Fuels and Combustion
Low temperature oxidation and spontaneous combustion of freshly mined coal is accentuated, if

All of these
It is stored in tall heaps
It contains large amount of volatile matter
Smaller fines are stored in large quantity

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

It is abrasive to the coal pulveriser (ie.g. ball mill) and the combustion chamber
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
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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