The Haber process sim
Nitrogen comes from the air (by fractional distillation of liquid air) and hydrogen from natural gas reacted with steam.
The Haber process · covers the GCSE, IGCSE, O-Level topic
What the sim shows
Nitrogen comes from the air (by fractional distillation of liquid air) and hydrogen from natural gas reacted with steam. They are mixed 1 volume to 3, squeezed by the compressor and passed over beds of iron in the reactor: N₂ + 3H₂ ⇌ 2NH₃, ΔH = −92 kJ/mol at 25 °C. The forward reaction is exothermic and makes fewer gas molecules, so a lower temperature and a higher pressure both give more ammonia at equilibrium. But colder is slower, and higher pressure needs thicker walls and more pumping, so 450 °C and 200 atm is a compromise. The iron makes the reaction faster; it does not change the yield. The gas leaves the reactor before it reaches equilibrium: about 15% of it reacts in one pass. In the condenser the ammonia turns to liquid and is drawn off; the nitrogen and hydrogen that did not react go round again, so almost all of it ends up as ammonia. How the numbers are worked out: the yield at equilibrium comes from Kp, using a straight van 't Hoff line fitted to standard Kp values from 300 to 600 °C (its slope gives ΔH ≈ -105 kJ/mol at these temperatures; below 300 °C the line is extended). The gases are treated as ideal: real gases give a little more ammonia at high pressure (measured, about 27% at 450 °C and 200 atm, against 24.7% here). The rate is an illustration: it rises with temperature as for an activation energy of 80 kJ/mol on iron, and in step with the pressure; without iron the barrier is 100 kJ/mol higher. The share converted in one pass is this desk's estimate, set to 15% at 450 °C and 200 atm. 0.5% of the unreacted gas is let out each time round (not drawn) so that argon from the air does not build up. Wall thickness goes in step with pressure (thin-wall rule). The particles are a picture, not a count.
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