Acid treatment of pulp at high temperature prior to chlorine dioxide bleaching
US6306253A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Apr 14, 1998 |
| Grant date | Oct 23, 2001 |
| Priority date | — |
| Expiry date | Apr 14, 2018 |
Classification
- Technology area (CPC D)Textiles; Paper
- CPC primaryD21C9/1026
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
In the treatment of cellulose pulp in connection with bleaching, the pulp is first cooked and, if necessary, oxygen delignified in order to reduce the Kappa number below 24, preferably below 14, and after that the pulp is treated in an acid stage at a pH of 2-5 and at a temperature range of 75-130.degree. C. in order to reduce the Kappa number by 2-9 units. To prevent essential weakening of the strength properties of the pulp in the acid stage treatment tower, the retention time, t min, is 30 to 300 minutes and the treatment temperature, T.degree. C. is T.sub.min <T<T.sub.max, in which ##EQU1## and EQU T.sub.max =T.sub.min+23.degree. C.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.