| 摘要 |
The secondary reformer of an ammonia production process is fed with moderately oxygen-enriched air such as from a simple air separation plant producing also nitrogen, which preferably is used to aid start-up or shut-down or to keep the process plant in a hot standby condition. In such or similar processes energy economy is improved by allowing 5 - 15% of the starting hydrocarbon to pass through unreformed. …<??>Hydrocarbon feedstock and steam are preheated in furnace 18, partly reacted in adiabatic catalyst 22, reheated in furnace 24 and reacted in secondary reformer 30 with oxygen-enriched air from air separation plant 27. The secondary reforming reaction is incomplete (outlet CH4 0.7% <v>/v, dry basis); its outlet gas is subjected to carbon monoxide shift 35, 37, steam and CO2 removal 48, methanation 54 and drying 56, 62, and passed to ammonia synthesis (items 64-78), from which a purge stream is taken at 78 and separated at 80 to give inter alia recycle hydrogen stream 82 and methane-containing stream 86. |
