As the capacity of circulating fluidized bed(CFB) boiler increases

the number of separators increases accordingly

and the structure of parallel arrangement of multiple separators will result in uneven gas-solid distribution and bias flow phenomenon

which brings great harm to the boiler. To investigate the effects of different operating parameters on the bias flow phenomenon

an Eulerian two-fluid model was used to carry out numerical simulation on the gas-solid flow characteristics of high efficiency ultra supercritical CFB boiler with four separators arranged in M type. The effects of air distribution uniformity

average particle size and volume ratio of primary air to secondary air on the gas-solid distribution uniformity among multiple separators were discussed in detail.Compared with bed stock and the primary and secondary air ratio

the uniformity of air distribution had the greatest influence on the gas-solid flow rate distribution between the four circulation loops. Therefore

ensuring the distribution uniformity of air distribution is the main measure to solve the gas-solid bias flow. Moreover

the nonuniformity of gas-solid distribution in the four separators increases at first and then decreases with the increase of particle size.