EP3511534A1 - Steam power-plant and method for operating same - Google Patents

Abstract

The invention relates to a steam power plant, such as brown coal or hard coal power plant, with a water-steam cycle (1), to a generator (7) for the electrical power generation connected turbine assembly (4) and a thermal energy storage part (5) a heat storage unit containing a heat storage medium (50), a heat input device (6) and an attached to the water-steam circuit (1) or a flue gas discharge device (51). A high degree of flexibility is achieved in that the heat coupling device (60) has an electrical heating device (60) which can be acted upon by an electrical energy supply device (61) with electrical energy generated by the generator (7) under control or regulation by means of a process control (FIG .1).

Description

The invention relates to a steam power plant, such as brown coal or hard coal power plant, with a water-steam cycle, a generator connected to a generator for electrical energy turbine assembly and a thermal energy storage part containing a heat storage medium heat storage unit, a heat input device and a to the Has water-steam circuit or a flue gas path connected discharge device, and to a method for operating such a steam power plant.

A steam power plant and a method of this kind are in the DE 10 2011 100 517 A1 specified. Here, a control system for adapting the power of a steam turbine to a changed load in the context of a primary control is provided with a heat storage. The heat storage takes with reduced load and thus increased amount of steam tapped from the steam turbine heat from the tapped steam and are at increased load and thus correspondingly reduced amount of the steam turbine tapped steam heat to a steam / feed water circuit, which supplies the steam turbine. In addition, it is conceivable to heat the heat accumulator separately, unless waste heat is available, for. B also electrically in times of a Stromüberangebots. The electrical heating of the heat accumulator does not affect the primary control itself. Overall, the control system is based on the variation of the tapped steam quantity in connection with the intermediate storage of heat. The change in the power plant steam turbine power over the amount of steam drawn off gives a limited margin for power adjustment. Also, the structural design of the control system requires no small effort.

In the DE 10 2012 204 081 A1 discloses an energy storage power plant for electric power generation, which is suitable for the transfer of electrical energy into thermal energy, wherein the thermal energy can be stored in a buffer until the time of need in at least two thermal storage and, if necessary, to increase the energy content of water in a water cycle can be retrieved. In this case, a thermal storage for storing sensible heat and a thermal storage for storing latent heat is provided. This energy storage power plant and the method used thereby takes advantage of the fact that electrical energy, which can be acquired relatively inexpensively in times of surplus production of electrical energy, can be converted into thermal energy, which is suitably stored in the energy storage power plant, and if required again the power generation can be supplied. To charge the two thermal storage electrical energy must be removed from an electrical supply circuit, so as the public power grid, if necessary, which is then converted by means of one or more suitable conversion devices into thermal energy. With these measures is a quick flexible adaptation to changed Network loads to practically impossible extent to achieve, because in particular during the thermal discharge, a startup of the inert heat-power process is necessary, whereby no dynamic operation can be achieved.

The DE 10 2012 003 267 A1 shows various heat storage with electric heaters, which can also be used in connection with a steam power plant. By means of the heat accumulator for a short time high surplus electricity quantities can be stored in order to be able to deliver them again at a later time over a longer period of time. Even such arrangements are inadequate to meet high flexibility requirements when adapting to requested services.

In the mentioned DE 10 2012 204 081 A1 and DE 10 2012 003 267 A1 Energy storage power plants are presented, which are basically based on the fact that electrical energy from the public network is used during the loading to heat thermal energy storage. During discharge, the stored thermal energy is used to generate a thermal power process (in the DE 10 2012 204 081 A1 a water-steam process; in the DE 10 2012 003 267 A1 a specified, only abstractly described by the Carnot efficiency process) and thus again to feed electrical energy into the public network. It is basically about newly built energy storage power plants that transmit electrical energy from / in the public / n net, and not to the upgrading of existing coal-fired power plants. The current during the discharge of energy storage power plants heat processes are limited by thermal inertia of the components, the process is operated only during the discharge phase.

In the CH 196 041 A an integration of heat storage is shown in steam power plants, wherein a storage of steam is called in a Ruths memory.

Furthermore, a steam power plant and a method of the DE 10 2011 078 193 A1 known. In this steam power plant, a higher energy steam is tapped on a turbine assembly and admixed with a low energy steam tapped on the turbine assembly. The vapor mixture is fed to a preheater, in particular a high pressure preheater of the steam power plant for heating a feedwater flowing through the preheater. The controlled or controlled admixing of the higher-energy steam to the low-energy steam is intended to bring about a rapid power change in the steam power plant.

At one in the WO 2013/000838 A2 presented another steam power plant and method for its operation are supplied for auxiliary power of the steam power plant when driving on or off the same with auxiliary steam from an auxiliary steam generator for rapid or temporary increase in power. In a power demand to the steam power plant of the auxiliary steam is fed into the water-steam cycle of the steam power plant, thereby supplying a turbine of the steam power plant with additional steam and the power of the steam power plant immediately, quickly or temporarily increased. In the DE 10 2012 215 569 A1 is proposed for rapid change in active power of steam power plants, in the water-steam working cycle branch off a steam portion as process energy for a CO ₂ -Abschalteeinrichtung, wherein in the branch or a subsequent steam extraction line an adjustable valve for rapid increase and reduction of the branched vapor content is provided.

Other steam power plants and methods for operating the same are in the DE 10 2011 078 205 A1 , the WO 2009/100881 A2 and the DE 10 2015 109 898 A1 shown.

In the course of the increasing expansion of renewable energy, the increase in flexibility of conventionally operated types of power plants, in particular steam power plants such as brown coal or coal-fired power plants, is becoming increasingly important.

Based on such requirements, the present invention has the object, a steam power plant, especially brown coal or hard coal power plant, and a method for its operation in such a way that the most efficient increase in flexibility is achieved.

This object is achieved by a steam power plant with the features of claim 1. In this case, it is provided that the heat coupling device has an electrical heating device, which can be acted upon by an electrical energy supply device with the electrical energy generated by the generator and at the output side removed therefrom by means of a process control.

With regard to the operation, the object is achieved by a method having the features of claim 5, wherein it is provided that the heat energy supplied to the thermal energy storage part is generated by means of an electrical heating device, wherein the warm-up device supplied electrical power of the electric power generated by the steam power plant on the output side is removed from the generator.

Investigations by the inventors have proved to be a promising solution to meet the increasing flexibility requirements for brown coal and hard coal power plants (coal power plants), that for the integration of thermal energy storage in the power plant process and their heating by the electrical output at the output of the generator in Depending on the requested, to be fed into the power grid electrical power is advantageous. This is made possible by the temporal decoupling of thermal energy and electrically generated work on the turbine assembly, d. H. to the integrated into the water-steam cycle steam turbines, increased minimum load decreases and significantly improved load gradients compared to conventionally operated coal power plants. Suitable integration sites for coupling and decoupling thermal energy into and out of the thermal storage system have found advantageous in the water-steam cycle, but also in the flue gas path of the steam generator.

When load reduction, ie reduced feed of electrical power into the power grid, so the thermal storage system with the energy storage more electric power supplied via the warm-up device, while load increase, so increased power supply to the power grid, the thermal storage system with the energy storage correspondingly less electrical power is supplied, wherein the control or regulation of the power distribution, in particular also the operation of the warm-up, takes place via the process control. During discharge (at a time of high electrical demand in the grid), the coal-fired power plant can provide very fast electrical power because it has not been shut down but is still running and thus a start of the sluggish system (warm / cold start) is bypassed. In addition, the electrical heat stored during loading allows - depending on the place of integration - an electrical power increase during unloading, savings of coal and / or a power plant internal thermal management (auxiliary steam or the like.).

In this case, by the extension of the thermal storage system by the electrical heating device, d. H. a high-performance electric heater, a high increase in flexibility in load subsidence, especially minimum load reduction, and increases load and dynamics achieved, resulting in high efficiency and as a further advantage at most low integration effects of thermal energy storage in the power plant process and thus have significant benefits for retrofitting existing Coal power plants result. The integration of the electrically heated heat accumulator thus allows a mode of operation of the coal power plant under constant operating conditions, which also results in benefits in life and efficiency. The necessary flexibility is provided by utilizing the electrically heated heat storage and by not shutting down the coal power plant.

In this case, the design that the electrical heating device is designed as a resistance heating device or as an inductive heating device, can achieve high-performance and efficient operations with high efficiencies.

Various advantageous thermal storage systems that meet high capacity and performance requirements are obtained by providing the thermal energy storage portion with a Ruths storage, a solid storage, or a molten salt storage.

Advantageous integration locations, which enable a high minimum load reduction and at the same time in the decoupling of the thermal energy from the storage system a comparable increase in power of the steam power plant when coupling the thermal energy into the thermal storage system, resulting from the fact that the unloading in a steam generator section, in particular on a high-pressure preheater , or in a feedwater part, in particular to a low-pressure preheater, is connected. These integration sites of the storage system allow with a high efficiency both an efficient reduction and increase of the electric power provided by the steam power plant for external consumers and thus significant increases in flexibility for load reduction or load increase. In addition, the integration sites mentioned allow a low-feedback integration of the thermal storage system in the complex power plant process and thus give no or negligible effects on the operational limits of central power plant components, such as steam, turbines and the like. The integration sites provide solutions that result in only relatively small shifts in operating conditions (eg, pressure, temperature) in the power plant process, thus ensuring extended operational availability while allowing for high flexibility gains.

Corresponding advantages result in the method in that the heat energy in the discharge process in a steam generating section, in particular in a high-pressure preheater, and in a feedwater part, in particular a low-pressure preheater, the water-steam cycle is supplied.

Other advantages of operating the steam power plant are that by the discharge process compared to a normal load additional electrical power is delivered by the discharge of the heat energy in the Water-steam cycle an increased steam mass flow by reducing the Anzapfdampfmassenstroms and thus in an in this turbine assembly, an increased volume flow is generated.

The measures also contribute to an advantageous mode of operation in that the loading processes and the unloading processes are controlled or regulated by a process controller as a function of predetermined and / or predefinable process parameters, wherein superordinate control or controlled variables can be incorporated.

Fig. 1

zeigt ein Prozessschema eines Wasser-Dampf-Kreislaufs eines Dampfkraftwerks mit einem eingebundenen thermischen Speichersystem.

The invention will be explained in more detail by means of embodiments with reference to the drawing.

Fig. 1

shows a process diagram of a water-steam cycle of a steam power plant with an integrated thermal storage system.

Fig. 1 shows a schematic representation of a water-steam cycle 1 of a steam power plant, such as in particular a brown coal or coal power plant, with arranged therein essential process components. In this case, a thermal energy storage system with a thermal energy storage part 5 is connected to the water-steam cycle 1. As essential process sections, the water-steam cycle 1 comprises, as usual, a feedwater part 2, a steam generator section 3 following in the process flow, and a steam turbine arrangement 4 for driving a generator 7 for electrical power generation.

The feedwater part 2 is provided on the input side with a capacitor 21 connected to the output side of the turbine arrangement 4 and further comprises a condensate pump 22 and low-pressure preheater 23, a feedwater tank 20 and a feedwater pump 24 for providing the feedwater for the steam generator section 3.

In the steam generator section 3, high pressure preheater 30, a preheater 31, an evaporator 32, and a superheater 33 are arranged downstream of the process scheme to generate high pressure steam for the turbine assembly 4.

With regard to the process sequence, the turbine arrangement 4 comprises on the input side a high-pressure turbine 40, a subsequent medium-pressure turbine 41 and an output-side low-pressure turbine 42. Between the high-pressure turbine 40 and the medium-pressure turbine 41, a reheater 43 for the process steam is arranged. The turbine assembly 4, which may be structurally designed differently and provided with different tapping points, as known per se, is driven in rotation by the steam mass flow passing through it in order to generate via the generator 7 the electric current or electric power to be provided by the steam power plant and thus to supply consumers connected via a power network.

As stated at the outset, the steam power plant must be able to react flexibly to different power requirements, the relatively slow process of steam generation, which is relatively slow in itself, precluding high flexibility requirements.

To increase the flexibility of the thermal energy storage part 5 is provided with a heat storage unit 50 in the embodiment according to the invention, which is equipped with an electrical heating device Wärmeeinkoppelungseinrichtung. 6 having. In the embodiment shown, the heat storage unit 50 on the output side via a discharge device 51 with the water-steam circuit 1 present in the region of the steam generator section 3, namely connected to the Hochdruckvorwärmern 30, via a heat exchanger. The heat storage unit 50 has a high heat storage capacity and is advantageous for. B. with a solid reservoir (regenerator), liquid salt storage or a Ruths memory provided.

Alternative integration sites or arrangements for the thermal energy storage part 5 consist in a discharge of heat energy in the feedwater part 2, in particular the Niederdruckvorwärmern 23, in other places of the steam generator section 3, or in the (in the Fig. 1 not shown) flue gas path as well as in combinations of these integration sites. The necessary thermal specifications can be met by a suitable design and control of the thermal energy storage part 5.

An essential feature of the invention of the steam power plant consists in a special embodiment of the heat coupling device 6 of the thermal energy storage part 5. The heat coupling device 6 has in accordance Fig. 1 a powered by an electrical power supply 61 with electrical energy warm-up device 60, by means of which the heat storage unit 50 heat energy is supplied. Advantageously, a conductive electrical method based on resistance heating or an inductive electric method is used for this purpose. The electrical heat energy supply 61 is thereby fed by the electric power generated by the steam power plant to load the heat storage unit 50 with heat energy. The electrical power supplied to the electrical heating device 60 can be controlled or regulated by means of a process control. The control or regulation of the output side The electrical power removed from the generator 7 can, for example, be effected as a function of process parameters predetermined or predefinable in the power plant and / or as a function of control or regulating variables of a superordinate network control.

Thus, a load reduction of the steam power plant at a supply of electric power to the electric warm-up device 60 and a supply of heat energy with the thermal energy storage part 5, d. H. during a loading phase, achieved by the electrical energy generated in the steam power plant is used for electrically heating the heat storage unit 50 and the thermal energy storage. A significant advantage of this method is that the steam generation in the steam generator section 3 can continue to operate and a high minimum load reduction of the fed from the steam power plant in the connected power supply power (up to a power of 0 W) is possible. As a result, a very high flexibility of the steam power plant is achieved and prevents a shutdown of the sluggish steam generator device and thus a costly startup of the steam generation process, as in a warm or cold start.

During a discharge of the heat storage unit 50 via the discharge device 51 in the water-steam circuit 1 and the flue gas path, in the present case in the Hochdruckvorwärmer 30, the conserved in the heat storage unit 50 thermal energy is used to heat over the respective heat exchanger, a high-pressure preheating Effecting feedwater. The coupling of the heat for high-pressure preheating thus allows during the discharge phase, a reduction of a tap quantity of steam at the steam turbine of the turbine assembly 4 and thus a higher electrical power through a higher steam mass flow.

The integration concept according to the invention thus makes it possible in steam power plants, in particular coal power plants, to provide a highly flexible reduction of the electrical load on the output side or electrical power output, which allows a minimum load reduction of the steam power plant up to 0 W, depending on the design or control of the electrical heating device 60. The electric auxiliary heater dispenses with an elaborate procedural integration of the storage system into the water-steam cycle 1 and a shutdown of the steam generator, which on the one hand results in no negative integration effects and on the other hand can avoid warm and cold starts. An additional electric power (generated by the warming by means of the thermal energy storage part 5) is achieved here by higher mass flows to the steam turbines, as can be dispensed with a removal of bleed steam for preheating the feed water in Hochdruckvorwarmer.

The inventive design also allows high efficiencies. The heat generated electrically during the charging can be achieved, for example, with the aforementioned conductive method by resistance heating with very high efficiency (> 95%). In addition, the additional electric power generated during the discharge is achieved by increased steam mass flows in the steam turbines, which operate at high isentropic efficiencies (approximately 90%) and thus achieve efficient power generation, possibly taking into account only efficiency-reducing effects due to a higher volume flow in the steam turbines are.

In addition, the high dynamics of the electric heating, as well as the heat input into the feed water, allows a provision of control energy and thus significant increases in flexibility of coal power plants.

Claims (8)

A steam power plant, such as a brown coal or coal-fired power plant, comprising a water-steam circuit (1), a turbine arrangement (4) connected to a generator (7) for electrical power generation, and a thermal energy storage unit (5) comprising a heat storage unit containing a heat storage medium (US Pat. 50), a heat input device (6) provided with an electric heating device (60) and an unloading device (51) connected to the water-steam cycle (1) or a flue gas path,
characterized,
in that the electrical heating device (60) can be acted upon by an electrical energy supply device (61) with electrical energy generated by the generator (7) and removed therefrom on the output side by means of a process control. Steam power plant according to claim 1,
characterized,
in that the electrical heating device (60) is designed as a resistance heating device or as an inductive heating device. Steam power plant according to claim 1 or 2,
characterized,
that the thermal energy storage part (5) is provided with a Ruth's memory, a solid memory or a liquid salt storage. Steam power plant according to one of the preceding claims,
characterized,
in that the unloading device (51) is connected in a steam generator section (3), in particular on a high-pressure preheater (30), or in a feedwater section (2), in particular on a low-pressure preheater (23). Method for operating a steam power plant, in particular a brown coal or hard coal power plant, in which a turbine arrangement (4) is driven via a water-steam circuit (1) and electric energy is generated by means of a generator (7) connected thereto, wherein a thermal energy storage unit (5) supplied in phases of a requested electrical load reduction thermal energy in a loading process and taken in phases of electrical load increase heat energy in a discharge and the water-steam cycle (1) or a flue gas path is supplied and wherein the thermal energy storage part (5) supplied Heat energy is generated by means of an electrical heating device (60),
characterized,
in that the electrical power supplied to the warm-up device (60) is taken from the output of the generator (7) on the output side of the electric power generated by the steam power plant (1). Method according to claim 5,
characterized,
that the heat energy in the discharge process in a steam generating section (3), in particular a Hochdruckvorwärmer (30), or in a feedwater part (2), in particular a Niederdruckvorwärmer (23), the water-steam cycle (1) is supplied. Method according to claim 5 or 6,
characterized,
in that an additional electric power is delivered by the discharging process compared with a normal load, in that an increased volume flow of steam and thus in an in this turbine arrangement (4) an increased volume flow is produced by the discharge of the thermal energy into the water-steam circuit (1). Method according to one of claims 5 to 7,
characterized,
that the loading processes and the discharging are controlled or regulated by a process control function of predetermined and / or predeterminable process parameters, said higher-level control or regulating values are incorporable.

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