Coal Formation
Fossil fuels are derived from plant and animal matter. They formed naturally over millions of years. These energy-producing fuels are the remains of ancient life that have undergone changes due to heat and pressure. The primary fossil fuels are coal, petroleum and natural gas. Together they account for 85% of the world's energy consumption.
Coal is a dark, combustible material formed, through a process known as coalification, from plants growing primarily in swamp regions. Layers of fallen plant material accumulated and partially decayed in these wet environments to form a spongy, coarse substance called peat. Over time, this material was compressed under sand and mud, and heated by the earth to be transformed into coal. Some scientists refer to coal as sedimentary rock. Coal is primarily composed of carbon, hydrogen, oxygen and nitrogen.
There are several classifications of coal, which are rated according to their carbon content and heating value. The heating value of coal is expressed in Kcal/Kg.
Coal Mining:
The two main types of coal mining are
1. Surface (strip) mining and 2.underground mining.
a).Strip mining:
It involves the removal of coal deposits close to earth's surface (usually no more than 100 feet from the surface). Topsoil and rocks are removed from the surface to expose the coal deposits. Explosives and heavy machinery are used to break up and remove layers of coal.
b).Underground mining
It involves the removal of coal deposits, often hundreds of feet below the earth's surface. (Some mines may be close to 2,000 feet deep.) Shafts or tunnels are dug into the coal layers and widened to allow room for the miners and coal cars or conveyor belts. Additional shafts may be excavated to increase air ventilation for the miners.
Coal Uses
Coal is used to generate heat, produce electricity, and make steel and industrial products. It is used worldwide as a fuel, second only to petroleum as the most consumed energy resource.
Coal Classification
As geological processes apply pressure to dead biotic material over time, under suitable conditions it is transformed successively into
Peat: It is considered to be a precursor of coal, has industrial importance as a fuel in some regions, for example, Ireland and Finland
Lignite: It is also referred to as brown coal, is the lowest rank of coal and used almost exclusively as fuel for electric power generation. Jet is a compact form of lignite that is sometimes polished and has been used as an ornamental stone since the Upper Paleolithic.
Sub-bituminous coal : This coal properties range from those of lignite to those of bituminous coal is used primarily as fuel for steam-electric power generation. Additionally, it is an important source of light aromatic hydrocarbons for the chemical synthesis industry.
Bituminous coal : it’s look like a dense sedimentary rock, black but sometimes dark brown, often with well-defined bands of bright and dull material, used primarily as fuel in steam-electric power generation, with substantial quantities also used for heat and power applications in manufacturing and to make coke.
Steam coal: It is a coal having grade between bituminous coal and anthracite, once widely used as a fuel for steam locomotives. In this specialized use it is sometimes known as sea-coal in the U.S.
Anthracite : it is the highest rank; a harder, glossy, black coal used primarily for residential and commercial space heating.