As one of the commonly used steam temperature regulating methods

the flue gas recirculation can cause an obvious change of the heat load distribution

which will finally affect the thermal hydrodynamic of water in the water wall. Based on the boiler thermal calculation method

numerical simulation of the combustion and the hydrodynamic calculation of water wall

the influences of flow rate of the recirculated flue gas and extraction position of the flue gas on thermal hydrodynamic and water wall temperature distribution were analyzed. The results show that

due to the fuel gas recirculation

both the minus mass flow characteristics and the mass flow rate difference between pipes became faint. With the flow rate of recirculated flue gas increasing

the water wall temperature decreased

while the temperature difference between pipes also declined. Compared with using the flue gas extracted from the electrostatic precipitator outlet

the changing amplitudes of both mass flow rate distribution and water wall temperature distribution were smaller when the the recirculated flue gas was extracted from the economizer outlet. The present research and relevant results can provide guidance for the thermal hydrodynamic design and improvement of an ultra-supercritical unit boiler with double-reheat cycle and flue gas recirculation.