摘要
Abstract
To address the growing demand for low-carbon olefins,this study proposed a coupled catalytic cracking reactor integrating a riser,turbulent bed,and dense bed.Large-scale cold model experiments were conducted to measure the axial and radial solid holdup distribution characteristics in the coupled reactor under varying operating conditions.The results indicated that the solid holdup in the riser exhibited a C-shaped axial distribution,with higher values at both ends and lower values in the middle,significantly influenced by particle circulation rate and superficial gas velocity.Solid holdup in the particle acceleration zone was markedly affected by particle circulation rate,the fully developed zone showed uniform holdup,and the constrained backmixing zone was influenced by particle recirculation,with the concentration increasing.In the turbulent bed,axial solid holdup distribution was categorized into a dense phase zone with high concentration,a dilute phase zone with low concentration,and a transition zone.The dense phase zone holdup decreased with height.The dilute phase zone holdup decreased with increasing particle circulation rate but increased with superficial gas velocity.Besides,complex solid holdup distribution was induced by bubble expansion and particle deposition near the distributor.Radially,the semi-circular fluidized bed displayed an asymmetric solid holdup distribution,characterized by higher values in the planar region and lower values in the curved region,reaching a minimum at r/R=0.4-0.5.Increasing particle circulation rate significantly enhanced solids holdup in the planar region,while that in the curved region became more uniform due to enhanced gas-solid mixing.However,higher superficial gas velocity reduced solid holdup in non-wall regions and intensified its distribution gradients near the wall.Based on the distribution characteristics of solid holdup in different regions of the reactor,people could regulate the reaction process more precisely,thereby improving the product yield and selectivity to meet the diverse needs of the reaction process.关键词
催化裂解/耦合反应器/固含率/轴向/径向分布/流化床Key words
catalytic cracking/coupled reactor/solids holdup/axial/radial distribution/fluidized bed分类
化学化工
