Task 4 - RAE Efficiency Improvements - Public 20070424. · 2007-12-13 · HPT retrofit 2.5 357 56,000 2.2 IPT retrofit 3.5 1166 24,000 7.3 LPT retrofit 3.5 422 66,400 2.6 Combined

TECH/JJF/699/07 Date: April 2007 Issue: Final

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Engineering Report

Regulatory Authority for Energy (RAE), Greece Task 4 - Re-Powering and Efficiency

Augmentation Alternatives Overview and Evaluation

Reference Number: TECH/JJF/699/07

Date: April 2007

Issue: Final

RWE Power International

Copyright © 2007 RWE npower plc All rights reserved. No part of this document may be reproduced, stored in a retrieval system, or transmitted in any form by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of RWE npower plc. Distribution RWE npower plc is the owner of this document which must not be provided, copied or shown to any person who is not an employee of RWE npower plc, or any organisation or entity, without consideration of the commercial desirability and legal consequences of doing so. Authorisation for supply of this document external to RWE npower plc should be sought in the first instance from the Director of Engineering, npowerOne. Liability The user of this document has the obligation to employ safe working practices for any activities referred to and to adopt specific practices appropriate to local conditions. RWE npower plc shall have no liability for any loss, damage, injury, claim, expense, cost, liability or other consequence howsoever arising, as a result of use or reliance upon any information contained in or omitted from this document.

RWE Power International RWE npower plc Windmill Hill Business Park Whitehill Way, Swindon Wiltshire, England, SN5 6PB

Telephone : 44 (0)1793 877777 Fax : 44 (0)1793 892525 Web site :http://www.rwepi.com

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Registered in England & Wales: No. 3892782


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Regulatory Authority for Energy (RAE), Greece Task 4 - Re-Powering and Efficiency Augmentation Alternatives

Overview and Evaluation

Prepared for:

Regulatory Authority for Energy (RAE) Greece, Athens

Client Contact : Konstantinos Kanellopoulos

Contract No. : JXZ3746

Prepared by: L. Gillies

Reviewed by: Authorised by:

Executive Summary The Regulatory Authority for Energy (RAE) contracted RWE npower to conduct an engineering and economic assessment of all available and under development technical solutions for increasing the performance of existing lignite power plants operated by Public Power Corporation (PPC) citing associated efficiency gains and investment cost. The following topics have been included in the context of this study:-

• Typical turbine efficiency and degradation levels for 300MW power plants built from the 1970’s through to 1990’s.

• Technical description of the current solutions for retrofitting old coal-fired power stations and the associated performance improvements, including investment costs.

• Generic performance model for predicting current degraded performance (pre-retrofit) and assessing the performance improvements through retrofitting (post-retrofit).

• Case studies have been presented showing the implementation of such retrofit techniques showing the expected performance improvements, and the estimated investment cost and payback associated with each type of retrofit.

• Cycle efficiency benefits for improving boiler steam conditions


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Steam Turbine Performance Improvements In order to demonstrate the improvements achievable through a turbine retrofit, a generic model was created based on the data for Megalopoli Unit 4 (Siemens AG 300MWe plant, 1989). This study has assumed turbine degradation based on the experience of RWE npower. While this will provide a good guideline for comparison, in order to accurately quantify the benefits for PPC, performance testing of the plant will be required. Turbine improvements may be configured according to several philosophies depending on which variables are kept constant. Thus for each of the retrofit options, the following scenarios were modelled: For each of the retrofit options, three main scenarios were modelled: • Baseline: establish performance assuming 20 years operation without major

overhauls or retrofits • turbine retrofit according to a fixed unit output: this implies the same gross

generator output, same fuel input and emissions, reduced pressure before the HPT or reduced turbine swallowing capacity (in the case of an HPT retrofit)

• turbine retrofit according to fixed boiler load: this implies a constant fuel feed rate and emissions

For each of the above, all retrofit options were considered. RWE npower experience has shown that the best financial returns are achieved by increasing the electrical output. The table below summarises the technical outputs:

Turbine Heat Rate (kJ/kWh)

Gross Overall Turbine Cycle Efficiency (%)

Cylinder Efficiency

Improvement (%)

Output Improvement

(MW)

Baseline 8168 44.1 - 284.8

HPT retrofit 7972 +1.1 14.0 +7.0

IPT retrofit 8083 +0.4 5.0 +3.0

LPT retrofit 7936 +1.3 8.0 +8.3

Combined HP/IP/LP 7688 +2.7 n/a +17.8

A simple analysis of payback was performed according to a Sparkspread price assumption of £20/MWh (Sparkspread Price = Power Price – Fuel Cost – CO2 Cost). The following results were obtained:


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Assumed Retrofit

Investment Cost (£M)

Cost per kW (£/kW)

Increased MWh per Annum

(MWh)

Estimated Payback Period

(years)

HPT retrofit 2.5 357 56,000 2.2

IPT retrofit 3.5 1166 24,000 7.3

LPT retrofit 3.5 422 66,400 2.6

Combined HP/IP/LP 9.5 534 142,400 3.3

The following should, however, be noted: • The nature of the assessment of the LP turbine performance is such that there will

be a significantly greater uncertainty in both the current operational efficiency assessment and also in the evaluation of any improvements (in the order of ±2% points on LP efficiency).

• However, the efficiency / output benefits will be dependant on the pre-retrofit performance of the unit hence heat rate testing is recommended before proceeding on a steam turbine retrofit programme in order to determine the optimal solution.

• The unit output can be optimised particularly when the HP turbine cylinder is replanted as this is largely a function of the new HP turbine swallowing capacity. The unit heat rate improvement will be reasonably consistent irrespective of the design of the new HP turbine swallowing capacity.

• Further partial retrofit options may also be considered with the OEM’s as they may yield a considerable proportion of the efficiency improvement for substantially lower cost.

Efficiency Improvement through Improving Steam Conditions As an alternative to building a complete new power station, key plant items (boiler, HP and IP turbines) can be replaced to achieve similar steam conditions to new supercritical plant (typically 600/620ºC SH/RH temperatures), thus providing an increase in efficiency. Although the OEMs claim that this would only cost approximately 40% of the cost of a new power plant, the actual cost would need to be determined with a detailed engineering study set in the context of the commercial and environmental drivers for the plant.

Fuel Pre-Drying Retrofit Retrofit of the lignite pre-drying system to an existing plant is not an economic option due to the high investment required to adapt the existing plant for pre-dried lignite firing. Conversion of a lignite boiler to combustion of partially pre-dried fuel is, however, potentially an option that could be explored.


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Table of Contents 1. Introduction 6

2. Steam Turbine Performance Improvements 6 2.1. Turbine Design Developments and Upgrade Packages 6 2.2. Typical Turbine Degradation Levels 6 2.3. Potential Performance Improvement & Estimated Costs 7

3. Performance Modelling 9 3.1. General Definitions 9

3.1.1. Turbine Efficiency 9 3.1.2. HPT Swallowing Capacity 10 3.1.3. Turbine Heat Rate & Cycle Efficiency 10 3.1.4. Plant Heat Rate & Efficiency 11

3.2. Model Input Data & Assumptions 11 3.3. Steam Master Model 12 3.4. Generic Performance Model 13

3.4.1. Model Input & Output Datasheets 13

4. Retrofit Case Studies 14 4.1. 14 4.2. Degraded Performance 14 4.3. HPT Retrofit 15

4.3.1. Results and Discussion 15 4.4. IPT Retrofit 17

4.4.1. Results and Discussion 17 4.5. LPT Retrofit 18

4.5.1. Results and Discussion 18 4.6. Combined HPT, IPT and LPT Retrofit 19

4.6.1. Results and Discussion 19 4.7. Performance Payback 21 4.8. Performance Payback – Example Scenario of Payback Times 22 4.9. Station Specific Examples 22

5. Efficiency Improvement through Improving Steam Conditions 28

6. Fuel Pre-Drying Retrofit 28

7. Discussion and Conclusions 29

8. Distribution 29

Appendix A Steam Turbine Improvements 30

Figure 1 HP & IP Turbine Efficiency Definitions 31

Figure 2 LP Turbine Efficiency Definitions 32

Figure 3 300MW Heat Balance (STEAM MASTER) 33


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Figure 4 Input Datasheet for Generic Performance Model 34

Figure 5 Output Datasheet for Generic Performance Model 35

Figure 6 Heat Balance for Generic Performance Model 36

Figure 7 Degraded Performance Case Study 37

Figure 8 HPT Retrofit Case Study - Fixed Output 38

Figure 9 HPT Retrofit Case Study - Fixed Boiler Load 39

Figure 10 HPT Retrofit Case Study - 300MW 40

Figure 11 IPT Retrofit Case Study - Fixed Output 41

Figure 12 IPT Retrofit Case Study - Fixed Boiler Load 42

Figure 13 LPT Retrofit Case Study - Fixed Output 43

Figure 14 LPT Retrofit Case Study - Fixed Boiler Load 44

Figure 15 HPT, IPT & LPT Retrofit Case Study - Fixed Output 45

Figure 16 HPT, IPT & LPT Retrofit Case Study – Fixed Boiler Load 46


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RWE Power International 1. Introduction The Regulatory Authority for Energy (RAE) contracted RWE npower to conduct an engineering and economic assessment of all available and under development technical solutions for increasing the performance of existing lignite power plants operated by Public Power Corporation (PPC) citing associated efficiency gains and investment cost. In the absence of specific technical information on the PPC power plants, the performance improvement assessment has been based on a 300MW generic model developed by RWE npower. The following topics have been included in the context of this study :-

• Typical turbine efficiency and degradation levels for 300MW power plants built from the 1970’s through to 1990’s.

• Technical description of the current solutions for retrofitting old coal-fired power stations and the associated performance improvements, including investment costs.

• Generic performance model for predicting current degraded performance (pre-retrofit) and assessing the performance improvements through retrofitting (post-retrofit).

• Case studies have been presented showing the implementation of such retrofit techniques showing the expected performance improvements, and the estimated investment cost and payback associated with each type of retrofit.

• Past and current RWE npower retrofit experience. • Cycle efficiency benefits for improving boiler steam conditions

2. Steam Turbine Performance Improvements 2.1. Turbine Design Developments and Upgrade Packages Steam Turbine Manufacturers have realised significant enhancements in the reliability, design life and efficiency of steam turbines by a process of incremental design improvements in a wide range of steam turbine technologies since the 1970s. A summary listing of these together with associated benefits is provided in Appendix A.

2.2. Typical Turbine Degradation Levels Turbine degradation levels have been determined from historical performance data available for current RWE npower power plant. The degradation levels have been assessed over a 20 year operating period and the average degradation per year has been used :-

• HPT efficiency 0.50% per year • IPT efficiency 0.15% per year • LPT efficiency 0.20% per year


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RWE Power International It is worth noting that the majority of the degradation on the HP turbine will occur during the first few years of operation. However, as a general rule of thumb the above figure will give a good indication of the expected degradation. Furthermore, the degradation figures given above are based on RWE npower experience on units that have undergone routine outages and planned maintenance, and may not be representative of the degradation seen by other utilities. It is recommended that performance testing be carried out on each power plant to determine the output, heat rate and turbine efficiencies. This will allow RAE / PPC to better assess / realise the potential benefits to be gained from turbine retrofitting.

2.3. Potential Performance Improvement & Estimated Costs The greatest improvements in steam turbine designs in the last 20 years has been the development of 3D blading techniques applied specifically to the HP and IP turbine cylinders where blade heights are relatively short. But also applied to the front stages of the LP turbine cylinders modest performance improvements have been made. These developments have been achieved and demonstrated by most of the major manufacturers and they now offer very similar levels of performance.

The performance of retrofit turbine cylinders using the latest technology blading and manufacturing techniques could give the following efficiencies based upon new and clean conditions :-

HP efficiency 92%-93% IP efficiency 94%-95% LP efficiency 93%-95%

The influence of the steam turbine retrofit on the unit output and heat rate can be optimised particularly when the HP turbine cylinder is replanted. The effect on unit output will depend upon the magnitude of the efficiency improvement between the existing and retrofitted turbine but also on the design of the new HP turbine swallowing capacity. The effect on the unit heat rate will be largely dependant upon the turbine efficiency improvement and will be reasonably consistent irrespective of the design of the new HP turbine swallowing capacity.

There are effectively three options in designing the new HPT swallowing capacity :-

1. Reducing the HPT swallowing capacity and maintaining the present

electrical output takes advantage of the efficiency improvement only. This will reduce the fuel input and total emissions.

2. Reducing the HPT swallowing capacity marginally and maintaining the fuel input will increase the electrical output proportionally to the cylinder efficiency improvement. This will maintain the emissions at the current levels.

3. Increasing the HPT swallowing capacity, where spare capacity is available in the boiler will enable an electrical output increase greater than that which would have been achieved through the turbine efficiency improvement alone. This however will increase the fuel input and emissions.


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RWE Power International On IPT and LPT retrofits there are two options available :-

1. Maintaining the present electrical output will require the plant to be run in sliding pressure mode. This will take advantage of the efficiency improvement only, and will reduce the fuel input and emissions.

2. Maintaining the HPT swallowing capacity and the fuel input will increase the electrical output proportional to the efficiency improvement. This will maintain the fuel input and emissions at the current levels.

Potentially it is possible to design the IPT swallowing capacity to match the original boiler pressure. However, this in turn increases the HPT exhaust pressure and reduces the expansion work from the HP turbine. There will be a slight heatrate benefit due to the increased feedwater temperature and hence reduced boiler load. In certain circumstances it is beneficial to optimise / change the IPT capacity to obtain a specific HPT exhaust pressure conditions. A prime example of this is on boiler feed pump turbines using bled steam sourced from the HPT exhaust. If the HPT exhaust pressure is increased, the available BFPT power capability will increase as a result of the increased available expansion power.

Designing the LPT capacity to match the original boiler conditions is not a feasible option as it only changes the IPT / LPT performance split (i.e. the IPT pressure ratio and power reduces and the LPT pressure ratio and power increases), and does not give any thermodynamic performance improvement. RWE npower experience has shown that the best financial returns are achieved by increasing the electrical output. If the boilers are currently operating at or near their maximum steam raising capacity, the designs for the HP turbines should be based upon the current boiler limits. This has the added advantage of minimising any changes to the design or operation of the boiler plant and makes no impact upon the current emissions levels, whilst improving the turbine heat rate and output. The effects that such cylinder efficiency improvements will have on the unit heat rate are typically : Turbine Δ Efficiency Δ Heat Rate HP +/-1.0% -/+0.17% IP +/-1.0% -/+0.25% LP +/-1.0% -/+0.44%

Table 1 – Turbine Efficiency Heat Rate Exchange Rates The effects on the unit output will depend largely on the design of the new HP turbine swallowing capacity. If no additional fuel is burnt in the boiler then the sensitively of the improvements on the output will be the same as the heat rate factors given above. However the swallowing capacity of the HP turbine cylinder can be designed to accommodate, within reason, any desired output.


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RWE Power International This of course will mean that additional fuel must be burnt in the boiler if the capacity is increased, which will subsequently increase the total mass emissions from the boiler. An increase in capacity can only be accommodated if there is sufficient capacity within the boiler to increase the steam flow and also that the unit generator and transformer and their auxiliary systems can accommodate such an increase. The approximate cost of the turbine cylinder retrofits are estimated as follows and are based on recent RWE npower experience:

HP cylinder £2.0M to £2.5M per rotor IP cylinder £2.5M to £3.5M per rotor LP cylinder £3.0M to £3.5M per rotor

Further partial retrofit options should be considered with the OEM’s such as partial blading and internal sealing up-grades, the cost of which should be significantly less than an entire module retrofit and may yield a considerable proportion of the efficiency improvement.

3. Performance Modelling 3.1. General Definitions 3.1.1. Turbine Efficiency

The turbine efficiencies are defined as follows :-

is21

21turbine h - h

hh= −η

where

η turbine = turbine efficiency (%) h1 = inlet steam specific enthalpy (kJ/kg) h2 = exhaust steam specific enthalpy (kJ/kg) h2is = isentropic exhaust specific enthalpy (kJ/kg)

The HPT and IP turbine efficiencies are defined in two ways as shown on Figure 1 :-

• Efficiency including (inc) valves uses the isentropic outlet enthalpy

derived from the exhaust pressure and the entropy before the stop valves. The entropy before the stop valves is determined from the steam condition at the stop valves.

• Efficiency excluding (exc) valves uses the isentropic enthalpy derived from the exhaust pressure and the entropy at inlet to the turbine i.e. after valves. The entropy at the inlet is determined from the steam condition at the turbine inlet.

The LP turbine performance has been defined in the model in terms of a dry excluding leaving loss efficiency (dry excl ll). LP turbine efficiency is also defined in terms of a wet including leaving loss efficiency (wet inc LL), which is derived from the dry excluding leaving loss efficiency correcting for exhaust leaving and wetness losses.


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RWE Power International There is no throttle valve on the LPT so the including and excluding valve efficiencies do not apply in this case. Figure 2 details the LP turbine expansion line and efficiency calculations.

.

3.1.2. HPT Swallowing Capacity The HPT swallowing capacity or flow coefficient is defined by the following equation :-

22

21

111212 P - P

vPm = k

where

k12 = HP turbine swallowing capacity / flow coefficient (m2) m12 = HPT inlet steam flow (kg/sec) P1 = HPT inlet pressure (barA) P2 = HPT outlet pressure (barA) v1 = HPT inlet specific volume (m3/kg)

3.1.3. Turbine Heat Rate & Cycle Efficiency

kJ/kW.hr Output Generator Gross

Load Heat Boiler= Rate Heat Turbine Gross

hr.kW/kJOutput Generator Net

Load Heat Boiler= Rate Heat Turbine Net

%RateHeatTurbine

3600= EfficiencyCycleTurbine

where Boiler Heat Load = Superheater Heat Load + Reheater Heat Load

Net Generator Power = Gross Generator Power – Auxilliary Power


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3.1.4. Plant Heat Rate & Efficiency

kJ/kW.hr Output Generator Gross

Input Heat Fuel= Rate Heat Plant Gross

kJ/kW.hr Output Generator Net

Input Heat Fuel= Rate Heat Plant Net

%RateHeatPlant

3600= EfficiencyPlant

3.2. Model Input Data & Assumptions A generic performance model has been created based on the data supplied for the Megalopoli unit 4. This is a 300MW plant built by Siemens AG in 1989. The table below details the performance data supplied for this plant :- Parameter Units Value Nominal Output kW 300,000 Superheater Pressure barA 186.0 Superheater Temperature oC 540.0 Reheater Outlet Pressure barA 43.0 Reheater Outlet Temperature oC 538.0 Reheater Pressure Drop bar 2.5 Condenser pressure mbarA 60.3 Final Feedwater Temperature oC 250 Steam Extraction Pressures HP7 HP6 HP5 Deaerator LP3 LP2 LP1

barA 45.2 21.3 10.8 5.17 2.00 1.15

0.218

Table 2 – Megalopoli Unit 4 Design Information The turbine configuration has been assumed to be one single flow HP turbine, one single flow IP turbine and one double flow LP turbine. However, no turbine efficiency data as given for the unit so the efficiency levels used in the model have been derived from performance data available for similar sized units built in the late 1990’s :-


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Parameter Units Value

HPT efficiency (including valves) % 86.2

Throttle valve pressure loss % 3.5

HPT efficiency (excluding valves) % 88.0

IPT efficiency (including valves) % 92.1

Intercept valve pressure loss % 2.5

IPT efficiency (excluding valves) % 93.0

LPT efficiency (dry exc leaving loss) % 91.0

Table 3 – Turbine Performance The feed heating configuration has been modelled as 3 HP feed heaters, deaerator and 3 LP heaters. Bled steam pipe pressure losses and heater terminal temperature differences have been assumed based on heat balance information available for other similar power plant. The table below summarises the assumptions made in the model.

Steam Terminal

Temperature Differences

(STTD)

Drain Terminal Temperature Differences

(DTTD)

Bled Steam Pipe Pressure Losses

HP7 HP6 HP5 Deaerator LP3 LP2 LP1

4.0oC 4.0 oC 4.0 oC

- 5.0 oC 5.0 oC 5.0 oC

10.0 oC 10.0 oC 10.0 oC

- 10.0 oC 10.0 oC 10.0 oC

5.8% 5.8% 5.8% 5.0% 5.0% 5.0% 5.0%

Table 4 – Feed Heating Assumptions

The boiler feed pump efficiency has been assumed to be 83%. A generator efficiency of 98.65% has been used in the model.

3.3. Steam Master Model The above inputs have been modelled using STEAM MASTER, which is a commercially available software package used in industry for modelling power plants. Figure 3 shows the heat balance diagram for the 300MW generic model.


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RWE Power International The main performance parameters are :- Gross Generator Output 300.0MW Gross Turbine Heat Rate / Efficiency 7854kJ/kW.hr / 45.8% Auxilliary Power 15.0MW Net Generator Output 285.0MW Net Turbine Heatrate / Efficiency 8267kJ/kW.hr / 43.5% Assuming a typical boiler efficiency of 93%, the gross and net plant efficiencies are 42.6% and 40.5% respectively.

3.4. Generic Performance Model As RAE do not have STEAM MASTER software, an Excel based model of the above heat balance has been created for use in predicting the current power plant performance, and the expected performance improvements available from turbine retrofits.

3.4.1. Model Input & Output Datasheets Inputs The model requires the user to input various parameters required for the model to produce a set of results. The Input Screen is shown in Figure 4. Input values are shown in red. Alongside the input values are the original design values that were used to produce the generic 300MW model. The model has 4 modes of operation available to the user. Mode 1: Fix Generator Gross Output In this mode, the model fixes the gross output to the value specified by the user and calculates the HPT after valves flow rate, IP and LP inlet pressures and the corresponding extraction pressures. The outputs in this mode are HPT Swallowing capacity, Boiler Load and Heat Rate. Mode 2: Fix Swallowing Capacity In this mode, the model fixes the HPT swallowing capacity to the desired value and calculates the new Generator Gross Output, Heat Rate and Boiler Load. Mode 3: Boiler Load In this mode, the model fixes the boiler load to a desired value and calculates the Generator Gross Output, Heat Rate and HPT Swallowing Capacity Mode 4: Fixed Output – Sliding Pressure In this mode, the model fixes the gross output at the desired value and unlike mode 1, slides the boiler pressure to meet the desired HPT capacity. The resulting outputs are HPT before valves pressure, Heat Rate and Boiler Load.

Once the input data has been finalised, the user can click on the calculate button to produce the model results. Output Sheet The model produces an output summary which shows some of a number of output values. The output shows both the model results and the generic design results. An example of the Output page is shown in Figure 5.


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RWE Power International Heat Balance Diagram The model produces a Heat Balance diagram. The heat balance diagram, shown in Figure 6, can be switched between either showing the model results or the generic 300MW design model.

4. Retrofit Case Studies A number of retrofit case studies are described below which illustrate the theoretical minimum turbine heat rate / output improvements achievable by retrofitting the turbine cylinders. In order to show the benefits of retrofitting, some assumptions have been made on the degraded performance of the turbines

4.1. 4.2. Degraded Performance For this study it has been assumed that the unit has been running for 20 years without any major turbine overhauls or retrofits. Given the degradation rates in Section 2.2, the predicted turbine efficiencies are :-

• HPT efficiency (exc valves) 78.0% i.e. { 88% - (20 x 0.5%) } • IPT (exc valves) 89.0% • LPT efficiency (dry excl ll) 87.0%

For the purposes of this case study, it has been assumed that the HPT capacity, reference terminal conditions (boiler, reheater etc) and feed heating performance are as defined in the design cycle. Figure 7 shows the heat balance for the degraded power plant :-

• Gross Generator Output 284.8MW • Gross Turbine Heat Rate / Efficiency 8168kJ/kW.hr / 44.1% • Net Generator Output 269.8MW • Net Turbine Heat Rate / Efficiency 8622kJ/kW.hr / 41.8%

The following table of potential turbine efficiency improvements is based upon recent tendered levels received from OEMs for RWE npower retrofit projects. Further detailed discussions with the equipment suppliers will confirm the actual performance guarantees they are prepared to offer.

Degraded Retrofitted Improvement

HPT efficiency (exc valves) 78.0% 92.0% 14.0%

IPT efficiency (exc valves) 89.0% 94.0% 5.0%

LPT efficiency (dry exc LL) 87.0% 95.0% 8.0%

Table 5 – Potential improvements in cylinder efficiencies


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4.3. HPT Retrofit A post retrofit HPT efficiency (exc valve) of 92.0% has been assumed for these case studies. The following three retrofit scenarios have been modelled :-

• Fix output at 284.8MW and redesign HPT capacity at rated boiler conditions

• Re-design the HPT capacity while maintaining the boiler heat load at pre-retrofit level (2326GJ/hr or 646217kW)

• Re-design the HPT capacity for an output of 300MW.

4.3.1. Results and Discussion 1. Fixed Output For this case study the output was fixed at the datum value, with the boiler conditions remaining unchanged. The heat balance for the case study is shown in Figure 8. The model produced the following results:

HPT Retrofit Datum Δ

Gross Generator Output (MW) 284.8 284.8 0.0%

Gross Turbine Heat Rate (kJ/kWh) 7975.6 8168.0 -2.4%

Gross Turbine Cycle Efficiency (%) 45.1 44.1 +1.0

Boiler Load (kW) 631013 646217 -2.4%

HPT capacity (m2) 2.3657 2.4980 -5.3%

HPT Before Valves Pressure (barA) 186.0 186.0 0.0%

Table 6 – HPT Retrofit Scenario 1: Fixed Output

The results show that retrofitting and therefore improving the HP turbine efficiency will see an improvement in turbine heat rate along with a decrease in the required boiler load and a decrease in the HP turbine swallowing capacity. The results are due to the fact that as the efficiency of the HP turbine has increased, the required steam flow needed to produce the same output will decrease. A decrease in the required steam flow means that the boiler load will decrease. As the power output remains the same, the overall steam cycle heat rate will improve.

2. Fixed Boiler Load

For this case the boiler load was fixed to the datum value. The output and HPT before valves flow rate were calculated by the model. The heat balance for the case study is shown in Figure 9.


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RWE Power International The model produced the following results:


Gross Generator Output (MW) 291.8 284.8 +2.4%



Boiler Load (kW) 646217 646217 0.0%

HPT capacity (m2) 2.4397 2.4980 -1.3%


Table 7 – HPT Retrofit Scenario 2: Fixed Boiler Load The results show that fixing the boiler load and retrofitting the HP turbine will see an increase in the gross generator output, an improvement in the turbine heat rate and a reduction in the HP turbine swallowing capacity. The results are due the fact that the more efficient HP steam turbine will produce a larger power output with the same steam flow. The turbine heat rate will improve as the output has increased whilst the boiler load has remained fixed. 3. Fixed Output of 300MW For this case the output was fixed at 300MW and the new HPT capacity calculated. The heat balance is shown in Figure 10. The model produced the following results:





Boiler Load (kW) 663996 646217 +2.8%

HPT capacity (m2) 2.5274 2.4980 +1.2%

HPT Before Valves Pressure (barA) 186.0 186.0 0.0% Table 9 – HPT Retrofit Scenario 3: 300MW Output The results show that to produce the original 300MW, retrofitting the HP turbine, will see an improvement in turbine heat rate. The required boiler load will increase as there will be more steam required to produce the extra gross generator output contributing to the increase in HP turbine swallowing capacity.


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4.4. IPT Retrofit A post retrofit IPT efficiency (exc valve) of 94.0% has been assumed for these case studies. The following two retrofit scenarios have been modelled :-

• Fix output at 284.8MW and slide boiler pressure • Fix boiler heat load at pre-retrofit level (2326GJ/hr or 646217kW)

4.4.1. Results and Discussion

1. Fixed Output and Sliding Boiler Pressure For this case study the output was fixed at the datum value. The boiler pressure was allowed to slide to adjust for the modelled conditions. The heat balance is shown in Figure 11. The model produced the following results:

IPT Retrofit

Datum Δ




Boiler Load (kW) 640144 646217 -0.94%

HPT capacity (m2) 2.4979 2.4980 0.0%

HPT Before Valves Pressure (barA) 184.1 186.0 -1.0%

Table 10 – IPT Retrofit Scenario 1: Fixed Output and Sliding Pressure The results show that only retrofitting the IP turbine will produce a small improvement in heat rate. The flow through the HP turbine in unchanged from the datum model. The IP turbine will require less energy to produce the same amount of megawatts as prior to the retrofit so as a result the boiler pressure has been slid down. 2. Fixed Boiler Load For this case the boiler load was fixed to the datum value. The output and HPT before valves flow rate were calculated by the model. The heat balance for the case study is shown in Figure 12.


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IPT Retrofit

Datum Δ




Boiler Load (kW) 646217 646217 0.0%

HPT capacity (m2) 2.4970 2.4980 -0.04%


Table 11 – IPT Retrofit Scenario 2: Fixed Boiler Load The results show that fixing the boiler load and retrofitting the IP turbine with a more efficient turbine will improve the turbine heat rate and increase the gross generator output. This is caused by the IP turbine contributing more megawatts to the overall gross output for the same steam conditions.

4.5. LPT Retrofit A post retrofit LPT efficiency (dry exc LL) of 95.0% has been assumed for these case studies. The following two retrofit scenarios have been modelled :-

• Fix output at 284.8MW and slide boiler pressure • Fix boiler heat load at pre-retrofit level (2326GJ/hr or 646217kW)

4.5.1. Results and Discussion 1. Fixed Output and Sliding Boiler Pressure For this case study the output was fixed at the datum value. The boiler pressure was allowed to slide to adjust for the modelled conditions. The heat balance is shown in Figure 13. The model produced the following results:

LPT Retrofit

Datum Δ




Boiler Load (kW) 629629 646217 -2.6%

HPT capacity (m2) 2.4979 2.4980 0.0%

HPT Before Valves Pressure (barA) 180.9 186.0 -2.7%

Table 12 – LPT Retrofit Scenario 1: Fixed Output and Sliding Pressure


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RWE Power International The results show that, by only improving the LP efficiency, the turbine heat rate can be improved. The cause of this is down to the fact the IP turbine will require less energy to produce the same output of megawatts than it did prior to the retrofit. As a result, with the HP flow remaining the same, the boiler pressure has been reduced. This reduction in pressure will mean the boiler will not have to fire as hard, reducing the required boiler load.

2. Fixed Boiler Load

For this case the boiler load was fixed to the datum value. The output and HPT before valves flow rate were calculated by the model. The heat balance for the case study is shown in Figure 14. The model produced the following results:

LPT Retrofit

Datum Δ


Turbine Heat Rate (kJ/kWh) 7936.3 8168.0 -2.9%


Boiler Load (kW) 646217 646217 0.0%

HPT capacity (m2) 2.4973 2.4980 -0.03%


Table 13 – IPT Retrofit Scenario 2: Fixed Boiler Load The results show that by fixing the boiler load and retrofitting the LP turbine, the output and heat rate can be improved. This improvement is down to the LPT turbine contributing more megawatts to the overall gross output. The increased load for the same boiler load results in an improved turbine heat rate.

4.6. Combined HPT, IPT and LPT Retrofit This case study has assumed efficiency levels for the HPT, IPT and LPT as defined in sections 4.2, 4.3 and 4.4 respectively. The following two retrofit scenarios have been modelled :-

• Fix output at 284.8MW and redesign HPT capacity at rated boiler conditions

• Re-design the HPT capacity while maintaining the boiler heat load at pre-retrofit level (2326GJ/hr or 646217kW)

4.6.1. Results and Discussion 1. Fixed Output For this case study the output was fixed at the datum value, with the boiler conditions remaining unchanged. The heat balance for the case study is shown in Figure 15.


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Combined Retrofit

Datum Δ

Gross generator Output (MW) 284.8 284.8 0.0%



Boiler Load (kW) 609214 646217 -5.7%

HPT capacity (m2) 2.2604 2.4980 -9.5%


Table 14 – HP/IP/LPT Retrofit Scenario 1: Fixed Output

The results show that completely retrofitting the entire turbine set will see an improvement in heat rate. The boiler will need less heat input as the turbine set will be able to produce the same gross output with less steam flow prior to retrofit. With the gross generator output fixed, the reduction in required boiler heat input will see an improvement in the turbine heat rate.

2. Fixed Boiler Load For this case the boiler load was fixed to the datum value. The output and HPT before valves flow rate were calculated by the model. The heat balance for the case study is shown in Figure 16. The model produced the following results:

Combined Retrofit

Datum Δ

Gross generator Output (MW) 302.6 284.8 +6.3%



Boiler Load (kW) 646217 646217 0.0%

HPT capacity (m2) 2.4386 2.4980 -2.4%


Table 15 – HP/IP/LPT Retrofit Scenario 2: Fixed Boiler Load The results show that fixing the boiler load at the datum value and retrofitting the entire turbine set will see an increase in the overall gross generator output. This is because the more efficient turbines will each contribute more megawatts, with a fixed boiler load, increasing the overall gross output. This will result in an improved turbine heat rate.


21


4.7. Performance Payback The table below shows the cost breakdown between the HP, IP and LP improvements on the basis of no additional fuel consumption i.e. constant boiler load.

Cylinder Efficiency

Improvement (%)

Output Inprovement

(MW)

Assumed Retrofit Investment Cost

(£M)

Cost per kW

(£/kW)

HPT retrofit 14.0 7.0 2.5 357

IPT retrofit 5.0 3.0 3.5 1166

LPT retrofit 8.0 8.3 3.5 422

Table 16 – Estimated retrofit cost per kW

The most cost-effective retrofits on a £/kW basis are associated with the HP turbine cylinders. It is also clear that the benefit of the IP cylinder retrofits may be difficult to justify on an efficiency / output improvement or pay back basis. Also the LP cylinder retrofits may also be marginal on a £/kW basis, but are likely to give the largest performance improvements. The nature of the assessment of the LP turbine performance is such that there will be a significantly greater uncertainty in both the current operational efficiency assessment and also in the evaluation of any improvements. The uncertainty of assessment is in the order of ±2% points on LP efficiency. Therefore sufficient allowances would need to be included in any evaluation for LP turbine retrofits. However, the efficiency / output benefits will be dependant on the pre-retrofit performance of the unit. The degradation figures given above are based on RWE npower experience and may not be representative of the degradation seen by other utilities. It is recommended that heat rate testing be carried out on each power plant before proceeding on a steam turbine retrofit programme, as this will help identify the most cost effective power plants to retrofit.

As stated previously, further partial retrofit options should be considered with the OEM’s as they may yield a considerable proportion of the efficiency improvement.


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4.8. Performance Payback – Example Scenario of Payback Times The following is an example scenario of how a retrofit would payback.

Sparkspread price: £20/MWh (Sparkspread = Power Price – Fuel Cost – CO2 Cost)

Based off running time of: 8000 hrs/year Increase in potential MWh per year:

HP Turbine 7.0MW x 8000hrs 56000 MWh

IP Turbine 3.0MW x 8000hrs 24000 MWh

LP Turbine 8.3MW x 8000hrs 66400 MWh Assumed Cost of Turbine:

HP Turbine £2.5m

IP Turbine £3.5m

LP Turbine £3.5m Payback time for each turbine:

HP Turbine: 2.2 years

IP Turbine 7.3 years

LP Turbine 2.6 years

The above numbers are of course an example based off an approximate current sparkspread figure. If the sparkspread figure was to decrease, due to a drop in power prices or an increase in fuel or CO2 prices, the above payback times would increase. An increase in power prices or a decrease in either fuel or CO2 costs would see the above payback time decrease.

4.9. Station Specific Examples This section covers how turbine retrofits would benefit each individual power plant. The numbers quoted are improvements that would likely to be seen following a retrofit of a specific turbine. Any numbers quoted are for reference only. For actual numbers, a design study using actual plant conditions would be required including a plant heat rate test to assess the level of improvement that could be reached.

Output Improvements The assumptions for this assessment are :- • Boiler capable of supplying heat load required to produce current estimated

load capability

kantas

Rectangle


28

RWE Power International 5. Efficiency Improvement through Improving Steam

Conditions The efficiency of a steam based power cycle can be increased by increasing the inlet steam temperatures to the high pressure (HP) and intermediate pressure (IP) turbines from the super heater (SH) and reheater (RH) respectively. As an alternative to building a complete new power station, key plant items can be changed to achieve similar steam conditions. Equipment suppliers have proposed replanting the boiler and HP and IP turbines with advanced supercritical boilers and cylinders designed for typically 600/620ºC SH/RH temperatures. It has been claimed that this would only cost 40% of the cost of a new power plant but the actual cost depends greatly on the following:

• Age and condition of plant and therefore amount of old plant to be renewed; this also depends on required future life.

• Scale of plant – supercritical plant operates at higher pressures, typically 300 bar and so the steam density at HP inlet is higher and the volume flow is less. Units of less then 400MW size would require HP nozzle blocks of a very small height and therefore more subject to damage and pressure losses.

• Retrofit factor – existing design may place significant constraints on the new plant design.

• Additional emission control equipment required to meet the requirements of LCPD as interpreted by the Regulators in Greece.

Therefore to identify which option: new plant or major component replant requires a detailed engineering study set in the context of the commercial and environmental drivers for the plant.

6. Fuel Pre-Drying Retrofit Retrofit of the lignite pre-drying system to an existing plant is not advisable. The pre-dried fuel has significantly lower moisture content and higher caloric value than raw lignite. Converting an existing conventional lignite boiler to 100% dry lignite firing is not advisable, because dry lignite burns at higher temperatures and produces a smaller volume of flue gas than raw lignite. This could only be compensated by re-circulating huge quantities of cold flue gas to the combustion chamber. This requires a high investment, and would not be economical. Conversion of a lignite boiler to combustion of partially pre-dried fuel is a different matter. RWE Power is currently building a WTA pre-drying plant, which will supply the 1000 MW BoA1 power plant at Niederaußem with 25-30% pre-dried lignite. Other lignite fuelled power plants may also be able to utilise a certain portion of pre-dried lignite. However this will have to be studied in detail for each specific plant. RWE Power plans to build a power plant which will use 100% pre-dried lignite as fuel by 2011.


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7. Discussion and Conclusions Reviewing the current performance of all operational coal fired units and assessing the potential benefits that could be realised by retrofitting the existing steam turbines with the latest module designs will show that significant earnings can be made from a steam turbine retrofit investment programme. The benefits will be realised through increased electrical output, improved cycle efficiency, better availability and reduced maintenance costs. The increased output and efficiency improvements and associated capital costs have been based upon estimated budgetary figures from the equipment suppliers. Further confidence in the capital costs, performances gains and programme dates etc will be gained through a competitive tendering process, where further financial gains maybe realised through a portfolio approach to procurement. The financial analysis of the schemes is very dependent upon the market assumptions for fuel and power prices, emissions legislation and cost which can impact upon the expected life and load factors of the plant.

8. Distribution Dorian Matts (Boiler & Combustion Group) File (1)


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Appendix A Steam Turbine Improvements Component / Aspect Details of Change Benefits

Maintenance intervalsIncreased from typically 4 to 6 years for LPs and 8 to 10 years for HP & IP to 12yrs / 100,000 hours for all cylinders.

Reduced maintenance costs / plant down time.

Governing System From hydro mechanical to electronic Reduced capital cost Improved reliability, lower maintenance, improved accuracy, reduced dead band.

Over speed protection system

From mechanical bolts to triple redundancy electronic over speed protection.

Reduced capital cost, reduced maintenance (no need to remove and overhaul / calibrate mechanical over speed head), reduced need for physical over speed testing.

Simplified valve designs incorporating both stop and governor valve into a single body.

Reduced capital and maintenance costs. Use of FEA in design has minimised risk of design oversights leading to high stress areas with associated thermal fatigue problems.

Increased power oil system pressures (up for 16 bar to 40 bar for mineral oil systems) with attendant reductions in relay size

Reduced capital cost. Necessary to ensure "pipe in pipe" systems used for 40 bar pressure to minimise fire risk.

HP cylinder From three cylinder to twin cylinder. Reduced capital cost , improved flexibility.

Improved geometry Lower thermal stresses & hence improved thermal fatigue life / start-up times

Removal of central bore hole Enhanced creep life (typical y increased form 200,000 hrs to 300,000 hrs), reduced inspection requirements reduced failure risk, faster start-up times.

Improved materials - 1Chr 0.5 Mo 0.25 Va replaced by 10 chr +

Enables operation at higher steam temperatures (600 +) with associated supercritical efficiency benefits.

Provision of thermal stress monitoring systems Improved start-up times, reduced risk of plant damage (especially to HP & IP rotors) & ability to accurately monitor thermal fatigue life.

Solid forged rotors with no central bore hole replaced 70s technology of built up rotors and / or solid rotors with central bore hole.

Reduced SCC problems. Reduced routine NDT requirements.

Improved rotor materials / geometry Reduced SCC problems (esp for nuclear machines)

Coupling bolts Fitted bolts replaced by expanding bolts Reduced outage durations. Expanding bolts eliminate need to re hone bolt holes.

Banded shrouding replaced by integrally shrouded blades

Enhanced integrity by elimination of shroud detachment risk. Elimination of tenon head erosion / cracking problems. Substantial reduction in rotor maintenance / NDT works.

Removal of blade linkage devices such as lacing wire, tip struts etc

Enhanced blade integrity by elimination of cracking risk from attachment features. Removal of risk of linkage component detachment in service.

Use of cantilevered (i.e unsupported) last stage blades Elimination of blade to blade linkage devices. Ability to use longer last stage blades.

Use of laser hardened last stage LP blades instead of brazed shields Avoids problems of erosion shield detachment in service.

Increase in length of last stage blades from - typically 36" to 43"

Enables reduced number of LP cylinders required for a given MW output with attendant capital cost / maintenance savings.

Development of "3D" blading. Significant enhancement in efficiency compared to 70s vintage 2D blading. Typically, cylinder efficiencies raised from low 80s% to mid 90s%

Development of "Retractable Seals" for use in interstage glands. Seals are sprung backwards away from the casing to provide increase of circa 2.5mm in radial clearance on start-up / at low load. When MW load increases, pressure drop across seal causes segments to spring inwards towards rotor and provide design radial clearances.

Reduced rotor rubbing risk with attendant vibration / damage issues. Ability to use smaller radial clearances with attendant efficiency improvements.

Development of brush seals Enable closer radial clearances. However there have been problems associated with rotor / blade overheating. Currently considered non preferred by RWE npower.

Bearings Development of special babbit materials to support increased bearing specific loadings. Reduced risk of bearing failure in highly loaded (greater than cirac 2.5 Mpa) bearings.

PedestalsDevelopment of low friction sliding surfaces (Deva Metal, DU metal or Pan B metal all sliding on stainless steel liner plates).

Reduced "mechanical tilting" of sliding pedestals with associated avoidance of bearing load sharing problems in two bearing pedestals.

Insulation Sprayed hardset replaced by specially tailored materials Reduced maintenance spend (matts can be reused) and reduced outage duration.

High temperature bolting Heat tensioned bolts replaced by hydraulically tensioned bolts.

Faster overhauls - enables high temperature casings to be "pulled up" to facilitate distortion checks without time delays associated with old style bolt heating.

Condition monitoring Significant advances in condition monitoring equipment and techniques

Early detection of turbine integrity issued manifested in vibration behaviour especially: Bearing overheating / loading, rotor cracking, internal radial and / or axial contact, casing distortion, build errors.

Seals

Valves & relays

HP & IP rotors

Blading

LP Rotors


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Figure 1 HP & IP Turbine Efficiency Definitions


32


Figure 2 LP Turbine Efficiency Definitions


33


Figure 3 300MW Heat Balance (STEAM MASTER)

FWH7A

10.71m3038h330.7T42.75p

119.8m250.3T 208.8T

4.01 T10.03 T

FWH7B

10.71m

330.7T10.71m

119.8m250.3T 208.8T

42.75p218.8T938.8h10.71m

TTD4.01 TDCA10.03 T

FWH6A

6.018m3318h431.9T20.18p

119.8m208.8T 176.8T

4.03 T10.03 T

FWH6B

6.018m

431.9T6.018m

119.8m208.8T 176.8T

20.18p186.8T793.6h16.73m

TTD4.03 TDCA10.03 T

FWH5A

3.926m3134h338.5T10.21p

119.8m176.8T 155T

4.03 T10.06 T

FWH5B

3.926m

338.5T3.926m

119.8m176.8T 155T

10.21p165T697.5h20.66m

TTD4.03 TDCA10.06 T

DA (FWH4)

11.84m2961.5h250.2T4.928p

186.4m

4.928p151.3T637.7h239.6m

TTD-3.67 TDCA37.68 T

151.6TFWH3

5.639m2780.6h155.6T1.902p

186.4m113.6T 96.87T

1.902p107.1T448.9h5.639m

TTD5.07 TDCA10.19 T

FWH2

12.83m2691.4h108.2T1.098p

186.4m96.87T 55.99T

1.098p65.97T276.1h18.47m

TTD5.41 TDCA9.98 T

FWH1

5.114m2464.7h60.97T0.2083p

186.4m55.99T 36.39T

0.2083p46.38T194.1h24.38m

TTD4.99 TDCA9.98 T

Leak 0.4004mLeak 0.3605m

7.77836.39153.1186.4

234.3p250.3T1088.5h239.6m

0.2186p 62.02T 2464.6h 5.114m

0.2186p 62.02T 2464.6h

1.152p 108.5T 2691.5h 12.83m

1.152p 108.5T 2691.5h

2p 156T 2780.6h 5.639m

2p 156T 2780.6h

5.176p 250.6T 2961.5h 11.84m

5.176p 250.6T 2961.5h

10.81p 339.1T 3134h 7.852m

10.81p 339.1T 3134h

21.36p 432.6T 3318h 12.04m

21.36p 432.6T 3318h

45.23p 333.2T 3038h 21.43m

45.23p 333.2T 3038h

43.08p538T3528h215.1m

0.36

05m

FW

H1

Leak

2.5

04m

LPcrs 5.176p 251.1T 2962.6h 185.5m

0.0604p 36.3T 2320.6h 87.13m

0.0604p 36.3T 2320.2h 74.8m

186p540T3381h239.6m

Condenser0.15m

2.504m LP

crs0.4004m

FWH

1

HPT IPT1 LPT1x2(double flow)

LPT2x2(double flow)

197.4p250.4T1088.5h239.6m

186p 540T 3381h 239.6m

45.23p 333.2T 3038h 215.1m43.08p 538T 3528h 215.1m

0.060p36.3T2062h186.4m

0.2997p36.3T152h186.4m

0.0034m

10616m10.01T2.138p

10616m18.03T1.611p

300001 kW

3000RPM

Innogy STEAM MASTER 16.0 364 02-22-2007 14:47:32 Steam Properties: IFC-67FILE: N:\Lorne Gillies WIP\RAE Repowering Study\300MW Generic Model 7 FH.STM Cycle Schematic

p[bar], T[C], m[kg/s], h[kJ/kg]

NET POWER 285001 kWTURBINE HR 7854 kJ/kWhAUX 15000 kW

1 CONDENSER


34


Figure 4 Input Datasheet for Generic Performance Model

Generic 300MW Performance Model - Steam Turbine and Feedheating Input Sheet

ST Main Input Variables Input Data Background Model Feedheating Input Variables Input Data Background Model

HP flow coefficient m^2 2.4979 2.4979 Heater 7 pressure drop % 5.48 5.48Gross power kWe 284,825 300,000 Heater 6 pressure drop % 5.52 5.52

Heater 5 pressure drop % 5.55 5.55Stop Valve Pressure BarA 186.00 186.00 Heater 4 pressure drop % 4.80 4.79Stop Valve Temperature Deg C 540.00 540.00 Heater 3 pressure drop % 4.95 4.95HP Stop Valve Throttle % 3.49 3.49 Heater 2 pressure drop % 4.69 4.69

Heater 1 pressure drop % 4.71 4.71Reheat pressure drop % 4.75 4.75Reheat Temperature Deg C 538.00 538.00 Heater 7 STTD Deg C 4.00 4.00IP Intercept Valve Throttle % 2.51 2.51 Heater 6 STTD Deg C 4.03 4.03

Heater 5 STTD Deg C 3.99 3.99Condenser Pressure mBarA 60.00 60.00 Heater 3 STTD Deg C 5.03 5.03

Heater 2 STTD Deg C 5.37 5.37Superheater spraywater flow kg/s 0.00 0.00 Heater 1 STTD Deg C 4.97 4.97Boiler Heat Load kW 646,197 654746

Heater 7 DTTD Deg C 10.00 10.00HP efficiency (ex v/v) % 88.0 88.0 Heater 6 DTTD Deg C 10.00 10.00IP efficiency (ex v/v) % 93.0 93.0 Heater 5 DTTD Deg C 10.00 10.00LP efficiency (dry ex ll) % 90.9 90.9 Heater 3 DTTD Deg C 10.20 10.20

Heater 2 DTTD Deg C 10.00 10.00Calculation Method Heater 1 DTTD Deg C 10.00 10.00

1.0000 MBFP Efficiency % 78.93 78.93MBFP Discharge Pressure BarA 220.00 220.00

Fix Swallowing Capacity


35


Figure 5 Output Datasheet for Generic Performance Model ST Main Output Variables Model Design

Output 299980.2 300000.0Heat Rate 7858.5 7856.9Boiler Load 654830.3 654745.7HP TurbineStop Valve Pressure bar.A 186.0 186.0Stop Valve Temperature deg C 540.0 540.0Stop Valve Flow kg/s 239.6 239.6After Valves Pressure bar.A 179.5 179.5After Valves Flow kg/s 239.6 239.6Exhaust Pressure bar.A 45.2 45.2

HPT flow coefficient 2.5 2.5

Efficiency inc valves % 86.1 86.2Efficiency exc valves % 88.0 88.0

IP TurbineIntercept Valve Pressure BarA 43.0 43.1Intercept Valve Temperature DegC 538.0 538.0After Intercept Valve Pressure bar.A 42.0 42.0Exhaust Pressure bar.A 5.2 5.2

Efficiency inc valves % 92.1 92.1Efficiency exc valves % 93.0 93.0

LP TurbineLP Inlet Pressure bar.A 5.2 5.2LP Inlet Temperature deg C 251.1 251.1LP Exhaust Pressure mbar.A 60.0 60.0

Efficiency dry exc LL % 90.9 90.9


36


Figure 6 Heat Balance for Generic Performance Model


37


Figure 7 Degraded Performance Case Study


38


Figure 8 HPT Retrofit Case Study - Fixed Output


39


Figure 9 HPT Retrofit Case Study - Fixed Boiler Load


40


Figure 10 HPT Retrofit Case Study - 300MW


41


Figure 11 IPT Retrofit Case Study - Fixed Output


42


Figure 12 IPT Retrofit Case Study - Fixed Boiler Load


43


Figure 13 LPT Retrofit Case Study - Fixed Output


44


Figure 14 LPT Retrofit Case Study - Fixed Boiler Load


45


Figure 15 HPT, IPT & LPT Retrofit Case Study - Fixed Output


46


Figure 16 HPT, IPT & LPT Retrofit Case Study – Fixed Boiler Load

Documents

Task 4 - RAE Efficiency Improvements - Public 20070424. · 2007-12-13 · HPT retrofit 2.5 357 56,000 2.2 IPT retrofit 3.5 1166 24,000 7.3 LPT retrofit 3.5 422 66,400 2.6 Combined