WHITE PAPER:

HOW DIGITAL STRATEGIES IMPROVESTEAM POWER PLANT PERFORMANCE
The increase in renewables,
the low cost of natural gas insome areas, and environmental
regulations are changing theworld of steam power plants.

A NEW SET OF REALITIESSteam power plants, typically using oil or coal for fuel, havebeen a critical component of power generation around theworld for decades, but the industry is currently undergoinga profound structural transformation responding tomegatrends in politics, the economy and technology. Whilesteam power plants remain a leading source of electricalenergy, they are facing new challenges to their financial andenvironmental viability.
Rapid growth in both solar and wind generation, with theirintermittent nature, combined with an abundant supply
and low price of natural gas in many areas of the world,
have eroded the competitiveness of traditional steam

power generation. New environmental regulations for fluegas emissions, as well as for combustion by-products andwastewater, while making these plants increasingly clean,
are adding significantly to their costs for producing electricity.
These disruptive forces create challenges for the operators ofexisting steam power plants. And new steam plants must be
designed to new requirements to succeed.
These challenges are all taking place while other landmark
changes to the generating mix happen around the world.
According to the U.S. Energy Information Administration(EIA), in March 2017 monthly generation from wind and solar
exceeded 10 percent of the U.S. total power generation for
the first time, a tremendous growth from under 1 percent
in 2007 and less than 5 percent only five years ago. EIA is2

forecasting that through 2050 over 50 percent of the newgeneration additions in the U.S. will be wind and solar.
Renewable energy sources accounted for a 17.5 percent
share of the EU-28’s gross inland energy consumption in2017 and for a 29.6 percent share of the gross electricity
consumption, according to Eurostat, and a 17.5 percent
share of the Organization for Economic Co-operation andDevelopment (OECD) Asia Oceania energy production in 2019,according to the International Energy Agency. The strong
growth of wind and solar generation is certain
to continue.

Requirements of load flexibility and fuel flexibility
impose challenges for power plant designers andoperators to control and optimize the operation
settings of the combustion system and boiler to ensure
the highest possible efficiency and lowest emissions.

With increasing trade of low-cost coal around the world,
operators are optimizing cost efficiency of coal power
generation by the diversification of coal sourcing from spot
markets and accepting large variations of coal quality. On theother hand, especially in Europe, Canada and Japan, there isa trend of co-combusting biomass or even retrofitting a coalfired power plant to 100 percent wood pellet combustion.
Like coal, biomass also has large variations of quality,
depending on its origin.

Avedøre Power Station, Ørsted A/SAvedøre, Copenhagen, Denmark

KEY REQUIREMENTS TO MEET THE NEW LANDSCAPE
The shifting electricity generation marketplace requires a new level of flexibility among power generators.
Older steam plants need to be increasingly nimble to stay competitive. Plant operators must look at a variety of ways
to meet these challenges.
Fast Ramping Rate: Power output from solar and windfacilities varies from day to day, and often on an hourly oreven minute scale. Because of low implementation levelsof dedicated energy storage capacity, this means steam
power plants need to provide required load support,
ancillary services and frequency control through improved
operational response and by tapping the thermal inertia inthe steam and hot water in power plant systems.
Reduced Minimum Load: Most conventional solid-fuelboilers have a limited turndown range, originally designed
for a minimum load of around 40 percent of maximum
continuous rating (MCR). Operating in cycling mode
requires reduced minimum load without the need forfiring expensive support fuel. This would enable the plant
to respond to grid demand and avoid startups, especiallycostly cold starts that can damage equipment due tothermal fatigue.

Reduced Startup Time: Fast and smooth startups allow
a steam plant to respond to grid dispatch and maximize
generation revenue.
Fuel flexibility: Successfully accomplishing therequirements for working with variations of fuel while
effectively managing life consumption in key components
and dealing with changing or fluctuating operation
parameters requires a much higher level of digital control
strategies and data-driven life consumption modelingthan is typical in older base-loaded steam power plants.

3

MAKING SURE THE PLANT
IS READY
Part of meeting the new realities is making sure a steam
plant’s equipment is ready for the challenge. Combustion
stability is a determining factor in achieving minimum load
and ramping rate. This requires operators to evaluate mills
and burners, including testing to determine turndown ranges.
Operating at very low load means taking some of the mills
and burners out of service in combination with running thein-service mills and burners at reduced output. Evaluating
fuel flexibility and the potential to upgrade to the latest
low-NOX burner models is an option. Inspecting the flame
scanners and potentially installing upgraded flame scanners
can help avoid false trips due to weak signal strength at low
burner load. Operators may also decide to retrofit rotary
classifiers to improve fineness to enable higher
flame stability.
Other actions coal plants can take include indirect firing byinstallation of a pulverized coal bunker between the milland the burner to decouple the burner firing rate and themill output rate. This offers a new level of freedom throughdata-driven combustion control. In all cases, increased useof advanced digital control strategies and data analytics willcontribute to success.
Operators with access to sufficient supplies of natural gas
can cut startup costs by switching startup burners fromfuel oil to natural gas. Co-firing with natural gas is effective
in providing operating stability at low loads and helps avoid
costly shutdowns.
Because cycling operations can expose boiler pressure parts
to increased risk of fatigue, it is important to review heattransfer components and pressure parts. Checking flow
stability, improving attemperation system operation andcontrol range, and monitoring critical parts for temperature

Boxberg Power Station
Boxberg, Saxony, Germany

difference and life consumption accumulation are allimportant steps.

Experience in Europe proves taking thesesteps with existing fleets can provide reliable
combustion at 15 to 20 percent of MCR.
Thick-walled boiler components such as steam headers
can be the limiting factor for ramping rate. Operators
may need to replace headers with an alloy that allows higherstress. Similar to thick-walled boiler components, steam
turbine parts such as rotors, casings and valve bodies are
frequently subjected to higher levels of thermal stress fromthe aggressive operation needed to remain competitive in
operational flexibility.
Numerous plants have had success applying steam turbine
variable-startup technology, allowing interpolation between
the definitions of cold, warm and hot starts based on
measured turbine metal temperatures. Additional technology
is being developed to generate startup curves in real time by
applying multi-objective evolutionary algorithms to optimize
rotor life and fuel consumption within the constraints of rotor
stress and internal clearances.

Another key area to consider with steam
plants is the air quality control system. Plant
operators want to meet emission limits evenwhen the plant is operated at very low load
and fast ramping conditions.
Electrostatic precipitators and fabric filters can generallyaccommodate a wide range of loads, but it is important tomaintain flue gas inlet temperatures above the acid dew point
to prevent corrosion. While wet flue gas desulfurization canoperate in a wide load range, it requires a robust response andproper process control tuning. Selective catalytic reduction
systems for NOX control require special measures in somecases to maintain sufficiently high flue gas inlet temperaturesand proper functioning at low load operation.

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4ADVANCED CONTROLTECHNOLOGIESTHE ROLE
OF MAINTENANCE

As part of its TOMONI® digital power plant initiative,
Mitsubishi Power is developing new AI-based control
systems to enhance performance, efficiency and flexibility
for power plants. Analyzing large volumes of data acquired
during plant operations allows advanced analytics toprovide a range of functions, including cost optimizationand early detection of anomalies.

Cycling operations for steam power plants demand morevigorous, knowledge-based and data-driven practices.
Avoiding unplanned outages and preserving the usefullife of equipment are critical. A single unplanned unit
outage due to a boiler component failure can cost tens of
millions of dollars in lost power generation and repairs.
Risk-based maintenance programs derived from extensiveboiler inspection and maintenance experience help avoid
unplanned outages. A large metallurgical and failure
assessment database, with historical information froma wide range of designs, fuel properties and operating
conditions, can help with inspection planning, assessment
and cost-based maintenance scheduling.

AI modeling has already been deployed to manage process
values that achieve optimum boiler conditions by factoringin external parameters such as fuel cost and fuel quality
fluctuations.

LOOKING TO EUROPE
FOR PROOF
Europe was one of the first large power markets where thegrid had to absorb the variability of widespread installationof wind and solar generation capacity. Germany is a leading
renewable energy market and also has a relatively small
natural gas–fired capacity.
High natural gas prices in Germany compared to electric
market pricing means that coal-fired plants are called on for
more support in stabilizing the grid. Here are two examples
that show how, after implementing equipment and control
improvement measures, a small subcritical unit and a large
supercritical unit were able to perform.

DEEP CYCLING OPERATIONS
100%

60%
40%
20%
0%150 MW Plant, Hard Coal Weekly Load Pattern
100%% Load

80%60%
40%
20%0%

700 MW Plant, Hard Coal Daily Load Pattern

USING FLEETMONITORING AND
CONTROL TECHNOLOGIES

Fleet monitoring and diagnostics technology can be a
key enabler of more flexible and aggressive operating
regimes as well as data-driven maintenance. Mitsubishi
100%Power began system-level implementation of massive
80% power plant data acquisition and digitalization in 1997 at
60% T-Point, the fully operational and heavily instrumented gas
turbine combined cycle (GTCC) power plant at the Takasago40%
Machinery Works in Japan. In 1999, a fleet monitoring
20% and diagnostics center joined T-Point. Since then, several
0% more centers have opened around the world, including two
700 MW thatPlant,support
Hard Coal steam
Daily Load
Pattern
centers
plantsin Alabang, Philippines,and Nagasaki, Japan. Steam power plants can benefit from
Mitsubishi Power’s ability to monitor the total plant andreport in real time on boiler, steam turbine and generator
efficiency, operating conditions, creep life evaluation,
fuel flexibility, stress/life consumption, performancedegradation and other important indicators.

% Load% Load

80%

In addition to increasingly data-driven maintenanceplanning, TOMONI also offers a component condition
monitoring tool, a software application for digitalizing,
monitoring and forecasting the condition of power plantcomponents. Reliable forecasting of component conditions
can be achieved by both offline inspections during outages
and online calculation using the databases and empiricalcorrelations in the software.

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Linkou Power Plant
Linkou, New Taipei, Taiwan

Increasing use ofAI enables loweremissions and ideal
gas/air balance.
This contributes toeconomical plant
operation whileburning a range ofcoal compositions.

SOLUTIONS FOR A COMPLEXENERGY WORLDFLEXIBLE
O&M
OPTIMIZATIONOPERATIONSSOLUTIONSPERFORMANCEIMPROVEMENTIMPROVEMENTSOLUTIONSFLEXIBLEOPERATIONSOPERATIONSSOLUTIONSMitsubishi Power Remote Monitoring Center
Nagasaki, JapanDATAFOUNDATIONFOUNDATION& ENABLERS& ENABLERS

Market conditions, global prices for natural gas and LNG,
and government incentives have an impact on steam power
plant operations. Increasing reliance on intermittent energy
sources leads to higher volatility and more dynamic energy
conditions. Even companies operating small fleets needto improve their capabilities to predict electricity prices,electricity and heat demand, and weather conditions. Tools
are available in the TOMONI suite of digital solutions tooptimize the operation and maintenance of existing power
plants and help evaluate future investment needs.
Coal-fired and other steam power plants can no longer
expect to operate at base load with high capacity factors
or with constant fuel qualities. Plants need to be agile, withwide load range, fast ramping and frequent starts as wellas with high fuel flexibility—all while maintaining efficiency,
equipment durability, environmental compliance and low costof electricity.

DATA FOUNDATION& ENABLERS

O&M
OPTIMIZATIONPERFORMANCEPERFORMANCEIMPROVEMENTIMPROVEMENTSOLUTIONSFLEXIBLEFLEXIBLE
OPERATIONSOPERATIONSSOLUTIONS 

The combination of the latest digital technologies, targeted
equipment upgrades and human insights has been proven toimprove steam power plant asset performance, leading toreduced fuel cost and reductions in CO2 and other emissions.

TOMONI® is a suite of intelligent solutions that accelerates decarbonization with power plant design, O&M and system knowledge, together withstrong customer and partner collaborations. TOMONI leverages advanced controls, artificial intelligence and machine learning with multi-layered
cybersecurity to make energy systems smarter, more profitable and ultimately more autonomous on the road to a sustainable future.

O&M
OPTIMIZATION© Mitsubishi Heavy Industries, Ltd. All rights reserved. TOMONI® is a registered trademark of Mitsubishi Heavy Industries, Ltd.
Mitsubishi Power is a power solutions brand of Mitsubishi Heavy Industries.

Data Foundation & Enablers
O&M Optimization
Performance Improvement
Flexible Operations
METP-11DS08E2-A