Method for improving mercury removal efficiency of flue gas desulphurization system

The invention provides a method for improving mercury removal efficiency of a flue gas desulphurization system. According to method, a desulphurization and mercury-removing additive composed of, by mass, 30 to 40% of sodium formate and 60 to 70% of calcium hypochlorite is added into desulphurization absorption slurry. The method comprises the following steps: preparing a desulphurization and mercury-removing additive uniform liquid with a concentration of 20 to 30% from sodium formate and calcium hypochlorite in a ground pit or filtrate pit of a flue gas desulfurization tower; pumping the uniform liquid into the desulfurization tower by using a ground pit pump or filtrate pump; and increasing air quantity of an oxidation fan so as to improve oxidation effect. According to method, the desulphurization and mercury-removing additive is applied to flue gas desulphurization, and the additive can effectively accelerate desulphurization reaction speed, reduce limestone content in gypsum, promote oxidation of elemental mercury in flue gas into oxidized mercury, inhibit reduction of oxidized mercury in the slurry and improve efficiency of the desulphurization system in removing sulfur dioxide and mercury in flue gas.