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

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.