fuel

1. Modeling of Fossil Fuel Formation
P M V Subbarao
Professor
Mechanical Engineering Department
Study of Natural Resources for Better
Design….

2. Plant Debris Peat Lignite Brown Coal
Diamond
Semi Anthracite
Anthracite Bituminous
Sub-Bituminous
Formation of Coal

4. Lignin Structure of Peat
O
nH
zCO
yCH
O
H
C
O
H
xC 2
2
4
5
10
8
5
10
6 



Structure of smallest molecule: 5
10
8 O
H
C
Bio-chemical Reaction:

5. Atmospheric CO2 Concentration at Peat Bogs

6. First Law Analysis of Formation of Peat :SSSF
Species Conservation Equation:
First Laws for furnace in SSSF Mode:
CV
CO
CH
peat
veg
CV
W
gz
V
h
m
gz
V
h
m
gz
V
h
m
gz
V
h
m
Q































































































2
2
4
2
2
2
2
2
2
2
Conservation of Mass:
W
m CO2
m vegetation
Q
Q
m Peat
m CH4
0
2
4 







CO
CH
peat m
m
m
mvegetation
O
H
CO
CH
O
H
C
O
H
C 2
2
4
5
10
8
5
10
6 2
2
2 




7. Secondary Transformation : Geo-Chemical Stage
• The decayed vegetation was subjected to extreme
temperature and crushing pressures.
• It took several hundred million years to transform the
soggy Peat into the solid mineral.
• 20 m of compacted vegetation was required to produce 1 m
seam of coal.
• This is called as coalification or coal forming.
• The extent to which coalification has progressed
determines the rank of coal.

8. Secondary Transformation : Geo-Chemical Stage

9. Chemical Structure of Coal

12. Coal Ranking

13. Modeling of Coalification
Peat to Enriched peat: (mostly due to heating)
O
H
O
O
H
C
O
H
C 2
2
3
18
19
5
10
8 23
24
8
19 



14. O
pH
zO
O
H
yC
O
H
xC 2
2
4
16
35
3
18
19 


Enriched peat to lignite: (mostly due to pressure &heating)

15. lignite to Sub-bituminous: (mostly due to pressure &heating)
O
pH
zO
O
H
yC
O
H
xC 2
2
4
19
49
4
16
35 



16. Sub-bituminous to High volatile Bituminous:
O
pH
zO
O
H
yC
O
H
xC 2
2
3
23
57
4
19
49 



17. High Volatile Bituminous to Medium volatile Bituminous:
4
2
2
1
23
64
3
23
57 qCH
O
pH
zO
O
H
yC
O
H
xC 



Medium Volatile Bituminous to Low volatile Bituminous:
4
2
2
5
.
0
21
66
1
23
64 qCH
O
pH
zO
O
H
yC
O
H
xC 



Low Volatile Bituminous to semi Anthracite:
4
2
2
5
.
0
16
67
5
.
0
21
66 qCH
O
pH
zO
O
H
yC
O
H
xC 



Semi Anthracite to Anthracite:
4
2
2
25
.
0
11
72
5
.
0
16
67 qCH
O
pH
zO
O
H
yC
O
H
xC 




18. Coal Classification
• There are two main ways for classifying coal
- by rank and by type.
• Coal Rank
• Coal Types
• Coal Rank : The degree of 'metamorphisrn'
or coalification undergone by a coal, as it
matures from peat to anthracite, has an
important bearing on its physical and
chemical properties, and is referred to as the
'rank' of the coal.
• Low rank coals, such as lignite and sub-bituminous coals, are typically softer,
friable materials with a dull, earthy appearance; they are characterised by
high moisture levels and a low carbon content, and hence a low energy
content.
• Higher rank coals are typically harder and stronger and often have a black
vitreous lustre.

19. Composition of Coals
• The natural constituents of coal can be divided into two
groups:
• (i) the organic fraction, which can be further subdivided
into microscopically identifiable macerals; and
• (ii) the inorganic fraction, which is commonly identified as
ash subsequent to combustion, but which may be isolated
in the form of mineral matter by low-temperature ashing
(LTA).
• The organic fraction can be further subdivided on the basis
of its rank or maturity.