Study On Particle Motion Characteristics Of Spray Gas-solid Fluidized Bed Based On PIV

The spray gas-solid fluidized bed is an important device for achieving gas-solid two-phase flow.It has been developed maturely and has been widely used in various chemical industrial fields.With the addition of liquid during the operation process of spray gas-solid fluidized bed reactor,affected by the liquid,the particle motion behavior will be different from that of conventional gas-solid fluidized bed reactor.It is necessary to further understand the motion characteristics of particles in the reactor in order to optimize industrial equipment.Therefore,the particle image velocimetry technology and modern analysis methods are used to study the particle motion characteristics in a spray gas-solid fluidized bed,hoping to provide theoretical guidance for the operation optimization of industrial reactors.A spray gas-solid fluidized bed experimental platform equipped with particle image velocimetry system is built for experiment.Particle motion image in fluidized bed was captured by high-speed camera.The information entropy of particle motion image under different liquid-solid ratio and liquid viscosity was captured.And Particle image velocimetry system was used to study the particle velocity distribution in different regions.First,the information entropy of particle motion image was extracted and analyzed recursively.Recursive analysis of the information entropy of particle motion images in fluidized bed shows that with the increase of liquid-solid ratio,the result shows a trend from weak to strong and then weakening,The periodicity of particle motion in fluidized bed weakens first,then strengthens and then weakens.While with the injected liquid viscosity increasing,all the recursive characteristics become weaker,but increased dramatically at 10.05 mPa·s.Compared with fine particles,the recursive characteristics of large particles change earlier,more susceptible to the effects of the injected fluid.The results of the recursive eigenvalue analysis and the qualitative analysis of the recursive graph are unified.The particle motion regularities in the fluidized bed can be clearly reflected by the recursive analysis.Then,the variation of particle velocity horizontal and vertical component in different regions of fluidized bed under different experimental conditions was obtained.Particle image velocimetry system was used to measure the particle flow field in fluidized bed.And the change of coherent structure in the flow field was analyzed by proper orthogonal decomposition.It was found that the particle velocity in the central zone of fluidized bed was more susceptible than that in the side wall zone.When the liquid-solid ratio is 0.59% in the fluidized bed,the particle velocity in the side wall increases obviously,it is good for fluidized mixing.With the increase of injected liquid viscosity,the trend of particle velocity is similar to that of water at the same liquid-solid ratio.The change of liquid viscosity has little effect on particle motion.Through the proper orthogonal decomposition of the flow field,it was found that with the injection of liquid,the larger eddy structure in the flow field diffuses from the side wall area to the whole flow field,it became long and thin and the particle motion tends to be integrated.