Enhanced water/steam cycle for advanced … Water/Steam Cycle for Advanced Combined Cycle Technology...

Enhanced Water/Steam Cycle for Advanced Combined Cycle Technology

Author: Patrick Bullinger Siemens AG; Energy Solutions, Product Line Marketing Plant Solutions Power Gen Asia Bangkok, October 3 – 5, 2012

Abstract The current energy market is driven by the request of further reducing CO2 emissions. This

accelerator for eco-friendly power generation is resulting in the necessity to integrate more

renewable resources in the energy mix. The weather and daytime dependency of renewable

energy causes highly fluctuating load profiles in the grid. A back up power generation with

advantages in emissions, flexibility and low operational costs is required to ensure reliable

electricity production. The catastrophe of Fukushima in March 2011 changed the direction of

nuclear power generation in many regions. Combined cycle power plants can build a bridge

towards the future when nuclear power plants have been switched off and the integration of

renewable has been decelerated.

Due to high availability of gas resources in certain regions and further extension via liquefied

natural gas (LNG) supported by the economic growth especially in emerging countries,

combined cycle power plants are expected to play a major role in the energy mix in the future.

A new generation of gas turbines with combined cycle plant efficiencies of over 60% and

enhanced operational flexibility entered the market with commercial operation in summer 2011.

The key to implementation of those new features is overall plant optimization, since power

plants have to be designed to accommodate the new performance parameters.

A major driver for performance improvement is the optimization of the water/steam cycle in

regard of temperature and pressure. Steam temperatures far above 565°C up to ~600°C and

steam pressures above 170bar are used to attain highest efficiencies. These ambitious

parameters cause huge challenges in regard of boiler materials, flexibility of the boiler and water

chemistry.

Siemens is the only company to have accumulated operational experience with raised steam

parameters in the combined cycle power plant “Ulrich Hartmann” SCC5-8000H 1S; Irsching

Unit No.4 with a net efficiency of 60,75%.

Based on that experience this paper presents the issues to be taken into account when designing

an advanced water/steam cycle.

Power Gen Asia Bangkok, Oct. 3. -5. 2012 1

Table of contents 1 Introduction ..........................................................................................................................3 2 The levers of Performance increase....................................................................................7 3 Challenges of the advanced cycle ........................................................................................9 3.1 Impact on boiler materials...............................................................................................9 3.1.1 Impact of steam side oxidation.............................................................................9 3.1.2 Spallation............................................................................................................13 3.2 Application limits of the drum type boiler ....................................................................14 3.3 Water chemistry ............................................................................................................15 4 Technical solution...............................................................................................................17 4.1 Boiler material for the EN and ASME market application ...........................................17 4.2 BENSON® technology with 3 pressure Reheat............................................................18 4.3 Condensate Polishing – the key element for minimized chemical wear and tear .........20 5 Operational experience - EON Ulrich Hartmann SCC5-8000H, 1S (Irsching No.4).......21 6 Summary and Outlook.......................................................................................................26 7 References ...........................................................................................................................28 8 Copyright ............................................................................................................................29


1 Introduction Today’s combined cycle power plants (CCPP) have to fulfill challenging requirements in order

to comply with the boundary conditions requested by the energy politics, infrastructure and

periphery. Although these requirements differ from region to region due to specific market

environments, three major drivers can be determined. All of these requirements are necessary to

ensure a successful operation of the power plant.

- Investment

- Efficiency

- Operational flexibility

Investment Most of today’s power plant projects are purely economical driven. Naturally, the investor

expects an attractive return of investment. Beside the margins generated by the revenues the

investment is a key figure. It does not mean that the lowest price will result in the most

attractive business model, as often reduced first investment result in additional cost during

operation or reduce the capabilities of the proposed solution. The whole life cycle costs of a

power plant have to be taken into account. Nevertheless, it is essential to optimize the solution

to the lowest possible invest without jeopardizing the business model of the project.

Efficiency The demand of highest efficiencies is a key requirement of today’s and tomorrows combined

cycle power plants. Current developments in the energy markets are requesting fuel

consumption saving and therefore the need of higher efficiencies due to the following reasons:

1. High gas prices in some regions (especially in the Asian, European and Latin American

markets) with the consequence of high electricity production cost.

2. The further reduction of CO2 emissions in order to enable-eco friendly operation is

indispensable. The contribution of combined cycles is to reduce emissions due to operation at

higher efficiencies. To give an example, an efficiency improvement of 1.5%-pts. saves 14.700


tons of fuel gas per year while reducing CO2 emissions by 41.000 tons per year when a 600MW

combined cycle power plant will be operated at base load.

3. A very simple but decisive effect is the higher profitability during operation with higher

efficiencies. Furthermore a high efficiency results in a low merit order and increases the

probability to be dispatched.

Operational flexibility The need of operational flexibility has become more and more important in recent years and this

need is expected to continue for the mid term. To become a prime candidate of the dispatcher

today’s combined cycle power plants have to be able to operate with fast fluctuating load

profiles. Fluctuating load will occur more frequently in the future due to the following reasons:

First is the above mentioned increase of renewable integration in the energy mix. The non-

availability of wind or solar energy has severe impact on the load profile.

Figure 1.1 shows the forecasts for a typical day in Germany in 2020 with low versus high wind

power feed-in. In the case of a high expected wind power input during the day as shown here, no

further fossil power generation is required during the night, i.e. when demand is low, as there is

a residual load (difference between demand and renewable feed-in) of zero or even over-

capacity (that is to say negative residual load). Compared to a day with a low wind feed-in there

is a continuous demand for about 20 GW of conventional base load capacity. The conclusion to

be drawn is that the major part of the conventional power generating capacity will probably not

be continuously required. This is the case in countries with growing renewable portfolio.


Source: joint study Siemens and VDE, AT40 scenario, March 2011

Low wind feed-inLow wind feed-in High wind feed-inHigh wind feed-in

Peak

12 GW

≥ 23h

20 GW

≥ 11h

10 GW

≥ 10h8 GW

≥ 9h2 GW

≥8h

2 GW

≥6h

10 GW

-10.000

-5.000

0

5.000

10.000

15.000

20.000

75310 2232119171513119 5

≥11h

≥10h

≥9h

≥8h

≥6h

Peaks

Loadramps:

Average: 56 MW/min

Max.: 377 MW/min

Min.: 0,028 MW/min

ContinuousContinuous

Daily start-stop

100% daily start-stop

Up to 100% of the fossil fleet in daily start-stop operationLoad ramps of about 200MW/min to be covered

Peak LoadPeak Load

0

5.00010.000

15.000

20.00025.000

30.000

35.000

40.00045.000

50.000

252321191715131197531

≥11h

≥10h

≥9h

≥8h

≥6h

Peaks

≥23h

2 GW

6 GW

2 GW

1 GW

2 GW

4 GW

≥ 10h

Peak

≥ 6h

≥ 9h

≥ 8h

≥ 11h

Overload

Time [h]

Res

idu

al l

oad

[MW

]

Res

idu

al l

oad

[MW

]

Time [h]

Figure 1.1 Residual load cycles in the year 2020 (examples of feed-in scenarios) for Germany

Second is the highly fluctuating load caused by the changing demand during peak time.

As an example for Singapore the load profile of a typical day is shown in figure 1.2. The

required load varies between 4,5GW (night time) and 6,5GW (peak). This fluctuating load has

to be captured by highly flexible combined cycle power plants. This is especially important in

Asia where more than 50% of the energy supply is generated by less flexible coal fired power

plants.

Many energy markets already require and compensate providers for short term additional power

generation. This minute reserve can be very profitable and can only be provided by highly

flexible power plants.


Sunday Peak load:Mostly SPP and some CCPP are runing

Peak & Intermediateload:Predominantly CCPP

Weekday Peak load:SPP and CCPP areoperating

Source: Enegy Market Authority, Singapore

May 2010

6552MW

4474MW

Figure 1.2 Fluctuating load profile in Singapore Taking into account an increasing worldwide gross domestic product (GDP) and the growing

availability of natural gas through the continuous extension of natural gas grids in combination

with the uncertain outlook of nuclear power plants it’s not surprising that combined cycle power

plants will play a major role in the future energy mix. Considering the ASEAN region, a

compound annular growth rate (CAGR) from 2012 – 2017 of almost 6% is expected. LNG is

becoming worlds new gas highway of choice with a potential of 10% CAGR capacity growth

for the next 10 years. Especially for the ASEAN region with a global demand of LNG of almost

60% it clearly confirms the need of further extending of combined cycle power plants fleet.

The application of an advanced cycle supports the necessary extension of combined cycle power

plants in regard of required efficiency, operational flexibility and profitability. This paper

describes the inherent challenges to be taken into account when designing such a cycle.


2 The levers of Performance increase

Steam turbine Water steam cycle Gas turbine

Improved sealing technologies

Optimization of blade profiles (3DS)

Increase of steam parameters

Triple pressure reheat cycle

Improved heat transfer

Increase of turbine inlet temperature

Reduction of cooling air consumption

Optimization of flow path and blade profiles

Fuel preheating

Figure 2.1 Plant efficiency improvement areas

There are several different approaches that can be used to increase efficiency of a combined

cycle power plant. As shown in figure 2.1, in addition to optimization on a component level

main driver is the optimization of the water/steam cycle.

This paper will focus on the improving combined cycle capability through changes to the

water/steam cycle, specifically increasing the steam temperature and pressure. The necessary

increase in steam parameters is only feasible due to the steady improvement of the gas turbine

and steam turbine. The constant increase of the turbine inlet temperature of the gas turbine led to

exhaust temperatures far above 600°C and enabled the application of a 600°C water/steam cycle.

Figure 2.2 shows the constant improvement of combined cycle efficiencies starting from 52%

efficiency with low steam parameters in 1991.

Siemens H-class combined cycle power plant technology has proven the capability to operate at

efficiency levels far above 60% today. This development was enabled via a stringent application

of total plant optimization.


1991 1996 2001 2011

SGT5-2000E SGT5-4000F SGT5-4000F SGT5-8000H

52 % Efficiency*Killingholme

2 x 470 MW, 2x(2+1)

56 % Efficiency*Didcot B1&2

702 +710 MW, 2x(2+1)

58 % Efficiency*Mainz-Wiesbaden

>400 MW, (1+1)

>60% Efficiency*Irsching 4

SCC5-8000H 1S 570 MW

Basis - 7.1 % - 10.3 % - 13.3 %

Reduction of CO2 emissions

Advanced GT technology allows for significant improvement of competitiveness and serves as basis for CO2 reduction of gas fired generation

* Net efficiency achievable with this technology / project specific efficiencies may vary

Texh = 548°CT/p Life steam = 516°C/ 75bar




Figure 2.2 Product development of CCPP The increase in steam parameters coming from 565°C and 105 bar (typical SCC5-4000F

application) is a design challenge especially for the Heat Recovery Steam Generator (HRSG) for

the following three reasons:

1. Steam parameters above 565°C require special attention to the use of boiler

materials.

2. Above a certain steam pressure level the natural circulation as realized in a natural

circulation drum type boiler can not be sustained anymore.

3. High pressure steam increases the challenges to mainatain feed water chemistry

within limits.

Siemens engineering has developed designs to overcome these hurdles and achieve record

breaking combined cycle efficiency.


3 Challenges of the advanced cycle The three challenges as described in chapter 2 defined by the application of raised steam

parameters will be described in the following chapter.

3.1 Impact on boiler materials One of the most critical components of the advanced cycle is the Heat Recovery Steam

Generator (HRSG), especially the HP-superheater and IP-reheater section. To enable operation

conditions with steam temperatures of ~600°C and pressures above 170bar, materials for the

critical sections need to have a combination of the following capabilities:

- sufficient creep strength behaviour at design temperature (stable microstructure)

- acceptable resistance to steam side oxidation (determined by Chrome content)

- sufficient fatigue characteristics to resist to extreme thermal cycling requirements

- acceptable cost of the design solution

3.1.1 Impact of steam side oxidation

A huge challenge caused by increased steam parameters is steam side oxidation of the affected

components. Figure 3.1 provides an overview of typical tube inner and outer wall temperatures

for the HP-final superheater fintubes. Temperatures marked in green are related to clean

conditions without any oxidation layer on the tube inner wall. Temperatures marked in red

represent the case that steam side oxidation occurs. The oxidation layer on the inner wall hinders

the heat transfer due to its low thermal conductivity and results in an increase of the tube wall

temperatures. The increased middle wall temperature results in reduced strength properties and

has to be considered in the design by selection of appropriate temperature margins. Also a

respective corrosion allowance should be considered to account for the loss of tube base

material due to the oxidation.

This effect would have to be considered in the design of the respective components.


Figure 3.1: Temperature behaviour based on steam side oxidtaion

Oxidation rate The formation of oxide scale on the tube inner wall (oxidation kinetic) is mainly driven by: - Steam temperature, tube inner wall temperature

- Material (esp. chrome content)

- Grain size (esp. austenit)

Steam temperature The influence of the steam temperature on the oxidation layer growth rate is shown in figure 3.2

for the application in the inner tube wall with the material P91. The higher the steam

temperature the higher the oxidation rate. A disproportionate increase of the oxidation layer

thickness can be seen in the temperature range of 600°C which is the crucial temperature for the

advanced cycle. This effect has been evaluated and confirmed by different applications in steam

plants and has to be considered for the design of the respective components.


Figure 3.2 Impact on oxidation layer thickness [2] Chrome content The oxidation rate is determined by the Chrome content of the material. The higher the Chrome

content the better the oxidation resistance. Figure 3.3 shows the oxidation growth behaviour for

different materials (based on a tube inner wall temperature of 600°C). The chart for 9% chrome

content is representative for T91 and T92, whereby oxidation resistance of P91 is reported to be

slighly better compared to T92. The chart provided for 12% chrome steels is typical for

martensitic materials.


Figure 3.3 Oxidation behaviour based on Chrome content [2]

A significant change in oxidation rate can be seen at a content above 12% (figure 3.4). A further

increase of the Chrome content has only slight impact on the resistance of the oxidation rate.

Below a Chrome content of 9% (e.g. P91/ T91) the oxidation rate behaviour is comparatively

poor. This effect has to be considered for the design of the respective components.

Chrome content

Ox

ida

tio

n r

ate

Figure 3.4 Chrome content over oxidation rate


3.1.2 Spallation

The oxide scale on the tube inner surface has got different thermodynamic properties compared

to the base material. Especially the thermal expansion coefficient is different. Especially in case

of transient operation, e. g. start-up and shut-down resulting in mechanical stress between oxide

scale and base material. Above a certain thickness of the oxidation layer spallation has to be

unavoidably expected. Spallation has a major impact on the water/steam cycle due to the

following reasons:

1. Solid particle erosion due to spallation especially during start-up and shut-down

(highest strain load)

2. Material abrasion due to spalling (loss of base material, loss of strength)

3. The oxidation layer serves as protection of itself by limiting further oxidation growth.

Spallation in a certain temperature and time range results in an uncontrolled growth

behaviour of the oxide layer.

As a consequence above a certain temperature range tube materials with chrome content >12%

have to be considered to limit negative effects caused by the formation of oxide scales on the

tube inner walls.

Reference [1] Severe scale separation, cracking, and exfoliation were observed in T91 pendant reheater tubing

in a Japanese utility boiler after around 40.000 hours of operation. Separation occured at the

interface between the inner and outer layers of scale (figure 3.5).


Figure 3.5 Spallation of inner surface tube

3.2 Application limits of the drum type boiler Drum type boiler A high-pressure drum in the HRSG is one of the most critical component with regard to

limitation in the start-up and ramping procedure as a thick-walled component exposed to large

temperature gradients and high operating pressures. Fatigue damage of the drum caused by

alternating stress is increasing disproportionally with higher wall thickness.

Typical approximate values for the drums are:

Pressure level Wall thickness

180bar ~140mm --> SCC5-8000H

130bar ~100mm --> SCC5-4000F

First calculation shows, that the impact on life time for a 160 bar solution is approximately 8

times higher then for a 125 bar solution when similar load gradients are considered


From a thermodynamical point of view, another effect is restricting the application of the drum

boiler especially for increased steam pressures (figure 3.6).

The natural circulation effect is driven by the difference in density of water and steam in the

evaporator and downcomer tubes. As the difference in density decreases with the higher

pressures there is a limit for drum pressure of about 180 to 190 bar for natural circulation

boilers. In regard of a safety margin application, the practical limit will be maintained at

~170bar.

0

100

200

300

400

500

600

700

800

900

1000

0 50 100 150 200 250

Pressure [bara]

Sp

ec

ific

De

ns

ity

[k

g/m

3]

Density Water

Density Steam

Difference

Figure 3.6 Pressure limit for natural circulation

The pressure limitation is counter productive to the requirement of raised steam parameters as

described above. For that reason an application of a thick walled drum type HRSG is suitable

for moderate steam parameters below 170 bar and base load operation only.

3.3 Water chemistry Impurities in the water/steam cycle can lead to deposits and corrosion phenomena of the

affected components. It must be realized that this effect has negative impact on the lifetime of

the components and that efficiency of the power plant might be decreased. The Water chemistry

is a crucial topic for the successful operation of a power plant independent of the boiler type.

In a once-through boiler design the complete evaporation of the feedwater occurs within the

evaporator tubes. All salt impurities as well as corrosion products will deposit at the internal


heat exchanger tube surfaces especially in the evaporation area. It is also possible that these

impurities and corrosion products will be transported into the super-heater and the steam turbine

and may entail severe damages (e.g. stress corrosion cracking).

In a drum type boiler application two different effects occur and have to be considered for the

respective design. First is the transportation of impurities due to mechanical and vaporous

carryover and the second is increasing solubility of silica at high pressure steam.

It is important that mechanical carryover is controlled and well-known for each boiler. Vaporous

carryover occurs due to the volatility of the substances present in the boiler water. The effect of

carryover is intensified with raised steam pressures.

Silica shows the highest solubility of feedwater contamination within high pressure steam

Deposits of silica caue an efficiency reduction due to increased roughness of the steam turbine

blading surface.

These two effects are intensified at raised steam parameters which is challenging for the design

of an advanced cycle.


4 Technical solution Based on the challenges described above this chapter addresses the technical solution for the

application of raised steam parameters in the advanced cycle.

4.1 Boiler material for the EN and ASME market application To find the best possible design solution for the material of the HP-superheater and IP-reheater

heating surfaces the effects as described in chapter 3.1 have to be considered for the respective

design. A detailed design study on that topic has been performed by Siemens. The programm

target was to find the best technical solution for the application in an HRSG with 600°C steam

temperatures for both the EN (former DIN) and ASME market requirements. Solutions are

identified for regions which use EN requirements and those that use ASME requirements.

Material choice for EN Material VM12-SHC from Vallourec Mannesmann has been selected for the application in the

EN market. This material has a chrome content of 12% and is considered the best technical

solution to fulfill all requirements in regard of creep, steam side oxidation, fatigue and cost.

VM12-SHC has been applied in Siemens SCC5-8000H power plant Ulrich Hartmann (Unit

No.4; Irsching) for the high temperature superheater and reheater section up to 600°C. During

design, manufacturing and installation valueable experience has been obtained for future

applications. As of August 2012 the plant is operating for more than 12.500EOH in CCPP

operation without any issues.

Material choice for ASME According to Vallourec Mannesmann the issue of a Code Case for the use of VM12-SHC within

ASME stamped boilers is still uncertain and will take a minimum of one year. Therefore VM12-

SHC cannot currently be used at this time for ASME stamped applications. VM12-SHC is the

technical solution for the EN market only.

Based on that issue and with the support of operational experience from Ulrich Hartmann power

plant (SCC5-8000H; 1S; Irsching No.4) a design study of the different feasible material

combinations has been conducted. Various sophisticated detailed design solutions have been


evaluated in regard to creep, steam side oxidation, fatigue and cost. An alloy on a basis of a 18-

20% chrome content has been found as the best technical and economical solution for the

advanced cycle to meet ASME market requirements.

4.2 BENSON® technology with 3 pressure Reheat The main feature of BENSON® boiler technology is once-through steam generation. In this

type of boiler, the conventional separation of steam and boiling water inside a boiler drum is not

necessary. Steam is generated directly within the evaporator tubes of the boiler. As shown in

figure 4.1 the high pressure drum can be omitted and replaced by a steam separator.

Principal Diagrams of Evaporator SystemsPrincipal Diagrams of Evaporator Systems

Steam

Feed-water

Heating

Drum Boiler

Steam

Feedwater

Once-Through Boiler

Heating

Figure 4.1 BENSON® vs. drum type boiler

A temperature-controlled start-up process which uses optimized high-capacity de-superheaters

to limit steam temperatures during the startup process has been developed for warm and cold

starts. This reduces thermal stress in critical components of the steam turbine.

The application of a BENSON® HRSG allows an increased number of permissable starts and

cycling events over the lifetime, by reducing stress induced fatigue in the high pressure section

of the HRSG.


Since the limiting component of the HP drum is omitted, and due to a thin walled separator

with wall thickness of only ~55mm at 180bar increased load gradients and highest operational

flexibility can be realized.

To further improve the water/steam process with regard to combined cycle efficiency, a three

pressure reheat process has been applied. Figure 4.2 shows a typical Q-T (transfered heat,

temeperature) diagram for HRSG comparing the different reheat processes in order to explain

the advantage of a three pressure reheat process.

The exhaust gas temperature limits the maximum achievable steam temperature. The exhaust

gas thermal heat defines the limit for overall heat transfer to the water/steam cycle.

The area between the exhaust gas temperature line (pink) and the corresponding water/steam

process line defines the amount of energy losses. The thermodynamical target is to reduce this

area in order to generate the highest possible heattransfer between the exhaust gas and the

water/steam cycle. This improvement can be achieved by increasing the heat exchange surface

or by the application of an improved three pressure reheat process. Due to the high cost impact

of increasing heat exchange surfaces, a theoretical optimum for the corresponding process has

been defined for the application in a three pressure reheat process.

Figure 4.2 Temperature curve of a typical Heat Recovery Steam Generator (HRSG)

The definition of economically optimized heat exchange surface is based on economical criteria

and rules the process design as well as achievable water/ steam temperature, pressure and flow

rates. As this component is of major importance for boosing efficiency and operational


flexibility this sophisticated design solution has been developed Siemens in-house on the basis

of the available experience with previous BENSON® boilers. .

4.3 Condensate Polishing – the key element for minimized chemical wear and tear The operation of the Condensate Polishing Plant ensures the required feedwater purity for a

once-through boiler. Because of the concept of mixed bed filter with upstream mechanical

treatment process (one way cartridge filters) the main condensate is cleaned from corrosion

products and ionic impurities. Siemens recomends to use a condensate polishing plant for once-

through boiler in order to keep the contamination of feedwater within the limits (e.g. VGB or

EPRI).

The evaporation of the drum boiler circulating water causes a continuous concentration of trace

impurities introduced by the feedwater. In order to achieve the recommended values for steam

purity and boiler water quality the operation of the boiler blow-down has to be performed. With

increased temperature and pressure the volatility of the impurities is increased and a higher

boiler water quality and respectively higher feedwater quality may be required. Therefore the

usage of a condensate polishing plant has to be considered.

Additionally the main advantages of a condensate polishing plant are:

Waiting time for steam purity is reduced (shorter start up times especially for

cold and warm starts)

Impurities concentrations will stay well beyond the critical limits

No operational limitations of the power plant

Higher flexibility

Lower blow down rates (reduced loss of water and heat)

Reduced duration of commissioning time

Minor contamination due to leakages will be removed


5 Operational experience EON Ulrich Hartmann SCC5-8000H, 1S (Irsching No.4) The Siemens combined cycle power plant Ulrich Hartmann (SCC5-8000H; 1S; Irsching No.4)

is the first power plant in commercial operation with a proven net efficiency far above 60%

(60,75% confirmed by the independent technical inspection authority “TÜV SÜD”). This power

plant was extended and converted to a combined cycle power plant and was restarted in January

2011. The simple cycle operation with the new H-class technology had first fire in December

2007.

The single shaft design was developed in the early 1990s and has been successfully

implemented since then in the SCC5-4000F 1S. More than 100 units using the single shaft

design are currently in commercial operation.

The H-class gas turbine design is a common development that integrates Westinghouse and

Siemens design experience and combines the best technologies out of both established product

lines to ensure a best available and reliable solution.

Siemens is the first and only manufacturer who realized the operation of a combined cycle

power plant with the application of an advanced cycle. All relevant requirements necessary for

the advanced cycle has been applied.

- raised steam parameters

- BENSON® Technology with three pressure reheat

- Application of VM12- SHC for boiler materials

This overall plant optimization led to the world record net efficiency of 60,75% without

sacrificing operational flexibility. Figure 5.1 shows the plant layout of Irsching Unit No.4.


Figure 5.1 Plant Layout of Ulrich Hartmann

BENSON® Technology – development and delivery by Siemens E.ON’s Ulrich Hartmann combined cycle power plant is characterized by the application of the

proven BENSON® design technology with a three pressure reheat process. This power plant is

the first unit in commercial operation (> 12.500 EOH and >330 starts; CCPP operation) with

raised steam parameters:

GT exhaust temperature ~625°C

Life steam temperature ~600°C

Reheat temperature ~600°C

Life steam pressure ~170bar

This combination enables the breakthrough of highest sustained efficiency with great

operational flexibility. The once through Boiler with BENSON® Technology as applied in

Irsching No.4 with all the advantages of approved design concepts is shown in figure 5.2. The

design principles are based on the proven F-class plant design with high operational experience.


Approved Design Concept

3-Pressure with Reheat

Horizontal Arrangement, Top Supported

Cold Casing Construction

Standard Plant Arrangement Concept

Standard Process Engineering Equipment

11-Nov-201011-Nov-2010

Figure 5.2 BENSON® HRSG

The application of the boiler material VM12-SHC was applied in Irsching No.4 in order to apply

the best technical solution in regard to creep, steam side oxidation, fatigue and cost.

Operational Flexibility

Although Irsching No.4 was designed and sold as a base load unit the current dispatch situation

requires a daily start/stop cycle (figure 5.3). This high fluctuating load profile can be matched

due to the high capacity of operational flexibility of this combined cycle power plant. This

advantage of exceptional flexibility required by current market environments will be described

in the following.

Figure 5.3 typical daily load profile of Irsching No.4


The application of the FACYTM (FAst CYcling) Technology facilitates an overnight shut-down

and helps further reducing CO2 emission and saving fuel cost. Figure 5.4 shows an extract of the

test results of the start-up procedure in Irsching No.4. The FACYTM technology was tested

successfully on the basis of raised steam parameters (~170bar; 600°C).

0

100

200

300

400

500

600

Time [min]

0

10

20

30

40

50

60

ST speed

Plant start-up time < 30 min.

GT speed

GT ignition GT @ base load

CC full load

Tu

rbin

e S

pee

d

Pla

nt

Ou

tpu

t

GT load

Plant output

~50%~36%Average efficiency (time frame for conventional start)

~326 MWh~514 MWhFuel consumption (start up only)

Hot startwith FACY™

conventionalhot start

~50%~36%Average efficiency (time frame for conventional start)

~326 MWh~514 MWhFuel consumption (start up only)

Hot startwith FACY™

conventionalhot startload

time

Conven-tionalstart up

Improvedstart up

ImprovementImprovement

~30 min.

Figure 5.4 fast start up with FACYTM

FACYTM enables the first steam generated to be delivered directly to the steam turbine. The

shorter start-up time and the ability to utilize the steam from the very beginning improve the

formerly inefficient start-up process by 14% points. That enables the participation in the highly


profitable spot market (tertiary reserve). Table 5.5 shows a reference of successful installed

FACYTM technology in commercial operation.

Table 5.5 References of FACYTM Technology

Not of less importance is the opposite direction in regard of fast shut-down due to grid failures

or sudden oversupply of renewable (negative residual load). A fast shutdown has been validated

in Irsching Unit No.4 within less than 30 minutes. Despite a world class efficiency and power

the plant can be parked at less than 100MW (20% CCPP power) with an efficiency typical for

high end open cycle applications.

For that reason the SCC-8000H is the perfect choice for high efficient applications in all

relevant operation regimes (Peaker, Intermediate or Base Load) and the guarantee of high

operational flexibility in order to meet all necessary market requirements. .


6 Summary and Outlook There is a clear expectation that combined cycle power plants will play a major role in the

energy mix in the future. This is driven by the following factors

There is a high availability of gas resources in certain regions and the further

extension via LNG or gas grid is supported by the economic growth especially in the

emerging countries.

A drive for eco-friendly power is resulting in a need to integrate more renewable

resources, which drive the need for fast, flexible operation.

Low emissions and low operational costs demand high efficiencies.

The Optimization of the power plant as a whole unit is thereby mandatory to achieve these

ambitious targets. The application of an advanced cycle with raised steam parameters and the

application of the requested materials for highest technical loads enable the combined cycle

power plant to realize efficiencies beyond 60% while enabling fast starting, fast cycling and

dependable operation.

This paper described how this optimization has been realized in the benchmark power plant

Ulrich Hartmann, SCC5-8000H, 1S (Irsching No.4). The application of the flexible BENSON®

technology with raised steam parameters to enable highest efficiencies beyond 60% is the ideal

reference for an advanced cycle.

Figure 6.1 shows the evolution of combined cycle power plants during the last 20 years. This

constant development will also be necessary for future applications and the demand of higher

efficiencies in combination with affordable electricity will further drive the combined cycle

power plant developments.


Figure 6.1Evolution of combined cycle power plants

The sophisticated design solution as applied in the power plant in Irsching No.4 means the

highest degree of reliable and proven innovation due to an integrated development of all

relevant components from one hand.

Siemens’ technology gives answers to the regional specific requirements and offers innovative

design concepts for combined cycle power plant applications to the customer.

A world-class efficiency with operational experience of more than 12.500 EOH; CCPP-

operation without any issues, excellent start-up and operational reliability emphasize the success

story of Irsching No. 4. These outstanding references are highly appreciated by our customers.

As of today more than 15 SGT-8000H gas turbines has been sold in the 50& 60Hz market.

It’s tested, it’s validated, it’s commercially available and it’s running...


7 References [1] Japanese with steam oxidation of advanced heat resistant steel tubes in power boilers; N.Nishimura [2] Oxidschichtwachstum Bereich HD- Endüberhitzer, Stefan Rasche, 2006-04 [3] ASME material concept for HRSG with main steam parameters of 600°C/180bar; Christoph Schmitt, 2012-04 [4] Hochflexible BENSON Abhitzedampferzeuger Erfahrungen aus Irsching 4; Jan ^ Brückner, VDI Wissensforum [5] L. Balling, Dr. U. Tomschi, A. Pickard, G. Meinecke, “Fast Cycling and Grid Support Capability of Combined Cycle Power Plants to optimize the Integration of Renewable Generation into the European Grid: Live examples from projects in NL, F, UK, D”, PowerGen Europe, Amsterdam, June. 2010 [6] The Future Role of Fossil Power Generation; Andreas Pickard, Gero Meinecke, Power GEN [7] Beauftragung von FANP für AHDE-Materialuntersuchung bei 600°C FD für GUD; Tanja Seibert, Rainer Hardt; AREVA NP GmbH; 2006 [8] Dr. R. Fischer, P. Ratliff, W. Fischer, “SGT5-8000H – Product Validation at Irsching Test Center 4” Power-Gen Asia 2008 [9] Dr. S. Abens, Dr. F. Eulitz, I. Harzdorf, M. Jeanchen, W. Fischer, R. Rudolph, P. Garbett, P. Ratliff, “Planning for Extensive Validation of the Siemens H-Class Gas Turbine SGT5-8000H at the Power Plant Irsching”, ASME Power Conference, July 2009, POWER2009-81082 [10] Gas Fired Power Generation Outlook to 2020; Siemens Marketing; August 2012 [11] Ein Jahr Betrieb im Ulrich-Hartmann-Kraftwerk (Irsching 4); Lothar Balling; BKW; June 2012



8 Copyright The content of this paper is copyrighted by Siemens AG Energy Sector and is licensed only to

PennWell for publication and distribution. Any inquiries regarding permission to use the content

of this paper, in whole or in part, for any purpose must be addressed to Siemens AG Energy

Sector directly.

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