What are Fossil Fuels | Types of Fuel

Fossil Fuels:

Fossil fuels are solids, liquids, and gases. Relative low price of natural gas is desirable for use as compared to other fuels like residual oil and coal which highly contaminate the atmosphere. Now efforts are being made to discover methods for the better utilization of coal as a fuel so the pollution due to the burning of coal can be minimized. The desire to reduce sulphur oxides in the air has led to regulations reducing the use of high sulphur residual oils and eastern coals; however.

Types of Fuels:

As mentioned before, fossil fuels are of three states that is solids, liquids, and gases. Let us discuss these fuels one by one briefly.

Solid Fuels:

Some Solid fuels are following:

1. Peat:

Peat is a wet partially decomposed organic matter. It is not a good fuel because of energy per unit weight is not so good. Peat has an extensive horticultural use. Peat is mostly found in isolated areas and drying conditions are severe.

2. Lignite:

Lignite is a solid fuel whose composition lies between the composition of peat and coal. It is also not a good fuel and not extensively used but it is used in the commercial barbeque briquette process. Some lignite also contains a significant amount of uranium in it.

3. Coal:

Coal is the most used solid fuel. Reserves of coal are found in great quantity but this coal cannot be used for domestic purposes. The reason is that this coal contains a good quantity of sulphur which upon burning produces sulphur oxides and causes pollution. So before using it for commercial purposes, it is needed to be treated. Coal cannot be used for electrical utilities and domestic purposes on a large scale. As you know, fuels consumption is increasing day by day and reserves of coal are in great quantity. So, Chemical Engineers are practising to fulfil the shortage of fuels faced annually by conversion of coal through commercial gasification/liquefaction. These projects are extremely large, requiring the creation, gigantic expenses not less than the present petroleum industry. Coal is classified according to their fuel properties, as anthracite, bituminous, subbituminous, and lignite with the subdivision of each type. Anthracite is the best coal type due to its clean burning characteristics and lowest pollutant production but it is now largely exhausted. Bituminous Coal is principally used for the burning to gain energy and carbonization of coke, tar, coal chemicals, and coke-oven gas. Gasified coal, as methane, low heating value gas, or high heating value gas, shows much promise as a fuel of the future and is essentially nonpolluting.

Pulverized coal has been increasingly used during recent years in suspension firing for power plant installations because of the high thermal efficiency with which it can be burned the low cost of operation and maintenance and its great flexibility.

4. Coke:

Coke is a fine solid fuel but it cannot be used commercially because of its expensive feature, although it is suitable to be used in blast furnace operation because in this process it acts as fuel as well as a chemical reactant.

Other solid fuels such as coke breeze, wood, sawdust, bagasse, and tanbark are used where they are easily available and obtained as a by-product.

Liquid Fuels:

Liquid Fuels are mostly obtained from the refining of crude oil. Some of the liquid fuels are the following.

1. Fuel Oil:

The only important liquid fuel used for power generation is fuel oil. It is obtained as a fraction of crude oil that cannot be converted into high priced product upon refining. It consists of a mixture of the liquid residues from cracking processes and fraction with suitable boiling point obtained by distillation of crude oil. Fuel Oils are classified by their properties, e.g. flash point, pour point, the percentage of water and sediment, carbon residue, ash, distillation temperatures, and viscosity.

2. Other Liquid Fuels: 

Some of the other liquid fuels are tar, tar oil, kerosene, benzol, and alcohol but these products are used in very smaller extent. Gasoline is mainly used in internal combustion engines.

Gaseous Fuels:

1. Natural and Manufactured Gas:

Natural and Manufactured gas is burned as a source of heat in domestic installations and also in industry. Blast Furnace gas resulting from the smelting of iron is an outstanding example of a by-product gas employed for heating the blast stoves, with the remainder burned under the boilers or for heating coke ovens.