ABSTRACT
Transportation of powder in the gaseous state is known as pneumatic conveying, of which familiar application is a vacuum cleaner, and uses air forces acting on particles exposed in an air stream in a pipe. The transport distance is 2 km at most, and to select flexible routes is easy due to pipeline transportation. Determination of an optimum pipeline and air source is required in design for a given transport distance and mass flow rate of given powder. Conveying systems consist of an air source, powder feeder, conveying pipe, gas particle separator, and air filter. In the positive systems (Figure 5.1), powder is fed into an air stream through a feeder at above ambient pressure and is continuously discharged into the outside at destinations. Foreign substances are not mixed in transported materials. When the air pressure at the feeding point is high, a continuous feeding is difficult and a batch system using a blow tank is employed (Figure 5.2). The positive systems are favored to deliver the powder to several destinations. In the negative systems, the powder can be continuously fed into an air stream at ambient pressure, but it is difficult to discharge it continuously to the outside at the destinations. While the available pressure for transport is limited, the powder does not leak out of the pipeline. These systems are used to collect powder from several points and deliver it to one destination. Besides, there are positive-negative systems that take advantage of both systems. While most systems are open, using air as a conveying medium, closed systems are used for specific cases such as toxic, explosive, and hygroscopic powders in a controlled environment. Circulating systems are employed for fluidized beds.
