A further study on effect of gas type on pulverized coal discharge

• Powder behavior and flowability will be influenced by the previous bulk sate.
• Pulverized coal fed by CO2 shows a higher gravity discharge rate than that of air.
• Both feeding and aerating gases can affect the powder discharge characteristics.

In this paper, a large-scale loop feeding system including pneumatic conveying and hopper discharge was set up; fine pulverized coal was used as the experimental material and four different procedures were designed; discharges of pulverized coal under the action of both gravity and aeration were carried out to further study the effect of gas type on hopper discharge. The experimental results were compared with each other and the effect of powder bulk state as well as feeding and aerating gases on hopper discharge was discussed. Compared to air, CO2 is hard to escape from the adsorbed pulverized coal and thus CO2 feeding corresponds to higher gravity solid discharge rates. The effect of gas type on hopper discharge is much more complicated than previously reported especially when feeding and aerating gases are different. It was concluded that aerating gas determined the discharge characteristics to a large extent and feeding gas would compound the problem. The state of gas–solid fluidization prior to the opening of the hopper outlet was discussed to help understand the differences between discharge results. Experimental results showed that when feeding and aerating gases were air and CO2, respectively, defluidization occurred during aeration in the hopper and discharge ability was weakened resulting in a low solid discharge rate.

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