Device and method for separating sulfur trioxide in flue gas

The invention relates to a device and method for separating sulfur trioxide in flue gas, and the device comprises a flue gas sampling part which comprises a sampling pipe; a heating belt is sleeved outside the sampling tube; the sulfur trioxide separation part comprises a condenser, the condenser comprises a shell part, a spiral condensation pipe capable of being communicated with the sampling pipe is arranged in the shell part, and the spiral condensation pipe is used for condensing flue gas, separating and collecting sulfur trioxide; the inlet of the spiral condenser pipe is also connected with a deionized water supply part; the deionized water supply part is used for adding deionized water into the spiral condenser pipe so as to wash out acid mist; the shell part is circularly communicated with a constant-temperature circulating water tank; an outlet of the spiral condensation pipe is communicated with a liquid discharging pipe; the tail gas treatment part comprises a gas washing bottle and a drying pipe,