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STEAM GENERATION
BOILER
A ‘Boiler’ means a pressure vessel in which steam is generated for use external to itself by application of heat which is wholly or partly under pressure when steam is shut off but does not include a pressure vessel
(1) With Capacity less than 25 ltrs (such capacity being measured from the feed check valve to the main steam stop valve);
(2) With less than 1 kilogram per centimeter square design gauge pressure & working gauge pressure
(3) In which water is heated below one hundred degree centigrade
Fuel Used In Boiler
S.No Solid Liquid Gaseous AgroWaste 1 Coal HSD NGas Baggase 2 Lignite LDO Bio Gas Pith 3 Charcoal Fur.Oil Rice Husk 4 LSHS Paddy Straw 5 Coconut shell 6 Groundnutshell
MSW/RDF
Type Of Boiler
1. Fire Tube Boiler
2. Water Tube Boiler
3. Packaged Boiler
4. Stoker Fired Boiler
5. Pulverized Fuel Boiler
6. Waste Heat 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• 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
Oil Burner
To Chimney
4.Stoker Fired Boiler
Uses both suspension and grate burning
Coal fed continuously over burning coal bed
Coal fines burn in suspension and larger coal pieces burn on grate
Good flexibility to meet changing load requirements
Preferred over other type of stokers in industrial application
a) Spreader strokers
Uses both suspension and grate burning
Coal fed continuously over burning coal bed
Coal fines burn in suspension and larger coal pieces burn on grate
Good flexibility to meet changing load requirements
Preferred over other type of stokers in industrial application
b) Chain-grate or Travelling-grate stoker
5.Pulverized Fuel Boiler
Coal is pulverized to a fine powder, so that less than 2% is +300 microns, and 70-75% is below 75 microns.Coal is blown with part of the combustion air into the boiler plant through a series of burner nozzles.
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
(contd…..)
Advantages
Its ability to burn all ranks of coal from anthracitic to lignitic, and it permits combination firing (i.e., can use coal, oil and gas in same burner). Because of these advantages, there is widespread use of pulverized coal furnaces.
Disadvantages
High power demand for pulverizing Requires more maintenance, flyash erosion and pollution
complicate unit operation
6.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
Pricinple of Operation
Combustion of fuel produce heat, which is transferred to the container and makes the water evaporate. The vapor or steam can escape through a pipe that is connected to the container and be transported elsewhere . Another pipe brings water (called “feedwater”)to the container to replace the water that has evaporated and escaped. Since the pressure level in the boiler should bekept constant (in order to have equal to the mass of the water that is added. If steam leaves the boiler faster than water is added, the pressure in the boiler falls stable process values), the mass of the steam that escapes has to be. If water is added faster than it is evaporated, the pressure rises .If more fuel is combusted, more heat is generated and transferred to the water. Thus, more steam is generated and pressure rises inside the boiler. If less fuel is combusted, less steam is generated and the pressure sinks.
BURNERWATER
SOURCE
SOFTENERSCHEMICAL FEED
FUELBLOW DOWN SEPARATOR
VENT
STACK DEAERATOR
PUMPS
BOILER
ECO-NOMI-ZER
VENTEXHAUST GASSTEAM TO PROCESS
Pricinple of Operation
Deaerator
A deaerator is used to strip corrosive gases from boiler feed water by sparging with steam.
Safety Consideration Boiler firebox Main stop valve Safety valve Smoke Tube Gas Burner
Reference http://en.wikipedia.org/w/index.php?
search=steam+generation&title=Special%3ASearch&go=Go
http://www.ttboilers.dk/steamgenerator_steamboiler.htm
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