Control of NO x

Two distinct reduction methods 1.Control over the reaction that produces the pollutant. (3T) 2.Removal of the pollutant after its formation

Combustion control methods for NO x from Stationary Sources 1.Effect of excess air 2.Effect of combustion air temperature 3.Effect of combustion-zone cooling 4.Effect of furnace-burner configuration 5.Flue gas recirculation 6.Two-stage or Off-stochiometric combustion 7.Status of combustion modification techniques

Effect of Excess Air

Effect of Combustion Air Temperature Waste heat is avaliable to help preheat air entering a combustion process. The added gas increases the flame temperature. Thus, NOx emissions increase. Significant formation occurs from C to C pre-heat (as 3-fold)

Effect of Combustion-Zone Cooling

Effect of Furnace-Burner Configuration

Flue-Gas Recirculation A portion of cooled flue gas is injected back into the combustion zone. Overall combustion temperature is reduced. Additionally O 2 amount is reduced. Gives the operator an additional element of control In amounts of up to 25 %, the recirculated gas negligible effect on flame development.

Two-Stage of Off-Stochiometric Combustion Fuel and air are burnt near stochiometric conditions. First fuel-rich feed Second fuel-lean feed

Status of Combustion Modification Techniques

Flue-Gas Control Methods for NOx Selective Catalitic Reduction Optimum reduction occurred 300 to C Platinum (Pt) or Palladium (Pd) optimum operation temperature C VnO 5 or TiO 2 optimum operation temperature C 75 to 90 % removal efficiency is possible

Selective Non-Catalitic Reduction Urea or ammonia based chemical are injected 900 to C is needed for reaction Catalyst is eliminated 20 to 60 % reduction is possible

Example : 50 ppm NO is going to be reduced to 10 ppm. Determine the NH 3 amount needed for a plant having flowrate of 10 Nm 3 /sec