In this paper, lignite and glass beads with different particle size were selected as experimental materials. These powder materials were discharged from hoppers in the situations of without insert (No-In), with confined insert (Con-In) and with unconfined insert (Ucon-In), respectively. The discharge processes were first discussed in detail and consequently, the solid flow rate of powders was obtained and analyzed. The flow zones in hoppers were divided based on the radial flow model of powder flow and the effects of inserts on the flow zone evolution were revealed. Experimental results show that both confined and unconfined inserts are beneficial to the increase of the solid flow rate, especially for the weaker flowability powders. The lignite, with the worst flowability, shows the largest increment of solid flow rate giving a value of 58% under Con-In. Considering characteristics of the inserted hopper structure as well as the development of flow zones, a modified model derived from the minimum energy theory was developed. The model was able to predict the solid flow rate through both the traditional hoppers and the inserted hoppers, with the deviation below than 10%. (C) 2020 Elsevier B.V. All rights reserved.