| 摘要 |
<p>Ammonia synthesis gas is produced from hydrocarbons by successive steps of primary reforming with steam, secondary reforming with air, shift conversion and removal of oxides of carbon, wherein the steam to carbon ratio of the primary step is 4.0 to 8.0 and the pressure of the secondary reforming step is 270-650 p.s.i.a. Thus an embodiment discloses, desulphurized compressed gaseous hydrocarbon, e.g. natural gas, mixed with steam and preheated to 600 DEG F. by the combustion gases used to heat the primary reforming step. The mixture of gas and steam passes over nickel bearing catalysts in the externally fired primary reformer furnace and leaves at 1350 DEG -1650 DEG F. at 50-200 p.s.i.a. The combustion gases from the primary reformer may also be used to generate high pressure steam by burning with additional fuel in a waste heat boiler. The reformed gases are mixed with compressed air at 25 p.s.i.a., preheated, if desired, to 300-1250 DEG F. and pass to the secondary reformer which contains a nickel bearing catalyst and leave at 1650-2000 DEG F. The exhaust gases are quenched with steam and/or water, to 1100-1200 DEG F. if the gas then passes through a waste heat boiler, or to 550-700 DEG F. if the gas passes directly to the shift converter. The shift converter contains a plurality of catalyst beds with intermediate injection of steam, water or both to maintain the temperature in the range of 550-700 DEG F. The crude synthesis gas and surplus steam from the converter are passed through another waste heat boiler and also used to regenerate the solutions, e.g. aqueous monoethanolamine, potassium carbonate or ammoniacal copper liquor, used to remove CO and CO2 from the crude synthesis gas. The gas stream passes through a separator to remove steam, on to a cooling and purification plant where CO and CO2 are removed and after compression passes on to the ammonia synthesis plant. A particular embodiment of the invention and the optimum conditions for reaction are disclosed in Figs. 1 and 2 (not shown).</p> |
