COAL

Chemical Structure of Coal(Depending upon source, structure may be widely different)

Anthracite Coal Carbon 92-98%

Coal 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.

COAL : DEFINITION

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 found

THEORIES OF COAL FORMATION

450-600 m of plant material might have accumulated at that place.(Taipei 101:509 m tallest building in world)

COALIFICATION COAL % C C H O Heating

value(MJ/kg)

CelluloseWoodPeatLigniteBrown coalBituminous coalAnthraciteGraphite

44.550.059.961.869.578.791.0100

100100100100100100100100

13.912.010.07.87.96.04.70.0

11188575436215.20.0

-19.7718.6620-2527.2032.1032.5632.91

Time

COAL RANKS 1.Peat: starting point of coal formation

does not come in the category of coalCarbon: 60-64%; Oxygen:35-30%

2. Lignites: mark the transition of peat to coalCarbon: 60-75% ; Oxygen: 30-20%Colour: black, brown, earthyDisintegrate very easilyBriquetting is doneNeyveli Lignite Corporation, Chennai, TamilnaduPossesses largest reserves of Lignite in IndiaElectricity 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 banded Industrial 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 coalExtreme of metamorphosis from the original plant materialCarbon: 93+%: Oxygen: 2-1%Caking power zero

Unusual coalsCannels: found rarely; high hydrogen content: burn with smoke and bright flame; does not fall in any category.Torbanites: fine grained coal, named after Torbane Hill of Scotland, rich in paraffin oil.

Unusual Solid Fuel (Methane Clathrate)

Burning Ice 1 mole methane in 5.75 mole

H2O 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)

Country Million tonnes % of world production

China 2380 39.75

USA 1053.6 17.59

India 447.3 7.47

Australia 373.8 6.24

South Africa 256.9 4.29

Canada 62.9 1.05

United Kingdom 18.6 0.31

Pakistan 4.3 0.07

Japan 1.3 0.02

Total of the world 5,986.90 100

WORLD PRODUCTION OF COAL IN YEAR 2006

WORLD PRODUCTION OF COAL IN YEAR 2006

China

USA

India

Australia Japan

Pakistan Canada South Africa

United Kingdom

WORLD TOP TEN COAL PRODUCING AND CONSUMING COUNTRIES

1 quadrillion=1000 trillion1 Btu=1.055 kJ

Type of coal TOTALRESERVE

PROVED RESERVE

INDICATEDRESERVE

INFERREDRESERVE

COKING 32 17 13 2NON-

COKING 223 81 105 36

TOTAL 255 98 118 38

COAL RESERVES OF INDIA

Source: MoC

Years to consume this coal with present rate: 600

(As on 1.1.2007 in billion tonnes)

Cokes are the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal.

State Proved Indicated Inferred Total % of totalJharkhand 36881 31094 6339 74314 29.11Orissa 17464 30239 14296 61999 24.29Chhattisgarh 10182 26826 4443 41451 16.24West Bengal 11454 11810 5071 28335 11.10Madhya Pradesh 7584 9259 2934 19777 7.75Andhra Pradesh 8475 6328 2658 17461 6.84Maharashtra 4856 2822 1992 9670 3.79Uttar Pradesh 766 296 0 1062 0.42Meghalaya 118 41 301 460 0.18Assam 315 27 34 376 0.15Bihar 0 0 160 160 0.06Arunachal Pdesh 31 40 19 90 0.04Sikkim 0 55 18 73 0.03Nagaland 3 1 15 19 0.01Total 98129 118838 38280 255247 100

COAL RESOURCES OF STATES IN MILLION TONNES Jan 1, 2007

Proved: boreholes (1200m deep) @ 400 mIndicated & Inferred: boreholes @ 1-2 km

Coking coal (carbon: 81-91%) Non-coking coal

GRADING OF INDIAN COAL

Grade Industry Ash %I steel <15II steel 15-18I washery* 18-21II washery* 21-24III washery* 24-28IV washery* 28-35

Grades of coking coal

* Washed Coal is used as fuel in thermal power plants

High ash content (up to 50%) Lower heating/calorific value Inferior quality but suitable for power gen.

GRADING OF INDIAN COAL

Grade 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 41.10-49.07

Grades of non-coking coal

UHV:Useful Heating Value=8900-138×[ash% + moisture%]

Based on 6 % moisture content

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

ROYALTY TO STATES

IMPORT OF COAL Coking 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

Proximate analysis Ultimate analysis Heating/calorific value

ANALYSIS OF COAL

1. Moisture content: 105 -110 oC

2. Volatiles: 925±15 oC for 7 min time (with lid)

3. Fixed carbon: by difference

4. Ash: 800±15 oC (without lid)

PROXIMATE ANALYSIS

IS:1350-I (1984)

REPORTING: AS RECEIVED BASIS, MOISTURE FREE BASIS/DRY BASIS OR DRY ASH FREE BASIS

A 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

MOISTURE (from first sample)mass of sample = 0.9945 g mass of dry coal = (9.5340-8.5506) = 0.9834 gmass of moisture = (0.9945-0.9834) = 0.0111 g% moisture = 0.0111 × 100/0.9945

= 1.11 %

EXAMPLE OF PA contd..

ASH (from second sample)Mass of sample = 1.0120 gMass of crucible = 8.5685 g

Heating up to 920ºC in absence of air removes volatile matters, subsequent heating up to 725ºC in presence of air burns all fixed 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 %

VOLATILE MATTERInitial mass of sample + crucible = 1.0120 + 8.5685 = 9.5805 gFinal mass after heating up to 920ºC (without air) = 9.1921 gMass 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 %

EXAMPLE OF PA contd..

FIXED CARBON% FC = 100 - % VM - % ash - % moisture

= 100 – 37.26 - 5.53 - 1.11= 55.98 %

Proximate analysis as received basisMoisture : 1.11 %Ash : 5.63 %Fixed carbon : 55.99 %Volatile matter : 37.26 %

Proximate analysis on dry, ash free basisMoisture + 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 %

EXAMPLE OF PA contd..

1. Carbon2. Hydrogen3. Oxygen4. Sulfur :0.5-2.50 %5. Nitrogen :1.0-2.25 %6. Phosphorus :0.1%;Blast Furnace: <0.01 %7. Chlorine

ULTIMATE ANALYSIS

IS:1350- IV (1974)

Mercury: A big problem from NTPC plants (up to 0.3mg/kg)

1. Calculated from proximate analysis2. Calculated from ultimate analysis3. Experimental determination

HEATING VALUE

1. Gross/High heating value

2. 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

1. Calculated from proximate analysis

HEATING VALUE

TAYLOR AND PATTERSON RELATIONSHIPHV=4.19 (82FC+ a VM) kJ/kgWhere FC and VM are on dry ash free basis and a is an empirical constant which depends on the VM content of coal.

VM 5 10 15 20 25 30 35 38 40

a 145 130 117 109 103 98 94 85 80

8090

100110120130140150160170

0 10 20 30 40

2. Calculated from ultimate analysis

HEATING VALUE

DULONG FORMULAHV=338.2C+1442.8(H-O/8)+94.2S kJ/kgWhere C, H, O and S are the % of these elements on dry ash free basis.

3. Experimental determination: Bomb calorimeter

HEATING VALUE

IS:1350-II (1970)

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

available

BOMB OF CALORIEMETER

VARIOUS COMPONENTS OF BOMB CALORIMETERIC EQUIPMENT

ROUTES OF GENERATION OF HEAT AND POWER FROM COAL

1. Direct use as thermal energy in heating processes, furnaces and domestic heating by open fires

2. 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 turbines

3. Gas turbine route to electricity generation

4. 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)

Generation of steam in a boiler Space heating by transferring heat of steam to air Process industry : Cogeneration is employed Utility services : steam turbines used

ROUTE II (Thermal Fluid)

GOVERNMENT ALLOWED ELECTRICITY GENERATION BY PRIVATE DEVELOPERSTariffingWheelingBanking

SUPERCRITICAL 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 ≈ 0.53

ROUTE II contd..

Coal

Hot air for spaceheating

Con

dens

ate

Steam

Alternator

Electricity to grid

Con

dens

ate

Steam

Air

to grid

Cogeneration

AlternatorSteam turbine

Heat exchanger

Boiler

Steam

Steamturbine

Steam

Process plant

Electricity

ROUTE III

Electricityto grid

Preheated air

Air

Turb

ine

exha

ust

CompressorGas turbine Alternator

Vent

Heat exchanger

Pulverizer

Coal

Combustion chamber

ROUTE III

Electricityto grid

Preheated air

Air

Turb

ine

exha

ust

CompressorGas turbine Alternator

Vent

Heat exchanger

Combustion chamber

Gasifier and gas cleaning unit

Coal

ROUTE IV (Pyrolysis / Gasification)

1. Partial Gasification or Pyrolysis /coking /carbonization / destructive distillation(heating in the absence of air)• Solid

• Liquid

• Gas

2. Complete gasification with air/oxygen• Gas

PYROLYSIS

Coke (solid fuel) maximum; classical domestic smokeless fuel production

Liquid fraction for chemicals recovery/liquid fuel

Coke for metallurgical furnaces; gas yield high; liquid low

Low temperature carbonization 500-700 oC

High temperature carbonization >900 oC

Medium temperature carbonization 700-900 oC

PYROLYSIS

Pyrolyser

Coal

Water in

Water out

Condenser

Gasfor IC engines/Gas turbines/thermal applications

Coke

Gas for heating of pyrolyser

Flue gas

Pretreatment unit

Liquid fraction

Coal tarLiquid fuelsChemicals

GASIFICATION

33

12x3=36 kg1k mole=1000.R.T/P (m3)=22.41 Nm3

≈18 Liter

(Air Separation Unit)

ROUTE IV BERGIUS PROCESS

1. Bergius processFriedrich 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 oils

2. Fischer-Tropsch processFranz Fischer and Hans Tropsch in 1926, Germany

Coal is hydrogen starved/hydrogen needs to be added to make it liquid (directly or indirectly)

BERGIUS PROCESS

Pulverizer

Coal pasting unit

HydrogenCoal

Fractionating column

BergiusReactor

Heavy fraction

HCs

T=400-500 oCP= 20 -70 MPa Catalyst=TinConver.=97%

F-T PROCESS

Gasification unit

Syn gasCleaning

Coal

Fractionating column

F-T Reactor

HCs

T=150-250 oCP= 1 -25 MpaCatalysts : Fe, Co

Syn gas

(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 similarprojects

F-T PROCESS (COMMERCIAL PLANTS)

F-T PROCESS(COMMERCIAL PLANTS)

UNDERGROUND/ IN SITU COAL GASIFICATION

A process applied to the non-mined coal seams

Injection and production wells are drilled

End gas mix depends on type of coal seam

Air/ oxygen can be used for gasification

Syn gas can be used for power generation in combined cycle

Syn 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

Carbon Dioxide Emissions and Carbon Dioxide Concentrations (1751-2004)

Present CO2 level:483 PPM

COAL COMBUSTION AND ENVIORNMENT

Global Carbon Cycle (Billion Metric Tons Carbon)

COAL COMBUSTION AND ENVIORNMENT

U.S. Anthropogenic Greenhouse Gas Emissions by Gas, 2006 (Million Metric Tons of Carbon Dioxide Equivalent)

ULTIMATE SOLUTIONS

Fuel cells: Chemical to electrical conversion

Solar: photovoltaic

Hybrid vehicles: Honda introduced in India