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1、A presentation on Steam Generator,Coal to Electricity.Basics,Major EnergySources of India,Why Coal?,Share of Coal in Power Generation,Advantages of Coal FuelAbundantly available in IndiaLow costTechnology for Power Generation well developed.Easy to handle,transport,store and use,Shortcomings of Coal
2、Low Calorific ValueLarge quantity to be HandledProduces pollutants,ashDisposal of ash is ProblematicReserves depleting fast,Indias Coal Reserves are estimated to be 206 billion tonnes.Present consumption is about 450 million tonnes.Cost of coal for producing 1 unit of electricity(Cost of coal Rs 100
3、0/MT)is Rs 0.75.Cost of Gas for producing 1 unit of electricity(Cost of Gas Rs 6/SMC)is Rs 1.20.,Knowing more about Coal,Coal productionSurface MiningUnderground Mining,Coal TransportationRailTruckConveyorShip,Coal PropertiesCalorific ValueGrade of Coal(UHV)Proximate AnalysisUltimate AnalysisAsh and
4、 MineralsGrindabilityRankPhysical Characteristics,Coal BeneficiationWhy?ProcessesEffectiveness,Coal productionSurface MiningUnderground Mining,Useful Heat Value(UHV)UHV=8900-138(A+M),Boiler/steam generator,Steam generating device for a specific purpose.Capable to meet variation in load demand Capabl
5、e of generating steam in a range of operating pressure and temperatureFor utility purpose,it should generate steam uninterruptedly at operating pressure and temperature for running steam turbines.,Boiler/steam generator,Raw materials for design of boilersCoal from minesAmbient air Water from natural
6、 resources(river,ponds),Generating heat energyAir for combustionWorking fluid for steam generation,possessing heat energy,A 500MW steam generator consumes about 8000 tonnes of coal every dayIt will be considered if it requires about 200 cubic meter of DM water in a dayIt will produce about 9500 tonn
7、es of Carbon di Oxide every day,Coal analysis,Typical composition(Proximate analysis)1.Fixed carbon2.Fuel ash3.Volatile material4.Total Moisture5.SulfurHigh calorific value/Lower calorific value(Kcal/kg)Hardgrove Index(HGI),Combustion of coal,Carbon,hydrogen,sulfur are sources of heat on combustionS
8、urface moisture removed on heating during pulverization.Inherent moisture and volatiles are released at higher temperature,making coal porous and leading to char/coke formation.(Thermal preparation stage),Fuel Oil,Three liquid fuels used in power plants1.Heavy Fuel Oil(HFO)2.LSHS(Low Sulfur Heavy st
9、ock)3.High speed Diesel(HSD)Oil firing is preceded byLowering viscosity and increasing flowability on heating for better combustion in given turn down ratio.(125oC)Droplet formation on atomization(by steam/compressed air/mechanical pressurization)Combustion initiation by High energy spark ignition,C
10、ombustion of reactants,Reaction rate depends on concentration of one of the reactantsConcentration varies on partial pressure of the reactants.Partial pressure is a function of gas temperature.Therefore,reaction rate depends on temperature and substance that enter the reaction.,Combustion Reactions(
11、Carbon),Main reactions 2C+O2=2CO+3950 BTU/lb(Deficit air)C+O2=CO2+14093 BTU/lb Secondary reactions2CO+O2=2CO2+4347BTU/lbC+CO2=2CO-7.25MJ/kg,Combustion Reactions(Carbon),Carbon reaction 2C+O2=2COEco=60kJ/molC+O2=CO2Eco2=140kJ/molreaction at 1200oC4C+3O2=2CO+2CO2(Ratio 1:1)Reaction at 1700oC3C+2O2=2CO
12、+CO2(Ratio 2:1)It is desirable to supply combustion air at lower temperature regime in furnace,Combustion Reaction(H2,S),Hydrogen reaction2H2+O2=2H2O+61095 BTU/lbSulfur reactionS+O2=SO2+3980 BTU/lb(undesirable),Coal for combustion,AnthraciteSemi-anthraciteBituminousSemi-BituminousLignitePeat,High CV
13、,low VMHigh CV,low VMMedium CV,medium VMMedium CV,medium VMLow CV,high VM,high TMVery low CV,high VM&TM,Heat Generation in furnace,Heat input in the furnace Efficiency of thermal power plants is 37%-45%for different types of cycleFor typical conventional P.F.boilers,coal flow rate is 290-350 T/hr Fo
14、r 500 MW units120-145 T/hrFor 200 MW units,Tangential Firing System,MAIN EQUIPMENTS OF FUEL&FIRING SYSTEM,MILLS OR PULVERISERS FEDDERS BURNERS,TYPES OF FEEDERS VOLUMETRIC FEEDRES GRAVIMETRIC FEEDERS,PULVERIZERS,OBJECTIVES TO CRUSHED THE COAL REDCED TO A FINENESS SUCH THAT 70-80%PASSES THROUGH A 200M
15、ESH SIEVE,ADVANTAGES OF PULVERISED COAL FIRING,EFFICIENT UTILISATION OF CHEAPER GRADE OF COALS FLEXIBILITY IN FIRING WITH ABILITY TO MEET FLUCTUATING LOADS BETTER COAL COMBUSTION INCREASING THE BOILER EFFICIENCY HIGH AVAILIBILITY,BOWL MILL,Model no.Base capacity(T/Hr)623XRP 18.4703XRP 26.4763XRP 33.
16、8803XRP 36.5883XRP 51.1903XRP 54.11003XRP 68.11043XRP 72.0,BASE CAPACITY(T/HR)AT HGI-55Total Moisture-10%Fineness-70%THRU 200 MESH,BALL&RACE MILL(E MILL),Model no.Base capacity(T/Hr)7E9 258.5E10 358.5E9 4010E10 5510.9E11 6110.9E10 7010.9E8 80,TUBE MILL,Model no.Base capacity(T/Hr)BBD4760 83BBD4772 9
17、0,AIR AND DRAFT SYSTEM,OBJECTIVES THE AIR WE NEED FOR COMBUSTION IN THE FURNACE AND FLUE GAS THAT WE MUST EVACUATE TRANSPORT AND DRY THE PULVERISED COAL SEALING OF BEARINGS FROM COAL/DUST,DRAFT SYSTEM,DRAFT MEANS THE DIFFRENCE BETWEEN THE ATMOSPHERIC PRESSRE AND PRESSURE EXISTING IN THE FURNACENATUR
18、AL DRAFT-OBTAINED BY TALL CHIMNEY INDUCED DRAFT-BY ID FANS FORCED DRAFT-BY FD FANS BALANCE DRAFT-BY ID AND FD FANSGENERALLY IN POWER PLANT BALANCE DRAFT SYSTEM IS USED.,FANS IN POWER PLANT,FORCED DRAFT FAN INDUCED DRAFT FAN PRIMARY AIR FAN SEAL AIR FAN SCANNER AIR FAN,THE BASIC INFORMATION NEEDED TO
19、 SELECT A FAN ARE AIR OR GAS FLOW-KG/HR DENSITY(FUNCTION OF TEMPERATURE AND PRESSURE)SYSTEM RESISTANCE(LOSSES),AIR PRE HEATERS,OBJECTIVES TO RAISE THE TEMPERATURES OF PRIMARY AND SECONDARY AIR BY UTILISING HEAT FROM FLUE GAS AT LOW TEMPERATURE,ADVANTAGES OF AIR PREHEATERS,INCREASE THE BOILER EFFICIE
20、NCY STABILITY OF COMBUSTION IMPROVED BY USE OF HOT AIR PERMITTING TO BURN POOR QUALITY COAL,Ljungstrom type Bisector,TWO PASS BOILER ARRANGEMENT,Electro Static Precipitator,To remove fly ash from the flue gases electrostatic precipitators are used.They have collection efficiency over 99.5%The effici
21、ency depends on various parameters such as velocity of flow,quantity of gas,resistivity of ash,voltage of fields,temperature etc,Principle of Operation,The fluegas laden with flyash is sent through ducts having negatively charged plates which give the particles a negative charge.The particles are th
22、en routed past positively charged plates,or grounded plates,which attract the now negatively-charged ash particles.The particles stick to the positive plates until they are collected by periodically rapping.,SELECTION OF BOILER TYPE OF BOILERBased on steam parameter-Subcritical/SupercritacalBased on
23、 steam/water circuit-Once throuh/drum typeBased on air/flue gas path-Tower/Two path/T-typeType of fuel-Coal fired/oil firedType of draft system-Type of burner arrangement-Tangential/Front/opposed Selection of Firing system-Type of millsSingle reheat/double reheat Type of water wall tube-Plain,rifled
24、Type of tubing arrangement-Spiral/straight,Tube leakages from boiler pressure parts.Erosion of tubes due to high ash content and velocitiesOver heating of tubesPassing from valves causing difficulty in maintaining the parametersFailure or incorrectness of measured parametersOverloading of boiler due
25、 to very poor quality of coalDeposition of ash(clinkers)on furnace walls.Difficulties in removal of ash from the boilerReduced effectiveness of heat transfer leading to loss of efficiency.Improper combustion of coal in the boiler.,Typical Boiler Problems,Air ingress from the nose arch,penthouse and
26、boiler second pass and quantification thereof Difference between on line reading and the actual oxygen in the flue gas duct Difference between actual and on line temperature measurement of air heater air/gas outlet temperaturesFouling and SlaggingHigh unburnt Carbon in flyash or bottomashHigh air he
27、ater leakage Boiler operation at high excess air,Typical Boiler Problems contd.,A Few words on Super Critical Boiler,Definition“CRITICAL”is a thermodynamic expression describing the state of a substance beyond which there is no clear distinction between the liquid and gaseous phase.The critical pres
28、sure&temperature for water are Pressure=225.56 Kg/cm2Temperature=374.15 C,SUPERCRITICALTHERMAL CYCLE ADVANTAGES(1),Improvements in plant efficiency by more than 2%Decrease in Coal ConsumptionReduction in Green House gases.Overall reduction in Auxiliary Power consumption.Reduction in requirement of A
29、sh dyke Land&Consumptive water.,SUPERCRITICAL ADVANTAGES(2),Sliding pressure operation because of Once through system.Even distribution of heat due to spiral wall arrangement leading to less Boiler tube failure,thereby improving system continuity and availability of the station.Low thermal stress in Turbine.The startup time is less for boiler.,SUPERCRITICAL DISADVANTAGES,Higher power consumption of BFPHigher feed water quality required.More complex supporting and framing in Boiler due to Spiral Wall tubes.Slight higher capital cost.,COMPARISION OF 660 MW Vs 500 MW BOILER,
