NOVELTY - Flue gas treatment method involves supplying tail gas from absorption tower using blower, adjusting sulfur dioxide content to less than or equal to 30000 mg/Nm3; cooling with temperature-reducing spraying layer of ammonium sulfate solution in absorption tower provided with oxidizing section which releases oxidation desulfurization absorption liquid for removing sulfur dioxide. The absorption tower is provided with desulfurization spray containing liquid for absorbing ammonia into ammonia storage tank. The flue gas is washed with water and removing the fog drop in flue gas demister for purifying tail gas.    USE - For flue gas treatment for purifying tail gas in coal chemical industry; for removing the sulfur dioxide in the flue gas, useful in the field of agricultural fertilizer, environmental, electric power and chemical industry.    ADVANTAGE - The method has high efficiency, low investment cost, operation is simple and environment-friendly, can provide desulfurization efficiency of more than 99.5%, sulfur recycling rate about 95% and side product ammonium sulfate capable of direct sale.    DETAILED DESCRIPTION - Treating ammonia flue gas from acid tail gas, involves: by supplying a suitable condition, adjusting the tail gas sulfur dioxide content of the air to concentration of less than 30000mg/Nm3; providing the absorption tower with a process of water spraying and cooling with ammonium persulfate solution to reduce the temperature, and washing the tail gas, where process is improved when ammonium sulfate solution is used for spraying and cooling; providing the tower oxidation section with a oxidization distributor to release the oxidation desulfurization absorption liquid; the absorption tower is provided with a liquid distributor to release a desulfurization spray containing a solution of amine-containing absorption liquid for absorbing ammonia into the ammonia storage tank; a tower section on the upper part is provided with a water washing layer for removing fog drop content in flue gas demister for purifying the tail gas. An INDEPENDENT CLAIM is included for flue gas treating device comprising absorption tower (16), blower (2), ammonia water tank (3), absorption tower oxidation section, circulating pump (5), ammonium sulfate storage tank (6), ammonium sulfate discharging pump (7), smoke gas channel (8), the clean flue gas flue (9), chimney, sprayer (11), water washing layer (12), absorption tower spraying layer (13), cooling washing pump (14), inlet, cooling and washing spray layer (15), a spraying pump (17), a smoke flue connected with blower, absorption tower inlet set with ammonium sulfate solution spraying cooling device, absorbing tower is set in the oxidizing section provided with oxidization distributor to release the oxidation desulphurization absorption liquid, absorption tower is provided with a section provided with a liquid distributor to release desulfurization spray.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of flue gas treating device.    Blower (2)    Ammonia water tank (3)    Absorption tower (4)    Circulating pump (5)    Ammonium sulfate (6)    Ammonium sulfate storage tank discharging pump (7)    Smoke gas channel (8)    Smoke gas channel (9)    Chimney (10)    Sprayer (11)    Water washing layer (12)    Absorption tower spraying layer (13)    Washing pump (14)    Washing spray layer (15)    Absorption tower (16)    Cooling device (17)    Acid off-gas inlet (18)    Air (19)    Ammonia (20)    Water (21)