To provide an extremely economical method for producing pulp by which both the pulp and lignin can efficiently be obtained to reutilize a high-boiling organic solvent used and extremely low pressure is sufficiently used in a pulping step with ultralow equipment cost and operating cost.
A pressure-resistant vessel is filled with a vegetable biomass raw material (pulp raw material) containing a woody material and wastes, etc., of agricultural products and an alcoholic solvent containing the high-boiling organic solvent soluble in alcohols and having a boiling point under atmospheric pressure of 150-290C and a heat treatment is carried out to pulp the pulp raw material. The pulp (crude pulp) and a waste liquid are separated from a cooking liquor after the pulping and the separated pulp is then washed with the alcoholic solvent containing the high-boiling organic solvent to afford the pulp. Water is added to the waste liquid from the pulping step and a pulp washing effluent to precipitate the lignin. The solvent containing the high-boiling organic solvent is recovered from a filtrate after separating the lignin and the recovered high-boiling organic solvent is reutilized in the pulping step and/or pulp washing step.
SEKIGUCHI YOSHITOSHI
SUZUKI HIDEO
Einosuke Kishimoto
Akira Watanabe
Kiyosue Yasuko