In this payer, three how regimes, such as fixed bed, partially fluidized bed and fluidized bed (or spouting bed), are observed successively with the increase of superficial gas velocity for a Geldart-D powder in a conical bed with three cone angles. The conditions of the regime transition and the hydrodynamics for the three flow regimes have been studied experimentally and systematically. The experimental results show that the bed cone angle and the particle bed height are the main factors influencing the regime transition and hydrodynamics of the particle bed. The measurements are compared with calculated results from relevant models and correlations. The predicting capability of the different models and correlations has been discussed. The mechanism for the occurrence of partial fluidization has also been analyzed and a correlation between the spouting pressure drop and the stagnant bed height H-m is given based on the experimental measurements.