Haber Process

Ammonia synthesis – Haber process
The final stage, which is the actual Haber process, is the synthesis of ammonia using an iron catalyst promoted with K2 O, CaO and Al2 O3 :
 * N2 (g) + 3 H2 (g) ⇌ 2 NH3 (g)  (ΔH = −92.22 kJ·mol−1 )

This is done at 15–25 MPa (150–250 bar) and between 300 and 550 °C, passing the gases over four beds of catalyst, with cooling between each pass to maintain a reasonable equilibrium constant. On each pass only about 15% conversion occurs, but any unreacted gases are recycled, so that eventually an overall conversion of 97% can be achieved.

The steam reforming, shift conversion, carbon dioxide removal, and methanation steps each operate at absolute pressures of about 2.5–3.5 MPa (25–35 bar), and the ammonia synthesis loop operates at absolute pressures ranging from 6–18 MPa (60–180 bar), depending upon which proprietary design is used.

There are many engineering and construction companies that offer proprietary designs for ammonia synthesis plants. Haldor Topsoe of Denmark, Lurgi AG of Germany, Uhde of Germany, Saipem/Snamprogetti of Italy and Kellogg, Brown and Root of the United States are among the most experienced companies in that field.[citation needed]