Method and apparatus for removing sodium chloride from pulping chemicals using an amphoteric ion-exchange resin
US5922171A · kind A · utility
Assignees
Inventors
Key dates
| Filing date | Jan 24, 1997 |
| Grant date | Jul 13, 1999 |
| Priority date | — |
| Expiry date | Jan 24, 2017 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY02P40/40
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
Sodium chloride is removed from pulping chemicals used in a Kraft pulping process by the use of a snake-cage polyelectrolyte ion exchange resin, coupled with removal of sulfide prior to treatment, or treatment of chemicals which are already low in sulfide. In one aspect of the invention, dust is collected from exhaust gases produced in the black liquor recovery cycle and is dissolved in water to produce a solution containing sodium chloride and sodium sulfate. The solution is filtered to yield a solid product and a filtrate solution. The filtrate solution is fed to an ion exchange unit which removes chloride and produces a purified sodium sulfate product. The sodium chloride is removed from the ion exchange resin by water elution, and useful recovered chemicals are recycled to the recovery cycle of the Kraft process. In one embodiment, only a portion of the dust is dissolved so that the solid product produced by filtering is primarily sodium sulfate, and that sodium sulfate is recycled to the recovery cycle of the Kraft process. In another aspect of the invention, white liquor from the pulping process is treated directly after oxidizing sulfide to sulfate. After removal of sodium c…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.