EXTRACTION OF HEMICELLULOSES FROM POPLAR, POPULUS-TREMULOIDES, USING AN EXTRUDER-TYPE TWIN-SCREW REACTOR - A FEASIBILITY STUDY

Hemicelluloses were extracted from the hardwood Populus tremuloides vi a alkaline solubilization using a modified Clextral twin-screw extrude r Extraction yields were studied as a function of temperature and sodi um hydroxide input flow rate, and compared to batch experiments. Based on the content of pentosans, the twin-screw reactor allows extraction of up to 90% of the initial hemicelluloses, the liquid/solid ratio be ing six times less than for a batch reactor and the solid reaction tim e being much lower Moreover an efficient liquid/solid separation was o btained, even at high caustic solution flow rate, the extracted solid being drier than the starting material. At a fixed solid flow rate (2. 2 kg of dry wood/h) the solubilization of hemicelluloses was directly correlated to the specific mechanical energy (SME) absorbed by the pro cessed material. When solubilized in water extracted hemicelluloses ex hibit a thickening behavior the solution being pseudoplastic and thixo tropic. Copyright (C) 1996 Elsevier Science Ltd.