NH₃ at equilibrium: from published equilibrium constants (Gillespie & Beattie, 1930) with their correction for real gases; within about 2 percentage points of measured data.
NH₃ per pass: schematic. The gas leaves the converter before it reaches equilibrium; the approach is faster at higher temperature and pressure. Tuned to about 15% at 450 °C and 200 atm with iron.
Both percentages are NH₃ in the gas mixture (mol %), not % yield (conversion). 15% NH₃ per pass means about 26% of the N₂ and H₂ reacted.
The catalyst only speeds up the approach. It does not change the equilibrium percentage.
Ammonia is condensed to a liquid and removed; unreacted N₂ and H₂ are recycled. "Unreacted" is worked out from the NH₃ per pass.
Heat exchanger: shown without temperatures; it only shows which gas warms which.
