Abstract: Wet desulphurization device is widely applied in coal fired power plant in the context of ultra low emission.The saturated wet flue gas emitted from the device outlet usually form wet plume at the chimney outlet,resulting in adverse effects on ecological environment and human health.In this paper,the state of flue gas and ambient air were calculated to determine the critical temperature of wet plume removal and the equivalent ratio of mixed air,and the applicable environmental conditions and technical parameters of different flue gas blanking technology routes were compared based on the tangential method.The result shows that the wet plume is more difficult to be eliminated with lower environment temperature and higher relative humidity.If the relative humidity is 60% and the flue gas temperature at the outlet of the wet desulphurization tower is 50 ℃,the critical temperature of 37.3 ℃ for wet plume elimination can be realized without any measures.So the flue gas parameters of the wet desulfurization unit should be adjusted for wet plume elimination under ordinary environment conditions.Assuming that the maximum cooling amplitude of applicable flue gas is 30 ℃ and the maximum warming amplitude is 30 ℃,the critical environment temperature of smoke plume elimination is 12.9 ℃ only by flue gas heating technology,while the critical environment temperature of smoke plume elimination is 8. 7 ℃ only by flue gas condensation technology and the critical environment temperature of smoke plume elimination is -12.9 ℃ by both flue gas condensation and heating technology.For air heating mixing technology,the heat balance of the air and flue gas mixing process was calculated to determine the critical air equivalent ratio of wet plume elimination based on the tangent method.The combination of flue gas heating,flue gas condensation and air heating technology can enlarge the applicable environmental conditions of wet flue gas plume elimination.