| 摘要 |
In order to improve the efficiency of nitric acid formation, cold oxygen, typically at a temperature below - 100 DEG C, is introduced into the absorption column in which the nitric acid is formed. With reference to Figure 2 of the drawings, a gas mixture containing nitrogen, oxygen and nitric oxide enters the bottom of absorption column 202 through an inlet 208, and water enters the top of the column 202 through an inlet 206. The column 202 has vertically spaced contact trays 204 down which the water descends, coming into contact with ascending gas mixture and becoming progressively richer in nitric acid. Liquid oxygen is sprayed into the column 202 at oxidation spaces 216 and 218 through vacuum-insulated spray nozzles 255 and 259 respectively. The temperature in the oxidation spaces 206 and 218 is sensed by sensors 277 and 279 respectively. If either of the sensed temperatures falls to a chosen value, relatively warm gaseous oxygen is introduced into the liquid oxygen supplied to the respective spray nozzle. Local freezing of the nitric acid is thus avoided. |
