Process for digesting and bleaching cellulosic material with reduced emissions
US4329199A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Dec 7, 1979 |
| Grant date | May 11, 1982 |
| Priority date | — |
| Expiry date | Dec 7, 1999 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S423/03
- WIPO fieldChemical engineering
- WIPO sectorChemistry
Abstract
The digestion of the cellulose-containing material is performed with a digestion liquor containing sulphur and sodium followed by recovery and regeneration of said digestion liquor and bleaching of the cellulose-containing material with chlorine dioxide. The SO.sub.2 -containing and possibly chloride-containing gas from the recovery boiler (11) of the process and from combustion of evil-smelling gases (20) is absorbed in an absorption liquor containing and alkali metal salt solution free of sulphur or sulphur compounds such as sulphide or thiosulphate, in a scrubber (27). The resulting scrubber liquor is mixed with acid residual solution (26) from the manufacture of chlorine dioxide, whereby sulphur dioxide (32) in gaseous state is returned to the process, whereafter the residual solution (34) free from SO.sub.2 is led to an evaporation and crystallization plant (35) for precipitation of alkali salts except chloride, substantially sodium sulphate, for obtaining a residual acid (37) consisting of chloride-containing sulphuric acid. The chloride-containing sulphuric acid is returned to the manufacture (19) of chlorine dioxide for generation chlorine dioxide, whereby the chloride cont…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.