US2816526A - Method of and apparatus for generating steam - Google Patents

Description

Dec. 17, 1957 D DALlN Y METHOD OF AND APPARATUS FOR GNRAT'ING STEAM Dec. 17, 1957 D, DALlN v 2,816,526 l METHOD OF AND APPARATUS FOR GENERATING STEAM Filed April 20, 1953 v 3 Sheets-Sheet 2 Dec. 17, 1957 D, DALIN 2,816526 METHOD 0F' AND APPARATUS FOR GENERATING STEAM Filed April 20, 1953 3 Sheets-Sheet 3 ,sowr l 73 y f ,A

FLUEGAS 0 OO f 55 l l l /fl ,//l V u United States Patent METHOD F AND APPARATUS FOR GENERATING STEAM David Dalin, Newr York, N. Y., assgnor to A/ B Svenska Maskinverken, Sodertalje, Sweden, a corporation of Sweden This invention relates to the art of generating steam and has as its purpose to so improve the generation of steam that a small compact plant constructed in accordance with this invention will have a capacity equivalent to that of a much larger steam generating plant of the most eicient type heretofore available; and further to assure that the steam produced will be much drier than that heretofore obtainable directly from a boiler.

' The significance of this invention is graphically demonstrated by the fact that the Swedish Steam Boiler Association recommends an output of 350 cubic meters of steam per cublic meter of steam space per hour, whereas a steam boiler constructed in accordance with this invention, but which does not take full advantage of its possibilities is presently delivering 3,500 cubic meters of steam per cubic meter of steam space per hour; and the weight and size of this plant is but a fraction of that of a La Mont type boiler of the same capacity. Actually its weight is but twenty percent and its total volume only twenty-live percent of a La Mont type boiler of equivalent capacity. Moreover, where a moisture content of approxirnately one percent has been considered normal in the past and 0.5 percent considered excellent, the moisture content of the steam delivered by the aforesaid boiler` is less than 0.3 percent.

This remarkable improvement results from an entirely new` method of generating the steam and vseparating it from the water. they are of the natural circulation or the forced circulation type the separation of the steam from the water takes place in a large drum generally located at the top of the boiler and which contains both water and steam. Also, in the conventional steam boiler the steam is generated in a large number of relatively small diameter tubes, some of which line the walls of the furnace or combustion chamber to be subjected to the radiant heat of the lire in the furnace and others of which are arranged as convection surfaces in the ue gas passages to be heated by the hot gases flowing therethrough, but in all cases the tubes deliver a steam-water emulsion to the steam drum.

With the present invention the steam drum and the conventional steam generating tubes are eliminated. Instead a few upright tube-like vessels provide both the steaming surfaces and the steam chamber. In fact each vessel constitutes a complete steam boiler in itself. These tube-like vessels contain water to a level spaced a distance below their closed 'upper ends where the steam outlet is located. Below the water level, the Vessels have extended surface on their exteriors to quickly transfer heat energy from a fluid heating medium llowing over the exterior of the vessels and effect rapid generation o f steam along the inner surface of the vessel walls. In fact, the transfer of heat energy is conducted at such a rate that the inner surfaces of the vessel walls below the water level are substantially covered with myriad steam bubbles which, following the path of least resistance, rise rapidly In conventional steam boilers whether along the vessel walls toward the surface of the water. As a result, the entry of the steam into the steam space provided by the upper closed end portion of each vessel is accomplished with a minimum of agitation of the water surface so that the strata of :foam on the water surface is relatively shallow.

This enables the distance between the water surface and the steam outlet to be reduced to a minimum, and undoubtedly accounts for the exceptional dryness of the steam produced by the practice of this invention.

This upward flow of the steam along the wall of the vessel also elects a very desirable toroidal circulation of the uid in the vessel. As the steam rises it naturally carries with it the adjacent water and as a result the water further removed from the wall and more especially at the center of the vessel ilows downwardly.

To effect these results rapid and eilicient transfer of heat energy from the heating medium to the water in the .Vessel is required, but the walls of the upper portion of the vessel which provides the steam -cha-mber and which are, of course, relatively dry must be protected from destructive heating. It follows, therefore, that where the heating medium (hot gases) flows upwardly over the vessel, most of the heat energy must be abstracted therefrom before it reaches these relatively dry wall surfaces. Consequently, the extended surface employed must be properly designed and capable of eiecting heat transfer at the rate required. Extended surface elements in the form of rod-like wires such as those illustrated in the Dalin Patent No. 2,584,189 when arranged and proportioned as taught in the Dalin et al. Patent No. 2,469,635 will accomplish this result. All references hereinafter, both in the specication and the claims, to correct proportioning, arrangement and disposition of the heating elements thus will be understood in the light of the teachings of the Dalin et al. Patent No. 2,469,635.

While various structures might be designed for the practice of the method of this invention, those illustrated in the accompanying drawings have been found to be well adapted thereto, and in these drawings:

Figure 1 is a vertical sectional view through a steam generating plant, especially suitable for marine service,

and which embodies the principles of this invention;

Figure 2 is a cross sectional view through Figure l on the plane of the line 2 2;

Figure 3 is a cross sectional view through Figure l on the plane of the line 3 3;

Figure 4 is a top view of the plant with the cover removed, said view being taken substantially on the plane of the line 4-4 in Figure l;

Figure 5 is a vertical sectional view through a steam generating plant of somewhat different design than that shown in Figure l; and

Figure 6 is a horizontal sectional view through Figure 5 on the plane of the line 6-6.

Referring now more particularly to the accompanying drawings, in which like numerals designate like parts throughout the several views, the high capacity steam generating plant illustrated in Figures l to 4 inclusive consists of two opposite rows of vertically disposed tube- like vessels 25 and 26 connected at their bottoms to a water distribution header 27 through which the vessels are communicated with one another.

The header 27 is rectangular and comprises four lengths of pipe mitered at their ends and welded together into a rigid annular unit. Hand holes equipped with covers 24 are provided at the corners of the header to enable cleaning thereof when necessary. The two longer sections or sides 28 and 29 have the vessels 25 and 26, respectively, mounted thereon; one of the shorter sections 30 has no upright vessels connected thereto but astasae 1.3 two uptight vessels 3l project from the opposite short section 32.

The distribution header 27 provides the base for the furnace, and the two opposite rows of upright vessels 2'5 and 26 tog'ethef with smaller tubes 33 and 34 and extended surface fins 35 on the vessels provide the inner surfaces of two opposite furnace walls 36 and 37. The other two walls 38 and 39 of the furnace, respectively have a burner nozzle 40 and a furnace door 4I mounted in the lower portions thereof; and a flue gas duct 56 lextending downwardly along the wall 37 carries the flue gases from' the furnace.

' Between the opposite rowsof vessels 2 5 and 2 6 are three rows of shorter tube- like Vessels 42, 43 and 44. The two outermost rows 42 and 44 `are connected with the adjacent sides of the distribution header by th'e tubes 33 and 34 whereas the units of themiddle row 43 have their lower ends connected to the adjacent upright Vessels 25 and 26 by tubes 46. All of the vessels, with thelexception of the center row of shortvessels 43, have their upper ends terminating upon a common plane and preferably provided with removable covers 47. Removal of these covers affords access to the interiors of the vessels for cleaning.

The short vessels 43 of the center row have their upper ends connected to a common steam header 48 which has access holes in the top thereof closed by removable covers 49 in line with each of the vessels` 43, also to afford access to the vessels for cleaning. Ducts 50 and 51 connect the upper ends of all of the remaining vessels with the common steam header 48,` and one end 52 of this header is extended for connection to the steam line (not shown).

Asbest shown in Figure l the lower portions fthe vessels'25, 26 and 31 as well as the tubes 33, 34 and 46 are subject to the direct radiant heat of the fire in the furnace, but the upper portions of these vessels as well as the full height of each of the shorter vessels 42, 43 and 44 are above the combustion chamber away from the direct radiant heat but in the path of the' upwardly flowing h'ot ue gases.

The exterior surfaces of all of the vessels are equipped with extended surface 53V in the form of rodlik' pins orwires `of the type illustrated in the aforesaidl Dalin Patent No. 2,584,189 and preferably applied in the manner there taught. TheseV extended surface lements are provided for a substantial portion of the lzieig'lt'4 of the vessels and disposed directly below the water level 54 to transfer heat energy from the hot flueg'ass" to the water in the vessels, and it stood that the extended surface on those vessels which form part of the walls of the furnace, ison only the surfaces thereof eXposed to the heating medium; this being illustrated by the dot and dash lines in Figure 3'.

With correct proportioning, arrangement anddi'sposition of the extended surface elements?, heat energy' ab'- strated from the fluid heating medium is transferred to the water in the vessels at such a rate that thetmpera'- ture of the gases upon reaching the u'ppei pprton's of the vessels which provide the steam spaces is low enough to be incapable of dele'teriously affecting the relatively dry walls of these portions.

By virtue of this rapid heat transfer water in a vessel contiguous to the upright wall of the vessel is quickly converted into steam bubbles which rise rapidly and' travel freely over the inner surface' of the vessel wall to enter the steam space without appreciably disturbing the surface of the water; and accordingly the steam is far drier than that produced by present methods, containing not more than about 0.3 percent of moisture.

The rising volume of steam mayv be said to c'onfr'tut'e" one link in a chain of toroidal circulation forthe in the vessel since it effects upward' flow ofthe 'water'conl' tiguous to the vessel wall` and as aresultfy c'auses dwi"l is, of course, f6 be under- 4 ward ow of the water at the center of the vessel. This toroidal circulation' is quite rapid, and with the corresponding rapid heat transfer brings about an unprecedented rate of steam production.

Due to the fact that the tubes 33, 34 and 46 which communicate the lower ends of the short vessels with the distribution header 27 (directly or indirectly) are too small in diameter to permit t-he hereinbefore described toroidal circulation to take place therein, the water level in the short vessels would fluctuate greatly, in the absence of means to prevent such fluctuation, and would often rise far above the level in the other vessels which are directly connected at their lower ends to the distribution" header. To avoid this objectionable consequence all of the vessels are interconnected substantially at the mean water level 54 by ducts 57 and from this level are exteriorly connected with the distribution header 27 by a downcomer 518 which may be equipped with a compensation tank 58C The tank 58 provides a reservoirfor water to compensate for possible failures in the feed water supply but obviously may be supplanted by a small diameter header 4through which the downcomer 58 would be onnectdwith all of the tubes 57.

Byvirtue of this interconnection between all of the vessels substantially at the mean water level and their connection from this level with the distribution header 27,;` an external circulation is possible which assures a substantially uniform water level in `all of the vessels, and in addition assures that any salt contained in the waterwill not concentrate in any portion of the system. In other words, any salt contained in the water will be distributed substantially uniformly throughout the entire system. Accordingly, it is possible to maintain a desired alkalinity in the water by merely periodically opening a cockf27' on the header 27.

Wherr the compensation vtank is used it is preferably mounted in theutlue gas duct and its upper portion is connected with the steam spaces of all of the vessels by ducts 59.

lFeed Water isl fed to the boiler from a feed line 60 whichv connects with the inlet of a conventional economizer 61 mounted in the ilue gas duct with its discharge 6 2. connected to the vtop of the compensation tank. Consequently the make-up water is preheated before entering thefsystern; and by virtue of the connections 59 betweenthe compensation tank and the connected steam spaces any/steam which formsl in the economizer enters the steamv space.

I As is customary the walls of the furnace as well asfthe flue gas duct 56 are jacketed and provided with insulation as shown.

An important advantage of this steam generator construction resides in the fact that the weight is concentrated a tthe bottom as distinguished from the conventional boiler plant which requires a large steam-water drum close to or at the very top thereof. Not only does this arrangementprovide greater stability for the boiler and thus render it especially suitable for marine use, but it eliminates the costly heavy supporting structure heretoforei needed," to carry the elevated steam-water drum and thel great-number of small diameter tubes which providedL the steaming surfaces and had to be supported from'thetop.

Another, adaptation of this invention is illustrated by the boiler-plant -shown in Figures 5 and 6. In this case alluof theuprfight tube-like vessels 65 are of the same height and'all of them have their lower ends connected to az common cylindrical centrally located distribution header 66 and vtheir upper endsl connected to a common steam header L67. The combustion chamber 63' is dis- I Josedl alongsidelthsj group; of vessels being partially detedby-tw sets-ofwat'er tubes 6 9 and 70 which coact lier "sselsto complete the boiler. All of` these wate tubes have their lower ends connected to the dis; tribution" header 66 and the upper ends of the two sets are-."connected to each other `asat 71 and to the adjacent vessels 65 by-means of a downwardly and upwardlyvopen lng discharge nozzle 72. The heating medium (hot gases) which emanates from the lire maintained by a burner 73 owsupwardly along the row of water tubes 69 and then passes between these tubes to enter a superheater chamber 74 in which a superheater 75 is located. From the bottom of this superheater chamber the hot flue gases flow upwardly between the vessels 65 and, of course, across their extended surface elements 76 to enter a line gas duct 77.

f"The flue gas duct has an economizer 7S and an air preheater 79 mounted therein, the economizer having its outlet connected by means of a duct 80 with the distribution header 66.

As will be readily apparent any steam formed in the water tubes 69 and '70 is discharged into the steam spaces of 'the adjacent vessels 65 by the upwardly opening branch of the nozzles 72 while the water leaving these tubes ows downwardly into the body of the water in these vessels.

As in the plant illustrated in Figures 1 to 4, inclusive, -all of the vessels 65 are interconnected -at the mean water level by ducts 81, and through a header 82 and a downcomer 83 are connected with the distribution header 66. As already explained this arrangement allows for an external circulation which supplements the toroidal circulation within each vessel and thus assures maintenance of a substantially uniform water level in all of the headers, and a substantially uniform distribution of any salts contained in the water.

One of the features of the plant shown in Figures 5 and 6 is that the extended surface elements of the upright vessels are so shaped that they collectively extend across all of the space between the vessels. This is illustrated in Figure 6 and is accomplished by turning the ends of certain of the elements either up or down.

Another feature of the plant shown in Figures 5 and 6 is that it effects a substantial reduction in the height of the boiler because the combustion chamber is located alongside the group of vessels 65 rather than beneath them as in the previously described constructions.

To permit the desired toroidal internal circulation in all embodiments of the invention, the distance between the heated wall and the portion of the vessel at which the descending fluid is coldest should not be less than about one and three-quarters (1%) inches. This means that where the vessel is cylindrical its inside diameter should not be less than about three and one-half (3l/t) inches; a diameter between live inches and ten inches is deemed to be most satisfactory.

From the foregoing description taken in connection with the accompanying drawings, it will be seen that one of the most important aspects of this invention is that it assures the production of dry saturated steam directly by the boiler and without the need for superheating. Those skilled in this art know full well the objections to wet steam, especially if it carries salt particles, hence it is not necessary to point out why this assurance of dry saturated steam is so important.

Another very important advantage of this invention is that it enables practically all of the abstractable heat to be transferred from the heating medium to the water within a short distance. This permits a substantial reduction in the height of the boiler for any given capacity and eiects a great saving in building costs. To illustrate, an oil-fired -boiler plant substantially like that shown in Figures l to 4 and having a capacity of 6,000 pounds of saturated steam per hour is but eight feet high and four feet seven inches square and weighs only 4,600 pounds, whereas a La Mont forced circulation type boiler of the same capacity would be at least sixteen feet high and about eight feet square and would weigh about 23,000 pounds. A conventional natural circulation type boiler of the same capacity would be even larger and heavier.

This advantage is further illustrated by the'factwtht a boiler of twice the stated capacity, namely 12,000 pounds of saturated steam per hour, would have the same eight foot height but twice the cross sectional area since increased capacity is easily met by merely multiplying the number of vessels and the increase can be all in one direction to facilitate transportation and to better accommodate given building designs.

This invention, therefore, makes possible railway transportation of a fully assembled oil-tired boiler of 80,000 pounds saturated steam capacity, since a -boiler of this capacity constructed in accordance with this invention would easily meet the standard railroad clearance and weight limitations. Such a boiler equipped with a superheater and used -with a condensing turbine would produce 8,000 kva.

Still another advantage of this invention lies in the fact that allinternal surfaces, that is-the inside of the vessels, etc., can be easily cleaned from the top of the boiler, necessitating only the removal off caps or covers closing the upper ends of the vessels, and in the case of the plant shown in Figures 1 to 4 the` opening of the covers 24 at the corners of the distribution header 27 and, of course, opening the blow-oid:` cock 27.

By the same token the external surfaces of the vessels, including the portions thereof upon which the extended surface is located, are easily reached from the top of the boiler for cleaning either by brushes or soot blowers.

The vertical disposition of the vessels and the general design of the units has the still further important advantage of facilitating removal of any vessel requiring replacement, since by virtue of this design and construction every vessel maybe quickly cut out of the boiler and replaced without disturbing the others.

While two specific embodiments of the invention have been shown and described herein, it is, of course, understood that such changes may be made therein as come within the scope of the appended claims.

What I claim as my invention is:

l. A steam boiler comprising a plurality of closed upright tube-like vessels, each of which has a steam outlet at the top and the tops of all of said vessels being at substantially the same elevation; a header connected with the bottom of each of said upright vessels so that said header communicates all of the vessels with one another; duct means connecting the upper portions of all of the vessels with one another at a common elevation a substantial distance below their tops; a downcomer connecting said duct means with the header; means for maintaining water in the thus communicated vessels to a level no higher than that of said duct means so that the upper portion of each vessel provides a steam space of substantial volume; pipes connecting the steam outlets of the vessels so that said upper portions of all of the vessels together comprise the steam chamber of the boiler, one of said pipes providing a common steam outlet; means for directing a fluid heating medium over the exterior surfaces of said vessels; and extended surface on the exterior of the vessels below the water level for abstracting heat energy from the fluid heating medium and transferring it to the water at a rate to rapidly effect and maintain a volume of rising steam between the water in each vessel and the wall thereof Iand to thereby maintain a toroidal circulation of the fluid in each vessel rising at the heated wall and descending remote from said wall with the steam which is formed entering the steam spaces adjacent to the wall.

2. The steam boiler of claim 1 further characterized by the fact that the downcomer includes a compensation tank at the water level and below the top of the vessels providing a reservoir for water.

3. The steam boiler of claim 2 further characterized by the provision of means defining a ue gas duct to carry olf the uid heating medium after it has passed over the exterior surfaces of the vessels; and an economizer in said=i1e gas ductliavi-ngits discharge end conneted with the'Y ripeiisat-ion tank for supplying preheated feed water to. the boiler; v

4. A steam boiler comprising a plurality of side-bysidevertic'al tube-like vessels closed at the top except for a. stean outlet thereat, the tops of all of the said vessels being at: substantially the same elevation; a distribution header connected with the bottom of each of said. vessels; Walls enacting with the lower portions of the vessels to define al combustionv chamber so that the lower portions of sa'id vessels are subject to the direct radiant heat of revin the combustion chamber; walls coacting with the pper portions of the vessels defining a passage for hot lueY gas. rising from the combustion chamber; shorter upright tube=like vesselsv disposed side by side in said passage, said shorter vessels also being closed at their tops except forlsteain outlets thereat and having their tops at substantially the' same common level as the first designated tube-like vessels; pipes connecting the lower ends of the shorter vessels with the distribution header; pipes connecting the steam outlets of all of the vessels; duct means connecting all of the vessels with one another at a. comon elevation a substantial distance belowvthi'r tops; adowneomer connecting said duct means with the heder towhich the bottoms of the vessels are connected; means. for maintaining water in the vessels to a level nohigher than that of said duct means so that the upper portions of the vessels. above said duct means collectively provide thesteam space of the boiler; and extended sur face on the exterior of the shorter vessels below the water level and on the exterior of those portions of the longer vessels which lie below the water level and above the combustion zone, said extended surface abstracti'ng suicient heat energy from the rising hot flue gases to render the saine incapable of destructive burning of the dry wall surfaces of the vessels dening the steam spacer References Cited in the tile of this patent UNITED STATES PATENTS Bailey et al. Dec; 3, 1895

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