Coal, also referred to as Black Gold, is a raw material and fuel that is globally available across countries and continents. Coal originated in a process of carbonization of plant remains under pressure and lack of oxygen. The main constituents of coal are carbon, hydrogen and oxygen. Coal produces thermal energy during combustion.
Stages of Carbonization
Source: Dr. Lars Schernikau “Economics of the International Coal Trade. The Renaissance of Steam Coal”, Springer, 2010.
The energy intensity of coal depends on the level of its carbonization: anthracite has the highest calorific value, followed by various sorts of hard coals and then lignite. The hard coals that we use today started carbonization some 300 million years ago. By the way, if we let biomass or even coal “carbonate” for another 1-3 billion years they will eventually turn into diamonds. On the lowest rank of the coal hierarchy is peat, characterized by high moisture and low calorific value. The borderline between different grades of coal is rather blurred and characterized by many national coal classification systems. Finally, a refined form of industrially processed coal is coke, which is used for the production of steel.
The Following Parameters are most Important for Coal Classification:
- Net Calorific Value (NCV) and Gross Calorific Value (GCV)
- Moisture (Total TM or Inherent IM)
- Ash (A) und Ash Fusibility (AFT)
- Volatiles (V)
- Sulphur (S)
- Fixed Carbon (C)
- Minerals (e.g. Chlorine, Fluorine)
- Other parameters, such as granulation size, grindability (HGI), coking ability (FSI).
Detailed Coal Classification
Source: European Association for Coal and Lignite (Eurocoal)
Thermal energy is released during combustion of coal. The following tables help to get an overview of different energy units and their conversion.
Energy Units: Definitions
Source: Dr. Lars Schernikau “Economics of the International Coal Trade. The Renaissance of Steam Coal”, Springer, 2010.
Conversion of Energy Units
Source: Dr. Lars Schernikau “Economics of the International Coal Trade. The Renaissance of Steam Coal”, Springer, 2010.
Further links:
http://www.unit-conversion.info/energy.html