Ammonia synthesis is used to produce ammonia from nitrogen and hydrogen. The produced ammonia can then be used as a fertilizer, or it can be further processed into urea or nitric acid. A mixture of hydrogen and nitrogen, usually originating from a steam reformer, is admitted to the synthesis loop and then compressed in two stages into the synthesis pressure of 150-300 bar (2200-4400 psi). The stream is preheated by heat exchange with the hot effluent coming out of the converter before entering the ammonia converter.
The ammonia conversion process is a compromise between temperature and pressure. For the catalyst to be efficient a temperature of at least 400 °C (750 °F) is needed,
but since the reaction is exothermic a higher temperature negatively affects product yield. To counter this issue, the pressure is increased to push the reaction equilibrium toward ammonia (thus increasing product yield). Heat is recovered from the effluent by generating steam and by pre-heating the incoming feed. The effluent is then sent to refrigeration before the product is separated from the medium and unreacted gas is recycled to the start of the synthesis loop.
This ammonia synthesis flow diagram is intended to be a representation and should not be viewed as an actual process flow diagram.