| 摘要 |
<p>Flue gases etc. may contain SO2 which should be prevented from admission to the atmosphere. SO2 is oxidized to SO3 and condensed with steam to H2SO4-vapours which are condensed in vertical glass tubes cooled from the outside. In principle the condensate is collected near the bottom of the tubes. In the cooling process a mist of very small H2SO4 droplets is formed and tends to escape to the atmosphere. Environmental regulations continually increase the demands on reducing the amount of acid mist escaping. According to the invention an important method to achieve a reduction of the escape of acid mist is to pass the gas leaving each tube through an aerosol filter in gastight connection with the tube top. Such a filter may consist of acid resistant fibres or filaments having a thickness of 0.04 - 0.7 mm and may be arranged in specified manners to ensure a drop of pressure through below 20 mbar. Moreover, the sulfuric acid caught in the filter is caused to flow downwardly through the tube countercurrently with the feed gas. Various embodiments of filters and filter media for the purpose are disclosed. The sulfuric acid recovered is highly pure and highly concentrated.</p> |
