Claims
- 1. A method for removing SO.sub.2 from a waste gas comprising:
- (1) contacting the waste gas with a basic aluminum sulfate solution which absorbs the SO.sub.2 from the gas;
- (2) subjecting the solution with the absorbed SO.sub.2 gas therein to oxidation to convert any sulfite ion to sulfate;
- (3) returning a major portion (P.sub.1) of the oxidized solution to the absorbing step;
- (4) neutralizing the remainder of the oxidized solution with calcium carbonate or calcium hydroxide to precipitate gypsum which is separated to produce solution (P.sub.2);
- (5) returning solution (P.sub.2) to the absorbing step; and controlling the amounts of basic aluminum sulfate at desired levels in solutions P.sub.1 and P.sub.2 by
- (a) obtaining samples of solutions P.sub.1 and P.sub.2
- (b) measuring the temperatures T.sub.1 and T.sub.1' of the sample solutions P.sub.1 and P.sub.2, respectively;
- (c) adding sulfuric acid to each of sample solutions P.sub.1 and P.sub.2 in amounts at least equivalent, on a stoichiometric basis to the estimated basic amount in each solution and immediately measuring the respective temperatures T.sub.2 and T.sub.2' of the mixtures;
- (d) determining the basic amount for each respective solution from the temperature differences T.sub.1 and T.sub.2, and T.sub.1' and T.sub.2' from a predetermined calibration curve of the linear relationship of temperature difference and basic amount; and
- (e) adjusting the basic amounts in solutions P.sub.1 and P.sub.2 to the desired levels based on said determination.
- 2. The method of claim 1 in which the basic amount thus determined is related to basicity of solutions P.sub.1 and P.sub.2 by the expression ##EQU3## and the basicity of solution P.sub.1 is kept at not less than about 5% and the basicity of solution P.sub.2 is kept at not more than about 40%.
- 3. The method of claim 1 or 2 wherein an electric current is generated in dependence on the respective temperature differences, the electric current being related to a predetermined calibration and determining said basic amount therefrom.
- 4. The method of claim 1 or 2 wherein the sulfuric acid concentration is between about 3 to 8 N.
- 5. The method of claim 1 or 2 wherein the sulfuric acid concentration is between about 4 to 5 N.
Priority Claims (1)
Number |
Date |
Country |
Kind |
51-108990 |
Sep 1976 |
JPX |
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Parent Case Info
This is a continuation-in-part of U.S. patent application Ser. No. 831,124, filed Sept. 7, 1977, now abandoned, the contents of which are incorporated herein by reference.
US Referenced Citations (7)
Continuation in Parts (1)
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Number |
Date |
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Parent |
831124 |
Sep 1977 |
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