Two-stage kraft cooking
US5522958A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jul 18, 1994 |
| Grant date | Jun 4, 1996 |
| Priority date | — |
| Expiry date | Jul 18, 2014 |
Classification
- Technology area (CPC D)Textiles; Paper
- CPC primaryD21C3/26
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
A method for the production of kraft pulps in a digester, by modifying the cooking chemical concentration, and lignin concentration profiles during the cook, has provided extended delignification and improved selectivity in a simpler way than has previously been possible. The cooking is performed at an elevated temperature in two stages. The first stage liquor is a mixture of 1) the spent liquor of the second stage and 2) a portion of the conventional charge of fresh cooking chemicals needed for the complete cook. The second stage liquor is made up by adding an aqueous diluent, for example, fresh water or washing filtrate to the remaining portion of the fresh cooking chemicals.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.