| Pipe grid gas distributor is a type of gas distributor which is commonly used in catalytic cracker regenerators.However,this type of distributor has a series of problems such as uneven gas distribution,wear of tubes and nozzles,degraded catalyst fluidization quality and poor catalyst regeneration in the actual operation process,which seriously affects the normal operation of the catalytic cracking device.The performance and wear phenomenon of the gas distributor are closely related to the jet characteristics of the nozzle in the dense phase bed.Therefore,the study of the jet characteristics of the nozzle of the pipe grid gas distributor in the dense-phase bed and the influence on the flow state of the jet area is operated for the analysis of the performance and wear mechanism of the gas distributor and the optimization of the structure of the distributor,which is of important guiding significance.In a two-dimensional rectangular bed experimental device,FCC catalyst particles were used in this study.The method of photographic inspection and pressure sensor was used to examine the influence of the nozzle gas velocity,nozzle jet angle,static bed height,and nozzle extension on the jet length,the pressure drop of the nozzle,the pressure fluctuation at the outlet of the nozzle and in the region of the jet.The main conclusions are as follows:The jet length of the nozzle becomes longer as the nozzle outlet gas velocity and the jet angle increase.In the upward turning process of the jet,a swirling vortex phenomenon occurs between the two branch pipes of the gas distributor.The size of the swirling vortex is closely related to the nozzle outlet gas velocity and jet angle.The experimental phenomenon indicates that the rotating vortex is the direct cause of the wear of the outer wall of the branch pipe.Based on the experimental data,a calculation model for nozzle jet length was established.The nozzle pressure drop increases with the increase of the nozzle outlet gas velocity and the nozzle length,and the formula for the nozzle pressure drop is established.The main influencing factors of nozzle pressure fluctuation at different jet angles are the impact of jets from adjacent nozzles.The secondary influence factor is the particle concentration.When the jet angle is 45°,the pressure fluctuation at the outlet of the nozzle increases as static bed height and nozzle extension length increase.The bed pressure in the jet area decreases with the increase of axial height and jet angle,and increases with the nozzle outlet gas velocity,static bed height and nozzle extension length,and is determined by the amount of material above the measuring point.When the jet angle is 0° and 22.5°,the bed between the branches is in the dense phase region,and the pressure fluctuation is caused by the movement of bubbles;when the injection angle is 45° and 67.5°,the bed between the branches is in the jet area,and the pressure fluctuation increases first and then decreases as the axial height increases,and increases as the nozzle outlet gas velocity,the static bed height,and the nozzle extension length increases,and is determined by the turbulence of jet.The main source of the pressure fluctuation at the nozzle outlet and jet area of bed is the movement of small particle groups,and the secondary source is the motion of dispersed particle. |
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