Introduction  The white fog is often appeared and causes "visual pollution" if the exhaust gas after wet desulphurization is not controlled.

  Method  The white fog phenomenon from the exhaust gas after wet desulphurization was studied theoretically, and the thermal process of the white fog was analyzed with the help of the flue gas thermal characteristic curve equation and "temperature-humidity" chart, so a new scheme of the white fog treatment for cooling, dehumidification and heating was presented. Combined with a typical 1 000 MW ultra-supercritical coal-fired unit, the energy-saving effects of the new scheme were calculated.

  Results  The results show that: based on certain boundary conditions of the project and design principles, the saturated gas heating power of the new scheme is decreased by 10.511 6 MW, in two cases that the flue gas waste heat is used to heating condensate water or is not used to heating condensate water, the unit efficiency is increased by 0.231% and 0.164% than the general scheme respectively.

  Conclusion  A new scheme of the white fog treatment can achieve the same effect of the white fog treatment and that has better energy-saving effects.