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|1. (WO1984002123) A METHOD FOR PRODUCING PURE SULPHURIC ACID AND A HIGH-GRADE MERCURY PRODUCT FROM GASES THAT CONTAIN SULPHUR DIOXIDE AND MERCURY|
|Title:||A METHOD FOR PRODUCING PURE SULPHURIC ACID AND A HIGH-GRADE MERCURY PRODUCT FROM GASES THAT CONTAIN SULPHUR DIOXIDE AND MERCURY|
Method in the production of sulphuric acid from sulphur-dioxide containing gas obtained when treating mercury-containing raw materials and intermediate products, for obtaining pure sulphuric acid and a high-grade mercury product. The gas is cleansed from accompanying gaseous mercury, by contacting the gas with sulphuric-acid solution in one or more stages (1, 2), so that the major part of the mercury is absorbed and dissolved in a concentrated solution having a sulphuric-acid concentration of at least about 85%, whereafter the purified gas is passed through a contact plant (3, 4) for producing purified sulphuric acid. The method is characterised by removing a part quantity (48) of the concentrated sulphuric-acid solution (33), and diluting the part quantity to a sulphuric-acid concentration of about 80%, or there below, the major part of the mercury dissolved in the sulphuric-acid solution being separated therefrom in the form of a high-grade mercury product (54) which, if so desired, can be separated from the solution (52). The sulphuric-acid solution can then be purified of residual, dissolved mercury, whereafter the sulphuric-acid solution, free of mercury, can be removed for use in its present form, or can be passed to an absorption tower (4) in the contact plant, for the production of pure, concentrated sulphuric-acid.