Ammonia (NH₃) is a colorless, pungent-smelling inorganic compound composed of nitrogen and hydrogen. It is one of the most important industrial chemicals globally and forms the backbone of the nitrogen fertilizer industry. Over 70% of global ammonia production is used directly or indirectly in fertilizer manufacturing, making it critical to modern agriculture and food security.
Chemical Composition
| Element | Composition |
|---|---|
| Nitrogen (N) | 82.35 wt% |
| Hydrogen (H) | 17.65 wt% |
| Molecular Weight | 17.03 g/mol |
| Chemical Formula | NH₃ |
✔ Simple molecular structure
✔ Extremely high nitrogen density
Key Physical Properties
| Property | Value |
|---|---|
| Physical State | Gas (at STP) |
| Color | Colorless |
| Odor | Sharp, pungent |
| Density (gas, 1 atm) | 0.73 kg/m³ |
| Density (liquid, −33°C) | ~682 kg/m³ |
| Boiling Point | −33.34 °C |
| Melting Point | −77.7 °C |
| Solubility in Water | Very high |
| pH (aqueous) | ~11.6 |
| Vapor Pressure | High |
Mechanical & Metallurgical Behavior
Ammonia is not a structural material. Mechanical design focuses on pressure containment and material compatibility.
✔ Nitriding agent for steels
✔ Forms hard iron nitrides (Fe₄N, Fe₂–₃N)
✔ Improves surface hardness, wear resistance, and fatigue life
🚫 Avoid contact with copper, zinc, and brass due to stress corrosion.
Industrial Production – Haber–Bosch Process
Reaction: N₂ + 3H₂ → 2NH₃
Operating Conditions
Temperature: 400–500 °C
Pressure: 150–300 bar
Catalyst: Iron-based with promoters
Applications
Agriculture: Fertilizers (urea, ammonium nitrate, ammonium sulfate)
Chemical Industry: Nitric acid, explosives, nylon, resins, pharmaceuticals
Refrigeration: Industrial refrigerant R-717
Metallurgy: Gas nitriding, annealing atmospheres
Environmental: NOₓ reduction, water treatment
Advantages
✔ Extremely high nitrogen content
✔ Cost-effective fertilizer base
✔ Carbon-free at point of use
✔ High refrigeration efficiency
✔ Key enabler of green hydrogen economy
Ammonia vs Other Nitrogen Carriers
| Property | Ammonia | Urea | Nitric Acid |
|---|---|---|---|
| Nitrogen % | 82% | 46% | ~22% |
| Transport | Pressurized | Solid | Corrosive |
| Reactivity | High | Moderate | Very High |
| Storage | Complex | Easy | Complex |