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Sture Erik Noreus

Bengt G Hultman

Per Stefan Svensson

A cyclic process is provided for utilizing sodium values in sulfate cellulose pulping, in which sodium losses normally are less than sodium additions to the process, thus tending to build up a sodium surplus, and which includes the steps of pulping cellulosic material with a pulping liquor comprising sodium hydroxide and sodium sulfide, separating spent pulping black liquor, evaporating and combusting the black liquor to recover sodium values as sodium sulfide and sodium carbonate, dissolving the sulfide and sodium carbonate in water to form green liquor, causticizing the green liquor with calcium hydroxide to form white liquor, and recycling white liquor to form pulping liquor, the improvement comprising maintaining sodium balance at least in part by removing sodium values as white liquor, oxidizing the white liquor with air at an elevated temperature, and utilizing the oxidized white liquor as a source of alkali in another cellulose pulp treatment process.

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Sture Erik Noreus