2. Chemical Structure of Coal
(Depending upon source, structure may be widely different)
Anthracite Coal
Carbon 92-98%
3. COAL : DEFINITION
Coal is a stored fossil fuel, occurring in
layers in the earth’s crust, which has
been formed by the partial decay of
plant materials accumulated millions of
years ago and further altered by the
action of heat and pressure.
5. 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 found
450-600 m of plant material might have
accumulated at that place.
(Taipei 101:509 m tallest building in world)
7. COAL RANKS
1.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
8. 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 usage
Carbon: 75-90%: Oxygen:10-5%
Semi-bituminous:
Between bituminous and anthracite
Metallurgical coke formation
Carbon: 90-93%; Oxygen:4-1%
9. COAL RANKS contd…
4. Anthracites
Highest rank of coal
Extreme of metamorphosis
from the original plant material
Carbon: 93+%: Oxygen: 2-1%
Caking power zero
Unusual coals
Cannels: 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.
10. 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)
11. WORLD PRODUCTION OF COAL IN YEAR 2006
% of world production
Country Million tonnes
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
12. WORLD PRODUCTION OF COAL IN YEAR 2006
Canada United Pakistan
South
Kingdom
Africa Japan
Australia
India
China
USA
13. WORLD TOP TEN COAL PRODUCING AND
CONSUMING COUNTRIES
1 quadrillion=1000 trillion
1 Btu=1.055 kJ
14. 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 38
Years 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
15. COAL RESOURCES OF STATES
Proved: boreholes (1200m deep) @ 400 m
IN MILLION TONNES Jan 1, 2007
Indicated & Inferred: boreholes @ 1-2 km
State Proved Indicated Inferred Total % of total
Jharkhand 36881 31094 6339 74314 29.11
Orissa 17464 30239 14296 61999 24.29
Chhattisgarh 10182 26826 4443 41451 16.24
West Bengal 11454 11810 5071 28335 11.10
Madhya Pradesh 7584 9259 2934 19777 7.75
Andhra Pradesh 8475 6328 2658 17461 6.84
Maharashtra 4856 2822 1992 9670 3.79
Uttar Pradesh 766 296 0 1062 0.42
Meghalaya 118 41 301 460 0.18
Assam 315 27 34 376 0.15
Bihar 0 0 160 160 0.06
Arunachal Pdesh 31 40 19 90 0.04
Sikkim 0 55 18 73 0.03
Nagaland 3 1 15 19 0.01
Total 98129 118838 38280 255247 100
16. 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
17. 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 coal
Grade UHV, kcal/kg Ash %
A >6200 <13.56
B 5600-6200 13.56-17.91
C 4940-5600 17.91-22.69
D 4200-4940 22.69-28.06
E 3360-4200 28.06-34.14
F 2400-3360 34.14-41.10
G 1300-2400 41.10-49.07
UHV:Useful Heating Value Based on 6 % moisture content
=8900-138×[ash% + moisture%]
18. 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
19. 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
20. ANALYSIS OF COAL
Proximate analysis
Ultimate analysis
Heating/calorific value
21. PROXIMATE ANALYSIS
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)
REPORTING: AS RECEIVED BASIS, MOISTURE FREE
BASIS/DRY BASIS OR DRY ASH FREE BASIS
IS:1350-I (1984)
22. EXAMPLE OF PA
A sample of finely ground coal of mass 0.9945 g was
placed in a crucible of 8.5506 g in an oven, maintained at
105 oC for 4.0 ks. The sample was then removed, cooled in
a dessicator and reweighed; the procedure being repeated
until a constant total mass of 9.5340 g was attained. A
second sample, of mass 1.0120 g in a crucible of mass
8.5685 g was heated with a lid in a furnace at 920 oC for
420 s. On cooling and reweighing, the total mass was
9.1921 g. This sample was then heated without a lid in the
same furnace maintained at 725 oC until a constant total
mass of 8.6255 g was attained. Calculate the proximate
analysis of the sample and express the results on “as
sampled” and “dry, ash-free” basis.
23. 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 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 %
24. 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 %
25. 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 %
26. ULTIMATE ANALYSIS
1. Carbon
2. Hydrogen
3. Oxygen
4. Sulfur :0.5-2.50 %
5. Nitrogen :1.0-2.25 %
6. Phosphorus :0.1%;Blast Furnace: <0.01 %
7. Chlorine
Mercury: A big problem from NTPC plants
(up to 0.3mg/kg)
IS:1350- IV (1974)
27. HEATING VALUE
1. Calculated from proximate analysis
2. Calculated from ultimate analysis
3. Experimental determination
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
28. HEATING VALUE
1. Calculated from proximate analysis
TAYLOR AND PATTERSON RELATIONSHIP
HV=4.19 (82FC+ a VM) kJ/kg
Where FC and VM are on dry ash free basis and a is
an empirical constant which depends on the VM
content of coal. 170
160
150
140
130
120
110
100
90
80
0 10 20 30 40
VM 5 10 15 20 25 30 35 38 40
a 145 130 117 109 103 98 94 85 80
29. HEATING VALUE
2. Calculated from ultimate analysis
DULONG FORMULA
HV=338.2C+1442.8(H-O/8)+94.2S kJ/kg
Where C, H, O and S are the % of these elements on
dry ash free basis.
30. HEATING VALUE
3. 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
available
IS:1350-II (1970)
33. 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)
34. 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)
35. 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 used
SUPERCRITICAL BOILERS: A RECENT CONCEPT
Critical pressure: 218 bar (21.8 MPa); Critical temperature: 374oC
Mark Benson; in 1922 Patent was granted
22 MPa pressure ; η= 1-T1/T2 ≈ 0.53
GOVERNMENT ALLOWED ELECTRICITY GENERATION
BY PRIVATE DEVELOPERS
Tariffing
Wheeling
Banking
36. ROUTE II contd..
Hot air
for
Heat space
Coal Boiler Steam
exchanger heating
Steam
Air
Condensate
Steam
Cogeneration
Steam
turbine Alternator to grid
Alternator
Electricity
Condensate
Steam
Steam
turbine
Electricity to grid Process plant
37. ROUTE III
Coal Vent
Preheated air
Pulverizer Heat
exchanger
Turbine
exhaust
Combustion
chamber
Gas turbine Compressor Alternator
Air Electricity
to grid
38. ROUTE III
Vent
Preheated air
Heat
exchanger
Turbine
exhaust
Combustion
chamber
Gas turbine Compressor Alternator
Coal
Air Electricity
Gasifier and gas to grid
cleaning unit
39. 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
40. PYROLYSIS
Low temperature carbonization 500-700 oC
Coke (solid fuel) maximum; classical domestic smokeless fuel
production
Medium temperature carbonization 700-900 oC
Liquid fraction for chemicals recovery/liquid fuel
High temperature carbonization >900 oC
Coke for metallurgical furnaces; gas yield high; liquid low
41. PYROLYSIS
Coal Pretreatment
unit
Water in Gas
Flue 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
45. ROUTE IV BERGIUS PROCESS
Coal is hydrogen starved/hydrogen needs to be added to make it
liquid (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 oils
2. Fischer-Tropsch process
Franz Fischer and Hans Tropsch in 1926, Germany
46. BERGIUS PROCESS
Coal T=400-500 oC Hydrogen
P= 20 -70 MPa
Catalyst=Tin
Conver.=97% Fractionating
column
Pulverizer
HCs
Bergius
Reactor
Coal pasting
unit
Heavy fraction
47. F-T PROCESS
Coal T=150-250 oC
P= 1 -25 Mpa
Catalysts : Fe, Co
Fractionating
column
Gasification
unit HCs
F-T
Syn gas
Reactor
Syn gas
Cleaning
(Large number of patents worldwide)
48. 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
51. 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
53. 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
54. COAL COMBUSTION AND ENVIORNMENT
Present CO2 level:483 PPM
Carbon Dioxide Emissions and Carbon Dioxide Concentrations (1751-2004)
55. COAL COMBUSTION AND ENVIORNMENT
Global Carbon Cycle (Billion Metric Tons Carbon)
56. COAL COMBUSTION AND ENVIORNMENT
U.S. Anthropogenic Greenhouse Gas Emissions by Gas,
2006 (Million Metric Tons of Carbon Dioxide Equivalent)
