WO2018172415A1

WO2018172415A1 - Steam power plant having an improved control reserve

Info

Publication number: WO2018172415A1
Application number: PCT/EP2018/057178
Authority: WO
Inventors: Stefan Becker; Vladimir Danov; Christian Lindner; Thomas Loeper
Original assignee: Siemens Aktiengesellschaft
Priority date: 2017-03-22
Filing date: 2018-03-21
Publication date: 2018-09-27
Also published as: EP3571381A1; US20200131940A1

Abstract

The invention relates to a method and to an apparatus for providing additional control power of a power plant process (10). The power plant process (10) comprises a steam turbine (11) connected into a water vapor circuit, having at least one high-pressure part (12) and a medium-pressure (13) and/or no-pressure part (15), which are connected to one another via a cold intermediate superheating line, a steam generator and a condenser (22). According to the invention, a steam reservoir is provided, which is formed as a Ruths reservoir (5) and in which an encapsulated PCM reservoir (7) is integrated. To charge the steam reservoir, hot steam is taken from the cold intermediate superheating line (17), between the high-pressure (12) and the medium-pressure (13) and/or low-pressure part (14) of the steam turbine, and for charging, and thus for providing additional control power, steam is taken from the steam reservoir (5) and fed back into the water vapor circuit between the steam generator and the condenser (22).

Description

description

Steam power plant with improved control reserve

The share of renewable energies in the energy mix is steadily increasing and is thus an essential element in the implementation of the energy transition. The goal is to increase the share of renewable energies. The challenges with the use of renewable energies lie in particular in the time-varying supply characteristics.

Figure 5 shows a diagram with two functions of power over time. Shown is the temporal deviation of power supply and demand in terms of energy consumption 1 (load) and wind power 2 as an example of renewable energy. Only in the fewest cases does the demanded amount of energy match the supply and the limited possibilities of regulation. Either the load 1 must be operated by stored energy 3, or there is excess wind energy 4 from the wind power production 2 before. In addition, renewable energy sources are not equally ^¬ SEN distributed locally available. This has the consequence that an increased network expansion is necessary, if no Alternati ^¬ ven can be used. This behavior leads to a reserve power market. It will be rewarded for that one is able for a short time to produce either energy to consume (negati ^¬ ve control power), or energy (positive control power).

In order to participate in this market, the flexibility of electricity production from steam power plants or combined gas and steam power plants must be increased.

A positive control power in seconds range can be provided in a steam power plant, for example, by the turbine inlet valves are opened for a short time and by the withdrawal of steam from the Boiler in the short term more power is generated. The Dros ^¬ selung of the main condensate in the condenser, and an additional firing in the steam generator are well-known measures to provide more power in the short term.

An increase in the flexibility of a steam cycle in a steam power plant is also possible through the use of heat storage. The functionality and efficiency of a heat accumulator largely depends on where and in what way a heat accumulator is integrated in the steam circuit. The goal is always to place a suitable Technolo gy ^¬ at a suitable location.

There is no existing standard solution on the market for integrating a heat accumulator in a power plant. Various storage solutions are known from the prior art. A distinction is made between sensitive and latent heat storage. Hot water or pressurized water storage tanks or P2H solutions are known as sensitive heat storage tanks. In this case, heat from the steam cycle or directly electricity is used to produce warm ^¬ water at the level of a district heating pipe. However, these solutions can only be used for negative control power.

Also known are Ruths stores. 1 shows a Ruth's memory in the form of a vapor memory which consists of a large pressure vessel 6 in Wesentli ^¬ chen. Since the heat is stored in the end sensitive in the water, such memory supply only conditionally constant steam temperatures and can be used only for a short time due to the economy and especially the size. Scaling is usually done by the number of devices.

Also known are liquid salt storage. Liquid salt storage are usually used in the steam cycle at high temperatures. The heat is stored sensitively in molten salt. chert. The performance depends mainly on the rate of heat transfer and pump performance. Since energy is usually stored at a very high level, all components must be insulated very well in order to avoid losses.

Also known are batteries for storing electrical energy. The electrical energy can be used for heating. The prices for battery solutions are, however, relatively high.

As latent heat storage phase change materials (PCM) are known. Macroencapsulated PCM are already known from DE 10 2014 203 545 AI. DE 10 2014 203 545 A1 describes in particular the production method of the capsules.

The object of the invention is to provide a method and a device, can be provided by the additional control power in a power plant process.

The directed to a method object of the invention comprises a switched into a steam cycle steam turbine ^¬ , with at least one high pressure and a medium and / or low pressure part, which are connected to each other via a cold Zwischenüberhitzungsleitung (KZÜ), a

Steam generator and a condenser. In this case, a steam storage is provided, which is a Ruths memory, in which an encapsulated PCM memory is integrated. For loading superheated steam from the cold reheat line (KZÜ) between see the high pressure and the middle and / or low pressure part of the steam turbine removed. For discharging and thus providing additional control power, steam is withdrawn and the steam is returned to the steam cycle between the steam generator and the condenser.

The object relating to a power plant OF INVENTION The object of the dung ^¬ comprising a switched into a water-steam cycle steam turbine with at least one high-pressure and a medium and / or low-pressure part, which are connected to one another via a cold Zwischenüberhitzungsleitung (KZÜ). For storage and provision of additional control power while a steam storage is provided, which is a Ruths memory, and in which an encapsulated PCM memory is integrated. In this case, the steam storage is connected for loading with superheated steam with the cold reheat line (KZÜ) between the high pressure and the middle and / or low pressure part of the steam turbine, and connected for discharging with the steam circuit between the steam generator and the condenser.

The invention represents a novel concept for integrating a macroencapsulated PCM (phase change material) memory in a steam circuit. FIG. 2 shows a Ruths memory 5 according to the invention with integrated macroencapsulated PCM. FIG. 3 shows an alternative embodiment of the invention with a Ruths memory 5 with externally connected pipe register system 8 with externally arranged PCM. The Ruth memories in FIGS. 2 and 3 use the saturated water of the Ruth's store 5 as the heat transfer fluid. Each variant can only absorb a certain amount of saturated water. Taking the water volume of a pure Ruth's memory 5 as a reference, the Ruth memory with macro-encapsulated 7 PCM displaces nearly 50% of the water content.

On the one hand, the present invention is based on the consideration of integrating these encapsulated PCM materials 7 into a Ruth memory 5. The resulting vapor storage has a much higher capacity per volume, and is thus clearly superior to a Ruth memory of the prior art. On the other hand, the present invention is based on the idea to integrate the modified Ruths memory according to the invention in a steam power plant. In addition, the storage ^{according to} the invention can provide constant steam parameters over a long time, since the heat is not stored sensitively. During the discharge of Spei ^¬ chers or solidification of PCM material is continuous released heat at a constant temperature level. As a result, the use of this memory is also possible in places where the Graßigkeiten are relatively small. The invention will be explained in more detail below with reference to FIG. 6:

FIG. 6 shows the integration according to the invention of a Ruth's memory 5 with encapsulated PCM materials 7 in one

Steam power plant 10. One can see a steam turbine 11 with a high-pressure part 12, a medium-pressure part 13 and a low-pressure part 14 on a common shaft 15. The steam which has been expanded in the high-pressure part 12 of the steam turbine 11 flows back into the via a cold reheat line KZU 17 Steam generator is heated there, and the central ^¬ pressure member 13 of the steam turbine 11 is supplied. At the cold reheat line 17 of the heat accumulator according to the invention is connected. To load the Ruths-memory 5 steam from the Kaltenüberhitzung (KZÜ) 17 of the steam turbine is removed. The cold reheat 17 represents a safe supply rail in the steam power plant, since the steam can be removed before the start of the turbine, but also during turbine operation. The removal amount from the KZÜ 17 for loading the Ruths memory 5 is limited by the

Minimum flow in the reheater boiler and minimum flow in the medium pressure (MD) and low pressure (ND) turbine.

The withdrawn vapor condenses in the Ruths memory 5, releases its heat of condensation and thereby melts the PCM 7. The PCM phase change temperature is selected as follows:

PCM < ^- Tsat (P MIN KZÜ) 15 The 15K (Kelvin) represents the rate of temperature of the water / steam inventory of the Ruth's memory 5 to the temperature of the integrated PCM material 7. The control valve 18 is advantageous for adjusting the vapor pressure in accordance with the reservoir loading temperature. Since you can quickly remove steam according to the duration of the control valve 18, quickly reduces the power plant performance and thus is already the participation in the negative reserve power market possible with small block performance.

In the case of Dampfentnähme before starting the turbine he ^¬ follows the storage of energy already during the turbine bypass operation. When unloading steam is unregulated removed from the Ruths memory 5. This solidifies the PCM 7, and gives its heat to the water, which evaporates. Since ^¬ by a Dampfentnähme at constant temperature is mög ^¬ Lich. The steam generated in the Ruths memory 5 with integrated PCM 7 has a temperature of: TDampf < ⁼ TPCM ^~~ 15 K.

The 15 K (Kelvin) represents the rate of temperature of the integrated PCM material to the temperature of the Ruth's 5 water / steam inventory.

The steam is passed to the Niederdruckvorwärmer 19 and used by heat transfer to the main condensate. Since ^¬ by the Dampfentnähme is mini mized or even prevented ^¬ from the steam turbine. 11 Thus, more steam remains in the turbine 11 and generates higher power, which can be used as a rule ^¬ performance.

In addition, the higher saturated vapor temperature of the stored vapor tends to increase the temperature of the Hauptkonden- sates after powered by stored vapor Niederdruckvorwärmers 19. This additionally causes a reduced copy ^¬ tion of the steam demand of the feedwater tank below, which in turn means that more steam remains in the steam turbine 11 and in addition more turbine power is generated.

This allows participation in the positive balancing market. The advantage of this integration is that you

Steam can be taken from the KZÜ 17 even at relatively low pressures and stored as heat in the Ruths memory 5 with integrated PCM 7, but nevertheless has a great influence on the power production, since the storage discharge at high

Block services done. As a result, a cost-effective concept with relatively little heat loss is possible.

The following table lists a selection of salt hydrates that meets encapsulated phase change material (PCM) 7 requirements for the treated storage applications. These include, for example, the PCM

95% NaN 3+ + 5% NaCl, consisting of a mass ratio of 95% sodium nitrate and 5% sodium chloride. These materials and the material properties are as specific heat capacity, thermal conductivity, density and the melting ^¬ entropy and the melting temperature known.

From the table it can be seen in a comparison of enthalpies Schmelzent- and the specific heat capacity that although NaN0 ₃ -NaOH poorer heat capacity value has CpPCM, but a significantly greater melting Thal ^¬ pie h _Schme iz release during the phase change. In addition, NaNÜ3-NaOH has a higher thermal conductivity and can better match the energy stored in the molten PCM with the heat transfer. transport the carrying surface of the capsule. Therefore, NaNC> 3-NaOH is the preferred PCM for the invention.

FIG. 4 shows an embodiment of a capsule 20 in which a PCM 21 is arranged. The capsule 20 is a stainless steel tube ^¬ having a diameter between 20 and 100 mm, preferably 50 mm, a length of between 200 mm to 1000 mm, preferably 400 mm, and a wall thickness of between 0.2 and 5 mm, preferably 1 mm , for use. After the capsule 20 has been filled with PCM 21, both ends are pressed together and welded. This results in both capsules 20, a section of 5 mm. In addition, the capsule 20 is filled only between 50 and 95%, preferably 80%, with PCM because the PCM volume changes during the phase change.

The invention enables cost-effective integration ei ^¬ nes memory in a steam cycle, increases the flexibility of the steam cycle and thus allows participation in the negative and positive reserve power market.

It is particularly advantageous in this case that steam storage can already take place from the minimum load of the power plant and even during the startup of the turbine. The steam storage takes place on the high performance level of the power plant.

Another advantage is that the integration manages with minimal additional expenses, which are limited to namely the Ruths memory 5 to be integrated with integrated PCM 7 and connecting pipes. The integration does not require any structural changes in the low pressure feedwater preheating. In the Dampfentnähme 11 from the KZÜ 17, a control valve 18 is provided to adjust the saturated steam parameters according to the selected PCM. The steam storage can also be unregulated. It is particularly advantageous that the memory saturated steam he witnesses ^¬, the heat can be transferred directly from the low-pressure economizer 19 to the main condensate. In addition, the existing promotion of the Nebenkondensates allowed with the

Nebenkondensatpumpe in the main condensate flow complete use of the stored energy.

Since the Ruth's memory 5 produced with integrated PCM 7 at a higher pressure level of saturated steam than the low druckvorwärmer 19 associated Turbinenanzapfung, the temperature of the main condensate is increased after the supplied via vomit ^¬ cherten steam Niederdruckvorwärmers what advantageous ^¬ way the steam requirement for the reduced subsequent preheaters. As a result, not only at the location of the storage integration, turbine recovery steam is replaced by steam from the storage, but at the subsequent low pressure preheater (in our case, the feedwater tank).

Turbine withdrawal steam is reduced. Any additional storage for providing support steam for the feed water tank is avoided by this concept or its requirements are reduced.

Claims

claims

1. A method for providing additional control performance of a power plant process (10) comprising a switched into a water-steam cycle vapor turbine (11), we ^¬ nigstens a high-pressure (12), a central (13) and / or low-pressure part (14), which are interconnected via a cold reheat line (17), a steam generator and a condenser (22)

a steam storage is provided, wherein the steam storage is a Ruths memory (5), in which an encapsulated PCM memory (7) is integrated,

- For loading superheated steam from the cold reheat line (17) between the high pressure (12) and the middle (13) and / or low pressure part (14) of

Steam turbine (11) is removed, and

- Is taken for discharging and thus to provide additional control power steam, and the steam in the water vapor cycle between the steam generator and the condenser (22) is returned.

2. Power plant (10) comprising a switched into a water vapor ^¬ cycle steam turbine (11) with at least one high-pressure (12) and a central (13) and / or low-pressure part (14), which (via a cold reheat line 17 ) are interconnected,

characterized in that

a steam storage is provided for storing and providing additional control power, the steam storage is a Ruths memory (5), in which an encapsulated PCM memory (7) is integrated, wherein the steam storage (5) for superheated steam with the cold reheat line (17) is connected between the high-pressure (12) and the medium (13) and / or low-pressure part (14) of the steam turbine, and for discharging with the steam circuit between the steam generator and the condenser (22). connected is .