Page 297 - Air pollution and greenhouse gases from basic concepts to engineering applications for air emission control

274 9 In-combustion Air Emission Control

when a diesel engine load changes from full load to idling state. And, the CO 2
concentration changes with an opposite direction. As a result, the effect in NO x
reduction by EGR depends on the diesel engine load.

9.7 Practice Problems

1. A coal having 4 % of ash content and 1.0 % of sulfur content by weight is
burned by power plant at a rate of 5,000 tons/day. Calculate the amount of
calcium carbonate (CaCO 3 ) needed to capture 90 % of the sulfur dioxide.
Assume molar ratio Ca:S = 2.
2. A power plant burns coal at a rate of 6,000 tons/ day. The coal has 5 % of ash
content and 2 % of sulfur content by weight. Calculate the amount of calcium
oxide (CaO) needed to capture 100 % of the sulphur dioxide. Assume molar
ratio Ca:S = 3.
3. The emission rate of NO x from a truck is 2.5 g/km. Determine the conversion
efficiency of a catalytic converter in order to meet an emission standard of
0.25 g/km.
4. In-combustion NO x control can be achieved by air staging burner, where
combustion is fuel rich in
a. the primary zone
b. the secondary zone
c. both primary and secondary zones
d. neither primary or secondary zone.
5. There are three steps in fuel staging combustion, and the combustion follows the
order of

a. fuel rich, fuel lean, fuel rich
b. fuel lean, fuel rich, fuel lean
c. fuel rich, fuel rich, fuel lean
d. fuel rich, stoichiometric, fuel lean.
6. In an in-combustion SO 2 capture by lime stone injected into the furnace, the Ca:
S molar ratio is 2, because

a. 2 mol of Ca is needed in order to react with 1 mol of SO 2
b. 2 mol of Ca is needed in order to react with 1 mol of SO 3 and 1 mol SO 2
c. the sorbent cannot be used effectively
d. more sorbent is needed to continue the reaction along the flue when the gas
exist the furnace.