| 摘要 |
<p>1445276 Bleaching cellulose pulp INTERNATIONAL PAPER CO 28 Feb 1974 [7 March 1973] 9218/74 Heading D1P Oxygen bleaching of cellulose pulp in alkaline aqueous suspension is effected by applying an initial pressure to the pulp having oxygen dissolved and finely dispersed therein so as to agglomerate bubbles, the maximum permitted bottle diameter being 1/16 inch, and thereafter gradually reducing the pressure without substantial agitation of the slurry, to provide a pressure gradient of between 1 and 10 atmospheres, the temperature being between 70‹ and 120‹C, the pulp consistency from 2-10% by weight and the pH between 9 and 14, and the addition of cellulose degradation inhibitors, e.g. magnesium carbonate, being unnecessary. The pressure gradient may be applied by passing the pulp slurry upwardly through a vertical tower preferably between 40 and 300 feet tall. A prepressurisation of up to 300 psig may be applied briefly to the slurry before entering the tower. The oxygen may be intimately dispersed and dissolved in the slurry by a high-shear agitator to provide 0.1-4% by weight of oxygen in the slurry, agglomerated bubbles being subsequently vented to atmosphere before the pressure gradient is applied. The process may be a continuous one utilising conventional pulp bleaching towers, etc.</p> |
