Granular flow fields in vertical high shear mixer granulators

Abstract

This study aims to elucidate some basic features of the granular flow field in a conical frustum-shaped vertical high shear mixer granulator by using the Positron Emission Particle Tracking technique. The tested range of particle size (d 50 ¼ 23, 43, and 60 lm) and shape as quantified by the angle of internal friction (268 and 388) have a negligible effect on the granular flow field in the mixer granulator. Density of particle imposes great influence on the flow field where reducing density from 2600 to 700 kg m 23 increase the tangential velocity by 1.95 time. Decreasing fill level from 3.5 to 0.9 kg increases the tangential velocity by a factor of 1.19. No obvious discrepancy in the solids motion is seen between machines of 1 and 5 L capacity and both machines have similar mixing and dispersion with constant tip speed criterion.

Dem investigation of horizontal high shear mixer flow behaviour and implications for scale-up

“…As it is not straightforward to obtain the internal flow and stresses through experimentation, kinematic and dynamic similarity are often not discussed and established in scale-up work. Most experimental flow studies in high shear mixers are focussed on the surface flow using high speed imaging [6][7][8][9][10], while some studies on the internal flow were carried out mostly using the Positron Emission Particle Tracking (PEPT) technique [11][12][13][14], although this technique is costly, less accessible and limited to velocities below 2 m/s [15][16].…”

“…For scale up studies, little work has focussed on studying the internal flow [12][13]23] and stresses/ energies [23,[26][27] in different scales vertical axis mixers. Ng et al [12] and Hassanpour et al [13] measured the internal flow using the PEPT method, while Nakamura et al [23] investigated the internal flow using DEM.…”

“…Ng et al [12] and Hassanpour et al [13] measured the internal flow using the PEPT method, while Nakamura et al [23] investigated the internal flow using DEM. Both Ng et al and Nakamura et al found that the internal flow/kinematic similarity is maintained using constant tip speeds, i.e.…”

A multiple radioactive particle tracking technique to investigate particulate flows

“…The optical methods are essentially limited to transparent systems while radioactive techniques can be applied in opaque systems, because gamma rays can penetrate relatively easily through various materials. PEPT uses two positron‐sensitive detectors mounted on the opposite sides of a system to detect pairs of exactly back to back gamma rays resulting from the annihilation of a positron . This technique is able to detect a tracer when this tracer is within the volume covered by the detectors.…”

Impact of surface tension and viscosity on solids motion in a conical high shear mixer granulator

“…Wet massing granulation is one of the most important unit operations in the chemical, pharmaceutical, detergent, and nuclear industries for enhancing the flowability, appearance, strength, and other physical and mechanical properties of particulate solids 1–3. It takes place in one of the two types of closed granulating systems: low to medium shear granulators such as fluidized bed granulators and high shear mixers as is used in this study.…”