Method for measuring the basic amount in basic aluminum sulfate solution for removal of SO2 gas

Claim 1

A method for removing SO 2 from a waste gas comprising: (1) contacting the waste gas with a basic aluminum sulfate solution which absorbs the SO 2 from the gas; (2) subjecting the solution with the absorbed SO 2 gas therein to oxidation to convert any sulfite ion to sulfate; (3) returning a major portion (P 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 2 ); (5) returning solution (P 2 ) to the absorbing step; and controlling the amounts of basic aluminum sulfate at desired levels in solutions P 1 and P 2 by (a) obtaining samples of solutions P 1 and P 2 (b) measuring the temperatures T 1 and T 1' of the sample solutions P 1 and P 2 , respectively; (c) adding sulfuric acid to each of sample solutions P 1 and P 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 2 and T 2' of the mixtures; (d) determining the basic amount for each respective solution from the temperature differences T 1 and T 2 , and T 1' and T 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 1 and P 2 to the desired levels based on said determination.

Claim 2

A method for removing SO 2 from a waste gas comprising: (1) contacting the waste gas with a basic aluminum sulfate solution which absorbs the SO 2 from the gas; (2) subjecting the solution with the absorbed SO 2 gas therein to oxidation to convert any sulfite ion to sulfate; (3) returning a major portion (P 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 2 ); (5) returning solution (P 2 ) to the absorbing step; and controlling the amounts of basic aluminum sulfate at desired levels in solutions P 1 and P 2 by (a) obtaining samples of solutions P 1 and P 2 (b) measuring the temperatures T 1 and T 1' of the sample solutions P 1 and P 2 , respectively; (c) adding sulfuric acid to each of sample solutions P 1 and P 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 2 and T 2' of the mixtures; (d) determining the basic amount for each respective solution from the temperature differences T 1 and T 2 , and T 1' and T 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 1 and P 2 to the desired levels based on said determination.