Oxidation of Ammonia by Air

outlet temperature in °C

700

Ammonia is oxidized by air to form nitric oxide, as the first step in the production of nitric acid. The two principal reactions that occur are

4

NH

3

(g)+5

O

2

(g)→4NO(g)+6

H

2

O(v)

(reaction R1) and

2

NH

3

(g)+

3

2

O

2

(g)→

N

2

(g)+3

H

2

O(v)

(reaction R2). The inlet and outlet conditions are given in the reactor's flowchart. You can set the temperature of the outlet stream. The extent of reaction R1 is



ξ

1

=22.5mol/min

, while the extent of reaction R2 is



ξ

2

=5.0mol/min

.

The standard enthalpies of reactions R1 and R2 are

Δ

0



H

r,1

=-904.74kJ/mol

and

Δ

0



H

r,2

=-633.11kJ/mol

, respectively. All of the heat requirements for the formations are obtained from [1, Appendix B1].

This Demonstration computes the heat added to the reactor



Q

in kW. For this purpose, we make use of the energy balance equation for reactive systems:



Q

=Δ



H

=



ξ

1

Δ

0



H

r,1

+



ξ

2

Δ

0



H

r,2

+

∑

i

out





n

i



H

i



-

∑

i

in





n

i



H

i



(i.e. the heat of reaction method). The specific enthalpies of all components are computed using the temperature-dependent expressions of the constant-pressure heat capacities given in [1, Appendix B2]. In addition, we chose as reference states the molecular species

Air(g)

,

N

2

(g)

,

O

2

(g)

,

NH

3

(g)

,

NO(g)

and

H

2

O(v)

at 25 °C and 1 atm.