Recovery of NaOH and other values from spent liquors and bleach plant effluents
US5061343A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | May 30, 1990 |
| Grant date | Oct 29, 1991 |
| Priority date | — |
| Expiry date | May 30, 2010 |
Classification
- Technology area (CPC D)Textiles; Paper
- CPC primaryD21C11/0042
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
Oxidized weak black liquor or effluents from alkaline bleaching stages, particularly oxygen delignification and/or ozone and/or hydrogen peroxide bleaching effluents are treated in process stages which include an electrolytic cell to recover NaOH, lignin, O.sub.2, H.sub.2 and to achieve other important benefits, the most important of these are (i) to unload the evaporator-recovery furnace and lime-kiln causticizing plant, and (ii) to enable a mill to implement low- or no-chlorine bleaching techniques without overloading their recovery furnace and/or lime kiln or requiring a new, larger recovery system, the electrolytic treatment can be carried out with one or a combination of the above types of effluents; it is also possible to increase the conductivity if required and thus the efficiency of the electrolytic cells and the yield/production of NaOH by the introduction of Na.sub.2 SO.sub.4 (make-up or recycle from recovery furnace) and/or NaCl into the feed to the process; the process involves pre-acidification of aqueous alkaline liquid containing lignin to initiate precipitation of lignin, feeding the partly acidified liquid to the anolyte compartment of an electrolysis cell in whic…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.