The present invention provides a method for purifying a
flue gas absorbent, the
flue gas absorbent is an organic amine
aqueous solution with a pH of 4.0 to 6.0, the organic amine is a mixture of one or two of 4,4'-(1,2-
ethylene)bismorpholine or 4,4'-(oxybis(
methylene))dimorpholine, wherein the
sulfate mass fraction is 12% to 25%; the method includes: adding a heat-stable salt purifier to the
flue gas absorbent, controlling the temperature of the
mixed solution at 5 to 40 ° C during the addition, and stirring sufficiently; controlling the final pH of the
mixed solution to be 10 to 13, obtaining a purified absorbent and
solid potassium sulfate precipitation; the heat-stable salt purifier, by
mass percentage, contains 30 to 100% of the main component and the remainder of water; the main component is a mixture of one or more of
potassium carbonate,
potassium bicarbonate,
potassium hydroxide or
potassium sulfite. The method of the present invention has a good removal effect for
sulfate in an organic amine
flue gas absorbent of a specific component, and no waste water is generated, and the
upgrade of a
flue gas absorbent purification device to reduce costs and increase efficiency can be achieved.