2 minute read
Amazing ammonia
SCIENCE
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How to make ammonia
The key stages behind the Haber-Bosch process
1b. Hydrogen
Hydrogen gas fl ows into the other tube and then mixes with the nitrogen.
1a. Nitrogen
After being fi ltered for impurities, nitrogen taken from the air fl ows into one tube.
3. Converter
The mixture of hot gases enters the next chamber which is also pressurised and heated to 450°C (842°F).
7. Recycling
The remaining unreacted gas is returned to the heating chamber for maximum effi ciency.
2. Compressor
Exposed to 200 atmospheres of pressure, the molecules gain kinetic energy and begin to heat up and break down.
4. Catalyst
Inside the converter are several shelves of iron, along with other metal oxides, which speed up the gas’s conversion into ammonia. Ammonia is immensely valuable as plant and crop fertiliser
5. Condenser
The next chamber is fi lled with cold water and, as the ammonia gas cools, some of it turns to liquid.
Amazing ammonia
Find out how we use this pungent chemical day to day
6. Runoff
The liquid ammonia that has been condensed drips out here to be extracted.
Ammonia is a compound gas that is most commonly used as a fertiliser, but also as a domestic cleaner and to make explosives, dyes and everyday synthetic fabrics, such as nylon.
The main method by which ammonia can be created artifi cially is the Haber-Bosch process during which nitrogen and hydrogen gas are combined. Nitrogen from the air and natural gas-derived hydrogen get combined in a 1:3 ratio (N2+3H2 <=> 2NH 3) at around 450 degrees Celsius (842 degrees Fahrenheit) while under 200 atmospheres of pressure, using a catalyst to speed up the reaction.
Once combined and cooled, around 15 per cent of the gas mix forms liquid ammonia. The remaining gases loop back into the system for it all to begin again, resulting in an impressive conversion rate of around 98 per cent.
Ammonia’s primary use is as agricultural fertiliser. In its non-chemically produced state, ammonia is created when amino acids break down. When put into soil, plants are able to absorb the reactive nitrogen atoms easily and then use them in the composition of their own amino acids, which are required for growth and repair. Another lesser-known application of ammonia is as rocket fuel (see ‘3,2,1, blast off!’).
Ammonia is also used in hair colouring to open out the cuticle, allowing the colours to seep deep into the hair cortex, but repeatedly doing this can dry hair out and damage it.
3, 2, 1, blast off!
Hydrazine is a chemical relative of ammonia. First created in 1889, it can be used to manufacture rocket fuel. It has since been replaced by unsymmetrical dimethylhydrazine (UDMH), but was one of the fuels used in the Apollo 11 mission to the Moon in 1969.
Hydrazine is created when an ammonia solution reacts with sodium hypochlorite, or when ammonia comes directly into contact with hypochlorite ions, creating chloramine. This then reacts with the remaining ammonia to produce hydrazine. This is known as the Raschig process. When hydrazine reacts with oxygen it burns intensely, producing steam and nitrogen as chemical by-products to propel the rocket.
