Boiler flue gas combined demercuration and dearsenification device and removing method thereof

The invention discloses a flue gas circulation fluidized bed combined demercuration and dearsenification device and a removing method thereof. The device comprises a coal economizer, a selective catalytic reduction denitrification device, an air preheater, a fluidized bed reactor, a bag type deduster, a desulfurization column and a chimney which are sequentially connected by a flue gas pipeline; a distributary flue gas pipeline and a main flue gas pipeline are arranged in parallel between the coal economizer and the fluidized bed reactor; the main flue gas pipeline is communicated to the bottom end opening of the fluidized bed reactor; the distributary flue gas pipeline is sequentially provided with a hydrogen bromide solution adding branch and an adsorbent adding branch from the coal economizer to the fluidized bed reactor; the tail end of the distributary flue gas pipeline is communicated with the lower part of the fluidized bed reactor via a flue gas spray nozzle; the flue gas spray nozzle is positioned above the bottom end opening of the fluidized bed; an adsorbent recycling mechanism is arranged below the bag type deduster. According to the invention, secondary pollution is not generated; mercury and arsenic removing efficiency is high; the pollution of mercury and arsenic generated by coal combustion flue gas to atmosphere can be prevented effectively.