With the continuously increasing proportion of installed capacity from new energy sources

higher flexibility demands are imposed on coal-fired power generation units

including supercritical circulating fluidized bed(CFB) boilers. By taking a 350 MW supercritical CFB boiler as the research object

the computational particle fluid dynamics(CPFD) method was employed to simulate the furnace response characteristics under variable load conditions

focusing on parameters such as furnace temperature

near-wall particle concentration

and average heat flux density on heating surfaces. The effects of combustion and circulation interventions on the rate of load change were also explored. The results indicate that

during load ramp-up operation

the response rate of average heat flux density in low load range(30%～50% of the unit rated load) decreases by about 38% compared with that in high load range(above 50% of the rated load). Focusing only on the high load range

the heat flux density responds faster during load ramp-down

with the rate of change about 31% higher than that during ramp-up. Under varying load amplitudes

the particle suspension concentration and convective heat transfer intensity inside the furnace can respond rapidly

while temperature changes lag slightly

indicating that CFB boilers rely more on variations in the heat transfer coefficient for rapid thermal regulation. Through combustion interventions

such as substituting 40% of the original coal feedstock with fine coal particles sized several hundred microns

the change in furnace temperature can be effectively accelerated

with the response rate of average heat flux density during ramp-up in the high load range increasing by about 43%

and by nearly 16% in the low load range. Additionally

implementing circulation interventions

such as adding a certain amount of fine bed material during ramp-up

can rapidly increase the particle suspension concentration in a short time and thus effectively improve the response rate of the heat transfer coefficient on the heating surface. If hot fine material is further added(for example

through a hot circulating ash storage and return system)

the response rate of the average heat flux density during ramp-up in the high load range can be improved by approximately 31%

and by about 13% in the low load range. The study elucidates the internal response mechanisms of CFB boilers under variable loading conditions

confirms the feasibility of improving load change rates through circulation and combustion interventions

and provides a reference for further tapping the flexibility potential of supercritical CFB boilers and improving their variable load capability.