Title of Invention

A STEAM GENERATOR , IN PARTICULAR, A WASTE HEAT STEAM GENERATOR AND METHOD FOR OPERATING THIS STEAM GENERATOR

Abstract

Steam generator, in particular waste-heat steam generator, and method for operating this steam generator A first (5, 9) and a second (8) evaporator heating surface are located in an elongate gas flue (2) for hot gas of a steam generator. A first supply line (10) for feed water is throughflow-connected on the inlet side to the first evaporator heating surface (5, 9), whilst the second evaporator heating surface (8) is throughflow-connected on the inlet and the outlet side to a low-pressure drum (7) . The low-pressure drum (7) is provided with a second supply line (6) for feed water. The first supply line (10) has a first treatment point (47) and the second supply line (6) a second treatment point (46); each of the two treatment points serves for adding and/or extracting chemicals for water treatment, so that each evaporator heating surface (5, 9, 8) can receive only feed water which is conditioned according to the regulations applying to the said evaporator heating surface.

Full Text

Description -1A- The invention relates to a steam generator, in particular a waste-heat steam generator, with an elongate gas flue, which has an inflow end for hot gas and an outflow end for the cooled hot gas, and with a first evaporator heating surface, to which a first supply line for feed water is throughflow-connected on the inlet side and which, as seen in the throughflow direction of the hot gas, is located on the gas flue upstream of a second evaporator heating surface which is throughflow-connected both on the inlet and on the outlet side to a low-pressure drum provided with a second supply line for feed water. A steam generator of this type is known from P J Dechamps and J-F. Galopin, "Once-through Heat Recovery Steam Generators working with Sub- and Supercritical Steam Conditions for Combined Cycles", ASME Paper 97-GT337, International Gas Turbine & Aeroengine Congress and Exhibition, Orlando, Florida, June 2nd to June 5th, 1997, in particular page 7, left-hand column, second paragraph. When the hot gas has high temperatures, the higher pressure stage of this steam generator, the said pressure stage being operable in the once-through mode and including the first evaporator heating surface, also makes it possible to implement high operating pressures up to supercritical states. This allows improved efficiency. Furthermore, the higher pressure stage requires, at most, only a relatively thin-walled water separation bottle at the steam outflow of the first evaporator heating surface, so that faster startup times of the steam generator and faster reactions of this steam generator to load changes are possible. - 2 - The second evaporator heating surface, together with the low-pressure drum assigned to it, is operated in the circulating mode and utilizes the low temperature which the hot gas still has after passing through the first evaporator heating surface. This too leads to an improvement in efficiency. On account of the low pressure in the low-pressure drum, the latter can likewise be relatively thin-walled. It is therefore no obstruction either to fast start-up times or to the fast reaction of the steam generator to load changes. Also, the circulating flow in the second evaporator heating surface has no instabilities and does not lead to any erosions in this second evaporator heating surface. However, the first evaporator heating surface operated in the once-through mode requires different conditioning of the feed water from that of an evaporator heating surface operated in the circulating mode, that is to say from that of the second evaporator heating surface connected to the low-pressure drum both on the inlet and on the outlet side. The object on which the invention is based is to ensure that both the first evaporator heating surface operated in the once-through mode and the second evaporator heating surface operated in the circulating mode receive only the feed water which is conditioned for them. To achieve this object, according to the invention, a steam generator of the type mentioned in the introduction has the features of the characterizing clause of Patent Claim 1. By means of chemicals which are added to and/or removed from the first treatment point of the first supply line, the feed water for the first evaporator heating surface can be conditioned according to the requirements of this first evaporator heating surface, whilst, by adding and/or removing chemicals at the second treatment point of the second supply line, the feed water for the second evaporator heating surface can be conditioned according to the - 3 - requirements of the latter. Both supply lines can therefore be connected to the same common feed-water supply arrangement. This feed-water supply arrangement can deliver initial feed water of uniform initial quality and may, for example, be a hot well, a feed-water treatment plant or a condensate collecting vessel. In the development of the steam generator according to Patent Claim 3, feed water conditioned in the first supply line may be reconditioned for the second evaporator heating surface. In the development of the steam generator according to Patent Claim 4, the feed water in the first supply line may be preconditioned for both evaporator heating surfaces by means of chemicals which are added to the first supply line at the first treatment point. By means of chemicals added to the second supply line at the second treatment point, feed water preconditioned for both evaporator heating surfaces from the first supply line may be reconditioned for the second evaporator heating surface. Finally, feed water in the first supply line, which is already preconditioned for both evaporator heating surfaces, may be reconditioned for the first evaporator heating surface at the third treatment point by the addition of further chemicals. By means of the development of the steam generator according to Patent Claim 5, the feed water for the first evaporator heating surface may be accurately conditioned by the addition of chemicals at the first treatment point and the feed water for the second evaporator heating surface may be accurately conditioned by the addition of chemicals at the second treatment point. The declaration vessel referred to in Patent Claim 6 may advantageously be integrated in the low-pressure drum which is provided with the second supply line for feed water. - 4 - Patent Claim 7 specifies an advantageous method for operating the steam generator according to the invention. Patent Claim 8 is directed at a modification of this method for the steam generator according to Patent Claim 3, Patent Claim 9 at a modification for the steam generator according to Patent Claim 4 and Patent Claim 10 at a modification for a steam generator according to Patent Claim 5. The invention and its advantages will be explained ,m more detail with reference to the accompanying drawings : Figures 1 to 3 show diagrammatically a combined-cycle plant of an electrical power station. In these three figures, identical parts are given the same reference symbols. The plant according to Figure 1 has a waste-heat steam generator with an elongate gas flue 2. This gas flue 2 has an inflow end 3 and an outflow end 4. Three evaporator heating surfaces 9, 5 and 8 can be seen within this gas flue 2. These evaporator heating surfaces 9, 5 and 8 are arranged in the gas flue 2 one behind the other, as seen in the throughflow direction for hot gas from the inflow end 3 to the outflow end 4. The evaporator heating surface 8 is nearest to the outflow end 4 of the gas flue and the evaporator heating surface 9 to the inflow end 3. The evaporator heating surface 5 is located between the two evaporator heating surfaces 8 and 9. The evaporator heating surface 8 is connected both at its inlet 8a and at its outlet 8b to a low-pressure drum 7. A supply line 6 for feed water leads to this low-pressure drum 7. Furthermore, a low-pressure steam line 41 leads off from this low-pressure drum 7. The said line contains a superheater heating surface 2 6 which is arranged between the two evaporator heating surfaces 5 and 8 in the gas flue 2. Each of the two evaporator heating surfaces 5 and 9 is assigned a start-up bottle 27, 28, into which - 5 - a steam line 29, 30 leading off from the evaporator heating surface 5, 9 opens laterally. A return line 31a, 32a guided to the respective inlet of the evaporator heating surface 5, 9 and containing a water pump 31, 32 leads off from the bottom of each of the two start-up bottles 27 and 28. By means of this return line, condensate water separated in the respective start-up bottle 27, 2 8 can be pumped back to the inlet of the respective evaporator heating surface 5, 9. A high-pressure steam line 33, which leads off from the start-up bottle 28 assigned to the evaporator heating surface 9, contains a superheater heating surface 34 which is located in the gas flue 2 of the waste-heat steam generator between the evaporator heating surface 9 and the inflow end 3 of the gas flue 2. A further steam line 35 leads off, on the one hand, from the start-up bottle 27 which is assigned to the evaporator heating surface 5. The said line contains a superheater heating surface 35a which is arranged in the gas flue 2 between the two evaporator heating surfaces 5 and 9. On the other hand, this steam line 35 also leads off from the steam outflow 36b of the high-pressure part of a steam turbine 36, to the steam inflow 36a of which high-pressure part the high-pressure steam line 33 leading off from the start-up bottle 28 is guided. The steam line 35 contains a superheater heating surface 38 which, in terms of throughflow, follows both the superheater heating surface 35a and the steam outflow 3 6b and which is located within the gas flue 2 likewise between the inflow end 3 of this gas flue 2 and the evaporator heating surface 9. Leading off from the superheater heating surface 38, the steam line 35 is guided to the steam inflow 36c of the medium-pressure part of the steam turbine 36. The steam outflow 36d of this medium-pressure part of the steam turbine 37 is th rough flow -connected, via a steam line 40, to the steam inflow 36e of the two low-pressure parts of the steam turbine 36. - 6 - A low-pressure steam line 41 also leads to this steam inflow 3 6e, the said line leading off from the low-pressure drum 7 and containing a superheater heating surface 26. This superheater heating surface 26 is arranged in the gas flue 2 between the two evaporator heating surfaces 5 and 8. An exhaust-steam line 42 leads off from two steam outflows 36f and 3 6g of the low-pressure part of the steam turbine 36 and is guided to a condenser 11. A supply line 10 for feed water, which contains a condensate pump 43, with an associated condensate purification system, as well as a preheating heating surface 12a located in the gas flue 2 and a high-pressure/medium-pressure feed-water pump 44 following this preheating heating surface 12a, leads from this condenser 11 to the inlet sides of the evaporator heating surfaces 5 and 9 located in the gas flue 2. The preheating heating surface 12a is arranged in the gas flue 2 between the outflow end 4 of the gas flue 2 and the evaporator heating surface 8. The inlet sides of the evaporator heating surfaces 5 and 9 are preceded in terms of throughflow in each case by a preheating heating surface 12b, 12c for feed water in the supply line 10 for feed water. These preheating heating surfaces 12b and 12c are arranged in the gas flue 2 between the evaporator heating surface 8 and the evaporator heating surface 5, 9. Connected in parallel with the preheating heating surface 12a is a circulating pump 12d which can pump the feed water from the outlet of this preheating heating surface 12a back to its inlet in order to raise the temperature of the feed water entering the preheating heating surface 12a. The supply line 6 for feed water leads to the low-pressure drum 7 and is throughflow-connected to the supply line 10 for feed water downstream of the preheating surface 12a and downstream of the circulating pump 12d, but upstream of the high-pressure /medium-pressure feed-water pump 44. A treatment point 4 6, which, for example, is a connection - 7 - piece, is located on this supply line 6, in terms of throughflow downstream of the point of connection of this supply line 6 to the supply line 10 for feed water. Another treatment point 47, which, for example, is likewise a connection piece, is located outside the gas flue 2 on the supply line 10 between the condensate pump 43 and the preheating heating surface 12a and upstream of the circulating pump 12d. A line 63 for hot gas, which emerges from a gas turbine 64, leads to the inflow end 3 of the gas flue 2. The inflow of this gas turbine 64 is assigned a combustion chamber 65 having a preceding compressor 66 driven by the gas turbine 64. Both the gas turbine 64 and the steam turbine 37 in each case drive an electrical generator G. At the treatment point 47, by the addition of NH3 and O2 the feed water can be conditioned according to the regulations which apply to the evaporator heating surfaces 5 and 9. By deaerating the feed water, that is to say removing O2, and by the further addition of NH3 at the treatment point 4 6, the feed water supplied to the low-pressure drum 7 is reconditioned in such a way that it conforms to the regulations for the evaporator heating surface 8. The exhaust steam leaving the steam turbine 37 through the exhaust-steam line 42 is precipitated in the condenser 11 as deaerated condensate which is purified in the condensate purification system 43. At the treatment point 47, a pH value of about 8.5 and an O2 content of about 50 to 100 ppb are set for the feed water. In a heated deaeration vessel which belongs to the low-pressure drum 7 and is assigned to the treatment point 46, the O2 content of the feed water supplied to the low-pressure drum 7 is reduced to approximately 2 0 ppb. Moreover, at the treatment point 46, NH3 is also administered to the feed water to be supplied to the low-pressure drum 7, so that the pH value of the feed water is finally raised to 9 to 9.5. - 8 - The combined-cycle plant according to Figure 2 differs from the plant according to Figure 1 only in that, in addition to the two treatment points 46 and 47 for adding and/or removing chemicals for water treatment, a third such treatment point 48 is also present. This is, for example, likewise a connection piece and is located in the first supply line 10 for feed water, in terms of flow downstream of the connection point of the second supply line 6 and upstream of the high-pressure/medium-pressure feed-water pump 44 and therefore upstream of the evaporator heating surfaces 5 and 9. By adding NH3 to the feed water at the treatment point 47 in Figure 2, this feed water can be preconditioned. At the treatment point 46, the feed water is reconditioned by the further addition of NH3, so that it conforms to the regulations for the evaporator heating surface 8. At the treatment point 48, the feed water is reconditioned by the addition of O2, in such a way that it conforms to the regulations for the evaporator heating surfaces 5 and 9. It is not necessary to remove chemicals at any of points 4 6 to 48, nor is any deaeration required. The combined-cycle plant according to Figure 3 differs from the plant according to Figure 1 only in that the second supply line 6 contains a second preheating heating surface 13 arranged within the gas flue 2 and is throughflow-connected, at a connection point upstream of the first preheating heating surface 12a, to the first supply line 10 between the first treatment point 47 and the condensate pump 4 3. The second treatment point 46 is provided on the second supply line 6 upstream of the second preheating heating surface 13 m terms of throughflow. The feed water coming from the condensate pump 4 3 can be conditioned accurately according to the regulations for the evaporator heating surfaces 5 and 9 by adding NH3 and O2 at the first treatment point 47 and accurately - 9 - according to the regulations for the evaporator heating surface 8 by adding NH3 at the treatment point 46. In parallel with the preheating heating surface 13, but downstream of the point of connection of the second supply line 6 to the first supply line 10 in terms of throughflow, there is also a circulating pump 13b which can pump feed water from the outlet of the preheating heating surface 13 back to the inlet of the latter, so that the temperature of the feed, water entering this preheating heating surface is raised. In the plants according to Figures 1 to 3, the condenser 11, together with the condensate pump 43, is the common feed-water supply arrangement, from which originates the initial feed water of uniform initial quality, which finally, differently conditioned, flows to the evaporator heating surfaces 5 and 9, on the one hand, and to the evaporator heating surface 8, on the other hand. - 10 - WE CLAIM : 1. A Steam generator, in particular waste-heat steam generator, with an elongate gas flue (2), which has an inflow end (3) for hot gas and an outflow end (4) for the cooled hot gas, and with a first evaporator heating surface (5, 9), to which a first supply line (10) for feed water is throughflow-connected on the inlet side and which, as seen in the throughflow direction of the hot gas, is located in the gas flue (2) upstream of a second evaporator heating surface (8) which is throughflow-connected both on the inlet and on the outlet side to a low-pressure drum (7) provided with a second supply line (6) for feed water, characterized in that the first supply line (10) has a first treatment point (47) for adding and/or extracting chemicals for water treatment and the second supply line (6) has a second treatment point (4 6) for adding and/or extracting chemicals for water treatment. 2. The Steam generator as claimed in Claim 1, wherein the first supply line (10) contains a preheating heating surface (12a) which is arranged within the gas flue (2) , and in that the second supply line (6) is throughflow-connected to the first supply line (10) at a connection point between the preheating heating surface (12a) and the evaporator heating surface (5, 9). 3. The Steam generator as claimed in wherein the first supply line (10) has, upstream of the preheating heating surface (12a) in terms of throughflow, the first treatment point (47) for adding and/or extracting chemicals for water treatment, and in that the second supply line (6) has, downstream of its point of connection to the first supply line (10) in terms of throughflow, the second treatment point (46) for adding and/or extracting chemicals for water treatment. 4 . wherein steam generator as claimed in Claim 3, the first supply line (10) has, -11- downstream of the connection point of the second supply 1ine (6) and upstream of the evaporator heating surface (5,9) in terms of throughflow, a third treatment point (48) for adding and/or extracting chemicals for feed-water treatment. 5. Steam generator as claimed in claim 1, wherein the first supply line (10) contains a first preheating heating surface (12a) which is arranged within the gas flue (2) in that the second supply line (6) contains a second preheating heating surface, (13) arranged within the gas flue (2) and is throughflow connected to the first supply line (10) at a first connection point upstream of the first preheating heating surface (12a), in that the first supply line (10) has, upstream of the first preheating heating surface (12a) and downstream of the first connection points in terms of throughflow, the first treatment Do in (47) for adding and/or extracting chemicals for water treatment, and in that the second treatment point (46) for adding and/or removing chemicals for water treatment is provided on the second supply line (6) upstream of the second preheating heating surface (13) in terms of throughflow. 6. Stream generator as claimed in one of claims 1 to 4, wherein the second treatment point (46) has a deaeration vessel for extracting a gaseous chemical from the feed water. 7. A method for operating a steam generator as claimed in claim 1 or 2, comprising the steps of: 7. -12- providing an elongate gas flue having an inflow end for hot gas and an outflow end for cooled hot gas; defining a throughflow direction of the hot gas; disposing a first evaporator heating surface in the gas flue, the first evaporator having an inlet side; connecting a first feed water supply line throughflow-to the first evaporator heating surface on the inlet side, the first supply line having a first treatment point for at least one of adding and extracting chemicals for water treatment, and the first supply line having a preheater heating surface disposed within the gas flue and defining a connection point between the preheater heating surface and the first evaporator heating surface; disposing a second evaporator heating surface in the gas flue downstream of the first evaporator heating surface as seen in the throughflow direction of the hot gas, the second evaporator heating surface having inlet and outlet sides; throughflow connecting a low-pressure drum to the second evaporator heating surface on both the inlet and outlet sides; and connecting a second feed water supply line to the low-pressure drum, the second feed water supply line having a second treatment point for at least one of adding and extracting chemicals for water treatment; -13- throughflow connecting the second supply line to the first supply line at the connection point| disposing the first treatment point for at leasts one of adding and extracting chemicals for water treatment is upstream of the preheater heating surface in terms of throughflow in the first supply line; disposing the second treatment point for at least one of adding and extracting chemicals for water treatment downstream of the connection point to the first supply line in terms of throughflow in the second supply line; adding NH3 and 02 at the first treatment point; and adding NH3 and extracting 02 at the second treatment point. 8. Method for operating a steam generator as claimed in claim 3 wherein NH3 and 02 are added at the first treatment point (47) and NH3 is added and 02 extracted at the second treatment point (46). 9. Method for operating a steam generator as claimed in claim 4 wherein NH3 is added at the first (47) and the second (46 treatment point and 02 is added at the third treatment point (48). -14- 10. Method for operating a steam generator as claimed in claim 5, wherein NH3 and O2 are added at the first treat- ment point (47) and NH3 is added at the second treatment point (46) . (B.B.SEN) of L. S, DAVAR & CO sApplicants' Agent Dated this 19th day of AUGUST, 1998 Steam generator, in particular waste-heat steam generator, and method for operating this steam generator A first (5, 9) and a second (8) evaporator heating surface are located in an elongate gas flue (2) for hot gas of a steam generator. A first supply line (10) for feed water is throughflow-connected on the inlet side to the first evaporator heating surface (5, 9), whilst the second evaporator heating surface (8) is throughflow-connected on the inlet and the outlet side to a low-pressure drum (7) . The low-pressure drum (7) is provided with a second supply line (6) for feed water. The first supply line (10) has a first treatment point (47) and the second supply line (6) a second treatment point (46); each of the two treatment points serves for adding and/or extracting chemicals for water treatment, so that each evaporator heating surface (5, 9, 8) can receive only feed water which is conditioned according to the regulations applying to the said evaporator heating surface.

Documents:

01477-cal-1998-abstract.pdf

01477-cal-1998-claims.pdf

01477-cal-1998-correspondence.pdf

01477-cal-1998-description(complete).pdf

01477-cal-1998-drawings.pdf

01477-cal-1998-form-1.pdf

01477-cal-1998-form-2.pdf

01477-cal-1998-form-3.pdf

01477-cal-1998-form-5.pdf

01477-cal-1998-gpa.pdf

01477-cal-1998-priority document other.pdf

01477-cal-1998-priority document.pdf

1477-CAL-1998-(12-10-2012)-FORM-27.pdf

1477-CAL-1998-FORM-27.pdf

1477-cal-1998-granted-abstract.pdf

1477-cal-1998-granted-claims.pdf

1477-cal-1998-granted-correspondence.pdf

1477-cal-1998-granted-description (complete).pdf

1477-cal-1998-granted-drawings.pdf

1477-cal-1998-granted-examination report.pdf

1477-cal-1998-granted-form 1.pdf

1477-cal-1998-granted-form 2.pdf

1477-cal-1998-granted-form 3.pdf

1477-cal-1998-granted-form 5.pdf

1477-cal-1998-granted-gpa.pdf

1477-cal-1998-granted-letter patent.pdf

1477-cal-1998-granted-priority document.pdf

1477-cal-1998-granted-reply to examination report.pdf

1477-cal-1998-granted-specification.pdf

1477-cal-1998-granted-translated copy of priority document.pdf

1477-CAL-1998-OTHER PATENT DOCUMENT.pdf