Environmentally benign TCF bleaching sequences for AS/AQ wheat straw pulp
OwnerNaila Yaqoob, Ishtiaq-Ur-Rehman +3inventors
InventorsNaila Yaqoob, Ishtiaq-Ur-Rehman, Kausar Jamal Cheema, Sahibzada Rashad Hameed, Bushra Mateen
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Abstract
This invention reports an environmentally benign method of delignifying bleaching sequences to gain more than 80% ISO brightness for alkaline sulfite-anthraquinone (AS/AQ) wheat straw pulp comprising of AOPsYP0, AOPsEP0 and AOPsP0P1 sequences that yielded surprising results in the field of pulp and paper technology; wherein the selectivity of sequences resulted in the protection of α-cellulose from degradation, produced significant drop in acid soluble lignin and yielded low viscosity losses reducing ecological impact of effluent load.
Claims26
A method of delignifying bleaching of alkaline-sulphite anthraquinone (AS/AQ) wheat straw pulp labelled as AOPsYP0 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 (P0) on the oven dried pulp;
- (o) Fifth wash with distilled water until the pulp shows neutral pH.
A method of delignifying bleaching of alkaline-sulphite anthraquinone (AS/AQ) wheat straw pulp labelled as AOPsEP0 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 the 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 the pulp to consistency greater than 6%;
- (k) Conventional alkaline extraction (E) using 3.0% sodium hydroxide on the oven dried pulp;
- (l) Fourth wash with distilled water until the pulp shows neutral pH;
- (m) Mechanical pressing of the pulp to consistency greater than 10%;
- (n) Oxidative bleaching using 3.0% hydrogen peroxide (P0) on the oven dried pulp;
- (o) Fifth wash with distilled water until the pulp shows neutral pH.
A method of delignifying bleaching of alkaline-sulphite anthraquinone (AS/AQ) wheat straw pulp labelled as AOPsP0 P1 comprising the steps of:
- (a) Mechanical pressing of the 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 the pulp to consistency greater than 10%, preferably between 15% and 20%;
- (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 the pulp to consistency greater than 10%;
- (k) Oxidative bleaching using 3.0% hydrogen peroxide (P0) on the oven dried pulp;
- (l) Fourth wash with distilled water until the pulp shows neutral pH;
- (m) Mechanical pressing of the pulp to consistency greater than 10%;
- (n) Oxidative bleaching using 2.0% hydrogen peroxide (P1) on the oven dried pulp;
- (o) Fifth wash with distilled water until pulp shows neutral pH.
Dependencies are inferred from the claim text.