Question

A power plant operates with 1000ppm NO_x in the flue gas. The flue gas flow rate is 2.0 x 10⁶ acfm at 300°C and 1 atm. An SCR system is being designed for 90% removal of NO_x. Calculate the stoichiometric amount of ammonia required in kg/h.

Answer 1

Reaction of NOx and NH3 are as follows

4 NH₃ + 6 NO = 5 N₂ + 6 H₂O

8 NH₃ + 6 NO₂ = 7 N₂ + 12 H₂O

So on an average for 12 moles of NOx 12 moles of NH3 are required

mole ratio = 1 .

V= 2 * 10^6 cfm

= 3398021.59 m3/hr

conc = 1000 ppm = 1000 g/m3

amount of NOx=  3398021.59 * 1000

= 3.4 * 10^9 g of NOx

moles of NOx = 3.4 * 10^9/ avg mol wt of NOx

= 3.4 * 10^9/41.3

= 82324455.2 moles

moles f NH3= moles of NOx = 82324455.2

mass of ammonia = 82324455.2 * 17

= 1399515738.4 g/hr

= 1.4 * 10^5 kg/hr is the requirement of NH3