modeling of fossil fuel formation p m v subbarao professor mechanical engineering department study...
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Modeling of Fossil Fuel Formation
P M V SubbaraoProfessor
Mechanical Engineering Department
Study of Natural Resources for Better Design….
Plant Debris Peat Lignite Brown Coal
Diamond
Semi AnthraciteAnthracite Bituminous
Sub-Bituminous
Formation of Coal
Lignin Structure of Peat
OnHzCOyCHOHCOHxC 22451085106
Structure of smallest molecule: 5108 OHCBio-chemical Reaction:
Atmospheric CO2 Concentration at Peat Bogs
First Law Analysis of Formation of Peat :SSSF
Species Conservation Equation:
First Laws for furnace in SSSF Mode:
CV
COCH
peatveg
CV
WgzV
hmgzV
hm
gzV
hmgzV
hmQ
2
2
4
2
22
22
22
Conservation of Mass:
W
m CO2
m vegetation
Q
Q
m Peat
m CH4
024
COCHpeat mmmm vegetation
OHCOCHOHCOHC 22451085106 222
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.
Secondary Transformation : Geo-Chemical Stage
Chemical Structure of Coal
Coal Ranking
Modeling of Coalification
Peat to Enriched peat: (mostly due to heating)
OHOOHCOHC 22318195108 2324819
OpHzOOHyCOHxC 224163531819
Enriched peat to lignite: (mostly due to pressure &heating)
lignite to Sub-bituminous: (mostly due to pressure &heating)
OpHzOOHyCOHxC 224194941635
Sub-bituminous to High volatile Bituminous:
OpHzOOHyCOHxC 223235741949
High Volatile Bituminous to Medium volatile Bituminous:
4221236432357 qCHOpHzOOHyCOHxC
Medium Volatile Bituminous to Low volatile Bituminous:
4225.0216612364 qCHOpHzOOHyCOHxC
Low Volatile Bituminous to semi Anthracite:
4225.016675.02166 qCHOpHzOOHyCOHxC
Semi Anthracite to Anthracite:
42225.011725.01667 qCHOpHzOOHyCOHxC
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.
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.