Shear zone measurements based on ECT image analysis in slim hopper

Krzysztof Grudzień1 Maciej Niedostatkiewicz2, Zbigniew Chaniecki1, Andrzej Romanowski1 1Technical University of Lodz, Computer Engineering Department, Lodz, Poland, kgrudzi@kis.p.lodz.pl

2Gdansk University of Technology, Department of Fundamentals of Building and Material Engineering,

Gdansk, Poland

ABSTRACT

Paper covers the results of ECT data analysis for bulk solid flow in slim, cylindrical silo model. A series of experiments of bulk solid gravitational flow shows the various conditions for dynamic effects appearing during container unloading. Experiments were conducted for different configuration of initial granular material packing density and silo wall roughness. The scope of this research was ECT measurement data and reconstructed images analysis aimed at detecting the shear zone associated with silo discharging dynamic effects. ECT images allow to visualize shear zone localizations. This is possible thanks to the ECT aptitude for detection of slight changes of material concentration. The rise in container wall roughness is an effective mean for reducing the dynamic effects during material discharging, since these effects result from resonance between hopper construction and trembling material. Such effects in real scale applications can cause damage in industrial equipment, bring danger to its operation surroundings, result in process termination and eventually produce financial losses in consequence.

On the basis of ECT visualisations, wall-adjacent shear zone profiles are analyzed for different wall roughness parameter values. Calculations of the characteristic parameters for shear zones are performed with use of concentration changes derived from ECT measurements.

Keywords Electrical Capacitance Tomography, silo flow, shear zone