Questions & Answers on Coal analysis & related calculations

 

1-What are the various coal analysis are carried out in plant lab?

• Surface moisture
• Inherent moisture
• Total moisture
• Volatile matter
• Ash
• Fixed carbon
• Unburned carbon
• Moisture in ash
• GCV by Bomb calorimeter & by calculation
• Sieve analysis

2-How do you calculate the surface moisture (SM) of coal?

Take 100 gram of coal sample whose size is < 12.5 mm & keep this sample in lab for 24 hours at atmospheric condition.

Then calculate the surface moisture = Loss in weight X 100 / Weight of the sample (100 gram)

For example: After drying the 100 gram coal in lab for 24 hours its total becomes 92 gram then,

Surface moisture = (100-92) X 100 / 100 = 8%

3- How do you calculate the Inherent moisture (IM) of coal?

After analysis of surface moisture, take 5 gram of coal sample & powder it to 212 microns or 0.212 mm & keep it in oven at temperature 108 deg C for 1 Hr

Sample is then cooled & is weighed & IM is calculated as

Inherent Moisture = = Loss in weight X 100 / Weight of the sample (5 gram)

4-What do you mean by Total moisture (TM) of coal? & how do you calculate the Total Moisture of coal?

Coal containing free visible & non visible water is called total moisture of coal. The total moisture of coal is due to rain or coal in contact with water.

TM is calculation:

Take 100 gram of coal sample of size < 12.5mm & keep it in oven for 1 hour at 108 deg C

Sample is then cooled & is weighed & TM is calculated as

Total Moisture = Loss in weight X 100 / Weight of the sample (100 gram)

Total moisture is the sum of IM & SM

5-How do you calculate Volatile matter present in coal?

Take 2 gram of moisture free coal sample & keep it in muffle furnace for 7 minutes at 900 deg C temperature. Then cool it in desiccator for 15 minutes. Then sample is again weighed for final weight.

Volatile matter = Loss in weight X 100 / Weight of the sample (2 gram)

6-How do you calculate the percentage of ash present in coal?

Take 1 gram of coal sample & keep it in muffle furnace for 1 Hr at 900 deg C temperature. Then cool it in desiccator for 15 minutes. Then sample is again weighed for final weight.

Ash % = Residual weight X 100 / Total weight of the sample (1 gram)

7-Write down the formula for calculating Fixed Carbon (FC)

Fixed carbon FC = 100-(TM+VM+Ash)

8-How do you calculate the unburned carbon in ash sample?

Take 1 gram of ash sample & burn it in muffle furnace for 1 hr at temperature 900 deg c. Then cool it in desiccator for 15 minutes. Then sample is again weighed for final weight.

% of unburned carbon = Loss in weight X 100 / Weight of the sample (1 gram)

9-How do you convert GCV of coal from Air dried basis (ADB) to As received basis (ARB) & Vice versa?

GCV ADB to ARB =GCVADB X (100-TM) / (100-IM)

GCV ARB to ADB =GCVARB X (100-IM) / (100-TM)

10-How do you convert coal GCV from ADB to Dried basis?

ADB to DB = GCVADB X 100 / (100-IM)

11-What are the two different types of coal analysis?

Proximate Analysis & Ultimate analysis

12-What parameters of coal are analysed in proximate analysis of coal?

Moisture, Volatile matter, Ash & Fixed carbon

13- What parameters of coal are analysed in Ultimate analysis of coal?

Total Carbon, Hydrogen, Nitrogen, Oxygen & Sulphur

14-How do you convert Higher Calorific value of coal into Lower calorific Value coal?

LCV = HCV - (9 X H2 X 586)

15-A coal sample of HCV 5100 kcal/kg having 3.5% of hydrogen in it, then calculate the LCV

LCV = HCV - (9 X H2 X 586) = 5100 – (9 X 3.5% X 586) = 4915.41 kcal/kg

16-A coal sample of GCV 4800 kcal/kg having total moisture 18%, then calculate the Net calorific value (NCV) of coal

NCV = GCV-(10.02 X Moisture) = 4800 – (10.02 X 18) = 4619.64 kcal/kg

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