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In this paper, the Computational Fluid Dynamics–Discrete Element Method (CFD-DEM) coupling method was used to simulate the pneumatic transport of pebble particles in a three-blade spiral tube. The results showed that the flow field distribution rotated along the circumference after loading. The maximum velocity of the flow field after loading was manifested as rotation along the circumference. In addition, the swirl intensity decreased exponentially with the increase in conveying distance, and the maximum swirl intensity had a saturation value. After reaching the saturation value, it is not evident that increasing the initial air velocity significantly affected swirl variation. The smaller the pitch, the greater the initial swirl intensity. The swirling flow was conducive to the fluidization of particles, but it would bring a significant energy loss. Increasing the swirl can increase the degree of particle dispersion. There is an optimal tangential airflow velocity, which allows the particles to fully spin and stay in the suspension zone without being thrown onto the pipe wall by excessive centrifugal force. At this time, the energy efficiency reaches the highest level. A 5.87 m/s velocity was deemed the optimal tangential airflow velocity for conveying 3 mm particles. [ABSTRACT FROM AUTHOR]

Pneumatic conveying is widely used in coal mining. As the lowest conveying velocity of materials, the pickup velocity is the key to the study of gas–solid two-phase flow. In this study, the pickup velocity of pebble particles was experimentally investigated. When the particle size is 3–9 mm, the airflow velocity was found to suitably describe the results as a function of the pickup velocity and have a high correlation. When the swirl number is 0.2, the optimal swirl number was found for which the highest particle pickup ratio was observed. Based on four different methods, namely, visual observation, mass weighing, coefficient of difference analysis, and determination of the peak-average ratio of the pressure drop in the flow field to measure the pickup velocity of the spraying material, the results showed that the accuracy of the particle pickup velocity obtained through visual observation was the lowest, and when the mass–loss rate of the particle was selected as the measurement index of the pickup velocity, the accuracy was the highest. The results will help to realize the long-distance transportation of spraying materials in inclined roadway under the shaft. [ABSTRACT FROM AUTHOR]