Elemental-chlorine-free bleaching process having an initial Eo or Eop stage
US6569284B1 · kind B1 · utility
Assignee
Inventors
Key dates
| Filing date | Jul 1, 1998 |
| Grant date | May 27, 2003 |
| Priority date | — |
| Expiry date | Jan 15, 2021 |
Classification
- Technology area (CPC D)Textiles; Paper
- CPC primaryD21C9/144
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
The specification discloses an improved bleaching sequence which provides significant reduction in filtrate volumes and amounts of absorbable organic halide (AOX), color, and chemical oxygen demand (COD) in the effluent. These reductions are achieved without adversely affecting the brightness and viscosity properties of the bleached pulp and without a high capital cost and operating cost penalty or impact on existing mill processes. The bleaching sequence according to the invention for reducing filtrate volumes is an EOD1EOPD2 or EOPD1EOPD2 bleaching sequence wherein substantially all of the filtrates from the later bleaching stages are recycled to earlier bleaching stages and eventually treated in the initial EO or EOP stage prior to discharge from the plant. An advantage of the invention is that pulp having a Kappa number of greater than about 25 for softwood and greater than about 15 for hardwood may be fed to the bleaching process while still providing a bleached pulp having sufficient brightness, viscosity characteristics and good pulp yield.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.