Fuels and Combustion
In low temperature carbonisation (as compared to high temperature carbonisation) of coal

Aliphatic tar is produced
Ammonia yield is more
Free carbon in tar is more
All of these

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Fuels and Combustion
Fixed carbon in coal is defined as

The total quantity of carbon present in the coal
The one which is present in the residue after combustion
Hundred minus the percentage of volatile matter, ash and moisture
That present in volatile matters

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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
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
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

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