| 摘要 |
PROBLEM TO BE SOLVED: To provide the methods for increasing the pulp production efficiency, for example, increase in pulp yield, in the batchwise production of kraft pulp. SOLUTION: In the first step, a lignocellulosic substance and the first alkaline cooking liquor containing polysulfide sulfur and sodium carbonate are charged in the reactor vessel and they are held at 100-130 deg.C to impregnate the lignocellulosic substance with the first alkaline cooking liquor. After completion of the impregnation step, the second cooking liquor containing sodium sulfide, sodium hydroxide and polysulfide sulfur is added to the reactor vessel and they are held at 160-180 deg.C to continue cooking.
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