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

Plant Debris PeatLignite Brown Coal Diamond Semi AnthraciteAnthraciteBituminous Sub-Bituminous Formation of Coal

Lignin Structure of Peat Structure of smallest molecule: Bio-chemical Reaction:

Atmospheric CO 2 Concentration at Peat Bogs

First Law Analysis of Formation of Peat :SSSF Species Conservation Equation: First Laws for furnace in SSSF Mode: Conservation of Mass: W m CO2 m vegetation Q Q m Peat m CH4

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)

Enriched peat to lignite: (mostly due to pressure &heating)

lignite to Sub-bituminous: (mostly due to pressure &heating)

Sub-bituminous to High volatile Bituminous:

High Volatile Bituminous to Medium volatile Bituminous: Medium Volatile Bituminous to Low volatile Bituminous: Low Volatile Bituminous to semi Anthracite: Semi Anthracite to Anthracite:

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.