Patent ID: 8080129
Filing Date: 2011-12-20
Classification: D21C

Abstract:
1. A method of delignifying bleaching of alkaline-sulphite anthraquinone (AS/AQ) wheat straw pulp labelled as AOPsYP 0 comprising the steps of: (a) Mechanical pressing of pulp to consistency greater than 15%; (b) Acidification (A) with 2.0% sulphuric acid on the oven dried pulp; (c) First wash with distilled water until the pulp shows neutral pH; (d) Mechanical pressing of pulp to consistency greater than 10%,; (e) Delignification by oxygenation (O) using pure oxygen feed at 70-75 psig pressure in a revolving closed loop digester; (f) Second wash with distilled water until the pulp shows neutral pH; (g) Mechanical pressing of the pulp to consistency greater than 10%; (h) Extended delignification and bleaching with 5.0% potassium peroxymonopersulfate (Ps) concentration on the oven dried pulp; (i) Third wash with distilled water until the pulp shows neutral pH; (j) Mechanical pressing of pulp to consistency greater than 10; (k) Reductive bleaching step (Y) using 0.2% sodium dithionite on oven dried pulp; (l) Fourth wash with distilled water until the pulp shows neutral pH; (m) Mechanical pressing of pulp to consistency greater than 10%; (n) Oxidative bleaching using 3.0% hydrogen peroxide (P (o) Fifth wash with distilled water until the pulp shows neutral pH.