Ammonia is a raw material used in the manufacture of fertilisers, explosives and cleaning fluids. It is produced using a reaction between nitrogen and hydrogen called the Haber process. Production costs of making ammonia are based on factors including the rate of reaction, and the cost of energy, labour, raw materials and equipment.
Amonia and the harber process
Ammonia, NH3, is a compound of nitrogen and hydrogen. It is a colourless gas with a choking smell, and a weak alkali that is very soluble in water. Ammonia is used to make fertilisers (as a source of nitrogen for plants), explosives, dyes, household cleaners and nylon. It is also the most important raw material in the manufacture of nitric acid. Ammonia is manufactured by combining nitrogen and hydrogen in an important industrial process called the Haber process.
The raw materials for this process are hydrogen and nitrogen:
Amonia and the harber process 2
The reaction conditions
The reaction between nitrogen and hydrogen is reversible:
nitrogen + hydrogen ammonia
N2(g) + 3H2(g) 2NH3(g)
The symbol indicates that the reaction between nitrogen and hydrogen can proceed in both directions.
In the Haber process, nitrogen and hydrogen react together under these conditions:
a high temperature - about 450°C
a high pressure - about 200 atmospheres (200 times normal pressure)
An iron catalyst is used to increase the rate of reaction.
Amonia and the harber process 3
The stages of the harber process
1. Having obtained the hydrogen and nitrogen gases (from natural gas and the air respectively), they are pumped into the compressor through pipes.
2. The gases are pressurised to about 200 atmospheres of pressure inside the compressor.
3. The pressurised gases are pumped into a tank containing beds of iron catalyst at about 450°C. In these conditions, some of the hydrogen and nitrogen will react to form ammonia.
4. The unreacted nitrogen and hydrogen, together with the ammonia, pass into a cooling tank. The cooling tank liquefies the ammonia, which can be removed into pressurised storage vessels.
5. The unreacted hydrogen and nitrogen gases are recycled by being fed back through pipes to pass through the hot iron catalyst beds again.