Oji Paper Co., Ltd.

Junichiro Kido

Hajime Yamanaka

Masaru Hirasawa

Keiichi Tsuchiya

Isao Wada

Yoichi Shin

Shigeru Eimaeda

A cellulose pulp slurry is delignified in an apparatus comprising a vertical cylindrical barrel chamber, a cone-shaped bottom chamber connected to the barrel chamber and having a circular inlet formed in a lower end portion thereof, and a cone-shaped top chamber connected to the barrel chamber and having a circular outlet formed in a top end portion thereof, in which apparatus the cone-shaped top and bottom chambers converge at a convergence angle of 60 degrees or less respectively, by feeding a cellulose pulp slurry containing an alkali and oxygen and having a pulp consistency of 8 to 15% into the apparatus through the circular inlet of the bottom chamber at 70.degree. C. to 140.degree. C., and discharging the pulp slurry through the circular outlet of the top chamber, while controlling the flow speed of the pulp slurry in the barrel chamber to a level of 0.4 m/min or more.

Apparatus and process for the delignification of cellulose pulp

Lignocellulosic material is pulped by a process comprising the steps of: introducing a molecular oxygen-containing gas, such as air, into an alkaline sulfide solution containing NaOH, Na.sub.2 S and at least one cyclic organic compound selected from quinone, hydroquinone, 9,10-diketohydroanthracene and 9,10-dihydroxyhydroanthracene compounds, to oxidize at least a portion of Na.sub.2 S; delignifying the lignocellulosic material with an alkaline sulfide cooking liquor containing the oxidized alkaline sulfide solution at an elevated temperature and; then, recovering the resultant pulp from the delignification mixture.

Process for pulping lignocellulosic material with a preoxidized alkaline

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Kasugai, Japan

Junichiro Kido