Flue protecting device of solid slag pulverized coal boiler

The utility model discloses a flue protecting device of a solid slag pulverized coal boiler. A smoke humidity detector (2) is arranged at a smoke outlet of the solid slag pulverized coal boiler (1); the smoke humidity detector (2) is electrically connected with a DCS (distributed control system) (3); the DCS (3) is electrically connected with a draught fan (4); the draught fan (4) is electrically connected with a desulphurization system (5); and an air inlet of the draught fan is connected with the smoke outlet of the solid slag pulverized coal boiler (1) through a flue and an air outlet is connected with a chimney (6) through the flue. By providing the smoke humidity detector at the smoke outlet of the solid slag pulverized coal boiler, the signal measured by the smoke humidity detector enters the DCS, and the DCS regards the measured value as an auxiliary control parameter of air quantity control of the fan, and controls the air quantity to achieve the purpose of controlling the moisture content of the smok