Abstract: The effect of angles between nozzle and riser in vertical direction on the flow properties was investigated in a large CFB cold simulation test device. The axial and radial distributions of particle concentration，instantaneous particle concentration signal and probability density analysis in three angles cases were investigated. The results showed that in the pre-lift section and the conveying section，no significant difference between the three cases was found，and the difference existed mainly in the vicinity zone above the nozzle; compared with the traditional equal-diameter riser，the solid-holdup of the bed in the variable-diameter riser increased，the particle distribution was more uniform, but the particle concentration gradient reduced，which is beneficial to the mixing and contact of the gas-solid two phases. As the nozzle angle increased，the diffusion velocity of the gas increased over the entire section，the radial distribution was more uniform，the gas-solid separation phenomenon was effectively suppressed，the gas-solid turbulence was more severe，resulting in more effective contact in the variable-diameter riser.

Key words: riser reactor, nozzle, particle concentration, contact efficiency