WO1995011371A1 - Method for improving electric plants of combined cycle with solar support - Google Patents

Method for improving electric plants of combined cycle with solar support Download PDF

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Publication number
WO1995011371A1
WO1995011371A1 PCT/ES1994/000102 ES9400102W WO9511371A1 WO 1995011371 A1 WO1995011371 A1 WO 1995011371A1 ES 9400102 W ES9400102 W ES 9400102W WO 9511371 A1 WO9511371 A1 WO 9511371A1
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WIPO (PCT)
Prior art keywords
steam
solar
cycle
pressure
boiler
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PCT/ES1994/000102
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Spanish (es)
French (fr)
Inventor
Antonio Lara Cruz
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Compañia Sevillana De Electricidad, S.A.
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Application filed by Compañia Sevillana De Electricidad, S.A. filed Critical Compañia Sevillana De Electricidad, S.A.
Publication of WO1995011371A1 publication Critical patent/WO1995011371A1/en

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03G—SPRING, WEIGHT, INERTIA OR LIKE MOTORS; MECHANICAL-POWER PRODUCING DEVICES OR MECHANISMS, NOT OTHERWISE PROVIDED FOR OR USING ENERGY SOURCES NOT OTHERWISE PROVIDED FOR
    • F03G6/00—Devices for producing mechanical power from solar energy
    • F03G6/06—Devices for producing mechanical power from solar energy with solar energy concentrating means
    • F03G6/064—Devices for producing mechanical power from solar energy with solar energy concentrating means having a gas turbine cycle, i.e. compressor and gas turbine combination
    • 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
    • F01K23/00—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids
    • F01K23/02—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled
    • F01K23/06—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle
    • F01K23/10—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle with exhaust fluid of one cycle heating the fluid in another cycle
    • F01K23/106—Plants characterised by more than one engine delivering power external to the plant, the engines being driven by different fluids the engine cycles being thermally coupled combustion heat from one cycle heating the fluid in another cycle with exhaust fluid of one cycle heating the fluid in another cycle with water evaporated or preheated at different pressures in exhaust boiler
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F03—MACHINES OR ENGINES FOR LIQUIDS; WIND, SPRING, OR WEIGHT MOTORS; PRODUCING MECHANICAL POWER OR A REACTIVE PROPULSIVE THRUST, NOT OTHERWISE PROVIDED FOR
    • F03G—SPRING, WEIGHT, INERTIA OR LIKE MOTORS; MECHANICAL-POWER PRODUCING DEVICES OR MECHANISMS, NOT OTHERWISE PROVIDED FOR OR USING ENERGY SOURCES NOT OTHERWISE PROVIDED FOR
    • F03G6/00—Devices for producing mechanical power from solar energy
    • F03G6/06—Devices for producing mechanical power from solar energy with solar energy concentrating means
    • F03G6/065—Devices for producing mechanical power from solar energy with solar energy concentrating means having a Rankine cycle
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/40—Solar thermal energy, e.g. solar towers
    • Y02E10/46—Conversion of thermal power into mechanical power, e.g. Rankine, Stirling or solar thermal engines
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E20/00—Combustion technologies with mitigation potential
    • Y02E20/16—Combined cycle power plant [CCPP], or combined cycle gas turbine [CCGT]

Definitions

  • This invention consists of an improvement procedure applicable to combined-cycle power plants gas turbine-steam turbine in which it is desired to integrate an additional steam flow generated from solar energy.
  • power generation and / or congeneration plants by means of a combined cycle, which integrates a gas turbine and a steam cycle for the recovery of the exhaust gases from the gas turbine, steam cycles of one, two and three pressures (the latter usually including steam reheating at intermediate pressure), whose fundamental difference lies in the level of exergy losses available in said gases, in the process of transmitting energy to the steam cycle.
  • the recovery with a pressure cycle is the one that presents a maximum mismatch and therefore the greatest exergy losses, both due to the important thermal differences and the high temperature of the gases at the exit of the recovery boiler. Therefore, this cycle is practically not used, given its low performance, except in small installations, where its simplicity is imposed.
  • the most common scheme in combined cycle power plants is the two-pressure steam cycle, with which a better adjustment of the absorption curve is achieved, also allowing to reduce the outlet temperature of the gases, reducing the exergy losses and increasing Therefore the performance.
  • the three-pressure recovery cycle has begun to be used, with steam reheating at intermediate pressure, in the upper temperature zone of the gas turbine's exhaust gases.
  • This solution allows the upper pressure of the cycle to be raised up to pressures of the order of 100 bar and to improve the shape of the absorption curve in its adaptation to the transfer, thanks to the three vaporizations at different pressure and the increase of the global specific heat in the steam absorption zone, when the steam flow to be superheated and the superheat steam are added.
  • the improvement process object of this invention consists in working, during the periods of solar steam supply, with a higher pressure of the steam cycle higher than the optimum design of the corresponding combined basic cycle without solar steam input and working with a lower pressure, close to optimum, during periods of operation without solar steam.
  • the steam provided by the solar boiler can be saturated or overheated.
  • superheated steam it can have a significantly lower thermal level than the output of the recovery boiler or have practically the same thermal level as this one. In the latter case, it would be mixed with the outlet of the recovery boiler before entering the steam turbine. In the other case, additional overheating in the recovery boiler would be necessary.
  • saturated steam which is considered the most interesting alternative, it would be mixed with the saturated steam coming out of the high pressure boiler of the recovery boiler and would pass to the superheated one of the same, being thus integrated in the cycle steam.
  • the feed water to the solar boiler would be taken preferably from the outlet of the high pressure economizer from the recovery boiler or from the discharge of the recirculation pump of the high pressure vaporizer thereof.
  • the limit to which it is possible to raise the upper pressure of the cycle is determined by the maximum degree of final permissible humidity in the steam turbine from a maximum overheating temperature determined by the exhaust temperature of the gas turbine gases.
  • the reheating of the steam at intermediate pressure to the temperature allowed by said exhaust gases allows a significant increase in this higher pressure, without reaching high final humidity rates in the steam turbine.
  • the proposed invention basically allows the steam turbine to be sized for the nominal steam flow generated in the recovery boiler in the absence of solar steam, with the upper pressure of the steam cycle corresponding to this condition, so that the admission of a higher steam flow through the steam turbine during periods of operation with solar steam is possible thanks to the characteristic increase in the upper pressure of the steam cycle and therefore , of the pressure at the steam turbine inlet, in this other condition.
  • This lack of oversizing of the steam turbine could even affect its escape, allowing an increase in the losses of the output speed in the condition with solar steam input, limited on the other hand by the slight increase that would occur in the Condensation pressure in the latter condition, if no condenser surfaces or cooling water flow rates are modified, due to the greater flow of steam to condense.
  • the recovery boiler must also be designed for the maximum upper pressure (with solar steam input) and each of its changers must be adequately sized to adapt optimally to the extreme operating conditions, so that under conditions of maximum demand for surface the thermal differentials of design are reached and under conditions of minimum required surface the appropriate typical actions (temperings, recirculations, etc.) are carried out to prevent excessive overheating or unwanted vaporization.
  • the available flow rate of contribution steam to the combined cycle is variable in time, and can oscillate from a null value to the maximum design value.
  • the proposed invention allows to operate satisfactorily in the two extreme conditions indicated, with an optimal regulation for intermediate transitory conditions.
  • the most appropriate solution in this case consists in the use of a regulation system of the power plant by means of variable boiler pressure, so that the turbine admits, with fully open inlet valves, the nominal steam flow generated in the recovery of the Exhaust gases from the gas turbine, in operation as a combined cycle without solar steam, and expand it to the condensation pressure.
  • the intake pressure in the turbine is increased, as the flow of steam to be admitted in the same temperature conditions is higher, so that the pressure at which This steam is generated, both in the solar boiler and at the upper pressure level of the recovery boiler, continuously up to the nominal value corresponding to the maximum contribution of solar steam.
  • said burners in addition to the usual boiler inlet, would be installed in the inlet of the high pressure vaporizer of the boiler, in order not to affect the operating conditions in the superheater with its operation, acting only on saturated steam generated in the recovery boiler.
  • said vaporizer in a smooth tube (without fins) in order to improve its working conditions and decrease its thermal inertia, so that the response capacity of this set is similar to or greater than the disturbance caused by the change of contribution of steam of solar origin to any transitory of this energy, in order to be able to control the operating parameters of the steam cycle in any situation.
  • This solution could be used both for the control of unforeseen transients and periods of absence of sun, as well as for other periods of peak demand of electrical energy in periods of absence of expected sun, if the design of the plant contemplates a maximum power with solar input or with post-combustion greater than the nominal power of the base combined cycle, based on keeping the gas turbine at full load and increasing the power of the steam turbine during those periods. Under these conditions, it would operate with a lower power, that of the combined base cycle, during the hours of lower demand for electricity.
  • the proposed invention in relation to existing solutions offers the following advantages:. Possibility of avoiding or limiting the oversizing and, therefore, the increase in cost of the steam turbine, with respect to the basic dimensions required by the design of the combined cycle plant without making the contribution of solar steam, as well as the need for reduce the load of the gas turbine and, by Therefore, the power generated, under conditions of high solar steam.
  • -. Reduction of exergy losses due to heat transmission of gases to the fluid in the high pressure area of the recovery boiler.
  • the proposed invention offers the following additional advantages:. High stability of the thermal conditions in the intake and early stages of the steam turbine, with significant reduction of the thermal stresses associated with load changes. -. Possibility of avoiding the multi-valve control and the steam turbine regulation stage, with the consequent reduction of costs and improvement of yields. -. Provisions of an important to the macenam and thermal entourage without cost and self-regulated, in the boilers themselves and high-pressure pipes of the installation, which dampens the transients derived from the fluctuations of solar radiation. As a whole, all the above advantages allow reducing investment costs, at least in larger plants, and increasing the overall performance of the plant, for a given solar energy contribution, leading to greater profitability of this type of combined cycle power plants with solar support.
  • the other proposed improvement, using post-combustion burners offers the following advantages:. Improvement of the operating conditions of the equipment, stabilizing its operating parameters before changes in the contribution of solar steam. -. Possibility of controlling the power generated in accordance with various operating programs of the plant. -. Possibility of increasing the participation of solar energy (broadly) in the energy balance of the plant and / or reducing or eliminating the need to increase the size of the superheater of the recovery boiler, using biofuels of biological origin- post-combustion solar.
  • Figure 1 shows an application scheme, including the following equipment: 1.- Heliostat field
  • the total steam flow generated in the recovery boiler is lower than in the operation without solar steam supply, so the vaporizers will have to be sized for the latter condition, being oversized for the first case, which only translates into a small reduction of the minimum thermal differentials in said operating condition, not affecting the functionality of the system at all.
  • the superheater must be sized for the maximum solar steam supply condition, being somewhat oversized in the other extreme operating condition, which is not a problem, as it can be perfectly resolved by tempering with liquid water to control the maximum overheating temperature , as usual in this type of facilities.
  • said oversizing of the superheater with respect to the sizing required by the base combined cycle, can be reduced or avoided by resorting to the use of typical post-combustion burners located at the entrance of the recovery boiler in the periods of solar steam supply , fed with the same fossil fuel of the gas turbine, at the cost of reducing the overall performance and solar participation, or, better still, with biological fuels obtained from biomass.
  • the economizers for liquid heating at the different pressures of the cycle will be optimally sized in each case from a technical point of view and economical, which will normally lead to an oversize in the operation as a combined cycle without solar steam.
  • liquid recirculations or other usual systems of control of this phenomenon should be provided.
  • the absorption curves in the economizers have been represented in the figure without taking into account the possible recirculations required as normally done, given that both representations are totally equivalent from the thermodynamic point of view , and this form, which logically coincides with the typical of a combined cycle of two pressures, facilitates the compression of the diagram.
  • the low temperature recovery zone including the generation of the small steam flow for the deaerator, allows for a higher cooling of the gases in the operating condition with solar steam, due to the fact that it has a higher liquid flow to heat in this condition.

Abstract

Method for improving electric plants of combined cycle with external steam supply from solar energy, consisting in using two complementary processes which may also be used independently with substantial advantages for conventional plants of this type. The first process consists in operating, during the periods of solar steam supply, with a high pressure of the steam cycle higher than the optimum rating pressure of the corresponding basic combined cycle without solar steam supply, thereby increasing the efficiency and output and minimizing the size of equipments. The second process comprises the use of post-combustion burners designed in association with the recovery boiler, so as to make up for deficiency transients of external steam supply, and to obtain the power generated by the plant independently from the solar steam supply.

Description

PROCEDIMIENTO DE MEJORA PARA CENTRALES ELÉCTRICAS DE CICLOIMPROVEMENT PROCEDURE FOR CYCLE POWER STATIONS
COMBINADO CON APOYO SOLAR COMBINED WITH SOLAR SUPPORT
Esta invención consiste en υn procedimiento de mejora aplicable a centrales eléctricas de ciclo combinado turbina de gas-turbina de vapor en las que se desea integrar un caudal de vapor adicional generado a partir de energía solar. En centrales de generación eléctrica y/o de congeneración mediante un ciclo combinado, que integra una turbina de gas y un ciclo de vapor para la recuperación de los gases de escape de la turbina de gas, se emplean ciclos de vapor de una, dos y tres presiones (este ultimo incluyendo habitualmente recalentamiento del vapor a presión intermedia), cuya diferencia fundamental estriba en el nivel de las pérdidas de la exergía disponible en dichos gases, en el proceso de transmisión de energía al ciclo de vapor. This invention consists of an improvement procedure applicable to combined-cycle power plants gas turbine-steam turbine in which it is desired to integrate an additional steam flow generated from solar energy. In power generation and / or congeneration plants by means of a combined cycle, which integrates a gas turbine and a steam cycle for the recovery of the exhaust gases from the gas turbine, steam cycles of one, two and three pressures (the latter usually including steam reheating at intermediate pressure), whose fundamental difference lies in the level of exergy losses available in said gases, in the process of transmitting energy to the steam cycle.
El acoplamiento de las curvas de cesión y absorción de calor en la caldera de recuperación, en el diagrama Temperatura-Potencia térmica intercambiada, no es perfecto, debido a la diferencia de forma que adoptan las mismas, lo que se traduce en degradaciones energéticas superiores siempre a las mínimas requeridas por el diseño práctico del cambiador en caso de que fuesen prácticamente paralelas. El calor específico de los gases se mantiene prácticamente constante, mientras que este calor es absorbido mediante calentamientos de agua líquida con calor específico prácticamente constante, vaporizaciones isotérmicas con calor específico infinito y sobrecalentamientos-recalentamientos de vapor con calor específico también constante, pero diferente del correspondiente al del agua líquida. Todo ello imposibilita la adaptación de estas curvas, afectando lógicamente al rendimiento de transformación alcanzable. The coupling of the heat transfer and absorption curves in the recovery boiler, in the Temperature-Heat exchanged diagram, is not perfect, due to the difference in the way they adopt them, which translates into higher energy degradations always to the minimum required by the practical design of the changer in case they were practically parallel. The specific heat of the gases remains practically constant, while this heat is absorbed by heating of liquid water with specific heat practically constant, isothermal vaporizations with infinite specific heat and superheating-superheating of steam with specific heat also constant, but different from the corresponding of liquid water. All of it It makes it impossible to adapt these curves, logically affecting the attainable transformation performance.
La recuperación con ciclo de una presión es la que presenta un desajuste máximo y por tanto las mayores pérdidas exergéticas, tanto por las importantes diferencias térmicas como por la alta temperatura de los gases a la salida de la caldera de recuperación. Por ello este ciclo prácticamente no se emplea, dado su bajo rendimiento, salvo en pequeñas instalaciones, donde se impone su sencillez. The recovery with a pressure cycle is the one that presents a maximum mismatch and therefore the greatest exergy losses, both due to the important thermal differences and the high temperature of the gases at the exit of the recovery boiler. Therefore, this cycle is practically not used, given its low performance, except in small installations, where its simplicity is imposed.
El esquema más habitual en centrales de ciclo combinado es el de ciclo de vapor de dos presiones, con el que se consigue un mejor ajuste de la curva de absorción, permitiendo además reducir la temperatura de salida de los gases, disminuyendo las pérdidas exergéticas e incrementando por ello el rendimiento. En la actualidad, para nuevas centrales, ha comenzado a utilizarse el ciclo de recuperación de tres presiones, con recalentamiento del vapor a presión intermedia, en la zona de superior temperatura de los gases de escape de la turbina de gas. Esta solución permite subir la presión superior del ciclo hasta presiones del orden de 100 bar y mejorar la forma de la curva de absorción en su adaptacicon a la de cesión, gracias a las tres vaporizaciones a diferente presión y al incremento del calor específico global en la zona de absorción del vapor, al sumarse el del caudal de vapor a sobrecalentar y el del vapor de recalentamiento. Este ciclo se adapta especialmente bien a las turbinas de gas avanzadas, con alta temperatura de gases de escape y ofrece lógicamente los máximos rendimientos comerciales. En las propuestas realizadas hasta la fecha de integración de vapor generado mediante energía solar en una central de ciclo combinado, el vapor solar se genera a una presión similar o inferior a la presión superior óptima de operación del ciclo combinado básico correspondiente sin aporte de vapor solar, incorporándose al ciclo de vapor en un punto adecuado, por sus similares condiciones de presión y temperatura, manteniéndose constante, con o sin aportación de vapor de origen solar, la presión superior de trabajo del ciclo de vapor. The most common scheme in combined cycle power plants is the two-pressure steam cycle, with which a better adjustment of the absorption curve is achieved, also allowing to reduce the outlet temperature of the gases, reducing the exergy losses and increasing Therefore the performance. At present, for three new plants, the three-pressure recovery cycle has begun to be used, with steam reheating at intermediate pressure, in the upper temperature zone of the gas turbine's exhaust gases. This solution allows the upper pressure of the cycle to be raised up to pressures of the order of 100 bar and to improve the shape of the absorption curve in its adaptation to the transfer, thanks to the three vaporizations at different pressure and the increase of the global specific heat in the steam absorption zone, when the steam flow to be superheated and the superheat steam are added. This cycle adapts especially well to advanced gas turbines, with high exhaust gas temperature and logically offers the highest commercial yields. In the proposals made to date of integration of steam generated by solar energy in a combined cycle power plant, solar steam is generated at a pressure similar to or lower than the optimum upper operating pressure of the corresponding basic combined cycle without solar steam input , incorporating to the steam cycle at a suitable point, due to its similar pressure and temperature conditions, maintaining, with or without the contribution of steam of solar origin, the upper working pressure of the steam cycle.
Estas solluciones tienen como principales inconvenientes los siguientes: -. Necesidad de sobredimensionar la turbina de vapor, respecto al dimensionamiento requerido sin considerar el aporte de vapor solar, o necesidad de reducir la carga de la turbina de gas en períodos de aporte de vapor solar, o ambas cosas a la vez. -. Operación fuera del punto de óptimo rendimiento de la turbina de vapor en períodos sin aporte de vapor solar o, incluso, en períodos con aporte de vapor solar, al menos en la sección de alta de la turbina, si se suministra vapor solar a presión inferior a la de entrada a turbina. - .. Mantenimiento de parte de las pérdidas exergéticas por transmisión de calor en la caldera de recuperación, como consecuencia de la inalteración del nivel isotérmico de la vaporización a la presión superior constante del ciclo de vapor. - . Limitación de la presión de generación del vapor en la caldera solar a la presión superior del ciclo de vapor, con las consecuentes pérdidas exergéticas asociadas a su nivel térmico limitado. These solutions have the following main drawbacks:. Need to oversize the steam turbine, with respect to the required sizing without considering the contribution of solar steam, or the need to reduce the load of the gas turbine during periods of solar steam supply, or both at the same time. -. Operation outside the point of optimum performance of the steam turbine in periods without solar steam or even in periods with solar steam, at least in the high section of the turbine, if solar steam is supplied at lower pressure to the turbine entrance. - .. Maintenance of part of the exergy losses due to heat transmission in the recovery boiler, as a result of the alteration of the isothermal level of vaporization at the constant upper pressure of the steam cycle. -. Limitation of the steam generation pressure in the solar boiler to the upper pressure of the cycle steam, with the consequent exergy losses associated with its limited thermal level.
El procedimiento de mejora objeto de esta invención consiste en trabajar, durante los períodos de aporte de vapor solar, con una presión superior del ciclo de vapor más alta que la óptima de diseño del ciclo combinado básico correpondiente sin aporte de vapor solar y trabajar con una presión más baja, próxima a la óptima, durante los períodos de operación sin aporte de vapor solar. Ello permite evitar o limitar los inconvenientes anteπormente citados de las soluciones actuales, además de ofrecer, en caso de instalaciones solares sin almacenamiento térmico, una mayor sencillez en la regulación de los transitorios de radiación solar, con una mayor capacidad intrínseca de almacenamiento de energía térmica de amortiguación en forma de agua caliente y vapor a presión, en los propios elementos de proceso de la instalación (caldeπnes, tuberías, etc.). The improvement process object of this invention consists in working, during the periods of solar steam supply, with a higher pressure of the steam cycle higher than the optimum design of the corresponding combined basic cycle without solar steam input and working with a lower pressure, close to optimum, during periods of operation without solar steam. This allows avoiding or limiting the aforementioned inconveniences of the current solutions, in addition to offering, in the case of solar installations without thermal storage, greater simplicity in the regulation of solar radiation transients, with a greater intrinsic capacity for thermal energy storage damping in the form of hot water and steam under pressure, in the process elements of the installation (boilers, pipes, etc.).
El vapor aportado por la caldera solar puede ser saturado o sobrecalentado. Tratándose de vapor sobrecalentado puede tener un nivel térmico notablemente inferior que el de salida de la caldera de recuperación o tener prácticamente el mismo mvel térmico que éste. En este último caso se mezclaría con el de salida de la caldera de recuperación antes de la entrada a la turbina de vapor. En el otro caso sería preciso un sobrecalentamiento adicional en la caldera de recuperación. En el caso particular de tratarse de vapor saturado, que se considera la alternativa más interesante, se mezclaría con el vapor saturado de salida del calderín de alta presión de la caldera de recuperación y pasaría al sobrecalentado de la misma, quedando así integrado en el ciclo de vapor. En todos los casos el agua de alimentación a la caldera solar se tomaría preferentemente de la salida del economizador de alta presión de la caldera de recuperación o de la descarga de la bomba de recirculación del vaporizador de alta presión de la misma. The steam provided by the solar boiler can be saturated or overheated. In the case of superheated steam, it can have a significantly lower thermal level than the output of the recovery boiler or have practically the same thermal level as this one. In the latter case, it would be mixed with the outlet of the recovery boiler before entering the steam turbine. In the other case, additional overheating in the recovery boiler would be necessary. In the particular case of being saturated steam, which is considered the most interesting alternative, it would be mixed with the saturated steam coming out of the high pressure boiler of the recovery boiler and would pass to the superheated one of the same, being thus integrated in the cycle steam. In all cases the feed water to the solar boiler would be taken preferably from the outlet of the high pressure economizer from the recovery boiler or from the discharge of the recirculation pump of the high pressure vaporizer thereof.
El suministro de este vapor adicional de origen solar al ciclo de vapor de la central aumenta el caudal disponible de líquido a calentar y, tratándose de vapor saturado o ligeramente sobrecalentado, el de vapor a sobrecalentar (y en su caso recalentar) con la energía de los gases de escape, lo que incrementa la capacidad calorífica de estas zonas de las curvas de absorción, mej orando notablemente la adaptación de las mismas, disminuyendo consecυentemente las citadas pérdidas exergéticas y permitiendo realizar el aumento característico de la presión superior del ciclo. Esto último incrementa el nivel térmico medio de absorción de calor, lo que conduce a una mejora del rendimiento respecto a las opciones existentes. El límite al que es posible subir la presión superior del ciclo, en el caso del ciclo de una o dos presiones, esta determinado por el máximo grado de humedad final admisible en la turbina de vapor al partir de una temperatura máxima de sobrecalentamiento determinada por la temperatura de escape de los gases de la turbina de gas. Sin embargo, en el ciclo de tres presiones, el recalentamiento del vapor a presión intermedia hasta la temperatura permitida por dichos gases de escape, permite un importante incremento de esta presión superior, sin llegar a tasas elevadas de humedad final en la turbina de vapor. The supply of this additional steam of solar origin to the steam cycle of the plant increases the available flow of liquid to be heated and, in the case of saturated or slightly overheated steam, that of steam to be superheated (and if necessary reheated) with the energy of Exhaust gases, which increases the heat capacity of these areas of the absorption curves, significantly improving their adaptation, consequently decreasing the said exergy losses and allowing the characteristic increase in the upper pressure of the cycle. The latter increases the average thermal level of heat absorption, which leads to an improvement in performance compared to existing options. The limit to which it is possible to raise the upper pressure of the cycle, in the case of the one or two pressure cycle, is determined by the maximum degree of final permissible humidity in the steam turbine from a maximum overheating temperature determined by the exhaust temperature of the gas turbine gases. However, in the three-pressure cycle, the reheating of the steam at intermediate pressure to the temperature allowed by said exhaust gases, allows a significant increase in this higher pressure, without reaching high final humidity rates in the steam turbine.
La invención propuesta permite dimensionar básicamente la turbina de vapor para el caudal de vapor nominal generado en la caldera de recuperación en ausencia de aporte de vapor solar, con la presión superior del ciclo de vapor correspondiente a esta condición, de tal forma que la admisión de un caudal de vapor mayor por la turbina de vapor durante los períodos de operación con aporte de vapor solar es posible gracias al incremento característico de la presión superior del ciclo de vapor y, por tanto, de la presión en la entrada de la turbina de vapor, en esta otra condición. Esta ausencia de sobredimensionamiento de la turbina de vapor podría afectar incluso al escape de la misma, permitiendo un aumento de las pérdidas de velocidad de salida en la condición con aporte de vapor solar, limitadas por otra parte por el ligero incremento que se produciría en la presión de condensación en esta última condición, si no se modificasen superficies del condensador ni caυdales del agua de refrigeración, debido al mayor caudal de vapor a condensar. En todo caso las pérdidas correspondientes a este incremento de la presión de condensación, junto con las posibles pérdidas adicionales por velocidad de salida, son notablemente inferiores a las reducciones de pérdidas exergéticas en la absorción de energía. Naturamelente, seré preciso que el diseño de la turbina de vapor, tanto desde el punto de vista mecánico como termohidrául ico contemple ambas condiciones de operación, con objeto de encontrar el punto de equilibrio óptimo. The proposed invention basically allows the steam turbine to be sized for the nominal steam flow generated in the recovery boiler in the absence of solar steam, with the upper pressure of the steam cycle corresponding to this condition, so that the admission of a higher steam flow through the steam turbine during periods of operation with solar steam is possible thanks to the characteristic increase in the upper pressure of the steam cycle and therefore , of the pressure at the steam turbine inlet, in this other condition. This lack of oversizing of the steam turbine could even affect its escape, allowing an increase in the losses of the output speed in the condition with solar steam input, limited on the other hand by the slight increase that would occur in the Condensation pressure in the latter condition, if no condenser surfaces or cooling water flow rates are modified, due to the greater flow of steam to condense. In any case, the losses corresponding to this increase in the condensation pressure, together with the possible additional losses due to the output speed, are significantly lower than the reductions of exergetic losses in energy absorption. Naturally, it will be necessary that the design of the steam turbine, both from a mechanical and thermohydraulic point of view, contemplates both operating conditions, in order to find the optimum equilibrium point.
La caldera de recuperación deberá diseñarse asimismo para la presión superior máxima (con aporte de vapor solar) y cada uno de sus cambiadores deberá dimensionarse adecuadamente para adaptarse de forma óptima a las condiciones extremas de operación, de tal forma que en condiciones de máxima demanda de superficie se alcancen los diferenciales térmicos de diseño y en condiciones de mínima superficie requeπda se realicen las acciones típicas adecuadas (atempereciones, recirculaciones, etc.) para impedir sobrecalentamientos excesivos o vaporizaciones indeseadas. The recovery boiler must also be designed for the maximum upper pressure (with solar steam input) and each of its changers must be adequately sized to adapt optimally to the extreme operating conditions, so that under conditions of maximum demand for surface the thermal differentials of design are reached and under conditions of minimum required surface the appropriate typical actions (temperings, recirculations, etc.) are carried out to prevent excessive overheating or unwanted vaporization.
En el caso habitual de aporte de vapor solar siguiendo la potencia de la radiación solar, sin almacenamientos e5pecíficos de energía térmica (tanques de fluido térmico o sales), el caudal disponible de vapor de aportación al ciclo combinado es variable en el tiempo, pudiendo oscilar desde un valor nulo hasta el valor máximo de diseño. La invención propuesta permite operar satisfactoriamente en las dos condiciones extremas indicadas, con una óptima regulación para las condiciones transitorias intermedias. In the usual case of solar steam supply following the power of solar radiation, without specific thermal energy storage (thermal fluid tanks or salts), the available flow rate of contribution steam to the combined cycle is variable in time, and can oscillate from a null value to the maximum design value. The proposed invention allows to operate satisfactorily in the two extreme conditions indicated, with an optimal regulation for intermediate transitory conditions.
La solución más adecuada en este caso consiste en el empleo de un sistema de regulación de la central mediante presión variable en caldera, de forma que la turbina admite, con vávulas de entrada totalmente abiertas, el caudal de vapor nominal generado en la recuperación de los gases de escape de la turbina de gas, en operación como ciclo combinado sin aporte de vapor solar, y lo expansiona hasta la presión de condensación. En el momento en que se produce aportación de vapor solar, la presión de admisión en la turbina se incrementa, al ser superior el caudal de vapor a admitir en las mismas condiciones de temperatura, por lo que en forma automática aumenta la presión a la que se genera este vapor, tanto en la caldera solar como al nivel superior de presión de la caldera de recuperación, en forma continua hasta el valor nominal correspondiente a la máxima aportación de vapor solar. También sería posible una operación con presión constante en ausencia de aporte de vapor solar, que se mantendría hasta que las vávulas de entrada a turbina abriesen totalmente al alcanzarse un caudal determinado de vapor solar, comenzando a partir de este punto la operación a presión variable. Adicionalmente con objeto de mejorar aún más las condiciones operativas de los equipos y de tener un control sobre la potencia generada, se propone otro procedimiento de mejora combinable o no con el procedimiento de mejora descrito y aplicable de forma especialmente idónea en los casos en que el aporte de vapor generado en la caldera solar al ciclo de vapor se realice en forma de vapor saturado, consistente en el empleo de qυemadores de postcombustión en vena gaseosa en la caldera de recuperación de los gases de escape de la turbina de gas, instalados de forma que permitan compensar con su actuación los cambios del aporte de vapor solar. The most appropriate solution in this case consists in the use of a regulation system of the power plant by means of variable boiler pressure, so that the turbine admits, with fully open inlet valves, the nominal steam flow generated in the recovery of the Exhaust gases from the gas turbine, in operation as a combined cycle without solar steam, and expand it to the condensation pressure. At the moment when solar steam is produced, the intake pressure in the turbine is increased, as the flow of steam to be admitted in the same temperature conditions is higher, so that the pressure at which This steam is generated, both in the solar boiler and at the upper pressure level of the recovery boiler, continuously up to the nominal value corresponding to the maximum contribution of solar steam. An operation with constant pressure would also be possible in the absence of solar steam, which would be maintained until the turbine inlet valves fully opened when a certain flow of solar steam was reached, starting from this point the operation at variable pressure. Additionally in order to further improve the operating conditions of the equipment and having a control over the power generated, another improvement procedure is proposed that can be combined or not with the improvement procedure described and applicable in a particularly suitable way in cases where the supply of steam generated in the solar boiler The steam cycle is carried out in the form of saturated steam, consisting of the use of post-combustion gas burners in the gas vein in the recovery boiler of the gas turbine's exhaust gases, installed in such a way that they can compensate with their performance for changes of the contribution of solar steam.
Para conseguir este objetivo, dichos quemadores, adicionales a los habituales de la entrada de la caldera, se instalarían en la entrada del vaporizador de alta presión de la misma, con objeto de no afectar con su operación las condiciones de trabajo en el sobrecalentador, actuando únicamente sobre el vapor saturado generado en la caldera de recuperación. En estas condiciones es posible tener que prever una zona de dicho vaporizador en tubo liso (sin aletas) con el fin de mejorar sus condiciones de trabajo y disminuir su inercia térmica, de forma que la capacidad de respuesta de este conjunto sea similar o superior a la perturbación originada por el cambio de aportación de vapor de origen solar ante cualquier transitorio de esta energía, con objeto de poder mantener controlados los parámetros de operación del ciclo de vapor en toda situación. Como del combustible utilizado en postcombustión se obtiene un rendimiento de transformación menor que el que se obtiene del consumido en la turbina de gas, si se utiliza en postcombustión el mismo combυstible fósil de la turbina de gas el rendimiento global de la central se reduce, pero en una medida tan pequefía que queda ampliamente compensado por el incremento del rendimiento derivado de la aportación solar. To achieve this objective, said burners, in addition to the usual boiler inlet, would be installed in the inlet of the high pressure vaporizer of the boiler, in order not to affect the operating conditions in the superheater with its operation, acting only on saturated steam generated in the recovery boiler. Under these conditions it is possible to have to provide an area of said vaporizer in a smooth tube (without fins) in order to improve its working conditions and decrease its thermal inertia, so that the response capacity of this set is similar to or greater than the disturbance caused by the change of contribution of steam of solar origin to any transitory of this energy, in order to be able to control the operating parameters of the steam cycle in any situation. As the fuel used in post-combustion, a lower transformation efficiency is obtained than that obtained from the one consumed in the gas turbine, if the same fossil fuel from the gas turbine is used in post-combustion, the overall performance of the plant is reduced, but to such a small extent that it remains widely offset by the increase in yield derived from the solar contribution.
Sin embargo, también es posible el empleo de otro tipo de combustibles obtenidos a partir de biomasa (tales como bioalcoholes o bioaceites) para la alimentación de estos quemadores de postcombustión, lo que supone aportación de energía solar almacenada biológicamente en los períodos de ausencia del sol, incrementando de esta forma la participación media anual de la energía solar (en sentido amplio) en el balance energético de la central, sin las desventajas técnico-económicas de los almacenamientos térmicos. Esta solución podría emplearse tanto para el control de transitorios y períodos de ausencia de sol imprevistos, como para otros períodos de demanda punta de enrgía eléctrica en períodos de ausencia de sol prevista, si el diseño de la central contempla una potencia máxima con aporte solar o con postcombustión superior a la pontencia nominal del ciclo combinado base, basándose en mantener la turbina de gas a plena carga e incrementar la potencia de la turbina de vapor en dichos períodos. En estas condiciones se operaría con una potencia más baja, la del ciclo combinado base, durante las horas de menor demanda de energía eléctrica. However, it is also possible to use other types of fuels obtained from biomass (such as bioalcohols or bio-oils) to feed these post-combustion burners, which implies the contribution of biologically stored solar energy during periods of absence from the sun , thereby increasing the average annual participation of solar energy (broadly) in the energy balance of the plant, without the technical-economic disadvantages of thermal storage. This solution could be used both for the control of unforeseen transients and periods of absence of sun, as well as for other periods of peak demand of electrical energy in periods of absence of expected sun, if the design of the plant contemplates a maximum power with solar input or with post-combustion greater than the nominal power of the base combined cycle, based on keeping the gas turbine at full load and increasing the power of the steam turbine during those periods. Under these conditions, it would operate with a lower power, that of the combined base cycle, during the hours of lower demand for electricity.
De acuerdo con lo expuesto, la invención propuesta en relación con las soluciones existentes ofrece las siguientes ventajas: -. Posibilidad de evitar o limitar el sobredimensionamiento y, por tanto, el incremento de coste de la turbina de vapor, respecto a las dimensiones básicas requeridas por el diseño de la central de ciclo combinado sin efectuar el aporte de vapor solar, así como la necesidad de reducir la carga de la turbina de gas y, por tanto, la potencia generada, en condiciones de alto aporte de vapor solar. - Operación de la turbina de vapor y de la turbina de gas en condiciones de rendimiento prácticamente óptimo, tanto en condiciones de operación con aporte de vapor solar como en ausencia del mismo. -. Reducción de las pérdidas exergéticas por transmisión de calor de los gases al fluido en la zona de alta presión de la caldera de recuperación. -. Reducción de las pérdidas exergέticas por transmisión de calor en la caldera solar. In accordance with the foregoing, the proposed invention in relation to existing solutions offers the following advantages:. Possibility of avoiding or limiting the oversizing and, therefore, the increase in cost of the steam turbine, with respect to the basic dimensions required by the design of the combined cycle plant without making the contribution of solar steam, as well as the need for reduce the load of the gas turbine and, by Therefore, the power generated, under conditions of high solar steam. - Operation of the steam turbine and the gas turbine in conditions of practically optimal performance, both under operating conditions and with the absence of solar steam. -. Reduction of exergy losses due to heat transmission of gases to the fluid in the high pressure area of the recovery boiler. -. Reduction of exergy losses due to heat transmission in the solar boiler.
En el caso de utilización de sistemas solares sin almacenamiento específico de energía térmica y regulación del sistema con presión variable, la invención propuesta ofrece las siguientes ventajas adicionales: -. Alta estabilidad de las condiciones térmicas en la admisión y primeras etapas de la turbina de vapor, con importante reducción de las tensiones térmicas asociadas a los cambios de carga. -. Posibilidad de evitar el control multiválvula y la etapa de regυlación de la turbina de vapor, con la consiguiente reducción de costes y mejora de rendimientos. -. Dispos i c i ón de un importante a l macenam i ento térmi co s i n coste y autorregulado, en los propios calderines y tuberías de alta presión de la instalación, que amortigua los transitorios derivados de las fluctuaciones de la radiación solar. En su conjunto, todas las ventajas anteriores permiten reducir los costes de inversión, al menos en las plantas de mayor tamaño, y aumentar el rendimiento global de la central, para un determinado aporte de energía solar, conduciendo a una mayor rentabilidad de este tipo de centrales de ciclo combinado con apoyo solar. In the case of using solar systems without specific storage of thermal energy and regulation of the system with variable pressure, the proposed invention offers the following additional advantages:. High stability of the thermal conditions in the intake and early stages of the steam turbine, with significant reduction of the thermal stresses associated with load changes. -. Possibility of avoiding the multi-valve control and the steam turbine regulation stage, with the consequent reduction of costs and improvement of yields. -. Provisions of an important to the macenam and thermal entourage without cost and self-regulated, in the boilers themselves and high-pressure pipes of the installation, which dampens the transients derived from the fluctuations of solar radiation. As a whole, all the above advantages allow reducing investment costs, at least in larger plants, and increasing the overall performance of the plant, for a given solar energy contribution, leading to greater profitability of this type of combined cycle power plants with solar support.
Adicionalmente, la otra mejora propuesta, utilizando quemadores de postcombustión, ofrece las siguientes ventajas: -. Mejora de las condiciones operativas de los equipos, estabilizando sus parámetros de funcionamiento ante cambios en el aporte de vapor solar. -. Posibilidad de controlar la potencia generada de acuerdo con diversos programas de explotación de la central. -. Posibilidad de incrementar la participación de la energía solar (en sentido amplio) en el balance energético de la planta y/o reducir o eliminar la necesidad de incrementar el tamaño del sobrecalentador de la caldera de recuperación, recurriendo al uso de biocarburantes de origen biológico-solar para la postcombustión. Additionally, the other proposed improvement, using post-combustion burners, offers the following advantages:. Improvement of the operating conditions of the equipment, stabilizing its operating parameters before changes in the contribution of solar steam. -. Possibility of controlling the power generated in accordance with various operating programs of the plant. -. Possibility of increasing the participation of solar energy (broadly) in the energy balance of the plant and / or reducing or eliminating the need to increase the size of the superheater of the recovery boiler, using biofuels of biological origin- post-combustion solar.
Estas ventajas adicionales permiten mejorar ampliamente los resultados económicos anuales de este tipo de centrales con apoyo solar, debido a la mayor generación de energía eléctrica, además de mejorar su capacidad de respuesta a los requisitos de la red, incrementando así la valoración de su potencia instalada. Por otra parte, permiten incrementar la participación de la energía solar (en sentido amplio), mejorando los rendimientos efectivos de transformación de los combustibles fósiles empleados y reduciendo las emisiones contaminates por unidad de energía eléctrica generada. These additional advantages make it possible to greatly improve the annual economic results of this type of solar-powered plants, due to the greater generation of electricity, as well as improving their capacity to respond to the network's requirements, thus increasing the valuation of their installed power . On the other hand, they allow to increase the participation of solar energy (in a broad sense), improving the effective transformation yields of fossil fuels used and reducing pollutant emissions per unit of electric power generated.
Como ejemplo, con el fin de conseguir aclarar los conceptos indicados en la descripción precedente se incluyen las figuras 1 y 2. As an example, in order to clarify the concepts indicated in the preceding description, figures 1 and 2 are included.
En la figura 1 se expone un esquema de aplicación, incluyendo los siguientes equipos: 1.- Campo de heliostatos Figure 1 shows an application scheme, including the following equipment: 1.- Heliostat field
2.- Receptor solar, generador de vapor saturado 2.- Solar receiver, saturated steam generator
3.- Aporte de combustible para postcombustión 3.- Fuel supply for post-combustion
4.- Aporte de combustible para la turbina de gas 5.- Turbogrupo de gas 4.- Fuel supply for the gas turbine 5.- Gas turbine group
6.- caldera de recuperación 6.- recovery boiler
7.- Turbogrupo de vapor 7.- Steam Turbogroup
8.- condensador de vapor En la figura 2 se han representado en un diagrama Temeperatura-Potencia térmica intercambiada las curvas de absorción del calor de los gases de escape de la turbina de gas, correspondientes a un ciclo combinado de dos presiones, tanto en la condición de operación sin aporte de vapor solar (lo cual corresponde al caso típico de ciclo combinado de dos presiones;, como en la condición de operación con aporte de vapor solar máximo, operando de acuerdo con la primera mejora propuesta. Es posible apreciar claramente la importante mejora de adaptación de la curva de absorción a la de cesión de los gases, gracias a este aporte de vapor externo, así como la subida de la presión superior del ciclo y el mayor enfriamiento de los gases para su descarga a la atmósfera. Todo ello supone una gran mejora del rendimiento de transformación. 8.- steam condenser In Figure 2, the heat absorption curves of the gas turbine exhaust gases, corresponding to a combined cycle of two pressures, are shown in a Temeperatura-Thermal Power diagram. operating condition without contribution of solar steam (which corresponds to the typical case of combined cycle of two pressures ;, as in the operating condition with maximum solar steam supply, operating in accordance with the first improvement proposed. It is possible to clearly appreciate the Significant improvement in the adaptation of the absorption curve to that of the transfer of gases, thanks to this contribution of external steam, as well as the increase in the upper pressure of the cycle and the greater cooling of the gases for their discharge into the atmosphere. this means a great improvement in the performance of transformation.
En el caso de operación con aporte de vapor solar, el caudal total de vapor generado en la caldera de recuperación es inferior que en la operación sin aporte de vapor solar, por lo que los vaporizadores habrán de dimensionarse para esta última condición, quedando sobredimensionados para el primer caso, lo cual únicamente se traduce en una pequeña reducción de los diferenciales térmicos mínimos en dicha condición de operación, no afectando en absoluto a la funcionalidad del sistema. In the case of operation with solar steam supply, the total steam flow generated in the recovery boiler is lower than in the operation without solar steam supply, so the vaporizers will have to be sized for the latter condition, being oversized for the first case, which only translates into a small reduction of the minimum thermal differentials in said operating condition, not affecting the functionality of the system at all.
El sobrecalentador habrá de dimensionarse para la condición de aporte de vapor solar máximo, quedando algo sobredimensionado en la otra condición de operación extrema, lo cual no supone ningún problema, al poder resolverse perfectamente mediante atemperación con agua líquida para control de la máxima temperatura de sobrecalentamiento, como es habitual en este tipo de instalaciones. The superheater must be sized for the maximum solar steam supply condition, being somewhat oversized in the other extreme operating condition, which is not a problem, as it can be perfectly resolved by tempering with liquid water to control the maximum overheating temperature , as usual in this type of facilities.
Por otra parte, dicho sobredimensionamiento del sobrecalentador, respecto al dimensionamiento requerido por el ciclo combinado base, puede reducirse o evitarse recurriendo a la utilización de los quemadores de postcombustión típicos situados a la entrada de la caldera de recuperación en los períodos de aporte de vapor solar, alimentados con el mismo combustible fósil de la turbina de gas, a costa de reducir el rendimiento global y la participación solar, o, mejor aún, con combustibles biológicos obtenidos a partir de biomasa. On the other hand, said oversizing of the superheater, with respect to the sizing required by the base combined cycle, can be reduced or avoided by resorting to the use of typical post-combustion burners located at the entrance of the recovery boiler in the periods of solar steam supply , fed with the same fossil fuel of the gas turbine, at the cost of reducing the overall performance and solar participation, or, better still, with biological fuels obtained from biomass.
Los economizadores para calentamiento de líquido a las distintas presiones del ciclo, estarán dimensionados en cada caso de forma óptima desde el punto de vista técnico y económico, que normalmente conducirá a un sobredimensionamiento en la operación como ciclo combinado sin aporte de vapor solar. Con el fin de evitar que en estas condiciones se acerque excesivamente la temperatura del líquido a la de saturación, e incluso se pudieran producir vapoπzaciones en el cambiador, se deberán prever recirculaciones de líquido u otros sistems habituales de control de este fenómeo. En la condición de operación sin aporte de vapor solar, en la figura se han representado las curvas de absorción en los economizadores sin tener en cuenta las posibles recirculaciones requeπdas como normalmente se hace, dado que desde el punto de vista termodmámico ambas representaciones son totalmente equivalentes, y esta forma, que lógicamente coincide con la típica de un ciclo combinado de dos presiones, facilita la compresión del diagrama. La zona de recuperación de baja temperatura, incluyendo la generación del pequeño caudal de vapor para el desaireador, permite obtener un superior enfriamiento de los gases en la condición de operación con aportación de vapor solar, debido al hecho de disponer de un caudal superior de líquido a calentar en esta condición. En aquellos casos en que, por las características del combustible, no sea recomendable el enfriamiento de los gases hasta esta temperatura con tubos de acero y tampoco sea adecuado recurrir a mateπales especiales (tubos cerámicos, vidrio o teflon), sería factible realizar una pequeña toma de vapor en la zona de baja de la turbina con el fin de calentar el condensado hasta una temperatura mínima adecuada. Esta solución muy habitual, no afecta para nada al sistema descπto ni a su operación. Por último, y aunque el sistema se ha descrito en aplicación a centrales de generación eléctrica pura con ciclo combinado, independientemente de sus características básicas y potencia, existen aplicaciones de ciclos combinados en centrales de cogeneración de energía eléctrica con otro tipo de energía térmica (vapor para proceso, calefacción, etc) donde el empleo del sistema descrito supone igualmente importantes mejoras. Entre estas últimas aplicaciones, es importante resaltar en particular su empleo en centrales de generación eléctrica combinadas con procesos de desalinización de agua por sistemas multievaporativos, donde se emplea a este último fin la energía térmica de condesación del ciclo de vapor. Para ello, se adoptaría una presión de condensación del ciclo de vapor sin aporte de vapor solar, correspondiente prácticamente a la temperatura mínima requerida por el sistema de desalinización. El aporte de vapor solar adicional al ciclo combinado, según el procedimiento que se ha descrito, conduciría a una elevación de la presión de condensación del vapor, suficiente para establecer el gradiente térmico requerido para suministrar al proceso de desalinización la energía adicional existente en esta condición, incrementando por tanto la producción de agua desal inizada. Este esquema se adapta de forma especialmente favorable a la invención propuesta, por permitir mantener prácticamente constante el salto térmico en la turbina de vapor y reducir los límites de aumento de la presión superior por humedad en el escape de la tubina de vapor. una vez descrita suficientemente la naturaleza de la presente invención, así como algunas formas de llevarlo a la práctica, es preciso señalar que, en el conjunto y detalles de la misma, es posible introducir cambios de forma y disposición siempre y cuando dichas alteraciones no varíen sustancialmente las características de la invención que se reivindican a continuación. The economizers for liquid heating at the different pressures of the cycle, will be optimally sized in each case from a technical point of view and economical, which will normally lead to an oversize in the operation as a combined cycle without solar steam. In order to avoid that in these conditions the temperature of the liquid is approached excessively to that of saturation, and even vapπzaciones could occur in the changer, liquid recirculations or other usual systems of control of this phenomenon should be provided. In the operating condition without solar steam, the absorption curves in the economizers have been represented in the figure without taking into account the possible recirculations required as normally done, given that both representations are totally equivalent from the thermodynamic point of view , and this form, which logically coincides with the typical of a combined cycle of two pressures, facilitates the compression of the diagram. The low temperature recovery zone, including the generation of the small steam flow for the deaerator, allows for a higher cooling of the gases in the operating condition with solar steam, due to the fact that it has a higher liquid flow to heat in this condition. In those cases in which, due to the characteristics of the fuel, it is not advisable to cool the gases to this temperature with steel tubes and it is not appropriate to resort to special materials (ceramic tubes, glass or teflon), it would be feasible to take a small shot of steam in the low zone of the turbine in order to heat the condensate to a suitable minimum temperature. This very common solution does not affect the decutto system or its operation at all. Finally, and although the system has been described in application to pure power generation plants with combined cycle, regardless of their basic characteristics and power, there are combined cycle applications in cogeneration power plants with other types of thermal energy (steam for process, heating, etc.) where the use of the described system also implies important improvements. Among these latest applications, it is important to highlight in particular its use in power generation plants combined with water desalination processes by multi-evaporative systems, where the thermal energy of steam cycle condensation is used for the latter purpose. For this, a condensation pressure of the steam cycle without solar steam contribution would be adopted, corresponding practically to the minimum temperature required by the desalination system. The contribution of additional solar steam to the combined cycle, according to the procedure described above, would lead to an increase in the vapor condensation pressure, sufficient to establish the thermal gradient required to supply the desalination process with the additional energy existing in this condition. , thereby increasing the production of desalinated water. This scheme is adapted in a particularly favorable way to the proposed invention, because it allows to keep the thermal jump in the steam turbine practically constant and reduce the limits of increase of the upper pressure by humidity in the steam pipe exhaust. once the nature of the present invention has been sufficiently described, as well as some ways of putting it into practice, it should be noted that, in the set and details thereof, it is possible to introduce changes of form and arrangement as long as said alterations do not substantially vary the characteristics of the invention claimed below.

Claims

REIVINDICACIONES
1.- un procedimiento de mejora para centrales eléctricas de ciclo combinado con aporte de un caudal de vapor externo generado a partir de energía solar, caracterizado porque la presión superior del ciclo de vapor durante los períodos de operación con aporte de vapor solar es más alta que la óptima de diseño del ciclo básico correpondiente sin considerar el aporte de vapor solar y más alta asimismo que la presión superior de trabajo durante los períodos de operación sin aporte de vapor solar. 1.- an improvement procedure for combined cycle power plants with contribution of an external steam flow generated from solar energy, characterized in that the higher pressure of the steam cycle during periods of operation with solar steam input is higher that the optimal design of the corresponding basic cycle without considering the contribution of solar steam and also higher than the higher working pressure during periods of operation without solar steam.
2.- un procedimiento, de acuerdo con la reivindicación 1a, caracterizado porque el vapor de origen solar es saturado y se mezcla con el vapor saturado generado a la presión superior en la caldera de recuperación de los gases de escape de la turbina de gas, para ser sobrecalentado en dicha caldera. 2. A method according to claim 1a, characterized in that the steam of solar origin is saturated and mixed with the saturated steam generated at the upper pressure in the recovery boiler of the gas turbine exhaust gases, to be superheated in said boiler.
3.- Un procedimiento, de acuerdo con la reivindicación 1a, caracterizado porque, la turbina de vapor está dimensionada para el caudal de vapor nominal generado en la caldera de recuperación de los gases de escape de la turbina de gas, en ausencia de aporte de vapor solar, con la presión superior del ciclo de vapor correspondiente a esta condición, de tal forma que la admisión de un caudal de vapor mayor por la turbina de vapor durante los períodos de operación con aporte de vapor solar sea posible gracias al incremento de la presión superior del ciclo de vapor y, por tanto, de la presión en 'la entrada de la turbina de vapor, en esta otra condición. 3. A method according to claim 1, characterized in that the steam turbine is sized for the nominal steam flow generated in the recovery boiler of the gas turbine's exhaust gases, in the absence of input from solar steam, with the upper pressure of the steam cycle corresponding to this condition, in such a way that the admission of a higher steam flow through the steam turbine during periods of operation with solar steam input is possible thanks to the increase in the higher pressure of the steam cycle and, therefore, of the pressure at the steam turbine inlet, in this other condition.
4.- un procedimiento, de acuerdo con la reivindicación 1a, caracterizado porqυe el caudal de vapor de oπgen solar aportado a la presión superior del ciclo de vapor es variable en el tiempo, entre cero y un valor máximo, y dicha presión superior es asimismo variable, entre el valor correspondiente a la operación del ciclo combinado sin aporte de vapor solar y el valor máximo correspondiente al caudal máximo de vapor solar aportado. 4.- a procedure, according to the claim 1a, characterized in that the flow rate of solar oxygen vapor contributed to the upper pressure of the steam cycle is variable in time, between zero and a maximum value, and said higher pressure is also variable, between the value corresponding to the operation of the combined cycle without contribution of solar steam and the maximum value corresponding to the maximum flow of solar steam provided.
5.- un procedimiento de acυerdo con la reivindicación 4a, caracteπzado porqυe. al menos a pertir de un determinado caudal de vapor solar aportado, las válvulas de entrada de la turbina de vapor están totalmente abiertas y la presión superior del ciclo de vapor viene totalmente determinada por el equilibrio entre capacidad de paso de la turbina de vapor y la capacidad total de generación de vapor, variando dicha presión superior en función fundamentalmente de la vaπable potencia aportada a la caldera solar, para unas condiciones determinadas de operación de la turbina de gas. 5. A method according to claim 4, characterized by. at least depending on a given solar steam flow rate, the steam turbine inlet valves are fully open and the upper pressure of the steam cycle is determined entirely by the balance between the steam turbine's passing capacity and the total steam generation capacity, said higher pressure varying primarily as a function of the watchable power provided to the solar boiler, for certain operating conditions of the gas turbine.
6.- un procedimiento, de acuerdo con la reivindicación 1a, caracterizado porque el calor de condensación del vapor de escape de la turbina de vapor se emplea para desal ínización de agua, con caudal variable de agua desal mizada en función del caudal variable de aporte solar. 6. A method, according to claim 1a, characterized in that the condensation heat of the steam turbine exhaust steam is used for water desalination, with variable flow of desalinated water as a function of the variable supply flow solar.
7.- un procedimiento de mejora para centrales eléctπcas de ciclo combinado con aporte de un caudal de vapor externo generado a partir de energía solar, caracteπzado porque, para regulación, atenuación y compensación del efecto producido en el ciclo de vapor por los cambios de la aportación de vapor de oπgen solar, se dispone en la entrada del vaporizador de alta presión de la caldera de recuperación de los gases de escape de la turbina de gas de υn sistema específicamente diseñado de quemadores de postcombustión en vena de gas, que permiten regular la potencia generada por la. central, con independencia de las condiciones solares. 7.- an improvement procedure for combined cycle power plants with input of an external steam flow generated from solar energy, characterized because, for regulation, attenuation and compensation of the effect produced in the steam cycle by changes in the contribution of solar oπgen steam, is disposed at the entrance of the high pressure vaporizer of the recovery boiler of the exhaust gases of the Gas turbine of a system specifically designed for post-combustion burners in a gas vein, which allows the power generated by the power to be regulated. central, regardless of solar conditions.
8.- Un procedimiento, de acυerdo con la eivindicación 53, caracterizado porque el vaporizador de alta presión de la caldera de recuperación de los gases de escape de la turbina de gas se diseña con una inercia térmica pequeña, de tal forma que su capacidd de respuesta al control con postcombustión, tanto para el aumento como para la disminución de la generación de vapor, permita compensar adecuadamente las variaciones en el caudal de vapor saturado aportado por la caldera solar. 8. A method, according to claim 53, characterized in that the high pressure vaporizer of the gas boiler exhaust recovery boiler is designed with a small thermal inertia, such that its capacity of response to post-combustion control, both for the increase and for the decrease in steam generation, allows to adequately compensate for variations in the saturated steam flow rate provided by the solar boiler.
9.- Un procedimiento, de acuerdo con la reivindicación 7a, caracterizado porque los quemadores de postcombustión se alimentan con combustibles obtenidos a partir de biomasa (bioalcoholes, bioaceites, biogas, etc.). 9. A method according to claim 7a, characterized in that the post-combustion burners are fed with fuels obtained from biomass (bioalcohols, bio oils, biogas, etc.).
10.- Un procedimiento, de acuerdo con la reivindicación 9a, en el que el mismo combustible biológico utilizado en los quemadores de postcombustión para regulación de la potencia generada se utiliza también en unos quemadores situados a la entrada de la caldera de recuperación, para aportar los mayores requisitos de sobrecalentamiento en períodos con aporte de vapor solar, reduciendo o eliminando la necesidad de sobredimensionar el sobrecalentador de la caldera de recuperación. 10. A method according to claim 9a, wherein the same biological fuel used in post-combustion burners for regulating the power generated is also used in burners located at the entrance of the recovery boiler, to provide the highest requirements for overheating in periods with solar steam, reducing or eliminating the need to oversize the recovery boiler overheater.
PCT/ES1994/000102 1993-10-21 1994-10-21 Method for improving electric plants of combined cycle with solar support WO1995011371A1 (en)

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WO1997014887A1 (en) * 1995-10-17 1997-04-24 Siemens Aktiengesellschaft Energy-generation process and power station for carrying out the process
ES2174682A1 (en) * 1998-09-10 2002-11-01 Ormat Ind Ltd Technological update equipment to reduce the fosil fuel consumption of an energy generating center using solar incident radiation. (Machine-translation by Google Translate, not legally binding)
ES2279658A1 (en) * 2004-07-22 2007-08-16 Serled Consultores, S.L. Electricity generation using solar energy and thermal energy from biomass involves generating electricity from collected solar energy and thermal energy caused by combustion of biomass using water vapor cycle produced and supplied by boiler
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CN101956577A (en) * 2010-09-15 2011-01-26 刘建光 New energy moderate temperate water steam power generating system
CN101968041A (en) * 2010-09-29 2011-02-09 武汉凯迪工程技术研究总院有限公司 Solar power generation method and system taking biomass boiler as auxiliary heat source
CN102200103A (en) * 2010-03-26 2011-09-28 阿尔斯通技术有限公司 Method of operating an integrated solar combined cycle power plant and solar combined cycle power plant for carrying out the method
WO2011068880A3 (en) * 2009-12-01 2012-09-20 Areva Solar, Inc. Hybrid solar-thermal power plant and operating method
CN103147944A (en) * 2013-01-29 2013-06-12 华北电力大学 Two-section tower type solar thermal power generation system
CN103953402A (en) * 2014-04-11 2014-07-30 武汉凯迪工程技术研究总院有限公司 Solar energy and biomass energy combined power generation optimizing integrated system
CN104912757A (en) * 2015-06-10 2015-09-16 中国华电工程(集团)有限公司 Trough-type solar thermal and natural gas combined power generation system
CN104912607A (en) * 2015-06-10 2015-09-16 中国华电工程(集团)有限公司 Tower type solar optothermal and gas hybrid generation system
CN104912755A (en) * 2015-06-10 2015-09-16 中国华电工程(集团)有限公司 Fresnel type solar photo-thermal and natural gas combined power generating system
WO2015136163A1 (en) 2014-03-13 2015-09-17 Mini Green Power Facility for energy production from biomass and solar energy
CN106837717A (en) * 2017-02-03 2017-06-13 安徽鼎甲科技有限公司 A kind of photo-thermal power generation and biological energy complementary electricity generation system
CN107448920A (en) * 2017-08-16 2017-12-08 上海垒锦环境科技中心 Biomass, rubbish, sludge and the comprehensive generating system of coal mixed combustion
CN109653971A (en) * 2018-10-17 2019-04-19 中山市思源电器有限公司 A kind of solar energy assisted coal fired hybrid power plant

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WO1996031697A1 (en) * 1995-04-03 1996-10-10 Compañia Sevillana De Electricidad, S.A. System for the integration of solar energy in a conventional thermal power plant generating electric energy
WO1997014887A1 (en) * 1995-10-17 1997-04-24 Siemens Aktiengesellschaft Energy-generation process and power station for carrying out the process
ES2174682A1 (en) * 1998-09-10 2002-11-01 Ormat Ind Ltd Technological update equipment to reduce the fosil fuel consumption of an energy generating center using solar incident radiation. (Machine-translation by Google Translate, not legally binding)
ES2279658A1 (en) * 2004-07-22 2007-08-16 Serled Consultores, S.L. Electricity generation using solar energy and thermal energy from biomass involves generating electricity from collected solar energy and thermal energy caused by combustion of biomass using water vapor cycle produced and supplied by boiler
ES2312275A1 (en) * 2007-06-07 2009-02-16 Abengoa Solar New Technologies, S.A. Solar concentration plant for production of overheated vapor (Machine-translation by Google Translate, not legally binding)
WO2009106657A1 (en) 2008-02-25 2009-09-03 Sener Grupo De Ingenieria, S.A. Energy generating method using thermal cycles with high-pressure and moderate-temperature steam
US8904789B2 (en) 2008-02-25 2014-12-09 Sener Grupo De Ingenieria, S.A. Method for generating energy by means of thermal cycles with high pressure and moderate temperature steam
WO2011068880A3 (en) * 2009-12-01 2012-09-20 Areva Solar, Inc. Hybrid solar-thermal power plant and operating method
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AU2010326107B2 (en) * 2009-12-01 2016-02-25 Areva Solar, Inc. Utilizing steam and/or hot water generated using solar energy
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US8833051B2 (en) 2010-03-26 2014-09-16 Alstom Technology Ltd Method for operation of an integrated solar combined-cycle power station, and a solar combined-cycle power station for carrying out this method
WO2012034358A1 (en) * 2010-09-15 2012-03-22 Liu Jianguang Intermediate temperature steam power generation system with new energy source
CN101956577A (en) * 2010-09-15 2011-01-26 刘建光 New energy moderate temperate water steam power generating system
CN101968041A (en) * 2010-09-29 2011-02-09 武汉凯迪工程技术研究总院有限公司 Solar power generation method and system taking biomass boiler as auxiliary heat source
CN103147944A (en) * 2013-01-29 2013-06-12 华北电力大学 Two-section tower type solar thermal power generation system
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FR3018559A1 (en) * 2014-03-13 2015-09-18 Jean Riondel INSTALLATION FOR GENERATING ENERGY FROM BIOMASS AND SOLAR ENERGY
WO2015154585A1 (en) * 2014-04-11 2015-10-15 武汉凯迪工程技术研究总院有限公司 Optimized integrated system for solar-biomass hybrid electricity generation
CN103953402A (en) * 2014-04-11 2014-07-30 武汉凯迪工程技术研究总院有限公司 Solar energy and biomass energy combined power generation optimizing integrated system
CN104912607A (en) * 2015-06-10 2015-09-16 中国华电工程(集团)有限公司 Tower type solar optothermal and gas hybrid generation system
CN104912755A (en) * 2015-06-10 2015-09-16 中国华电工程(集团)有限公司 Fresnel type solar photo-thermal and natural gas combined power generating system
CN104912757A (en) * 2015-06-10 2015-09-16 中国华电工程(集团)有限公司 Trough-type solar thermal and natural gas combined power generation system
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CN107448920A (en) * 2017-08-16 2017-12-08 上海垒锦环境科技中心 Biomass, rubbish, sludge and the comprehensive generating system of coal mixed combustion
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