COAL


  I have learned about some question related to coal.

coal

       1- what is coal?                   
       2- types of coal?                         
        3- formation of coal?                                   
       4-  the occurrence of coal?     
       5- use of coal?



 what is coal?



Coal is a hard rock which can be burned as a solid fossil fuel.
  • Also called black gold.
 It is a sedimentary rock formed from peat, by the pressure of rocks laid down later on top. It is mostly carbon but also contains hydrogen, sulfur, oxygen, and nitrogen.

                                                 coal is one of the principal mineral fuels.as defined by Stutzer and Noe coal is a combustible rock which had its origin in the accumulation and partial decomposition of vegetation. palaeobotanists have shown conclusively that been formed usually from land plants.








Coal is an organic sedimentary rock that forms from the accumulation and preservation of plant materials, usually in a swamp environment. Coal is a combustible rock and, along with oil and natural gas, it is one of the three most important fossil fuels. Coal has a wide range of uses; the most important use is for the generation of electricity.
type of coal --  there is mainly 4  type coal. This division is based on carbon, ash and moisture content.
  1. Peat, 
  2. Lignite,
  3.  Bituminous
  4.   Anthracite   
 Peat- Peat is not considered as coal though it is a fuel. It represents the first stage of the coal formation. Peat is a brown porous mass of partly decomposed vegetable material. It contains about 85% moisture, 10.4% volatile matter, and 4.6% carbon. The dried peat burns readily with the long smoky flame. Its calorific value is very low.

peat coal

Lignite  ---   Lignite is often called “brown coal” because it is lighter in color than the higher ranks of coal. It has the lowest carbon content out of all the coal ranks (25%-35%)1 and it has high moisture content and crumbly texture. It is mainly used in electricity generation.


lignite coal


Bituminous Coal- It is dense coal of black color. It shows banded structure in which dull and bright bands alternate. The bituminous coal breaks parallel to bands but the presence of vertical joints makes it give cubical or rectangular blocks. Its moisture content is low, volatile matter medium and fixed carbon high. It burns easily with a smoky yellow flame. Its calorific value ranges between 13500 to 16000 B.T.U. higher ranks of bituminous coals have the maximum heating power of all coals

 .
bituminous coal



Anthracite- It is hard coal with an iron-black color and submetallic luster. It does not soil the fingers and commonly breaks with a conchoidal fracture. the anthracite contains about 92-94% carbon and 3-8% volatile matter. It is difficult to ignite but burns with a short blue flame and gives little smoke. its calorific value ranges between 15000 to 15600 B.T.U.



Anthracite coal 



Cannel coal- cannel coal is a special variety of bituminous coal which is very fine grained and is of uniform texture.it has no bituminous coal which is very fine grained and is of uniform texture. It has no banded structure like ordinary bituminous coal. Cannel coal is black in color and has a dull luster. It does not soil fingers. It burns easily with a long candle-like flame.it is made up of windblown spores and pollen. It is commonly found associated with seams of bituminous coal as lenticles or bands up to about half meter think. Cannel coal is essentially a drift deposit laid down in shallow lakes. 

Formation of coal --

                     Amount of oxygen, nitrogen and moisture content decreases with time while the proportion of carbon increases [The quantity of carbon doesn’t increase, only its proportion increases due to the loss of other elements].

The capacity of coal to give energy depends upon the percentage of carbon content [Older the coal, much more is its carbon content].




Percentage of carbon in coal depends upon the duration and intensity of heat and pressure on wood. [carbon content also depends on depth of formation. More depth == more pressure and heat == better carbon content].
  • Coal formed millions of years ago when the earth was covered with huge swampy [marshy] forests where plants – giant ferns and mosses – grew.
  • As the plants grew, some died and fell into the swamp waters. New plants grew up to take their places and when these died still more grew.
  • In time, there was thick layer of dead plants rotting in the swamp. The surface of the earth changed and water and dirt washed in, stopping the decaying process.
  • More plants grew up, but they too died and fell, forming separate layers. After millions of years many layers had formed, one on top of the other.
  • The weight of the top layers and the water and dirt packed down the lower layers of plant matter.
  • Heat and pressure produced chemical and physical changes in the plant layers which forced out oxygen and left rich carbon deposits. In time, material that had been plants became coal.
  • Coals are classified into three main ranks, or types: lignite, bituminous coal, and anthracite.
  • These classifications are based on the amount of carbon, oxygen, and hydrogen present in the coal.
  • Coals other constituents include hydrogen, oxygen, nitrogen, ash, and sulfur.
  • Some of the undesirable chemical constituents include chlorine and sodium.
  • In the process of transformation (coalification), peat is altered to lignite, lignite is altered to sub-bituminous, sub-bituminous coal is altered to bituminous coal, and bituminous coal is altered to anthracite.