EP0719378A1 - Process for improving efficiency in thermal power stations with series-connected condensers on the cooling water side - Google Patents

Process for improving efficiency in thermal power stations with series-connected condensers on the cooling water side

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Publication number
EP0719378A1
EP0719378A1 EP95925677A EP95925677A EP0719378A1 EP 0719378 A1 EP0719378 A1 EP 0719378A1 EP 95925677 A EP95925677 A EP 95925677A EP 95925677 A EP95925677 A EP 95925677A EP 0719378 A1 EP0719378 A1 EP 0719378A1
Authority
EP
European Patent Office
Prior art keywords
cooling water
condenser
flow
condensers
partial
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
EP95925677A
Other languages
German (de)
French (fr)
Other versions
EP0719378B1 (en
Inventor
Uwe JOHÄNNTGEN
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Steag Power Saar GmbH
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Saarbergwerke AG
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Filing date
Publication date
Application filed by Saarbergwerke AG filed Critical Saarbergwerke AG
Publication of EP0719378A1 publication Critical patent/EP0719378A1/en
Application granted granted Critical
Publication of EP0719378B1 publication Critical patent/EP0719378B1/en
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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K9/00—Plants characterised by condensers arranged or modified to co-operate with the engines
    • F01K9/003—Plants characterised by condensers arranged or modified to co-operate with the engines condenser cooling circuits

Definitions

  • the invention relates to a method for improving the efficiency in thermal power plants with condensers connected in series on the cooling water side.
  • the possibility is used to connect the condensers downstream of the LP turbines or LP subturbines in series on the cooling water side in order to increase the efficiency, all condensers one after the other from the whole Flow of cooling water.
  • the cooling water cooled down by the cooling process in the cooling tower flows through the condensers one after the other, absorbs heat and is subsequently removed from this part of the system and fed back to the cooling tower as hot water for recooling.
  • the exhaust steam condenses at a pressure which depends in particular on the respective cooling water outlet temperature of the condenser in question.
  • a disadvantage of the series connection is that at low cooling water inlet temperatures, due to the reduced cooling water outlet temperatures, further reduced evaporation pressures occur in the individual condensers. They lead to higher degradable pressure drops, correspondingly to higher flow velocities of the steam and thus to increasing outlet losses, which reduce the increase in efficiency. If the pressure ratios approach the critical pressure ratio when the cooling water inlet temperature decreases, the flow velocity roughly reaches the speed of sound and the so-called blocking of the flow profile occurs. Any further increase in the pressure drop beyond the critical pressure drop, caused by a further reduction in the cooling water inlet temperature, no longer has an effect on increasing the speed of the steam.
  • the invention is based on the object of preventing the disadvantage of losses in efficiency which arises when the cooling water inlet temperatures are too low in a system of the type described at the outset.
  • the object is achieved in that, when the cooling water flow falls below a predetermined limit temperature, the cooling water flow is divided before entry into the first condenser, so that only part of the cooling water flow flows through the condenser, while the remaining partial flow flows through a condenser Bypass bypasses the condenser, and that both partial flows are brought together again immediately behind the condenser, before entering the following condenser.
  • the partial flow diverted via the bypass is set or regulated particularly economically, for example, with the aid of a control device depending on the cooling water outlet temperature of the bypassed condenser.
  • the advantage of the method is based in particular on the fact that the bypass circuit prevents the flow profile in the turbine or sub-turbine assigned to the bypassed condenser from being blocked, without having any appreciable influence on the cooling water outlet temperatures of the condensers, which are subsequently flowed through by the partial streams which are again combined to form a total cooling water stream.
  • the expansion ratios in each condenser not bypassed by a bypass partial flow and thus in the turbines or partial turbines assigned to them are not deteriorated according to the invention.
  • a general reduction of the cooling water flow for all condensers connected in series or a warming up of the cooling water before entering the first condenser has- te an increase in the evaporation pressure in the first condenser, but also in all subsequent condensers.
  • the blocking effect in the turbine or partial turbine assigned to the first condenser would be prevented, but at the same time the conditions in all the following condensers would also have deteriorated.
  • a further advantage of the method according to the invention results from the temporary expansion of the flow cross section in the bypass mode of operation, which leads to a noticeable reduction in throttle losses.
  • the possibility is also provided of bypassing the second and possibly further capacitors with a bypass partial stream, the bypass partial stream being immediately separated from the total by the condenser to be bypassed. Cooling water flow is branched off and the partial flows are brought together again behind the condenser. It is thereby achieved that at a very low temperature of the cooling water supplied by the cooling tower and a possibly inadequate temperature increase due to the heat absorption in the first condenser, the flow profile in the turbine or partial turbine assigned to the subsequent condenser is not blocked is coming.
  • a bypass sequence extending over several condensers ensures for each individual bypassed condenser that the flow profile in the turbine or sub-turbine assigned to it is not blocked without worsening the expansion conditions in the condensers still to be flowed through.
  • the method according to the invention is further explained on the basis of the exemplary embodiments shown schematically in FIGS. 1 to 3.
  • the two partial condensers 1 a and 1 b which are assigned to the two low-pressure sub-turbines 2a and 2b, are connected in series on the cooling water side in order to increase the efficiency.
  • the cooling water is conveyed from the cooling tower cup via the cooling water pump 3 and the cooling water line 4 into the first partial condenser 1 a, via the overflow line 5 the cooling water, which has already been partially warmed up, reaches the second partial condenser 1 b and is returned via line 6 as hot water to the cooling tower .
  • the exhaust steam which is introduced via line 7 from the low-pressure turbine section 2b into the partial condenser 1b, condenses at a pressure which is particularly dependent on the water temperature in line 6.
  • the exhaust steam which is introduced via line 8 from the LP sub-turbine 2a into the partial condenser 1a, condenses at a pressure which is dependent in particular on the water temperature in line 5. Since the temperature in line 5 is lower than in line 6, the evaporation pressure in line 8 is at a lower level than in line 7.
  • the partial turbine 2a therefore has a greater pressure drop than when the partial condensers la and lb are connected in parallel on the cooling water side would be the case. An improvement in efficiency results from this.
  • the condensate formed from the exhaust steam passes via line 9 from the partial condenser 1b into line 10 and via the condensate pump 11 to the low-pressure preheaters and thus into the water-steam circuit of the power plant.
  • a reduction in the cooling water inlet temperature results in a reduction in the evaporation pressure, as a result of which the flow rate of the steam and thus also the outlet losses increase. Nevertheless, an efficiency advantage remains as long as the flow profile is not blocked. It is only when the cooling water inlet temperature drops to a level that causes critical or subcritical conditions that the effect of blocking the flow profile first occurs in the partial turbine 2a. Because of the resulting low condensate temperature, additional tap steam is required for preheating the feed water, which reduces the overall efficiency.
  • a reduction in the cooling water flow for example by adjusting the moving blade on the cooling water pump 3, would have an increase in the evaporation pressure in the partial condenser la and thus prevent the blocking effect, but at the same time the conditions on the partial condenser lb would also deteriorate.
  • the blocking of the flow profile due to excessively low inlet temperature of the cooling water is prevented by passing a partial flow of the cooling water flow past the first partial condenser 1 a through a bypass line 12, the bypass Partial current can be set or regulated by a control valve 13.
  • the cooling water outlet temperature in line 5a increases behind the partial condenser 1 a.
  • the blocking of the flow profile in sub-turbine 2a can be prevented even if the cooling water inlet temperatures in line 4 are too low.
  • the advantageous effect of an improvement in efficiency due to the series connection of the condensers la and lb on the cooling water side is retained, however, since the drop in efficiency due to excessively low cooling water temperature is prevented, but the contribution to efficiency of the partial condenser 1b is due to the almost uninfluenced expansion in the Sub-turbine 2b is not deteriorated. As shown in FIG.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Engine Equipment That Uses Special Cycles (AREA)
  • Greenhouses (AREA)
  • Electric Double-Layer Capacitors Or The Like (AREA)
  • Discharge Heating (AREA)

Abstract

In a process in thermal power stations in which condensers (1a, 1b) are connected in series on the cooling water side to improve efficiency, it is proposed that, with excessively low cooling water inlet temperatures, when the improved efficiency is lost through sub-critical pressure ratios, part of the flow of cooling water adjustable, e.g. using a regulating device (13), be diverted before entering the first condenser (1a) via a by-pass line (12), by-pass said condenser (12) and be remixed with the partial cooling water flow before entering the condenser (1b) through which it has yet to pass. The process of the invention can also be extended to other condensers in order to ensure that there is no obstruction in the flow profile in the allocated turbines or partial turbines owing to the pressure ratios arising in the by-passed and subsequent condensers. The advantage of the improved efficiency is thus retained even with excessively low cooling water inlet temperatures and the pressure ratios in the un-by-passed condensers remain virtually unaffected. The ratio between by-pass partial flow and cooling water partial flow is adequately adjusted or controlled depending on the actual cooling water outlet temperature.

Description

Verfahren zur Wirkungsgradverbesserung in Wärmekraftwerken mit kuhlwasserseitig in Reihe geschalteten KondensatorenProcess for improving efficiency in thermal power plants with condensers connected in series on the cooling water side
Die Erfindung betrifft ein Verfahren zur Wirkungsgradver¬ besserung in Wärmekraftwerken mit kuhlwasserseitig in Reihe geschalteten Kondensatoren.The invention relates to a method for improving the efficiency in thermal power plants with condensers connected in series on the cooling water side.
Bei Wärmekraftwerken, insbesondere solchen mit Rückkühlung des Kühlwassers über den Kühlturm, wird die Möglichkeit ge¬ nutzt, zur Wirkungsgradsteigerung die den ND-Turbinen bzw. ND-Teilturbinen nachgeschalteten Kondensatoren kuhlwasser¬ seitig in Reihe zu schalten, wobei alle Kondensatoren nach¬ einander vom gesamten Kühlwasserstrom durchflössen werden. Das durch den Kühlprozeß im Kühlturm heruntergekühlte Kühl¬ wasser durchströmt dabei nacheinander die Kondensatoren, nimmt Wärme auf und wird anschließend aus diesem Anlagen¬ teil abgeführt und dem Kühlturm als Warmwasser zur erneuten Rückkühlung wieder zugeleitet. In den in Reihe geschalteten Kondensatoren kondensiert der Abdampf dabei bei einem Druck, der insbesondere von der jeweiligen Kühlwasseraus¬ trittstemperatur des betreffenden Kondensators abhängt. In Flußrichtung des Kühlwasserstromes steigen die Kühlwasser¬ austrittstemperaturen an den einzelnen Kondensatoren zwangsläufig an. Das dem Abdampf zur Verfügung stehende Druckgefälle, das als Enthalpiedifferenz zur Steigerung der Strömungsgeschwindigkeit in Geschwindigkeitsenergie umge¬ setzt wird, wird - wegen der erhöhten Wärmeabfuhr infolge des größeren KühlwasserStromes - bei den zuerst durchström¬ ten Kondensatoren größer, als es bei kühlwasserseitiger Parallelschaltung der Kondensatoren der Fall wäre. Dies be¬ wirkt einen besseren Gesamtwirkungsgrad, da die auf der wärmeren Seite des Kühlwassers gelegenen Kondensatoren den¬ noch mit Druckgefällen arbeiten, die in etwa denen der Pa¬ rallelschaltung entsprechen.In the case of thermal power plants, in particular those with recooling of the cooling water via the cooling tower, the possibility is used to connect the condensers downstream of the LP turbines or LP subturbines in series on the cooling water side in order to increase the efficiency, all condensers one after the other from the whole Flow of cooling water. The cooling water cooled down by the cooling process in the cooling tower flows through the condensers one after the other, absorbs heat and is subsequently removed from this part of the system and fed back to the cooling tower as hot water for recooling. In the condensers connected in series, the exhaust steam condenses at a pressure which depends in particular on the respective cooling water outlet temperature of the condenser in question. In the flow direction of the cooling water flow, the cooling water outlet temperatures at the individual condensers inevitably rise. The pressure drop available to the exhaust steam, which is converted into enthalpy difference to increase the flow velocity into velocity energy, becomes greater - due to the increased heat dissipation due to the greater cooling water flow - in the condensers through which flow first than when the condensers of the condenser are connected in parallel on the cooling water side Would be the case. This results in a better overall efficiency, since that on the condensers located on the warmer side of the cooling water still work with pressure drops which correspond approximately to those of the parallel connection.
Nachteilig erweist sich jedoch bei der Reihenschaltung, daß sich bei tiefen Kühlwassereintrittstemperaturen, bedingt durch die damit auch verringerten Kühlwasseraustrittstempe¬ raturen, in den einzelnen Kondensatoren weiter verminderte Abdampfdrücke einstellen. Sie führen zu höheren abbaubaren Druckgefällen, dementsprechend zu höheren Strömungsge¬ schwindigkeiten des Dampfes und damit zu ansteigenden Aus¬ laßverlusten, die den Wirkungsgradzuwachs verringern. Nähern sich bei abnehmender Kühlwassereintrittstemperatur die Druckverhältnisse dem kritischen Druckverhältnis, so erreicht die Strömungsgeschwindigkeit in etwa Schallge¬ schwindigkeit und es tritt das sogenannte Sperren des Strö¬ mungsprofiles ein. Jede weitere Vergrößerung des Druckge¬ fälles über das kritische Druckgefälle hinaus, hervorgeru¬ fen durch eine weitere Absenkung der Kühlwassereintritts¬ temperatur, wirkt sich nicht mehr als Geschwindigkeitsstei¬ gerung beim Dampf aus.However, a disadvantage of the series connection is that at low cooling water inlet temperatures, due to the reduced cooling water outlet temperatures, further reduced evaporation pressures occur in the individual condensers. They lead to higher degradable pressure drops, correspondingly to higher flow velocities of the steam and thus to increasing outlet losses, which reduce the increase in efficiency. If the pressure ratios approach the critical pressure ratio when the cooling water inlet temperature decreases, the flow velocity roughly reaches the speed of sound and the so-called blocking of the flow profile occurs. Any further increase in the pressure drop beyond the critical pressure drop, caused by a further reduction in the cooling water inlet temperature, no longer has an effect on increasing the speed of the steam.
Eine Wirkungsgradsteigerung, zurückzuführen auf den Abbau vergrößerter Enthalpiedifferenzen, kommt so nicht mehr zu¬ stande und aufgrund der niedrigen Kondensattemperaturen wird sogar eine intensivere Beheizung der Speisewasservor- wärmung mit Anzapf ampf erforderlich. Die Folge ist eine Verschlechterung des Gesamtwirkungsgrades ursächlich einge¬ leitet durch zu tiefe - d.h. unterkritische Verhältnisse schaffende - Kühlwassereintrittstemperaturen. Da bei Reihenschaltung der Kondensatoren und gleichem Gesamt-Kühlwasserstro das Sperren des Strömungsprofiles , wegen des bezogen auf den einzelnen Kondensator erhöhten Kühlwasserdurchflusses, bereits bei höheren Kühlwasserein¬ trittstemperaturen eintritt als bei Parallelschaltung der Kondensatoren, kann bei zu tiefen Kühlwassereintrittstempe¬ raturen der Vorteil der Reihenschaltung nicht mehr voll er¬ halten werden.An increase in efficiency, due to the reduction of larger enthalpy differences, no longer occurs and, due to the low condensate temperatures, even more intensive heating of the feed water preheating with a tap is necessary. The result is a deterioration in the overall efficiency, which is initially caused by cooling water inlet temperatures which are too low, ie which create subcritical conditions. Since, when the condensers are connected in series and the total cooling water flow is the same, the blocking of the flow profile, due to the increased cooling water flow rate in relation to the individual condenser, already occurs at higher cooling water inlet temperatures than when the cooling water is connected in parallel Capacitors, the advantage of the series connection can no longer be fully maintained if the cooling water inlet temperatures are too low.
Der Erfindung liegt die Aufgabe zugrunde, bei einer Anlage der eingangs beschriebenen Art den bei zu tiefen Kühlwas¬ sereintrittstemperaturen sich einstellenden Nachteil der Wirkungsgradeinbuβe zu verhindern.The invention is based on the object of preventing the disadvantage of losses in efficiency which arises when the cooling water inlet temperatures are too low in a system of the type described at the outset.
Die Aufgabe wird erfindungsgemäß dadurch gelöst, daß bei Unterschreiten einer vorgegebenen Grenztemperatur des Kühl¬ wassers der Kühlwasserstrom vor Eintritt in den ersten Kon¬ densator geteilt wird, so daß nur ein Teil des Kühlwasser¬ stromes den Kondensator durchströmt während der verbleiben¬ de Teilstrom über einen Bypass den Kondensator umfährt, und daß beide Teilströme unmittelbar hinter dem Kondensator, vor Eintritt in den folgenden Kondensator, wieder zusammen¬ geführt werden.The object is achieved in that, when the cooling water flow falls below a predetermined limit temperature, the cooling water flow is divided before entry into the first condenser, so that only part of the cooling water flow flows through the condenser, while the remaining partial flow flows through a condenser Bypass bypasses the condenser, and that both partial flows are brought together again immediately behind the condenser, before entering the following condenser.
Der über den Bypass umgeleitete Teilstrom wird dabei z.B. besonders wirtschaftlich mit Hilfe einer Regeleinrichtung in Abhängigkeit der Kühlwasseraustrittstemperatur des um¬ fahrenen Kondensators eingestellt bzw. geregelt. Der Vorteil des Verfahrens beruht insbesondere darauf, daß durch die Bypass-Schaltung das Sperren des Strömungsprofi¬ les in der dem umfahrenen Kondensator zugeordneten Turbine bzw. Teilturbine verhindert wird, und zwar ohne nennens¬ werten Einfluß zu nehmen auf die Kühlwasseraustrittstempe¬ raturen der Kondensatoren, die nachfolgend von den wieder zu einem Gesamt-Kühlwasserstrom zusammengeführten Teilströ¬ men durchströmt werden. Die Expansionsverhältnisse in jedem nicht von einem Bypass-Teilstrom umfahrenen Kondensator und damit in den ihnen zugeordneten Turbinen bzw. Teilturbinen werden dabei erfindungsge äβ nicht verschlechtert. Eine generelle Verringerung des Kühlwasserstromes für alle in Reihe geschalteten Kondensatoren oder eine Aufwärmung des Kühlwassers vor Eintritt in den ersten Kondensator hat- te eine Erhöhung des Abdampfdruckes im ersten Kondensator, aber auch in allen folgenden Kondensatoren zur Folge. Die Sperrwirkung in der dem ersten Kondensator zugeordneten Turbine bzw. Teilturbine wäre zwar verhindert, gleichzeitig hätten sich aber auch die Verhältnisse in allen nachfolgen¬ den Kondensatoren verschlechtert.The partial flow diverted via the bypass is set or regulated particularly economically, for example, with the aid of a control device depending on the cooling water outlet temperature of the bypassed condenser. The advantage of the method is based in particular on the fact that the bypass circuit prevents the flow profile in the turbine or sub-turbine assigned to the bypassed condenser from being blocked, without having any appreciable influence on the cooling water outlet temperatures of the condensers, which are subsequently flowed through by the partial streams which are again combined to form a total cooling water stream. The expansion ratios in each condenser not bypassed by a bypass partial flow and thus in the turbines or partial turbines assigned to them are not deteriorated according to the invention. A general reduction of the cooling water flow for all condensers connected in series or a warming up of the cooling water before entering the first condenser has- te an increase in the evaporation pressure in the first condenser, but also in all subsequent condensers. The blocking effect in the turbine or partial turbine assigned to the first condenser would be prevented, but at the same time the conditions in all the following condensers would also have deteriorated.
Ein weiterer Vorteil des erfindungsgemäßen Verfahrens er¬ gibt sich durch die vorübergehende Erweiterung des Strö¬ mungsquerschnittes bei Bypass-Fahrweise, die zu einer merk¬ lichen Verringerung der Drosselverluste führt.A further advantage of the method according to the invention results from the temporary expansion of the flow cross section in the bypass mode of operation, which leads to a noticeable reduction in throttle losses.
Gemäß einer weiteren Ausgestaltung des erfindungsgemäßen Verfahrens ist bei einer Reihenschaltung von mehr als zwei Kondensatoren die Möglichkeit vorgesehen, auch den zweiten und gegebenenfalls weitere Kondensatoren mit einem Bypass- Teilstrom zu umfahren, wobei der Bypass-Teilstrom jeweils unmittelbar vor dem zu umfahrenden Kondensator vom Gesamt- Kühlwasserstrom abgezweigt wird und die Teilströme hinter dem Kondensator wieder zusammengeführt werden. Dadurch wird erreicht, daß bei sehr niedriger Temperatur des vom Kühl¬ turm zugeführten Kühlwassers und einer möglicherweise nicht ausreichenden Temperaturerhöhung durch die Wärmeaufnahme im ersten Kondensator , es nicht zu einem Sperren des Strö¬ mungsprofiles in der dem nachfolgenden Kondensator zugeord¬ neten Turbine bzw. Teilturbine kommt.According to a further embodiment of the method according to the invention, if more than two capacitors are connected in series, the possibility is also provided of bypassing the second and possibly further capacitors with a bypass partial stream, the bypass partial stream being immediately separated from the total by the condenser to be bypassed. Cooling water flow is branched off and the partial flows are brought together again behind the condenser. It is thereby achieved that at a very low temperature of the cooling water supplied by the cooling tower and a possibly inadequate temperature increase due to the heat absorption in the first condenser, the flow profile in the turbine or partial turbine assigned to the subsequent condenser is not blocked is coming.
Ein über mehrere Kondensatoren sich erstreckende Bypass- Folge, wobei für jeden umfahrenen Kondensator das Verhält¬ nis von Bypass-Teilstrom zu Kühlwasser-Teilstrom in Abhän¬ gigkeit der Kühlwasseraustrittstemperatur des jeweiligen Kondensators bestimmt ist, stellt für jeden einzelnen um¬ fahrenen Kondensator sicher, daß ein Sperren des Strömungs¬ profiles in der ihm zugeordneten Turbine bzw. Teilturbine unterbleibt, ohne die Expansionsverhältnisse in den noch zu durchströmenden Kondensatoren zu verschlechtern. Das erfindungsgemäße Verfahren wird anhand der in den Figu¬ ren 1 bis 3 schematisch dargestellten Ausführungsbeispiele weiter erläutert.A bypass sequence extending over several condensers, the ratio of bypass partial flow to cooling water partial flow being determined as a function of the cooling water outlet temperature of the respective condenser for each bypassed condenser, ensures for each individual bypassed condenser that the flow profile in the turbine or sub-turbine assigned to it is not blocked without worsening the expansion conditions in the condensers still to be flowed through. The method according to the invention is further explained on the basis of the exemplary embodiments shown schematically in FIGS. 1 to 3.
Gemäß der bekannten Schaltung nach Figur 1 sind zur Wir¬ kungsgradsteigerung die beiden Teilkondensatoren la und lb, die den beiden ND-Teilturbinen 2a und 2b zugeordnet sind, kuhlwasserseitig in Reihe geschaltet. Das Kühlwasser wird dabei aus der Kühlturmtasse über die Kühlwasserpumpe 3 und die Kühlwasserleitung 4 in den ersten Teilkondensator la gefördert, über die Überströmleitung 5 gelangt das bereits teilweise aufgewärmte Kühlwasser in den zweiten Teilkonden¬ sator lb und wird über die Leitung 6 als Warmwasser zum Kühlturm zurückgeführt. Der Abdampf, der über die Leitung 7 aus der ND-Teilturbine 2b in den Teilkondensator lb ein¬ gleitet wird, kondensiert bei einem Druck, der insbesondere von der Wassertemperatur in Leitung 6 abhängig ist. Der Ab¬ dampf, der über die Leitung 8 aus der ND-Teilturbine 2a in den Teilkondensator la eingeleitet wird, kondensiert bei einem Druck, der insbesondere von der Wassertemperatur in Leitung 5 abhängig ist. Da die Temperatur in Leitung 5 niedriger ist als in Leitung 6, hat der Abdampfdruck in Leitung 8 ein niedrigeres Niveau als in Leitung 7. Die Teilturbine 2a hat also ein größeres Druckgefälle zur Ver¬ fügung, als es bei kühlwasserseitiger Parallelschaltung der Teilkondensatoren la und lb der Fall wäre. Daraus resul¬ tiert eine Wirkungsgradverbesserung. Das aus dem Abdampf entstandene Kondensat gelangt über die Leitung 9 vom Teil¬ kondensator lb in die Leitung 10 und über die Kondensatpum¬ pe 11 zu den ND-Vorwärmern und damit in den Wasser-Dampf- Kreislauf des Kraftwerkes.According to the known circuit according to FIG. 1, the two partial condensers 1 a and 1 b, which are assigned to the two low-pressure sub-turbines 2a and 2b, are connected in series on the cooling water side in order to increase the efficiency. The cooling water is conveyed from the cooling tower cup via the cooling water pump 3 and the cooling water line 4 into the first partial condenser 1 a, via the overflow line 5 the cooling water, which has already been partially warmed up, reaches the second partial condenser 1 b and is returned via line 6 as hot water to the cooling tower . The exhaust steam, which is introduced via line 7 from the low-pressure turbine section 2b into the partial condenser 1b, condenses at a pressure which is particularly dependent on the water temperature in line 6. The exhaust steam, which is introduced via line 8 from the LP sub-turbine 2a into the partial condenser 1a, condenses at a pressure which is dependent in particular on the water temperature in line 5. Since the temperature in line 5 is lower than in line 6, the evaporation pressure in line 8 is at a lower level than in line 7. The partial turbine 2a therefore has a greater pressure drop than when the partial condensers la and lb are connected in parallel on the cooling water side would be the case. An improvement in efficiency results from this. The condensate formed from the exhaust steam passes via line 9 from the partial condenser 1b into line 10 and via the condensate pump 11 to the low-pressure preheaters and thus into the water-steam circuit of the power plant.
Eine Absenkung der Kühlwassereintrittstemperatur hat eine Reduzierung des Abdampfdruckes zur Folge, wodurch die Strö¬ mungsgeschwindigkeit des Dampfes und damit auch die Ausla߬ verluste ansteigen. Dennoch verbleibt ein Wirkungsgradvor¬ teil, solange kein Sperren des Strömungsprofiles eintritt. Erst bei einem Absinken der Kühlwassereintrittstemperatur auf ein Niveau, das kritische bzw. unterkritische Verhält¬ nisse bewirkt tritt zunächst bei der Teilturbine 2a der Ef¬ fekt des Sperrens des Strömungsprofiles ein. Wegen der sich einstellenden niedrigen Kondensattemperatur wird sogar zu¬ sätzlicher Anzapfdampf für die Speisewasservorwärmung benö¬ tigt, der den Gesamtwirkungsgrad reduziert. Eine Reduktion des Kühlwasserstromes z.B. durch Laufschau- felverstellung an der Kühlwasserpumpe 3 hätte zwar eine Er¬ höhung des Abdampfdruckes im Teilkondensator la und damit das Verhindern der Sperrwirkung zur Folge, gleichzeitig würden dadurch aber auch die Verhältnisse am Teilkondensa¬ tor lb verschlechtert.A reduction in the cooling water inlet temperature results in a reduction in the evaporation pressure, as a result of which the flow rate of the steam and thus also the outlet losses increase. Nevertheless, an efficiency advantage remains as long as the flow profile is not blocked. It is only when the cooling water inlet temperature drops to a level that causes critical or subcritical conditions that the effect of blocking the flow profile first occurs in the partial turbine 2a. Because of the resulting low condensate temperature, additional tap steam is required for preheating the feed water, which reduces the overall efficiency. A reduction in the cooling water flow, for example by adjusting the moving blade on the cooling water pump 3, would have an increase in the evaporation pressure in the partial condenser la and thus prevent the blocking effect, but at the same time the conditions on the partial condenser lb would also deteriorate.
Nach dem in Figur 2 dargestellten erfindungsgemäßen Verfah¬ ren wird das Sperren des Strömungsprofiles infolge zu tie¬ fer Eintrittstemperatur des Kühlwassers verhindert, in dem durch eine Bypass-Leitung 12 ein Teilstrom des Kühlwasser¬ stromes an dem ersten Teilkondensator la vorbeigeleitet wird, wobei der Bypass-Teilstrom durch eine Regelarmatur 13 eingestellt bzw. geregelt werden kann.According to the method according to the invention shown in FIG. 2, the blocking of the flow profile due to excessively low inlet temperature of the cooling water is prevented by passing a partial flow of the cooling water flow past the first partial condenser 1 a through a bypass line 12, the bypass Partial current can be set or regulated by a control valve 13.
Durch den über Leitung 13 abgezweigten Bypass-Teilstrom er¬ höht sich die Kühlwasseraustrittstemperatur in Leitung 5a hinter dem Teilkondensator la. Dadurch kann erfindungsgemäß auch bei zu tiefen Kühlwassereintrittstemperaturen in Lei¬ tung 4 das Sperren des Strömungsprofiles in Teilturbine 2a verhindert werden. Die vorteilhafte Wirkung einer Wirkungs¬ gradverbesserung bedingt durch die kühlwasserseitige Rei¬ henschaltung der Kondensatoren la und lb bleibt jedoch er¬ halten, da der Wirkungsgradabfall infolge zu tiefer Kühl¬ wassertemperatur verhindert wird, der Wirkungsgradbeitrag des Teilkondensators lb jedoch durch die fast unbeeinflußte Expansion in der Teilturbine 2b nicht verschlechtert wird. Wie in Figur 3 gezeigt ist, kann es bei einer Reihenschal¬ tung von mehr als zwei Kondensatoren la, lb, li erforder¬ lich sein, auch vor dem zweiten Teilkondensator lb und ggf . weiteren nachgeschalteten Teilkondensatoren, von dem Gesamt-Kühlwasserstrom einen - eingestellt bzw. geregelt wieder in Abhängigkeit der Kühlwasseraustrittstemperatur des jeweiligen Kondensators - Bypass-Teilstrom abzuzweigen und hinter dem Kondensator wieder dem austretenden Kühlwasser-Teilstrom zuzumischen. Das kann erforderlich sein, wenn die Temperaturerhöhung im Gesamt-Kühlwasserstrom nach dem Durchströmen des ersten Kondensators nicht aus¬ reicht, um ein Sperren des Strömungsprofiles in der dem nachfolgenden Kondensator zugeordneten Teilturbine sicher zu verhindern. As a result of the bypass partial flow branched off via line 13, the cooling water outlet temperature in line 5a increases behind the partial condenser 1 a. As a result, according to the invention, the blocking of the flow profile in sub-turbine 2a can be prevented even if the cooling water inlet temperatures in line 4 are too low. The advantageous effect of an improvement in efficiency due to the series connection of the condensers la and lb on the cooling water side is retained, however, since the drop in efficiency due to excessively low cooling water temperature is prevented, but the contribution to efficiency of the partial condenser 1b is due to the almost uninfluenced expansion in the Sub-turbine 2b is not deteriorated. As shown in FIG. 3, it may be necessary in the case of a series connection of more than two capacitors 1 a, 1 b, 1 1, also in front of the second partial capacitor 1 b and, if necessary. further downstream partial condensers, one branch from the total cooling water flow - adjusted or regulated again depending on the cooling water outlet temperature of the respective condenser - branch bypass partial flow and admixed behind the condenser to the emerging cooling water partial flow. This may be necessary if the temperature increase in the total cooling water flow after flowing through the first condenser is not sufficient to reliably prevent the flow profile in the sub-turbine assigned to the subsequent condenser from being blocked.

Claims

Patentansprüche claims
1. Verfahren zur Wirkungsgradverbesserung in Wärmekraft¬ werken mit kühlwassserseitig in Reihe geschalteten Kondensatoren,1. Process for improving the efficiency in thermal power plants with condensers connected in series on the cooling water side,
dadurch gekennzeichnet, daß bei Unterschreiten einer vorgegebenen Grenztempe¬ ratur des Kühlwassers der Kühlwasserstrom vor Eintritt in den ersten Kondensator geteilt wird, so daß nur ein Teil des Kühlwasserstromes den Kondensator durchströmt während der verbleibende Teilstrom über einen Bypass den Kondensator umfährt, und daß beide Teilströme un¬ mittelbar hinter dem Kondensator, vor Eintritt in den folgenden Kondensator, wieder zusammengeführt werden.characterized in that if the cooling water flow falls below a predetermined limit, the cooling water flow is divided before entering the first condenser, so that only part of the cooling water flow flows through the condenser while the remaining part flow bypasses the condenser, and that both part flows un ¬ indirectly behind the capacitor, before entering the following capacitor, be merged again.
2. Verfahren nach Anspruch 1,2. The method according to claim 1,
dadurch gekennzeichnet. daß bei mehr als zwei kuhlwasserseitig in Reihe ge¬ schalteten Kondensatoren weitere nachgeschaltete Kon¬ densatoren von einem Bypass-Teilstrom umfahren werden.characterized. that in the case of more than two condensers connected in series on the cooling water side, further bypass condensers are bypassed by a bypass partial flow.
3. Verfahren nach einem der Ansprüche 1 und 2,3. The method according to any one of claims 1 and 2,
dadurch gekennzeichnet, daß das Verhältnis von Bypass-Teilstrom zu Kühlwasser- Teilstrom für jeden umfahrenen Kondensator in Abhän¬ gigkeit von dessen Kühlwasseraustrittstemperatur ein¬ gestellt oder geregelt wird. characterized in that the ratio of the bypass partial flow to the cooling water partial flow is set or regulated for each bypassed condenser as a function of its cooling water outlet temperature.
EP95925677A 1994-07-14 1995-07-07 Process for operating a thermal power station with condensers connected in series on the coolimg water side Expired - Lifetime EP0719378B1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE4424870A DE4424870A1 (en) 1994-07-14 1994-07-14 Process for improving efficiency in thermal power plants with condensers connected in series on the cooling water side
DE4424870 1994-07-14
PCT/DE1995/000860 WO1996002736A1 (en) 1994-07-14 1995-07-07 Process for improving efficiency in thermal power stations with series-connected condensers on the cooling water side

Publications (2)

Publication Number Publication Date
EP0719378A1 true EP0719378A1 (en) 1996-07-03
EP0719378B1 EP0719378B1 (en) 1998-05-20

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AT (1) ATE166427T1 (en)
AU (1) AU2973995A (en)
DE (2) DE4424870A1 (en)
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DE19626372C1 (en) * 1996-07-02 1997-11-27 Saarbergwerke Ag Method and device for improving the efficiency in steam power plants
EP0895050A3 (en) 1997-07-30 2000-05-24 Siemens Aktiengesellschaft Steam turbine plant
EP2307673A2 (en) * 2008-08-04 2011-04-13 United Technologies Corporation Cascaded condenser for multi-unit geothermal orc
CN107062927B (en) * 2017-04-19 2024-02-06 北京今大禹环境技术股份有限公司 Multistage condenser reverse cooling noncondensable gas system for sea water desalination and process thereof
CN114877491B (en) * 2022-05-12 2023-12-22 珠海格力电器股份有限公司 Central air conditioner water system work control method, central air conditioner water system and control device

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US4168030A (en) * 1976-10-22 1979-09-18 Timmerman Robert W Waste heat utilization system
DE2737539A1 (en) * 1977-08-19 1979-03-01 Steag Ag Series condensing system for multistage turbine plant - has condensate from one stage injected into exhaust of next stage
DD275591A3 (en) * 1986-05-30 1990-01-31 Turboatom METHOD FOR MULTIPLE PRECIPITATION OF CIRCULATORY WATER

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See references of WO9602736A1 *

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WO1996002736A1 (en) 1996-02-01
AU2973995A (en) 1996-02-16
DE59502250D1 (en) 1998-06-25
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ATE166427T1 (en) 1998-06-15
DK0719378T3 (en) 1999-01-25
DE4424870A1 (en) 1996-01-18

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