hrsg impact assessment of gas turbine upgrades

HRSG Impact Assessment of Gas Turbine UpgradesDan Blood, Uniper TechnologiesU.S. HRSG Forum, Orlando, Florida, July 2019

Rationale for gas turbine upgrades

Understanding the impact on the water / steam cycle

Summary

Questions

Agenda

Case study: Impact of VLP upgrade for GE 9FA / 9FB

About Uniper

We are Uniper

Where we operate:

40+ countries around the world4th largest generator in Europe

Employees: 12,000Our operations:

Power Generation

Commodity Trading

Energy Storage

Energy Sales

Energy Services

Power generation, Storage, Services - Europe

Power generation - International

Commodity Trading, Energy Sales

€ 1.7 bnEBITDA

100 yearsExperience

37 GW Total generation

Main activities:

Data: Uniper Annual report 2018

Gas fired plants19.2 GW

Coal fired plants10.5 GW

Energy storageGas: 8.2 bn m3

Gas pipelines and infrastructure

Regasification

Nuclear plants1.9 GW

Hydroelectric plants 3.6 GW

Trading Energy sales (small to large clients, electricity and gas)

Services

Expertise built on engineering excellence and owner operator asset experience

We are independent of equipment and component suppliers, giving us freedom to choose the best solution for clients

We are a one-stop shop offering a broad range of services that work closely together, reducing complexity and risk for clients

Our background as an asset owner/operator gives us deep understanding of the energy industry and our clients’ needs

Expertise based on experience

1926 1957 1970 19901978 2000 2016

Innwerke

1917

UK Central Electricity Generating Board

Pipeline Engineering GmbH

VEBA KraftwerkeRuhr AG

Powergen PLCPower Technology

Energy services to over 600 power sector and industrial clients all over the world

Gas pipelines, storage & LNGInsurance, banking & finance Energy distribution

Renewables Energy from waste and biomass

Gas fired generation

Nuclear

Industrial generationCoal fired generation

Our HRSG Expertise

Why choose Uniper for your technical support?

• Over 25 years of operational experience as an ‘owner / operator’, complemented by specialist HRSG integrity and engineering knowhow

• Successful track record of optimising combined cycle and HRSG plant under challenging market conditions

• Experience of all major gas turbine OEMs • Experience of many HRSG OEMs and all design configurations• OEM independent• Expertise successfully delivered to internal and external clients globally

Typical activities on HRSG plant

New plant / early life• Owner’s Engineer role • Technical specifications, tender reviews, due diligence • Supplier quality surveillance • Identification and pursuit of warranty claims

Through life• Flexible operation assessment & optimisation• Water / steam cycle chemistry optimisation & audit• Failure investigation (with full laboratory capability)• Trip / operational incident root cause analysis• Improved pressure part design for retrofit • Advanced condition monitoring (automated alerts)

Typical activities on HRSG plant

Outage related• Technical justification for extending outage periodicity• Provision of plant-specific outage inspection scopes• Outage inspections & NDE• Component integrity assessment - ‘run / repair / replace’ • Provision of ‘safety cases’ for continued operation of

defective pressure parts• Repair advice and quality surveillance

Life extension / plant modification• Predictive thermal plant modelling of modifications• HRSG impact assessment of gas turbine upgrades• Life extension scoping and project management



Summary

Questions

Agenda


About Uniper


Site / market specific but themes are: Increased need for flexibility due to

renewables growth, commodity prices, demand volatility and demand for balancing services

Plants are displaced in the dispatch order by new market entrants

Change from hours-based to starts-based operating regime increases focus on start cost

Low power prices and uncertain environment for new-build investment

0

50

100

150

200

250

2008 2009 2010 2011 2012 2013 2014 2015

GWh/start Starts

→ Market survival → Market optimisation

Potential offered by gas turbine upgrades

GT upgrades offer a range of measures to improve market value, including: Improved speed of response (fast starts,

fast ramps, fast shutdown) Increased maximum load Increased cycle efficiency Reduced minimum load Enhanced ability to offer grid services

Such upgrades offer a CAPEX efficient means of keeping plants competitive → push back up the dispatch order

→ Increase revenue→ Generate value

Standard Combined Cycle

Open Cycle

Combined Cycle with VLP

Improved start-up time:

Reduced minimum load:

Potential offered by gas turbine upgrades

Pre-upgrade

1st upgrade

2nd upgrade17

26

74

25

52

114

0 20 40 60 80 100 120Time (min), Fuel (kNm^3)

Time Fuel

Flexibility → significant start / stop / load change performance gainsEfficiency → plant utilisation increased from 18% to >90% Capacity → additional capacity realised

Improved speed of response & reduced fuel burn:



Summary

Questions

Agenda


About Uniper

Key questions when considering GT upgrades

What will be the impact on the water / steam cycle? Will it cope with the new process conditions? Will it be safe to operate? Will the water / steam cycle restrict the full capabilities of the upgrade? Will I get the full value of my investment? Will pressure part inspection regimes need to be adjusted or enhanced? How do I understand, quantify and manage the potential risks? Will reliability be compromised? Will the GT supplier ensure that the water / steam cycle is ‘fit for purpose’?

→ A formal process is needed to understand and mitigate the risks→ GT suppliers may not offer a comprehensive assessment or may

make assumptions which are not truly valid

Uniper’s recent experience of water / steam cycle impact assessment

2011 2012 2013 2014 2015 2016 2017 2018 2019

Service Pack 7 package

Variable Load Path (VLP)

Ambient Air Injection (AAI)

Black start capability

Variable Load Path

Low Load Operating Concept

Minimum Load Reduction

Advanced Performance Package

Variable Load Path

Variable Load Path

‘Open Cycle’ start-up

Low Part Load

Variable Load Path

CO Reduction / Extended Turndown

GE 9FA GE 9FB Alstom GT26 Siemens SGT5-4000F

Fast Ramp Rate

Fast Ramp Rate

High Efficiency (HE)

Includes global ‘first of kind’ installations of VLP, AAI and HE

PLANNING TESTING IMPLEMENTATION

A structured approach to impact assessment

Initial review of risks (e.g. HAZOP or HAZID)

Quantify risks (engineeringimpactassessment)

Review impact of mode of operation (e.g. by plant modelling)

Define new mode of operation(e.g. new GT exhaust conditions)

Assess plant trials(are the impacts as predicted?)

Reassess

Undertake plant trials

Adapt / enhance maintenance & inspection regimes (e.g. pressure part integrity strategy)

Instigate risk reduction plan(e.g. modify design or operating procedures)

Implement, optimise & standardise

Thermal plant modelling

PROATES® is a whole plant modelling software package – enables impact of plant upgrades, modifications or changes in operation to be quantified

Outputs are used to inform: - HAZOP studies and resulting risk mitigation measures prior to testing - engineering impact assessment, particularly where no instrumentation- future pressure part component inspection strategy

Build site-specificmodel and validatewith real plant data

1Model the impactof the new GT exhaust conditions

2Identify differencesbetween pre- andpost- upgrade process conditions

3Calculate criticalparameters such as saturation andsuperheat margin

4

Typical PROATES model for a CCGT plant

Modelling is essential to understand the complex interactions between components and process flows!

HAZOP (HAZard & OPerability) Study

Reduces risk of potentially disastrous incidents and operational problems Identifies hazards and suitable risk controls Detailed review fulfilling international / national / company requirements Used on new plant, ageing plant and for plant modifications Uniper provides HAZOP study leadership and plant specialists to

complement knowledge and experience of site personnel (and OEM) Considers causes of process deviations, consequences and safeguards Provides recommendations with actions & responsibilities categorised as:

- ‘pre-commissioning’- ‘commissioning’ - ‘post-commissioning’

Assess plant trials

Confirm performance enhancements (compared to any guarantees)

Revalidate ‘predictive’ model with ‘real’ post-upgrade data, correcting any assumptions made as necessary (e.g. spray flow set-points)

Confirm changes to steady-state conditions across the load range

Review dynamic response, especially fast starts / shutdowns / load changes (e.g. attemperator sprays, feed flow / drum level control)- identify significant thermal transients (not always predictable!)- where possible, mitigate through operation, maintenance or design - manage any integrity implications

Re-confirm safeguards and close-out HAZOP actions

Assess plant trials – example transient

Fast start

HPS

H1Gas

Flow

HP Steam

HPS

H2

Attemperator

DrainsDrains

= TC(thermocouple)

Baseline start

TC1 (ºC) TC2 (ºC) TC3 (ºC) TC4 (ºC)

GT Load (MW) Saturation Temperature (ºC)

-102ºC in 70s,+78ºC in 120s

→ Suspected movement of undrained condensate on fast starts→ Drains may not be open for long enough to clear all condensate→ Not all post-upgrade transients are predictable!

Define pressure part integrity strategy

Post-upgradepressure part

integritystrategy

Review ofsteady-state

operating conditions

Validated modelling results

HAZOPoutputs

Review ofthermal transients

Operatingregime

Define pressure part integrity strategy - examplesComponent Risk New / Enhanced Integrity Issues Potential Mitigations

Condensate Preheater

• Minimum load: Increased risk of acid dew point deposition due to reduced stack temperature

• Re-tune CPH recirculation system• Periodic CPH tube cleaning

HP & IP Evaporators

• Minimum load: Increased risk of FAC due to reduced temperature and pressure

• Adapt FAC monitoring dependent on frequency of low-load operation

• Conduct HP / IP Steam iron monitoring • Apply improved FAC protection

HP Superheater (first stage)

• Fast starts: Increased risk of thermal fatigue damage due to large transients associated with undrained condensate

• Optimise drains to clear condensate • Undertake basic stress modelling to

inform inspection frequency

HP Superheater (second stage)

• Base load: Enhanced creep-life consumption due to increased temperature and pressure

• Consider enhanced inspection regime

IP Feed Control Valve

• Reduced risk of steam flashing across valve due to improved sub-cooling margin

• n/a

HP Bypass outlet / Cold Reheat system

• Fast shutdowns: Increased risk of thermal fatigue due to severe thermal transients –attributed to passing spray control valve and poor synchronization between HP Steam Bypass valve and spray control valve

• Maintain / upgrade spray control valve • Avoid fast shutdowns if no

commercial benefit • Improve synchronisation between HP

Bypass valve and spray control valve• Enhance condition monitoring (e.g. at

tee-piece into Cold Reheat line)



Summary

Questions

Agenda


About Uniper

GE9FA / 9FB Variable Load Path ‘VLP’ upgrade

GE / Uniper joint development project commenced in 2011 (VLP subsequently became a full commercial product offering by GE)

VLP is a GT control feature which uses IGV control to keep exhaust temperature low during start-up

Allows independent control of GT load and exhaust temperature within an ‘operating space’

Significantly decouples GT output from HRSG / ST thermal constraints

Conventional operating ‘path’:

VLP enables: → more MW in less time→ reduced fuel burn → reduced load imbalance→ reduced start emissions→ reduced start cost

VLP operating space:

HOT PATH

Plant A Hot Start Comparison

Pre-VLP VLP

Start-up Fuel Cost Savings

40%

Start Time c.130 mins c.65 mins

Plant B Hot Start Comparison

Pre-VLP VLP

Compare Op Jun’14 – May’15

143 Starts1,900 Hours

233 Starts3,100 Hours

Time to 150MW 55 mins 10 mins

GE9FA / 9FB Variable Load Path ‘VLP’ upgrade

BUT…this causes a redistribution of heat in the balance of plant – requires detailed HRSG & ST assessment

VLP Impact/Risk: HRSG Heat Balance Comparison

At same output:

Cold path reduces heat in the HP and Reheat sections and “pushes” more heat energy to the IP and LP sections of the HRSG

VLP Impact/Risk: HRSG Heat Balance Comparison

At same exhaust temp:

For the cold path, modelling predicted that the IP Evaporator would be overwhelmed (more than 100% of full load heat input)

→ the VLP operating space needed to be reduced

Cold path enables the GT to deliver more output and increases / redistributes the overall heat energy into the HRSG - particularly in the IP & LP sections

300

350

400

450

500

550

600

650

0 50 100 150 200 250

GT

Exha

ust T

empe

ratu

re (°

C)

GT Load (MW)

Control system prohibits operation in

this region

VLP: Requirement for ‘Exhaust Flow Boundary’

In some assessments, modelling predicted that the IP Safety Valve capacity would be insufficient at the extremes of the VLP operating space

Required ‘Exhaust Flow Boundary’ to be imposed for plant integrity / safety Boundary determined via plant modelling, impact assessment, HAZOP and

carefully monitored and controlled plant trials

VLP: ‘Exhaust Flow Boundary’ relaxation

Flow boundary provides a safeguard, but restricts full exploitation of VLP Desirable to relax the boundary as far as possible, subject to rigorous

assessment / implementation of additional risk control measures At one site, relaxation possible via retrofit of additional IP Drum safety valve

New IP Drum safety valve


At another site, safety valve capacity was reassessed against current design code requirements (EN12952) which supersede the original design code

Enabled a case for flow boundary relaxation to be made → ‘Relaxation test’

Relaxation test profile

Test moves beyondExhaust Flow Boundary


‘Relaxation test’ confirmed the high IP steam volumetric flow anticipated, confirming the validity of the predictive modelling

IP/HP steam volumetric flows

Beyond ExhaustFlow Boundary

126%

VLP: Example impacts / risks to Balance Of Plant Impact Typical Risks (site-specific) Potential Mitigations

Reduced sub-cooling margin at economiseroutlet

• Economiser steaming causing stagnation / reverse flow / water hammer / drum level fluctuations

• Steam flashing causing level control valve damage• Drum level instability due to loss of natural circulation• Forced circulation pump damage due to cavitation

• Use economiser bypass to improve sub-cooling margin and reduce steam flow

• Limit gas turbine exhaust flow using the Exhaust Flow Boundary

• Increase steam pressure to reduce steam volumetric flow

• Retrofit high pressure trips to HP / IP / LP drums prior to testing

• Consider probability of failure in risk assessments, given the duration of operation expected at challenging conditions

• Minimise personnel exposure• Monitor for indications of boiler /

Balance of Plant control issues or equipment damage during trials

• Enhance maintenance / inspection regimes to target areas where modelling / testing suggests enhanced rates of damage

Increased steam flow from IP & LP Evaporators

• Increased feedwater demand requiring backup pumps• Insufficient capacity of safety pressure relief valve(s)• Water carryover from drums • Insufficient ST bypass system / attemperation capacity• Change in steam turbine thrust (bearing loading)

Increased steam velocity in IP & LP steam circuits

• Droplet impingement in superheaters• Liberation of debris - risk of erosion & ST damage

Increased gas-side conditions • Stack temperature exceeds design limit



Summary

Questions

Agenda


About Uniper

Summary

GT suppliers offer upgrades to increase plant flexibility and competitiveness

Upgrades can have negative impacts on the HRSG / ST or the benefits can be restricted or negated by balance of plant limitations

Plant modelling, engineering impact assessment and HAZOP before upgrade implementation is key to understanding the risks and appropriate mitigations

A structured approach minimises risks to component integrity, process safety and operability, ensuring maximum value can be gained from the investment

Thank you!If you need any further information, please contact:

[email protected]

Uniper TechnologiesTechnology CentreRatcliffe-on-SoarNottingham, NG11 0EEUNITED KINGDOM

www.uniper.energyThis presentation may contain forward-looking statements based on current assumptions and forecasts made by Uniper SE management and other information currently available to Uniper. Various known and unknown risks, uncertainties and other factors could lead to material differences between the actual future results, financial situation, development or performance of the company and the estimates given here. Uniper SE does not intend, and does not assume any liability whatsoever, to update these forward-looking statements or to conform them to future events or developments.No representation or warranty is made or implied as to the completeness, accuracy or fitness for any particular purpose in respect to this presentation or its contents.

If you require more information about the Variable Load Path (VLP) product, please contact your local GE representative.

hrsg impact assessment of gas turbine upgrades

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