US 4,828,660 A · Method and apparatus for the continuous on-site chemical reprocessing of ultrapure liquids

Abstract

A continuous process and apparatus for the repurification of ultrapure liquids. An oxidant solution comprising ultrapure sulfuric acid, peroxydisulfuric acid, and ultrapure water is continuously withdrawn from a process after use. The withdrawn oxidant is reprocessed continuously by contacting with alumina to remove fluoride ions. Water is continuously separated or stripped from the oxidant solution by heating the solution and bubbling an inert gas therethrough causing the water to vaporize from the solution. The separated oxidant is continuously distilled and condensed to form a purified stream of sulfuric acid. The major portion of this stream is continuously returned to the process. The remaining minor portion is continuously cooled, subjected to analysis for purity, and diluted with ultrapure water. The diluted sulfuric acid is further cooled prior to electrochemical treatment in the anode compartment of an electrochemical cell. This converts at least a portion of the dilute sulfuric acid to peroxydisulfuric acid. The resulting solution is continuously returned to the process to be mixed with the major portion of the purified sulfuric acid. A system of apparatus to conduct the processes is provided which also includes means for continuously analyzing the minor portion for purity and trace elements.

Claims35

Dependent claims

A process for the regeneration and repurification of ultrapure oxidant solution comprising ultrapure sulfuric acid, ultrapure peroxydisulfuric acid, and ultrapure water which is used in a chemical process utilizing said ultrapure oxidant solution comprising:

withdrawing at least a portion of said oxidant solution used in said chemical process;
distilling said withdrawn oxidant solution to remove particles and dissolved impurities to form ultrapurified sulfuric acid;
dividing said ultrapurified sulfuric acid into a major portion and a minor portion;
returning said major portion of said ultrapurified sulfuric acid to said chemical process;
diluting said remaining minor portion of said ultrapurified sulfuric acid with ultrapure water to produce a stream of diluted ultrapure sulfuric acid;
introducing said diluted ultrapure sulfuric acid into the anode compartment of an electrochemical cell where at least a portion of said diluted ultrapure sulfuric acid is converted into ultrapure peroxydisulfuric acid;
adding at least a portion of said resulting solution of ultrapure sulfuric acid, ultrapure peroxydisulfuric acid, and ultrapure water to said chemical process where it is admixed with said major portion of said ultrapure sulfuric acid to reform said ultrapure oxidant solution.

4 more elements

A system for the chemical repurification and regeneration of an ultrapure oxidant solution comprised of ultrapure sulfuric acid, ultrapure peroxydisulfuric acid, and ultrapure water used in a chemical process at a process center comprising:

means for removing oxidant solution from said process center;
means for removing fluoride ions from said oxidant solution;
means for separating sulfuric acid from water contained in said oxidant solution;
means for distilling to remove particles and dissolved impurities and condensing said sulfuric acid into a continuous stream of ultrapure condensed sulfuric acid;
means for dividing said condensed ultrapure acid stream into two streams comprising a major portion and a minor portion;
means for conducting said major portion of said ultrapure condensed sulfuric acid stream to said chemical process center;
means for diluting said minor portion of said stream of condensed purified acid with ultrapure water to form an ultrapure acid/water solution;
means for metering and conducting said minor portion of said ultrapure condensed acid stream to said diluting means;
at least one electrochemical cell having an anode compartment and a cathode compartment;
means for conducting said ultrapure acid/water solution from said diluting means to said anode compartment of said electrochemical cell;
a source of electrical power for said electrochemical cell;
and,
means for conducting said acid/water solution from the anode compartment of said electrochemical cell after reaction therein to produce a solution containing ultrapure sulfuric acid, ultrapure peroxydisulfuric acid, and ultrapure water to said chemical process center for admixture with said major portion of said ultrapure condensed sulfuric acid stream.

10 more elements

Dependencies are inferred from the claim text.

Method and apparatus for the continuous on-site chemical reprocessing of ultrapure liquids

Life of this patent

Method and apparatus for the continuous on-site chemical reprocessing of ultrapure liquids

Life of this patent

Abstract

Claims35