TOPICAL REPORT NUMBER 1 . MARCH1990

Tidd:

The Nations First

PFBC Combined-Cycle

Demonstration

Prepared jointly by:

U.S. Department of Energy

Assistant Secretary for Fossil Energy

American Electric Power Service Corporation

Cover photo:

Shipped up the Ohio River, the pressure

vessel passes AEPs Cardinal plant as the

barge nears Tidd, the red brick power

plant at the far right, ushering in a new era

for clean coal technologies.

Contents

Foreword 2 Plant Systems 11

Preface 3 Tidd Fact Sheet 19

Introduction 4 Project Progress 20

Benefits of PFBC Technology 5 Tidd Test Program 24

Need for the Demonstration 7 Environmental Monitoring 26

Repowering Tidd 9 Commercialization 29

Tidd Power Island 10 References 32
 With this first issue of Clean Coal

Technology, a new series of topical

Foreword reports on the demonstration program,

we hope to forge an essential link with

 Coals abundance makes it one of the potential users of the technologies and

nations most important strategic the many decision makers who play

resources in building a more secure important roles in determining the

energy future. However, the characteris- commercial applicability, viability, and

tics of coal tend to inhibit its greater use success of innovative and new energy

as a fuel. technologies. This series will provide a

 For coal to reach its full potential, forum for communicating the potential

economically competitive and advanced of the technologies and the status and

coal-using technologies and systems accomplishments of the projects.

must be developed and they must be Innovative clean coal technologies

responsive to diverse energy markets, offer tremendous potential as a part of

varied consumer needs, and stringent the solution to the many complex and

environmental requirements. integrated problems we face in our

 If there is one effort that can best rapidly changing energy arena. This

define our unique opportunity to merge series of topical reports will be one of

technological know-how with goals for a the many efforts undertaken to commucleaner environment and continued nicate vital information from the

economic prosperity, it is the Clean Coal demonstration program about technoTechnology Demonstration Program. logical opportunities that could signifi-

 A government-industry partnership, cantly reduce or perhaps eliminate the

this program is demonstrating, at threat of acid rain damage in the future,

commercial scale, a new generation of while at the same time create the

innovative coal-utilizing processes in a capability to solve the anticipated

series of showcase plants across the problems in meeting long-range energy

country. For many technologies, these requirements.

demonstrations are the culmination of 15

to 20 years of research and development

efforts that have yielded major improvements in the environmental and economic performance of coal-based energy Robert H. Gentile

technologies. For U.S. power and Assistant Secretary

energy industries, the demonstration Fossil Energy

projects represent the final step over the U.S. Department of Energy

threshold between the research laboratory and the commercial market.

This final step will occur only if the

concepts and equipment developed in

the demonstration projects are replicated

and successfully deployed into the

marketplace. Such deployment can

occur only if decision makers are fully

informed about their options.

2
release of proprietary data and controlled

operational information.

Preface Clean Coal Technology, a series of

topical reports, is one means to achieve

The Clean Coal Technology these goals.

Demonstration Program is a unique joint Prepared jointly by the industrial

venture of industry and government. It participant and the governments

is a cost-shared effort to develop program and project managers, these

advanced coal-based technologies that reports will establish a communication

offer numerous options for addressing a link among industry, federal and state

wide range of energy issues, including government, and the public. Each report

acid rain, global warming, improved will contain sufficient information to

energy efficiency, energy security, and track a projects progress, determine its

environmental quality, status, and evaluate its potential. Each

 In nearly every phase of the report lists sources of indepth informaprograms implementation, precedent tion on commercial aspects.

setting procedures have been imple- This topical report features PFBC, or

mented in joining government require- pressurized fluidized-bed combustion

ments to the commercial requirements of technology, and describes the status of

industrial participants, who by law pay one of the most advanced demonstration

at least half the costs. Cooperation has projects in the program. The project as

been essential in preparing procedures well as the report are outstanding

that enable both government and examples of what can be achieved

industry to pursue mutual and separate through the cooperation of industry and

goals. In the relationships established, government. This first issue introduces

industry is the performer, the owner, and a new concept for distributing inforthe implementer. The government mation as it is produced from the

shares in the cost, provides recommen- demonstrations.

dations, and ensures that the programs The Clean Coal Technology series is

ultimate goal commercialization of a designed to stimulate interest in the

suite of advanced coal-using technolo- program, facilitate technology transfer,

gies is achieved, and encourage commercialization by

 Some of the demonstration projects those most interested and prepared to do

are approaching the stage where useful so. The series is an evolving concept

design, construction, or operational data with the flexibility to be refined so that

are being generated. The time is the information can remain relevant and

opportune for communicating these satisfy user needs.

results to the industrial community and

to those who will participate in key

decisions concerning the commercial

application of clean coal technologies.

However, a balance must be achieved Dr. C. Lowell Miller

between the governments responsibility Associate Deputy Assistant Secretary

to see that the public reaps full value for Office of Clean Coal Technology

its share of the funding and the industrial U.S. Department of Energy

participants concerns about inadvertent

3
Tidd:

The Nations First

PFB C Combined- Cycle

Demonstration

idd, an electric generating station blades to survive in a large-scale,

Project Participants in Brilliant, Ohio, will have the coal-fired, operating plant

Ohio Power Company nations first pressurized fluAmerican Electric Power Service Corporation idized-bed combustor (PFBC) to operate • Demonstrate the ability to control

Ohio Coal Development Office in a true combined-cycle mode. And for an integrated combined-cycle

U.S. Department of Energy the first time in the U.S., this emerging system in utility operation.

clean coal technology will power an

PFBC Vendor operating, commercial-scale plant. Government and industry are jointly

ASEA Babcock Almost all facets of the project funding the $1 85-million project. The

involve pioneering efforts. Tidd will be American Electric Power Company, Inc.

Contacts the first PFBC facility in the U.S. to: (AEP) is providing $114.8 million, and

Dr. C. Lowell Miller the State of Ohios Coal Development

Associate Deputy Assistant Secretary for • Burn high-sulfur coal in full Office is contributing an additional

 Clean Coal Technology compliance with existing $10 million, for a total of $124.8 million

FE-22 environmental requirements from industry sources. To this amount,

U.S. Department of Energy the U.S. Department of Energy (DOE) is

Washington, DC 20585 • Be designed in accordance with adding $60.2 million.

(202)586-7150 U.S. codes and standards

 The project involves modernizing a

Marshall 0. Julien • Have the pressure vessel and 46-year-old power plant with technology

Vice President Communications combustor internals assembled that can burn coal efficiently while reAmerican Electric Power Service Corporation off-site and shipped via barge to moving sulfur and significantly reducing

1 Riverside Plaza the site as a complete module nitrogen pollutants, both thought to conColumbus, OH 43215 tribute to acid rain. Repowering Tidd

(614)223-1660 • Use cyclones to clean up hot gas offers the added advantage of boosting

for an operating gas turbine power output while lowering emissions.

• Demonstrate the ability of in-bed The owner of the Tidd plant is the

tube bundles and gas turbine Ohio Power Company (OPCo), an AEP

4

T
subsidiary. Electricity produced at Tidd a PFBC combined-cycle plant offers The project site is AEPs deactivated Tidd

will be dispatched by AEP into its several major advantages: power plant on the Ohio River near Brilliant,

will be dispatched by AEP into its • Low SO2 and NOx emissions Ohio. The PFBC vessel is housed in the new

transmission system. The American • Lower capital and operating costs building (black walls, white roof) adjacent to

Electric Power Service Corporation • Increased thermal efficiency the plant.

(AEPSC), another AEP subsidiary, is • Fuel flexibility

serving as the utilitys agent and is • Modularity

managing the project. The PFBCrelated equipment is being supplied by

ASEA Babcock, a partnership between More than 90% of the sulfur released

The Babcock & Wilcox Company while burning coal can be removed in

(B&W) and ASEA Brown Boveri the PFBC process. NO~ can be reduced

Carbon (ABB Carbon). by 50% to 70%.

Capital and operating costs for PFBC

are lower than for conventional coal

Benefits of PFBC fired boilers with flue gas scrubbers.

Technology Typical savings are roughly 10% of

costs. Factors contributing to these

 A clean coal technology (CCT) savings include higher heat transfer rates

capable of burning high-sulfur coal to in the boiler, smaller unit size, higher

generate electricity efficiently and eco- plant efficiency, elimination of costly

nomically, PFBC can do so while meet- add-on pollution control equipment, and

ing stringent New Source Performance easier solid waste disposal.

Standards (NSPS). Compared to a In PFBC, the rate at which heat is

conventional pulverized coal-fired plant, transferred from the bed to the tubes is

5
four to five times greater than in a quality (e.g., its heat, ash, and sulfur

conventional coal-fired boiler. PFBC content, or its fusion temperature).

combined-cycle technology offers the Modularity makes PFBC combined

potential to achieve thermal efficiencies cycle technology an attractive option for

as high as 45%, a significant improve- either repowering or new applications.

ment over the 36% efficiency of todays PFBC modules, available in two sizes,

coal-fired plants. can be installed individually or in

 The fuel flexibility offered by a multiples. The modules are suitable for

PFBC boiler enables a plant to burn a installation in existing facilities, where a

wide range of coal, regardless of its PFBC module would replace a units

6

Pressurized Fluidized-Bed Combustion

 In a fluidized-bed combustor, 1,600 0F, or almost half that of a

crushed coal with limestone or conventional boiler. This is also

dolomite (called sorbents) is the temperature range within

suspended by jets of air. This which the reaction of SO2 with

bed of coal and sorbent actually limestone and dolomite is most

floats inside the boiler, tumbling effective. Furthermore, this

in a way that resembles a boiling range is lower than the

fluid, hence the name fluidized. temperature at which substantial

Inside a PFBC boiler, pressures amounts of NO~ are formed.

are up to 16 times higher than To maintain bed temperature

normal atmospheric pressure. within the desired range, heat is

 As the coal burns, sulfur is extracted continuously by

released. The limestone acts like immersing cooling tubes in the

a chemical sponge to capture fluidized bed. Water (or another

the sulfur before it can escape working fluid) flows through the

the boiler. The sulfur-laden bundle of tubes, changes to

sorbent forms a dry waste. steam as it is heated, and is

Some of the waste is removed routed through a steam turbine to

with the bed ash through the generate electricity.

bottom of the boiler. Smaller ash Hot, pressurized flue gases

particles, or fly ash, are carried from the combustor flow through

out of the boiler and captured by cyclone d ust collectors to

cyclone dust collectors. remove particulate matter that

 Also, because the tumbling could foul, corrode, or erode the

motion of the coal enhances the blades of the gas turbine. After

burning process, combustion cleaning, the hot gases are

temperatures can be kept routed to a gas turbine and

relatively low to less than expanded to generate electricity.
boiler, or in new plants, where one or the performance of PFBC systems at

more modules would be installed, larger sizes have been based on these

 In repowering, the old boiler is earlier tests and engineering estimates.

replaced while most of the remaining Without actual operating experience,

facilities are retained, although some however, uncertainty and risk are

may be refurbished. Because the facility inherent, and this risk can be a barrier to

has already been sited, built, and commercial acceptance.

connected to the power grid, repowering The purpose of the Tidd PFBC

can be an economical alternative to demonstration is to verify expectations

constructing a new power plant. about the technologys economic, envi-

 Repowering with combined-cycle ronmental, and technical performance

PFBC technology enables an existing and to collect actual data from a utilityplant, such as Tidd, to meet environ- operated facility while it is subjected to

mental constraints while at the same real world conditions.

time producing more power than the Potential users must be confident that

original plant. Depending on the appli- the systems are not only technically In fluidized-bed combustion, crushed coal

cation, the capacity of the existing plant feasible but also viable in the real world mixed with sorbent burns while suspended

can be increased by up to 25% with with all its attendant complexities. by jets of air. Water flowing through tubes

PFBC combined-cycle technology. In 1989, DOEs Innovative Control submerged in the hot, turbulent bed changes

When a new power plant is built, Technology Advisory Panel assessed to steam which drives a steam turbine. The

PFBC modules can be installed incre- impediments to the commercialization of hot flue gases are cleaned in cyclone dust

mentally in phases, making it easier for a clean coal technologies. The Panel collectors and then routed to a gas turbine.

utility to manage capital investment

without sacrificing economies of scale.

Staged, modular expansion shortens construction time and lowers the costs

required to bring new capacity on line,

In addition, the reliability of a string of

parallel modules is typically higher than

for a single, large unit.

In sum, the many features of PFBC

combined-cycle systems are expected to

make this technology an attractive and

highly competitive option in the suite of

emerging clean coal technologies.

Need for the

Demonstration

Never before has PFBC technology

been employed in the U.S. in a commercial facility. Previous tests have been

conducted at far smaller scales and in

controlled settings. Expectations about

7
described a number of barriers relating There are costs associated with

to economic risks, regulatory concerns, bringing a technology to full commercial

and environmental problems. maturity. A new technology can have a

higher cost at first than the technology it

Economic Risks is meant to replace. Typically, a first-ofa-kind facility will have comparatively

 Economic problems and risks result higher development, testing, engineering

from various market imperfections or and design, and fabrication costs than

failures such as unrecognized value of will subsequent plants. Consequently,

research and development, imperfect the true cost savings offered by the new

regulation, imperfect knowledge, technology usually cannot be realized

environmental externalities, and unrec- until the third to fifth plant has entered

ognized public needs, the marketplace.

8

Barriers to New Technologies

In its 1989 Report to the institutional problems inherent in

Secretary of Energy Concerning rate regulation today cause

Commercialization Incentives, utilities to be reluctant to spend

DOEs Innovative Control large amounts of money for new

Technology Advisory Panel generation projects of any kind,

summarized barriers to clean including CCTs. Also siting and

coal technologies as follows: permitting regulations can be

 These new technologies duplicative and overly complex.

face potential impediments of Some environmental air quality

three types. regulations may also potentially

 First, because these constrain new CCT demonstratechnologies are new, and in tion and deployment, despite the

many cases have yet to be fact that both the regulations and

demonstrated at the commercial the CCT technologies have the

scale, engineering estimates of goal of a cleaner environment.

actual cost and performance are Some regulations or policies may

still uncertain. Thus, it is too create uncertainties because of

early to expect utilities or other lack of clarity, while others provide

firms to build these technologies CCT demonstration with

on a commercial scale without inadequate time for compliance.

some reduction of economic risk. In addition, in some cases,

 Secondly, despite the best environment permitting and/or

efforts of regulators to properly approval may be subject to delays

balance the interests of electric which increase project uncertainty

ratepayers and shareholders, and/or costs.
Developers of pre-commercial CCT Developers may be reluctant to proceed

plants risk higher than expected project if uncertain about how current regulacapital costs and operating costs and tions will be enforced or unsure as to

lower than expected performance. whether or not the project would comply

with future regulations.

Regulatory Concerns Inflexibility of regulations can also

present barriers. For example, if a utility

 Protecting ratepayer interests while at voluntarily improves controls and

the same time providing a reasonable reduces emissions at a power plant,

business environment for utilities is a requirements for even tighter controls

complex and difficult task, one in which could be triggered. Because emission

balance is very hard to achieve, waivers might not be allowed or might

 The Innovative Control Technology be restricted, units that just miss complyAdvisory Panel observed that problems ing with newer, tighter standards could

faced by utilities and other regulated de- be faced with substantial added expense

velopers of CCT projects tend to involve in order to comply.

electricity rate regulation and/or the state

siting and project approval process.

 Rate regulation can significantly

impede CCT investment if developers Repowering Tidd

are concerned or uncertain about the

potential for cost disallowances, inade- Originally commissioned in 1945, the

quate rates of return, financial effects of Tidd plant was prematurely retired in the

delayed construction projects, and regu- late 1 970s because it was unable to meet

latory lag. In addition, complex and emission standards. At that time, OPCo

lengthy siting and project approval determined that it would not have been

processes may be concerns. economical to retrofit the plant with the

necessary controls to meet the standards.

Environmental Problems However, Tidd is now being repowered

with an emerging clean coal technology.

Ironically, CCT demonstrations are The old pulverized coal-fired boiler is

subject to a number of environmental being replaced with a PFBC boiler, and

impediments. The problem is not due to a gas turbine is being added. The PFBC

the intent of the environmental regula- combined-cycle system is being used to

tions but occurs during implementation repower Unit 1, one of two 11 0-MWe

or enforcement. units at the Tidd site.

 Environmental permitting processes Much of the original equipment is

can be long and costly, and delays tend being refurbished. The plants steam

to increase borrowing costs of a project. cycle is utilizing many of the existing

Time limits in some environmental and components, including the steam turbine

construction permits increase a devel- generator as well as condensate and

opers uncertainty and costs if repeated feedwater heaters and pumps.

applications are required. Many of the service buildings, control

 Uncertainty in the definition or systems, and piping systems also are

enforcement of regulations or in the being incorporated. The existing

future status of the regulations can have structures for storing and handling coal

a major impact on CCT projects. and dolomite are also being used, as well

9
Many existing facilities at Tidd are being as a 138,000-volt switchyard from which new building next to the wall of Tidd

refurbished and reused, such as the steam power will be sent into AEPs transmis- Unit 1 in one of the original ash ponds.

cycle, fuel storage and handling facilities, sion system. The new economizer, electrostatic

and switchyard. A new building adjacent to Major new equipment being installed precipitator, ash silos, and electrical vessel,

Tidd Unit 1 houses the PFBC pressure includes the PFB combustor and related control building are located nearby.

vessel, gas turbine, and other new systems. components (including the boiler, bed This layout allowed maximum use of

ash reinjection system and cyclones), the existing Tidd facilities.

gas turbine, coal and sorbent preparation

and injection systems, the economizer,

the electrostatic precipitator, ash removal and disposal systems, and electrical

components (including transformers and Tidd Power Island

switchgears). It also has been necessary

to construct new foundations, buildings, The Tidd PFBC Demonstration

and piping and electrical systems needed Project will be the nations first PFBC

to integrate the PFBC system with the plant to operate in a true combined-cycle

balance of the plant. mode, with both a gas turbine and a

The new PFBC power island, which steam turbine generating electricity.

includes the combustor, gas turbine, and Tidds new PFBC power island,

coal and sorbent systems, is located in a which is being incorporated into the

10
existing conventional steam cycle, will adjustment by dilution) controls the final

have a steam flow of 440,000 pounds per temperature of steam exiting the boiler.

hour at 1,300 psia and 925 0

F and a gross After passing through the in-bed

electrical output of 74 MWe (58 MWe secondary superheater, the steam exits

from the steam turbine and 16 MWe the boiler at 1,335 psia and 925 0

F.

from the gas turbine). During start-up and in the event of a

 The Tidd plant will demonstrate a steam turbine trip, a 50% bypass system

pressurized bubbling fluidized-bed oper- to the condenser and a pressure control

ating at about 175 psia. Pressurized valve to the atmosphere serve to dispose

combustion air is supplied by the gas of excess steam while controlling the

turbine. In the combustor, air fluidizes boiler pressure-temperature decay. In

and entrains bed materials consisting of the event of a loss of plant power or the

the fuel (a coal-water paste), coal ash, boiler feed pumps during operation, a

and dolomite sorbent. backup feedwater injection system main-

 After leaving the boiler, the hot gases tains water flow to the boiler circuits

and entrained ash particles pass into a contained in the slumped bed and thus

two-cyclone train. The cyclones remove exposed to heat.

98% of the entrained ash. The clean, hot

gases leave the pressure vessel via a

coaxial pipe and are expanded through a

high-pressure turbine and a low-pressure Plant Systems

turbine, then sent to the turbine exhaust Tidds new PFBC power island includes the

gas economizer. The gas is further One of the key objectives of the Tidd combustor vessel, gas turbine, and fuel

cleaned in an electrostatic precipitator demonstration project is successfully preparation system. Other related

and then emitted to the atmosphere. scaling up the PFBC system from pilot equipment, such as the economizer,

 The steam cycle is a Rankine cycle plant size to the 200-MWt Tidd plant. electrostatic precipitator, ash silos, and

with a once-through boiler. Condensate The 15-MWt integrated pilot plant, electrical controls, also were added.

(from a condenser) is heated in three

stages of low-pressure heaters and the

gas turbine intercooler as it is pumped to

the deaerator. The feedwater pressure is

then increased to 820 psia and further

heated. The flow is then further pressurized to 2,000 psia by the feedwater

pump and directed to the economizer,

where it is preheated to 480o

F by the

gas turbine exhaust before being routed to

the boiler.

The feedwater passes through the boiler

bottom zone and into the in-bed evaporator

surface. Here, steam is formed and

conveyed to the vertical separator. The

steam is two-phase up to about 40% load

and slightly superheated at full load. After

the steam enters the

in-bed primary superheater, spray

attemperation (which is temperature

11
designed for a relatively low differential

pressure even though the process pressure

is relatively high.

The pressure vessel is externally

insulated and is designed for internal

operating conditions of 590 0

F and

170 psia. It consists of a vertical cylindrical shell about 70 feet high and 44 feet

in diameter with elliptical heads.

The pressure vessel heads include

removable service openings that allow for

the removal of internal components. In

addition, internal and external service

platforms, lifting devices, and access

doors are provided to permit service and

maintenance of both the internal and

external systems.

PFBC Boiler

The PFBC boiler enclosure is designed

with membrane water wall construction.

At normal operating loads, the boiler is a

sub-critical, once-through unit. There are

three major sections in the boiler the

boiler bottom, the bed zone, and the

freeboard.

The boiler bottom consists of fluidizing

air ducts arranged on top of a pair of

membraned water wall hoppers. The

hoppers, which remain full of ash

This scale model of Tidds pressure vessel located at the PFBC Component Test during operation, direct the spent bed

shows (1) the dolomite feed system, Facility (CTF) in Sweden, was designed ash to the bed ash removal system.

(2) boiler tubes suspended in the fluidized to test components, process variables, The boilers bed zone is designed as a

bed, (3) coal feed lines, (4) vessel wall, and control systems at near-commercial deep (10.5 feet), tapered, fluidized bed

(5) two-stage cyclone train, and (6) bed ash size. The testing performed at the CTF in which the superheater and evaporator

reinjection vessel. has enabled AEP to verify the design sections are submerged. At full load, all

conditions projected for the Tidd PFBC of the evaporator and superheater

demonstration plant. surfaces are submerged within the bed.

At reduced loads, the bed level is lower,

Pressure Vessel thereby exposing portions of the surface.

The surface above the bed convectively

 A single cylindrical pressure vessel cools the gases feeding to the gas side,

contains the boiler, cyclones, cyclone because the convective heat transfer

ash coolers, and bed ash reinjection rates are lower than those within the bed.

system. This arrangement allows the In the freeboard section, excess air in

components within the vessel to be the hot gas is controlled to 25%. The

12
freeboard is sized to minimize the In scaling up bed area, experience has

elutriation (separation) of fly ash by the shown that boiler tube geometry and

gas flow and is internally insulated to cut proper air distribution are the most

heat loss on the way to the gas turbine, significant parameters relating to bed

 Critical design variables for the boiler temperature distribution. Increased bed

were bed temperature and area, operat- area is not expected to be a problem,

ing pressure, and residence time, especially since the larger bed area

 Bed temperature strongly influences minimizes the effects of wall cooling.

the process and is related to gas-side Earlier research has also indicated

corrosion. Experience at the CTF that between 150 and 300 psia, operating

indicated that gas-side corrosion should pressure does not significantly influence

not be a problem if bed temperature is process results. At 170 psia, Tidds bed

kept between 1,500 and 1,600 0

F. will operate well within this range.

Above this temperature range, there is Residence time, another critical

greater risk that high levels of alkali scale-up variable, strongly influences

constituents will form in the gas stream, sulfur removal and combustion

The Tidd plant is designed to operate at efficiency. Residence time is a function

a bed temperature of 1,580 0

F, which is of fluidizing velocity and bed depth.

within the acceptable range. Because these two parameters are

13

Component Testing for Commercial Scale-Up

 Technical risks associated with 235 psia. The GTE incorporates

scaling up technology to commer- key PFBC-related systems and

cial sizes are reduced by testing components needed for a cornthe proposed designs and mercial power station.

systems in an integrated facility. Key technological and

Testing of PFBC-related equip- developmental breakthroughs

ment and systems for Tidd was made at the GTE include:

conducted at the Component · Successful continuous

Test Facility (GTE) in Sweden. removal of cyclone ash in a

This facility is owned and dry state

operated by ASEA Brown Boveri · Successful utilization of hot

Carbon (ABB Carbon; formerly bed ash reinjection

known as Stal-Laval and then · Successful test of a rotating

ASEA Stal). ABB Carbon is one gas turbine cascade

of the partners in ASEA Babcock, · Successful gas cleaning

the PFBC supplier for Tidd. through a two-stage

 Operational since 1982, the cyclone train

GTE is an integrated PFBC pilot · Successful feeding of coal

plant. Its 1 5-MWt combustor can as a paste with less than

be operated at pressures of up to 25% total water content.
similar for both the CTF and Tidd, Air from the combustor pressure

scale-up problems are not expected. vessel transports the bed material to and

 Another area of technical concern in from the reinjection vessels. The

the development of PFBC technology transport air flow is separated from the

has been in-bed tube erosion. The ash and vented outside the combustor

design of the tube bundle for the Tidd into the main combustion flue gas. The

plant takes advantage of experience from reinjection vessels are normally at the

the CTF, and it is anticipated that tube same pressure as the boiler; however,

erosion rates will prove to be acceptable during load decreases, they are at a

for commercial applications, slightly lower pressure.

Bed Ash Reinjection System Ash Removal System

 Bed level is the main controlling Fine ash collected in the cyclones is

parameter in the PFBC boiler. The bed continuously removed by a pneumatic

ash reinjection system permits rapid transport system. The ash is cooled and

change in the unit load by transferring a portion of the heat is recovered in the

bed material to and from a pair of combustion air. Depressurization

reinjection vessels located inside the requires no lockhoppers or valves.

combustor pressure vessel. Special Granular bed ash is continuously

Cyclones clean particulates from hot flue handling devices are used to admit bed removed by gravity from the boiler

gases to prevent fouling and erosion of the material stored in the reinjection vessels bottom hoppers in order to maintain the

gas turbine. The Tidd pressure vessel into the bed, thus increasing load. To desired fluidized-bed level. Two

contains seven parallel strings of cyclones, decrease unit load, bed material is parallel lockhoppers, each serving one of

each with two stages. Pictured are both

stages of cyclones, prior to installation pneumatically transported from the bed the bottom hoppers, are filled and

inside the pressure vessel, to reinjection vessels, emptied independently. When full, the

lockhoppers are depressurized by

venting and are emptied by gravity into a

common atmospheric-pressure hopper.

From here the ash is fed onto an enclosed

conveyor system and transported to the

storage silo.

Cyclones

To reduce particulates flowing to the

gas turbine, the exhaust gas leaving the

upper part of the boiler freeboard passes

through a series of cyclones. At Tidd, there

are seven parallel strings of cyclones, each

with two stages of separation. The gas is

conveyed from the boiler to the first-stage

cyclones through connecting flues. Gas

flows from the second-stage cyclones to a

manifold and then exits the pressure vessel.

It then makes its way through

14
the inner portion of a coaxial pipe and past

the hot gas intercept valves on its way to

the gas turbine. The cyclones and gas

collecting pipe are insulated to minimize

gas temperature loss.

Gas Turbine Generator

The new gas turbine being used for the

demonstration project, the GT-35P, is a

modified ASEA Stal GT-35 that is

uniquely suitable for PFBC applications.

This turbine is arranged in-line on two

shafts. The variable speed, low-pressure

compressor is mechanically coupled to its

driving low-pressure turbine on one shaft.

The high-pressure turbine drives both the

constant speed high-pressure compressor

and the electric generator. An epicyclic

gear reducer couples the electric generator

to the high-pressure shaft.

With this design, combustion gas

temperatures fall when unit load is cut

because the lower bed height exposes

more steam generator tubes. As gas

temperature drops, the low-pressure

shaft slows, lessening the pressure and

flow of combustion air. Thus the freespinning low-pressure shaft allows the

air flow to vary with unit load.

The gas turbine in a PFBC combined

cycle system is subjected to very harsh

conditions and the Tidd demonstration

is no exception. Thus measures have

been taken to ensure the integrity and

operating life of the turbine. At Tidd,

the gas is precleaned using cyclones, and Assembly of the high-pressure turbine stage

Turbine erosion and corrosion as well is shown in the photo (top). Tidds gas

Turbine erosion and corrosion as well turbine is arranged in-line on two shafts: the

as deposition phenomena have been variable speed, low-pressure (LP) turbine on

researched extensively. An important one and the constant speed, high-pressure

aspect of the program at the CTF was (HP) turbine on the other.

investigation of the gas-cleanup and

gas-turbine interface. In testing at

turbine inlet temperatures to 1,526 0

F, no

blade erosion was found. Selection of

15
16

Hot Gas Cleanup R&D Planned

 The Tidd demonstration offers Even though there has been

a unique opportunity for devel- extensive development in

oping further advances in PFBC advanced HGCU filtration, AEP

components and systems. An concluded that advanced HGCU

agreement between AEP and technology was not yet ready to

DOE to test advanced hot gas be implemented into the design

cleanup (HGCU) filtration devices of Tidd, but that provisions should

is an example of the synergism be included at Tidd to test such a

possible between demonstration device in the future.

and R&D activities. The 5-year, $20-million HGCU

 Historically, gas turbines have research project will test filtration

been fueled from natural gas or devices in a slipstream. About

oil; however, Tidds gas turbine one-seventh of the combustor

will generate electricity from coal. exhaust gas 100,000 pounds

The key element at Tidd that per hour at full load will be

allows the gas turbine to be coal- diverted through this slipstream.

fired are cyclones-devices that Various types of filters will be

impart a swirl to gases laden with evaluated and one or two tested.

fly ash and remove over 98% of Four types of filters are under

the ash particles before the high- study: ceramic crossflow, moving

temperature, high-pressure gas screenless granular bed, ceramic

enters the turbine, candle, and ceramic tube filters.

 Although this gas is expected All use ceramic material

to be clean enough to prevent configured in various shapes and

damage to the gas turbine from sizes. Ceramic is used as the

particle erosion, the gas must be particulate barrier because it can

further cleaned to meet withstand harsh conditions.

particulate emissions standards. The filters trap virtually all

A conventional electrostatic particulate matter by acting as an

precipitator accomplishes this. impermeable barrier, in

 Ideally, an HGCU device could microscopic pores in the ceramic,

be located between the combus- or in a moving bed of granules as

tor and the gas turbine to remove the gas flows from the fluidized

sufficient particulate matter to bed to the gas turbine.

eliminate the need for the electro- Testing is scheduled to begin

static precipitator; however, this in early 1992 and will be

approach would require a very conducted during the second and

efficient filter capable of operating third years of Tidds operational

under comparatively severe phase. During this period, up to

conditions of over 1,500 0

F and 7,000 hours of test runs are

180 to 250 psia. planned for the HGCU devices.
the two-cyclone train for gas cleanup at Coal Feed System

Tidd was based on work at the CTF and

the cyclone manufacturers experience. A paste feed system is being used. It

Design modifications made in the gas was chosen because of its operating

turbine to improve reliability in PFBC ease, lower capital cost, better flow

applications include decreasing loading control, and better expected availability

on the first turbine stage by adding an than alternative methods. Also crushed

extra stage and increasing stability by rather than pulverized coal is being used

connecting the high-pressure shaft to the because small particles will elutriate

power turbine shaft by using a gear train. (separate) from the bed. This would be

undesirable as it would reduce the

Economizer residence time needed for efficient

combustion and sulfur absorption and

 A new, once-through, turbine exhaust would also cause excessive loading of

gas economizer will be used at Tidd. An dust within the cyclones.

economizer recovers heat from the gas To form the paste, uncrushed 1-inch

turbine exhaust for preheating the coal stored in a 45-ton capacity surge

feedwater. Tidd s economizer is a hopper is fed into a double-roll crusher. A coal-water paste fuels Tidds PFBC boiler.

modular design with the flue gas flowing A system of conveyors then transports Feed hoppers supply six parallel, hydraulihorizontally across vertical, in-line, the crushed coal (1/4-inch) onto a three- cally operated coal-injection pumps. Feed

spirally finned water tubes. It is in series deck screen to eliminate oversized lines leading from each pump carry the

with the condensate heaters and replaces pieces and into a pugmill-type mixer, paste upward and into the boiler.

existing high-pressure feedwater heaters.

Electrostatic Precipitator

After leaving the economizer, the gas

enters the electrostatic precipitator. Here,

the gas is further cleaned of particulates to

the NSPS level of 0.03 pounds per million

Btu. The gas is then released to the

atmosphere via the flue gas stack.

Steam Turbine Generator

The original Tidd plant steam turbine

generator is being refurbished and will

operate at half of its original rating to

generate 75% of the plants 70-MWe

capacity. Both the turbine rotor and

generator field for the steam cycle were on

reserve as system spares at another AEP

power plant. Refurbishing the turbine

involves replacing the first-stage wheel

and updating the former water seal system

with a more effective, new steam seal

system.

17
The fuel is pumped as a coal-water paste sorbent (1/8-inch) is controlled by a

which is 25% water. A specific distribu- vibrating screen and heated air flowing

tion of coal size is used to eliminate through the mill. The sized material is

inter-particle motion and to make swept from the mill by the hot air and

pumping the paste easier. The coals then sorted by a cyclone separator and a

moisture is measured on the weigh baghouse. A vibrating screen located at

feeder and water is added to the mixer to the outlet to the cyclone separator

prepare the paste. It then goes directly diverts oversized material back to the

into a fuel feed hopper which has a mill. The final product is transported by

1-hour storage capacity. conveyor into a 200-ton sorbent storage

 The feed hopper supplies six parallel, hopper. The hopper has two outlets to

hydraulically operated coal injection feed the sorbent injection system.

pumps that deliver the fuel to the boiler. Lockhoppers receive the prepared

Each pump feeds fuel into the boiler sorbent at atmospheric pressure. When

through a dedicated fuel nozzle, full, the lockhoppers are isolated from

the storage vessel and pressurized more

than the combustor. Variable-speed

Sorbent Feed System rotary feeders meter the flow of sorbent

The PFBC combined-cycle system is to pneumatic conveying pipes. When

integrated using eight process control units Sorbent (dolomite), stored in a 70-ton the lockhoppers are empty, they are

located in a central control room, shown capacity surge hopper, is first fed into an isolated from the combustor and are

under construction. impact dryer mill. The size of the vented to the atmosphere through a bag

filter. When completely depressurized,

they are then ready to be refilled.

Control System

A distributed programmable logic

system is being used to collect signals and

measurements. The control system, a

Bailey NET-90, uses eight process control

units divided into the following nodes: gas

turbine, combustor, steam turbine, balance

of plant, and safety.

These units perform the control of

individual plant items and also most of the

coordinating control, interlocking, and

automatic functions involving groups of

related items.

The control system will operate as an

integral-plus-proportional system. It

integrates the combined-cycle system

through a megawatt-demand signal. The

system determines the necessary fuel flow,

water flow, air flow, and bed level based

on predicted values and biased by feedback

loops.

18
19

Tidd PFBC Combined-Cycle Demonstration Project

Description: Electrical output: Combustor vessel:

 A PFBC combined-cycle system Net 70 MWe Operating temperature 590 0

F

is being used to repower a moth- Gross 74 MWe Operating pressure 170 psia

balled pulverized coal-fired power Steam turbine 58 MWe Diameter 44 ft

plant. Off gases from the combustor Gas turbine 16 MWe Height 70 ft

are expanded through a GT-35P gas Weight (total) 1,400 tons

turbine with a steam turbine Fuel and sorbent:

bottoming cycle. A new PFBC Pittsburgh #8 (3.4% sulfur) Combustion:

power island is being installed. Dolomite (Ca/S of 1.6) Temperature 1,580 0

F

Existing steam turbine and site Pressure 170 psia

utilities are being refurbished. Environmental performance:

S02 abatement 90% Steam flow:

Participants: NOx abatement 70% Temperature 925 0

F

Ohio Power Company Particulates 0.03 lb/106

 Btu Pressure 1,300 psia

American Electric Power Solid waste 32.8 lb/106

 Btu Flow rate (lb/hr) 440,000

 Service Corporation

Ohio Coal Development Office

U.S. Department of Energy Schedule for Project Phases 1987 1988 1989 1990 1991 1992 1993

Funding: I. Design & permitting

DOE $ 60,200,000 II. Procurement, construction & start-up

Industry $124,800,000 Ill. Operation, data collection, reporting

Total $185,000,000 & disposition
Project Progress

The Tidd cooperative agreement

between AEP, DOE, and the Ohio Coal

Development Office was executed in

1987. Formal ground breaking ceremonies were held in April 1988. The

project is on schedule, and plant start-up is

set for October 1990.

Proceeding on Schedule

Phase I (Design and Permitting) started

in February 1987. Phase II (Pro-curement,

Construction, and Start-up) began in

December 1987.

Construction is nearly complete. The

new combustor building has been

erected and contains the entire PFBC

pressure vessel. All of the major

components have been constructed and

installed, including the coal feed system,

pressure vessel, economizer, electrostatic precipitator, and ash silos. The

gas turbine is in place and ready to be

hooked up, and all new piping and

electrical work is almost completed.

Refurbishment of the steam turbine

began with disassembly in early 1988

and was completed in late 1989.

Moving the Pressure Vessel

The immense size of most utility

boilers requires that they be custom

assembled at the plant site. A PFBC boiler,

however, can be designed as a

modular unit. It is compact enough to be

fabricated at the manufacturers plant

and then transported to the plant site.

Tidds prefabricated pressure vessel is

Sparks fly as a worker grinds the edges of a service opening (top). A steel plate 3 inches as tall as a seven-story building. The thick

is bent to form a section of one of the three steel rings that were welded together to pressure vessel was shipped by barge make

the pressure vessel shell (bottom). Prefabricated at B&Ws facility in Mt. Vernon, nearly 750 miles up the Ohio River to

Indiana, the pressure vessel stands ready for removal of the top head and installation of the plant site.

internal components (opposite).

20

The combustor vessel was built over a 2-

year span at B&Ws fabrication facilities in

Mt. Vernon, Indiana. The 44-foot diameter,

70-foot tall combustor vessel is the largest

shop-built vessel in B&Ws history. By

building the vessel and shipping it intact,

considerable cost and time savings were

realized.

The vessel holds the fluidized-bed

enclosure with boiler tubes and other

associated equipment. These items were

also constructed as modules for easy

assembly into the vessel after being shipped

to the Tidd plant. The fluidizedbed boiler

modules were built at B&Ws facility at

West Point, Mississippi, and shipped via

the Mississippi and Ohio Rivers to Mt.

Vernon for placement inside the cylindrical

pressure vessel.

In May 1989, the completed pressure

vessel was loaded onto a 276-foot barge for

the river trip to the Tidd site. With the 17-

foot high hemispherical head removed, the

vessel stood 53 feet. The

vessel assembly and head weighed a total

of 1,392 tons. The entire cargo, consisting

of the vessel with internal items, head,

transport trailer, and other moving

apparatus, totaled 2,200 tons.

The barge passed through 13 locks and

under 49 bridges on its voyage through

Indiana, Kentucky, Ohio, and

West Virginia to Brilliant, Ohio.

High water from late spring rains

necessitated the addition of water ballast in

the barge to clear a railroad bridge at

Henderson, Kentucky. Even more ballast

was added shortly thereafter to improve

stability and provide adequate clearance

under another bridge.

Project engineers had calculated that a

suspension bridge at Wheeling, West

Virginia, would pose the tightest squeeze of

the trip. In the end, the combustor

The vessel, head, internal items, and transport equipment, weighing a total of 2,200 tons, had a 10-foot clearance as it passed

were loaded onto a 276-foot barge and shipped 750 miles up the Ohio River. After departing under this bridge. The combination of

Mt. Vernon (bottom), the loaded barge passed under 49 bridges, including those at the ballasted barge and greater water

Cincinnati (top).

22
depth made it possible to follow the rivers

sailing channel under the bridge.

Nine days after its departure from

Indiana, the combustor vessel arrived at

the landing area on the Tidd plant site.

Two crawler cranes helped hold the barge

in place against the landing area while

enough ballast was added to place the

barge level with the shore.

Once in position, with the tugboat

providing an extra push from behind, a

power unit was hitched to the trailer

carrying the 150-ton combustor vessel

head. The giant truck and cargo left the

barge and turned 900 to make the slow trip

up the 900-foot haul road to a spot in front

of the combustor building.

As soon as the combustor head left the

barge, workers began to prepare the 1,242-

ton combustor assembly for transport

using hydraulic push jacks, 10,000 psia

each, along a steel-plate track system.

Tons of fill material had been placed in the

haul road, 12 feet deep in some places, to

support the load. On the trip up the haul

road, workers alternated pushing the

vessel one day with moving and welding

the track system ahead of the cargo the

next day.

In late July 1989, the pressure vessel

head was hoisted by two crawler cranes

and placed into position. Then the entire

vessel was pushed into the combustor

building. Once the vessel arrived over its

pedestal, the contractor performed a final

rotation and centering move. The pressure

vessel was placed on its pedestal in early

August and was in its precise location four

days later.

The construction, shipping, and

installation of the combustor vessel are

 pioneering efforts. Almost every With the barge docked at Tidd, the crew gets ready to oft-load the head, detached for

facet from the new technology and its clearance under bridges (top). The vessel shell was moved up a 900-foot haul road, over a

modular construction to moving the steel plate track laid on timber mats (center). With major internal components installed and

vessel itself represents a challenge that the head repositioned, the pressure vessel is ready for the final move into the building

will benefit future PFBC plants. (bottom). Once in position, the head will be arc welded in place.

23
the performance and test data collected

during its operation are essential for

Tidd Test Program confirming technical feasibility and

economic viability. With this data, more

 During the 3-year operational phase, accurate forecasts of the cost of electricplant performance and operation will be ity from a PFBC combined-cycle plant

carefully monitored and analyzed to can be developed.

verify technical performance of the plant

and its components. Tests will establish Acceptance Testing

the reliability, load following capability,

and operating and maintenance costs. Acceptance testing will demonstrate

 Although the Tidd demonstration the technical feasibility of PFBC complant is not expected to be economical bined-cycle technology at the 70-MWe

or operate at a high level of availability, scale. Of primary interest are the

24

Parameters Continuously Monitored

 During Tidds operation, plant 6. Economizer mass flow,

performance will be monitored pressure, temperature, effeccontinuously. Detailed analysis of tiveness, and heat transfer

the data collected will yield infor- 7. Fly-ash mass flows, particle

mation about the deterioration of size distribution, and chemical

plant performance over time and analysis

will be used to ascertain preferred operating conditions and to 8. Bed-ash mass flows, particle

improve future designs. size distribution, and chemical

Major parameters being analysis

tracked are listed below: 9. Cyclone dust removal

1. Fluidization conditions efficiency and pressure loss

 (temperature, bed height) 10. Coal and sorbent mass flows,

2. Fluidized-bed air flow, gas particle size distributions, and

flow, temperature distribution, chemical analyses

 excess air factor, bed ash 11. Coal and sorbent feed

 removal rate, elutriation rate system consumption of water

3. Combustor mass flow, and transport gas

temperature, pressure, and 12. Coal heat input

heat transfer 13. Auxiliary power needs for all

4. Calcium-to-sulfur molar ratio PFBC-specific systems

5. Gas turbine efficiency and 14. Total combustor heat

output transfer efficiency.
combustor, gas turbine, and economizer, and controllability of a gas turbine

Test results will be used in a thorough operated in a combined-cycle mode with

assessment of the actual performance of PFBC. Therefore, special attention will

the equipment. These results will be be paid to the materials in the gas

compared to design expectations. The turbine to detect any deterioration that

information also will serve as a baseline might be caused by high-temperature

for performance tests. PFBC effluents.

 Another goal of the inspections is to

Performance Monitoring develop better RAM (reliability, availability, and maintainability) data for the

 Beginning with the initial start-up of combustor and related equipment. Data

the unit and continuing through the end analysis will provide PFBC equipment

of the project, plant performance will be manufacturers with information needed

monitored continuously. Engineers will to develop a reliable, cost-effective,

look for indications that equipment commercial plant design.

performance might be deteriorating with

time. A maintenance history for the System Response Testing

PFBC-related equipment will be

developed and the impact of plant Finally, system response testing will

operating conditions on this equipment be performed to verify the dynamic

determined. All plant effluents and behavior of combined-cycle PFBC

gaseous emissions will be monitored, systems. Various control strategies will

Manned test stations will sample fuel, be tested and evaluated to find out how

sorbent, ash, and particulate emissions PFBC plants can be best integrated with

for laboratory analysis. existing utility networks. Steady-state

 Detailed study of the test data will testing will be conducted over the load

yield preferred operating conditions for range of the unit, and transient studies

the PFBC combined-cycle concept and will be conducted during load changes

also provide the information necessary and trips. Process parameters also will

for improving the equipments design for be varied to optimize emission reducuse in future commercial facilities. tions and plant economics. Several coals

 Information will be available in real and sorbents also will be tested.

time and in an historical data base for Control principles being evaluated

assessing trends. Operators and test during system response testing include:

engineers will be able to make on-line · Unit load control by bed level,

calculations of system performance- which is controlled by bed ash

information needed to assure that test removal and reinjection

conditions are being met.

• Bed temperature control by fuel

Physical Equipment Inspections injection

• Excess air control by air flow

The third part of the testing program

involves periodic inspection of the major · Steam outlet temperature control

PFBC-specific equipment. Erosion, cor- by attempenition (temperature

rosion, and other wear characteristics adjustment) and feedwater flow

will be measured and evaluated. A · Steam outlet pressure control by

primary goal is to confirm the reliability turbine valve position.

25
Environmental

Monitoring

Throughout Tidds operational phase,

emissions and other aspects will be

monitored to ensure compliance with environmental regulations. Environmental

data being collected to comply with

applicable permits and regulations

should also provide the necessary data

for PFBC commercialization activities.

Nevertheless, supplemental monitoring

will provide additional data for use in

designing future PFBC systems.

Compliance monitoring activities at

Tidd will include stack gas monitoring

of SO, NO, and opacity. Other

required performance testing will

measure 502, NOx and particulates in

the duct leading from the combustor and

downstream of the precipitator.

 Supplemental testing for particulates

and determination of particle size will be

conducted on the emissions from the

combustor at a location downstream of

the gas turbine and upstream of the precipitator. The coal, sorbent feed, bed

ash, fly ash, and exhaust stream to the

stack will be checked for trace metals.

 The solids stream will be monitored

and analyzed daily. Measurements will

be taken of coal moisture, sulfur, ash,

and Btu content. Supplemental monitoring of the solids stream will develop data

for characterization of fly ash and bed

ash, evaluation of combustion process

performance, and additional analysis of

the coal and sorbent.

26

SO2 and NO~ Emissions Reductions

 Two critical air pollutants are To meet NSPS, the Tidd

emitted when coal is burned PFBC system is designed to use

sulfur dioxide (SO2) and nitrogen a calcium-to-sulfur molar ratio of

oxides (NOr). Emission levels of 1 .6. This level is expected to

these pollutants are regulated by capture 90% of the sulfur

the Environmental Protection released by high-sulfur (4%) coal.

Agencys New Source Perfor- NO~ emissions are a function

mance Standards (NSPS). A of the combustion temperature

primary goal of the Tidd project is and the amount of excess air

to demonstrate the ability of supplied to the combustion

PFBC technology to meet these process. NO~ emissions from a

standards, even when burning PFBC system are expected to be

high-sulfur coal. 50% to 70% lower than those

 Sulfur is removed by adding an from a conventional pulverized

alkali sorbent to the fluidized bed. coal-fired boiler. This decrease

Dolomite (calcium magnesium in NO~ occurs because of the

carbonate), a form of limestone, relatively low combustion

is the sorbent being used at Tidd. temperature in a fluidized bed.

 If enough sorbent is used while The Tidd plant is expected to

burning coal, it is possible to emit only 50% of the NO~ that

capture up to 95% of the sulfur would be emitted from a

released during combustion. conventional coal-fired plant.

Comparison of the Environmental Perfoemance

Selected Clean Coal Technologies

SO2 NOx

Heat Rate Removal Removal

Clean Coal Technologies (Btu/kWh) (%) (%)

Pulverized coal-fired with FGD 9,320 90+ 0

Circulating FBC 9,230 90 50

Gasification combined-cycle (GCC) 9,500 98

Advanced GCC 8,140 99+ 95+

PFBC 8,510 90+ 50+

Advanced PFBC 7,820 95+ 80+
27

The Road to Commercial Application

 The origin of FBC technology provided tens of thousands of

can be traced to the Winkler hours of test data.

gasifier developed in Germany U.S. interest in PFBC

during the 1920s. By the second technology intensified in the

world war, the technology was 1970s in response to stringent air

being used commercially in quality regulations and a need for

German coal gasification and an economical and environmetal refining industries, mentally acceptable way to burn

 The U.K. began developing high-sulfur domestic coal.

FBC in the 1950s, with the goal In 1980, testing began on a

of making use of locally available, wide range of design and

low-grade coals. At the same operating conditions at the

time, several countries were International Energy Agencys

developing a coal-fired gas Grimethorpe PFBC test facility,

turbine. However, early turbine- operated and jointly financed by

firing methods proved unaccept- the U.S., the U.K., and West

able, at least partly because of Germany. The facility has

problems associated with the provided pilot-scale data on

high combustion temperatures. technical and environmental

 Because of its relatively low performance, process monitoring

combustion temperatures, PFBC and control, the behavior of

came under study in the mid- regional coals and sorbents, and

1960s as a new means of firing a component performance and

gas turbine with coal. Plant-scale reliability. From 1986 to 1988,

PFBC testing began in 1968 at DOE participated in follow-on

the British Coal Utilization tests at Grimethorpe. An

Research Associations Coal updated, U.S. designed heat

Utilization Research Laboratory exchange bundle was used to

(CURL) in England. develop pilot-scale data on coal

 From the mid-i 970s to the feeding and combustion

early 1980s, several small-scale performance.

PFBC facilities were constructed. In 1980, ABB Carbon designed

These units, built by Exxon, the Component Test Facility

Curtiss-Wright, General Electric, (CTF). Operational since 1982,

New York University, Argonne this integrated PFBC pilot plant

National Laboratory, NASAs has been used to test and evalLewis Laboratory, the U.K.s uate components and systems

National Coal Board, and ABB designed for the Tidd demonCarbon (then Stal-Laval), have stration plant.
AEPs Philip Sporn Plant in West Virginia will

be the worlds largest PFBC power plant.

Two 1 50-MVJe pulverized coal-fired units

will be replaced with one 330-MVJe PFBC

combined-cycle system.

28

Sporn PFBC Demonstration Project

 AEPs Philip Sporn Plant in Capacity will be increased from

West Virginia will be the site for 300 to 330 MWe and net thermal

construction of the worlds largest efficiency from 36.5% to 38%.

PFBC power plant. The Sporn The existing boilers for Sporn

project is the next logical step in Units 3 and 4 will be replaced by

developing PFBC technology and a single P-800 PFBC module that

would be the worlds first large- will supply steam to both of the

scale repowering of a existing steam turbines.

conventional coal-fired plant. The combustor for the P-800

 The system used at Tidd is unit will be enclosed in a

pressure

being scaled up to 330 MWe, a vessel about 64 feet in diameter

size more typical of U.S. and 140 feet high. The operating

commercial utility applications, pressure will be about 235 psia,

With a goal of extending Sporns the combustion temperature

about

plant life by 25 years, reliability 1,580 0

F. The systems gas

and maintainability will be turbine, a modified GT-140P, has

important considerations in an output of about 72 MWe.

designing the repowered plant. After repowering, Sporn will be

 Currently Sporn consists of able to use 4%-sulfur coal

instead

five pulverized coal-fired units of the 1 %-sulfur coal currently

four identical units of 150 MWe burned to meet emissions requireeach and a 450-MWe unit. Two ments. The repowered unit is

of the smaller units will be replac- expected to burn 374,500 tons of

ed with a single PFBC module. high-sulfur coal per year.
Commercialization

Commercialization and marketing of

PFBC combined-cycle systems will be

performed by private industry. Equipment manufacturers, engineering firms,

and many other businesses are expected

to play key roles in the sale, design, construction, operation, and maintenance of

commercial PFBC systems.

Potential buyers, consisting of

utilities and other industries, will base

their decisions on whether or not to

nstall PFBC systems in a particular

facility on the merits of this technology

compared to other conventional and

emerging technologies.

The Tidd demonstration project is

expected to yield data and operating experience useful in improving the design,

operation, and economics of subsequent

commercial-scale PFBC plants. In

addition, successful demonstration of the

70-MWe PFBC unit at Tidd is expected

to comfirm the commercial feasibility of

this technology for power generation

units of under 100 MWe, a size typical

of many installations worldwide.

 However, according to ASBA

Babcock, the best applications for PFBC

technology are likely to be for repowering and adding new capacity increments

in medium (100-400 MWe) and large

(over 400 MWe) generating units. With repowering with PFBC at a size more

this in mind, AEP and ASEA Babcock typical of commercial utility applicaare currently negotiating another Clean tions in the U.S. and internationally.

Coal Technology Demonstration Project The potential PFBC market can be

with DOE that would address this divided into the repowering and new

market segment. capacity markets. There are an esti-

 A single 330-MWe combined-cycle mated 400 to 500 candidates for repowPFBC system would be used to repower ering with PFBC, with a cumulative

two existing I 50-MWe generating units capacity of over 70,000 MWe. Only 7%

at the Philip Sporn Plant in New Haven, of these units currently have SO2

West Virginia. With a capacity more removal systems. Candidate plants are

than four times that of Tidd, Sporn 20 to 40 years old, have a capacity of

would demonstrate the feasibility of between 40 and 360 MWe, an existing

29

Scaling Up PFBC Technology

CTF Tidd Sporn

Bed height (ft) 11 .5 10.5 12

Scale of bed area 1 16 24*

Bed pressure (atm) 12to16 12 16

Bed temperature (0

F) 1580 1580 1580

Fluidizing velocity (ft/sec) 3 3 3

Gas turbine inlet temperature (0

F) 1454 1526 1526

Scale of cyclones 1 1 .3 1 .3

Steam pressure (psia) 1440 1335 2015

Steam temperature (0

F) 990 925 1050/1 000

Thermal input (MWt) 15 200 800

* The commercial plant module has two beds, each at this scale
coal-fired boiler, and steam turbine

pressure of at least 1,300 psia.

PFBC is expected to be competitive

also with the atmospheric fluidized-bed

boiler in utility applications and could

eventually capture a significant share of

the market for replacing pulverized-coal

plants using flue gas desulfurization.

 It is expected that PFBC will be

commercially available by the year 2000

and that repowering with PFBC technology could increase capacity by up to

20,000 MWe by the year 2010.

 In the new capacity market, B&W

forecast that orders for all technologies

in the first half of the 1990s could total

60,000 MWe and then increase to

75,000 MWe by the second half of the

decade. During the 1990s, utilities are

projected to order or repower between

200 and 300 power plants and buy

between 250 and 300 cogeneration units.

 The ability of PFBC to service both

the new plant and life-extension markets

is expected to provide a basis for steady

penetration of the utility market. A

substantial market is also expected to

exist for the 80-MWe PFBC modules in

cogeneration applications.

 ASEA Babcock has determined that

two standard-size PFBC modules would

best meet the requirements for both new

and repowering markets. These two

modules are called:

· P-200, an 80-MWe module

· P-800, a 340-MWe module.

 These modules could be combined to

suit a wide range of plant sizes, such as

80 MWe, 160 MWe, 340 MWe, and

680 MWe. These sizes would enable

utilities to add small, moderate, or large

increments of power in relatively short

time intervals.

 The P-200 module is the type

installed at Tidd. Engineering studies to

support the development of the P-800

unit are in progress, and an assessment

30

Technical Partners in the Tidd Demonstration

American Electric Power which annually generates over

Company 100 billion kWh, ranks as the

 Two key participants in the nations second largest investorTidd project, OPCo and AEPSC owned producer of electric

are wholly owned subsidiaries o power. The system includes 10

the American Electric Power power plants with a capacity of

Company, Inc. (AEP), an electric 1,000 MWe or more; among

utility holding company. An these are six of the worlds

investor-owned electric utility largest operating units (each

company, OPCo generates, 1,300 MWe).

purchases, transmits, and

distributes electric power to over ASEA Babcock

625,000 customers in Ohio; Tidd AEPSC subcontracted with

is one of OPCos power plants. ASEA Babcock for construction

OPCo customers annually of the Tidd PFBC island. ASEA

consume over 33 billion kWh. Babcock is a business partner-

 As AEPs management, ship between ABB Carbon and

technology, and professional B&W formed to commercialize

services organization, AEPSC is PFBC technology,

designing, engineering, and B&W is a supplier of steam

managing construction of the generating equipment and has

Tidd demonstration plant. been designing, engineering, and

AEPSC also will provide technical constructing fluidized-bed

services to OPCo throughout the technology for over 30 years.

operating life of the Tidd plant. ABB Carbon develops and

 One of the largest U.S. users manufactures steam and gas

of coal, AEP burns more than turbines and other equipment for

40 million tons of coal per year to energy conversion. ABB Carbon

generate about 89% of its owns and operates the Compoelectricity. The AEP system, nent Test Facility.
of manufacturing facilities required for the

large pressure vessel is planned. The

design philosophy of the P-800 involves

multiples of hardware and equipment that

will be proven on the P-200.

In supporting the commercialization of

PFBC technology, especially for use in

future power generation applications, AEP

plans to share the operational information

gained from the Tidd demonstration with

other electric utilities and industries.

Except for contractual restrictions, AEP

does not intend to identify as proprietary

and confidential any information about

the project. Successful operation and

commercial demonstration of the PFBC

combined-cycle system at Tidd may

encourage U.S. manufacturers to provide

equipment that is applicable to PFBC

technology. Such equipment might involve

fuel preparation and feeding, ash removal,

and hot gas cleanup.

In addition to Tidd and Sporn, two

other PFBC projects are also under way

one at the Escatron plant in Spain and one

at the Vartan plant in Sweden.

ENDESA, the Spanish state-owned

utility, is repowering Unit 4 of the

Escatron power plant with a P-200 PFBC

module, the size of the unit used at Tidd.

ENDESA produces about 25% of Spains

electricity mainly by burning

coal and lignite. Spain has large center of Stockholm. Steam from the The vartan PFBC plant is located in the

reserves of black lignite which contain plant will be used for district heating. center of Stockholm (top). Low-sulfur coal

4% to 8% sulfur, 25% to 45% ash, The Vartan plant uses two P200 will fire two P-200 units, the same size used

and about 20% moisture. ENDESA PFBC modules and a single steam at Tidd, to cogenerate electricity and steam

chose PFBC over other technologies turbine. The plant will have a net output for district heating. Spains Escatron plant

because of its promise in burning this of 135 MWe of electricity and more than sulfur black lignite; a sorbent will capture at

type of coal. 225 MWt of heat while meeting ex- (bottom) will use PFBC to burn very highThe Escatron plant is designed to tremely stringent emissions require- least 90% of the sulfur. The Escatron

burn Spanish black lignite with 36% ash ments. Low-sulfur (1% or less) coal will pressure vessel is being constructed on site;

and 6.8% sulfur, and a moisture content be burned; and Swedish dolomite or the head and steel rings are ready for

of about 20%. Limestone will be used to limestone will be used as the sorbent. assembly.

capture at least 90% of the sulfur. Start-up tests began in late 1989.

 In Sweden, Stockholm Energi, a With commissioning proceeding ahead

municipal utility, has constructed a new of schedule, full commercial operation is

PFBC cogeneration power plant in the now expected by the end of 1990.

31
Clean Coal Technology The New Coal

Era (DOE/FE-0149), U.S. Department

References of Energy, Assistant Secretary for Fossil

Energy, November 1989.

Almquist, P., A. Dahl, and B. Nordmark,

 Status of the PFBC Project in Vartan, Disbrow, Richard E., The Clean Coal

Stockholm, Proceedings of the 1989 Program Taking Stock and Looking

International Conference on Fluidized Ahead, LANDMARC, Vol. 11, No. 4,

Bed Combustion. FBC Technology for July/August 1988, pp. 16-21. (Published

Today, Vol. 1, pp. 195-201. (Published bimonthly by the National Coal Associa

by the American Society of Mechanical tion, 1130 17th Street NW, Washington,

Engineers, United Engineering Center, DC 20036.)

345 East 47th Street, NY, NY 10017.)

Innovative Control Technology

ASEA Babcock PFBC Update. Advisory Panel, Report to the Secretary

(Published quarterly by ASEA Babcock; of Energy Concerning Commercialifor copies contact ASEA Babcock, One zation Incentives (DOE/EH-0083), U.S.

Park Centre, Wadsworth, OH 44281.) Department of Energy, Assistant

Secretary for Environment, Safety and

Clean Coal Technology Demonstration Health, January 1989.

Program Annual Report to Congress

(DOE/FE-0 125), U.S. Department of Mudd, M.J., Status of AEPs Tidd

Energy, Assistant Secretary for Fossil PFBC Demonstration Plant, ProceedEnergy, February 1989. ings of the 1989 International Conference on Fluidized Bed Combustion.•

Clean Coal Technology Demonstration FBC Technology for Today, Vol. 1,

Program Final Programmatic pp. 203-209. (The American Society of

Environmental Statement (DOE/EIS- Mechanical Engineers, United Engineer0146), U.S. Department of Energy, ing Center, 345 East 47th Street, NY,

November 1989. NY 10017.)

Clean Coal Technology PFBC Update. Prefab Utility-Scale Fluidized-Bed

(Published quarterly by American Combustor Barged up Ohio River,

Electric Power; for copies contact Fossil Energy Review, May-June 1989,

Gregory D. Soulsby, Ohio Power Co. pp. 8-9. (Published periodically by

Public Affairs, P.O. Box 24400, Canton, DOEs Office of Fossil Energy; for

OH 44701-4400.) copies contact the Fossil Energy ComPreparation and printing of this document was munications Staff, FE-5, U.S. Departfunded jointly by American Electric Power Comprehensive Report to Congress, ment of Energy, Washington,

Service Corporation and the U.S. Department Clean Coal Technology: Tidd PFBC DC 20585.)

of Energy. The funding contribution of the Demonstration Project (DOE/FE-0078;

industrial participant permitted inclusion CCT/87 MC 24132), U.S. Department of The Role of Repowering in Americas

of multicolor artwork and photographs. Energy, Office of Fossil Energy, Power Generation Future (DOE/FE

Report preparation by Energetics, Inc.; 

research and editing by Jill J. Rasmussen February 1987. 0096), U.S. Department of Energy,

and Nancy G. Margolis. Office of Fossil Energy, December 1987.

32

To Receive Future Reports

 To be placed on the CCT

distribution list for future

topical reports and other

publications about the CCT

program and demonstration

projects, contact:

Ms. Denise Calore

FE-22

U.S. Department of Energy

Washington, DC 20585

(202) 586-7148