System using boiler sewage of thermal power plant as desulfurization water

A system using boiler sewage of a thermal power plant as desulfurization water comprises a boiler drum, a continuous blowdown flash tank, a water-water heat exchanger, a desulfurization process water tank, a desulfurization tower, a first pipeline, a second pipeline, a third pipeline and a fourth pipeline. One end of the first pipeline is connected with the drain outlet end of the boiler drum, the other end of the first pipeline is connected with the inlet end of the continuous blowdown flash tank, and a first valve is arranged on the first pipeline; one end of the second pipeline is connected with the outlet end of the continuous blowdown flash tank, the other end of the second pipeline is connected with the inlet end of the water-water heat exchanger, and a second valve is arranged on the second pipeline; the discharged sewage is used as water for a desulfurization process, so that the problem that the use amount of a desulfurizing agent and the water for the desulfurization process in desulfurization opera