Ammonia production process

An ammonia production process which comprises

• (a) primary catalytically reforming at superatmospheric pressure a hydrocarbon feedstock with steam to give a gas containing carbon oxides, hydrogen and methane;
• (b) secondary catalytically reforming the gas from step (a) by introducing air and bringing the mixture towards equilibrium, whereby to produce a gas containing nitrogen, carbon oxides, hydrogen and a decreased quantity of methane;
• (c) converting carbon monoxide catalytically with steam to carbon dioxide and hydrogen;
• (d) removing carbon oxides to give a nitrogen-hydrogen ammonia synthesis gas and compressing said gas to ammonia synthesis pressure;
• (e) reacting the synthesis gas to produce ammonia and recovering ammonia from the reacted gas;
• and
• (f) discarding non-reactive gases present in the synthesis gas;
• and is characterized by:
• (i) operating step (a) at a pressure of 40-80 bar absolute and in conditions of steam-to-carbon ratio and temperature to produce a gas containing at least 10% v/v methane and using in step (b) a quantity of air in excess of what would introduce 1 molecule of nitrogen per 3 molecules of hydrogen;
• (ii) in step (d) compressing said ammonia synthesis gas including excess nitrogen resulting from said use of excess air in step (i) by no more than 100 bar;
• and
• (iii) treating a side stream of synthesis gas after reaction to synthesise ammonia to separate a stream enriched in hydrogen and returning the enriched stream to the synthesis.