| 摘要 |
In a known process for preparing calcium sulphate hemihydrate, especially alpha -hemihydrate, from flue gas of furnaces, the flue gas is dedusted at least partially and scrubbed with a calcium-containing scrubbing liquid. The calcium sulphite formed is oxidised to give calcium sulphate dihydrate. In order to remove the chlorides introduced via the coal, the dihydrate, prior to conversion into the calcium hemihydrate, is washed and centrifuged. Wash-centrifuging requires quite complex equipment. In order to simplify the process it is proposed, according to the invention, that the calcium sulphate dihydrate produced be converted in the oxidised scrubbing liquid or part thereof into calcium sulphate hemihydrate without first removing the chloride fractions. The alpha -hemihydrate obtained by recrystallisation and the beta -hemihydrate obtained by calcination have better properties, in spite of their high chloride percentage, than the previously aimed-for low-chloride hemihydrates. <IMAGE>
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