Minimising the spread of residence-time distribution for flat and heaped powders in a wedge-shaped planar hopper--颗粒学报PARTICUOLOGY

Fullard, L., & Davies, C. (2017). Minimising the spread of residence-time distribution for flat and heaped powders in a wedge-shaped planar hopper. Particuology, 30, 102-110. https://doi.org/10.1016/j.partic.2016.06.002

Minimising the spread of residence-time distribution for flat and heaped powders in a wedge-shaped planar hopper

Luke Fullard ^a *, Clive Davies ^b

a Institute of Fundamental Sciences, Massey University, Palmerston North Campus, Private Bag 11222, Palmerston North 4442, New Zealand
b School of Engineering and Advanced Technology, Massey University, Palmerston North Campus, Private Bag 11222, Palmerston North 4442, New Zealand

10.1016/j.partic.2016.06.002

Volume 30, February 2017, Pages 102-110

Received 25 November 2014, Revised 22 March 2016, Accepted 9 June 2016, Available online 7 October 2016, Version of Record 27 January 2017.

E-mail: L.Fullard@massey.ac.nz; laffnz@gmail.com

Highlights

• The discharge of a granular material from a hopper was modelled.

• Residence time distribution (RTD) was calculated for flat and heaped powder layers.

• Increasing layer angle decreased the spread of the RTD.

• The critical angle to minimise the spread of the RTD was calculated.

Abstract

A wedge-shaped planar mass-flow hopper system was modelled using stress-field theory as found in the literature. The authors present governing equations for stress and velocity fields under a radial-flow assumption in a converging hopper. The velocity in the silo above the hopper is modelled as plug flow. Two set-ups are modelled, one where powder layers in the hopper are assumed to be flat, and the second in which the layers are heaped at some characteristic angle. The ejection times and residence-time distributions are calculated and presented for a range of heap angles. For realistic heap angles, the spread of the residence-time distribution decreases with increasing heap angle; in one case, the spread is halved to a well-defined limit. At this limit (the critical heap angle) the geometry of the hopper can be optimised to minimise the spread of the residence-time distribution, and hence to minimise predicted mixing in the system. We present examples of curves for a variety of parameters that minimise the predicted mixing in the hopper–silo system.

Graphical abstract

Keywords

Residence-time distribution; Radial stress field; Hopper; Heaped layers; Granular

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