PURPOSE: To remove copper efficiently and prevent occurrence of trouble in wet oxidation process, ammonium sulfate production process, etc., by heating the absorption liquid when removing NOX and SOX contained in waste gas simultaneously, by using the absorption liquid containing copper compound in aqueous solution of thiosulfate.
CONSTITUTION: NOX and SOX are removed from the waste gas, by using aqueous solution of thiosulfate, such as coke oven gas desulfurization waste liquid, containing copper compound, e.g. cupric sulfate, cupric chloride, by usually 100W500ppm approximately as Cu. Afterwards, the absorption liquid is heated to 100W200°C, preferably 150W200°C to decompose thiosulfate, thereby producing H2S. As a result, the copper occurring in the form of copper-thiosulfate complex is transformed into sulfide, which is then settled and removed. The reaction time is, when heated to 150°C, 20W60 minutes. The separated copper sulfide may be, when oxidized with oxidizing agent such as hydrogen peroxide, may be recovered as copper sulfate to be re-used.
WAKABAYASHI ATARU
YOKOTA KUNIHIKO
SATOU HIROSHI
SHIGA KAZUYUKI
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