Pulp bleaching method wherein an ozone bleaching waste stream is scrubbed to form an oxygen containing stream
US6210527A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Mar 14, 1994 |
| Grant date | Apr 3, 2001 |
| Priority date | — |
| Expiry date | Mar 14, 2014 |
Classification
- Technology area (CPC D)Textiles; Paper
- CPC primaryD21C9/147
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
A method for producing bleached wood pulp in which wood chips are digested in polysulfide liquor to produce brown stock pulp. The brown stock pulp is washed to produce washed brown stock wood pulp and weak black liquor and the washed wood pulp is then delignified in an oxygen delignification stage to produce oxygen delignified wood pulp. The delignified wood pulp is then ozone bleached in an ozone bleaching stage in which a waste stream principally containing ozone, carbon dioxide and oxygen is produced. The ozone-bleached pulp is introduced into an extractive oxidation stage which can include peroxide to further bleach the pulp and the product of the extractive oxidation stage is then either introduced into either a peroxide or chlorine dioxide bleaching stage. The waste stream is recovered and scrubbed with either white liquor, oxidized white liquor, or fully oxidized white liquor either in a separate scrubber or during oxidation reactions occurring in either polysulfide, white liquor or complete white liquor production stages. The scrubbing with white liquor or oxidized white liquor removes ozone and carbon dioxide so that the scrubbed stream can be utilized in the oxygen delign…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.