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EP4431803A1 - Générateur de vapeur et procédé de fonctionnement d'un générateur de vapeur - Google Patents

Générateur de vapeur et procédé de fonctionnement d'un générateur de vapeur Download PDF

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Publication number
EP4431803A1
EP4431803A1 EP24164099.4A EP24164099A EP4431803A1 EP 4431803 A1 EP4431803 A1 EP 4431803A1 EP 24164099 A EP24164099 A EP 24164099A EP 4431803 A1 EP4431803 A1 EP 4431803A1
Authority
EP
European Patent Office
Prior art keywords
liquid salt
liquid
steam
heat exchanger
storage tank
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.)
Pending
Application number
EP24164099.4A
Other languages
German (de)
English (en)
Inventor
Rüdiger Franck
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.)
Currenta GmbH and Co OHG
Original Assignee
Currenta GmbH and Co OHG
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Currenta GmbH and Co OHG filed Critical Currenta GmbH and Co OHG
Publication of EP4431803A1 publication Critical patent/EP4431803A1/fr
Pending legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B1/00—Methods of steam generation characterised by form of heating method
    • F22B1/02—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
    • F22B1/06—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers the heat carrier being molten; Use of molten metal, e.g. zinc, as heat transfer medium
    • 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
    • F01K13/00—General layout or general methods of operation of complete plants
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F22—STEAM GENERATION
    • F22B—METHODS OF STEAM GENERATION; STEAM BOILERS
    • F22B1/00—Methods of steam generation characterised by form of heating method
    • F22B1/02—Methods of steam generation characterised by form of heating method by exploitation of the heat content of hot heat carriers
    • F22B1/028—Steam generation using heat accumulators

Definitions

  • the invention relates to a steam generator and a method for operating such a steam generator, with the aid of which high-energy steam can be generated cost-effectively.
  • a solar thermal power plant in which a liquid salt can also be heated using electrodes operated with alternating current.
  • the heated liquid salt is fed to a steam generator, which uses the steam generated to feed a turbine to generate electrical energy for a power grid.
  • One embodiment relates to a steam generator for generating superheated high-pressure steam, with a storage tank for storing an electrically conductive cold liquid salt, a heating device for heating the cold liquid salt, wherein the heating device has electrodes that can be electrically connected to one another via the liquid salt and operated by an alternating voltage source or three-phase source, a storage tank for storing the warm liquid salt heated by the heating device and a heat exchanger arranged in a flow path of the liquid salt from the storage tank to the storage tank for preheating, evaporating and/or superheating a liquid, in particular water, within the heat exchanger to a high temperature level that is above a boiling point of the liquid.
  • the AC voltage source generates an alternating voltage that is characterized by the fact that the direction of the electric flow changes periodically, typically in a sinusoidal pattern with alternating positive and negative current directions. In contrast, the direction of the electric flow remains constant with direct current.
  • AC voltage sources can be generators, transformers and inverters in particular.
  • the three-phase source is a special type of AC voltage source that generates three separate AC voltages that are each 120 degrees out of phase. Three-phase sources can be generated, for example, by special generators that have several windings or by converting alternating current into three-phase current using three-phase converters.
  • the liquid salt can be present, for example, as a melt of a salt or as a melt of a salt mixture of at least two different salts, so that the liquid salt is electrically conductive due to the molten state.
  • the liquid salt is preferably essentially anhydrous, i.e. a water content in weight percent based on the total mass of the liquid salt is less than 1%, in particular less than 0.1%.
  • the vapor pressure of the liquid salt practically does not increase when heated to high temperatures below the decomposition temperature, which enables the process to be carried out in pressureless apparatus.
  • the liquid salt acts as an ohmic resistance or impedance, whereby the liquid salt is heated directly.
  • the liquid salt In contrast to indirect heating of the liquid salt, in which the liquid salt is indirectly heated by a heating element that is electrically insulated from the liquid salt and in particular powered by electrical energy, unnecessary power losses and time delays are avoided due to high currents at low voltage.
  • the heating output is therefore dependent on the applied voltage, the conductivity of the liquid salt and the design and arrangement of the electrodes. This opens up the possibility of influencing the voltage that can be applied to operate the electrodes through design specifications, since the liquid salt is part of the electrical circuit and creates an electrical connection between at least two electrodes.
  • the electrodes are electron conductors that interact with the liquid salt between the two electrodes in the interaction between the electrode and a corresponding counter electrode (anode - cathode).
  • the electrodes can be made of a conductive material, in particular metal, graphite or a conductive compound.
  • the liquid salt heated in the heating device can be fed directly into the heat exchanger or temporarily stored in the storage tank, so that it is possible to generate high-pressure steam almost simultaneously or to use the high-pressure steam stored in the storage tank at a later time.
  • the heating device for the high-output liquid salt can also be operated for a shorter time and the steam generator for a longer time. The costs of generating steam can therefore be kept low.
  • the heat exchanger can be supplied with warm liquid salt from the storage tank intermittently, so that the steam generator can provide an additional energy storage function with the aid of the storage tank.
  • This makes it possible to store more and more warm liquid salt in the storage tank during periods in which heating up the cold liquid salt in the heating device is cost-effective, so that there is enough warm liquid salt available for the heat exchanger during periods in which heating up the cold liquid salt in the heating device is not so cost-effective.
  • This makes it possible to operate the heating device during cost-effective periods and not to operate it during less cost-effective or cost-intensive periods without affecting the sufficient generation of steam in the heat exchanger.
  • the heating device can be oversized, whereby the oversized heating device does not lead to higher, but rather lower average operating costs.
  • the frequency of the power grid can be evened out even in the event of sudden fluctuations and the grid time can be kept more constant.
  • An oversupply of electrical power in the power grid can be identified by a higher actual grid frequency provided by the power grid compared to a nominal frequency, for example 50 Hz or 60 Hz.
  • An undersupply of electrical power in the power grid can be identified by a lower actual grid frequency provided by the power grid compared to the nominal frequency.
  • interventions in the supply of electrical power in the power grid are initiated, to which the steam generator can make a contribution.
  • at least one steam generator can have a noticeable influence on the regional or national power supply.
  • the heating device can in particular have a plurality of electrodes connected in parallel, so that a correspondingly high electrical power can be introduced into the liquid salt via a plurality of electrodes and used to heat the liquid salt. This allows an electrical current flow to be generated in a particularly large volume of the heating device, so that a correspondingly large volume of the liquid salt in the heating device can also be heated at the same time.
  • the liquid salt can be heated to a comparatively high temperature, which is above the evaporation temperature of many liquids used to generate steam, especially water.
  • the warm liquid salt is able to superheat the steam, so that the not only is all of the liquid fed to the heat exchanger completely evaporated, but the steam itself is also heated further.
  • the steam leaving the heat exchanger can have a temperature that is significantly above the boiling point. For example, this can prevent condensation of liquid as a result of heat losses occurring during the transport of the steam.
  • the steam can be superheated with the help of the warm liquid salt in the heat exchanger to such an extent that the steam meets certain specifications and/or standards for high-energy hot steam and/or high-pressure steam.
  • the equipment required and the associated costs for providing high-energy steam can therefore be kept low.
  • the liquid salt can be pumped in a circle.
  • the cold liquid salt can be pumped from the supply tank via the heating device into the storage tank and from the storage tank via the heat exchanger back into the supply tank.
  • the liquid salt is, for example, a solar salt or a eutectic mixture of NaNO 3 and KNO 3 .
  • the liquid salt can remain liquid and thermally stable over a wide temperature range with a high heat capacity.
  • a mass flow of the liquid and a quantity of heat of the warm liquid salt at the temperature at the outlet of the heat exchanger are adapted to one another in such a way that for a pressure p of the steam leaving the heat exchanger 5 bar ⁇ p ⁇ 200 bar, in particular 15 bar ⁇ p ⁇ 120 bar and preferably 30 bar ⁇ p ⁇ 60 bar and/or for a saturated steam pressure ps of the liquid in the heat exchanger 1.5 ⁇ ps/p ⁇ 20.0, in particular 2.0 ⁇ ps/p ⁇ 10.0 and preferably 3.0 ⁇ ps/p ⁇ 5.0 applies.
  • the superheated steam can be heated by the heat input of the liquid salt in the Heat exchangers can be very dry and can therefore be cost-effectively overheated to a very high temperature level.
  • the heating device is designed to heat the liquid salt to a temperature T above an intended evaporation temperature of the liquid, in particular 100°C ⁇ T ⁇ 560°C, preferably 170°C ⁇ T ⁇ 450°C and particularly preferably 250°C ⁇ T ⁇ 350°C.
  • a temperature T above an intended evaporation temperature of the liquid, in particular 100°C ⁇ T ⁇ 560°C, preferably 170°C ⁇ T ⁇ 450°C and particularly preferably 250°C ⁇ T ⁇ 350°C.
  • the electrodes of the heating device are particularly preferably connected to an alternating voltage source or three-phase source operated at medium voltage, the alternating voltage source or three-phase source providing a medium voltage U of 1 kV ⁇ U ⁇ 69 kV, in particular 10 kV ⁇ U ⁇ 50 kV and preferably 20 kV ⁇ U ⁇ 30 kV.
  • the medium voltage allows a high energy input into the liquid salt at low currents and fewer voltage changes. By using alternating voltage, electrolytic decomposition of the liquid salt can be avoided.
  • the liquid salt is a molten salt.
  • electrolytic decomposition can be avoided.
  • the electrodes can be operated from a power grid, whereby a generator that can be operated with the help of the superheated steam is provided for feeding the generated electrical energy into the power grid.
  • a generator that can be operated with the help of the superheated steam is provided for feeding the generated electrical energy into the power grid.
  • a closable valve is provided between the storage tank and the heat exchanger.
  • the valve can also assume intermediate positions, preferably essentially continuously, between a completely closed and a completely open position.
  • the mass flow of the liquid salt supplied to the heat exchanger can be adjusted as required and preferably independently of the mass flow of the liquid salt supplied to the heating device and/or discharged from the heating device. For example, this makes it possible to react to a change in the required mass flow of superheated steam.
  • a first pump for conveying the liquid salt is provided in a flow path from the supply tank to the storage tank and a second pump for conveying the liquid salt is provided in a flow path from the storage tank to the supply tank.
  • an expansion device in particular a turbine, and/or a pressure and/or heat consumer connected to a generator for generating electrical energy
  • the expansion device and/or the pressure and/or heat consumer is connected to the heat exchanger for the removal of superheated steam leaving the heat exchanger.
  • the energy content of the superheated steam in the form of pressure and/or heat can be used by corresponding consumers for various purposes, wherein the superheated steam can also be stored on the lower energy level can still be present as superheated steam.
  • the steam can therefore be fed sequentially to several consumers connected in series, which can be operated at the respective energy level of the superheated steam.
  • the superheated steam can first be fed to the turbine at a high energy level and then to the pressure and/or heat consumer at the lower energy level, in order to further utilize the energy content of the superheated steam that remains after the turbine has been operated at a high efficiency.
  • the superheated steam it is also possible for the superheated steam to first be fed to the pressure and/or heat consumer at a high energy level and then to the turbine at the lower energy level, in order to utilize the energy content of the superheated steam that remains to generate electrical energy.
  • the turbine and the pressure and/or heat consumer can be connected in parallel so that the superheated steam can be supplied at the same energy level, whereby in particular a distribution of the mass flow between the turbine and the pressure and/or heat consumer can be changed, preferably continuously, in order to be able to react quickly and easily to changing requirements.
  • a further embodiment relates to a method for operating a steam generator, which can be designed and developed as described above, in which in a first period of time only the liquid salt is heated, while evaporation of the liquid does not occur, and in a second period of time offset from the first period of time only preheating, evaporation and overheating of the liquid takes place, while heating of the liquid salt does not occur.
  • the method can be designed and developed, in particular as explained above with reference to the steam generator. By temporally decoupling the heating of the liquid salt and the use of the liquid salt in the heat exchanger to generate superheated steam, high-energy steam can be generated with cost-effective energy consumption, so that cost-effective generation of high-energy steam is possible.
  • the amount of heat and the energy content of the storage tank are increased simply by heating the cold liquid salt to a higher energy level, by continually increasing the mass of the warm liquid salt stored in the storage tank, without the warm liquid salt being required in the heat exchanger at this time.
  • Energy can be temporarily stored inexpensively, particularly if there is an oversupply in the power grid and/or the costs for the electrical energy supplied to the electrodes of the heating device are particularly low.
  • the second period only the liquid salt stored in the storage tank is used to evaporate and superheat the liquid in the heat exchanger, without cold liquid salt being heated up in the heating device at the same time.
  • the heating device and the heat exchanger can be operated simultaneously, or neither the heating device nor the heat exchanger, or either the heating device or the heat exchanger.
  • the load on a power grid by electrical consumers is lower in the first period than in the second period.
  • superheated steam leaving the heat exchanger is fed to a heat utilization, in particular in a pressure and/or heat consumer, and the superheated steam is present in a superheated state downstream of the heat utilization. Condensation of liquid in the pressure and/or heat consumer is thereby avoided.
  • the superheated steam can optionally be reused at the lower energy level present after the pressure and/or heat consumer.
  • superheated steam leaving the heat exchanger is fed to an expansion device, in particular a turbine, connected to a generator for generating electrical energy, and that the superheated steam is present in a superheated state downstream of the expansion device. Condensation of liquid in the turbine is thereby avoided.
  • the energy temporarily stored in the storage tank from the power grid can be converted into electricity by evaporating and superheating the liquid in the heat exchanger and using the superheated steam in the turbine and fed back into the power grid. The power grid can thus be stabilized.
  • the electrodes of the heating device are operated with alternating current. By using alternating current, electrolytic decomposition of the molten salt can be avoided.
  • the steam generator 10 shown can generate superheated steam 12, which can be used, for example, for pressure and/or heat consumers in an industrial plant and/or for power generation in a turbine connected to a generator.
  • the steam generator 10 has a storage tank 14 in which a cold liquid salt with a temperature of, for example, approximately 180°C is contained.
  • the cold liquid salt can be fed to a heating device 18 with the aid of a first pump 16.
  • the heating device 18 has two or more electrodes 20 that can be supplied with electrical energy from a power network 22.
  • the electrodes 20 are operated with alternating current at a medium voltage level, the circuit between the electrodes being closed by the liquid salt, which forms an electrical resistance but is electrically conductive.
  • the liquid salt can thus be heated directly to, for example, approximately 550°C.
  • the warm liquid salt leaving the heating device 18 can be fed to a storage tank 24 and temporarily stored.
  • the warm liquid salt from the storage tank 24 can optionally be fed to a heat exchanger 28 with the aid of a second pump 26, where the warm liquid salt can evaporate and superheat a liquid, in particular water, fed with the aid of a feed water pump 30.
  • the liquid salt cooled to approx. 180°C in the heat exchanger 28 by the heat exchange with the liquid can be fed back to the storage tank 14.
  • the heating device 18 it is possible in a first period of time when there is an oversupply of electrical power in the power grid 22 to use the heating device 18 to generate electrical energy in the form of To store thermal energy in the storage tank 24 and, in a second period of time when there is a shortage of electrical power in the power grid 22, to generate superheated steam with the aid of the heat exchanger 28, which can be converted into electricity in the turbine connected to the generator and fed back into the power grid 22.
  • the heating device 18 it can be provided that in the first period of time the heating device 18 is operated, but not the heat exchanger 28, and in the second period of time the heat exchanger 28 is operated, but not the heating device 18.
  • the liquid salt heated by a first heat flow 30 in the heating device 18 can have a comparatively high temperature T of, for example, 550°C.
  • T a comparatively high temperature
  • the warm liquid salt from the storage tank 24 is fed to the heat exchanger 28
  • the warm liquid salt can cool down along a second heat flow 32, releasing an amount of heat Q, and be conveyed into the storage tank 14 as cold liquid salt.
  • the liquid can heat up along a third heat flow 34.
  • the liquid is initially heated to the boiling point in a first region 36.
  • the liquid is completely evaporated within a second region 38 adjoining thereto.
  • Within a third region 40 adjoining the second region 38 the completely evaporated liquid is further heated and thereby superheated.
  • the relatively high temperature difference between the temperature achievable in the heating device 18 for the liquid salt and the boiling temperature of the liquid in the heat exchanger can be exploited in order to obtain a high-energy and particularly dry high-pressure steam.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Sustainable Energy (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Engine Equipment That Uses Special Cycles (AREA)
EP24164099.4A 2023-03-16 2024-03-18 Générateur de vapeur et procédé de fonctionnement d'un générateur de vapeur Pending EP4431803A1 (fr)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP23162209.3A EP4431802A1 (fr) 2023-03-16 2023-03-16 Générateur de vapeur et procédé de fonctionnement d'un générateur de vapeur

Publications (1)

Publication Number Publication Date
EP4431803A1 true EP4431803A1 (fr) 2024-09-18

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EP23162209.3A Withdrawn EP4431802A1 (fr) 2023-03-16 2023-03-16 Générateur de vapeur et procédé de fonctionnement d'un générateur de vapeur
EP24164099.4A Pending EP4431803A1 (fr) 2023-03-16 2024-03-18 Générateur de vapeur et procédé de fonctionnement d'un générateur de vapeur

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EP23162209.3A Withdrawn EP4431802A1 (fr) 2023-03-16 2023-03-16 Générateur de vapeur et procédé de fonctionnement d'un générateur de vapeur

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Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2574784A2 (fr) 2011-09-29 2013-04-03 Pratt & Whitney Rocketdyne Inc. Système d'énergie solaire et procédé associé
US20170370250A1 (en) 2014-12-31 2017-12-28 Shenzhen Enesoon Science & Technology Co., Ltd. Combined energy supply system of wind, photovoltaic, solar thermal power and medium-based heat storage
CN108533467A (zh) 2018-02-26 2018-09-14 华北电力大学 一种功率调控的槽式、塔式光热与光伏可储热发电系统
WO2019094921A1 (fr) 2017-11-13 2019-05-16 Chromalox, Inc. Réchauffeur de sel fondu à moyenne tension et système d'accumulation d'énergie thermique à sel fondu comprenant celui-ci

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2574784A2 (fr) 2011-09-29 2013-04-03 Pratt & Whitney Rocketdyne Inc. Système d'énergie solaire et procédé associé
US20170370250A1 (en) 2014-12-31 2017-12-28 Shenzhen Enesoon Science & Technology Co., Ltd. Combined energy supply system of wind, photovoltaic, solar thermal power and medium-based heat storage
WO2019094921A1 (fr) 2017-11-13 2019-05-16 Chromalox, Inc. Réchauffeur de sel fondu à moyenne tension et système d'accumulation d'énergie thermique à sel fondu comprenant celui-ci
CN108533467A (zh) 2018-02-26 2018-09-14 华北电力大学 一种功率调控的槽式、塔式光热与光伏可储热发电系统

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