<P> This conversion is typically conducted at 15--25 MPa (150--250 atm; 2,200--3,600 psi) and between 400--500 ° C (752--932 ° F), as the gases (nitrogen and hydrogen) are passed over four beds of catalyst, with cooling between each pass so as to maintain a reasonable equilibrium constant . On each pass only about 15% conversion occurs, but any unreacted gases are recycled, and eventually an overall conversion of 97% is achieved . </P> <P> The steam reforming, shift conversion, carbon dioxide removal, and methanation steps each operate at pressures of about 2.5--3.5 MPa (25--35 bar; 360--510 psi), and the ammonia synthesis loop operates at pressures ranging from 6--18 MPa (60--180 bar; 870--2,610 psi), depending upon which proprietary process is used . </P> <P> The major source of hydrogen is methane from natural gas . The conversion, steam reforming, is conducted with steam in a high temperature and pressure tube inside a reformer with a nickel catalyst, separating the carbon and hydrogen atoms in the natural gas . </P> <P> Nitrogen (N) is very unreactive because the molecules are held together by strong triple bonds . The Haber process relies on catalysts that accelerate the scission of this triple bond . </P>

Where does hydrogen come from in the haber process