Research On Pressure Gradient And Radial Solid Holdup In Riser

In a self-developed and transparent circulating fluidized bed,install self-made pressure probe.A study on the behavior of catalyst fluidization was carried out,using FCC catalyst with different moisture content and mean particle diameters as solid materials,room air as fluidizing medium.The influence of air velocity Ug,catalyst flow rate GS,particle diameters dp,moisture content w,feed rate Uj,pre-elevating air velocity Up,l,on axial pressure gradient and radial solid holdup was investigated.Based on the gas-solid flow situation and reasonable hypothesis,pressure gradient models of solid-phase flow in dilute region and dense region was founded respectively,and then solved and validated.The results showed that the axial pressure gradient increased with the decreasing of air velocity Ug.With the increasing of air velocity,the shape of axial pressure gradient distribution curve transit from S-type to exponential-type,and to linear type and radial solid holdup distribution curve tend to be gentle.Compared with core region,air velocity has greater influence on the circle region.The axial pressure gradient and radial solid holdup rises with the increasing of catalyst flow rate.Catalyst flow rate has little impact on the pressure gradient when the air velocity is high.Under the same operating conditions,the particles with large mean diameters contribute to higher pressure drop and the particles with small mean diameters contribute to longer accelerating section.Pressure drop rises with the increasing of moisture content.The less moisture content is the more prominent difference of solid holdup between core region and circle region.The feed rate has great influence on the pressure gradient above the nozzle.As the axial position rising,the shape of solid holdup transits from n-type to A-type,W-type,U-type and the impact of feed rate becomes weaker.The solid holdup distribution curve tends to be gentle and the impact of feed rate becomes weaker when the pre-elevating air velocity increases.Based on the experimental data,the dilute region pressure gradient model is established.The calculating value and experimental value fit well.The average error is 7.5%.The dense region pressure gradient model is not accurate.