Good powder flowability is required in many industrial applications, particularly drug manufacturing. Pharmaceutical production processes strongly rely on powder flowability because the flowability of the powder ingredients a affects the quality and integrity of the final product (Prescott and Barnum, 2000). Many characteristics of particles and their surrounding environment are influenced by powder flowability (Antony, 2007), including: particle size, shape, particle size distribution, moisture content and chemical composition (Bodhmage, 2006). In spite of the extensive amount of research reported so far, powder flow behaviour still remains difficult to predict accurately (Ganesan et al., 2008). To enhance the flowability of powder industries use the granulation method to improve the flow behaviour of powder.
The main aim of this project is to study the flowability improvement of the granules prepared by wet and melt granulation in pharmaceutical industries, in addition to the flowability enhancement using different binding ratios, particle size ranges and storage geometries.
In this research, two granulation methods were applied (i.e. melt and wet) to examine the improvements of physiomechanical properties of the granules. Different variables were considered for the prepared granules: granulation method, binding ratios (5%-15%-25% w/w), particle size ranges (very fine 45-106µm, moderately coarse 250-355µm and coarse 600-710µm), and different hopper geometries. Granular flowability was measured qualitatively using different conventional methods such as, angle of repose, bulk and tapped density, Carr’s index and Hausner Ratio. Schulze (2002) developed a fully automated ring shear cell RST-XS to measure the powder flow quantitatively using different loads which is used in this study. The output results were used to measure granules flowability, cohesivity and wall friction. These parameters are important for designing the silo and hopper geometries with proper internal hopper angles and outlet dimensions to produce uniform flow of powders. Silo design is performed for achieving better flowability for two geometries (i.e. conical and wedge-shaped hopper) which were designed using the data obtained from the ring shear test results. A new non-invasive and advanced flow dynamic method called digital particle image velocimetry (DPIV) was used to understand the velocity distribution of the granular flow inside a typical case of silo with internal angles of 45° and 70°. The starch granules prepared by wet granulation showed better flowability than that prepared using melt granulation. This trend is in agreement with the outcomes of applying shear cell test stated earlier. Additionally, particle size has a significant influence on the flowability of granules, relatively stronger than the binding ratios. Also, PEG granules prepared using melt granulation required a relatively small internal hopper angle compared to starch granules prepared using wet granulation. In addition, starch granules moderately coarse and coarse were able to produce a symmetric flow trend within the flow champers when compared with the PEG granules.
New insights are provided on the flow behaviour of granules in terms of different granulation methods, single-particle characteristics and geometrical conditions. The integrated approach adopted here viz., designing the flow geometries based on using classical shear cells and DPIV provides a holistic and better pathway for designing powder flow geometries.
