When coal-fired boiler units participate in deep peak shaving

the water wall temperature and the characteristics of the working fluid in the tube are crucial for the safe and stable operation of the boiler under low load. Therefore

this paper uses bidirectional iteration strategies based on Fluent and user-defined functions (UDFs) to conduct a coupled simulation of combustion and steam-water side in a 1 000 MW double tangential-fired boiler under low load. This study explores the influence of air distribution mode and coal mill combination mode on the heat flux

working fluid temperature

heat transfer coefficient

and water wall temperature. The results indicate that the simulated values of the oxygen content

carbon content in fly ash

water-wall temperature

and working fluid temperature are consistent with the on-site measurement

and the coupled simulation results are reliable. The carbon content in fly ash is the lowest with waist reduction and equal air distribution methods. With inverted tower air distribution

the outlet temperature of the working fluid in the tube is the highest

followed by the main tower and the waist contraction

while the equal is the lowest. The water wall temperature gradually increases along the height with equal and waist-reduced air distribution. In contrast

the temperature of the lower wall with inverted tower air distribution is higher

and the range of high-temperature zones is wider. When ABC or BCD mills are applied

the temperature distribution inside the furnace is relatively uniform

and the carbon content in fly ash is relatively low (ABC: 1.03%

BCD: 1.26%). Under the ABC mills

the temperature of the working fluid inside the tube increases the fastest and reaches the highest

while under the DEF mills

the temperature of the working fluid inside the pipe increases most slowly and reaches the lowest maxinum. The wall temperature of the DEF mills is significantly reduced compared to the combination of ABC mills and BCD mills. The studied results can provide practical guidance for low-load

efficient

safe

and stable operation of boilers.