Presentation on theme: "Unit -2 Power Plants Steam power plant Layout Boilers"— Presentation transcript:
1 Unit -2 Power PlantsSteam power plantLayoutBoilersPulverized coal burnersFluidized bed combustion
2 Power generating units are mega projects Require huge capital investmentRequire natural resources like, fossil fuelsLarge amount of waterChanges the local eco systemHuge Impacts on the Environment and Health
3 In a thermal power plant, steam is produced and used to spin a turbine that operates a generator. Shown here is a diagram of a conventional thermal power plant, which uses coal, oil, or natural gas as fuel to boil water to produce the steam. The electricity generated at the plant is sent to consumers through high-voltage power lines.
7 Understanding Coal fired Thermal Power plants Air QualityAround 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 .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 NOx and its impacts are under study
8 Understanding Coal Fired Thermal Power Plants Fly ash contains a toxic brew of dangerous chemicals and is the largest contributor to mercury pollution
9 Understanding Coal fired Thermal Power plants Composition of Fly ashIt 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 Understanding Coal fired Thermal Power plants 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. 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
12 Coal Power Plant Operation Steam Turbine GeneratorIs a series of steam turbines interconnected to each other and then a generatorSteam CondenserSteam enters from the turbine generator and is pumped into the bottom of the condenser, where pumps recycle the condensed steam from the feedwaterStackReleases process emissions.
13 Introduction What is a Boiler? Vessel that heats water to become hot water or steamAt atmospheric pressure water volume increases 1,600 timesHot water or steam used to transfer heat to a processA boiler is an enclosed vessel that provides a means for combustion heat to be transferred to water until it becomes heated water or steam.When water at atmospheric pressure is boiled into steam its volume increases about 1,600 times, producing a force that is almost as explosive as gunpowder. This causes the boiler to be an equipment that must be treated with utmost careThe hot water or steam under pressure is then usable for transferring the heat to a process.
14 Introduction BOILER Figure: Schematic overview of a boiler room STEAM TO PROCESSEXHAUST GASVENTSTACKDEAERATORECO- NOMI- ZERPUMPSBOILERVENTBURNERWATER SOURCEBLOW DOWN SEPARATORFUELBRINECHEMICAL FEEDSOFTENERSFigure: Schematic overview of a boiler room
15 Types of Boilers Fire Tube Boiler Water Tube Boiler Packaged Boiler Fluidized Bed (FBC) BoilerStoker Fired BoilerPulverized Fuel BoilerWaste Heat BoilerThermic 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 requirementsCapacity range of 4,500 – 120,000 kg/hourCombustion efficiency enhanced by induced draft provisionsLower tolerance for water quality and needs water treatment plant
18 Type of Boilers 3. Packaged Boiler Comes in complete package Features High heat transferFaster evaporationGood convective heat transferGood combustion efficiencyHigh thermal efficiencyClassified based on number of passesOil BurnerTo Chimney
19 4. Fluidized Bed Combustion (FBC) Boiler Type of Boilers4. Fluidized Bed Combustion (FBC) BoilerParticles (e.g. sand) are suspended in high velocity air stream: bubbling fluidized bedCombustion at 840° – 950° CCapacity range 0,5 T/hr to 100 T/hrFuels: coal, washery rejects, rice husk, bagasse and agricultural wastesBenefits: 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 air4b. Pressurized Fluidized Bed Combustion (PFBC) BoilerCompressor supplies the forced draft and combustor is a pressure vesselUsed for cogeneration or combined cycle power generation
21 Type of Boilers4c. Atmospheric Circulating Fluidized Bed Combustion (CFBC) BoilerSolids lifted from bed, rise, return to bedSteam generation in convection sectionBenefits: 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 bedFlexibility to meet load fluctuationsFavored in many industrial applications
23 Type of Boilers 5. Stoke Fired Boilers b) Chain-grate or traveling-grate stokerCoal is burnt on moving steel grateCoal gate controls coal feeding rateUniform coal size for complete combustion
24 6. Pulverized Fuel Boiler Type of Boilers6. Pulverized Fuel BoilerPulverized coal powder blown with combustion air into boiler through burner nozzlesCombustion temperature at °CBenefits: varying coal quality coal, quick response to load changes and high pre-heat air temperaturesTangential firing
25 Type of Boilers 8. Thermic Fluid Heater User equipment 3. Heat transfer through heat exchanged8. Thermic Fluid HeaterControl panelBlower motor unitFuel oil filterExhaustInsulated outer wallUser equipment2. Circulated to user equipment4. Fluid returned to heater1. Thermic fluid heated in the heater(Energy Machine India)