Title of Invention

STEAM GENERATOR

Abstract Steam generator (1) in particular for heating by means of hot exhaust gases, having two or more water/steam circuts (2,3,31,34), In which each water/steam circuit (2,3,31,34) has at least one evaporator (4,5,33,36) to receive the heat from the heating medium, and the water/steam circuits (2,3,31,34) have at feast one watersteam drum (6) and one downcomer pipe(7) in common, having at least one branch (8) in the downcomer pipe (7), from which the pipe sections (9,10,32,35) of the respective water/steam circuits (2,3,31,34) branch off, characterized in that the downcomer pipe (7) is embodied wth a venturi device (11,12) in the area of the branch (6), and the inlet opening (14,37,38) of the pipe section (10,32,35) of at least one water/steam circuit (3,31,34) Is disposed In the area of diffuser-shaped outlet (39) of the venturi device (11, 12), and the pipe section (10,32,35) is embodied as a dynamic pressure pipe in order to increase the pressure of the working medium in this circuit (3,31,34).
Full Text Description Steam Generator
The invention relates to a steam generator, in particular a waste-heat steam generator or boiler for heating by means of hot exhaust gases.
Such steam generators are primarily fed with hot exhaust gases from energy and/or process technology systems, and they often comprise a plurality of water-side pipe sections or circuits that not only have varying geometries but also have widely divergent heat capacities. For this reason, it is often necessary to control the distribution of the circulating water to individual pipe sections or circuits, for example with the aid of flow restrictors.
In the case of forced-circulation steam generators, the distribution of the circulating water to individual water-side pipe sections is controlled by means of orifice restrictors installed at the inlet to the individual heating surface coils or pipe sections (La Mont system). The pressure difference caused by the individual pipe sections and the orifice restrictors must be overcome with the aid of a circulating pump.
Controlling the circulating water in a natural-circulation steam generator is a difficult problem since these steam generators generally lack sufficient pressure difference to allow orifice restrictors to be installed. The available pressure difference in the individual pipe sections or circuits is predetermined by the intensity of heating, the height difference and the pressure loss in the individual pipe sections. In this case, the installation of nozzle or orifice restrictors to improve the distribution of water is based on the idea of restricting the flow of water in the pipe sections that have good circulation in order to increase the circulation of water in the low-circulation pipe sections by means of a lower frictional pressure loss in the common downcomer and riser lines. The total rate of circulation in the system is often greatly reduced in a disadvantageous manner, and only a modest improvement can be achieved for the affected pipe section-in other words, the weakly circulating pipe section.

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The object of the invention is to provide a steam generator in which the water circulation in the individual pipe sections/circuits can be distributed more effectively without having a significant adverse effect on the total water circulation rate in the system
The above object is achieved by the inventive features of the present invention Preferred embodiments of the invention are recited in the description.
The solution offered by the invention provides a steam generator that has the following
advantages:
It can distribute the water circulation rates in each pipe section or circuit as needed by increasing the pressure in the pipe section or sections in which an increase in the circulation rate is necessary or desired, with causing an additional pressure loss due to friction in the pipe section which does not require pressure increase- in other words this measure can
a) compensate for the lack of upward flow in a pipe section or in a plurality of
pipe sections,
b) more successfully overcome an inherently high pressure loss in a pipe section
so that it is more closely matched to the other pipe sections or is matched to
them as completely as possible,
c) supply an evaporator device that is located within a steam generator and that
has relatively high cooling requirements- for example, an end plate or a tube
plate in a firetube boiler- with a relatively high quantity of cooling water,
the pressure increase in the pipe section or in the pipe sections in which an increase in the circulation rate is required can be achieved without the use of and additional pump
In a preferred embodiment of the invention, the venture device comprises a venture nozzle inserted in the downcomer pipe of a water/steam circuit. This makes it easy to configure the downcomer pipe with a standardized, commercially available nozzle, for example an EN ISO 5167-1 venturi nozzle
In a preferred embodiment of the invention, the venture device comprises a downcomer pipe line in the form of a venture pipe. Thus, the venture device is completely integrated .

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in the downcomer line, and, if desired, it can be made of the same material and from a single piece.
Preferably, the steam generator of the invention is operated under natural circulation.
flow. In this mode, one or more water/steam circuits that, for various reasons, has/have
a weaker rate of circulation compared to a different or additional circuits can be
operated at an increased water circulation rate without having to resort to additional
pumps and consequently increasing capital spending, operating, and maintenance
costs.
It is also advantageous to operate the steam generator of the invention with forced circulation. In this mode, one or more water/steam circuits that, for various reasons has/have a weaker rate of circulation compared to a different or additional circuits, can be operated at an increased water circulation rate
In one preferred embodiment of the invention, the ratio of the inside diameter d of the venturi nozzle device at its narrowest cross section to the inside diameter D of the downcomer pipe is between 1.0 and 0.01. This embodiment ensures that the effect of an increased water flow rate is established in the circuit whose inlet is located in the diffuser-shaped outlet of the venturi nozzle device. Examples of the invention are illustrated in greater detail below based on the drawings and the description.
The drawings show:
oFig 1 a schematic diagram of a waste-heat steam generator in the form of a firetube boiler as a side view and, partially in a longitudinal cross-sectional view,
Fig 2 a branch on the downcomer line of the steam generator according to Detail A of Figure 1 with two pipe sections,
Fig. 3 as in Figure 2, but an alternative design,

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Fig. 4 as in Figure 2, but an alternative design having more than two pipe section or circuit lines,
Fig. 5 as in Figure 4, but an alternative design, Fig. 6 section B-B shown in Figure 5,
Fig. 7 schematic diagram of a waste-heat steam generator in the form of a watertube boiler in a longitudinal sectional view.
Figure 1 shows a steam generator 1, embodied as a firetube boiler. It represents a waste-heat steam generator. The steam generator 1 essentially comprises a vertically disposed water space 29, which is laterally limited by a jacket 27 and by end or tube plates 23, 24 on the top and bottom. The water space 29 has at least one bundle of firetubes 30 passing through it that are disposed between the end plated 23 and 24 in a gas-tight manner and essentially are oriented in a vertical direction. The heating medium or. hot exhaust gas that is needed to heat the water located in the water space
29 is supplied to the steam generator 1 via an inlet 21 and the gas inlet chamber 22
From the inlet chamber 22, the heating gas travels to the firetubes 30 that extend
through the water space 29, and in the process transfers heat to the water located in the
water space 29. Then the cooled heating medium passes through the gas outlet
chamber 25 into the outlet 26, from where it can be routed to additional process steps,
which are not shown. Figure 1 shows how the hot exhaust gas travels from the top to
the bottom through the steam generator 1. Depending on requirements, it can also
travel from the bottom to the top. The water space 29 together with the firetube bundle
30 and both of the two plates 23, 24 comprise the evaporator device 4 of the first
water/steam circuit 2'.
The steam qenerator 1 shown in Figure 1 has two water/steam circuits or pipe.sections,

2, 3. From the water/steam drum 6, which is supplied with feedwater through a line that

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is not shown, the water travels through a common downcomer pipe 7, which extends away from the drum 6 and is designed in an essentially vertical orientation. This occurs via the branch 8 into the two water/steam circuits 2, 3. The pipe section 9 that extends from the branch 8 and is part of the first circuit 2 conveys the water through the inlet 15, which is located in the immediate vicinity of the lower end plate 24, into the water space 29. The water or steam, which is flowing upward as a result of heating and the resulting buoyancy, is directed in the area of the upper end plate 23 through the outlet 16 out of the water space 29 and is fed to the drum 6 via pipe section 9 and riser pipe 19. Steam that has already been generated can be supplied from the drum 6 by means of a line 28 to a superheater (not shown) in the steam generator 1, or it can be sent elsewhere for a different purpose. The unevaporated water from the drum 6 is routed back into circuits 2, 3 via the downcomer line 7.
The pipe section 10 that leads away from the branch 8 and that is part of the second water/steam circuit 3 shown in Figures 1 to 3 is embodied in the invention in such a way that the inlet opening 14 of pipe section 10' is disposed just downstream from the narrowest cross section of the venturi device 11, 12-in other words, in the area of the diffuser-shaped outlet 39 and in the middle of the downcomer line 7, and pipe section 10 is embodied as a dynamic pressure pipe. When pipe section 9 continues axially as shown in Figure 2, pipe section 10 is advantageously routed away in a direction that is essentially perpendicular to line 9. As a result of the dynamic pressure of the flowing fluid caused by the venturi device 11, 12, the apparatus of the invention causes a pressure increase at the inlet 14 of the second circuit 3 or of pipe section 10, in that the water throughput is systematically adjusted to a higher level. The venturi device 11,12 either comprises a standard venturi nozzle 11 that has a shape that is favorable to flow, for example DIN EN ISO 5167-1 with a specified diameter (Figure 2) or a downcomer pipe 7 in the shape of a venturi tube 12 (Figure 3), in which the static pressure of the fluid is restored when the cross section increases. The flow velocity, and thus the dynamic pressure upstream from the pipe section 10 that is embodied as a dynamic pressure pipe, is increased with the aid of the venturi device 11, 12. The high flow velocity is reduced again in the diffuser 39 of the venturi device 11, 12, and the static pressure increases. The increased dynamic pressure at inlet 14 in the second

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water/steam circuit 3 therefore is only produced by the conversion of the kinetic energy of the flowing medium in downcomer pipe 7 without causing an additional frictional pressure loss as a result of a restriction in the first water/steam circuit 2 or in the inlet 13 to pipe section 9.
The apparatus of the invention therefore causes a pressure increase to occur in the
second circuit 3, without the need for an additional pump. In the present example, the
upward flow of the natural circulation system is optimally used for adjusting the desired
water distribution within water/steam circuits 2, 3 of steam generator 1. The water flow
rate that is now increased in the second circuit 3 is transported by pipe section 10 into
the water space 29 of the steam generator 1 in such a way that pipe 10 terminates in a
centered position relative to tube plate 23 directly below tube plate 23, and the water is
forced from below against tube plate 23, which is heated to an especially great extent
by the heating medium that enters the inlet chamber 22. This measure is able to reliably
cool tube plate 23, which is threatened by high thermal loads, and the production of
steam in the steam generator 1 can be maintained without interruptions or relatively
frequent maintenance intervals.
After the water leaves pipe section 10 of the second circuit 3 and enters the water space 29 through the water chamber inlet 17 and after it in some cases has partially evaporated, the water/steam mixture, together with the water/steam mixture from the first circuit 2, flows through the water chamber outlet 16, 18 via pipe section 9 and riser pipe 19 into the drum 6. The evaporator device 5 of the second circuit 3 essentially comprises the water space 29 and the upper tube plate 23.
However, pipe section 10 of the second circuit 3 can also be routed away from the venturi device 11, 12-in other words, in the axial direction of downcomer pipe 7. In this case, pipe section 9 of the first water/steam circuit 2 is generally routed away perpendicular to downcomer pipe 7.
Thus, the two circuits 2, 3 are brought together in the water space 29 in the steam generator shown in Figure 1, and, by means of a shared outlet 16, 18 of a shared outlet

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pipe 9/10, 19/20 are fed into the drum 6. However, if the two circuits 2, 3 are not brought together (in other words, circuits 2, 3 each have separate evaporators 4, 5), the respective circuits can also be routed to the drum 6 by means of separate outlets 16, 18 as well as pipe sections and riser pipes 9, 19 and 10, 20.
If there are more than two circuits within a steam generator 1, Figure 4 shows that two
or more branches 8 disposed following one another in the direction of flow in
downcomer pipe 7, each equipped with a venturi device 11, 12, can be disposed in
downcomer pipe 7. Figure 4 shows, in addition to the two circuits 2,3,a third
water/steam circuit 31 which, like the second circuit 3, experiences an increased water
circulation rate. The working medium enters the third pipe section 32 through inlet
opening 37 in the area of the diffuser 39 on the second branch 8, and it is sent to a third
evaporator device 33 so that pipe section 32 can carry it to the drum 6.
Figure 5 shows that, instead of using a pipe section in the area of the venturi device 11, 12, it is possible to provide a number of different pipe sections 10, 32, 35 for a number of different circuits 3, 31, 34 This will increase the water flow in circuits 3, 31, 34. The inlet openings 14, 37, 38 of pipe sections 10, 32, 35 are also disposed in the vicinity of the diffuser 39 of the venturi device 11, 12 in such a way that the three inlet openings 14, 37, 38 all are located in the center of the downcomer pipe in order to achieve a uniform distribution of flow among the individual pipe sections 10, 32, 35. The pipe sections 10, 32, 35 each proceed essentially perpendicular to the downcomer pipe 7.
Figure 7 shows an additional version of a steam generator 1 of the invention. The steam generator shown in Fig. 7 is also a waste-heat steam generator, but it does not use a firetube boiler, but rather a watertube boiler. The steam generator 1 has an essentially vertical gas stack 40, which is essentially comprised of water-cooled tubular walls and forms the evaporator 4 of the first water/steam circuit 2 of two existing circuits. The

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working medium, water, is fed from the drum 6 via the downcomer pipe 7 through the inlet opening 13 of pipe section 9 to the evaporator 4, where it is partially evaporated and then sent back to the drum 6 via pipe section 9.
The working medium of the second circuit 3 is transported at branch 8 through the inlet opening 14 to pipe section 10 and thence to the evaporator 5, which are [sic] embodied as contact heating surfaces and are [sic] disposed in the gas stack 40. After partial evaporation of the water, the working medium returns to the drum 6 via pipe section 10. In the invention, the circulation of water in the second water/steam circuit 3 through the venturi device 11, 12 located at branch 8 of downcomer pipe 7 is increased. The heating medium or hot exhaust gas passes through inlet 21 in the bottom of the gas stack 40 of the steam generator 1, and it flows through the gas stack 40 from the bottom to the top before it is sent to additional process steps at the outlet 26. When the heating medium flows through the gas stack, heat is transferred into the tubular walls and the contact heating surfaces-in other words into evaporator units 4 and 5
If the apparatus of the invention is used in a forced circulation steam generator 1 (not shown), then the venturi device 11, 12 is advantageously located downstream from the circulating pump located in downcomer pipe 7. In a forced circulation system, downcomer pipe 7 is essentially a vacuum pipe upstream from the circulating pump and a pressure pipe downstream from the pump, just like the riser pipe 19, 20. In the forced circulation design as well as in the natural circulation design, the water circulation rate in the second circuit 3 is increased by means of the venturi device 11, 12.
As already discussed above, venturi nozzles or classical venturi pipes 12 such as those used to measure fluid flow rates in the case of DIN EN ISO 5167-1 restrictors, can be used When viewed in the direction in which the fluid or water working medium flows, the venturi devices 11,12 possess an inlet cone, a cylindrical necked section having an inside diameter of d (narrowest cross section), and a diffuser 39, and, instead of the

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inlet cone, an inlet curvature matching that of DIN EN ISO 5167-1 venturi nozzle is possible, and the neck section, which forms the narrowest cross section, may not be cylindncally shaped. The openings for measuring flow in the neck section may need to be eliminated. However, any other venturi device that deviates from this standard and that has a narrowed section and a diffuser part may be used. In order to ensure that there is an increased water circulation rate in the water/steam circuits 2, 3, 31, 34 in which an increased water circulation rate is desired, the ratio of the inside diameter d of the venturi device 11, 12 at its narrowest cross section to the inside diameter D of the downcomer pipe 7 may lie between 1.0 and 0.01.

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List of Reference Numbers:
1 Steam generator
2 Water/steam circuit 1
3 Water/steam circuit 2
4 Evaporator, circuit 1
5 Evaporator, circuit 2
6 Water/steam drum
7 Downcomer tube or pipe
8 Branch
9 Pipe section circuit 1
10 Pipe section circuit 2
11 Venturi nozzle
12 Venturi pipe
13 Inlet opening for pipe section 1
14 Inlet opening for pipe section 2
15 Water chamber inlet circuit 1
16 Water outlet circuit 1
17 Water chamber inlet circuit 2
18 Water outlet circuit 2
19 Riser tube or pipe circuit 1
20 Riser tube or pipe circuit 2
21 Inlet for hot exhaust gas or flue gas
22 Gas inlet chamber
23 Water chamber-end plate or tube plate, gas inlet
24 Water chamber-end plate or tube plate, gas outlet
25 Gas outlet chamber
26 Outlet cold exhaust gas or flue gas
27 Jacket
28 Line between drum and superheater
29 Water space
30 Firetube bundle

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31 Water/steam circuit 3
32 Pipe section circuit 3
33 Evaporator, circuit 3
34 Water/steam circuit 4
35 Pipe section circuit 4
36 Evaporator, circuit 4
37 Inlet opening for pipe section 3
38 Inlet opening for pipe section 4
39 Diffuser-shaped outlet from venturi device
40 Gas stack
41

-12-WE CLAIM
1. Steam generator (1) in particular for heating by means of hot exhaust
gases, having two or more water/steam circuits (2,3,31,34), in which each
water/steam circuit (2,3,31,34) has at least one evaporator (4,5,33,36) to
receive the heat from the heating medium, and the water/steam circuits
(2,3,31,34) have at least one watestream drum (6) and one downcomer
pipe(7) in common,
having at least one branch (8) in the downcomer pipe (7), from which the
pipe sections (9,10,32,35) of the respective water/steam circuits
(2,3,31,34) branch off,
characterized in that the downcomer pipe (7) Is embodied with a venturi
device (11,12) m the area of the branch (8),
and the inlet openmg (14,37,38) of the pipe section (10,32,35) of at least
one water/steam circuit (3,31,34) is disposed in the area of diffuser-
shaped outlet (39) of the venturi device (11, 12), and the pipe section
(10,32t35) is embodied as a dynamic pressure pipe in order to increase
the pressure of the working medium in this circuit (3,31,34).
2. The steam generator as claimed in claim 1, wherein the venturi device
comprises a venturi nozzte (11) inserted in the downcomer pipe (7).
3. The steam generator as claimed in claim 1, wherein the venturi device
comprises a downcomer pipe (7) embodied as a venturi pipe (12),
4. The steam generator as claimed in claim 1 to 3, wherein the steam
generator (1) can be operated in natural circulation mode,
5. The steam generator as claimed in claim 1 to 3, wherein the steam
generator (1) can be operated in forced circulation mode.


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6, The steam generator as claimed in one of claim 1 to 5, wherein the ratio of the inside diameter d of the venturi device (11, 12} at its narrowest crossed section to the inside diameter of the D of the downcomer piper (7) lies between 1.0 and 0,01.
Steam generator (1) in particular for heating by means of hot exhaust gases, having two or more water/steam circuts (2,3,31,34), In which each water/steam circuit (2,3,31,34) has at least one evaporator (4,5,33,36) to receive the heat from the heating medium, and the water/steam circuits (2,3,31,34) have at feast one watersteam drum (6) and one downcomer pipe(7) in common, having at least one branch (8) in the downcomer pipe (7), from which the pipe sections (9,10,32,35) of the respective water/steam circuits (2,3,31,34) branch off, characterized in that the downcomer pipe (7) is embodied wth a venturi device (11,12) in the area of the branch (6), and the inlet opening (14,37,38) of the pipe section (10,32,35) of at least one water/steam circuit (3,31,34) Is disposed In the area of diffuser-shaped outlet (39) of the venturi device (11, 12), and the pipe section (10,32,35) is embodied as a dynamic pressure pipe in order to increase the pressure of the working medium in this circuit (3,31,34).

Documents:

00195-cal-2002 abstract.pdf

00195-cal-2002 claims.pdf

00195-cal-2002 correspondence.pdf

00195-cal-2002 description(complete).pdf

00195-cal-2002 drawings.pdf

00195-cal-2002 form-1.pdf

00195-cal-2002 form-18.pdf

00195-cal-2002 form-2.pdf

00195-cal-2002 form-26.pdf

00195-cal-2002 form-3.pdf

00195-cal-2002 form-5.pdf

00195-cal-2002 letters patent.pdf

00195-cal-2002 priority document others.pdf

00195-cal-2002 priority document.pdf

00195-cal-2002 reply f.e.r.pdf

195-CAL-2002-FOR ALTERATION OF ENTRY.pdf

195-CAL-2002-FORM-27.pdf


Patent Number 205515
Indian Patent Application Number 195/CAL/2002
PG Journal Number 14/2007
Publication Date 06-Apr-2007
Grant Date 05-Apr-2007
Date of Filing 03-Apr-2002
Name of Patentee ALSTOM POWER ENERGY RECOVERY GMBH
Applicant Address ELLENBACHER STRASSE 10, 34123 KASSEL, GERMANY, A GERMAN COMPANY
Inventors:
# Inventor's Name Inventor's Address
1 JIRI, JEKERLE FINKENSTR. 5, 34225 BAUNATAL, GERMANY
PCT International Classification Number F 22B1/18
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10117989.8-24 2001-04-10 Germany