Method for regenerating scale solvent
US5151196A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 27, 1991 |
| Grant date | Sep 29, 1992 |
| Priority date | — |
| Expiry date | Sep 27, 2011 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC09K8/528
- WIPO fieldBasic materials chemistry
- WIPO sectorChemistry
Abstract
Barium sulfate scale is dissolved by contacting the scale with an aqueous solvent having a pH of about 10 to about 14, preferably about 12, and comprising a chelating agent comprising a polyaminopolycarboxylic acid or salt of such an acid, and a synergist anion. The solvent containing the dissolved scale is regenerated by acidifying the spent solvent with an acidic chelating agent such as EDTA or DTPA, preferably DTPA, that release alkaline earth cations which react with sulfate ions present in the solvent to form a precipitate of an insoluble salt of the alkaline earth metal. The precipitate is then removed from the solvent by settling/decanting, filtering, or centrifuging. Thereafter, caustic is added to increase the pH of the solvent to a pH of about 10 to about 14, preferably about 12, to recover a regenerated solvent for reuse, in dissolving scale. The amount of chelating agent added to acidify the spent solvent balances the total amount of dilution caused by adding the caustic thereby maintaining the activity of the chelating agent in the regenerated solvent at least equivalent to or greater than the activity in the spent solvent.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.