| 摘要 |
<p>In a process for preparing alkali metal cyanides by neutralizing an alkaline solution with gases containing, besides hydrogen cyanide, at least one of ammonia, steam and carbon dioxide, the gases are treated with the alkaline solution, which may contain cyanide, in a film apparatus, which may be cooled, the gases and solution being in parallel flow, the temperature of the solution reaching at the highest 90 DEG C., the final temperature of the gases being near that of the solution, the contact time of the gases with the solution being not greater than 2 or 3 seconds and preferably less than one second, and the contact time of the solution with the gases being a few seconds, for example 5 to 6 seconds. Preferably, the vapour tension of the solution leaving the apparatus is higher than or equal to the partial pressure of the steam in the gases leaving the apparatus. The temperature of the inlet gases to the apparatus may be between room temperature and 300 DEG C. The process may be carried out either discontinuously, by neutralizing a strongly alkaline solution by contact with the gases during several cycles of the solution through the apparatus; or continuously, by use in the apparatus of a constant concentration alkaline solution which is recharged with alkali metal hydroxide after leaving and before being recycled to the apparatus. A suitable film apparatus is described and illustrated, and its use exemplified in the production of sodium cyanide.</p> |
