Question

Explain the determination of % moisture and % volatile matter in a coal sample.

Answer 1

% Moisture:

• A known weight of powdered and air dried coal sample is taken in a crucible and it is placed in preheated oven for 1 hour at 110 C. Then the coal is cooled in a dessicator and weighed out.
• If the initial weight of the coal is m gms and final weight is m1 gms.
• Then the loss in weight corresponds to moisture in coal.
• Moisture % = `"loss in weight"/"weight of coal sample"xx100=(m-m1)/mxx100` 

% Volatile Matter:

• Moisture free coal left in the crucible in the first experiment is covered with a lid loosely. Then it is heated at 925 C in a furnace for 7 minutes.
• The crucible is taken out and cooled in a dessicator. Then it is weighed again. The loss in weight is due to loss of volatile matter in the m gms of the coal sample.
• % volatile matter = `"weight of volatile matter"/"weight of are dried coal"xx100=(m1-m2)/mxx100`
• The volatile matter % can also be determined by taking the fresh weight of the air dried coal but the loss in weight at 925 C, will be due to loss of moisture and volatile matter both.
• If w is he weight of air dried coal and w2 is the mass of coal left at 925 C heating then,
• % Volatile Matter = `"loss in weight due to moisture and V.M."/"weight of coal sample"xx100`