| 摘要 |
<p>1417541 Removal of mercury from gases PREUSSAG METALL AG 4 Feb 1974 [5 Feb 1973] 05047/74 Heading C1A A gas stream is freed from vapour of free or combined mercury by reacting the mercurycontaining gases, in the presence of SO 2 and condensing H 2 O vapour, with nascent sulphur formed from H 2 S or a compound that generates H 2 S, to form solid mercury sulphide which is then precipitated from the gases. The H 2 S may be formed by adding a sulphide, e.g. sodium sulphide, to the gas stream. The gas may be at 10-70‹ C. when the mercury sulphide is formed. The precipitate may be removed by washing, with or without the aid of wet electro-filters. Any colloidal HgS formed is removed by adsorbing on to a solid substrate and precipitating as before. The precipitates are processed to yield metallic mercury. Sulphuric acid prepared from the SO 2 thus purified has a considerably lower mercury content than H 2 SO 4 not so prepared, e.g. 0À5 p.p.m. compared to 60-80 p.p.m. In one embodiment (Fig. 1), gas at 1000‹ C. from the roasting of sulphidic zinc ore in a furnace (2) is cooled progressively in units 3 and 6 to a temperature of 50-70‹ C., and finally to 30-40‹ C. in unit 9. Dust is precipitated in the cyclone 4 and a hot gas electrofilter (5); the filtered gas is then washed with recycled dilute H 2 SO 4 solution in washing tower 7. Injection of H 2 S or a source thereof, e.g. Na 2 S, at 14, produces HgS particles which are precipitated in the wet electro-filters 8 and 10.</p> |
