Abstract: The entrained-flow pulverized coal gasification process has emerged as a promising and attractive coal utilization technology in China,where it demonstrates a great advantage in energy conversion and environmental protection. Aeration in a hopper used to enhance the flow capability of powder has been widely applied in the coal gasification process and other production processes. Bubbles in entrained-flow bed play an important role in the flow capability, like bubbles in the gas-solid fluidized beds, as they governed the hydrodynamics and efficiency of the operation for which the bed is used, such as gas-solid mixing, heat transfer, mass transfer, and material sorting. This work aims at investigation of the characteristics of the bubble behaviors in the process of powder discharge. All experiments were carried out in a two-dimensional (2D) aerated hopper for visual studies, and the movements of bubbles in different operation conditions were recorded by a high-speed camera. By analyzing the recorded images,both basic rules and the characteristics of bubble movements in the volume, shape, position, coalescence, splitting and annihilating were gained in hoppers. The experimental results showed that the bubble volume increased initially followed by a decrease, while the velocity of bubble increased until it reached a constant value. During the rise of the bubble, its position, size and shape continually changed. In the first stage, bubbles attached to the gas inlet,and showed oblique long shape. In the middle stage, bubbles showed the right angle trapezoid shape and went up uniformly. In the final stage, bubbles showed cap-shaped or round shape and went up uniformly. Aggregation and splitting occurred during bubble rising, and eventually annihilated in the hopper. Aggregation was actually the process that a small bubble was attracted by the large bubble, and finally formed a bigger bubble. Splitting was the result of the uneven force of the bubble, leading to the flow of particles at the top of the bubble. Splitting was more common in larger, flatter bubbles, as the additional pressure was not sufficient to support the upper particles due to the large radius of curvature in these bubbles. The annihilation was the result of the gas entering the bubble less than the gas that infiltrating the solid phase.