Carbon and Fossil Fuels

The substance that burns in the presence of oxygen and heat are called combustible substances whereas that do not burn are non-combustible substances. Elements such as carbon, hydrogen and sulphur present in the fuel makes it combustible.

The ash content of indian coal is 30℅. Initially in 1970s it was 28℅. The quality of Indian coal is deteriorating over the years. However Sulphur content of Indian coal is low about 0.5℅.

Coal is a black coloured sedimentary rock. When coal is grounded or broken into fine particles using a device called powdered coal mill, the resultant coal obtained is called powdered coal or pulverized coal. It is used in cosmetics, for the generation of electricity etc.

The calorific value of the coal depends upon its ash content. Less the ash content present, more is the calorific value of the fuel i.e. the fuel which has less ash content produces more energy on burning. Higher the calorific value, more is the efficiency of the fuel.

Bituminous coal or black coal is a relatively soft coal containing a tarlike substance called bitumen or asphalt. It is of higher quality than lignite coal but of poorer quality than anthracite and has a high heating (Btu) value . Formation is usually the result of high pressure being exerted on lignite. Bituminous coal is an organic sedimentary rock formed by diagenetic and sub metamorphic compression of peat bog material. Its primary constituents are macerals: vitrinite, and liptinite. The carbon content of bituminous coal is around 60–80%; the rest is composed of water, air, hydrogen, and sulfur.

Lignite is brownish-black in color and has a carbon content around 60–70 percent, a high inherent moisture content sometimes as high as 75 percent, and an ash content ranging from 6–19 percent compared with 6–12 percent for bituminous coal. The energy content of lignite ranges from 10 to 20 MJ/kg (9–17 million BTU per short ton) on a moist, mineral-matter-free basis.

Lignite is brownish-black in color and has a carbon content around 60–70 percent, a high inherent moisture content sometimes as high as 75 percent, and an ash content ranging from 6–19 percent compared with 6–12 percent for bituminous coal.

 A brownish-black coal with generally high moisture and ash content, and the lowest carbon content and heating value is lignite.

The process of conversion of lignite to anthracite is called coalification or metamorphism of coal.
Coal is classified on the basis of its rank. The rank of coal denotes its degree of maturity. Vegetable matter, under the action of pressure, heat and anaerobic conditions, gets converted into different stages of coal namely:
Wood → Peat → lignite → sub-bituminous coal → bituminous coal → anthracite.
Peat is the first stage in the formation of coal.

The calorific value of the fuel is also called as the heat value of the fuel. It is defined as the amount of heat released by burning of unit quantity of the fuel. The calorific value is an important characteristic of the fuel. The unit of measurement of the calorific value is the same as the energy.

The rank of coal is based on the degree to which the original plant material has been transformed into carbon.

The rank of coal is based on the amount of the plant converted into carbon.

The mineral coal with given properties is Anthracite.

Dry cleaning means cleaning of tiles without using water or aqueous solvents. Petrol is used as a solvent in dry cleaning because it is highly vapourising organic solvent.