Low-load and even ultra-low-load peaking operation has been the operating trend of supercritical circulating fluidized bed boilers. The water-cooled wall thermal deviation

heat transfer deterioration and other problems accompanying the operation under low load conditions aggravate the super-temperature creep damage of the tube wall

which affects its operation life. This paper takes an in-service supercritical circulating fluidized bed boiler as the research object

combines the actual operation data

constructs the simulation model of its temperature field and stress field

explores the distribution law of the temperature

deformation and thermal stress of the tube wall under the low load condition

normal heat transfer

heat transfer deterioration

and different thermal deviation

and evaluates the creep life of the water-cooled wall tubes under different temperatures and stress levels. The results show that when heat transfer deterioration occurs

the maximum temperature of the water-cooled wall tube shifts to the midpoint of the tube wall on the fireward side

and the maximum thermal stress still occurs at the contact point between the tube wall and the fins on the backward side; when the temperature deviation is more than 50℃

the maximum temperature

the maximum deformation

and the maximum thermal stress of the reference tube increase abruptly; and when the heat transfer deterioration occurs

the wall temperature of the tube wall at the danger point reaches 535℃

and the thermal stress reaches 258 MPa

which is close to the life limit of the water-cooled wall tube

so strict temperature control of the water-cooled wall should be prioritized. The results of the study provide a certain reference for the safe operation of supercritical circulating fluidized bed boilers at low load.