Fuels and Combustion
Higher efficiency in the combustion of solid fuel can not be achieved by

Proper fuel preparation
Supplying correct quantity of combustion air
Adopting efficient-fuel firing technique & equipment
Keeping the flue gas exhaust temperature very high

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Fuels and Combustion
A coal with high ash content is undesirable, as

The ash retains the sulphur & phosphorus and thus affects the quality of products in metallurgical furnace apart from increasing the slag volume. Besides, it may fuse and stick to the boiler tubes
All of these
It is abrasive to the coal pulveriser (ie.g. ball mill) and the combustion chamber
The ash in molten condition gets absorbed in the pores of the refractory lining of the furnace and causes its spalling due to different co-efficient of expansion/contraction of the refractory and the

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