiation passage 30. They are thus cooled to the maximum extent. If, under such conditions, the gases contacting with the superheater are at temperatures too low to produce the desired superheat, the regulator 62 is opened to some extent and gases at furnace temperature are admitted directly to the top of the gas radiation passage 30. In this passage they mix with the gases which have traveled the full length of the gas radiation chamber and the temperature of the furnace gases may be thus raised to an extent sufllcient to produce a superheat of the value desired. Under usual conditions, the regu lator 62 would be open at light load and closed at full load.

It will be appreciated that my invention is of such a scope that it is not limited to all of the details of the installation-which is indicated in Fig. 1 of the drawing. It is rather of such a scope that it covers various arrangements of the component parts herein indicated. For example, a similar installation may involve two open passes side by side and arranged between a bottom furnace exit and a top superheater tube bank entrance. There may be a top and bottom opening in the wall dividing them, and the bottom opening may be provided with a gas flow regulator.

Fig. 2 of the drawing shows two open parallel gas passes I0 and I2 between the furnace I4 and the superheater I6. In this installation, the open pass, or gas radiation passage I0, is wider than the similar open pass I2.

Gas flow regulators

18 and 80 are provided for the top and bottom openings 82 and 84, respectively, in the wall 90 dividing the gas radiation passages. The arrangement of elements here is such that all of the furnace gases may flow through the gas radiation passage 12, or all of the gases may be caused to flow through the pass I0, or. the total gas flow may be so divided that part of the gases flow throughout the length of the gas radiation passage I2 and the remaining gases flow from the bottom of the pass I0 to the top thereof.

When all of the gases flow up through the gas radiation passage I2 and the regulator I8 is in its open position, as indicated in the full-lines at I8, and the lower regulator is in its closed position, as indicated in the full-lines at 80, the

' amount of gas cooling by gas radiation to the fluid cooled walls will be at a minimum. An intermediate amount of cooling will take place when all of the gases flow up through the gas radiation passage I0. The maximum cooling of the furnace gases between the furnace and the superheater will take place when the regulators 80 and I8 are in such positions that the total gas flow will be divided between the primary and secondary gas radiation chambers I0 and I2.

This would be the condition of the apparatus at full boiler load, while the first arrangement, with all of the gases flowing upwardly through the gas radiation chamber I2, would be the condition for light boiler load.

An embodiment of the invention somewhat similar to the installation indicated in Fig. 2 of the drawing would involve two open gas passes arranged side by side so that all of the gases might be directed from a furnace outlet at the bottom of the furnace to a gas entrance at the bottom of the chamber in which the bank of superheater tubes is located. In this instance, the dividing wall between the two open passes would have top and bottom openings for the passage of furnace gases, with only the gas flow through'the bottom opening being subject to Y 4 regulation. In such a case, the gases would normally traverse the full length of both open passes in series, but, with the bottom opening in the dividing wall open, part of the gases would flow directly across the width of both passages at the bottom of the installation and would mix with the remainder of the gases which had passed through both gas radiation chambers, and such mixing would take place before the gases entered the chamber in which the superheater would be located. Under normal or full load conditions, the gas flow opening in the bottom of the dividing wall would be closed. When, under light load conditions, the gases are allowed to pass through this opening, the temperatures of the gases would be comparatively higher.

In the embodiment of the invention indicated in Fig. 3 of the drawing, the fluid cooled

division walls

92, 94, and 96 are provided with gas flow openings I4, 98, and I6, respectively, at their lower parts. The dividing wall 94 between the two open gas passes I0 and I2 is also provided with a gas flow passage I00 which may be controlled by the regulator indicated in full lines at I02. The gas flow opening 98 is similarly controlled by a regulator I04 which is indicated in full lines in closed position. When the regulator I02 is moved to its dotted-line position closing the opening I00, none of the gases traverse the open passes. With this arrangement of elements, there would be a minimum of gas cooling. With the regulator I02 open and the regulator I04 closed, all of the gases traverse the full length of both of the open passes in series, giving the greatest degree of gas cooling, while a partial opening of both regulators provides an intermediate degree of cooling.

While the invention has been illustrated in connection with the boiler installations all having open passes arranged for vertical flow of gases, and the boilers are indicated as provided with water walls including vertical tubes for natural circulation, it is to be understood that my invention is applicable to boilers with vertical passes defined by walls including horizontal tubes. Another useful embodiment within the scope of my invention includes horizontal flow gas passes provided with vertical tubes. Again, the invention is also applicable to once-through boilers and pump circulation boilers where there may be one or more open passes for gas cooling between the furnace exit and the convection heating surfaces which may be formed by the superheater. In all cases, there are one or more fiow paths between the two terminals, and the invention is characterized by its ability to accomplish different degrees of gas cooling between the two terminals, these different degrees of cooling being attained by dividing the gas f'owbetween a plurality of gas passes to any desired degree, or varying the length of time available for radiation of heat from the gases.

It is also within the scope of the invention that gas flow through the various openings leading to or from the gas radiation chambers may be controlled without the use of regulators which involve dampers. For example, the control of the gas flow through such openings may be effected by providing furnace gas streams of high pressure directed across the openings to minimize or limit the gas flow therethrough.

Each of the embodiments of the invention indicated in the drawing includes a steam and water drum directly connected to bottom headers by tubes which are so arranged as to define the walls of the furnace and the various gas chambers. In Fig. 1, the wall tubes I 20' extend outwardly from the drum,20 so as to deflne the roof of the furnace 34, and thence vertically downwardly to a position where' they are connected to the bottom furnace header I22. From this header, horizontally inclined floor tubes I24 extend to a position where they are connected to the header I26.

From this header short floor tubes I28 directly connect the header I26 with the header I30 Other floor tubes I32 directly connect the header I30 with the header I34. From the =latter, the wall tubes I36 extend vertically along one side of the superheater chamber to the roof thereof. From that position, they are horizontally inclined, and extend to a position wherein they directly connect with the drum 20. Along the floor of the furnace 34, as well as the furnaces of the other embodiments of the invention, the floor tubes may be provided with space closing devices such as metallic blocks closely fitting the tubes and maintained thereon by clamping devices which secure the blocks to the tubes in good heat exchange relationship. Similar constructions may be used for closing the spaces between some of the wall tubes. In higher temperature zones of the installations the spaces between the wall tubes may be closed by ceramic refractory material mechanically anchored to the tubes and thermally maintained thereon by metallic studs transversely related to the tubes and welded thereto. Again, in some of the gas zones, the wall tubes may be so arranged that they are substantially in contact, thus constituting tube to tube walls.

The furnaces of the illustrative, embodiments of the invention are fired by burners which in some instances may be pulverized fuel burners 0. When pulverized fuel is employed, the furnaces maybe constructed as slag tapfurnaces' maintaining a pool of molten slag on the floor. It is understood that suitable ash or slag removal means, not shown, are to be applied.

All of the embodiments of the invention also include in the superheater chamber a fluid heater I50 which is located beyond, or rearwardly of, the superheater, relative to gas flow. This fluid heater may constitute, in some instances, an economizer or, under other conditions, it may act as a reheater.

The side walls of the embodiments of the invention indicated in Figs. 1, 2, and 3, of the drawing may be formed by water walls similar to those above described, wall tubes I60 directly connecting the upper header I62 with the lower headers I64; and the side wall systems being appropriately connected for fluid movement therethrough. It is understood that suitable downcomer connec- It is also to be appreciated that the invention is of such a scope that any one of the embodiments herein described may be modified by the incorporation therein of changes within the scope of the disclosures of the other modifications.

It is also within the scope of the invention that the gas flow regulators may be controlled from any one, or appropriate combination of .many variables such as steam flow, superheat, furnace gas temperatures, etc.

The embodiment of the invention indicated in Figs. 2 and 3 of the drawing have headers I22, I26, I30, and I34 corresponding to the headers above described with reference to Fig. 1 of the drawing. In addition, they have floor headers I90 and I92 arranged between the floor headers I26 and I30 and directly connected thereto by short floor tubes I94 and I06 which may be covered with appropriate heat resisting material.

While, in compliance with the statutes relating to the patenting of inventions, and par-, ticularly Sec. 4888 R. S., I have described my invention with reference to certain specification embodiments which are shown in the accompanying drawing, and it is to be appreciated that the invention is not to be taken as limited thereto. It is rather of such a scope that the various elements of the different embodiments may be combined indifferent ways within the general principles which have been laid down. The scope of the invention is indicated by the sub-joined claims.

What is claimed is:

1. The method of fluid heating which comprises introducing a stream of fueland air for combustion into and burning the fuel in suspension while passing through a fumace-chamber, directing heating gases leavingthe furnace chamber through an elongated substantially unobstructed vertical gas passage and cooling the gases while 'flowing vertically therein mainly by radiation to fluid cooled walls thereof, directing the heating gases from the gas passage into contact with fluid heating surface in the path of the gases, and controlling the temperature of the heating gases contactingwith the fluid heating surface by passing a portion of the heating gases from the furnace chamber through a gas flow path of different gas cooling capacity beperature of the heating gases contacting with the steam superheating surface by passing a portion of the heating gases from the furnace chamber through a gas flow path of lesser gas cooling capacity before the gases contact with the steam superheating surface.

3. The method of generating and superheating steam which comprises introducing a stream of finely divided solid fuel and-air for combustion into and burning the fuel in suspension while passing through a furnace chamber under furnace temperatures above the fuel ash fusion temperature, directing heating gases leaving the furnace chamber through an elongated substantially unobstructed vertical gas passage and cooling the gases while flowing vertically therein mainly by radiation to steam generating surface defining the walls thereof, directing the heating gases from the gas passage into contact with steam superheating surface in the path of the gases, and controlling the temperature of the heating gases contacting with the steam superheating surface by passing a portion of the heating gases from the furnace chamber through a gas flow path of different gas cooling capacity before the gases contact with the steam superheating surface.

4. A steam generator comprising a setting including a furnace chamber and a convection section spaced laterally from the furnace chamber, a vertically disposed substantially unobstructed connecting passage having its opposite ends connected to said furnace chamber and convection section respectively, means for burning fuel in said furnace, chamber, steam generating surface for said generator including radiantly heated tubes defining walls of said connecting passage, means forming a second gas flow path connecting said furnace chamber and convection section, damper means arranged to control said second gas fiowpath, and a bank of fluid heating tubes in the path of gases fiowing'through said convection section and arranged to receive furnace gases from both of said connecting passages.

5. A steam generator comprising a' setting including a furnace chamber and a convection section spaced laterally from the furnace chamber, a vertically disposed substantially unobstructed connecting passage having its lower end connected to said furnace chamber and its upper end to said convection section, means for burning fuel in suspension in said furnace chamber, an upper steam and water separator, steam generating surface for said generator connected to said steam and water separator and including radiantly heated tubes defining walls of said connecting passage, means forming a separate gas flow passage between said furnace chamber and the upper end of said connecting passage. damper means arranged to control said separate gas flow passage, and a bank of fluid heating tubes in the path of gases flowing through said convection section and arranged to receive furnace gases from both of said connecting passages.

6. A steam generator comprising a setting including a furnace chamber and a convection section spaced laterally from the furnace chamber, a vertically disposed substantially unobstructed connecting passage having its lower end connected to said furnace chamber, a second vertically disposed substantially unobstructed connecting passage having its lower end connected to the lower end of said first connecting passage and its upper end to both said first connecting passage and said convection section, means for burning fuel in suspension in said furnace chamber, steam generating surface for said generator connected to said steam and water separator and including radiantly heated tubes defining walls of said connecting passages, damper means arranged to control the division of heating gases from said furnace chamber to said connecting passages, and a bank of fluid heating tubes in the path of gases flowing through said convection section and arranged to receive furnace gases from both of said connecting passages.

7. A steam generator comprising a setting including a furnace chamber and a convection section spaced laterally from the furnace chamber,

an inverted U-shaped substantially unobstructed connecting passage having upfiow and downflow sections serially connected at their upper ends and having their lower ends connected to said furnace chamber and convection section respectively, means for burning fuel in said furnace chamber, steam generating surface including radiantly heated tubes defining the walls of said connecting passage, a gas flow passage connecting the lower portions of saidupflow and downflow passage sections and arranged to permit furnace gases to by-pass the remaining portion of said connecting passage, damper means arranged to control said gas flow passage, and a bank of steam superheating tubes in said convection section.

8. A steam generator comprising a setting including a furnace chamber and a convection section spaced laterally from the furnace chamber, an inverted U-shaped substantially unobstructed connecting passage having upfiow and downflow sections serially connected at their upper ends and havingtheir lower ends connected to said furnace chamber and convection section respectively, means for burning fuel in said furnace chamber, steam generating surface including radiantly heated tubes defining the walls of said connecting passage including a wall separating said upfiow and downfiow passage sections, a gas flow passage in said separating wall and connecting the lower portions of said upfiow and downflow passage sections and arranged to permit furnace gases to by-pass the remaining portion of said connecting passage, damper means arranged to control said gas flow passage, and a bank of steam superheating tubes in said convection section.

9. A steam generator comprising a setting including a furnace chamber and a convection section spaced laterally from the furnace chamber, an inverted U-shaped substantially unobstructed connecting passage having upfiow and downfiow sections serially connected at their upper ends and having their lower ends connected to the lower portions of said furnace chamber and convection section respectively, means for downwardly introducing and burning finely divided solid fuel in suspension in said furnace chamber at furnace temperatures above the fuel ash fu sion temperature, an upper steam and water drum, steam generating surface including rows of radiantly heated tubes connected to said upper drum and defining the walls of said connecting passage including a wall separating said upfiow and downfiow passage ections, conduit means for supplying water from said upper drum to said radiantly heated tubes, a gas flow passage in said separating wall and connecting the lower portions of said upfiow and downflow passage sections and arranged to permit furnace gases to by-pass the remaining portion of said connecting passage, damper means arranged to control the gas fiow through said gas flow and connecting passages, and a bank of steam superheating tubes in said convection section.

CHARLES E. LUCKE.