The ammonia concentration at equilibrium is small under high temperatures. Then, plenty of H2 and N2 remains unreacted and needs to be recycled from the viewpoint of cost. For recycling, we employed a general method in ammonia synthesis, refrigeration under high pressure, to make ammonia liquid and separate the product liquid and the reactant gases. The refrigeration temperature was adjusted to bring the NH3 molar concentration at the reactor inlet to 3 %, the typical value for the ammonia collection in the plant. Water was utilized to initial cooling to room temperature (30 °C), and the cooled nitrogen gas in cryogenic air separation was used in the second. The pressure of the NH3 product was released, and its latent heat and cold heat were utilized to lower the temperature, followed by the compression of the product to be liquid under 20 bar at room temperature, 30 °C (Fig. )). In the plant embedded with Ru/Ca(NH2)2 at 10 bar, the refrigeration process differs from others because the required temperature for cooling was too low, -33.3 °C, the boiling point of ammonia.