Method of bleaching pulp with ozone wherein the acidity is maintained with an acid solution prepared by electrolysis or electrodialysis
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United States of America Patent
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Mar 21, 2000
Issued Date -
N/A
app pub date -
Jul 9, 1998
filing date -
Sep 17, 1991
priority date (Note) -
Expired
status (Latency Note)
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Abstract
When closing the process of manufacturing cellulose pulp of high brightness, i.e. including the recovery of essentially all waste liquor, there is an untenable enrichment of certain basic elements, such as sodium and sulphur. The present invention provides a partial solution to this problem and is concerned with a method in bleaching with ozone lignocellulosic material, e.g. cellulose pulp, which has been at least partially manufactured chemically, in the presence of water at a degre of acidity, expressed as pH, of 2-5. The method is characterized in that the acidity is maintained during the ozone bleaching process by adding a sulphuric acid solution or an acid sodium sulphate solution produced by electrolysis or electrodialysis of an essentially neutral sodium sulphate solution obtained by recycling chemicals in a system to which waste liquor from the ozone bleaching process is added.
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