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FULL PAPER
FP_A.5_CLP_CCGT Upgrade
Major 9FA Combined Cycle Upgrade Works at Black Point Power Station for Improved
Efficiency and Lower Emissions
David Yip, Senior Project Manager, Generation Business Group, CLP Power Hong Kong Limited
(Telephone: +852 2678 4156, email: [email protected])
ABSTRACT
Black Point Power Station is one of the largest combined cycle gas turbine (CCGT) power stations in the world
consisting of 8 units of 9FA single-shaft generating units with a total capacity of 2500MW. To further improve
thermal efficiency and reduce nitrogen oxides (NOx) emission from the CCGT, a Gas Turbine Upgrade Project
was put forward commencing in 2014. Besides these performance improvements, the Project could also reduce
maintenance costs and contribute to the reliability of the units in the longer term.
This Paper is written to
describe changes to the thermodynamic cycle and the new design features that account for the upgrade
performance in efficiency, NOx emission and generating output
outline the approach and process to define the scope of works and boundary conditions based on the
examination of physical parameters, operating conditions and cycle performance parameters
present a summary of the execution pathway of the Project and the initial performance results
[Key Word] Combined cycle gas turbine, gas turbine, compressor, efficiency, NOx Emission, thermodynamic cycle,
combustion system
1. INTRODUCTION
Black Point Power Station (BPPS) is one of the largest combined cycle gas turbine (CCGT) power stations in
the world consisting of 8 units of 9FA single-shaft generating units with a total capacity of 2500MW. To
further improve thermal efficiency and reduce nitrogen oxides (NOx) emission from the CCGT, a Gas
Turbine Upgrade Project was put forward commencing in 2014.
The major scope of works in the Project includes the complete replacement of the gas turbine and
compressor, hot gas path components, combustion system, etc., and the associated modifications to other
plants including the heat recovery steam generator (HRSG) and generator transformer in the same single-
shaft configuration that are necessary to cope with the changes in operating conditions from the gas turbine.
2. PROJECT DESCRIPTIONS
2.1 DESIGN CHANGES TO THE THERMAL CYCLE
2.1.1 Configuration at Black Point Power Station (BPPS)
Each of the combined cycle units (CCGT) at BPPS is an identical configuration, where the Frame 9FA
gas turbine and the two-cylinder steam turbine drive one single generator, in a single-shaft line
arrangement. The HRSG is located at the axial exhaust of the gas turbine, in a “vertical” arrangement,
i.e. flue gas flows in a vertical direction through the HRSG, perpendicular to the arrangement of most
of the pressure piping in the HRSG.
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Figure 2.1.1 - Descriptions of the Steam Cycle in the BPPS CCGT Arrangement
The gas turbine inlet duct connects the air filters located on the turbine hall roof to the compressor inlet
plenum and incorporates a silencer. The generating shaft line is supported on an elevated reinforced
concrete foundation. The shaft line auxiliaries are located either in the turbine hall (below the
generating shaft line) or in the mechanical annex alongside the unit.
The gas turbine shaft line comprises the following major equipment:-
Air inlet
Inlet guide vanes
Compressor (rotor and casing)
Combustor
Turbine (rotor and casing)
Exhaust frame
Exhaust diffuser
Load coupling
Bearings – journal and thrust
Support frame
Instrumentation
“On-base” pipe-works
The Unit electrical and control equipment is located in an electrical annex within the turbine hall
alongside the generator.
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The physical space and footprint below the HRSG are fully utilized to accommodate the feed-water
pumps, chemical dosing, and sampling equipment and the condensate polishing plant.
2.1.2 Thermal Cycle Descriptions
The gas turbine operates in a thermal cycle that could be categorized by the Brayton cycle of which the
ideal cycle could be described in typical P-V & T-S diagrams.
Efficiency
η brayton = Ideal Brayton Cycle (thermal) efficiency
Rp = pressure ratio =
k = specific heat ratio
and Maximum WorkNET
when Rp
where Tmax (i.e. T3 limited by metallurgy) and
Tmin (i.e. T1 set by air temperature at inlet)
Figure 2.1.2 - Description of Ideal Brayton Cycle for the Gas Turbine
To produce higher cycle efficiency and generation output from the gas turbine, increasing the
compressor compression ratio and the turbine firing temperature are the typical approaches adopted
which are obvious from the Brayton cycle. But due to thermal fixation process, a higher turbine firing
temperature would favor the formation of nitrogen oxides (NOx) which is the key control emission
parameter from gas turbine of today. Therefore the selection of the new combustion system that would
provide a higher turbine temperature will have to strike a delicate balance between output, efficiency,
combustion dynamics, carbon monoxide, and NOx emission.
Finally a new type of dry low-NOx combustion system is adopted which is designed to offer the dual
benefits of higher turbine firing temperature and lower NOx emission. The extended use of pre-mix
fuel combustion was an important design and operation principle of the new dry-NOx combustion
system which would reduce the overall formation of NOx.
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2.2 ENGINEERNIG
2.2.1 Holistic Engineering Approach
An overall holistic engineering approach was taken and is depicted in Figure 2.2.1 for illustration. This
comprises the following elements and objectives.
a) Thermal loading to the HRSG and Steam Turbine should be within the original design margin of
the installed equipment as modifications to these existing equipment could make the project more
costly and not commercial viable, and impose additional project execution risks
b) The above approach also applied to electrical loading on other equipment, including the Generator
and the Generator Transformer.
c) Capacity assessments were to be carried out on all the equipment to make sure that there is no
bottom-neck and cost of modifications, if any, were factored in the overall cost-benefit evaluation
of the Project
d) All new equipment and modifications had to be fitted into the existing “footprint” of the CCGT,
and constructability review was to be carried out together with engineering
e) Potential exchangeability of new equipment for use in other CCGT units in the same BPPS was
required to be evaluated.
Figure 2.2.1 – Overall Holistic Engineering Approach
2.2.2 Front-end Engineering
Gas Turbine Engineering
Gas turbine unit rotor, compressor discharge casing and turbine casing will be engineered by the gas
turbine supplier.
The existing compressor will be redesigned for robustness, increased pressure ratio and improved surge
margin. The new compressor rotor upgrade involves an incremental increase in rotor wheel diameters
in the heavy pressure stages with a corresponding decrease in the length of the rotor blades and the
stator vanes on these stages.
The turbine rotor will be of a new design that has the special cooling slot design on the wheels.
Gas Turbine Auxiliary Systems Engineering
The major change involves the conversion of the existing dry low-NOx combustion system to a new
type combustion system. The new dry low-NOx combustion system will provide improved combustor
operability, reduced emissions levels, extended turndown capability and extended interval hardware.
This new dry low-NOx system has more number of nozzles that improve flame stability and involve
changes in mode transition.
Generator and Generator Auxiliary Systems Engineering
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The equipment supplier has conducted a review on the engineering and design changes required on the
generator and generator auxiliary systems. As the original generator capacity is adequate to cover the
increase in unit output after the gas turbine upgrade, no change is required for the generator and
generator auxiliary systems.
HRSG Engineering
The equipment supplier was engaged to identify necessary enhancement required on the HRSG to cope
with the increase in exhaust energy from the gas turbine exhaust. The following areas/issues were
reviewed by the equipment supplier:
Flow induced tube vibration
Attemperator
Flow accelerated corrosion
Inlet duct casing
HRSG casing
Expansion joint
Pressure parts
Sling system
Steam Turbine Engineering
The equipment supplier was engaged to identify necessary enhancement required on the steam turbines
and associated equipment to cope with the increase in steam flow. The following equipment were
reviewed by the equipment supplier to identify design modifications:
High Pressure (HP) steam chests
HP turbine pipework
HP valve actuators
HP rotor
HP inner and outer cylinders
HP inlet and cylinder bolting
HP blading
HP diaphragms
Low Pressure (LP) rotor
HP-LP crossover pipework
LP cylinder
LP cylinder bolting
LP blading
LP diaphragms
LP steam supply
HP & LP bypass systems
LP spray cooling system
Gland steam system
Turbine drains
Control fluid system
Lube oil system
Balance of Plant Engineering
The equipment supplier was engaged to identify necessary enhancement required on the BOP
equipment to cope with the increase in system demand. The following equipment were reviewed by the
equipment supplier to identify design modifications:
Condenser
Condensate extraction pump
HP boiler feed pump
LP boiler feed pump
Main cooling water pump
Condensate line to deaerator
Deaerator and feed water tank
Main control valves
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Electrical System Engineering
The equipment supplier was engaged to identify necessary enhancement on the Load Commutated
Inverter (LCI) equipment to cope with the Project. As a result of the higher LCI torque required after
the upgrade, the maximum current rating of the LCI needs to be increased. The existing AC reactor and
heat exchanger will be replaced.
Engineering review and design changes required on the 415V system to cope with increase in electrical
loading of the equipment after the Project were carried out.
The Generator supplier was engaged to identify necessary enhancement required on the generator
transformer cooling system to cope with the increase in unit output.
Civil Engineering
The potential civil work includes:
Furnish and construct fuel gas module support structure.
Modify gas turbine pedestals, if necessary.
Flash and weatherproof penetrations (pipe, structural steel, equipment, duct, and other
miscellaneous) in Turbine Hall, if any.
Control Philosophy
All systems shall be designed such that no single failure of any control component will cause a trip of
the unit. All transmitters and plant sensors which could directly leading to tripping of a unit shall be
triplicated and their signals shall be used in a 2 out of 3 voting logic.
2.3 SCOPE DEFINITION AND DESIGN BASIS
By adopting this holistic engineering approach, the following definition of scope of work was defined at the
closure of front-end engineering as the design basis:-
i. Replace the existing compressor rotor with a new more robust design with a slight increase in
compression ratio
ii. Complete the upgrade of all hot-gas path components (i.e. stationary and rotating blades, etc) to
the new and robust design
iii. Replace the existing dry low-NOx combustion system to a new design that promote pre-mix
combustion and enable a higher firing temperature
iv. Complete the full replacement of fuel gas control system
v. Complete necessary upgrade of all GT auxiliary systems (more than 10 systems are required to be
upgraded or modified)
vi. Complete necessary upgrade of the Load Commutated Inverter (part of the excitation system)
vii. Complete some flow measuring and control devices in the fuel quality management system
viii. Complete some modifications of steam turbine (mostly on low-pressure steam turbine cylinder)
ix. Complete some minor modifications on the HRSG (mostly some flow control devices)
x. Complete some modifications of the Generator Transformer (mostly on the cooling system and
control)
Also as part of the design basis, the upgrade unit should be able to run on gas fuels with a wider range of
composition (and Modified Wobbe Index) without the need of hardware changes. The following table is a
typical requirement of potential variability of gas fuels.
Table 2.3 – Typical Requirement of Potential Variability of Gas Fuels
Potential Gas Fuel Gas Fuel 1 Gas Fuel 2
Composition
Methane mol% ~85 ~93
Carbon Dioxide mol% ~10 ~2
Nitrogen mol% ~1 ~1
Air mol% 0 0
Total 100 100
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LHV (60oF, 1 atm.) Btu/scf 858 929
MWI at 55oC Btu/scf.R
1/2 42.7 49.1
MWI at 120oC Btu/scf.R
1/2 39.0 44.9
2.4 BOUNDARY LIMITS AND CONDITIONS
The Front-end Engineering had identified all the boundary limits and conditions for the Project. In particular
to boundary limits, the techniques of 3-D laser scanning and modeling were used extensively. This
technique had provided numerous inputs for physical dimensional analysis and general arrangement design
of various systems. As a specific application of this technique, physical clash and interference of new
equipment with the existing equipment had been effectively avoided.
3-D design model with laser scanning input
Existing equipment
Figure 2.4 – Application of 3-D Modeling, Laser Scanning and Constructability Review to avoid
interference both during installation and for permanent use
2.5 FINAL DETAILED DESIGN AND ENGINEERING
To meet the stringent reliability requirement of CLP, some rigorous studies were also carried out as part of
the final detailed design and engineering. These include the following studies:-
- Tuning of the Power System Stabilizer (PSS) of the upgrade CCGT unit
- Final bearing stress analysis based on the definitive design of the new gas turbine
- Structural and bearing capacity analysis of all new and modified plant and equipment
The PSS is a supplementary control that acts through the Automatic Voltage Regulator (AVR) of the
excitation system, and provides positive damping to generator rotor angle swings. These swings are in a
broad range of frequencies in a power system. Single-shaft CCGT such as the BPPS units have low
frequency torsional modes, which would more likely to interact with the PSS. This interaction was therefore
required to be assessed to determine whether there exists the need for torsional filters in the PSS to mitigate
the level of interaction to acceptable levels.
3. PROJECT EXECUTION
3-D design
iterative
modeling
Laser scan of existing
equipment to avoid
interference for permanent
use
Constructability review to
devise installation sequence and
fine-tune final assembly part
design
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3.1 ENGINEERING MANAGEMENT
Site engineering reports were used to provide feedback from the Project Team to the respective Contractor of
engineering problems, suggested improvements, defects and omissions which are found during construction
and commissioning. The formal reports were issued by CLP and the Contractor would have to reply by a
formal response within a short period. These report will cover though not necessarily be limited to the
following types of problems:
Interfaces
Incompatibility of Equipment and civil works
Inappropriate Equipment supplied for a required duty
Omissions and shortfalls in the design and extent of supply
Inadequacies in shipping, packing and protection
Equipment failing to fulfill design requirements
Equipment failing during construction or commissioning tests
Where CLP wishes to make modifications to the Equipment as supplied which require comment from
the Contractor or which need to be incorporated in the Contractor’s drawings.
3.2 DOCUMENT MANAGEMENT
A specific document and drawing management software system was used to manage all the technical
submissions and correspondences between the Project Team, the equipment suppliers and contractors. This
software system served as a hub with security features to control the incoming and outgoing information,
tracked changes and version control of documents, and as a central database.
3.3 MATERIAL MANAGEMENT
Discrepancy reports were used to notify the Contractor of items were damaged in transit or short shipped.
Following receipting a discrepancy report, the Contractor shall supply replacement parts or make good the
omission as soon as possible.
3.4 CONSRUCTION PLANNING AND EXECUTION
All the Contractors were required to submit their site execution programme. The programme had to indicate
the erection and commissioning logic and duration of all activities and had to be coordinated with the
delivery programme and the design submission programme. The site execution programme was required to
be expanded to a level of details that could reasonably be used by CLP to control the relevant activities on
Site. CLP developed an overall Project’s schedule that integrated all Contractor’s site execution programmes
altogether.
“Technical Advisors” are personnel and specialists supplied by the Contractor to support the execution of the
Project on Site, including but not limited to equipment transportation, equipment preservation, engineering,
materials coordination, quality management, installation, cold commissioning, hot commissioning, tuning,
testing, start-up and tests on completion.
In this Project, technical advisors were required to ensure ‘Technical Compliance’ during the execution of
work on Site, including provision of services in areas including site handling, quality assurance, quality
compliance during installation, cold commissioning, hot commissioning start-up, tuning and testing work. In
addition, Technical Advisors shall prepare, validate and counter-sign completion statements during
installation, and prior to cold and hot commissioning.
CLP also required the contractor to make the Technical Advisors available promptly at CLP’s request.
Technical Advisors with valid work permits shall be nominated a few months prior to the start of
mobilization for confirmation by CLP.
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Figure 3.4.1 – A Bird-eye View of the Site Showing Ongoing Major Construction Activities
Aerial view showing gas turbine systems installation
Internal view showing the installation of new
combustion system
Installation of “spaghetti-like” pipe-work / piping
serving each of the dual-fuel combustor
Modification works on the Fuel Gas Supply
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Associated works on the Steam Turbine
Associated works on the Generator Transformer
Figure 3.4.2 – Photos Showing Other Construction Activities
3.5 COMMISSIONING PLANNING AND EXECUTION
A clear stage-by-stage commissioning programme covering construction completion, cold commissioning,
hot commissioning until handover of the facilities’ custodianship from project execution to operations was
developed. Check-sheets, transfer of project document custodianship, and facility walk-down were typically
used to signify the completion of different stages of commissioning. Figure 3.5.1 depicts the overall process
of this stage-by-stage commissioning programme.
Figure 3.5.1 – Overall Stage-by-Stage Commissioning Programme
Also a clear division of responsibility was agreed between CLP and Contractors through the respective
contracts.
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Table 3.5.1 - Example of Division of Responsibility between CLP and Contractors
Contractor Activity / Responsibility (Examples only) CLP Activity (Examples only)
1. Mechanical Acceptance Package
Provide CLP with the Turnover Certification
Package for each system
Review – issue comments back to the
Contractor and distribute to other
parties.
2. Tie-Ins at Battery Limits (Interface Points)
Provide complete tie-in list, including the location
and method of each tie-in.
Review / Verify / Approve /
Coordinate
Provide a method statement for each tie-in point. Approve
Coordinate schedule of tie-in work with CLP Coordinate
3.6 TRAINING PRIOR TO OPERATION
The equipment suppliers were required to make available training services for CLP’s staff for any item of
Equipment supplied under the Contract, prior to commencement of operation. A training needs analysis was
carried out to match the overall operation and maintenance (O&M) needs as well as the competency
requirement of individual O&M personnel.
Venue of classroom and simulator training sessions were arranged local in Hong Kong to facilitate
involvement and participation of O&M personnel. More than 200 training man-days were recorded prior to
O&M personnel took over the facilities.
4. RESULTS AND DISCUSSIONS
The first CCGT generating unit upgrade was completed in early 2016, in a safety manner and ahead of
schedule. More about 250,000 man-hours were recorded for the first unit upgrade from project inception to
close-out without a lost-time injury, medical case or environmental incident.
The post-upgrade machine performance was satisfactory with test results generally better than the plan. For
example, the emission levels of NOx were consistently maintained to below 15 ppm (parts per million) with
an extended turndown ratio, hence allows a wider operability range for the upgraded CCGT unit to suit
system demand. Moreover, a higher level of adaptability to gas fuel with different Modified Wobbe Index
(MWI) has also been successfully tested, without any need for hardware and software changes.
Notes: Due to commercially sensitive information, only indicative figures on a
comparative basis were shown. Figures > 100% depict actual results better than planned
(i.e. 100%).
Figure 4 – Overview of the Project Performance and Benefits Realization
50%60%70%80%90%
100%110%120%130%140%150%
Safety
Schedule
Efficiency
Output
NOx Emission
Turndown
Project Performance and Benefits Realization
Plan
Actual
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5. CONCLUSIONS The Project has been successfully implemented in one of the CCGT generating unit in the Black Point Power
Station in a safe manner, slightly ahead of original schedule and with good machine performance results after
upgrade. Hence upgrading existing CCGT generating units provides a feasible and sustainable way to uprate
thermal and emission performance of the entire combined cycle fleet.
REFERENCE
Nil