SYNTHESISING AMMONIA IN LATER STAGE OF A HYDROCARBON-STEAM REFORMING PROCESS

摘要

In a process for producing ammonia which comprises: primary (4) and secondary (60) catalytically reforming shift conversion (80 and 90); carbon oxides removal (115); and ammonia synthesis (110), wherein at least a portion of an ammonia-depleted gas stream is recycled to the synthesis zone (110); and sidestream (134) of the ammonia-depleted gas is treated to separate a stream (142) enriched in hydrogen for return to the ammonia synthesis zone; the improvement which comprises: (i) operating step (b) at a temperature in the outlet gas of not greater than about 946 DEG C and with an amount of air sufficient to provide from about 3 to 11 molar % excess N2 and to form a secondary reformer outlet gas containing at least 0.8 vol. % methane; (ii) operating step (e) under conditions sufficient to provide at least 10 vol. % inert gases in the ammonia-depleted gas stream; and (iii) introducing as synthesis gas feed to the ammonia synthesis zone a mixture comprising the synthesis gas formed in step (d) having a methane content of at least about 1.2 mol.% CH4, on a dry basis, the recycled gas produced in step (f) plus the hydrogen-enriched gas stream formed in step (g), whereby the H2 loss from the process with the separated inerts enriched gas stream is minimized.