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OCR for page 95
Technology and Environment 1989.
Pp. 9~113. Washington, DC:
National Academy Press.
Meeting the Near-Term Challenge
for Power Plants
RICHARD E. BALZHISER
This volume frames a set of emerging multidimensional challenges
to the science and technology of our energy economy and ecology. This
chapter focuses on near-term challenges facing the utilibr industry and its
engineers in accommodating to the realities of environmental, resource,
and institutional constraints. It explores technological opportunities to
maximize the value of past investments in meeting societal demands as well
as the likelihood of finding new systems and synergies that can contribute
to a healthy industry in the changing business climate in the years ahead.
The challenges the industry faces need to be understood from several
different perspectives. For convenience, these challenges can be considered
as a matrix in which the elements interact. The matrix can be understood
first by examining each element, or cell, and then considering their inter-
actions.
Near term Regional outlook Reasonably assured
(less than 25 years) (city, state, part technology
of country)
Long term Global outlook Potential future
(more than 25 years) (hemisphere, options
continent, world)
95
OCR for page 96
96
RICHARD E. BALZHISER
The first pair of cells points out the different time frames of the
challenges that must be addressed. In many aspects of energy technology,
the time required for extensive penetration of a market, often characterized
by a logistic curve (Ausubel and Lee, this volume), is 20 years or more,
because large investments in facilities and infrastructure are involved. The
utility industry is learning (with urgent need) to be able to effect some
changes more quickly, even when this large fleet of facilities is involved.
The long term opens up many more possibilities and options in technology,
but also brings many tighter constraints with respect to air, water, land
use, aesthetics, and resources. The industry must, therefore, anticipate and
move to cope with the long-term considerations even in what is developed
and applied in the near term.
The next pair of elements in the matrix contrasts regional and global
outlook Most of what is feasible and economical in energy is determined
by what is practical and convenient in a given region, whether it be a city,
a state, or a section of a country. The global view has received much
theoretical attention for nearly a century, but the influence of transregional
and transnational constraints on local decisions and choices has begun to
take effect at a practical level only in the past decade.
The third pair of matrix elements distinguishes between technology that
has a reasonably firm base in knowledge and experience, and technology
that may lead to potentially important applications but has either known
or unexpected gaps in the knowledge and experience base.
As the research arm of the U.S. electric utility industry, the Electric
Power Research Institute (EPRI) carries out development work largely in
the first two cells on the top row of the matrix, that is, near term and
regional. In the third column EPRI aims at evolutionary refinements in
known technologies, as well as developing the knowledge base for the most
promising future options. However, there is ample scope for development
even of "mature" technologies that are widely used and have long been
in textbooks. These developments are often in response to the challenges
discussed in this volume, namely, tighter environmental constraints, or
economic incentives such as an opportunity for increased efflciengy or
productivity in the production and use of energy and electricity. These
challenges often reveal gaps in the technology base, and sometimes gaps in
underlying science as well.
Mere are two other driving forces for development, almost at opposite
ends of the spectrum of technological maturity. At one end, as much as
one-third of EPRI's development is still driven by inadequacies in the
fundamental knowledge base of seemingly mature technologies. This is
especially evident as economic incentives for extension of useful life of
major equipment intensify. Extending the knowledge base to the prediction,
detection, and control or remedy for various aging and wear-out phenomena
OCR for page 97
NE4R-1~RA! CHAI~NGE FOR POWER PUS
97
is now a major goal of research and development. (Industries concerned
with aircraft, oil supply, and much of our basic infrastructure of dams,
bridges, telecommunications, and buildings also see the needs, and large
economic incentives, for safely extending useful lifetimes.)
At the other end of the technology maturity spectrum, EPRI supports
exploratory research, not necessarily tied to any existing industnal-scale
technology. This seeks to extend the knowledge base of potential future
technology or methods for the production, storage, transport, or use of
energy. These projects range from seeking new types of exotic composite
materials, through modeling and mathematics for configuration and control
of large complex computer programs, to theoretical aspects of nonneutronic
fusion processes.
All of these activities include implicit judgments about the nature of
the challenges for the utility industry, and for the national economy and the
environmental, legislative, and administrative context in which it functions.
A key point, also made by other authors in this volume, is the need
to be skeptical of forecasts. For the energy industry, skepticism means that
even reasonably stable trends or widely believed forecasts need to be used in
conjunction with contingency plans and options. For example, conventional
wisdom is that electricity demand growth will be between 1.5 and 2.5 percent
per year for the next decade at least. But 1987 and 1988 saw growth rates
roughly twice this high. As another example, natural gas is generally agreed
to be the most convenient fuel of choice for capacity additions over the next
decade. It is clean, available, and minimizes financial risk in investment.
It is convenient to install in relatively small increments for either utility or
nonutility generation and for cogeneration. It continues to show attractive
technical advances in lifetime and efficiency of turbines and in combined
gas-steam cycle systems. Nevertheless, it would be less than prudent to
neglect the possibility of price increases or supply limitations as the use of
gas increases.
The enormous resource base of domestic coal can provide a vital
insurance policy for energy resources supply. It is the nation's mainstay at
present and is likely to continue as such, provided industry can effectively
explore and demonstrate ways to make it environmentally more benign.
This environmental issue for coal divides into two parts. One is to get the
most useful lifetime out of the large national investment in existing coal
capacity; the other is to find the next generation of technology that exploits
a fundamentally different systems approach to clean coal combustion.
One development that looks especially promising involves the marriage
of coal and gas technologies. This comes about from the development of
efficient coal gasifiers that can feed a system using a gas turbine and a
combined steam cycle. Such a system can make a technically and eco-
nomically practical transition from a low-efficiency gas turbine cycle to a
OCR for page 98
98
RICHARD E. IRALZHISER
OCR for page 99
NEAR-TERA! CHALLENGE FOR POOR PITS
99
achieved without significantly compromising economic well-being. For the
utilities, the energy/environment dilemma is especially confounding because
electricity is itself such an important means to reconciliation of societal ex-
pectations, including environmental ones.
THE ROLE OF ELEc@1KICITY IN
ECONOMIC GROWTH AND PRODUCTIVITY
Over the centuries, auxiliary sources of energy have enabled man to
leverage the economic benefits deliverable from human inputs of capital,
and mental or physical labor. In the last century, electricity has amplified
the economic productivity of society, initially through widespread use of
motors as the muscle of our increasingly sophisticated factories. In recent
years, the computer revolution has built on the versatility of electricity to
move us into the electronic era, in which both man and machine work
smarter and faster, achieving still higher productivity levels. This versatility
reflects the "form value" of electrici~the ease of moving it and of turning
it on or off (Schmidt, 1986~. The form value accounts for the remarkably
rapid growth of its use, despite limited thermodynamic efficiency of the
Carnot cycle (cycle efficiencies of about 5 percent were common for the
first decade or two) and losses in transmission.
Figure 1 shows the contrasting changes in energy and electricity inten-
sity of our economy over the past 35 years. The use of electricity per unit
of gross national product (GNP) increased until about 1975, after which
it leveled off. The use of electricity has grown over the past decade at
about the same rate as the economy but has been trending slightly upward
again relative to GNP since 1985. Meanwhile, the intensity of energy use
in our economy has declined sharply over this period since 1973. In the
post-OPEC (Organization of Petroleum Exporting Countries) period, the
sharp decline comes from improved use efficiencies, in the Industrial and
transportation sectors especially, and increasing conversion to electricity
generally. The use of electricity has also reached higher efficiencies in
many conventional applications. However, there are a continuing stream
of new industrial applications for electricity and a continued growth in the
commercial sectors that have maintained the electricipr-GNP ratio, even
though the ratio of ener~v to, GNP has been falling (National Research
--A V
Council, 1986~.
Among the most important attributes of electrician emphasized by
events of the past two decades is He ability to produce it from a wide
range of resources, varying from geothermal sources and garbage on one
end of the spectrum to the atom and sunlight on the other. This flexibility
is central to the optimistic outlook for the increasing role of electricity in
meeting our energy, environmental, and economic needs.
OCR for page 100
100
28
24
of
CO 20
Cal
0 tin
SO
-
m
co
A
12
8
4
o
1950 1955 1960 1965 1970 1975 1980 1985
_
-_'
Total Energy Intensity ~
_~
/ctricity Intensity
I I , ,
RIC~4RD E. BALZHISER
0.8
0.7
0.6
0~5 c``
oo
0.4
0.3
0.2
0.1
O
Year
FIGURE 1 Changes in intensity of energy use in the U.S. economy, 195~1985. Intensity
is shown as the ratio of energy use, in thousands of British thermal units (Btu) and in
kilowatt-hours (kWh), to U.S. gross national product (GNP) in 1982 dollars.
IMPACIS OF REGULATIONS
The dramatic size of the political and legislative response to environ-
mental concerns is shown in Figure 2, which chronicles laws and regulations
aimed at controlling the effects of energy-related activity on air, water, and
land use (Yeager and Baruch, 1987~. The early challenges were the most
visible and aesthetically disturbing forms of pollution, such as smoke and
strip mining wastage. Pollution of the waterways, by both chemical and
thermal pollutants, received attention as civic and recreational interests
became affected. Finally, concerns began to focus on invisible traces of
chemical constituents in gas, liquid, and solid effluents. The sensitivity of
routine measurements has unproved from parts per million, through parts
per billion, to parts per trillion with a little more effort. These capabilities
and associated concerns led to proliferation of legislation that began in the
mid-1960s and continues virtually unabated today. The overall result is an
enormous, uncoordinated patchwork of control requirements for smoke,
air and water pollution, solid wastes, noise, and aesthetics.
The Clean Air Act (CAA), which was originally focused on human
health effects much more than environmental considerations, required a
seemingly simple unit operation, flue gas scrubbing, to remove sulfur dioxide
(SO:) from most coal plants built after 1971. These scrubbers introduced
utilities to the world of chemical or process engineering and, for many
companies, things have not been quite the same since (see Figure 3~.
Today, the nation's power plants include 62,000 megawatts of capacity with
OCR for page 101
NEAR-TERM CHALLENGE FOR POWER PLANTS
50
DO
25
o
._
o
SARA
NWpA EPM
CWA ALA
FLPMA ~RCRA
ESECA ~TSCA
ESA ~ SDWA
CZMA
NEPA ~ OSHA
NHPA ~ CM
cwna ~ WSRA
WL
RA -
RHA ~ IA
~~r~
WRA ~ WRPA
_~ FWCA Aft
_w row
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_ _ ~I I ~
1895 1915 1935 1955 1975 1995
Year
101
1973 - Endangered Species Act (ESA)
1974 - Deepwater Port Act (DPA)
1974 - Safe Drinking Water Act (SDWA)
1974 - Energy Supply and Environmental
Coordination Act (ESECA)
1976 - Toxic Substances Control Act (TSCA)
1976 - Federal Land Policy and Management Act (PUMA)
1976 - Resource Conservation and Recovery Act (RCRA)
1977 - Clean Air Act Amendments (CAAA)
1977 - Clean Water Act (CWA)
1977- Surface Mining Control and Reclamation Act
(SMCRA)
1977 - Soil and Water Resources Conservation Act
(SWRCA)
1978 - Endangered Species Act Amendments (ESM)
1978- Environmental Education Act (EEA)
1980- Comprehensive Environmental Response
Compensation and Uability Act (CERCLA)
1899 - River and Harbors Act (RHA)
1902 - Reclamation Act (RA)
1910 - Insecticide Act (IA)
191 1 - Weeks Law (WL)
1934 - Taylor Graring Act (TGA)
1937 - Flood Control Act (FCA)
1937 - Wildlife Restoration Act (WRA)
1958 - Fish and Wildlife Coordination Act (FWCA)
1964 - Wilderness Act DIVA)
1965 - Solid Waste Disposal Act (SWDA)
1965 - Water Resources Planning Act (WRPA)
1966 - National Historic Preservation Act (NHPA)
1968 - Wild and Scenic Rivers Act (VVSRA)
1969 - National Environmental Policy Act (NEPA)
1970 - Clean Air Act (CM)
1970 - Occupational Safety and Health Act (OSHA)
1972 - Water Pollution Control Act (NPCA)
1972- Marine Protection, Research and
Sanctuaries Act (MPRSA) 1982 - Nuclear Waste Policy Act (NWPA)
1972 - Coastal Zone Management Act (CZMA) 1984 - Resource Conservation and Recovery Act
1972- Home Control Act (HCA) Amendments (RCRAA)
19?2 - Federal Insecticide, Fungicide and
Rodenticide Act (FIFRA)
1972 - Parks and Waterways Safety Act (PWSA)
1972 - Marine Mammal Protection Act (MMPA)
1984 - Environmental Programs and Assistance Act (EPM)
1986 - Safe Drinking Water Act Amendments (SDWM)
1986 - Superfund Amendments and Reorganization Act
(SARA)
FIGURE 2 Growth in the number of U.S. environmental laws.
scrubbers operating and 27,000 megawatts of scrubber capacity planned
and under construction.
Congress has amended the original CAA to require a scrubber on
essentially every new coal plant and is now contemplating a retrofit re-
quirement for old coal plants to reduce acid deposition in the eastern half
of the United States. Stiff emission standards are being considered for
oxides of nitrogen (NO=) as well, posing further challenges for coal-fired
plants. Selective catalytic reduction is already commonly used on fossil
stations in Japan to achieve very low NOR emissions. Its operation on U.S.
OCR for page 102
OCR for page 103
NEAR-TERM CHALLENGE FOR POWER PI-ANTS
103
coal plants poses much more serious engineering and operating challenges
because c)f the lower grades of coals Epically used. Combustion modifica-
tion options can provide substantial NOR reductions at a fraction of the cost
of catalytic reduction. The key point with respect to further environmental
legislation aimed at air quality is the growing disparity between the price
to the U.S. economy through higher electricity costs and the marginal air
quality benefits attainable this way.
Environmental demands are not the only challenges to which utilities
must adjust. Large uncertainties in long-term fuel prices and availability
continue. Legislative and regulatory changes are reshaping the business of
electricity supply and the obligation-to-serve concept. Meanwhile, electrical
load growth continues (in some regions at phenomenal rates in 1988) and
existing capacity ages. Given the growing reluctance of utilities and their
regulators to add generating capacity, the need to sustain the performance
of existing plants is more important than ever.
The present and planned generation mix by resource is shown in Figure
4. Coal continues to be the backbone of the current mix, representing 44
percent of the capacity and supplying 55 percent of the kilowatt-hours in
1987, much of it in the nation's heartland. A surprisingly large fraction
of U.S. electricity generating capacity nationwide uses oil or gas. Because
many of these units were built in days of very low oil and gas prices, much
of this capacity is in peaking gas turbines that are relatively inefficient and
typically lack flexibility to use alternative fuels. ~day, given the higher
efficiencies available with more modern combustion turbines and combined
cycles, coupled with current low oil and gas prices, much of the planned
generating capacity for the next decade will fall into this category. It is
more difficult to anticipate and track closely, because many decisions are
being put off as long as possible.
The role of independent producers that are less subject to regulation
can bridge important gaps where demand growth is foreseen to outpace
capacitor. However, this capacity is without the obligation to serve, so a
new balance may have to be struck between reliability of services and costs,
as independent generation becomes a noticeable percentage of capacity in
any given region.
In Figure 4, the hydroelectric component remains relatively stable, and
nuclear capacity growth ends with completion of the few remaining plants
the pipeline. In the current public and regulatory climate, no chief executive
officer of a public utilibr will even consider another nuclear plant in his
remaining tenure, nor are significant additions to U.S. hydroelectric power
likely. Yet, along with intensified conservation, these are among the most
desirable options with respect to air quality or global warming concerns.
Figure 5 shows the requirements for new power generating capacity implied
by today's demand as well as 1, 2, and 3 percent compounded growth until
OCR for page 104
104
1 000
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co
co
200
o
RICI14RD E. 84LZHISER
·
~Oil: ~ & Gas
1985 1990 1995 2000 2005 2010
Year
FIGURE 4 Current and projected electric power generating capacity of U.S. utilities, by
fuel. Power generating construction by U.S. utilities is reaching completion with undefined
commitments to meet future customer load growth. SOURCES: Utility Data Institute
(19883; Federal Energy Regulatory Commission (l988~.
the year 2010. Clearly, the United States is in trouble if demand parallels
economic growth as it has historically. However, the real concern and more
serious near-term challenge to utilities is whether they can even afford to
keep some of the existing generation operating.
The shaded region in Figure 5 is a reminder that, historically, a capacity
margin of at least 17 percent has been required to service users reliably
at times of peak demand. Even if that performance might be improved
somewhat in the future with added transmission, additional capacity will
still be required.
If the aging of this capacity is considered, as shown in Figure 6,
the challenges become clear. All components of the mix will be well
advanced in age by the turn of the century. Like much of the aging
national infrastructure, it is taken for granted as we live comfortably for
the moment on the investments of the past The operating licenses of about
one-third of U.S. nuclear capacity will have expired by 2010. More than
half of fossil capacity will be more than 30 years of age by 2000. Up to
a third of U.S. hydroelectric capacity faces relicensing and, in some cases,
serious questions of safety between now and 2010. The challenges keep
coming.
The productivity and reliability of aging plants are increasingly difficult
to sustain, given typical original design lifetimes of 30 years (themselves
often optimistic) and the cyclic operation many units have experienced.
The cost of providing for modest growth is substantial, let alone having to
OCR for page 105
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OCR for page 106
106
RIC~4RD E. RA1ZHISER
replace large portions of the existing mu. Given the fuel, environmental,
and institutional uncertainties existing today, most decisions are being
deferred until absolutely necessary. Short-term factors will likely dominate,
which means some unattractive long-term prices may be payable in lowered
reliability of service and high replacement costs.
Given the popularity of prudency reviews and major disallowances of
investments after the fact by public utility commissions, there is an obvious
reluctance to invest in scrubbers on aging coal plants when these could
soon be made obsolete by still further requirements for the reduction of
emissions. Moreover, concerns about global warming could do to coal what
unlimited intervention has done to nuclear power. The investment risk of
both options far exceeds that of oil and gas, and environmental intervention
can drive up costs unpredictably. Commitments for new generation are
logically moving to combustion turbines and combined cycles where these
exposures are minimized. If U.S. gas reserves and the ability to produce
and transport gas are as abundant as the utility industry projects, that is a
reasonable path, provided it is possible to keep robust systems with some
diversity and contingency options. Developing technology opportunities
can help deal with this concern.
TRENDS IN EFFICIENCY
An important track record of engineering achievement is shown in
Figure 7, which illustrates a sustained improvement in thermal efficiency
accompanied by a continuing decline in the cost of electricity over most
of the last century. The reversal in both efficiency and cost coincide with
imposition of more stringent emission controls for particulates and SO2, as
well as for thermal discharges. Energy requirements and losses associated
with these control devices more than offset continued engineering improve-
ments in both gas and steam cycle conversion technology that had pushed
actual power plant thermal efficiencies above 40 percent.
The new challenge to which the industry is now responding is to
reverse the negative pressures on thermal efficiency and, at the same time,
improve environmental controls. Holistic approaches to past and future
environmental concerns have been pursued doggedly over the past 15
years, recently with amazing success.
CLEAN POWER FROM COAL
Leo basic technologies have been adapted for producing clean power
from coal: fluidized-bed combustion (FBC) and integrated gasification
combined cycle (IGCC). Both technologies avoid the need for scrubbers
OCR for page 107
NEAR-TERM CHALLENGE FOR POWER PLANTS
107
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18~30 1900 1920 1940 19601990
Year
500
400
300 0
200
100
FIGURE 7 Power plant evolution. As the thermal efficiency of coal-fired steam electric
generation increased from about 5 percent in the late 1800s to 35~0 percent in the late
196Os, fuel Consumption per kilowatt of power produced decreased by 85 percent. Dunng
the same period, boiler size increased from 50 kilowatts to 1,2~ megawatts. As a result,
the cost of new generating capacity dropped from $350 per kilowatt in 1920 to $130 per
kilowatt in 1967 (constant 1967 dollars), and average residential service cost dropped from
$0.25 to $0.02 per kilowatt-hour. This pattern of improved efficiency and lower energy costs
ended in the late 196Qs, which suggests that existing power plants had approached limits
set by thermodynamics, available materials, and economics. Moreover, it coincided with the
increasing priority on controlling environmental pollutants.
by internalizing means for control of emissions in the combustion process.
Waste products are more manageable and even salable.
Fluidized-bed combustion captures sulfur from burning coal in a bed
of huidized limestone; NOR formation is suppressed by virtue of lower
temperatures in the combustor (see Figure 8~. Ninetr percent of SO2
removal is achievable, and NOR levels are Epically between 200 and 300
parts per million (ppm), or well below (about half) of today's new source
performance standards.
These lower and more uniform combustion temperatures also permit
increased fuel flexibility, because combustion temperatures remain below
the temperature at which the ash melts and becomes slag. Adaptability
to a wide range of fuels is a major advantage for FBC. It helps to ensure
competitive fuel costs as prices trend upward.
These advantages are being demonstrated at a scale of approximately
80 to 160 megawatts in several key projects. Early results at Northern States
Power in Minneapolis (130 megawatts), Montana-Dakota (80 megawatts),
and Colorado-Ute (110 megawatts) have been extremely instructive and
encouraging. Projects at TVA/Duke and American Electric Power will
OCR for page 108
108
Superheaterlreheater _ 41
~ 1
Fluidized bed
of particles
surround in-bed
boiler tubes
RICHARD E. BALZHISER
High pressure steam to turbine Convection
Water in _ ~ pass
, ~
| flue gas
ecycle ·, ·~ ~ Cool
system < <, flue gas
14..
· ~ ~r
Solids
, ~ recycle
J system
Hc'`
flue aa~
FIGURE 8 Fluidized-bed combustion (IBM) of coal. Modern FBC boilers can burn even
high-sulfur coal cleanb, meeting emissions standards without scrubbed for flue gas. Forced
air suspends a mixture of coal, limestone, ash, and sand, maintaining a turbulent, fluidlike
bed in which some of the boiler tubes are immersed. Sulfur released by the burning coal
is captured as solid calcium compounds by reaction with the limestone panicles in the
fluidized bed. The excellent heat transfer within the bed limits the combustion temperature,
which avoids the formation of NOR and the melting of ash into slag that could block the
furnace. With low-sulfur fuels, a bed of mainly coal ash or sand captures most of the
residual sulfur.
explore the operational regimes of FBC pressurized to higher than atmo-
spheric pressures.
The FBC projects have been making important but evolutionary ad-
vances in combustion technology. Meanwhile, the IGCC has made what
can be considered a quantum jump forward. Successful operation of large
demonstration plants at Southern California Edison's Cool Water site in
California and, more recently, at Dow Chemical's Plaquemine, Louisiana,
plant provide the basis for clean use of coal for the next century.
The Cool Water plant has operated with high- and low-sulfur coals over
the past five years, producing a plume comparable to that of the natural
gas fired combined-cycle plant adjacent to it Emissions of SO2, NO=, and
particulates are all below federal and state requirements as shown in Table
1 (Spencer, 1986~. The vitrified solids leaving the gasified are virtually
inert, passing tough California leaching tests for contamination of drinking
OCR for page 109
HE4R-1~RM CHAI1ŁNGE FOR POWER PLANTS
TABLE 1 Cool Water Program Heat Recovery Steam Generator Stack
Emissions (Utah Coal)
Emissions
Parts per Pounds per
Million, Pounds Million
Effluent volume per Hour Btu
Permit requirement (lO)a 35b 0033
Actual test result 9 33 0.033
NOx
Permit requirement (27)a 140 0.06S
Actual test result 23 61 0.061
Particulates
Permit requirement
Actual test result
- 1 0.001
bNominal translation from pounds per hour at typical conditions.
Environmental Protection Agency permit requirements for Utah
(SUFCO) design coal correspond to 95% sulfur removal. Permit
requirement (and expected SO2 emissions) for Illinois No. 6 coal
test is 175 pounds per hour, corresponding to 97% sulfur removal.
109
water. Requirements for cooling water are less stringent in these plants
than in conventional coal plants using scrubbers. Even more impressive
has been the high level of availability (70 percent) realized in 1987 by this
first-of-a-kind plant. If carbon dioxide (CO2) must eventually be removed
from plant effluents, IGCC technology can probably best accommodate
this requirement-not without cost, but at costs below other coal-based
alternatives.
With today's gas prices and system base load capacity, simple gas
turbines for peaking are often the option of choice for most utilities. With
proper planning and siting, these units can be upgraded in several stages,
first from a simple cycle to a combined gas-and-steam cycle with an increase
in output and in thermal efficiency. Where coal becomes the fuel of choice,
an integrated gasifies can be added. This phased growth adaptability of
IGCC makes it particularly attractive to utilities at the present time.
The Fl3C and IGCC options also have application in repowering some
existing fossil units. Repowering by using either option, where feasible,
achieves SOc and NON control in addition to improving overall plant
productivity a much preferred alternative to scrubbers. The application of
FBC to the Black Dog unit of Northern States Power gained 25 megawatts
of capacity and 25 years of useful life.
OCR for page 110
110
40
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3 30
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Commercial Technology
Advanced Technology-Retrofit Plants
Advanced Technology-New Plants
o
_ W
Linings
0 10 20 30 40 50 60 70 80 90 100
:.:..::. Advanced Coal Cleaning...:..
::.: ' and Dry Scrubbing : :..
,~,~ a] a- ~e ·~e te ~ ~
RlC~4RD E. BALZHISER
it,
,~ Wet
^~ Scrubbing
- \\\\\\\\\w
Percent SO2 or NOX Emission Reduction
FIGURE 9 Control options for SO2 and NO=. Advanced coal cleaning and dry scrubbing
retrofit options (B) offer oost'ffective emission reductions at levels between present physical
coal cleaning capabilities (A1) and wet flue gas snubbing (A2) for existing commercial
power plants. Improved coal use technologies both for retrofitting (B) and for new plant
applications (C3 can combine high levels of emission and effluent control with reduced
costs and improved thermal efficiency. Levelized cost represents the present value of the
lifestyle capital, operation, and maintenance costs normalized to a uniform annual cost.
NOTE: 1 mill = 0.001 dollar.
Figure 9 shows the control options for SO2 and NOR. Options for
retrofitting existing plants win advanced technology to SO2 typically have
lower removal potential, but also lower capital costs than wet flue gas
scrubbers. In the case of NOR, similar retrofit controls now under develop-
ment in this country offer appreciable NOR reduction at lower capital and
operating costs than current commercial scrubbers.
The essence of clean coal programs is to provide long-term holistic
solutions to coal's environmental impacts, such as FBC and IGCC, and
better retrofit technology. The latter is essential to mitigate legitimate
environmental problems without forcing premature retirement of aging
units, which are still a major part of U.S. base load capacitor.
As extended lifetime performance becomes an increasingly important
objective for older fossil and nuclear units, it is necessary to look for better
indicators of declining safety margins or incipient failures of equipment.
Ideally such deficiencies or degradation effects are detected early enough
to permit the scheduling of repair work It is also preferable to detect
such conditions so as to get plants off Be line in time to avoid damaging
failures. One of the keys to maintaining performance is much broader
OCR for page 111
NE4R-TERM CHALLENGE FOR POWER PLANTS
in
._
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o
Cat
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a)
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c
111
Chimney Vibration
T G TOFS;On
Flame Flicker
T-G Vibration
Tube Leaks
O Bearing Rubs
Ultrasonic NDE
Arcing
_ Creep NDE
~ Coal Moisture Meter
.....
10 103 105 1O1O
1015 1o2o 1025
Electromagnetic Spectrum (Frequency, hertz)
FIGURE 10 Technologies for monitoring and inspection of power generation equipment
in operation. Low-ffequency devices monitor or detect low-f~quengy phenomena, such as
turbogenerator (T-G) torsion and vibration; higher frequencies are used for nondestructive
evaluation (NDE), among other purposes.
coverage of equipment with on-line diagnostics, an emerging technology of
great potential value to utilities. This involves both new sensor technologies
and computer-assisted discrimination and diagnostic tools, including expert
systems and artificial intelligence applications.
Figure 10 shows the general kinds of devices and signals that can serve
to monitor equipment while it operates. Devices use a wide spectrum of
frequencies to detect, for example, incipient failures in turbine rotors or hot
spots in a generator or combustion turbine. Avoidance of forced outage
takes on added importance as equipment is operated beyond original design
lifetimes.
CARBON DIOXIDE AND GLOBAL WARMING
Much effort has been expended over the past 15 years to deal with the
mandate to make cleaner use of coat The engineering accomplishments on
this need-by many individuals and organi7~tion~have been impressive
(Conference Report, 1987; Simbeck et aL, 1983~. Exploiting the foregoing
technology opportunities addresses all but the most recent environmental
concern-global warming. If minimization of CO2 emissions becomes a
serious objective, the United States will most certainly want to revisit the
OCR for page 112
112
RICHARD E. BALZHISER
nuclear option as well as redouble its efforts on solar energy, electric trans-
portation, and improved efficiency in the generation and use of electricity.
The United States can both engineer and afford these options. Many
emerging countries can do neither and will likely continue to rely largely
on coal and oil.
CONCLUSION
Power plants are becoming more oriented to chemical processes and,
therefore, more adaptable to environmental goals. Coal gasification not
only produces a clean fuel for combustion turbines or fuel cells but also
the building blocks for methanol and many other petrochemicals. One
should recognize that coal gasification represents the core of a coal refinery
with electricity as only one of many products available. Who will most
successfully commercialize this technology in the future? The opportunities
for adding value are large.
Given that coal can eventually be relied on for feedstock purposes, it
appears that the United States can safely turn increasingly to gas for near-
term energy needs. At current prices and with available combustion turbine
and combined-cycle technology, it is the option of economic choice not only
for peaking, but also for middle-range and some base load applications. It
can be added quickly; it operates cleanly and emits less CO2 per kilowatt-
hour than any other fossil option. It permits time to understand the issue of
global warming better without imposing costs or ineffectual CO2 removal
requirements. Finally, when gas prices rise, installation of coal gasifiers
permits adaptation and continued productive use of the power generation
investment.
The electric power industry now has a technological tool kit that
can meet most of the environmental challenges identified to date. Most
important, the industry and the nation have an engineering capability that
will continue to adapt to changes ahead.
REFERENCES
Balzhiser, R. E., and K E. Yeager. 1987. Coal-fired power plants for the future. Scientific
American 257(September):100 107.
Conference Report. 1987. Proceedings of Sixth Annual Conference on Coal Gasification,
Electric Power Research Institute Report AP-5343-SR, October 1987. Palo Alto, Calif.
Federal Energy Regulatory Commission. 1988. Data base maintained by R. Congo, Office
of Hydropower Incensing, Washington, D.C
National Research Council, Energy Engineenng Board. 1986. Electricity in Economic
Growth. Washington, D.C.: National Academy Press
Schmidt, P. 1986. Form Value of Electacibr. Pp. 199 227 in Electncity Use, Productive
Efficiency and Economic Growth, S. Schu~r and S. Sonenblum, eds Palo Alto, Calif.:
Electric Power Research Institute.
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NEAR-TERM CHAI~NGE FOR POWER PI-ANTS
113
Simbeck, D. R., R L Dickenson, and E. D. Oliver. 1983. Guide to coal gasification
systems. Electric Power Research Institute Report AP-3109, June 1983. Palo Alto,
CaliŁ
Spencer, D. F., S. B. Alpert, and H. H. Oilman. 1986. Cool Water. Demonstration of a
dean and efficient new coal technology. Science 232(May 2~:609 61~
Utility Data Institute. 1988. Edison Electric Institute power statistics data base. Washington,
D.C.
Yeager, K E., and S. B. Baruch. 1987. Environmental issues affecting coal technology: A
perspective on U.S. trends Pp. 471-502 in Annual Reviews of Energy, Vol. 12. Palo
Alto, Calif.: Annual Reviews, Inc.
Representative terms from entire chapter:
control act
