Question

Give a brief account of proximate analysis of coal .

Answer 1

In this analysis moisture, volatile matter, ash and fixed carbon can be determined. 

Moisture: A known amount of finely powdered air-dried coal sample is taken in crucible. The crucible is placed inside an electric hot air-oven, at \(105^o to 110^oC\) for 1 hour. The crucible is then taken out, cooled in desiccators and weighed. Difference in the weight of sample gives the information about the weight loss due to removal of moisture.

Lesser the amount of moisture content, better the quality of fuel 

 

Volatile matter: The moisture free coal sample is taken in a crucible, covered with a lid and placed in muffle furnace (electric furnace) at 950oC for 7 minutes and then remove the crucible from the oven and cooled first in air, then cooled in a desiccator and weighed again. Loss in weight is due to presence of volatile matter in coal sample

Low quantity of volatile matter, better the quality of a coal.

Ash: The residual coal sample taken in a crucible and then heated without lid in a muffle furnace at 700-750oC for an hour. The crucible is then taken out, cooled first in air, then in desiccators and weighed again. The process of heating, cooling and weighing are repeated until a constant weight is not obtained. The residue is reported as ash on percentage-basis.

Ash is non-combustible substance which reduces the calorific value of a coal. Therefore, low quantity of ash contents, better the quality of a coal.

 

Fixed carbon: The fixed carbon percentage is determined by following equation 

Greater the calorific value, higher the % of fixed carbon.