WO2012175763A1 - Stockage d'énergie thermique au moyen d'un condensateur-générateur de vapeur réversible - Google Patents

Stockage d'énergie thermique au moyen d'un condensateur-générateur de vapeur réversible Download PDF

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Publication number
WO2012175763A1
WO2012175763A1 PCT/ES2012/000155 ES2012000155W WO2012175763A1 WO 2012175763 A1 WO2012175763 A1 WO 2012175763A1 ES 2012000155 W ES2012000155 W ES 2012000155W WO 2012175763 A1 WO2012175763 A1 WO 2012175763A1
Authority
WO
WIPO (PCT)
Prior art keywords
exchanger
tank
steam
reversible
fluid
Prior art date
Application number
PCT/ES2012/000155
Other languages
English (en)
Spanish (es)
Inventor
José Maria MARTÍNEZ-VAL PEÑALOSA
Manuel VALDÉS DEL FRESNO
Alberto Abanades Velasco
Rafael Rubén AMENGUAL MATAS
Mireia Piera Carrete
Mária José MONTES PITA
Antonio Rovira De Antonio
Alberto RAMOS MILLÍAN
Javier MUÑOZ ANTÓN
Rubén ABBAS CÁMARA
Original Assignee
Universidad Politécnica de Madrid
Universidad Nacional De Educación A Distancia
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 Universidad Politécnica de Madrid, Universidad Nacional De Educación A Distancia filed Critical Universidad Politécnica de Madrid
Publication of WO2012175763A1 publication Critical patent/WO2012175763A1/fr

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01K—STEAM ENGINE PLANTS; STEAM ACCUMULATORS; ENGINE PLANTS NOT OTHERWISE PROVIDED FOR; ENGINES USING SPECIAL WORKING FLUIDS OR CYCLES
    • F01K9/00—Plants characterised by condensers arranged or modified to co-operate with the engines
    • 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
    • F01K3/00—Plants characterised by the use of steam or heat accumulators, or intermediate steam heaters, therein
    • F01K3/006—Accumulators and steam compressors
    • 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
    • F01K3/00—Plants characterised by the use of steam or heat accumulators, or intermediate steam heaters, therein
    • F01K3/12—Plants characterised by the use of steam or heat accumulators, or intermediate steam heaters, therein having two or more accumulators

Definitions

  • the invention falls within the field of thermal engineering, and more specifically in installations where a high enthalpy steam is generated by any means, and said steam cannot be used in its entirety at any given time, so It has to relieve the atmosphere, if it cannot be stored.
  • An important case of this type is that of thermo-solar power plants, whether they are intended for electricity generation or direct thermal uses, typically of an industrial type.
  • the problem that is specifically to be solved is the storage of thermal energy from steam (mainly water vapor), and the thermal route to be proposed passes through the condensation of high pressure steam, by thermal transfer to a secondary fluid that is going to acquire at the condenser outlet a temperature not too far from that of water condensation, which occurs on the primary side of the condenser.
  • steam mainly water vapor
  • thermodynamically differentiated field such as subcooled, biphasic, and superheated steam
  • the invention consists in structuring a steam generation plant, for whatever use, including a central thermal storage system comprising:
  • a drum for the separation of saturated steam with three possible alternatives of exit, which correspond to: the recirculation of the liquid; to the steam duct towards its application or purpose; and to the steam duct towards a specific, reversible flow exchanger; - said heat exchanger, reversible flow both in its primary and secondary circuit, acting as a condenser when the primary fluid has a downward path, or acting as a steam generator when the primary fluid goes upward, having a structurally arranged vertical housing and tubes, the trunk tubes being conical, with the mouth of smaller diameter below, and said tubes going from a lower base plate to an upper base plate, and the primary fluid being the one circulating inside the tubes;
  • a secondary fluid subsystem of said reversible exchanger consisting of two storage tanks of the thermal fluid used, this fluid selected from oil and molten salts, or another substance that is liquid at the operating temperature level set at each
  • the tanks are connected by a conduit or pipe that crosses the reversible exchanger, one of them always acting as a low temperature tank, and another as a high temperature tank, with the secondary fluid from the low to high tank when the exchanger it acts as a condenser, and the secondary fluid from the tank goes from high to low when the exchanger acts as a steam generator;
  • the secondary fluid selected from molten salt, industrial oil or any other substance stable as a liquid at operating temperatures, moving from the outside of the tubes, between them and the housing, always predominantly vertical; an evacuation conduit from the separation drum, through the reversible exchanger primary circuit, to the condensate tank at high pressure and high temperature, this conduit being provided with a valve that is only open when the exchanger acts as a condenser;
  • a condensate evacuation pump in said evacuation duct which stimulates the rate of evacuated fluid, and maintains the level of the liquid free surface, in said reversible exchanger, at the height of the lower base plate of the exchanger, when it acts as condenser;
  • a vapor replacement duct which takes liquid from the condensate tank, injects it into the primary circuit of the reversible exchanger, which acts in the steam generator mode, and from which it emerges into the ordinary uses of the steam in the plant, this duct being provided with a valve that is only open when the exchanger acts as a steam generator; - an injection pump from the condensate tank to the primary circuit of the reversible exchanger, which maintains the level of the liquid-free surface, in the primary circuit of said exchanger, at the height of the upper base plate of the exchanger, when it It acts as a steam generator.
  • the drainage circuit is opened that diverts part or all of the steam produced to the primary circuit of the reversible heat exchanger, which currently acts as a condenser.
  • the entire surface of the frustoconical tubes inside which condensation occurs must be practically discovered of condensed liquid, since this is a thermal resistance for heat transfer that involves condensation.
  • the surface of the condensed liquid is carried and maintained just at the height, or a few centimeters below, of the bottom base plate of the exchanger, which is monitored with various techniques, both thermoelectric and electro-optical, as visual (in a bypass capillary with transparent cover slit).
  • An essential element for maintaining the level is the pump that drives the condensate from the base of the condenser to the pressure vessel of the condensate. If the condensed liquid accumulates in the condenser because it does not evacuate quickly enough, the level of liquid in the condenser would rise, cover part of the thermo-transfer surface and make condensation difficult. Therefore, if the free surface of the liquid rises above the lower base plate, the condensate extraction pump must act with more power, extracting more liquid flow, and lowering the level of the free surface; and reducing the suction power in the opposite case, extracting less liquid flow when the free surface falls below its set point, which is the lower base plate.
  • the pressure of said reservoir can be relaxed by partially opening the relief valve that connects it to the main condensate tank, which is at or near atmospheric pressure.
  • the heat recovered in that phase change is captured by the secondary fluid, which acts as a refrigerant, reaching a very high temperature, substantially 10 ° C below the fluid condensation temperature primary, and said secondary fluid passes from the low temperature tank, or cold tank, to the high temperature tank, or hot tank, (by actuating the cold tank pump), absorbing the heat released by the primary fluid in its condensation; leaving the primary fluid condensed at pressure and temperature equal to those of the primary steam, or somewhat lower, with a reduction of up to 5% in value relative to the pressure and temperature of the steam.
  • thermal storage is truly done in the oil or molten salt, although the condensed primary fluid is kept at pressure and temperature as high as possible and cost effective, to make steam generation easier, when it is demanded. in quantity greater than what the plant can give at that time, so it has to resort to stored thermal energy.
  • the injection pump is activated from the condensate tank to the primary circuit of the exchanger and the primary fluid circulates from the inside from bottom to top, always through inside the truncated conical tubes; and the criterion that the liquid-free surface is above the upper base plate is prescribed, which is monitored, by thermoelectric, or electro-optical or visual procedures. It is crucial here the role of said liquid injection pump from the high pressure condensate tank, which is given greater pumping power if it is desired to level up the liquid free surface, or otherwise, if desired that the level goes down, to stabilize in your reference, which is the upper base plate.
  • the discharge of secondary fluid from the hot tank to the lower temperature tank is activated, passing through the secondary circuit of the exchanger, activating the discharge pump of said hot tank.
  • thermocouples it is advisable to detect the appropriate level of protection against the boiling crisis, by applying active thermocouples to determine the local film coefficients at various heights, which will be very high, above 10,000 W / (m 2 K) if it is in the nucleated boiling regime, falling to 1,000 W / (m 2 K) or less if that surface is bathed only by dry steam.
  • the steam separates from the inner surface of the tubes, which is where their bubbles appear, which are enlarged as they rise in the breast of the liquid If it occurs in excess, the free surface of the liquid will descend, which can cause serious deterioration of the tubes in its exposed part.
  • the liquid injection pump is available from the condensate tank at high pressure, which is given greater pumping power if it is desired to level up the liquid free surface. During this operation, a high fraction of the heat stored in the hot tank is recovered, since from this it passes to the cold, yielding the heat necessary for the boiling of the primary liquid, whose vapor must be provided from the thermal storage.
  • the secondary fluid be it molten salt, industrial oil or any other substance, moves through the outside of the tubes, between them and the housing; and always moves in countercurrent.
  • the condensation function the primary descends and the secondary ascends; and the opposite in boiling.
  • Figure 1 shows the scheme of a steam plant, in this case to be used for expansion in a turbine, and to produce electricity. It is possibly the best example to demonstrate the parts and functionality of a thermal storage system.
  • Figure 2 shows the scheme of the vertical straight section of a reversible exchanger, which is the central element of the invention.
  • Figure 3 shows the straight cross section of the reversible exchanger, at the mouth level, distinguishing the lateral reinforcement crossings that should be placed between tubes, from the central tube, to maintain its geometry despite the pressure differences between the primary fluids and secondary.
  • Trunk tube inside which the primary fluid moves.
  • Lower base plate which closes spaces 55, and is welded to the bottom mouths of tubes 57.
  • Instruments for identifying the free surface of the liquid in the condensation which are monitors or meters of that level.
  • Instruments for identifying the free surface of the liquid in the boil which are monitors or meters of that level.
  • the invention has to be framed in a steam generation plant for a useful purpose, such as the generation of electricity, which is the case presented in Figure 1, and which brings together all the elements to explain the invention clearly, starting with note that the invention itself is the thermal storage system consisting of:
  • the reversible exchanger 17 which is properly the component specifically designed for this invention, and which is described below with the required detail. Its primary fluid is the vapor that reaches it to condense, or that is generated within it when it operates in the generation mode.
  • the enthalpy of the available saturated steam is achieved in two ways: the condensate of the primary fluid itself, which is kept at high pressure and temperature; and the heated secondary fluid, which is stored in the high T tank.
  • the excess steam of the drum 10 is condensed practically at the pressure that it has, thanks to the secondary fluid, and to the heat transfer carried out in the exchanger.
  • the secondary fluid passes from the low temperature tank, or cold tank, to the high temperature tank, or hot tank, absorbing the heat released by the primary fluid in its condensation.
  • the generation mode is activated, and the contents of the hot tank, 19, are discharged through the circuit 20, which has as main part the secondary of the exchanger 17, to arrive, cooled , to the low T storage tank, 18.
  • heat is transferred to the liquid injected into the primary of the exchanger 7 from the high pressure condensate tank, which is where the primary fluid is collected in the condensation mode.
  • the reversible exchanger 17 corresponds to a general type of casing and tubes, but with a special configuration, deduced from the functions to be fulfilled.
  • the level monitors, 66 and 67 respectively near or slightly below the lower base plate (58) for condensation mode, and near or slightly above the upper base plate (59) for the boiling mode
  • These level meters can be of the active thermocouple type, which measure the value of the film coefficient, which is really the variable to be monitored, since what has to be avoided, particularly in boiling, is that the appearance of a film Dry steam on the contact surface greatly reduces the value of that coefficient, and that greatly impairs heat transfer and efficiency in the process is lost; although it should be noted that in this case, in which the heat input comes from a fluid, the secondary one, whose temperature is given, the "dry out" phenomenon feared in the nuclear fuel pods in the LWR reactors cannot occur, because in the reactors the power generated within the fuel must be extracted and the temperature is not limited.
  • the value of h 2 ' ⁇ which is the thermal resistance of the secondary film will be the largest of the three addends of the right member in the equation previous, that defined U "1 , and therefore U. That means that the value U will be close to ah 2 , but less than him.
  • the value of U must be made as high as possible, because it intervenes in the determination of the size of the exchanger 17, since it is conditioned to the heat transfer area A which is defined as a function of the height H between the two base plates, the number of truncated conical tubes, N, and the upper diameters D s and lower D ⁇ of said tubes, being
  • m is defined as a function of the condensation temperature of the primary T c , that of the secondary fluid in the high T 2a tank and that of the secondary fluid in the low T 2b tank
  • the thermal power Q meets the energy balance in the secondary fluid, depending on its mass flow m 2 and the specific heat C 2 of the secondary fluid
  • the boiling temperature of the primary T e will be less than T 2b , in the same way as in the condensation mode, the temperature T c is above T 2a . This leads to the loss of exergy due to the process of loading and unloading storage can be characterized by
  • m 2 is essential to reduce the loss of exergy; but it must be taken into account that this value also influences the size of the exchanger, particularly in its straight section, which is the sum of the straight section of the tubes through which the primary circulates, plus the straight section of the secondary S 2 .
  • the latter is linked to am 2 by the equation in which the density of the secondary p 2 and its velocity v 2 intervene
  • the option of boosting the secondary with a v 2 involves the problem of a strong loss of manometric load, and therefore high pumping power, so that the particular realization of an exchanger will have to be done by adding some optimization criteria, or by performing a Cost-benefit analysis between investment cost and operating cost, which escapes the scope of a patent. It is, however, relevant for the design to take into account that the film coefficient h 2 is not uniform, but depends on the hydraulic conditions at each point, in particular the speed.
  • r is the ratio between outside and inside diameters of the tank.
  • the admissible ⁇ is less than usual at room temperature, since the elastic period is shortened and the risk of creep approaches, if Pi is high, close to 10 MPa, for example, the ratio ⁇ / ⁇ Allowable is low, around 6.
  • the thickness of the tank must be greater than 9% of the inside diameter. If the wall of the tank is bounded at a thickness of 10 cm, the inner diameter would be approximately 1 meter. This means that the exchanger must be slender, which is a well known reality.
  • An emblematic case is that of the PWR nuclear reactor steam generators, in which the pressure is around 7 MPa (and they have no other function, nor are they reversible).

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Engine Equipment That Uses Special Cycles (AREA)

Abstract

L'invention concerne un système de stockage d'énergie thermique dans des installations qui produisent de la vapeur, généralement à haute ou très haute pression, en fonction de la condensation de la vapeur à haute pression et à haute température, le second fluide étant un milieu fluide choisi parmi le sel fondu, l'acide thermique ou un autre liquide aux propriétés stables dans ces conditions qui, pendant le fonctionnement du réservoir, passe d'une température basse à une température élevée. Ainsi, pratiquement la totalité de la chaleur de condensation est extraite par ledit moyen, qui est récupéré, bien qu'à une température quelque peu inférieure, quand l'échangeur fonctionne comme générateur de vapeur, ledit échangeur ayant des tubes verticaux tronconiques pour améliorer ses performances.
PCT/ES2012/000155 2011-06-22 2012-06-05 Stockage d'énergie thermique au moyen d'un condensateur-générateur de vapeur réversible WO2012175763A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
ESP201100715 2011-06-22
ES201100715A ES2364311B2 (es) 2011-06-22 2011-06-22 Almacenamiento de energía térmica mediante condensador-generador de vapor reversible.

Publications (1)

Publication Number Publication Date
WO2012175763A1 true WO2012175763A1 (fr) 2012-12-27

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Application Number Title Priority Date Filing Date
PCT/ES2012/000155 WO2012175763A1 (fr) 2011-06-22 2012-06-05 Stockage d'énergie thermique au moyen d'un condensateur-générateur de vapeur réversible

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ES (1) ES2364311B2 (fr)
WO (1) WO2012175763A1 (fr)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4089744A (en) * 1976-11-03 1978-05-16 Exxon Research & Engineering Co. Thermal energy storage by means of reversible heat pumping
EP2157317A2 (fr) * 2008-08-19 2010-02-24 ABB Research LTD Système de stockage d'énergie thermoélectrique et procédé de stockage d'énergie thermoélectrique
US20110100611A1 (en) * 2008-07-16 2011-05-05 Abb Research Ltd Thermoelectric energy storage system and method for storing thermoelectric energy

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4089744A (en) * 1976-11-03 1978-05-16 Exxon Research & Engineering Co. Thermal energy storage by means of reversible heat pumping
US20110100611A1 (en) * 2008-07-16 2011-05-05 Abb Research Ltd Thermoelectric energy storage system and method for storing thermoelectric energy
EP2157317A2 (fr) * 2008-08-19 2010-02-24 ABB Research LTD Système de stockage d'énergie thermoélectrique et procédé de stockage d'énergie thermoélectrique

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ES2364311B2 (es) 2011-12-26
ES2364311A1 (es) 2011-08-31

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