ESSENCE OF CHEMICAL PROCESS ENGINEERING I - EXERCISE 1

EXERCISE 1

Calculate excess N₂ amount per 1 mol NH₃ production when ammonia synthesis reaction completely proceed. Assume that Air contains 80% N₂ and 20% O₂.

· NH₃ Production Reaction: N₂＋3H₂ → 2NH₃

· H₂ Production using CH₄ steam reforming reaction:

1. Ratio N₂ and H₂ In Air

Ratio Coefficient N₂ : H₂

80% : 20% (:20%)

4 : 1

28 : 7

2. Steam reforming reaction of Methane

CH₄ + 0.35O₂ + 1.3H₂O CO₂ + 3.3H₂

Ratio Coefficient O₂: H₂

0.35 : 3.3 ( x 20)

7 : 66

3. Ammonia synthesis reaction

Hydrogen gas (H₂) that is produced by steam reforming is used to ammonia synthesis reaction as follow:

N₂ + 3H₂ 2NH₃

Ratio Coefficient N₂ : H₂

1 : 3 (x 22)

22 : 66

4. Ratio of all elements

Reaction: N₂ + 3H₂ 2NH₃

(N₂ Consumption) : H₂ : NH₃ N₂ (in air)

1 : 3 : 2

22mol : 66mol : 44mol 28mol

For 1 mol NH₃ each component divided by 44 mol

(N₂ Consumption) : H₂ : NH₃ N₂ (in air)

22/44mol : 66/44 mol : 1 mol 28/44 mol

N₂ excess of Ammonia Synthesis Reaction per 1 mol NH₃

N₂Excess = (N₂ in air) – (N₂consumption)

= 28/44 - 22/44

= 6/44 mol

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