An Electrical Capacitance Tomography (ECT) system has been applied to non-invasively visualize the solid distribution in a downflow fluidized bed (downer) with a specially designed distributor. By means of this distributor, air can be supplied from both the axial and radial directions. In order to understand its effect on the solid distribution, the solid concentration characteristic was discussed in both the time and space domains. As a result, the specially designed distributor leads to a more uniform solid distribution near the entrance region. As the measurement position descends, the solid distribution becomes uniform. The solid concentration increases as the center-side airflow rate ratio varies from 1:4 to 1:1. Moreover, the air velocity in the axial direction adversely affects the temporal stability of solid concentration, whereas the air velocity in radial direction contributes significantly to the spatial uniformity. (C) 2009 Elsevier B.V. All rights reserved.