DE102012010795A1 - Steam power method for electric power generation in steam power plants, involves carrying out stress relief to apply high pressure and temperature potential, and increasing temperature according to high pressure steam turbine - Google Patents

Abstract

The steam power method involves carrying out stress relief after high temperature intermediate superheating to apply a high pressure and temperature potential. The significant temperature is increased only according to the high pressure steam turbine (3) in a high temperature intermediate superheater (4), since the admissible voltage of the materials reduces with increasing temperatures, when high temperatures are obtained at the lower pressures till the material limits, which reduces the difference between the combustion chamber and steam temperatures.

Description

The invention relates to a related to the steam power process thermal process, which improves the overall efficiency by special modifications. Such a solution is needed primarily in the energy industry.

The increasing global energy demand increases the anthropogenic pressures on the climate and the environment. Economical use of energy and efficient thermal conversion processes are becoming increasingly important in order to avoid further accelerating climate change. Steam power plants are responsible for the reliable share of power generation even in the age of renewable energies. The state of the art is at a very high technical level. Modifications such as regenerative feedwater pre-heating, reheating, increasing the live steam parameters, lowering the condensation temperature, optimizing the system components and improved process control are measures to make power plants fit for the needs of the 21st century. The focal points are named in the research association abayfor (www.abayfor.de/kw21). Increasing live steam parameters to 700 ° C at pressures of 350 bar and over requires hot and high strength superalloys that are still in development. The compound high temperatures at high pressures encounters material boundaries, so between the combustion chamber temperature and the max. Steam temperature still exist thermal reserves.

If it were possible to use them, this would mean a significant improvement compared to the prior art. Austenites, for example 800 H, have a permissible stress of about 35 MPa at 700 ° C., which is reduced to about 7 MPa at 900 ° C. or nickel-based alloys, for example IN 617, in the temperature range from 850 ° C. to 1100 ° C, the permissible stress decreases from approx. 25 MPa to approx. 7 MPa. Higher temperatures are therefore manageable, if the internal pressure would not be so high, as this significantly affects the allowable stress.

It is therefore an object of the invention to design the steam power process with increased efficiency so that a higher temperature gradient is available in the course of the process.

The object is achieved according to the invention essentially by the characterizing features of claims 1 to 5. In steam power plants, intermediate superheaters are state of the art in order to be able to efficiently use a high pressure gradient down to the wet steam range. In this case, superheated high-pressure steam in the high-pressure turbine to the wet steam area is relaxed z. B. from 260 bar / 545 ° C to 55 bar / 300 ° C, coupled and heated by installed in the steam generator pipe systems back to 545 ° C outlet temperature. In the middle and low pressure stages then the relaxation takes place up to the condensation pressure z. B. from 55 bar / 300 ° C to 0.05 bar / 32 ° C.

It would be better if the pipe system for reheating in the combustion chamber hot area of the steam generator is placed and dimensioned so that the material potential in the medium pressure range z. B. 55 bar and lower, temperature-related can be fully exploited. Were it previously as in the numerical example 545 ° C at 55 bar, so steam temperatures of about 800 ° C are possible because the internal pressure of 55 bar compared to the live steam pressure 260 bar gets along with the decreasing allowable voltage. However, the first rows of turbine blading must be cooled analogously to a gas turbine. In addition to the usual cooling methods such as film, impingement or internal cooling, the blades can also be protected by surface evaporation, as decoupled condensate wets the hot gas contours. Thus, the advantages of the steam power process to combine high pressures combined with the benefits of a hot gas turbine, which has a positive effect on the overall efficiency. Problems due to wet steam blade erosion in the case of low-pressure expansion no longer exist because it runs to a large extent outside the critical range.

The proposed solution can already be achieved with constructive measures on the steam generator and the medium and low pressure turbines with existing materials significant efficiency gains without having to wait for new superalloys or hope.

1 a schematic block diagram of the steam power process with the high-temperature reheat and the cooled superheated steam turbine for electric power generation in the cycle.

2 Represents the state-of-the-art overheating and the high-temperature reheat in the temperature-entropy diagram for IAPWS-IF97 Industrial Formulation Water with the parameter example of the description.

LIST OF REFERENCE NUMBERS

1

steam generator

2

High-pressure superheater

3

High-pressure steam turbine

4

High-temperature reheaters

5

Medium or low pressure steam turbine

6

capacitor

7

condensate pump

8th

condensate

9

steam

10

enerator

11

Cooling steam for blade cooling

12

optional condensate for surface evaporation

13

wave

14

heat source

15

Relaxation after reheating prior art

16

Relaxation after high-temperature reheat

17

usable temperature reserve due to lower vapor pressure

Claims (5)

Steam power process with increased efficiency by high-temperature reheat for the generation of electrical energy in the cycle, by not the relaxation after reheating prior art ( 15 ) but the relaxation after high temperature reheat ( 16 ) in order to be able to use a high pressure and temperature potential, characterized in that the relevant temperature increase only after the high-pressure steam turbine ( 3 ) in the high-temperature reheater ( 4 ), since the permissible stress of the materials decreases with increasing temperatures, higher temperatures can be achieved at low pressures up to the material boundary, which significantly improves the process efficiency and reduces the difference between combustion chamber temperature and steam temperature. Steam power process with increased efficiency by high-temperature reheat for the generation of electrical energy in the cycle according to claim 1, characterized in that the high-temperature reheater ( 4 ) in the combustion chamber of the steam generator ( 1 ) near the heat source ( 14 ) is placed to the usable temperature reserve by lower vapor pressure ( 17 ) on the working fluid steam ( 9 ) transferred to. Steam power process with increased efficiency by high-temperature reheat for the production of electric power in the cycle according to claim 1 and 2, characterized in that the medium or low pressure superheated steam turbine ( 5 ) must be cooled. Steam power process with increased efficiency by high-temperature reheat for the production of electric power in the cycle according to claim 1 to 3, characterized in that for the medium or low pressure super steam turbine ( 5 ) either cooling steam for blade cooling ( 11 ) from the high-pressure steam turbine ( 3 ) or optionally condensate for surface evaporation ( 12 ) is used for cooling. Steam power process with increased efficiency by high-temperature reheat for electric power generation in the cycle according to claim 1 to 4, characterized in that the Höchtemperatur reheat shifts the relaxation process from the wet steam region, whereby Schaufel erosion problems are avoided.

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