Comparison of the electric charging properties of particulate materials in gas–solids flows in pipelines

The charging trends of particulate materials in gas–solid flows in pipelines are of considerable interest to designers of such flow systems, particularly with regard to flow instruments based on electrostatic measurement principles. Such data may also be useful to other researchers in associated fields. The authors of this paper, therefore, set about obtaining such data empirically. In order to achieve this, a small-scale test rig was designed incorporating a 26.5 mm bore pipeline, particulate material feeder, and electric charge measurement equipment. Charging trends are reported for flow velocities in the range 16–36 m/s and particle concentrations in the range 5–50 mg/m3. Aluminium hydroxide, aluminium oxide, sugar and pulverised coal samples graded to have particle sizes in the range 90–106 μm were tested. Samples of aluminium hydroxide graded to between 45–53 and 63–75 μm were also tested.