seen and apparatus for alkali of fibrous vextmaterial as straw

摘要

Method and apparatus for treating fibrous plant material, preferably straw, with aqueous alkali solution, preferably soda lye. The straw is supplied at the bottom of a container (1) filled with aqueous alkali solution which is characterized in that it has no uniform alkali concentration but an alkali gradient such that the alkali concentration is highest at the bottom of the container (1) and lowest at the top thereof. While rising upwardly in the container by its own buoyancy, the straw is thus treated with aqueous alkali solution of successively decreasing concentration. Finally, the straw is removed from the top of the container (1) and flushed. In the flushing operation only so much fresh flushing water is supplied as corresponds to the liquid absorbed by the straw. As a result, a closed system in respect of the treating liquid will be obtained. The container has supply means (2) for supplying plant material (3) and lye of high concentration (5) at the bottom and a grid (9), conveying means (11) and flushing means (13, 16) for the plant material at the top. Besides, the container has at least one levelling vessel (17) between the top and the bottom for adjusting the liquid level in the container upwardly and downwardly by supply and withdrawal, respectively, of liquid and resultant control of the level of the straw column in the container.