Inhibiting scaling in alkaline waste liquor evaporators
US6235151A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 26, 1999 |
| Grant date | May 22, 2001 |
| Priority date | — |
| Expiry date | Apr 26, 2019 |
Classification
- Technology area (CPC D)Textiles; Paper
- CPC primaryD21C11/106
- WIPO fieldTextile and paper machines
- WIPO sectorMechanical engineering
Abstract
Calcium carbonate scaling is inhibited in a multi-stage alkaline waste liquor evaporation plant in a chemical cellulose pulp mill having a bleaching plant. Calcium-containing effluent from the bleaching plant is treated together with alkaline waste liquor in the evaporation plant. A portion of the alkaline waste liquor of the evaporation plant is supplied to the bleaching effluent to increase the carbonate content of the effluent. Then the bleaching effluent is heated to 110-160.degree. C. by direct contact with a heating medium (e.g. steam, or secondary vapor) and maintained in a retention tank for a period of about 1-20 minutes to reduce the amount of dissolved calcium in the effluent. Finally the heat-treated bleaching effluent is evaporated with the alkaline waste liquor in the evaporation plant, with minimized scaling.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.