Liquid purification or separation – Processes – Making an insoluble substance or accreting suspended...
Patent
1991-09-27
1992-09-29
Silverman, Stanley S.
Liquid purification or separation
Processes
Making an insoluble substance or accreting suspended...
210724, 134 13, 134 2214, 134 2219, 252 82, 252 86, C02F 162
Patent
active
051511967
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.
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Morris Richard L.
Paul James M.
McCarthy Neil M.
McKillop Alexander J.
Miller Lawrence O.
Mobil Oil Corporation
Silverman Stanley S.
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