Fluoride removal from sulphuric acid
AssigneeChemetics International Company Ltd.
InventorsLynda G. Sturgeoff, Graeme W. Norval, Frederick S. Przystal, Andrew E. Yethon
Life of this patent
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Abstract
A process for the reduction in fluoride concentration in a fluoride-contaminated sulphuric acid which process comprises treating said sulphuric acid with a silicon compound to produce silicon tetrafluoride, and removing said silicon tetrafluoride to produce a purer sulphuric acid having a substantially reduced fluoride concentration. The process is of particular use for the removal of fluoride from waste sulphuric acid in the copper smelting industry to meet environmental concerns.
Claims14
A process for the reduction of fluoride concentration in a waste sulphuric acid, which acid is contaminated with hydrogen fluoride and heavy metal salts, which process comprises:
- a) establishing a first circulating sulphuric acid loop at a temperature between about 20.degree. C. and the boiling temperature of said first circulating sulphuric acid;
- b) adding said waste sulphuric acid to said first circulating sulphuric acid;
- c) adding silica to said first circulating sulphuric acid circulation loop to convert at least a portion of said hydrogen fluoride to silicon tetrafluoride;
- d) removing a portion of said first circulating sulphuric acid and spray drying said portion to produce a gaseous stream comprising hydrogen fluoride, sulphur trioxide, sulphuric acid, silica, silicon tetrafluoride and heavy metal salts, at a temperature sufficient to ensure complete drying of said portion and which minimizes decomposition of sulphur trioxide to sulphur dioxide;
- e) separating the solid components from the gaseous stream;
- f) contacting said gaseous stream with a second circulating sulphuric acid loop to absorb at least a portion of said sulphur trioxide into said second circulating sulphuric acid to generate additional sulphuric acid in said second circulating acid and produce a second gaseous stream containing at least one of unabsorbed sulphur trioxide, sulphuric acid, unreacted hydrogen fluoride and silicon tetrafluoride, said second circulating sulphuric acid being at a temperature between about 20.degree. C. and the boiling temperature of said second circulating sulphuric acid, and said second circulating acid containing said additional sulphuric acid having an acid concentration of at least about 50%;
- g) adding silica to said second circulating sulphuric acid to convert at least a portion of said hydrogen fluoride to silicon tetrafluoride;
- h) removing a portion of said second circulating sulphuric acid as product;
- i) contacting said second gaseous stream with said first circulating sulphuric acid to absorb said unabsorbed sulphur trioxide into said first circulating sulphuric acid to generate second additional sulphuric acid in said first circulating acid and react at least a portion of said unreacted hydrogen fluoride with said silica in said first circulating sulphuric acid to produce silicon tetrafluoride, and said first circulating acid containing said second additional sulphuric acid having an acid concentration of at least about 45%;
- j) removing said silicon tetrafluoride.
A process for the reduction of fluoride concentration in a waste sulphuric acid, which acid is contaminated with fluoride and heavy metal salts, which process comprises:
- a) establishing a circulating sulphuric acid loop at a temperature between about 20.degree. C. and a boiling temperature of said circulating sulphuric acid;
- b) vaporizing said waste sulphuric acid to produce a gaseous stream comprising hydrogen fluoride, sulphur trioxide and sulphuric acid, and heavy metal particulates, at a temperature sufficient to ensure complete vaporization of said waste sulphuric acid and which minimizes decomposition of sulphur trioxide to sulphur dioxide;
- c) removing said particulates;
- d) contacting said gaseous stream with said circulating sulphuric acid to absorb said sulphur trioxide into said circulating sulphuric acid to generate additional sulphuric acid in said sulphuric acid loop, and said circulating sulphuric acid containing said additional sulphuric acid having an acid concentration of at least about 45%;
- e) adding silica to said circulating sulphuric acid to convert at least a portion of said hydrogen fluoride to silicon tetrafluoride;
- f) removing said silicon tetrafluoride from said circulating sulphuric acid;
- and
- g) removing a portion of said circulating sulphuric acid as product.
Dependencies are inferred from the claim text.