Tomographic measurements of solids mass flow in dense pneumatic conveying. What do we need to know about the flow physics?

Tomography is used to determine the distribution of heterogeneous phases, concentration of one component in another, and, under certain conditions, the velocity vector. The latter is usually achieved by applying multi-plane tomography systems and cross-correlation techniques.

Flow patterns in the dense pneumatic conveying show many interesting features and analogies with gas-liquid flows. Typically, materials conveyed in a dense phase system are not very cohesive and exhibit a permeability and de-aeration rate that are either both low (moving bed) or both high (slug or plug). High permeability and de-aeration rates characterise polyamide chips used in the experiments, and the modes of a dense transport of this material were investigated.

The experimental work was conducted in a pilot-plant-scale flow rig at UMIST. Granular material was conveyed within a 57-mm pipeline with solids feed up to 900 kg/h. The flow phenomena in both horizontal and vertical sections were investigated by means of a high-speed camera (500 frames per second) and a twin-plane electrical capacitance tomography (ECT) system.