GB333426A - Process of and apparatus for effecting continuous digestion in the extraction of cellulose - Google Patents

Abstract

333,426. Holmes, J., and Kingcome, H. A. Sept. 20, 1929. Pulp, preparation of. - In a, process for the continuous digestion of fibrous vegetable material for the extraction of cellulose, the material is subjected to a graduated treatment whereby the more easily hydrolyzable constituents are eliminated first and the more highly resistant lignone treated with clean cooking liquor at the desired maximum temperature for a final digestion, the resultant cellulose being subjected to a countercurrent washing operation before being discharged' from the apparatus. The material is fed by a conveyer A to a mechanical conveyer B which passes it through the apparatus as indicated by the arrows. The material first passes through boiling water zones a, band c, d a vacuum head V being maintained corresponding to these two columns. A column of treatment liquor e, f is maintained in the vertical member J. The vapour pressure in the head S added to the pressure of the column e, f gives a higher pressure in the vapour head T, the vapour of which extends from f to g. Liquor is maintained in the vertical members L, N between the levels g, k, the desired maximum digestion pressure being thus obtained in the horizontal member M. Heating of the member M is effected by a steam jacket. The condensate may be used to heat the vertical members for the water treatment to further extract heat, the final condensate being admitted at m as wash-water. The discharged material passes out of the apparatus at R. A simpler apparatus omitting the vacuum treatment may be used for esparto grass. Pumps connected by pipes at suitable points in the apparatus may be used to circulate the cooking liquors and washwater and to agitate the material.