Segregation of free-flowing materials possibilities of developing and correcting it

Even a small amount of sliding over a sloping surface may become the cause of marked coal flow segregation (the length of chute 3 was 0.5 m and the coal was in contact with it for 0.35 m). By changing the slope angle of the sliding surface (the chute) it is possible to influence the nature of the process. The segregation is retained when the coal is placed on a uniformly moving base (track, conveyor belt, etc.). It is possible to use this effect during coal flow over an inclined chute to decrease the charge inhomogeneity. (For instance, in our case it appeared possible to change the coal inhomogeneity, caused by segregation on chute 1 and in the rotor, in any direction by changing the position of chute 3). It must be noted that our investigations were carried out using dry preheated coal having high mobility. It is possible to control the homogeneity of normal (wet) charge material by means of short sections of chutes although not so effectively. Nevertheless establishing the fact that segregation on sloping surfaces is the cause and means of controlling the inhomogeneity of free-flowing materials merits consideration while the method of exposing sources and reasonsmore » for segregation by investigating the uniformity of part of the material flow deposited on a uniformly moving base is useful. It is logical to assume that the charge inhomogeneity over the flow cross sections took place not because the mills and blenders were not able to mix better but because there was coal segregation during flow which was influenced considerably by the charge material properties. The reasons for the segregation may be the different trajectories of the coal particles in the body of the mill, mixer, in the space below the screen, in the transfer equipment and in bunkers and determined by differences in particle sizes, densities, elasticities, etc.« less