The production of ammonia is one of the important industrial processes that you need to know about for your GCSE Chemistry exam. Ammonia is used to make many other materials such as nitric acid, explosives, nitrogen containing organic chemicals and fertilisers. Without the fertilisers made using ammonia, the world would probably not provide enough food to support the human population. It is used directly in many other products and processes including industrial fermentation and household cleaning products.
Fritz Haber, the man who invented the Haber process for production of ammonia, was a talented chemist. If you study A-level chemistry, you will come across him in several places. He was married to a very accomplished scientist, Clara. Unfortunately at the time, women's achievements were rarely acknowledged and she did not get any credit for the help she gave her husband in his work. Her husband was involved with the development of chemical weapons and is sometimes referred to as the 'father of chemical warfare'. Clara was staunchly opposed to this and committed suicide shortly after the first use of poisonous gas in World War I.
The industrial production of ammonia from nitrogen and hydrogen requires high temperatures, high pressures, an iron catalyst and is a reversible reaction. The nitrogen comes from the air whilst the hydrogen is usually obtained by reacting steam with natural gas. The two gases are continuously cycled and recycled through the reaction vessel. During the recycling, they are cooled to remove the ammonia and fresh nitrogen and hydrogen are added. The process is therefore continuous and you are expected to know the factors that affect the manufacturing costs. Since the equipment runs all day and every day, automating the process is a good way for manufacturers to save money. The recycling of the gases is also a simple way of keeping costs down.
The pressures and temperatures used are always a compromise in order to make the process economically worthwhile and are the key factors that increase the costs. Using higher pressures would increase the amount of ammonia produced, however, the extra cost of building the equipment that could generate and withstand such pressures would not be balanced by the sale of the extra ammonia. Energy costs could be reduced by lowering the temperature but the reaction would slow dow too much and it would not be possible to satisfy the demands of customers. The iron catalyst is useful here as it speeds up the reaction, meaning that temperatures can be kept relatively low.