A sample of finely grounded coal of mass 0.9946kg was placed in a crucible of 8.

Question

A sample of finely grounded coal of mass 0.9946kg was placed in a crucible of 8.5506g in an oven,maintained at 375 k for 400 seconds .The sample was then removed,cooled in a dissicator and re- weighed,the procedure being repeated until a constant total mass of 9.5340g was attained. A second sample, of mass 1.0120g in a crucible of mass 8.5685g was heated with a lid over a Bunsen for 450 seconds.On cooling and reweighing, the total mass was 9.1921g.The sample was then heated without a lid over a strong Bunsen flame until a constant total mass of 8.6255g was attained. Calculate the proximate analysis of the sample and express the results on as sample and dry ash free bases.

Explanation / Answer

1) Moisture : The moisture is evaporated during the heating so that the difference between the starting weight and the final weight represents the moisture. One gram of coal is heated to 105 degrees C. When the weight stops changing, the sample weight remaining is 0.95 grams.

2) Ash : everything except the ash is burned so that the final weight is the ash.The same sample from test one is burned in air to a final weight of 0.12 grams

3) Volatile Matter: The volatile matter is evaporated during the heating so that the difference between the starting weight and the final weight represents the volatile matter. An additional one-gram sample of the same coal is heated for seven minutes in the absence of air.The weight at the end of the test is 0.65 grams.

4) The fixed carbon :It represents the carbon content in a coal that has not combined with any other element (in a free state). The amount of fixed carbon increases with the rank of coal and is highest in Antracite coal. The amount of fixed carbon is computed by subtracting the sum of the percentage of moisture, volatile matter and ash from hundred. Fixed carbon = 100 - (moisture% + ash% + volatile matter%)

1.00 gram - 0.65 grams = 0.35 grams or 35 percent volatile matter weight.

Calculate the proximate analysis of this sample.

Moisture=5%

Ash=12%

Volatile Matter=35%

Fixed Carbon=48%

Total=100%

This is the procedure for the first sample and likewise the second sample is to be calculated.

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