Treatment of chemical pulp
US6514380B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Mar 26, 1998 |
| Grant date | Feb 4, 2003 |
| Priority date | — |
| Expiry date | Jan 17, 2019 |
Classification
- Technology area (CPC D)Textiles; Paper
- CPC primaryD21C9/02
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
Chemical pulp is produced by cooking comminuted cellulosic fibrous material (e.g. wood chips) in a continuous digester or batch digesters or produce brown stock, and washing the brown stock in a brown stock washer to produce chemical pulp, oxygen delignifying the chemical pulp at medium consistency, and then screening the oxygen delignified pulp to produce an accept fraction and a shive-containing reject fraction. Drawbacks inherent in the prior art are overcome by directly transporting (i.e. without refining or accessory oxygen delignification) the shive-containing rejects fraction to the main fiber line before oxygen delignification (e.g. to just before a mixer for the oxygen delignification stage, to between the brown stock washer and mixer, to a coarse screen between the digester and the brown stock washer, and/or to a washer for the coarse rejects from the coarse screen). The oxygen delignification stage may include at least two upflow vessels, of different first and second stages, with a mixer before each stage, and at least one of the vessels includes a multiple feeding device. Gas separation can also be practiced in one or all of the oxygen delignification vessels. The scre…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.