*3.1. Ammonia*

Ammonia can be dissociated into nitrogen and hydrogen. It is a very interesting option when considering the development of hydrogen economy, as ammonia transport over long distances is much easier than that of hydrogen. At the same time, unlike hydrogen, storage and transportation of ammonia does not require the use of special expensive cryogenic containers. Ammonia can be stored and transported in standard liquid hydrocarbon storage tanks [50].

A mixture of nitrogen and hydrogen of the required composition can be obtained by reforming natural gas using atmospheric air and water, followed by the separation of CO2 from the synthesis gas. Then, in the column for ammonia synthesis on a catalyst (promoted iron) at temperature 390–530 ◦C, an exothermic reaction of ammonia formation from a nitrogen-air mixture takes place:

$$\text{3H}\_2 + \text{N}\_2 \leftrightarrow \text{2NH}\_3 + \text{111.5 kJ/mol},\tag{1}$$

The circulation gas after leaving the synthesis column, depending on the technology used, comes out with a temperature of up to 350 ◦C and an ammonia content of up to 19.9%. The heat of reaction of ammonia synthesis is used to heat the feed water supplied to the waste heat boiler to produce high pressure steam.

The ammonia condensation is carried out in two stages. The gas is cooled with water, air, and evaporating ammonia. The condensed ammonia is separated in a separator and the gas is directed to a circulation compressor.

Ammonia refrigeration is provided to the units by ammonia compressor or absorption refrigeration units. The produced ammonia can be supplied to consumers both in liquid and gaseous form [51]. In liquid form, ammonia can be transported over long distances in a special tanker or containers on cargo ship.
