Method for treatment of lignocellulosic material with chlorine

Paper making and fiber liberation – Processes of chemical liberation – recovery or purification... – Gas – vapor or mist contact

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162 67, 162 87, 162 88, D21C 912, D21C 914

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042228182

ABSTRACT:
A pulp containing lignocellulosic fibers is treated with chlorine in two steps. In the first step, chlorine in the amount of 0.6-0.9 grams per gram of lignin in the fibers, is mixed in the gaseous state into the pulp and in a second step the reaction products, which contain chlorinated lignin, are removed by displacing the liquid in the pulp with a chlorine solution, the amount of active chlorine in the solution in the second step being between 0.1 and 0.3 grams per gram of the lignin initially present in the pulp. In this manner 92% delignification is achieved without any intermediate washing between the two steps and with a total amount of chlorine between 0.7 and 1.2 grams per gram of lignin. The consistency of the pulp in both steps is the same and is between 6 and 12%.

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Gullichsen "Pilot Plant Application of the Displacement Bleaching Process", TAPPI, vol. 56, No. 11, Nov. 1973.
Rapson et al. "Dynamic Bleaching Continuous Movement of Pulp through Liquor Increases Bleaching", TAPPI, vol. 49, No. 8, 8-1966.
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Gullichsen "High Density Chlorination", Preprint Version of a Paper Presented May 3-5 at Internatl. Bleaching Conference, Chicago.

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