US2662506A - Steam generator - Google Patents

Description

C. H. CARI-EY STEAM GENERATOR Dec. l5, 1953 Filed March 25, 1952 Patented Dec. 15, 1953 UNITEDSTATES PATENT OFFICE STEAM GENERATOR Clyde H. Carley, North Adams, Mass. Application March 25, 1952, Serial No. .278,450 13 Claims. (Cl. 122-173) This invention relates to steam generators and more particularly to a heating boiler of novel construction and high operating efficiency.

The class of heating boilers contemplated by this invention are generally known as porcupine or thimble tube boilers in that the water-heating surface comprises a plurality of relatively small tubes extending outwardly from the water chamber into the path of the hot gases coming from the combustion chamber. Numerous prior constructions of such boilers have been proposed, particularly with respect to the relative disposition of the thimble tubes, the direction of the hot gases past the tubes, the location of the combus tion chamber and stack outlet, etc., all with the view of obtaining certain operating advantages. While each of such prior boilers offered certain specic advantages their construction involved a compromise with respect to other desirable features with the result that thimble tube boilers have as yet not found wide general use.

An object of this invention is the provision of a thimble tube boiler of simple construction, high operating eiiiciency and one affording numerous practical features not found in presently-known boilers of this class.

An object of this invention is the provision of a thimble tube heating boiler wherein the boiler water is heated predominantly by radiation.

An object of this invention is the provision of a thimble tube boiler wherein the flow of gases from the combustion chamber to the stack outlet is unidirectional and counter to the movement of the boiler water.

An object of this invention is the provision of a thimble tube boiler wherein the combustion chamber is positioned at the top of the boiler over the thimble tubes and the upper surface of the combustion chamber is defined by a refractory member removably positioned at the top of the boiler to facilitate cleaning of the boiler interior.

An object of this invention is the provision of a vertical thimble tube boiler wherein the upper rows of tubes are of progressively-varying lengths and the combustion chamber is disposed over the tubes and of substantially spherical shape.

An object of this invention is the provision of a thimble tube boiler wherein the combustion chamber is substantially spherical and disposed i predominantly over the normal water line of the boiler to provide superheated steam to the steam main.

An object of this invention is the provision of a thimble tube boiler having a substantially spherical combustion chamber disposed at the top of the boiler predominantly over the normal water line of the boiler and wherein approximately 10% of the boiler water-heating surface is exposed to direct radiations from the combustion chamber to produce approximately of the boiler-heating capacity, approximately 76% of such surface is exposed to contact by the gases leaving the combustion chamber to produce approximately 12% of the total boiler-heating capacity, and the remainder of the surface is exposed to radiations of reduced intensity to superheat the steam fed to the steam main.

An object of this invention is the provision of a heating boiler comprising a vertical, substantially cylindrical water chamber, a plurality of thimble tubes communicating with the water chamber and projecting toward the axis of such chamber, a combustion chamber disposed at the top of the boiler over the said tubes, a stack outlet at the bottom of the boiler and communicating with the combustion chamber and baiile means directing the iiow of gases from the combustion chamber into surface contact with said tubes.

An object of this invention is the provision of a heating boiler comprising a vertical, substantially cylindrical water chamber; a plurality of thimble tubes communicating with the water chamber and extending toward the axis of such chamber, the upper rows of the tubes being of progressively-varying length; a substantially spherical combustion chamber centrally positioned at the top of the boiler and over the said tubes; a heat baille supported at the bottom of the boiler and extending axially of the water chamber; a refractory-material member supported by said baiile said member having a concave surface dening a portion of the combustion chamber; a top removably positioned on top of the water chamber, said top being made of a refractory material and having a concave surface defining the upper portion of the combustion member; a stack outlet at the bottom of the boiler and communicating with the combustion chamber; a steam outlet communicating with the water chamber above the normal water line; and a water return connection at the bottom of said water chamber.

These and other objects and advantages will become apparent from the following description when taken in connection with the accompanying drawings illustrating the construction of a thimble tube boiler made in accordance with my invention. It Will be understood the drawings are for purposes of illustration and are not to be construed as defining the scope or limits of the invention, reference being had for the latter purpose to the appended claims.

In the drawings wherein like reference characters denote like parts in the several views:

Figure 1 is a vertical section through a thimble tube boiler made according to my invention;

Figure 2 is a top view of the boiler with the refractory material top removed; and

Figures 3 and 4 are enlarged, fragmentary cross-sectional Views showing two different constructions of the thimble tubes.

Reference is now made to Figure l which may be considered as a somewhat diagrammatical representation in that structural details not material to a clear understanding of the invention are either omitted or illustrated in outline form. The water chamber I0, of the boiler, comprises a substantially cylindrical core formed by an outer shell I I and an inner shell I2 extending upwardly from the boiler base 9. The shells i I and I2 are suitably welded together to form a water tight reservoir. The outer shell extends somewhat above the inner shell resulting in a horizontal ledge for the accommodation of the top i3 which is made of a suitable refractory material. One or more observation ports Ic may be provided in the top I3 and the inner surface of the top is concave to form a substantially spherical combustion chamber I5, as will become more apparent as the description proceeds. Each observation port is normally closed by means of a suitable removable plug I6. The inner shell I2 is perforated below the normal water line and a plurality of thimble tubes It, which form the main heating surface of the unit, each have an end passing through a perforation, substantiallf.7 as shown. As is well known in this art, each tube may be secured firmly in position by rolling the inner end over the inner surface of the shell I2. As shown in Figures 3 and 4, the tubes may take one of a number of specific forms. In Figure 3 the tube I8 has a substantially-uniform diameter and slopes downward slightly from the shell I2. In Figure 4 the tube i8' is conical. In any case, the important consideration is that the upper, inner surface of the tube slopes upward toward the shell such that the heated water, within the tube, will flow smoothly in an unimpeded path into the water chamber. Again referring to Figure 1, feed water coming into the bottom of the water chamber through the return inlet I3, will be heated and will move upwardly from one thimble tube to the next, owing to the angle of the tubes, receiving more and more heat until it reaches the upper water level.

It may here be pointed out that a majority of the thimble tubes are of uniform length, approximately six inches, but the upper rows of the tubes, namely, tubes Ia, IBD and ISC are of progressively decreased length thereby conforming, in a general sense, to the spherical shape of the combustion chamber I5. It will be noted that a significant portion of the surface of the upper tubes Ia, ISb, 18o, is exposed directly to heat radiations emanating from the burning fuel supplied through a conventional burner 20. In the design of the boiler, I make such exposed sur-l face area approximately 10% of the total heating surface of the boiler. The remainder of the combustion chamber I5 is lined with refractory material 2i having skirt-like ends 2l to further promote the generally spherical contour of the combustion chamber.

Supported from the bottom of the boiler and centrally disposed therein is a hollow, metal bale 22 which carries a heat reflecting member 23 made of a refractory material and having a concave upper surface, conforming substantially to the spherical shape of the combustion chamber, and a concave periphery 23. The concave upper surface reflects infrared rays to the other walls of the combustion chamber whereas the concave periphery reects such rays toward the upper three rows of tubes ISa to lac. Although, as stated above, only approximately 10% of the surface of the upper tubes is exposed toward the combustion chamber, the reflective character of the heat reflector 23 is such that this 10% surface extracts approximately 50% of the total available heat of combustion, an important consideration in the design of a boiler for efficient operation.

Several practical considerations apply to the generally spherical combustion chamber I5. The concave chamber surfaces reflect infrared rays and normally would become very hot. Therefore, I prefer to make the refractory top I3 of suicient thickness to reflect the heat back into the chamber without significant external heat loss. In actual practice, the inner portion of the top l3- retains a fairly high temperature for smokeless starts of the burner during intermittent boiler operation. The curved, inner surfaces of the top I3 and refiector 23 refract convergent rays to increase boiler efficiency, while the curved peripheral surface of the member 23 refracts divergent rays toward this same end Normally, the central section of the combustion chamber, comprising the refractory 2i, would get extremely hot but it will be noted the refractory material at this section is relatively thin and passes heat to that portion of the water chamber which is above the normal water line of the boiler. Consequently, this central section of the combustion chamber serves to superheatl the steam passing out of the water chamber through one or more steam mains 25, said steam mains communicating with the water chamber at the top of the shell il, as shown. In practice, I design the boiler so that the central portion of the combustion chamber comprises approximately 14% of the total heating surface and so that such section will provide approximately 28% the total boiler heating capacity in the form of superheated steam.

Attention is directed to the fact that the stack outlet 26 is disposed at the bottom of the boiler, certain thimble tubes being omitted for this purpose. It will be clear, therefore, that the hot gases have a single, unidirectional flow from the combustion chamber to the stack and that such flow is contra to the movement of the boiler water from the bottom of the water chamber to the steam main. It will also be noted that the baffle 22 has an inwardly-curved lower section to afford a ready flow of the gases out of the stack outlet.

When heat is generated in the combustion chamber I5 the gases pass downwardly over the thimble tubes, heat being extracted until the gases exit through the stack outlet 26. Heating of the boiler water is accomplished by direct radiation to the upper three rows of thimble tubes and by heat conduction through the lower rows of the tubes. There is no heating by convection. As the relatively cool feed water enters the return inlet I 9 it enters the lower thimble tubes, is heated slightly and moves upward to the next row of tubes where it receives more heat, such motion continuing until it reaches the top Where it is converted into steam to be superheated in the upper section of the water chamber. The new of the progressively-heated water is perfectly smooth. In normal operation, the ring rate of the boiler is that rate which will bring the stack temperatures to approximately 212 F. or 10% over the temperature of the return water, whichf ever is the higher. Such ring rate is correct for the radiant heat and superheat sections to produce 78% of the heat load. At 12% CO2 in the stack, the overall boiler efliciency is 90%. Further, in such arrangement of the heating surfaces, wherein convection heating is eliminated and the steam is superheated, there is a direct saving on the E. D. R. (equivalent of direct radiation) in the boiler installation.

As the specific gravity of solids does not change as rapidly with temperature as does that of liquids, any solids suspended in the boiler water and carried upward within the water chamber will reach a point of equilibrium beyond which such particle will not rise. Thus, practically only distilled water will be converted into steam and no solids will come in contact with a temperature high enough to bake the solids into a scale.

Domestic hot water may be furnished by mounting a copper coil inside of the water chamber, as shown, the spacing between adjacent coil turns being equal to, or slightly greater than, the outside diameter of the tubing. Cold water flows into the coil at the lower end 3l and hot water is drawn out of the upper end 32. The coil 36 is designed for what is known as instantaneous hot water service, as distinguished from a hot water storage system involving a separate tank, and includes an aquastat control system for operation of the burner during periods when the boiler is not operating for steam, all as is well known in this art. However, in connection with my particular boiler, it is interesting to point out that solid particles which may be suspended in the boiler feed water will, upon being heated, rise slowly from one thimble tube to the next to some maximum level below the top surface of the Water, namely, where the specific gravity of the particle equals that of the water. In its upward travel the particle will pass between the turns of the hot water coil v30 and, being chilled by the copper tube, will sink straight down in the circular-core water chamber to settle at the bottom. Such accumulated particles may be blown out occasionally through a suitable blow-out connection S4. It is clear, therefore, that the drawing of domestic hot water not only flushes out the copper tubing but also keeps the outer surface of the tubing clean.

I have already stated that the refractory top I3 is removably disposed on top of the boiler. This member may be provided with suitable steel braces for structural purposes to reduce the chance of breakage when the top is removed. By simply removing the top I3 immediate access is had to the entire combustion chamber. Further, the baie member 22 may be lifted out of the boiler if such member is frictionally retained in upright position by a suitable supporting collar affixed to the base of the boiler. Removal of the baille member affords access to the individual thimble tubes. Occasionally, the entire inside of the boiler may be washed down by inserting a water hose into one of the ports I4, in the top I3', and connecting a drain hose to the clean-out outlet 36. The necessity for washing down the boiler should arise no oftener than once in severalyears and, since the washing is done by means of a downwardly-directed water stream, there is no dust or soot generated as is the case with conventional boilers requiring a brushing or swabbing action.

From the above detailed description the numerous construction, operating and maintenance features of my boiler will now be apparent. Those skilled in this art will nd no difficulty in modifying some of the component parts and their interrelated assembly to meet specific desired, or required, conditions. made without departing from the scope and spirit of the invention as set forth in the following claims.

I claim:

1. A boiler of the type described comprising a vertical water chamber in the form of a substantially-eylindrical core having a length substantialli7 spherical combustion chamber posed at the top of the boiler, a plurality of tubes extending radially from the water chamber each tube having an open end communicating with the water chamber and a closed end directed toward the axis of the water chamber, a stack outlet disposed at the bottom of the boiler, a feed water inlet communicating with the water chamber at the bottom thereof, a tubular baffle extending along the axis of the water chamber and a refiecting member of refractory material carried by the baiiie said reflecting member having a concave upper surface deiining the lower portion of the combustion chamber.

2. The invention as recited in claim 1, wherein the top of the boiler comprises a removable member made of refractory material said member having a concave inner surface defining the upper portion of the combustion chamber.

3. The invention as recited in claim 1, wherein the inner upper surfaces of the said tubes are inclined downwardly away from the water chamber and the upper tubes proximate to the combustion chamber are of reduced length.

4. The invention as recited in claim l, wherein some of the tubes are disposed above the reflecting member and exposed to direct heat radiations emanating from the combustion chamber and such exposed tubes constitute approximately 10% of the total heating surface of the boiler.

5. A boiler of the type described comprising a vertical water chamber in the form of a substantially-cylindrical core extending substantially the full height of the boiler; a substantiallyspherical combustion chamber at the top of the boiler, said combustion chamber predominantly disposed above the normal water line of the boiler; a removable member of refractory material forming the top of the boiler said member having a concave inner surface which constitutes the upper surface of the combustion chamber; a cylindrical baiile member disposed axially with respect to the water chamber and removably supported on the bottom of the boiler; a reiiecting member of refractory material on the top of the baille member, said reflecting member having a concave upper surface conforming to the general spherical shape of the combustion chamber; a stack outlet at the bottom/of the boiler; a steam outlet connected to the upper portion of the water chamber at a point above the center of the combustion chamber; a plurality of tubes extending radially from the water chamber, each tube having an open end communicating with the Water Such modifications may be.

equal to the boiler height, a substantially.

chamber and a closed end spaced from said bafe member; and a Water-inlet connection at the bottom of the water chamber.

6. The invention as recited in claim wherein some of the tubes are disposed above the upper surface of bale member and such tubes are of progressively-decreased lengths with the shortest tubes closest to the combustion chamber.

'7. The invention as recited in claim 6, wherein the said reiiecting member has a concave periphery presented to the shorter length tubes.

8. The invention as recited in claim 5 wherein the lower portion of the baffle member in the vicinity of the stack outlet is of reduced diameter.

9. A steam boiler comprising an outei` shell and an inner shell constituting a vertical substantially-cylindrical core water chamber; a steam main connected to the water chamber at the upper end thereof; a substantially-spherical combustion chamber; a refractory-material top removably disposed over the top of the shells said top having a concave inner surface deiining the upper portion of the combustion chamber; refractory-material adjacent to the upper surface of the inner shell said material defining the central portion of the heating chamber; a plurality of perforations in the inner shell said perforations extending substantially from the lower end of the shell to the refractory material forming the central portion of the combustion chamber; individual tubes extending radially from the inner shell toward the axis thereof each of said tubes having an open end passing through a perforation and a closed end spaced from the shell axis; a cylindrical baie member disposed axially Within the inner shell and extending upwardly from the lower end of the shell, said baffle member having a side wall spaced from the inner ends of the tubes and an upper end lying below the level of some of the uppermost tubes; a reflecting member of refractory material disposed on the top of the bafe member, said reiiecting member having a concave upper surface dening the lower portion of the combustion chamber; a stack outlet passing through the shells at the lower end thereof; and a feed water inlet connected to the water chamber at the lower end of the outer shell.

10. The invention as recited in claim 9, wherein the said tubes are arranged in horizontal rows and the tubes in the uppermost rows are of progressively-decreased length with the shortest tubes nearest to the combustion chamber.

l1. The invention as recited in claim 10, Wherein the said reflecting member has a concave periphery adapted to reflect heat rays to the shorter length tubes.

12. The invention as recited in claim 9, wherein the refractory material top includes a vertically-extending aperture communicating with the combustion chamber and including a removable plug closing said aperture.

13. The invention as recited in claim 9, wherein the lower portion of the baille member in the vicinity of the stack outlet is of reduced diameter and such reduced-diameter section is frictionally disposed within a bailie-supporting member carried by the boiler base.

CLYDE H. CARLEY.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,842,965 Fountain Jan. 26, 1932 1,923,614 Clarkson Aug. 22, 1933- FORETGN PATENTS Number Country Date 455,103 Great Britain Oct. 14, 1936

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