lecture 29 boilers
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Vividha Dhapte M. Pharm
Lecture 29
BOILERS
Lecture in Pharma EngineeringDept. of Pharmaceutics,
Marathwada Mitra Mandal’s COLLEGE OF PHARMACY, Pune
Contents1.Classification
Classification of Boilers
1. Fire Tube Boiler2. Water Tube Boiler3. Packaged Boiler4. Fluidized Bed (FBC) Boiler5. Stoker Fired Boiler6. Pulverized Fuel Boiler7. Waste Heat Boiler8. Thermic Fluid Heater (not a boiler!)
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
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
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
efficiencyClassified based on
number of passes
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 SO2 & NO2
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
4c. Atmospheric Circulating Fluidized Bed Combustion (CFBC) Boiler
Solids lifted from bed, rise, return to bed
Steam generation in convection section
Benefits: more economical, better space utilization and efficient combustion
5. Stoke Fired Boilersa) Spreader stokers Coal is first burnt in suspension
then in coal bed Flexibility to meet load fluctuations Favored in many industrial
applications
5. Stoke Fired Boilersb) Chain-grate or traveling-grate stoker
Coal is burnt on moving steel grate
Coal gate controls coal feeding rate
Uniform coal size for complete combustion
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
7. Waste Heat Boiler Used when waste heat
available at medium/high temp
Auxiliary fuel burners used if steam demand is more than the waste heat can generate
Used in heat recovery from exhaust gases from gas turbines and diesel engines
8. Thermic Fluid Heater Wide application for indirect process heating Thermic fluid (petroleum-based) is heat
transfer medium Benefits:
Closed cycle = minimal lossesNon-pressurized system operation at 250 °C
Automatic controls = operational flexibilityGood thermal efficiencies
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
Water tube boiler Fire tube boiler1. When water is contained inside thetubes (called water tube) which aresurrounded by flames and hot gasesfrom outside, then the boilers arenamed as water tube boilers.
1. When the flames and hot gases,produced by combustion of fuel, passthrough the tubes (called multitubes)which are surrounded by water, then the boilers are named as fire tube boilers
2. They are safe, quick steaming,flexible in construction and operation.
2. They have an advantage of low cost and compact design.
3. These boilers are extensively usedbecause they can be built for high pressure and large evaporative capacities.
3. They are used where steam pressure does not exceed about 10 bar and where moderate quantity of steam is required.
4. Examples: Babcock and Wilcox boiler, sterling boiler, Lamont boiler, Benson Boiler, loeffler boiler
4. Examples: simple vertical boiler, Lanchashire boiler, Cocharn boiler, Locomotive boiler.
References• en.wikipedia.org/wiki/Boiler • www.sazboilers.com
Questions
1. Give classification of Boilers.2. Compare between water tube and fire
tube boiler
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