Process for high consistency delignification using a low consistency alkali pretreatment
US5525195A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 7, 1993 |
| Grant date | Jun 11, 1996 |
| Priority date | — |
| Expiry date | Sep 7, 2013 |
Classification
- Technology area (CPC D)Textiles; Paper
- CPC primaryD21C9/1005
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
Unbleached pulp is washed with an aqueous alkaline solution in a wash press to substantially uniformly distribute a first amount of alkaline material throughout the pulp. The consistency of the pulp exiting the wash press is above about 18%, preferably between 25 to 35 percent by weight, and the high consistency alkali containing pulp is then treated with oxygen to effect delignification. The use of a wash press reduces the overall amounts of alkaline material utilized in the process compared to processes which add alkaline material to the pulp at low consistency. Additional alkali may be applied, if desired, onto the high consistency pulp prior to oxygen delignification to provide a total amount of between 0.8 and 7 percent by weight of oven dry pulp. High strength, low lignin pulps are formed after oxygen delignification which may be further bleached to high brightness with reduced amounts of bleaching chemicals.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.