Experimental Studies On Hydrodynamics In An Ebullated-Bed Reactor With Different Solid Holdups

Because of its simple equipment,easy operation and good mass and heat transfer performance,the ebullated-bed reactor(EBR)is applied in many fields,such as petroleum engineering,biochemistry,wastewater treatment and so on,so it has important scientific value and industrial applications in further research on EBR.The hydrodynamics of EBR are the key to design,scale and optimize the operation.Therefore,it is necessary to do a further research on the ebullated-bed reactor.Experiments were performed to study the hydrodynamic characteristics of ebullated-bed reactor operated under the condition of high solid concentration up to 60%by volume in a Plexiglas column of 7.0 m in height and 0.286 m in inside diameter using air as the gas phase,tap water as the liquid phase and spherical alumina pellets as the solid phase.We got a large number of experimental data,including total gas holdup,rise velocity of large and small bubble,gas-liquid mass transfer coefficient,axial solid concentration distribution and so on.The effect of gas and liquid superficial velocity and solid holdup on these hydrodynamics were discussed.The experiment found that with the increase of gas velocity,total gas holdup,large bubble diameter and velocity,liquid volumetric mass transfer coefficient,particle concentration distribution and axial solid dispersion coefficient are increased,but small bubble diameter and velocity are reduced.With the increase of solid content,total gas holdup,liquid volumetric mass transfer coefficient and axial solid dispersion coefficient are reduced,but large bubble diameter and large bubble rising velocity increases.With the increase of solid content,small bubble diameter increases first,but goes into zero at the condition of high solid holdup.In addition,the so-called one-dimensional sedimentation-dispersion model was used to describe the axial solid concentration profile,and a correlation for axial solid dispersion coefficient as a function of gas superficial velocity and solid loading was proposed.