Ultimate Analysis

Ultimate analysis refers to elemental analysis of coal.The main chemical elements in coal (apart from associated mineral matter) are C, O, H, N and S. The chemical analysis is very important to calculate material balance accurately and calorific value of coal. For the ultimate analysis C, H, S and N are determined by chemical analysis and expressed on a moisture free basis. Ash is determined as in proximate analysis and is calculated on moisture free basis. Then,

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Ultimate analysis is useful to perform combustion calculations for energy balance in the furnace. It is also required to calculate the calorific value of coal. Ultimate analysis also suggests the combustible and non-combustible elements in thew coal. For example carbon, hydrogen and sulphur are combustible, whereas nitrogen, oxygen, ash and moisture are non-combustibles.

Note on Ash and Volatile Matter

In fact coal contains mineral matter (MM) like , , , , etc. but not ash. Ash is residue obtained after complete combustion of coal and consists of , , , etc. Ash and mineral matter are not identical.

Ash content of coal is important. In high temperature applications where coal is the principle source of chemical and thermal energy, removal of ash is an important issue. In general ash content of coal should be low. In addition, melting point of ash is also important. In furnaces where coal is used to heat the material below its melting point, melting point of ash should preferably be higher than the furnace temperature because of easy disposal

Whereas in applications where coal is carbonized and the carbonized product is used to derive thermal and chemical energy for example in blast furnace iron-making, both amount of ash and its melting point is of considerable importance. In this case ash should be easily fusible and its melting point should be lower than furnace temperature. Larger amount of ash will increase the amount of slag.

Total mineral matter (MM) can be calculated by Parr formula¹⁾

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While calculating FC on mineral matter basis, Parr subtracts 0.15% S from measured fixed carbon.