Experiments　were　made　on　axial　concentration　distribution　of　binary　solid　mixtures　in　a　three-phase　fluidized　bed　of　4.2　cm　I.D.　and　150　cm　height　under　continuous　operation　mode.　Biurea　particles　with　different　diameters　and　a　mixture　of　biurea　and　blowing　agent　ADC　with　different　wettability　were　used　in　the　experiments.　One-dimensional　sedimentation-dispersion　model　was　modified　by　taking　into　consideration　of　the　effects　of　both　particle　size　and　wettability　on　particle　settling　velocity　to　describe　the　axial　concentration　distribution　of　each　solid　component.　Agreement　between　experimental　and　model　predicted　data　is　satisfactory.