To solve the problem of full load instantaneous fire extinguishing of an ultra supercritical 1 000 MW unit boiler

through data recovery and tracking analysis of the combustion conditions

the water level of wet slag catching seal and the elevation settlement of the seal baffle of the boiler full load ash hopper before and after the time point of boiler fire extinguishing

it is found that

the main cause of boiler full load instantaneous fire extinguishing and unit trip is that

poor combustion conditions made the coke block formed by some unburned pulverized coal fell directly into the furnace bottom water seal

which increased the content of solid particles in the seal water

so the liquid level measuring element with design defects was buried. With distorted signal

normal interlock water supply could not be ensured

resulting a damage of the water seal at the furnace bottom. In this regard

by adjusting the fineness of pulverized coal into the furnace

improving the bottom structure of the measuring barrel of the liquid level measuring element of the slag extractor

and optimizing the judgment conditions of the water supplement program

the safety risk caused by the damage of the water seal at the bottom of the boiler was effectively prevented. This result can provide reference for the boiler units with the same type of wet slag extractor.