Study On The Particle Distribution And Pressure Drop Of A Horizontal Multi-tube Circulating Fluidized Bed

The circulating fluidized bed heat exchanger has a promising application prospect for its good performance in heat transfer enhancement and fouling prevention and descaling.In this research,a set of cold model and horizontal multi-tube circulating fluidized bed heat exchanger is designed and built,with transparent tube bundle for the visualization research.With water and six kinds of inert solid particles as the liquid phase and solid phase,the effects of circulating flow rate,amount of added solid particles,diameter and density of particles on the fluidization and distribution of solid particles in the horizontal tube bundle and single horizontal tube are investigated by using image measurement and acquisition system of a charge-coupled device(CCD)and pressure transducer.The pressure drop of the liquid-solid circulating fluidized bed is also systematically discussed.The research results show that the particle distribution in the horizontal tube bundle is non-uniform.The non-uniform degree of particle distribution decreases with the increasing of the circulation flow rate and the amount of added solid particles.The particles with smaller diameter and density are fluidized and distributed better in the horizontal tube bundleIn the horizontal tube bundle,the particle holdup of in 5# tube is the highest,then the solid holdups in the 4# and 3# tube are less,and those in the 2# and 1# tube are the lowest.Most of the particles concentrate below the centerline of the tube for the effect of gravity.With the increasing of the circulation flow rate and the amount of added solid particles,the particle distribution becomes more uniform and the particle holdup in the tubes increases.The particles with smaller diameter and density are fluidized and distributed better in the horizontal single tube.High turbulent extent of fluid results in more uniform particle distribution in the horizontal tube.The three-dimensional phase diagrams are established to show the variation ranges of the operating parameters for more uniform particle distribution and relatively high solid holdup in the tube.The pressure drop of the horizontal tube bundle increases while the circulation flow rate and the amount of the added solid particles increase.There is no obvious influence of the particle diameter and density on the pressure drop.