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Unit -2 Power Plants Steam power plant Steam power plant Layout Layout Boilers Boilers Pulverized coal burners Pulverized coal burners Fluidized bed combustion.

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Presentation on theme: "Unit -2 Power Plants Steam power plant Steam power plant Layout Layout Boilers Boilers Pulverized coal burners Pulverized coal burners Fluidized bed combustion."— Presentation transcript:

1 Unit -2 Power Plants Steam power plant Steam power plant Layout Layout Boilers Boilers Pulverized coal burners Pulverized coal burners Fluidized bed combustion Fluidized bed combustion

2 Power generating units are mega projects Power generating units are mega projects Require huge capital investment Require huge capital investment Require natural resources like, fossil fuels Require natural resources like, fossil fuels Large amount of water Large amount of water Changes the local eco system Changes the local eco system Huge Impacts on the Environment and Health Huge Impacts on the Environment and Health

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6 Coal Mining Surface Mining Surface Mining Strip Mining Strip Mining Underground Mining Underground Mining

7 Air Quality Around the coal based plants the ambient concentrations of Sulphur Dioxide, Oxides of Nitrogen and SPM are high. Around the coal based plants the ambient concentrations of Sulphur Dioxide, Oxides of Nitrogen and SPM are high. Epidemiological Studies have shown that of the area surrounding coal based thermal plants, population living within a 2 -5 km radius of the plant suffers from respiratory disorders. Epidemiological Studies have shown that of the area surrounding coal based thermal plants, population living within a 2 -5 km radius of the plant suffers from respiratory disorders. Two other gases, carbon dioxide and ozone are emitted. The high amount of carbon dioxide emission from thermal power plants contribute to global warming leading to climate change is significant Ground level ozone, which is formed due to photolytic reactions of NO x and its impacts are under study Two other gases, carbon dioxide and ozone are emitted. The high amount of carbon dioxide emission from thermal power plants contribute to global warming leading to climate change is significant Ground level ozone, which is formed due to photolytic reactions of NO x and its impacts are under study

8 Fly ash contains a toxic brew of dangerous chemicals and is the largest contributor to mercury pollution

9 Composition of Fly ash Composition of Fly ash It contains as main chemical components SiO2 (51.4 wt%), Al2O3 (22.1 wt%) and Fe2O3 (17.2 wt%; ignited weight basis). As commonly observed, many toxic elements and heavy metals are highly enriched in the fly ash relative to the original coal. For example, considerable amounts of Be (16.4 ppm), Cu (106 ppm), Zn (578 ppm), As (40.4 ppm), Cd (2.6 ppm), Hg (18 ppm), Pb (71 ppm), and U (21.8 ppm) is found in Fly ash.

10 Water slurry is used to take the ash from the power plant to the ash pond for disposal. Water slurry is used to take the ash from the power plant to the ash pond for disposal. Water slowly seeps into the ground while carrying with it the ash leach ate. Water may contain harmful heavy metals like boron, which have a tendency to leach out over a period of time. Water slowly seeps into the ground while carrying with it the ash leach ate. Water may contain harmful heavy metals like boron, which have a tendency to leach out over a period of time. When fly ash comes into contact with water, leaches into groundwater supplies which get polluted and unsuitable for domestic use. When fly ash comes into contact with water, leaches into groundwater supplies which get polluted and unsuitable for domestic use. The release of ash pond decant into the local water bodies- water dries up, dust nuisance, increases turbidity, decreases primary productivity, affects fishes and other aquatic biota The release of ash pond decant into the local water bodies- water dries up, dust nuisance, increases turbidity, decreases primary productivity, affects fishes and other aquatic biota

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12 Coal Power Plant Operation Steam Turbine Generator Steam Turbine Generator Is a series of steam turbines interconnected to each other and then a generator Is a series of steam turbines interconnected to each other and then a generator Steam Condenser Steam Condenser Steam enters from the turbine generator and is pumped into the bottom of the condenser, where pumps recycle the condensed steam from the feedwater Steam enters from the turbine generator and is pumped into the bottom of the condenser, where pumps recycle the condensed steam from the feedwater Stack Stack Releases process emissions. Releases process emissions.

13 What is a Boiler? Introduction 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

14 Introduction BURNER WATER SOURCE BRINE SOFTENERS CHEMICAL FEED FUEL BLOW DOWN SEPARATOR VENT VENT EXHAUST GAS STEAM TO PROCESS STACK DEAERATOR PUMPS Figure: Schematic overview of a boiler room BOILER ECO- NOMI- ZER

15 Types 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!)

16 Type of Boilers 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

17 Type 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

18 Type of Boilers 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

19 Type 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

20 Type 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

21 Type of Boilers 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

22 Type 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

23 Type of Boilers 5. Stoke Fired Boilers b) 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

24 Type of Boilers Tangential firing 6. Pulverized Fuel Boiler Pulverized coal powder blown with combustion air into boiler through burner nozzles Combustion temperature at °C Benefits: varying coal quality coal, quick response to load changes and high pre- heat air temperatures

25 Type 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


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