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Chemical Structure of Coal(Depending upon source, structure may be widely different) Anthracite Coal Carbon 92-98%
COAL : DEFINITIONCoal is a stored fossil fuel, occurring inlayers in the earth’s crust, which hasbeen formed by the partial decay ofplant materials accumulated millions ofyears ago and further altered by theaction of heat and pressure.
THEORIES OF COAL FORMATION IN SITU THEORY DRIFT THEORY - Flood /Tsunami type wave (velocity 800 km/h) 300 million of years (earth is 4.6 billion years old) 15-20 m OF PLANT MATERIAL= 1 m OF COAL SEAM In INDIA 30 m seam of coal has been found450-600 m of plant material might haveaccumulated at that place.(Taipei 101:509 m tallest building in world)
COAL RANKS1.Peat: starting point of coal formation does not come in the category of coal Carbon: 60-64%; Oxygen:35-30%2. Lignites: mark the transition of peat to coal Carbon: 60-75% ; Oxygen: 30-20% Colour: black, brown, earthy Disintegrate very easily Briquetting is done Neyveli Lignite Corporation, Chennai, Tamilnadu Possesses largest reserves of Lignite in India Electricity generation: 2490 MW
COAL RANKS contd…3. Bituminous coals Sub-bituminous: Between lignites and bituminous Carbon: 75-83% ; Oxygen: 20-10% No caking power (Briquettes can not be made)Bituminous: black and bandedIndustrial and domestic usageCarbon: 75-90%: Oxygen:10-5%Semi-bituminous:Between bituminous and anthraciteMetallurgical coke formationCarbon: 90-93%; Oxygen:4-1%
COAL RANKS contd…4. Anthracites Highest rank of coal Extreme of metamorphosis from the original plant material Carbon: 93+%: Oxygen: 2-1% Caking power zeroUnusual coalsCannels: found rarely; high hydrogen content: burnwith smoke and bright flame; does not fall in any category.Torbanites: fine grained coal, named after Torbane Hillof Scotland, rich in paraffin oil.
Unusual Solid Fuel (Methane Clathrate) Burning Ice 1 mole methane in 5.75 mole H 2O Available in Deep sea (methane from trench + cold water + high pressure) and at the lower ice layer in Antarctica It is expected that 15,000 Gt (21×1015 m3) of methane is available in this form (as compared to 1,000 Gt of Coal)
WORLD PRODUCTION OF COAL IN YEAR 2006 % of world production Country Million tonnesChina 2380 39.75USA 1053.6 17.59India 447.3 7.47Australia 373.8 6.24South Africa 256.9 4.29Canada 62.9 1.05United Kingdom 18.6 0.31Pakistan 4.3 0.07Japan 1.3 0.02Total of the world 5,986.90 100
WORLD PRODUCTION OF COAL IN YEAR 2006 Canada United Pakistan South Kingdom Africa Japan Australia India China USA
WORLD TOP TEN COAL PRODUCING AND CONSUMING COUNTRIES 1 quadrillion=1000 trillion 1 Btu=1.055 kJ
COAL RESERVES OF INDIA (As on 1.1.2007 in billion tonnes) TOTAL PROVED INDICATED INFERRED Type of coal RESERVE RESERVE RESERVE RESERVE COKING 32 17 13 2 NON- 223 81 105 36 COKING TOTAL 255 98 118 38Years to consume this coal with present rate: 600 Cokes are the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Source: MoC
GRADING OF INDIAN COAL Coking coal (carbon: 81-91%) Non-coking coal Grades of coking coal Grade Industry Ash % I steel <15 II steel 15-18 I washery* 18-21 II washery* 21-24 III washery* 24-28 IV washery* 28-35* Washed Coal is used as fuel in thermal power plants
GRADING OF INDIAN COAL High ash content (up to 50%) Lower heating/calorific value Inferior quality but suitable for power gen.Grades of non-coking coalGrade UHV, kcal/kg Ash %A >6200 <13.56B 5600-6200 13.56-17.91C 4940-5600 17.91-22.69D 4200-4940 22.69-28.06E 3360-4200 28.06-34.14F 2400-3360 34.14-41.10G 1300-2400 41.10-49.07UHV:Useful Heating Value Based on 6 % moisture content=8900-138×[ash% + moisture%]
ROYALTY TO STATES Nationalization in 1971 Coal companies are paying the royalty to states This varies from Rs 90-250/tonne The rate is dependent of coal grade Rates are 16 August 2002 onwards
IMPORT OF COALCoking and non-coking coals being imported Year Coking Non-coking Total 1991/92 5.27 0.66 5.93 1996/97 10.62 2.56 13.18 2000/01 11.06 9.87 19.70 2003/04 12.99 8.69 21.68 2005/06 16.89 21.70 38.59 2006/07 22.00 23.00 45.00 In million tonnes
ANALYSIS OF COAL Proximate analysis Ultimate analysis Heating/calorific value
PROXIMATE ANALYSIS1. Moisture content: 105 -110 oC2. Volatiles: 925±15 oC for 7 min time (with lid)3. Fixed carbon: by difference4. Ash: 800±15 oC (without lid)REPORTING: AS RECEIVED BASIS, MOISTURE FREEBASIS/DRY BASIS OR DRY ASH FREE BASISIS:1350-I (1984)
EXAMPLE OF PAA sample of finely ground coal of mass 0.9945 g wasplaced in a crucible of 8.5506 g in an oven, maintained at105 oC for 4.0 ks. The sample was then removed, cooled ina dessicator and reweighed; the procedure being repeateduntil a constant total mass of 9.5340 g was attained. Asecond sample, of mass 1.0120 g in a crucible of mass8.5685 g was heated with a lid in a furnace at 920 oC for420 s. On cooling and reweighing, the total mass was9.1921 g. This sample was then heated without a lid in thesame furnace maintained at 725 oC until a constant totalmass of 8.6255 g was attained. Calculate the proximateanalysis of the sample and express the results on “assampled” and “dry, ash-free” basis.
EXAMPLE OF PA contd..MOISTURE (from first sample) mass of sample = 0.9945 g mass of dry coal = (9.5340-8.5506) = 0.9834 g mass of moisture = (0.9945-0.9834) = 0.0111 g % moisture = 0.0111 × 100/0.9945 = 1.11 % ASH (from second sample) Mass of sample = 1.0120 g Mass of crucible = 8.5685 gHeating up to 920ºC in absence of air removes volatile matters,subsequent heating up to 725ºC in presence of air burns allfixed carbon of the sample leaving behind ash in the crucible. Mass of ash (remnant in crucible) = (8.6255 - 8.5685) = 0.0570 g % ash = 0.0570 × 100/1.0120 = 5.63 %
EXAMPLE OF PA contd..VOLATILE MATTER Initial mass of sample + crucible = 1.0120 + 8.5685 = 9.5805 g Final mass after heating up to 920ºC (without air) = 9.1921 g Mass of volatile matter + moisture = Initial – Final mass = (9.5805-9.1921) g = 0.3884 g % Moisture + Volatiles = 0.3884 x 100/1.0120 = 38.3794 %% VOLATILE MATTER = 38.3794 – 1.11 (% Moisture) = 37.26 %FIXED CARBON % FC = 100 - % VM - % ash - % moisture = 100 – 37.26 - 5.53 - 1.11 = 55.98 %
EXAMPLE OF PA contd..Proximate analysis as received basis Moisture : 1.11 % Ash : 5.63 % Fixed carbon : 55.99 % Volatile matter : 37.26 %Proximate analysis on dry, ash free basis Moisture + ash = 1.11 + 5.63 = 6.74% Fixed carbon: 55.99x100/(100-6.74) = 60.04 % Volatile matter: 37.26x100/(100-6.74) = 39.95 %
ULTIMATE ANALYSIS1. Carbon2. Hydrogen3. Oxygen4. Sulfur :0.5-2.50 %5. Nitrogen :1.0-2.25 %6. Phosphorus :0.1%;Blast Furnace: <0.01 %7. ChlorineMercury: A big problem from NTPC plants(up to 0.3mg/kg)IS:1350- IV (1974)
HEATING VALUE1. Calculated from proximate analysis2. Calculated from ultimate analysis3. Experimental determination1. Gross/High heating value2. Useful/low heating value Hydrogen Water (gas/vapor or liquid phase) Carbon Carbon Dioxide (gas phase) Latent heat of vaporization of water: 2.26 MJ/kg
HEATING VALUE1. Calculated from proximate analysisTAYLOR AND PATTERSON RELATIONSHIPHV=4.19 (82FC+ a VM) kJ/kgWhere FC and VM are on dry ash free basis and a isan empirical constant which depends on the VMcontent of coal. 170 160 150 140 130 120 110 100 90 80 0 10 20 30 40VM 5 10 15 20 25 30 35 38 40a 145 130 117 109 103 98 94 85 80
HEATING VALUE2. Calculated from ultimate analysisDULONG FORMULAHV=338.2C+1442.8(H-O/8)+94.2S kJ/kgWhere C, H, O and S are the % of these elements ondry ash free basis.
HEATING VALUE3. Experimental determination: Bomb calorimeter solid /liquid samples can be analyzed 1 g air dried sample is burnt in a bomb in oxygen atmosphere rise in temperature gives the heat liberated and heating value is determined after doing the corrections for resistance wire and thread. microprocessor based bomb calorimeters are now availableIS:1350-II (1970)
VARIOUS COMPONENTS OF BOMB CALORIMETERIC EQUIPMENT
ROUTES OF GENERATION OF HEAT AND POWER FROM COAL1. Direct use as thermal energy in heating processes, furnaces and domestic heating by open fires2. Transfer of the heat to a thermal fluid and application of the latter for heating and power e.g., steam for heating in process industry, central heating and electricity generation by steam turbines3. Gas turbine route to electricity generation4. Conversion to gas/liquid fuels and subsequent usage in IC engines/turbines (gas/steam)
ROUTE I (Direct Heating) Domestic cooking (Chula at tea stalls, dhaba, bakery) Space heating (Fireplace) Lime and brick kilns (Direct heating of stack) Ceramic industry (Oven/Furnace)
ROUTE II (Thermal Fluid) Generation of steam in a boiler Space heating by transferring heat of steam to air Process industry : Cogeneration is employed Utility services : steam turbines usedSUPERCRITICAL BOILERS: A RECENT CONCEPTCritical pressure: 218 bar (21.8 MPa); Critical temperature: 374oCMark Benson; in 1922 Patent was granted22 MPa pressure ; η= 1-T1/T2 ≈ 0.53GOVERNMENT ALLOWED ELECTRICITY GENERATIONBY PRIVATE DEVELOPERS Tariffing Wheeling Banking
ROUTE II contd.. Hot air for Heat space Coal Boiler Steam exchanger heating Steam Air Condensate Steam Cogeneration Steam turbine Alternator to gridAlternator Electricity Condensate Steam Steam turbineElectricity to grid Process plant
ROUTE IIICoal Vent Preheated airPulverizer Heat exchanger Turbine exhaust Combustion chamber Gas turbine Compressor Alternator Air Electricity to grid
ROUTE III Vent Preheated air Heat exchanger Turbine exhaust Combustion chamber Gas turbine Compressor AlternatorCoal Air Electricity Gasifier and gas to grid cleaning unit
ROUTE IV (Pyrolysis / Gasification)1. Partial Gasification or Pyrolysis /coking /carbonization / destructive distillation (heating in the absence of air) • Solid • Liquid • Gas2. Complete gasification with air/oxygen • Gas
PYROLYSISLow temperature carbonization 500-700 oC Coke (solid fuel) maximum; classical domestic smokeless fuel productionMedium temperature carbonization 700-900 oC Liquid fraction for chemicals recovery/liquid fuelHigh temperature carbonization >900 oC Coke for metallurgical furnaces; gas yield high; liquid low
PYROLYSIS Coal Pretreatment unit Water in GasFlue gas for IC engines/ Gas turbines/ Pyrolyser Condenser thermal applications Water out Coke Liquid Coal tar fraction Liquid fuels Chemicals Gas for heating of pyrolyser
ROUTE IV BERGIUS PROCESSCoal is hydrogen starved/hydrogen needs to be added to make itliquid (directly or indirectly)1. Bergius process Friedrich Karl Rudolf Bergius (Germany) in 1913, Nobel Prize in 1931 (Shared with Carl Bosch) By end of World war II – most of the fuel for German army was produced by this method. Hydrogenation of vegetable oils2. Fischer-Tropsch process Franz Fischer and Hans Tropsch in 1926, Germany
F-T PROCESS Coal T=150-250 oC P= 1 -25 Mpa Catalysts : Fe, Co Fractionating column Gasification unit HCs F-TSyn gas Reactor Syn gas Cleaning (Large number of patents worldwide)
F-T PROCESS (COMMERCIAL PLANTS) South Africa Oil and Gas Company 1950 established Oldest plant proving the F-T process viability Presently engaged in Qatar, Iran and Nigeria in similar projects
UNDERGROUND/ IN SITU COAL GASIFICATIONA process applied to the non-mined coal seamsInjection and production wells are drilledEnd gas mix depends on type of coal seamAir/ oxygen can be used for gasificationSyn gas can be used for power generation in combined cycleSyn gas can be converted to chemicals/fuel by F-T process
UNDERGROUND/ IN SITU COAL GASIFICATION Source: World Coal Institute
COAL COMBUSTION AND ENVIORNMENT Global warming Green house gases: water vapor, carbon dioxide, methane, nitrous oxide, HFCs (hydrofluorocarbons), PFCs (perfluorocarbons), SF6 (Sulphur Hexafluoride) SF6 is 22, 200 more potential than CO2 Carbon dioxide gas: main culprit from fossil fuels; not from biomass Intergovernmental Panel on Climate Change (IPCC) Nobel Peace Prize 2007 : R. K. Pauchari and Al Gore Reduction in Carbon Dioxide emissions G8 meeting in Japan in July 2008
COAL COMBUSTION AND ENVIORNMENT Present CO2 level:483 PPMCarbon Dioxide Emissions and Carbon Dioxide Concentrations (1751-2004)
COAL COMBUSTION AND ENVIORNMENT Global Carbon Cycle (Billion Metric Tons Carbon)
COAL COMBUSTION AND ENVIORNMENTU.S. Anthropogenic Greenhouse Gas Emissions by Gas,2006 (Million Metric Tons of Carbon Dioxide Equivalent)
ULTIMATE SOLUTIONSSolar: photovoltaicFuel cells: Chemical to electrical conversionHybrid vehicles: Honda introduced in India
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