Experimental Study On Distribution Of Forces Acting On Slats Immersed In A Gas-Solids Fluidized Bed

The addition of internals in the fluidized bed can break air bubbles to inhibit the growth of bubbles,inhibits gas-solids back-mixing in the bed,enhances mass transfer and heat transfer efficiency between the two phases,and improves product selectivity.So they are wildly used.However,in the fluidized bed,the internals are subjected to various forces such as gravity,buoyancy,the drag generated when the fluid passes,and the impact force of particles and bubbles.Especially the impact force of particles and bubbles,the long-term effect of this force may cause the strength of the internal components to damage and fatigue failure,which will affect the normal operation of the device,and even result in shutdown production.Therefore,it is of great significance to study the force characteristics of internals.This article expands the research on the force characteristics of the slat internals in our research group.It mainly investigates the force distribution characteristics of the inclined slat in the bed under the conditions of starting and stable operation,including the force distribution characteristics in different transverse directions,the effect of different spacing on the force characteristics of the slat,and the effect of the location,number of grids and distance of the grid on the force characteristics of the slat.The experiment was carried out in a three-dimensional cold-molded fluidized bed of300 mm×300 mm×5000 mm.The bed particles were divided into FCC catalyst particles(Geldart A)and quartz sand particles(Geldart B).The slat is fixed on the fixed member by one end and inserted into the dense phase section of the fluidized bed in the form of an angle of 45~o with the horizontal plane.The lateral position and spacing of the slat can be adjusted by changing the installation position and the number of slats on the fixing member.The installation position,number of grids and distance of the grid can be adjusted by inserting the grid at different positions of the fluidized bed.The magnitude of the dynamic force of the slat in the fluidized bed is measured by the method of pasting the strain gauge on the surface of the test slat.The force of the slat in the stable operation condition is represented by the RMS value of the uniform load,the force of the slat under the starting condition is represented by the peak uniform load.The experimental studies have found that,under stable operating conditions,the symmetry of the forces acting on the slat at different lateral positions is poor when a single slat plate is installed in two kinds of particle fluidized beds.In the A-type granular fluidized bed,the force acting on the slat at each position at low gas velocity changes little;under high gas velocity,the force acting on the slat gradually decreases from left to right.In the B-type granular fluidized bed,the force acting on the slat exert little change in force along the transverse position.When five slats are installed,the force acting on the slat is significantly smaller than when the single slat is installed,and the slats at different lateral positions are gradually increased from left to right.Under the start-up conditions,the symmetry of the slat at different lateral positions in the two particle fluidized beds is relatively good.When installing one slat,the peak uniform load increases gradually from the edge of the fluidized bed to the middle position and reaches the maximum at the middle position.When installing five slats,the force acting on the slat gradually decreases from the side wall to the middle of the fluidized bed.In both conditions,the addition of slats in the cross-sections of the two particle fluidized beds and the installation of the grid at the bottom of the slat can reduce the force acting on the slat,and the reduction effect gradually increases when the spacing of the slats in the transverse position and the distance between the grid and the slat are decreases.