A METHOD FOR PRODUCING PURE SULPHURIC ACID AND A HIGH-GRADE MERCURY PRODUCT FROM GASES THAT CONTAIN SULPHUR DIOXIDE AND MERCURY

摘要

Method in the manufacture of sulphuric acid from substantially dry gas containing sulphur dioxide and generated when treating mercury-containing raw materials and intermediate products, for obtaining pure sulphuric acid and a high-grade mercury product. The gas is cleansed of accompanying gaseous mercury, by bringing the gas into contact with sulphuric acid in one or more stages (1, 2) so that the major part of the mercury is absorbed in and dissolved in concentrated sulphuric acid having a concentration of at least about 90%, whereafter the purified gas is supplied to a contact plant (4) for the production of pure sulphuric acid. The invention is characterised by circulating the concentrated sulphuric acid in a circuit which comprises at least one drying tower (2), for the sulphur-dioxide-containing gas, a sludge separator (19) and an oxidation reactor (3). Gaseous elementary mercury accompanying the gas in the drying tower (2) is oxidized and absorbed in the acid, and isolated mercury compounds are separated from the acid and removed from the circuit. The thus purified acid is then brought into contact with an oxidant in the oxidation reactor (3), so that dissolved mercury present in the acid is oxidized to mercury (11) ions, which are then used in the drying tower (2) for promoting oxidation of elementary mercury.