US2037493A - Heavy duty steam generator - Google Patents

Description

April 14, 1936. R B|ERSACKETAL 2,Q37,493

HEAVY DUTY STEAM GENERATOR Filed March 21, 1954 2 Sheets-Sheet l INVENTORS RICHARD Bmgzsncn nnn. Kmy. 5cm? DER B 1% ATTORNEY "5 2". E n 1 4/ L m\ um a, Z v R m@ WITNESSES 6. i6.

April 14, 19136. BIERSACK ET AL 2,037,493

HEAVY DUTY S'TEAM GENERATOR Filed March 21, 1954 2 Sheets-Sheet 2 F'is.2.

I F i 3 INVENTORS EHTZSSSES RICHARD B15 sncK m T K9131? SCHR DER ATT/ORNEY Patented Apr. 14, 1936 UNITED STATES PATENT OFFICE HEAVY DUTY STEAM GENERATOR Application March 21,

1934, Serial No. 716,670

In Germany December 23, 1932 11 Claims.

Our invention relates to heavy duty steam generators with forced passage of the operating medium, and more particularly to such steam generators whose heating surfaces are subdivided into radiation heating surfaces and contact heating surfaces.

The common characteristic of all modern constructions for heavy duty boilers lies in the fact that, in contradistinction to the previous steam generators, the greater part of the heat supplied by the fuel is given up directly to the heating surface by radiation and not by contact. The contact heating surfaces follow the radiation heating surface in the path of the flue gas, and the quantity of heat of the flue gas remaining after the heat of radiation has been given up isutilized in the contact heating surfaces. Since the volume of the radiation heat chamber increases with the cube of'the dimensions, whereas the combustion chamber jacket increases only with the square it will be apparent that the ratio between the capacity of the combustion chamber and the heating surface becomes more and more unfavorable with increasing size of the boiler.

' The result is that the heat which may be developed in the furnace cannot be carried off when departing from a given size of the boiler even though the walls of the combustion chamber are completely lined with tubes so that for this very reason one is compelled to load the combustion chamber to a slighter extent, 1. e., to enlarge accordingly the combustion chamber for a given boiler output. A method resorted to in overcoming the above difiiculties consisted in increasing the ratio of the heating surface to the capacity of the combustion chamber by subdividing the combustion chambers by means of partitions formed of radiation tubes. It is true that the conditions are thereby improved from a theoretical point of View.

However, this method entails considerable constructional difficulties and is not suitable for a satisfactory operation, inasmuch as this method independent steam generation elements with radiation heating surface and, if desired, contact heating surface, which elements cooperate with a common contact heating surface and are preferably arranged around this common con- I tact heating surface. By the present invention 5 not only is it possible to attain favorable conditions for the distribution of heat in the radiation heating chambers but it also permits above all to render the furnace operating with overpressure operative for heavy duty boilers. In the boiler plants hitherto employed greater outputs could not be obtained owing to the constructional difficulties resulting from the relatively high overpressure of the combustion chamber.

A further important advantage of the invention is that each partial steam generator may be shut down without interfering with the operation of the other partial steam generators.

Further advantages of the novel construction will be apparent as the description proceeds.

In the accompanying drawings an embodiment of our invention is illustrated in diagrammatic form.

Fig. 1 shows a. longitudinal sectional view of a steam generator;

Fig. 2 a cross-section of the same; and

Fig. 3 a connection diagram.

The steam generator shown in Fig. 1 is a generator with forced passage of the operating medium having a furnace operating with overpres- 30 sure. The steam generator mounted on supports I is surrounded'by a pressure-tight jacket 2 which forms with an inner jacket 3 a circular air jacket 4. Around a centrally arranged jacket 5 an annular space 6 is formed which is subdivided by radial sheet-iron plates 1 into single segments. The plates are welded to the jacket 5 as indicated at 8 (Fig. 2) but they do not contact with the jacket 3 in order to permit radial expansion of the same, when heated during operation. The single partial steam generators consisting of a radiation heating surface 9 and a contact heating surface In associated therewith are arranged according to the invention between the radial sheet iron plates 1. The radiation heating surface 9 is wound in the form of a helix, i. e., in the form of a ribbon consisting of a small number of parallel tubes. The operating medium flows through the radiation heating surface in the direction of the arrow ll.

The operating medium leaves the heating surface through the conduit I2 and enters the contact heating surface ID at I3, through which the operating medium flows in the direction of the arrow 14. The operating medium is carried off utilized in the gas turbine I 9 as to cover not only .in the cylindrical jacket 5.

by the conduit l5. Also the other partial steam generators amounting to eight in the embodiment shown in Fig. 2 are designed in the same manner as the above-described partial steam generator. The contact heating surface cooperating with the eight steam generators is de noted by the numeral I6 and it is assumed that the heating surface Iii is the preheating surface. The operating medium is, consequently, heated at first in the heating surface l 6, then enters the heating surface 9, from where it passes into the heating surface It and then leaves the boiler. The zone of conversion of the ope-rating medium from the liquid into the vaporous state lies in the partial steam generator. Whether the zone is located in the contact portion or in the radiation portion or whether it is subdivided in such a manner that one portion lies in the radiation portion and the other in the contact portion depends upon the operating conditions. If the steam generator is designed for producing steam at critical pressure and at critical temperature the zone of conversion will have to be probably placed in the contact portion. When operating in the undercritical zone it will probably be preferable to place a portion of the zone of conversion in the radiation portion and to effect the complete conversion in the contact portion. The space H which is not occupied as shown in Fig. 1 byoany heating surfaces may, of course, be also utilized. A flue gas-heated intermediate superheater may be, for instance, arranged therein. If the capacity of the jacket 5 is not suiiicient in order to accommodate the remaining portion of the total contact heating surface it is, of course, possible to build in a portion of this heating surface outside of the steam generator in the path of the flue gases.

The steam generator shown in Figs. 1 and 2 is designed for a furnace operating at superatmospheric pressure. Fuel and combustion air are, consequently, supplied at a super-atmospheric pressure in order to attain great loads in the combustion chamber and a great burner output. The

super-atmospheric pressure is produced by means of a compressor l8 which is driven by a turbine 19. In this case, the arrangement is so designed that the flue gases of the individual furnaces of the partial steam generators after they have given up a portion of their heat to the radiation heating surface 9 and to the contact heating surface H3 are supplied to the turbine is for developing power. After leaving the turbine 19 they then pass through the heating surface accommodated The air to be compressed is drawn in through nozzle-shaped inlets 2a and supplied to the furnace 21 through the air jacket 4. The fuel supply is indicated by the arrow 22. By means of the above-described construction pressure-graded spaces are attained,

that is to say the air jacket has maximum pressure, the combustion chambers have less pressure and the common chamber for contact heating surface the minimum pressure. The different stages of pressure assure sealing and prevent the infiltration of air with consequent heat loss.

The essential feature of this arrangement lies in the fact that as a result of the high tempera tures such a great temperature gradient may be the power required for the compressor for each load but also additional power may be available for other purposes. One is, therefore, not dependent upon any auxiliary power, since the compressor power of the gas turbine is at least available at any time. How the available excess power is utilized and how it may be chosen depends upon the requirements to be met by the steam generating plant. Besides the compressor, other auxiliary pumps of the plant (feed pump, cooling water pump and fuel pump) may be, for instance, coupled with the turbine or a generator may be associated therewith so as to supply the auxiliary drives with electrical energy. The excess power may, however, be also produced in the form of excess compressed air and the compressed air may be then used either as operating medium for the auxiliary engine or for other purposes. Owing to the available excess power of the turbine IS a very simple method is, consequently, attained for covering the auxiliary needs of the central power plant.

The above-described construction of the steam generator requires, of course, constructional measures which are not required for other types of boilers. Below some of these measures are particularly indicated. While the cylindrical jackets 2 and 3 are cooled, that is to say, they are not subjected to very high temperatures and are, besides, allowed to freely expand both in the axial and radial direction, the cylindrical jacket 5 is subjected to a relatively high temperature and cannot expand to the desired extent. To avoid excessive stresses of the cylindrical jacket 5 in a longitudinal direction due to heat, the righthand end of the jacket is designed in the form of a corrugated tube 23, which compensates for longitudinal expansion effects. In the embodiment shown, the guide blades of the compressor [8 are carried by the annular portion 26 of the rigid inlet Zii, whereas the guide blades of the turbine l 9 are carried by a rigid intermediate piece 25. A seal (not shown in detail) is provided as indicated at 26 between the turbine and the compressor. In order to guide the flue gases in front of the turbine a cylindrical guide body 2'! is provided which is reinforced by ribs 28. Behind the turbine I9, is mounted in the same manner an outer guide cylinder 29 which carries an inner hollow guide body 35 provided with ribs 30. In order to remove the turbine, it is only necessary, after loosening the connections, to remove the inlet 20 which is provided with the bearing 33 for the runner 34. Thus it will be seen that'the blading of the turbine I9 is arranged at the throat region of a converging-diverging passage so that adequate velocity is given to the gas to act on the blading.

To reassemble and to dismantle the heating surfaces of the individual partial steam generators it is preferable to support the walls of the heating surfaces by ledges by welding the turns or at least some of them so that the heating surfaces form self-supporting structures. The heating surfaces may then be removed from the left-hand side after removing the ignition members 45, burners, cover closures etc. It is preferable to slightly taper the spaces of the single partial steam generators in order to facilitate the assemblage and dismantling of the parts. Besides, it is not necessary to provide any space for the removal of the heating surfaces behind the steam generator corresponding to the total length of the heating, surfaces but only corresponding to the length of the radiation portion, since the radiation heating surfaces may be welded together during the assemblage after positioning the contact heating surface, and when removed for repair they may be out between the radiation heating surface and the contact heating surface, so that both parts may be removed one after the other.

The individual partial steam generators are connected to a ring conduit from which a number of conduits 36 branch off corresponding to the number of the parallel tubes, unless it is preferable to branch off from a single conduit and to effect the distribution over the parallel tubes of the heating surface 9 by means of a manifold at the conduit itself. The conduits l5 enter a ring pipe 31. Each of the conduits 36 is equipped with a valve 38 and each of the conduits l5 with a valve 39; besides, conduits 40 provided with stop valves 4| branch off from the conduits I5. The feed water is supplied through the conduit 42 provided with the stop valve 44 and passes after flowing through the heating surface I6 into the ring pipe 35 through the conduit 43.

The above-described arrangement of valves renders the individual partial steam generators independent of one another, for if one of the individual partial steam generators should be damaged the latter may be shut down by closing the valves 38 and 39 after cutting off the fuel and air supply without thereby affecting the operation of the other partial steam generators.

To draw off the deposit from a partial steam generator the fuel and heat supply is at first reduced, or, if desired, completely cut off and then the valve 39 is closed and the valve 4| opened. The partial steam generator is then cut off from the ring pipe 31 but is just the same as before connected to the ring pipe 35. The zone of conversion assumes now another position within the heating surface and the salts are discharged through the conduit 40 from the partial steam generator. After the deposits have been removed the valve 39 is again opened and the valve 4| closed and then the normal fuel and air supply may be again turned on.

The flue gases leave the steam generator through the flue gas conduit 46.

In case the winding of the contact heating surface Hl should be too difficult owing to the small inner winding diameter, a core 41 consisting of refractory material; for instance, refractory clay as shown in Fig. 2 may be inserted in the contact heating surface in order to bring the free path of flue gas in the center of the heating surface.

Before describing the regulation of the steam generator it may be pointed out that the power of the compressor developed by the turbine l9 may bemostly employed to overcome the resistance to flow in the contact heating surfaces l0 and Hi. In these heating surfaces a very strong whirling of the gases is caused which produces an extremely intense transfer of heat. This transfer of heat to the heating surface I0 is still further increased by the increased pressure so that very small contact heating surfaces are sufficient as compared to the other types of boilers. Furthermore, a relatively small cross-section is obtained for the flue gas pipe 48, since in the latter a very high speed of flow is also available which by the use of a diffusor may be again converted into pressure and utilized. Furthermore, due to compression of the air and to the velocity thereof, the flow area of the jacket 4 may be kept at a minimum with the result that the outer dimensions of the boiler are minimized.

From the above, it will be apparent that steam generators according to the invention are characterized by the simple and compact construction, since they permit high heat stressings of the heating surface and are, consequently, not

only particularly advantageous for great outputs but also for the reason that breakdowns of the complete plant are practically prevented by the subdivision of the steam generator into individual independent steam generators. The velocity of the flue gases may be so high as to amount to approximately 100 m/sec., but it is much lower than the speed of flue gases of the high-power boilers hitherto known. Nevertheless the same or even a smaller total weight and above all a considerably smaller total volume may be employed, since, on the one hand, the combustionchamber capacity which is decisive for the total space requirements may be limited to the utmost and, on the other hand, the novel construction ensures the use of forced passage of the operating medium and above all of the cross-current, i. e., a direction of the flue gas perpendicular to the axis of the tube (contact heating surface Ill and I6). It is the use of the cross-current which renders it possible to arrange the tubes in such a manner that the total tubular system has a certain flexibility, whereas, for instance, multi-tubular boilers are practically considered as rigid units and, consequently, are subjected to very high heat stressings and are also not suitable for high pressures, unless expensive and complicated special constructions are employed.

In the embodiment shown in the drawings, it is assumed that the boiler runs on oil or gas. Should the boiler run on pulverized coal the use of the above-described turbine drive must be probably dispensed with, for the blade material of the turbine would be exposed to great wear and tear. In this case, a particular driving engine, perhaps in the form of a steam turbine would have to be provided for the drive of the compressor. It is, of course, not absolutely necessary to couple the compressor directly with the steam generator, although this arrangement for the steam generator would doubtless be the most convenient. Even the manner how the air supply to the boiler is controlled is not of any particular importance. It may be, however, convenient to effect the regulation of air supply by means of a by-pass H provided with a valve 12, i. e., in such a manner that with decreasing consumption of air the quantity of air to be resupplied through the by-pass H increases and reversely. In this manner a regulation of the power of the compressor set is at the same time effected.

We claim as our invention:

1. In apparatus of the character described, means providing a plurality of first-pass heating chambers in communication with a secondpass heating chamber, combustion means for each first-pass chamber, tubular heating surface elements in the first and second-pass chambers, the tubular elements in the first-pass chambers each including a radiant heat-absorbing portion adjacent to the combustion means and a contact heat-absorbing portion more remote therefrom, and means for passing medium to be heated first through the tubular element in the second pass chamber, next through said radiant portion or portions, and then through said contact portion or portions.

2. In apparatus of the character described, means providing a group of elongated first-pass heating chambers disposed in parallel relation and communicating with a second-pass heating chamber, combustion means for each of the firstpass heating chambers and so disposed that heating medium generated thereby flows along the first-pass chambers and then through the second-pass chamber, tubular heating surface elements in the first-pass chambers and each including a radiant heat-absorbing portion connected to a contact heat-absorbing portion, the radiant heat-absorbing portions being disposed adjacent to the combustion means and having the tubing thereof arranged to facilitate the passage of heating medium along the first-pass chambers and the contact heat-absorbing portions having the tubing thereof so disposed and arranged as to promote contact of heating medium therewith, a tubular heating surface element in the second-pass heating chamber, and means providing for flow of medium to be heated through the tubular elements and including inlet and outlet conduits connected to the opposite ends of each of the tubular elements disposed in the first-pass heating chambers, and discharge means associated with each of said outlet conduits and operative to provide for flushing out the tubular elements in the first-pass heating chambers.

3. In apparatus of the character described, means providing a plurality of first-pass heating chambers in communication with a second-pass heating chamber, combustion means for each first-pass chamber, tubular heating elements in the first and second-pass chambers, the tubular elements in the first-pass chambers each including a radiant heat-absorbing portion adjacent to the combustion means and an axially-aligned contact heat-absorbing portion more remote therefrom, the tubing of the radiant heat-absorbing portions being arranged to facilitate the flow of heating medium and that of the contact heatabsorbing portions being so arranged as to promote the contact of heating medium therewith, means for supplying medium to be heated to the tubular element in the second-pass chamber, means for conducting medium from the latter element to the ends of the radiant heat-absorbing portions which are adjacent to the combustion means, means for conducting medium from the other ends of the radiant heat-absorbing portions to the ends of the contact heat-absorbing portions remote from the radiant heat-absorbing portions, whereby medium flows through radiant heat-absorbing portions toward the contact heat-absorbing portions and flows through the contact heat-absorbing portions toward the radiant heat-absorbing portions, and discharge means connected to the ends of the contact heatabsorbing portions adjacent to the radiant heatabsorbing portions.

4. In apparatus of the character described, means providing a plurality of first heating chambers in communication with a second-pass heating chamber, combustion means for each firstpass chamber, tubular heating elements in the first and second-pass chambers, the tubular elements in the first-pass chambers including a radiant heat-absorbing portion adjacent to the combustion means and a contact heat-absorbing portion more remote therefrom, means for supplying medium to the tubular element in said second-pass, means for conducting medium from the last-named tubular element to the tubular elements in the first-pass heating chambers, outlet conduits for the last-named tubular elements, discharge means for each of said outlet conduits, and valve means for each outlet conduit and operative to interrupt normal flow therethrough and to provide for flow through the discharge means to provide for flushing of the first-pass tubular elements.

5. In apparatus of the character described,

means providing a plurality of first-pass heating chambers communicating with a second-pass heating chamber, combustion means for the firstpass chambers, tubular heating surface elements in each of said chambers, the tubular surface element in each first-pass chamber including a radiant heat-absorbing portion having one end disposed adjacent to the combustion means and having its other end connected to a contact heat-absorbing portion, the tubing of each radiant heat-absorbing portion being Wound so that adjacent convolutions are substantially similar to provide a passage facilitating the flow of heating gases and the tubing of each contact portion being wound so that adjacent convolutions are dissimiliar to promote contact therewith of heating gases, and means providing for the passage of medium to be heated first through the secondpass tubular heating surface element, next through the radiant portions of the first-pass tubular heating surface elements and then through the contact portions of the latter elements.

6. The combination as claimed in claim wherein refractory cores are arranged centrally of the contact heat-absorbing portions of the tubular heating surface elements disposed in the firstpass heating chambers and serving to promote contact of heating gases with the tubular convolutions of such contact portions.

7 In apparatus of the character described, an outer tubular wall, end walls joined to the outer tubular wall, an inner tubular wall and having one end joined to one of said end walls, means for connecting the other end of the inner tubular wall to the other end wall and including an element yieldable axially of said inner and outer walls, a plurality of partition walls in the space between the inner and outer walls for dividing said space into a plurality of first-pass heating spaces, said inner wall encompassing a secondpass heating space, means affording communication of the outlet ends of the first-pass heating spaces with the inlet end of the second-pass heating space, a heat source for each of the first-pass heating spaces, heating surface in the firstand second-pass heating spaces, and means providing for the passage of medium to be heated through said heating surface.

8. In apparatus of the character described, an outer cylindrical Wall, end walls for the outer cylindrical wall, an inner cylindrical .wall coaxial with and spaced inwardly from the outer cylindrical wall, one end of the inner cylindrical wall being joined to one of the end walls, means for connecting the other end of the cylindrical wall to the other end wall and including a circumferentially corrugated tubular element, partitions carried by the inner cylindrical wall and dividing the space between the inner and the outer cylindrical walls into a plurality of segmental first-pass heating spaces, the inner cylindrical wall encompassing a second-pass heating space, means affording communication between the outlet ends of the first-pass heating spaces with the inlet end of the second-pass heating space, a flue communicating with the outlet end of the second-pass heating space, combustion means for each of the first-pass heating spaces, heating surface in said heating spaces, and means providing for the passage of medium to be heated through said heating surface.

9. In apparatus of the character described, an outer tubular wall, first and second end walls joined to the outer tubular wall, an inner tubular wall spaced from the outer tubular wall and having one end joined to the first end wall, means including an expansion joint for connecting the other end of the inner tubular wall to the second end wall, means dividing the space between the inner and the outer tubular walls into a plurality of first-pass heating spaces and the inner tubular wall defining a second-pass heating space, all of said heating spaces being disposed in parallel relation, means affording communication between the ends of the first-pass heating spaces and the end of the second-pass heating space adjacent to the second end wall, means extending through the first end wall for supplying combustible media to each of the first-pass heating spaces, tubular heating surface in each of said heating spaces, and means providing for the passage of medium to be heated through said heating surface including conduits connected to the tubular heating surface and extending through said first end wall.

10. In a steam generator, means providing a first and second-class heating chamber, means including a passage affording communication between said heating chambers, a turbine having its blading disposed. in said passage, an air compressor driven by the turbine, combustion means for each of the first-pass chambers supplied with air from the compressor, heating surface in the first and second-pass chambers, and means providing for the passage of medium to be heated through said heating surface.

11. In a steam generator, means providing a plurality of first-pass heating chambers and a second-pass heating chamber, means including a converging-diverging passage affording communication between the outlet ends of the firstpass chambers and the inlet end of the secondpass chamber, a turbine having its blading disposed in the throat region of said passage, an air compressor driven by the turbine, combustion means for each first-pass chamber and supplied with air from the compressor, heating surface in the first and second-pass chambers, and means providing for passage of medium to be heated through said heating surface.

RICHARD BIERSACK. KARL SCHRCSDER.

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