Desulfurization is mainly to remove sulfur dioxide in flue gas, and denitrification is mainly to reduce nitrogen oxides in flue gas. Desulfurization generally uses limestone-lime-gypsum method, and denitration generally uses catalyst oxygen reduction to convert nitrogen oxides into nitrogen for emission. The desulfurization and denitrification fan is a forced ventilation system when the desulfurization and denitration system is working. Its compact structure, high operating efficiency and high pressure are very well matched with the current desulfurization and denitration system for gas sealing.