The invention relates to an exhaust gas separating tower, comprising a washing section, a flash-distilling section above the washing section, and a liquid seal means between the flash flash-distilling section and the washing section. The washing section is configured for washing exhaust gas entering the tower with a cooling liquid to at least partially remove solid dust entrained in the exhaust gas, cool the exhaust gas, and condense at least a portion of moisture in the exhaust gas into liquid. The flash-distilling section is configured for flash-distilling the cooling liquid from the washing section to produce a cooled cooling liquid and a cooling liquid vapor. The liquid seal means is configured so that the cooling liquid produced by flash-distillation can enter the washing section through the liquid seal means while the flash-distilling section is in gas-phase isolation from the washing section, wherein a pressure in the flash-distilling section is lower than that in the washing section.