2012 Volume 6 Issue 1 Pages 25-40
As material-handling equipment for unloading bulk materials such as iron ore and grain from vessels at harbor piers, continuous unloaders play an important role from the viewpoint of handling performance and environmental protection. Among the various types, belt conveyor-type unloaders are required to provide highly versatile handling performance covering low- to high-fluidity bulk materials. When low-fluidity bulk materials are handled, handling performance decreases and electric energy consumption increases because they do not flow easily into a scraping device. For a scraping device consisting of a horizontal screw and a rotary feeder, this paper proposes a cutting device in which multiple rotatable blades are arranged outside the scraping device. It also describes the basic structure and design guideline of the newly proposed cutting device to improve its low-fluidity bulk handling performance. Furthermore, the driving conditions of the cutting device are optimized, and the improvement of the handling performance is verified by experimental analyses using a model manufactured based on the design guideline. Cement, which is a typical low-fluidity bulk with a large angle of repose, is used for experiments. Low-fluidity bulk materials such as coal, converter slag and soybean meal having some different physical properties from those of cement, such as larger particle size, higher bulk density or higher moisture content, are also examined and discussed as materials for digging. The effect of each physical property on the handling performance, as well as the effect of the proposed device and its effectiveness toward stabilization, are also be clarified, including the basic design and method of optimization.
