媒体流動層における大粒径粒子の流動化

抄録

The vertical force acting on a single sphere was measured and the fluidizing conditions of the fluidized bed with suspended packings were studied.
(1) The vertical force (F) acting on a single sphere which was hung in a fluidized bed was measured by a strain gage. At low gas velocity (near minimum fluidization), F was mainly determined by the apparent buoyancy and downward force arising from stagnant solids on the sphere. And with the increase in gas velocity, it was shown that this was gradually influenced by the drag force of moving solids.
(2) The fluidizing conditions of the fluidized bed with suspended packings were studied by changing the diameter and density of the packings. It was found that the boundary of the packed fluidized bed (PFB) and suspended packing fluidized bed (SPFB) could be expressed by W_p/W_s=1 where W_p and W_s are the weight of suspended packings and fluidized particles, respectively. In SPFB, the left hand side in the preceding equation must be less than unity and the density of the packing should be less than the mean density of the bed. The pressure drop of SPFB(ΔP′) was accounted for by the following equation:
ΔP′=ΔP(W_p/W_s+1) where ΔP is the pressure drop of a conventional fluidized bed (FB). And minimum fluidized velocity of SPFB(u_mf′) could be expressed experimentally by u_mf′=m^(V_p/V_s)u_mf for D_p≥25.4mm. 0<(V_p/V_s)≤(V_p/V_s)* m is calculated by logm=log(1-ε_p)/(V_p/V_s) where D_p, V_p, V_s, (V_p/V_s)*, m, u_mf and ε_p are the diameter of suspended packing, volume of suspended packings, volume of fluidized particles, boundary value of PFB and SPFB, constant, minimum fluidized velocity of FB and void fraction of PFB, respectively. Also, It was observed experimentally that the bed expansion of SPFB was less than that of PFB.