Carbon and Fossil Fuels

Coal gas, gaseous mixture—mainly hydrogen ($H _2$), methane ($CH _4$), and carbon monoxide  ($CO$) — formed by the destructive distillation (i.e., heating in the absence of air) of bituminous coal and used as a fuel. Sometimes steam is added to react with the hot coke, thus increasing the yield of gas. Coal tar and coke are obtained as by-products.

A solid fuel formed by heating coal in the absence of air is coke. Coke is black colored, tough porous substance. It is pure carbon. It has applications in steel manufacture and in the metallurgy.

Coke is a better fuel because coke  produces more heat on burning as compared to coal. Coke has higher calorific value than coal. When equal masses of coke and coal are bunt, coke produces more heat. Also when coke is burnt, smoke is not obtained whereas coal produces smoke on coal.

Coke is used in the preparation of producer gas which is a mixture of carbon monoxide and nitrogen. Producer gas is produced by passing air over red-hot coke. Coke is also used to manufacture water gas.

Coal gas is a flammable gaseous fuel made from coal and supplied to the user via a piped distribution system. Town gas is a more general term referring to manufactured gaseous fuels produced for sale to consumers and municipalities.

Natural coke is also called as carbonite coke. It is formed by metamorphism from bituminous coal when intrusive igneous rock cuts across vein of coal.

Coal tar is a brown or black liquid of extremely high viscosity. Coal tar is among the by-products when coal is carbonized to make coke or gasified to make coal gas.

Fixed carbon is the fuel portion of the coke. The higher the fixed carbon, the higher is the thermal value of coke.

Calcinated petcoke (CPC) has highest carbon purity and is used to manufacture aluminium, graphite electrodes, steel, titanium dioxide and other carbon consuming industries.

Foundry coke is a type of hard coke which is used for the production of cast iron and ductile products. It is an excellent source of heat and therefore it is used in industrial boilers and furnaces.

Coke and coal tar are produced as by-product in production of coal gas.

Coal tar, a principal liquid product resulting from the carbonization of coal, i.e., the heating of coal in the absence of air, at higher temperatures.

Coal gas can be made by two processes: carbonization or gasification. Carbonization refers to the devolatilization of an organic feedstock to yield gas and char. Gasification is the process of subjecting a feedstock to chemical reactions that produce gas.

Tar bases are the alkaline constituents of distillate oils, remaining after tar acids have been removed. One of the base that is recovered is pyridine, a colourless nitrogenous liquid that has a pungent odour and produces derivatives that are of pharmaceutical value. Pitch is the material remaining after the removal of pyridine and other distillates. It is useful in the aluminium industry for the manufacture of electrodes.

Coal gas is a flammable gaseous fuel made from coal and supplied to the user via a piped distribution system. Town gas is a more general term referring to manufactured gaseous fuels produced for sale to consumers and municipalities.
Coal gas contains a variety of calorific gases including hydrogen, carbon monoxide, methane and volatile hydrocarbons together with small quantities of non-calorific gases such as carbon dioxide and nitrogen.