View
2.212
Download
62
Category
Preview:
Citation preview
1
Steam BoilersSteam Boilers
2
St eam
Boil ers
Introduction
Type of boilers
Assessment of a boiler
Energy efficiency opportunities
Presentation: BoilerPresentation: Boiler
3
St eam
Boil ers
What is a Boiler?
IntroductionIntroduction
• Vessel that heats water to become hot water or steam
• At atmospheric pressure water volume increases 1,600 times
• Hot water or steam used to transfer heat to a process
4
St eam
Boil ers
IntroductionIntroduction
BURNERBURNERWATER WATER
SOURCESOURCE
BRINEBRINE
SOFTENERSSOFTENERSCHEMICAL FEEDCHEMICAL FEED
FUELFUELBLOW DOWN BLOW DOWN SEPARATORSEPARATOR
VENTVENT
VENTVENTEXHAUST GASEXHAUST GASSTEAM TO STEAM TO PROCESSPROCESS
STACKSTACK DEAERATORDEAERATOR
PUMPSPUMPS
Figure: Schematic overview of a boiler room
BOILERBOILER
ECO-ECO-NOMI-NOMI-ZERZER
5
St eam
Boil ers
Introduction
Type of boilers
Assessment of a boiler
Energy efficiency opportunities
Training Agenda: BoilerTraining Agenda: Boiler
6
St eam
Boil ers
Types of BoilersTypes of Boilers
1. Fire Tube Boiler
2. Water Tube Boiler
3. Packaged Boiler
4. Fluidized Bed (FBC) Boiler
5. Stoker Fired Boiler
6. Pulverized Fuel Boiler
7. Waste Heat Boiler
8. Thermic Fluid Heater (not a boiler!)
What Type of Boilers Are There?
7
St eam
Boil ers
Type of BoilersType of Boilers
(Light Rail Transit Association)
1. Fire Tube Boiler
• Relatively small steam capacities (12,000 kg/hour)
• Low to medium steam pressures (18 kg/cm2)
• Operates with oil, gas or solid fuels
8
St eam
Boil ers
Type of BoilersType of Boilers
2. Water Tube Boiler
• Used for high steam demand and pressure requirements
• Capacity range of 4,500 – 120,000 kg/hour
• Combustion efficiency enhanced by induced draft provisions
• Lower tolerance for water quality and needs water treatment plant
9
St eam
Boil ers
Type of BoilersType of Boilers
BIB Cochran
3. Packaged Boiler
Oil Burner
To Chimney
• Comes in complete package
• Features• High heat transfer• Faster evaporation • Good convective
heat transfer• Good combustion
efficiency• High thermal
efficiency
• Classified based on number of passes
10
St eam
Boil ers
Type of BoilersType of Boilers
4. Fluidized Bed Combustion (FBC) Boiler• Particles (e.g. sand) are suspended in high
velocity air stream: bubbling fluidized bed
• Combustion at 840° – 950° C
• Capacity range 0,5 T/hr to 100 T/hr
• Fuels: coal, washery rejects, rice husk, bagasse and agricultural wastes
• Benefits: compactness, fuel flexibility, higher combustion efficiency, reduced SOx & NOx
11
St eam
Boil ers
Type of BoilersType of Boilers
4a. Atmospheric Fluidized Bed Combustion (AFBC) Boiler
• Most common FBC boiler that uses preheated atmospheric air as fluidization and combustion air
4b. Pressurized Fluidized Bed Combustion (PFBC) Boiler
• Compressor supplies the forced draft and combustor is a pressure vessel
• Used for cogeneration or combined cycle power generation
12
St eam
Boil ers
Type of BoilersType of Boilers
5. Stoke Fired Boilers
a) Spreader stokers
• Coal is first burnt in suspension then in coal bed
• Flexibility to meet load fluctuations
• Favored in many industrial applications
13
St eam
Boil ers
Type of BoilersType of Boilers
5. Stoke Fired Boilers
b) Chain-grate or traveling-grate stoker
(University of Missouri, 2004)
• Coal is burnt on moving steel grate
• Coal gate controls coal feeding rate
• Uniform coal size for complete combustion
14
St eam
Boil ers
Type of BoilersType of Boilers
Tangential firing
6. Pulverized Fuel Boiler
• Pulverized coal powder blown with combustion air into boiler through burner nozzles
• Combustion temperature at 1300 -1700 °C
• Benefits: varying coal quality coal, quick response to load changes and high pre-heat air temperatures
15
St eam
Boil ers
Type of BoilersType of Boilers
8. Thermic Fluid Heater
• Wide application for indirect process heating
• Thermic fluid (petroleum-based) is heat transfer medium
• Benefits:
• Closed cycle = minimal losses
• Non-pressurized system operation at 250 °C
• Automatic controls = operational flexibility
• Good thermal efficiencies
16
St eam
Boil ers
Type of BoilersType of Boilers
(Energy Machine India)
8. Thermic Fluid Heater
Control panel
Blower motor unit
Fuel oil filter
Exhaust
Insulated outer wall
1. Thermic fluid heated in the heater
2. Circulated to user
equipment
User equipment
3. Heat transfer through heat exchanged
4. Fluid returned to
heater
17
St eam
Boil ers
Introduction
Type of boilers
Assessment of a boiler
Energy efficiency opportunities
Training Agenda: BoilerTraining Agenda: Boiler
18
St eam
Boil ers
Assessment of a BoilerAssessment of a Boiler
1. Boiler performance• Causes of poor boiler performance
-Poor combustion-Heat transfer surface fouling-Poor operation and maintenance-Deteriorating fuel and water quality
• Heat balance: identify heat losses
• Boiler efficiency: determine deviation from best efficiency
19
St eam
Boil ers
Assessment of a BoilerAssessment of a Boiler
Heat BalanceAn energy flow diagram describes geographically how energy is transformed from fuel into useful energy, heat and losses
StochiometricExcess AirUn burnt
FUEL INPUT STEAM OUTPUT
Stack Gas
Ash and Un-burnt parts of Fuel in Ash
Blow Down
Convection & Radiation
20
St eam
Boil ers
Assessment of a BoilerAssessment of a Boiler
Heat BalanceBalancing total energy entering a boiler against the energy that leaves the boiler in different forms
Heat in Steam
BOILER
Heat loss due to dry flue gas
Heat loss due to steam in fuel gas
Heat loss due to moisture in fuel
Heat loss due to unburnts in residue
Heat loss due to moisture in air
Heat loss due to radiation & other unaccounted loss
12.7 %
8.1 %
1.7 %
0.3 %
2.4 %
1.0 %
73.8 %
100.0 %
Fuel
73.8 %
21
St eam
Boil ers
Assessment of a BoilerAssessment of a Boiler
Heat Balance
Goal: improve energy efficiency by reducing avoidable losses
Avoidable losses include:
- Stack gas losses (excess air, stack gas temperature)
- Losses by unburnt fuel
- Blow down losses
- Condensate losses
- Convection and radiation
22
St eam
Boil ers
Assessment of a BoilerAssessment of a Boiler
Boiler EfficiencyThermal efficiency: % of (heat) energy input that is effectively useful in the generated steam
BOILER EFFICENCY CALCULATION
1) DIRECT METHOD: 2) INDIRECT METHOD:
The efficiency is the different between lossesand energy input
The energy gain of theworking fluid (water and steam) is compared with the energy content of the boiler fuel.
23
St eam
Boil ers
Assessment of a BoilerAssessment of a Boiler
hg -the enthalpy of saturated steam in kcal/kg of steam
hf -the enthalpy of feed water in kcal/kg of water
Boiler Efficiency: Direct Method
Boiler efficiency () = Heat Input
Heat Outputx 100 Q x (hg – hf)
Q x GCVx 100=
Parameters to be monitored: - Quantity of steam generated per hour (Q) in kg/hr - Quantity of fuel used per hour (q) in kg/hr- The working pressure (in kg/cm2(g)) and superheat
temperature (oC), if any - The temperature of feed water (oC) - Type of fuel and gross calorific value of the fuel (GCV) in
kcal/kg of fuel
24
St eam
Boil ers
Assessment of a BoilerAssessment of a Boiler
Advantages• Quick evaluation• Few parameters for computation • Few monitoring instruments• Easy to compare evaporation ratios with
benchmark figures
Disadvantages• No explanation of low efficiency• Various losses not calculated
Boiler Efficiency: Direct Method
25
St eam
Boil ers
Assessment of a BoilerAssessment of a Boiler
Efficiency of boiler () = 100 – (i+ii+iii+iv+v+vi+vii)
Boiler Efficiency: Indirect Method
Principle losses:i) Dry flue gas
ii) Evaporation of water formed due to H2 in fuel
iii) Evaporation of moisture in fuel
iv) Moisture present in combustion air
v) Unburnt fuel in fly ash
vi) Unburnt fuel in bottom ash
vii) Radiation and other unaccounted losses
26
St eam
Boil ers
Assessment of a BoilerAssessment of a Boiler
Boiler Efficiency: Indirect Method
Advantages• Complete mass and energy balance for each
individual stream• Makes it easier to identify options to improve
boiler efficiency
Disadvantages• Time consuming• Requires lab facilities for analysis
27
Boilers Boilers
THANK YOUTHANK YOUFOR YOUR KIND ATTENTION!!!!!FOR YOUR KIND ATTENTION!!!!!
St eam
Boil ers
Recommended