Ammonia production process

Claim 1

An ammonia production process which comprises (a) primary catalytically reforming a hydrocarbon feedstock with steam at superatmospheric pressure and in conditions of steam-to-carbon ratio, pressure and temperature to produce a gas containing carbon oxides, hydrogen and at least 10% v / v methane on a dry basis; (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, the quantity of air used being in excess of what would introduce 1 molecule of nitrogen per 3 molecules of hydrogen; (c) converting carbon monoxide catalytically with steam to carbon dioxide and hydrogen; (d) removing carbon oxides to give a nitrogen-hydrogen ammonia synthesis gas; (e) reacting the synthesis gas to produce ammonia and recovering ammonia from the reacted gas; and (f) treating synthesis gas after reaction to synthesise ammonia to separate a stream enriched in hydrogen and returning the enriched stream to the synthesis; and is characterised by X. controlling the rate of flow of the stream enriched in hydrogen so that the hydrogen to nitrogen molar ratio of the gas entering the synthesis catalyst is in the range 1.0 to 2.5; and Y. operating step (a) in at least one adiabatic catalyst bed and providing the endothermic heat of reaction by preheating the reactants, whereby the temperature of the reacting gas falls as it proceeds through the catalyst bed.