Coal is an organic mineral which can be burned andformed from ancient plant residual precipitate which subsequently changed its form due to physical and chemical processes that occur over millions of years. Therefore, the coal included in the category of fossil fuels. The process that turns coal plants is called as coalification.
Variety of ancient plant according to geologic age and location of growth and development, along with the site of deposition (sedimentation) of the plants, the influence of pressure and geothermal rocks and geological changes that occurred are the factors why there are various types of coal. Therefore, the characteristics of coal vary with the field of coal (coal fields) and coating (hard coal).
Formation of coal began in the formative period of the Carboniferous (Carboniferous Period), known as coal, which was the first of the season lasted from 360 to 290 million years ago. The quality of each coal deposit is determined by temperature and pressure as well as the establishment of a long time, referred to as "organic maturity." First process, the plants turn into deposits of peat which later changed its brown coal (lignite) or also called lignite (brown coal). Young coal is coal with the kind of low organic maturity.
After obtaining the effects of temperature and continuous pressure over millions of years, lignite will experience changes that gradually increase the organic maturity and youth to change coal into sub-bituminous coal (sub-bituminous). Chemical and physical changes continued until the coal becomes harder and darker color to form bituminous coal (bituminous) or coal (anthracite). Under the right conditions, an increase of more mature organic, continued to form anthracite.
In coalification process, the organic maturity, actually describes the change in concentration of each major element of the coal-forming. The following example shows the analysis of each element in each coalification stage. coalification process at higher levels, carbon levels will increase, while the hydrogen and oxygen is reduced. Because the level of general coalification can be associated with the quality or the quality of coal, coal with low coalification also called low-grade coal, materials such as lignite and sub-bituminous are generally more gentle with the fragile and without color brightness as the ground, have high levels of moisture (humidity) is high and the low carbon content, so the energy content is also low. The higher the quality of coal, generally the hardest color and compact, elegant black and will be more. Also, humidity levels would be reduced, while the carbon will increase, so the greater its energy content.
The Coal is Classified based on the level coalification usually becomes a general indicator to determine the intended use. For example, coal or coal boiler is called thermal or steam coal, used to fuel many power plants, industrial combustion at large, such as brick or tile, and cement industries, while metallurgical coal (coking coal, coke or coal) is used for industrial iron and steel industries and chemicals. Both types of coal were included in the bituminous coal. The anthracite coal used for mineral ore sintering process, the process of manufacture of electrical electrodes, burning lime, and for the manufacture of smokeless briquettes.
Before its used, the coal must be known in advance the quality. This meant that the specifications of the machine or equipment that use coal as fuel, in accordance with the quality of coal being used, so the machines can function optimally and durable.
