Papers by Author: Jan Dirk Prigge

Abstract: Over the past 50 years, a strong foundation for the professional discipline of bulk solids handling has been provided, but so far, the theories for predicting funnel-flow are still quite empirical. In most cases, only two-dimensional stress field models are applied, which overestimate the stable pipe or rathole dimensions defining the core of the funnel and lead to draw-down and live capacity determinations, which are too conservative. More recently, Roberts [ introduced a new, more realistic, hoop stress theory based on the three-dimensional stress state occurring in a rathole. To verify the validity of the new theory, the current research upon which this paper is based, involves an experimental study of rathole formation in laboratory scale model funnel-flow bins and gravity reclaim stockpiles. A two-dimensional laser line scanner is used to depict rathole profiles, while load cells and pressure sensors are applied to determine instantaneous loads and pressure conditions during filling, storage and discharge. Iron ore fines are used as the test material, with the test program including flat-bottom bins with different diameters as well as varying filling levels and outlet diameters and stockpiles with variable heights and outlet diameters. The tests demonstrate the capability of laser scanning to describe rathole profiles. In addition, the suitability of the load cells and pressure sensors to describe the relevant funnel-flow parameters is shown.

Abstract: This paper presents the experimental results of mass-flow hopper arch geometry investigation, which was conducted using a variable geometry plane-flow bin. The cohesive arches formed under different critical outlet openings and hopper half-angles were measured using a 360° two-dimensional laser line scan system. This system was employed to obtain the complete surface profile of each arch across the width of the outlet by moving the rotating laser along the total length of the outlet. The test results were analyzed using Matlab, adopting stationary wavelet transformation de-noising to decrease the signal noise generated during the testing process. The geometric data for each single line scan was smoothed and combined to present a three-dimensional arch surface profile shown to be in good agreement with the observed experimental arch profiles. The angle η at the intersection of the arch with the hopper walls was then calculated by running a Matlab program and a new angle η' is introduced to the arch shape study. The detailed results are discussed in the paper. Arch geometry models, such as the parabolic arc and circular arc arch models developed, respectively, by Walker [ and Enstad [ are reviewed and their relevance is discussed based on the experimental results presented in this paper.