Oxygen delignification method incorporating wood pulp mixing apparatus
US5460696A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 12, 1993 |
| Grant date | Oct 24, 1995 |
| Priority date | — |
| Expiry date | Aug 12, 2013 |
Classification
- Technology area (CPC D)Textiles; Paper
- CPC primaryD21C9/147
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
An oxygen delignification method and apparatus in which a charge of heated wood pulp is reacted with oxygen in the presence of a charge of caustic soda in a plurality of reaction stages located between mixing stages in which caustic is mixed with the wood pulp. The use of the plurality of mixing stages reduces peak pH exposure of the wood pulp that would otherwise occur if the charges of caustic and wood pulp were mixed all at once. Moreover, the caustic mixed in such manner replenishes neutralized caustic and ensures that the average pH level is increased above that in conventional oxygen delignification. The increase in average pH level favors an increase in the delignification. Filtrate from a washing stage is introduced into the mixing stages to prevent wood pulp degradation. Oxygen is mixed within the wood pulp by a wood pulp mixer that employs coaxial perforate passageways between which the wood pulp is retained and driven but which allow the oxygen to pass in an inward radial direction of the passageways to mix with the wood pulp.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.