Question

A power plant burns 100 metric tons of coal per day with a sulfur content of 5%. The coal contains 3% ash (noncombustible portion). Samples of the ash show that it has a sulfur content of 10% sulfur by weight. Sulfur that is not in the ash is in the flue gases. How many metric tons of SO2 are emitted from the smoke stack each day? (Hint: Apply mass balance to find the amount of sulfur leaving the power plant and then use stoichiometry to calculate SO2) Answer: 9.4 ton SO2/d

Answer 1

1 ton = 0.907185 metric tons

100 ton = 90.72 metric ton

100 metric ton = (1*100)/0.9072 = 110.23 ton

5 % S is present in coal.

That is 5 metric ton S in 100 metric ton coal.

3 % is ash = 3 metric ton

10 % of 3 metric ton = (3*10)/100 = 0.3 metric ton

Thus 0.3 metric ton S is present in ash.

So combustible quantity of S in 100 metric ton coal = (5 -0.3)=

4.7 metric ton

1 kilogram is equal to 0.001 metric ton.

That is 1000 Kg = 1 metric ton

4.7 metric ton S = 4700 Kg

S molecular weight = 32.10 g

The stoichiometric equation for SO2 formation is

S + O2 ----------> SO2

That is 32 g S reacts with 32 g of O2 to give 64 g SO2.

Thus 4.7 metric ton S reacts with 4.7 metric ton of O2 to give 9.4 metric ton SO2.

Thus SO2 formed per day = 9.4 metric ton /day.