POWER January 2020 - 31

COAL
cal looping combustion projects are also
under the DOE's purview. These include
a project to design a 10-MWe combustion
pilot to validate the performance of
flameless pressurized oxy-combustion
technology for a broad range of coals on
a large pilot scale (50 MWth). The project
has heavyweight partners: Southwest
Research Institute (SwRI), ITEA, Jacobs,
EPRI, GE Global Research, and Peter
Reineck Associates.
A different pilot project spearheaded
by Babcock & Wilcox and Ohio State
University, meanwhile, will explore development
of an iron-based coal direct
chemical looping (CDCL) technology. If
successful, the small 25-kWth pilot could
be expanded into a 10-MWe pilot that
will likely be hosted by the Dover Light &
Power plant in Dover, Ohio. " Integrating
the design with existing steam cycle and
balance-of-plant equipment at a selected
host site represents a substantial step
toward commercialization of CDCL technology, "
the developers said.
Existing Coal Plants
For existing coal plants, the technology
focus appears squarely on improving efficiency
and flexibility. But as IEA CCC
analyst Dr. Malgorzata Wiatros-Motkya
explained, no
" one-size-fits-all " solution
exists to make a coal plant flexible,
mainly because flexibility requirements
differ depending on grid characteristics,
market designs, and cost factors. " For
some, achieving low minimum load in
important, while for others, it is all about
fast startup and rapid load ramp rates. "
However, flexible plant operation can
have a " significant impact " on all areas
of a coal-fired plant due to the increase
in thermal and mechanical fatigue stresses,
which could reduce the lifetimes of
many components, reduce heat rates,
and ramp up operating costs on average
by 2% to 5%, Wiatros-Motkya said.
Generally, however, flexibility can be
through
improved
new technologies,
modifying existing or adopting new operating
procedures, and staff training.
In Germany, for example, some coal
plants have implemented a minimum
load of 10% by ensuring stable combustion
through a combination of measures
(Figure 1), including optimization of coal
fineness and air-fuel flow, indirect firing,
changing the size and number of mills,
and reliable flame monitoring, she said.
Especially notable are improvements
to startup, which, as Wiatros-Motkya
explained, often involves complex and
expensive procedures because they reJanuary
2020 | POWER
quire auxiliary fuel, such as gas or oil.
One development that is already standard
in China today is plasma oil-free ignition,
which involves igniting coal with
a hot plasma flow. In China, the cost of
a 10-burner system is about $2 million,
however, and the 250-hour life of the
electrodes is still limiting, she said. More
insights could come from a DOE-backed
$4.5 million full-scale plasma ignition and
combustion stabilization demonstration
project that GE Steam Power began this
September at Rocky Mountain Power.
GE suggests the technology could save
customers " millions of dollars " by eliminating
fuel costs and providing a stable
low-load flame.
Among other " near-term " DOE-funded
projects is development of Oceanit
Laboratories' HeatX composite coating
material. Designed to reduce fouling and
promote drop-wise condensation, the
coating could be applied as part of regular
maintenance to existing in-service exchanger
units that have been pre-fouled,
as well as to seawater-fed shell and tube
heat exchangers to reduce biofouling.
Also notable is EPRI's research to determine
whether it is technically achievable
and cost-effective to upgrade subcritical
U.S. coal plants (ranging in pressure from
2,300 psi to 2,600 psi) and supercritical
plants (3,400-3,600 psi) with nine retrofit
options that raise steam temperatures
from 1,000F to 1,350F, rendering them
into ultrasupercritical and advanced ultrasupercritical
units. That project is slated
to be wrapped up in January.
The Promise of Digitalization
Advanced manufacturing, which includes
a broad range of tools, technologies, and
processes, which encompass additive
manufacturing (such as 3D printing), roll-toroll
technologies, and process intensification,
also promises to boost the efficiency
and economics of component design, and
manufacturing of new systems. Entities
around the world are researching technologies
that include advanced and flexible
electronics-which, for example, could
allow sensors to be embedded in critical,
geometrically complex components-integrated
computational materials engineering;
modularization; automation and
control; smart sensors; and novel materials
development.
At the same time, digitalization and
big data are providing deep insight into
the behavior and performance on a wide
scale, from component to overall plant
to the entire enterprise. As one of many
examples, Mitsubishi Hitachi Power Syswww.powermag.com
1.
EnBW's 1985-built Heilbronn power
plant has a once-through, tangentially fired
boiler with hard coal supplied by four bowltype
mills. Originally designed to operate at
30% minimum load, it has undergone several
modifications to achieve 10% net (15%
gross) minimum load. In 2018, it added a
5.6-MWh lithium-ion battery system to help
it better respond to fluctuating grid demand.
Courtesy: EnBW
tems in June 2018 incorporated its first
boiler combustion tuning system employing
artificial intelligence at Taiwan's
Linkou Thermal Power Plant. And GE,
which has for some years offered a boiler
module designed to improve efficiency
by working with existing distributed control
systems, is today focusing efforts
on creating digital " twins " of coal plants
based on an extensive " learning model "
library of coal plant components to determine
component health and visualize optimization
opportunities that could help
deliver up to 30% faster ramp rates.
As the IEA CCC's Dr. Wiatros-Motkya
noted, perhaps the biggest gains will
come from full automation of instrumentation
and control (I&C) systems to allow
plant operations to come ever closer to
material limitations of important components
such as superheater headers.
" Optimization of I&C is the most costeffective
way to improve plant flexibility
and should be a precondition for other
measures, " and today, the industry already
has access to various process
optimization software systems, such as
those offered by ABB, Emerson, GE,
Siemens, and Uniper, she noted. In the
not-so-distant
future, fully automated
I&Cs could be interconnected to the
industrial internet of things, allowing a
power plant to incorporate technologies,
such as virtual reality to plan outages and
simulate plant behavior; augmented reality
to support maintenance work; and big
data solutions to tap the vast potential of
predictive maintenance. ■
-Sonal Patel is a POWER senior
associate editor.
31
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POWER January 2020

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