Chapter 4 Fossil Fuel Energies
Boosting Power Plant Efficient (提昇發電效率)
 Low Emission Boiler Systems—LEBS (低排
放鍋爐系統)
 Pressurized Fluidized Bed Combustion—
PFBC (高壓流體化床燃燒技術)
 Integrated Gasification Combined Cycle—
IGCC (氣化複循環發電技術)
 Indirectly Fired Cycle—IFC (間接燃燒循環發
電技術)
 Advanced Turbine Systems—ATS (先進渦輪
機系統)

4-1 Boosting Power Plant Efficient

Less fuel will be consumed to generate the same
amount of electricity.
↓
sharply reduce emissions of CO2
4-1 Boosting Power Plant Efficient

Coal-Fired Power Plants
1. Efficiency ~ 33-38 %
2. Retrieve waste heat
3. Simple cycle:heat from the burning coal boils water
to create steam which spins a steam turbinegenerator
↓
combined two or more power generation cycles
4-1 Boosting Power Plant Efficient
4-1 Boosting Power Plant Efficient

Low Emission Boiler System—
“supercritical steam cycle”
a conventional power plant boiler releases steam
at p~2400 psi (160 bar) & T~1050 oF (570 oC)
↓
p~3400-5500 psi (230-370 bar) & T~1100 oF
(590 oC)
4-1 Boosting Power Plant Efficient

Conventional combined cycle—
burn natural gas or petroleum products, using
the hot combustion gases to power a combustion
gas turbine-generator, then channelling the waste
heat to drive a steam turbine-generator.
↓
Pressurized Fluidized Bed Combustion &
Integrated Gasification Combined Cycle (DOE
for “combined cycle” operation to coal-burning
power plants)
4-1 Boosting Power Plant Efficient

Pressurized Fluidized Bed Combustion
system—
coal is burned at elevated pressures (6-16 bars)
to produce a high-p exhaust gas stream. →spin a
gas turbine-generator. Simultaneously, the boiler
also heats water to produce steam (steam cycle)
4-1 Boosting Power Plant Efficient

Integrated Gasification Combined Cycle
system—
coal is converted into a combustible gas
(typically a mixture of CO and H2)
↓
The gas is burned in the combustor for a gas
turbine-generator. Simultaneously, exhaust gases
from the gas turbine heats water to produce
steam (steam cycle)
4-1 Boosting Power Plant Efficient

Integrated Gasification Combined Cycle
system—
In the future, may combine with high-T fuel cell
↓
A hybrid system combining coal gasification,
high-T fuel cells, and high efficiency gas turbine
cycles→ efficiency up to 60% & CO2 release cut
to half of conventional one.
4-1 Boosting Power Plant Efficient

Integrated Gasification Combined Cycle
system—
Gasification-based power system produce a
concentrated CO2 gas stream→ carbon
sequestration
↓
cf. conventional coal-burning tech. release CO2
in a diluted, high-volume mixture with nitrogen
(from the combustion
4-1 Boosting Power Plant Efficient

Natural Gas Power Plants
–
Worldwide, 16% of fuel consumed for electricity
generation in 1995→23% in 2015
–
Emits only ½ CO2 than coal for the same energy
produced.
4-1 Boosting Power Plant Efficient

Natural Gas Power Plants
4-1 Boosting Power Plant Efficient



Natural Gas Turbines
40 years ago, η~20% for a simple cycle system.
Today, η~30% for a simple cycle system & η~mid-50%
for a combined cycle system .
Thermal efficiency of a gas turbine depends on T of the
gas entering the turbine blades.~2300 oF (1260 oC) for
modern turbines (temperature barrier)
↓
Reaching the limits of current materials → new
materials or better ways to cool the blades
DOE is developing new tech. to push Tinlet to 2600 oF
(1430 oC) → η~60% for a combined cycle system
4-1 Boosting Power Plant Efficient

Fuel Cell Power Plants—another way to use
natural gas, η> 50%
–
–
Using an electrochemical reaction of H2 (fuel) and
O2 (from air) to produce electricity, water and heat.
Generate the least amount of CO2 in the fuel
processing stage.
4-1 Boosting Power Plant Efficient
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「一度電」的定義就是1kWh也就是一千瓦小
時
「一度電」就是1000(W)瓦耗電的用電器具，
使用一小時所消耗的 電量
例如你點亮一個100瓦的燈泡10小時，也就是
1000Whr，也就耗掉「一度電」了
一度電 = 一千瓦 x3600秒= 3,600,000焦耳
4-1 Boosting Power Plant Efficient



BTU (British thermal unit):a unit of energy used in the
United States. In most other areas, it has been replaced
by the SI unit of energy, the joule (J).
In the United States, the term "BTU" is used to describe
the heat value (energy content) of fuels, and also to
describe the power of heating and cooling systems,
such as furnaces, stoves, barbecue grills and air
conditioners.
When used as a unit of power, BTU per hour is
understood, though this is often confusingly
abbreviated to just "BTU".
4-1 Boosting Power Plant Efficient

1 BTU ≡ the amount of heat required to raise T
of one pound of water by one degree Fahrenheit.

One BTU is approximately:
1.054-1.060 kilojoule
252–253 cal (calories, small)
0.252–0.253 kcal (kilocalories)
778–782 ft·lbf (foot-pounds-force)
4-1 Boosting Power Plant Efficient
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1 watt is approximately 3.41 BTU/h
1000 BTU/h is approximately 293 W
1 horsepower is approximately 2540 BTU/h
1 "ton of cooling", a common unit in North American
refrigeration and air conditioning applications, is 12,000 BTU/h
(~3.5kW). It is the amount of power needed to melt one short ton
of ice in 24 hours.
1 therm is defined in the United States and European Union as
100,000 BTU – but the U.S. uses the BTU59 °F whilst the EU
uses the BTUIT.
1 quad (short for quadrillion BTU) is defined as 1015 BTU,
which is about one exajoule (1.055×1018 J). Quads are
occasionally used in the United States for representing the annual
energy consumption of large economies: for example, the U.S.
economy used about 94.2 quads/year in 1997.
4-2 Low Emission Boiler System

B&W’s Advanced Coal-Fired Low Emission
Boiler System
4-2 Low Emission Boiler System

1. Rankine cycle.
Simple Steam Rankine Cycle
4-2 Low Emission Boiler System

1. Rankine cycle—coal, oil, and natural gas.
Simple Steam Rankine Cycle
4-2 Low Emission Boiler System

1. Rankine cycle—coal, oil, and natural gas.
Simple Steam Rankine Cycle
4-2 Low Emission Boiler System

1. Rankine cycle—coal, oil, and natural gas.
Simple Steam Rankine Cycle
4-2 Low Emission Boiler System

2. Bryton Cycle—oil or natural gas.
Basic Bryton Cycle
4-2 Low Emission Boiler System

2. Bryton Cycle—oil or natural gas.
Basic Bryton Cycle
4-2 Low Emission Boiler System

3. Combined Cycle
4-3 Pressurized Fluidized Bed Combustion


Fluidized bed combustion (FBC) is a
combustion technology used in power plants.
FBC plants are more flexible than conventional
plants in that they can be fired on coal, biomass,
among other fuels. These boilers operate at
atmospheric pressure
Fluidized beds suspend solid fuels on upwardblowing jets of air during the combustion
process. The result is a turbulent mixing of gas
and solids. The tumbling action, much like a
bubbling fluid, provides more effective chemical
reactions and heat transfer.
4-3 Pressurized Fluidized Bed Combustion
4-3 Pressurized Fluidized Bed Combustion
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
FBC reduces the amount of sulfur emitted in the form
of SOx emissions.
Limestone is used to precipitate out sulfate during
combustion, which also allows more efficient heat
transfer from the boiler to the apparatus used to capture
the heat energy (usually water pipes). The heated
precipitate coming in direct contact with the pipes
(heating by conduction) increases the efficiency. Since
this allows coal plants to burn at cooler temperatures,
less NOx is also emitted.
However, burning at low temperatures also causes
increased carbon dioxide, nitrous oxide, and polycyclic
aromatic hydrocarbon emissions. FBC boilers can burn
fuels other than coal, and the lower temperatures of
combustion (800 °C) have other added benefits as well.
4-3 Pressurized Fluidized Bed Combustion
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FBC evolved from efforts to find a combustion process
able to control pollutant emissions without external
emission controls (such as scrubbers).
The technology burns fuel at temperatures of 1,400 to
1,700 °F (760 to 930 °C), well below the threshold
where nitrogen oxides form (at approximately 2,500 °F
(1370 °C)).
The mixing action of the fluidized bed results brings the
flue gases into contact with a sulfur-absorbing chemical,
such as limestone or dolomite. (> 95% of the sulfur
pollutants in coal can be captured inside the boiler by
the sorbent)
Commercial FBC units operate at competitive
efficiencies, cost less than today's units, and have NOx
and SO2 emissions below levels mandated by Federal
standards.
4-3 Pressurized Fluidized Bed Combustion
(r2001_03_109.pdf,)

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The first-generation PFBC system also uses a sorbent
and jets of air to suspend the mixture of sorbent and
burning coal during combustion. However, these
systems operate at elevated pressures and produce a
high-pressure gas stream at temperatures that can drive
a gas turbine. Steam generated from the heat in the
fluidized bed is sent to a steam turbine, creating a
highly efficient combined cycle system.
A 1-1/2 generation PFBC system increases the gas
turbine firing temperature by using natural gas in
addition to the vitiated air from the PFB combustor.
This mixture is burned in a topping combustor to
provide higher inlet temperatures for greater combined
cycle efficiency. However, this uses natural gas, usually
a higher priced fuel than coal.
4-3 Pressurized Fluidized Bed Combustion
4-3 Pressurized Fluidized Bed Combustion
(2_1a6.pdf)
4-3 Pressurized Fluidized Bed Combustion
(2_1a6.pdf)
4-4 Integrated Gasification Combined
Cycle Technology
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This power plant configuration relies on a coal gasifier
rather than a boiler.
Combustible gases produced by the gasifier can be
cleaned to high purity levels (more than 99 percent
sulfur removal) before being burned in a gas turbine.
Exhaust heat can be used to drive a steam turbine.
1st-generation systems now being readied for
construction can achieve efficiencies up to 42%. 2ndgeneration systems could reach efficiencies of 45 % by
the end of this decade, and more advanced systems
envisioned are expected to exceed 50 % efficiency
levels.
Sulfur dioxide and nitrogen oxides emissions are less
than one-tenth of the New Source Performance
Standards.
4-4 Integrated Gasification Combined
Cycle Technology
4-4 Integrated Gasification Combined
Cycle Technology
4-4 Integrated Gasification Combined
Cycle Technology
4-4 Integrated Gasification Combined
Cycle Technology

IGCC Advantage
1. A Clean Environment—99% SO2 removed before
combustion, NOx reduced by over 90%, CO2 is cut
by 35%.
2. High Efficiency—42 – 52%
3. Low-Cost Electricity.
4. Low-Capital Costs
5. Repowering of Existing Plants—components of
IGCC can be integrated into an existing system in
modular form
6. Modularity—allowed for staged additions in blocks
ranging in size from 100-450 MW.
4-4 Integrated Gasification Combined
Cycle Technology

IGCC Advantage
7. Fuel Flexibility—most gasifier systems can be easily
adapted to different
8. Phased Construction—1st-phase include only a gas
turbine, operating as a simple natural-gas-fired
cycle.(2/3 ultimate capacity) →2nd phase, a steam
turbine create a combined cycle with full capacity.
→3rd phase, integrate the gasifier and gas cleanup
systems.
9. Low Water Use. ~50-70 % that of a PC plant with a
flue gas desulfurization system
10. Low CO2 Emissions. ∵ high efficiency. More
reduction when combined with fuel cell systems in
the future.
11. Continuous Product Improvement
4-4 Integrated Gasification Combined
Cycle Technology

IGCC Advantage
12. Reusable Sorbents
13. Marketable By-Products—Waste disposal is minimal:
sulfuric acid, element sulfur, Ash and any trace
elements are melted and when cooled become an
environmentally safe, glass-like slag that can be used
in the construction or cement industries.
14. Co-Products—fuels in the form of methanol or
gasoline, urea (尿素) for fertilizer, hot metal for
steal making and chemicals.
15. Demonstrated Success
16. Public Acceptability
4-4 Integrated Gasification Combined
Cycle Technology

Improving Key Components
1.
2.
3.
4.
Advanced Gasifier Systems
Hot Gas Desulfurization
Hot Gas Particulate Removal
Advanced Turbine Systems (ATS)
4-5 Indirectly Fired Cycle Systems


The combustion gases created by burning coal in
this high performance power system are
prevented from contacting a gas turbine. Instead,
they transfer heat to an impurity free gas, eg. air,
that powers the turbine.
Currently, in the conceptual design phase,
indirectly fired cycle systems could offer a coalbased technology with efficiencies approaching
50 %, with sulfur dioxide, nitrogen oxides, and
particulates reduced to 1/4 of the New Source
Performance Standards.
4-5 Indirectly Fired Cycle Systems
4-5 Indirectly Fired Cycle Systems
4-5 Indirectly Fired Cycle Systems

Ceramic Heat Exchanger Development (Key
component)
1.
2.
3.
4.
5.
Survive high operating temperature
Resist corrosion
Withstand pressure differentials
Avoid seal leakage
Avoid catastrophic failure
4-6 Advanced Turbine Systems
What is a Gas Turbine? (also called a combustion
turbine)

–
–
–
A rotary engine that extracts energy from a flow of
combustion gas. It has an upstream compressor coupled to a
downstream turbine, and a combustion chamber in-between.
Energy is released when air is mixed with fuel and ignited in
the combustor. The resulting gasses are directed over the
turbine's blades, spinning the turbine and powering the
compressor, and finally is passed through a nozzle, generating
additional thrust by accelerating the hot exhaust gases by
expansion back to atmospheric pressure.
Energy is extracted in the form of shaft power, compressed air
and thrust, in any combination, and used to power aircraft,
trains, ships, generators, and even tanks
4-6 Advanced Turbine Systems

What is a Gas Turbine?
This machine has a single-stage radial compressor and turbine, a recuperator,
and foil bearings.
4-6 Advanced Turbine Systems

What is a Gas Turbine?
–
–
The power turbines in the largest industrial gas
turbines operate at 3,000 or 3,600 rpm to match the
AC power grid frequency and to avoid the need for a
reduction gearbox. Such engines require a dedicated
building.
They can be particularly efficient — up to 60% —
when waste heat from the gas turbine is recovered by
a conventional steam turbine in a combined cycle
configuration.
4-6 Advanced Turbine Systems

What is a Gas Turbine?
–
–
–
They can also be run in a cogeneration configuration: the
exhaust is used for space or water heating, or drives an
absorption chiller for cooling or refrigeration;
cogeneration can be over 90% efficient.
Simple cycle gas turbines in the power industry require
smaller capital investment than combined cycle gas, coal
or nuclear plants and can be designed to generate small
or large amounts of power.
Also, the actual construction process can take as little as
several weeks to a few months, compared to years for
baseload plants. Their other main advantage is the ability
to be turned on and off within minutes, supplying power
during peak demand. Large simple cycle gas turbines
may produce several hundred megawatts of power and
approach 40% thermal efficiency.
4-6 Advanced Turbine Systems
GE H series power generation gas turbine. This 480-megawatt unit has
a rated thermal efficiency of 60% in combined cycle configurations.
4-6 Advanced Turbine Systems
4-6 Advanced Turbine Systems
4-6 Advanced Turbine Systems
4-6 Advanced Turbine Systems
4-6 Advanced Turbine Systems
4-6 Advanced Turbine Systems
4-6 Advanced Turbine Systems (ngt.pdf)
4-6 Advanced Turbine Systems
4-6 Advanced Turbine Systems
4-6 Advanced Turbine Systems
4-6 Advanced Turbine Systems
4-6 Advanced Turbine Systems
4-6 Advanced Turbine Systems
4-6 Advanced Turbine Systems
4-6 Advanced Turbine Systems
4-6 Advanced Turbine Systems
4-6 Advanced Turbine Systems
4-6 Advanced Turbine Systems