Study on the mechanism of thermal inertia action in circulating fluidized bed boiler☆

The Circulating Fluidized Bed (CFB) units accumulate a lot of heat during operation, forming the thermal inertia, which seriously constrains the improvement of the variable load rate. This study presents an innovative approach to characterizing thermal inertia through changes in heat storage capacity corresponding to unit power generation. An unsteady heat transfer calculation program was developed to evaluate the temperature distribution and heat transfer characteristics. The results indicate that the load change time was 1200 s in 75 %-100 % loadraising process. The thermal inertia of refractory material was 3 times that of the metal heating surface. The metal heating surface in areas without refractory material reached the new equilibrium state earlier than the working substance. Due to thermal inertia, the time for the working substance to reach its predetermined value was delayed by approximately 451 s. Furthermore, the thermal inertia caused load fluctuations even after the working substance parameter had reached the predetermined value. By calculating the energy transfer and temperature distribution, the specific influence and mechanism of thermal inertia in the variable load process were elucidated.