The synthesis unit of the ammonia plant is designed to produce a NH3 content of about 16% by volume in the recycle gas downstream of the converter. In order to avoid N2 and H2 losses, the unconverted gas must be fed back to the converter. Before returning the gas to the converter, the NH3 previously formed must be removed from the recycle gas. This is done by cooling the hot reaction gas to a temperature below the dew point of ammonia, as a result of which liquid ammonia is obtained. A separator serves to separate the liquid phase from the gaseous phase. Total ammonia condensation is not possible for equilibrium reasons.