Study On The Flow Characteristics Of The Pulsating Intermittent Liquid-solid Fluidized Bed With Sinusoidal Liquid Velocity

In recent decades,with the rapid development of industrialization and modernization,the discharge of domestic wastewater has increased sharply.In order to protect the environment and biological health,adopting more efficient sewage treatment methods and changing the overall sewage treatment process should be put on the agenda.The circulating fluidized-bed bioreactor(CFBBR)plant could reduce the cost of sewage transport due to the advantage of the process integration and intensification,which is used as a new technology in the wastewater treatment field.In the conventional liquid-solid fluidized bed,a unidirectional liquid flow is used,and the particles tend to have the same velocity as the liquid flow during the operation time.The particles and the fluid move in the same direction,which limits the further increase in the relative velocity.In this paper,a new type of liquid-solid fluidized bed,the pulsating intermittent liquid-solid fluidized bed(PILSFB),which uses the pulsating liquid flow,was analyzed through experimental and numerical study.The pulsating intermittent liquid-solid fluidized bed was designed and constructed in this paper,and a set of experiments were conducted,varying the liquid phase velocity form and the particle properties(such as the liquid velocity amplitude,the liquid velocity period,the particle size and the particle density).The flow characteristics of the PILSFB during the complete time period were given through the experimental study.A mathematical model of the pulsating intermittent liquid-solid fluidized bed was given in this paper,and the flow characteristic of the pulsating intermittent liquid-solid fluidized bed was analyzed through the Eulerian-Eulerian approach incorporating the KTGF model.The applicability of the appropriate interphase drag model for the pulsating intermittent liquid-solid fluidized bed was analyzed.The axial solids holdup distribution,the radial solids holdup distribution,the axial relative velocity of the solids and the liquid phases and the radial solids velocity in the pulsating intermittent liquid-solid fluidized bed using the sinusoidal liquid velocity was analyzed with the experimental data.The regression analysis for the relative velocities between the liquid and solids phases was proposed in this paper.A comparative study with a conventional fluidized bed verified the feasibility of using the pulsating liquid flow to enhance the relative velocity between the liquid and the solids phases.