Post on 24-Dec-2015
description
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Training Session on Energy Training Session on Energy EquipmentEquipment
CogenerationCogeneration
Ther m
al Equipm
ent/C
ogener ation
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Training Agenda: CogenerationTraining Agenda: Cogeneration
Ther m
al Equipm
ent/C
ogener ation
Introduction
Types of cogeneration systems
Assessment of cogeneration systems
Energy efficiency opportunities
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IntroductionIntroduction
• Generation of multiple forms of energy in one system: heat and power
• Defined by its “prime movers”• Reciprocating engines• Combustion or gas turbines, • Steam turbines• Microturbines• Fuel cells
What’s a Cogeneration/CHP System?Ther m
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IntroductionIntroduction
Efficiency Advantage of CHPTher m
al Equipm
ent/C
ogener ation 100 68
24 Units
34 Units
6 Units (Losses)
60
40
36 Units (Losses)
= 85%
= 40%
10 Units (Losses)
Conventional Generation (58% Overall Efficiency)
Combined Heat & Power (85% Overall Efficiency)
(UNESCAP, 2004)
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IntroductionIntroduction
• Increased efficiency of energy conversion and use
• Lower emissions, especially CO2
• Ability to use waste materials
• Large cost savings
• Opportunity to decentralize the electricity generation
• Promoting liberalization in energy markets
Benefits of Cogeneration / CHP)Ther m
al Equipm
ent/C
ogener ation
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Training Agenda: CogenerationTraining Agenda: Cogeneration
Ther m
al Equipm
ent/C
ogener ation
Introduction
Types of cogeneration systems
Assessment of cogeneration systems
Energy efficiency opportunities
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Type of Cogeneration SystemsType of Cogeneration Systems
• Steam turbine
• Gas turbine
• Reciprocating engine
• Other classifications:
- Topping cycle
- Bottoming cycle
Ther m
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ogener ation
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Type of Cogeneration SystemsType of Cogeneration Systems
• Widely used in CHP applications
• Oldest prime mover technology
• Capacities: 50 kW to hundreds of MWs
• Thermodynamic cycle is the “Rankin cycle” that uses a boiler
• Most common types• Back pressure steam turbine• Extraction condensing steam turbine
Steam Turbine Cogeneration SystemTher m
al Equipm
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• Steam exits the turbine at a higher pressure that the atmospheric
Back Pressure Steam TurbineTher m
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Fuel
Figure: Back pressure steam turbine
Advantages:-Simple configuration-Low capital cost-Low need of cooling water -High total efficiency
Disadvantages:-Larger steam turbine-Electrical load and output can not be matched
Boiler Turbine
Process
HP Steam
Condensate LP Steam
Type of Cogeneration SystemsType of Cogeneration Systems
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• Steam obtained by extraction from an intermediate stage
• Remaining steam is exhausted
• Relatively high capital cost, lower total efficiency
• Control of electrical power independent of thermal load
Extraction Condensing Steam Turbine
Ther m
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Boiler Turbine
Process
HP Steam
LP SteamCondensate
Condenser
Fuel
Figure: Extraction condensing steam turbine
Type of Cogeneration SystemsType of Cogeneration Systems
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• Operate on thermodynamic “Brayton cycle”• atmospheric air compressed, heated,
expanded• excess power used to produce power
• Natural gas is most common fuel
• 1MW to 100 MW range
• Rapid developments in recent years
• Two types: open and closed cycle
Gas Turbine Cogeneration SystemTher m
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ogener ation
Type of Cogeneration SystemsType of Cogeneration Systems
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• Open Brayton cycle: atmospheric air at increased pressure to combustor
Open Cycle Gas TurbineTher m
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Air
G
Compressor Turbine
HRSG
CombustorFuel
Generator
Exhaust Gases
Condensate from Process
Steam to Process
• Old/small units: 15:1 New/large units: 30:1
• Exhaust gas at 450-
600 oC
• High pressure steam produced: can drive steam turbine Figure: Open cycle gas turbine cogeneration
Type of Cogeneration SystemsType of Cogeneration Systems
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• Working fluid circulates in a closed circuit and does not cause corrosion or erosion
• Any fuel, nuclear or solar energy can be used
Ther m
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ogener ation
Closed Cycle Gas TurbineHeat Source
G
Compressor Turbine
Generator
Condensate from Process
Steam to Process
Heat Exchanger
Figure: Closed Cycle Gas Turbine Cogeneration System
Type of Cogeneration SystemsType of Cogeneration Systems
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• Used as direct mechanical drives
Reciprocating Engine Cogeneration SystemsT
her mal E
quipment/
Cogener ation
Figure: Reciprocating engine cogeneration system (UNESCAP, 2000)
• Many advantages: operation, efficiency, fuel costs
• Used as direct mechanical drives
• Four sources of usable waste heat
Type of Cogeneration SystemsType of Cogeneration Systems
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• Supplied fuel first produces power followed by thermal energy
• Thermal energy is a by product used for process heat or other
• Most popular method of cogeneration
Topping CycleTher m
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Type of Cogeneration SystemsType of Cogeneration Systems
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Bottoming CycleTher m
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• Primary fuel produces high temperature thermal energy
• Rejected heat is used to generate power
• Suitable for manufacturing processes
Type of Cogeneration SystemsType of Cogeneration Systems
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Training Agenda: CogenerationTraining Agenda: Cogeneration
Ther m
al Equipm
ent/C
ogener ation
Introduction
Types of cogeneration systems
Assessment of cogeneration systems
Energy efficiency opportunities
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Assessment of Cogeneration Assessment of Cogeneration SystemsSystems
• Overall Plant Heat Rate (kCal/kWh):
Ms = Mass Flow Rate of Steam (kg/hr)hs = Enthalpy of Steam (kCal/kg)hw = Enthalpy of Feed Water (kCal/kg)
• Overall Plant Fuel Rate (kg/kWh)
Performance Terms & DefinitionsTher m
al Equipm
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)(
)(
kWOutputPower
hwhsxMs
)(
)/(*
kWOutputPower
hrkgnConsumptioFuel
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• Steam turbine efficiency (%):
Steam Turbine PerformanceTher m
al Equipm
ent/C
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Gas Turbine Performance• Overall gas turbine efficiency (%) (turbine
compressor):
100)/(
)/(x
kgkCalTurbinetheacrossdropEnthalpyIsentropic
kgkCalTurbinetheacrossDropEnthalpyActual
100)/()/(
860)(x
kgkCalFuelofGCVxhrkgTurbineGasforInputFuel
xkWOutputPower
Assessment of Cogeneration Assessment of Cogeneration SystemsSystems
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• Heat recovery steam generator efficiency (%):
Ms = Steam Generated (kg/hr)
hs = Enthalpy of Steam (kCal/kg)
hw = Enthalpy of Feed Water (kCal/kg)
Mf = Mass flow of Flue Gas (kg/hr)
t-in = Inlet Temperature of Flue Gas (0C)
t-out= Outlet Temperature of Flue Gas (0C)
Maux = Auxiliary Fuel Consumption (kg/hr)
Heat Recovery Steam Generator (HRSG) Performance
Ther m
al Equipm
ent/C
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100)]/([)]([
)(x
kgkCalFuelofGCVxMttCpxM
hhxM
auxoutinf
wss
Assessment of Cogeneration Assessment of Cogeneration SystemsSystems
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Training Agenda: CogenerationTraining Agenda: Cogeneration
Ther m
al Equipm
ent/C
ogener ation
Introduction
Types of cogeneration systems
Assessment of cogeneration systems
Energy efficiency opportunities
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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
Steam turbine:
• Keep condenser vacuum at optimum value
• Keep steam temperature and pressure at optimum value
• Avoid part load operation and starting & stopping
Boiler & steam – see other chapters
Steam Turbine Cogeneration System
Ther m
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Energy Efficiency OpportunitiesEnergy Efficiency Opportunities
Gas Turbine Cogeneration System
Ther m
al Equipm
ent/C
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Gas turbine – manage the following parameters:
• Gas temperature and pressure• Part load operation and starting & stopping• Temperature of hot gas and exhaust gas• Mass flow through gas turbine• Air pressure
Air compressors – see compressors chapter
Heat recovery system generator – see waste heat recovery chapter