Energy Analysis of the Ideal Rankine CycleThe pump, boiler, turbine, and condenser are steady-flow devices, and thus all four processes that make up the Rankine cycle can be analyzed as
Trang 1Anh văn Chuyên ngành Nhiệt
English for thermal engineering
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Trang 3Tài liệu tham khảo
1 Fundamentals of thermal-fluid science, Y A Çengel.
2 Fundamentals of thermodynamics (sixth edition),
Sonntag, Borgnakke and van Wylen.
3 Steam plant operation (Eighth edition), Everett B
Woodruff, Herbert B Lammers, Thomas B Lammers
3
Trang 45.1 Rankine cycle: The ideal cycle
1-2 Isentropic compression in a pump
The ideal Rankine cycle does not involve any internal irreversibilities and consists
of the following four processes:
Trang 5Energy Analysis of the Ideal Rankine Cycle
The pump, boiler, turbine, and condenser are steady-flow devices, and thus all four processes that make up the Rankine cycle can be analyzed as steady-flow processes
The steady-flow energy equation per unit mass of steam reduces to:
Trang 6The Simple Ideal Rankine Cycle
Consider a steam power plant operating on the simple ideal Rankine cycle The steam enters the turbine at 3 MPa and 350˚C and is condensed in the condenser
at a pressure of 75 kPa Determine the thermal efficiency of this cycle
5.1 Rankine cycle: The ideal cycle
Trang 75.1 Rankine cycle: The ideal cycle
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Trang 85.1 Rankine cycle: The ideal cycle
Trang 9Actual vapor power cycles
Fluid friction causes pressure drops in the boiler, the condenser, and the
piping between various components;
The heat loss from the steam to the surroundings as the steam flows through
various components
(a) Deviation of actual vapor power cycle from the ideal Rankine cycle; (b) The effect
of pump and turbine irreversibilities on the ideal Rankine cycle.
5.1 Rankine cycle: The ideal cycle
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Trang 10Actual vapor power cycles
The irreversibilities occurring within the pump
and the turbine
A greater work input in pump, and a smaller work output in turbine
Isentropic efficiencies
5.1 Rankine cycle: The ideal cycle
Trang 11Methods to increase the efficiency of the Rankine cycle
Air leakage into the condenser
Turbine blades erosion,Turbine efficiency decreasing
5.1 Rankine cycle: The ideal cycle
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Trang 12Methods to increase the efficiency of the Rankine cycle
5.1 Rankine cycle: The ideal cycle
Trang 13Methods to increase the efficiency of the Rankine cycle
Operating pressures of boilers have gradually increased over the years from about 2.7 MPa (400 psia) in 1922 to over 30 MPa (4500 psia) today, generating enough steam to produce a net power output of 1000 MW or more in a large power plant Today many modern steam power plants operate at supercritical pressures (P> 22.09 MPa) and have thermal efficiencies of about 40 % for fossil-fuel plants and 34 % for nuclear plants.
5.1 Rankine cycle: The ideal cycle
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Trang 14Methods to increase the efficiency of the Rankine cycle
The ideal Reheat Rankine Cycle
5.1 Rankine cycle: The ideal cycle
Trang 155.2 The Boiler
A boiler (or steam generator, as it is commonly called)
is a closed vessel in which water, under pressure, is transformed into steam by the application of heat.
Definition
A steam electric power plant is a means for converting
the potential chemical energy of fuel into electrical
Trang 165.2 The Boiler
The ideal boiler includes:
1 Simplicity in construction, excellent workmanship, materials conducive
to low maintenance cost, high efficiency, and high availability;
2 Design and construction to accommodate expansion and contractionproperties of materials;
3 Adequate steam and water space, delivery of clean steam, and goodwater circulation;
4 A furnace setting conducive to efficient combustion and maximum rate
of heat transfer;
Trang 175.2 The Boiler
Boiler water circulation methods (a) Simple natural or thermal circulation loop (b) Simple forced or
pumped circulation loop (Babcock & Wilcox, a McDermott company.) 17
Trang 185.2 The Boiler
Fire-Tube Boilers
Trang 195.2 The Boiler
Fire-Tube Boilers
Capacity: 6 to 75 bhp (4.47 kW – 55.875 kW)
Tube diameter size: from 2’ to 3’ (50.8 - 76.2 mm)
Pressures to 100 psi = 689.476 kPa ( 6.9 bar)
Boiler diameters: from 3 to 5 ft; and height from 5
to 10 ft
The exposed-tube arrangement, 10 to 15°F of
superheat may be obtained.
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Trang 205.2 The Boiler
Horizontal fire-tube boilers
Trang 21Fuels: Solid fuels (coal, wood), oil and natural gas
Operation mode: Manual and automatic
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Trang 225.2 The Boiler
Water-Tube Boilers
A water-tube boiler is one in which the products of combustion (called flue gas) pass around tubes containing water The tubes are interconnected to common water channels and to
the steam outlet
Trang 235.2 The Boiler
Water-Tube Boilers
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Trang 24Diesel Engine
Thermal Energy
Rotational Mech Energy
Electrical Energy
Steam
Rotational Motion
Combustion Gas
Trang 255.3 Thermal Power Plant
General Layout of Steam Power Plant
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Trang 26Thermal Power Plant
What is boiler ?
A Boiler is a closed vessel
in which water or other fluid
is heated under pressure.
The steam is then
circulated out of boiler for
use in various process or
heating applications
Steam Steam
Flue Gas Air
Fuel Water
Turbine
Trang 275.3 Thermal Power Plant - Boiler
Fuel • Coal fired Boiler
• Oil fired Boiler
• Gas fired Boiler
• Multi-fuel fired Boiler
• Fluidized Bed Firing
• Suspension Firing : Tangential, Wall Burner, etc
Circulation
Steam Pressure
• Natural Circulation Boiler
• Controlled Circulation Boiler
• Once-Through Boiler
• Sub-critical Pressure Boiler
• Super-critical Pressure Boiler
• Ultra Super-critical Pressure Boiler (USC)
Classification : Boiler Types
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Trang 285.3 Thermal Power Plant - Boiler Components & Equipment
Pressure Parts Non-Pressure Parts
Fuel System
Burner
Circulation System
Environment
Protection Sys.
Trang 29Draft Sys Firing Sys.
C & I Environ Sys.
Heat Exchanger
Circulation System
Trang 30Circulation System
Trang 3131
Trang 32Draft Sys.
Firing Sys.
C & I Environ Sys.
Heat Exchanger
Circulation System
• Pulverizer
• Burner
Boiler Components & Equipment
Trang 33- Pulverizer or Mill
Raw Coal Pulverized Coal
Roller Primary Air
Trang 352 nd Air
Primary Air (Fuel Air)
1 st Air (Hot)
1 st Air (Cold)
Air Preheater
Gas Duct
Air Duct
Air Duct
Stack
ID Fans
Draft Sys.
Firing Sys.
C & I Environ Sys.
Heat Exchanger
Circulation System
Draft System
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Trang 361) Fans Draft Sys.
• Fans
• Ductworks
• Air Heater
• Forced Draft Fan, FDF
- supplys air necessary for fuel combustion
• Primary Air Fan, PAF
- supplys air needed to dry and transport coal
from mills to the furnace
• Induced Draft Fan, IDF
- exhausts flue gas from the furnace
with suction force
Draft System
Trang 372) Ductworks Draft Sys.
Trang 383) Air Heater Draft Sys.
Trang 39Ⅰ Overview – Boiler Components &
Equipment
Draft Sys Firing Sys.
C & I
Environ Sys.
Heat Exchanger
Circulation System
• SCR
• EP
• FGD
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Trang 401) Selective Catalystic NOx Reduction System (SCR)
Environmental Protection System
Draft Sys Firing Sys.
C & I
Environ Sys.
Heat Exchanger
Circulation System
• SCR
• EP
• FGD
Trang 412) Electrostatic Precipitator (EP)
Draft Sys Firing Sys.
C & I
Environ Sys.
Heat Exchanger
Circulation System
Trang 423) Flue Gas Desulphurization System (FGD)
Gas Inlet
Gas Outlet
Limestone Slurry
Draft Sys Firing Sys.
C & I
Environ Sys.
Heat Exchanger
Circulation System
Trang 43C & I Environ Sys.
Heat Exchanger
Circulation System
• Condenser
• Deaerator
• Feedwater Heater
Heat Exchangers
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Trang 44http://blogcongdong.com