Qualities of Fuels Used in Steam (Coal) Thermal Power Plants
- Following are the types of fuels which can be used for thermal plant: (i) Solid, (ii) Liquids, (iii) Gaseous.
- They may be natural or prepared. Normally for a thermal power station coal, oil or gas is used as fuel. Gaseous fuel is only economical when its source is nearby the plant.
- In country like India, where there is a shortage of oil and is required to import, it is not economical, however it will be economical to use oil as a fuel if it is available in ample quantity and cheaply.
- In India coal is the fuel which is commonly used in a thermal power plant.
- Coal occurs naturally in mines as mined raw coal usually contains impurities such as pieces of slate etc. Hence, it is required to carry out some amount of processing at the colliery before it can be transported.
Analysis of Coal
- To determine the commercial value of coal following tests are carried out:
(i) Proximate analysis: It gives indication about heating and burning properties of coal. It gives the composition of coal in respect of moisture, volatile matter, ash and fixed carbon.
(ii) Ultimate analysis: It is a test, which enables to know the chemical composition of coal w.r.t. elements like carbon, hydrogen, oxygen, Sulphur, nitrogen and ash. Since, the content of carbon and hydrogen that is already combined with oxygen to form carbon dioxide and water is of no value for combustion. The chemical analysis of the coal alone is not sufficient to predict the suitability of coal for the purpose of heating. However, the chemical composition is very useful in combustion calculations and in finding the composition of flue gases. For most of the purposes, proximate analysis is quite sufficient.
- Coals are classified in increasing order of heat value into the following: Peat, lignite, bituminous, semi-bituminous, semi-anthracite and anthracite. Anthracite is the fully transformed coal of the best type while peat is the first stage of transformation.