Investigation on the granulation behavior of iron ore fine in a horizontal high-shear granulator

High-shear granulation is widely used in many particulate industries for its good capability to improve the size,strength and composition uniformity of powder substances.This work conducted an experimental study to investigate the granulation behavior of iron ore fine in a horizontal high-shear granulator,such as granules size distribution,granules growth rate,and permeability of the granules bed.The results show that the granule size and permeability of packed granules bed increase gradually with increasing the granulation time,and the growth of granules can be divided into three stages:the rapid growth stage,the slow growth stage and the relatively stable stage.Both the higher rotational speed and larger number of impellers increase the kinetic energy and collision frequency of the particles,which causes the increase of average granule size,growth rate and permeability of granules packed bed.On the other hand,the shear damage effect of the impellers on the granules is also enhanced with the increase of rotational speed and impeller number,resulting in significant granule size segregation.

Scale-up of a high shear wet granulation process using a nucleation regime map approach

Scale-up of the high shear wet granulation （HSWG） process is considered a challenge because HSWG is complex and influenced by numerous factors, including equipment, formulation, and process variables. For a system of microcrystalline cellulose and water, HSWG experiments at three scales （1, 2, and 4 L working vessel） were conducted with a granulator. Scale-up was implemented on the basis of a nucleation regime map approach. To keep dimensionless spray flux and drop penetration time constant, water addition time at three processing scales were 300, 442, and 700 s, respectively. The other process parameters were kept unchanged. Granule size distributions were plotted and compared, and scanning electron microscopy was used to analyze granule surface morphology. Physical characterization was undertaken using a modified SeDeM method. At nearly all scales, granule yield was greater than 85% and all the cosine values were larger than 0.89. At the same experiment points, granules at all scales had similar surface morphology and similar physical characteristics. The results demonstrate that a rational scaling-up of the HSWG process is feasible using a regime map approach.

Further investigations on the influence of scale-up of a high shear granulator on the granule properties

This study focuses on the characterisation of strength, density, and size of granules produced in various scales of a high shear granulator. Calcium carbonate （Durca165） was used as the feed powder and aqueous polyethylene glycol （PEG 4000） as the binder. The dried granules were analysed for their strength, density, size distribution, and wall make-up. Granules were produced in granulators with four scales, 1, 5, 50, and 250 L under three scale-up rules of constant tip speed, constant shear stress, and constant Froude number. The results show that regardless of equipment scale, increasing the impeller speed has a great effect on crushing strength and stress. The underlying cause is an increase in granule density due to more consolidation at higher impeller speeds. Wall make-up is significantly reduced to less than 5% as the scale is increased from 1 to 250 L. The results of this study corroborate our previous findings that the constant tip speed rule is the best criterion for scale-up of high shear granulators.