Controlling Material Trajectories and Minimizing Drop Heights
The path that bulk material follows as it exits the delivery conveyor is termed its trajectory. This trajectory is influenced by several factors including the belt speed, the angle of inclination of the discharging belt, and the shape of the material on the belt. In traditional transfer-chute design, engineers plot the trajectory to estimate where the material will initially impact the head chute wall. From there, the material is expected to rebound off the chute wall, similar to light bouncing off mirrors. CEMA's Belt Conveyors for Bulk Materials, Sixth Edition, offers a detailed guide on how to calculate and plot these trajectories.
Common errors in this design phase include inaccurately estimating the initial material trajectory and overlooking the impact of friction when predicting subsequent reflections from the transfer chute walls.
Current trends in transfer-chute design emphasize controlling the flow of bulk material to prevent free-falling onto the receiving belt. This controlled approach assumes the material profile remains relatively uniform, minimizing the risk of it spreading out excessively. By reducing drop heights, designers aim to mitigate issues such as material degradation, dust generation, and wear on the receiving belt.
Achieving this requires understanding the frictional characteristics between the bulk material and the chute materials. Conventional chute design now employs Discrete Element Modeling (DEM) methods to aid in assessing how changes in properties, such as friction coefficients, affect performance. Various DEM software packages are available on the market for this purpose.