Particulate materials, powders or bulk solids are used widely in almost all areas of the process industries, such as in the pharmaceutical, chemical and cosmetics industries. Hence a good understanding of the physics of particulate materials is desired in order to design efficient processing and handling systems. A successful mixing process is extremely desirable in the powder processing industries, as it could save manufacturing procedures and reduce costs. However, segregation is a formidable problem in mixing processes as it destroys mixtures and causes other kinds of inhomogeneities, all of which will have significant effects on the economics of production.
Basically, segregation is about how particles move and flow under various conditions. The objective of this study is to determine the influence of particle-wall friction and size distribution on particle flow and segregation. Firstly, research on the impact of particle-wall friction and size distribution on particle flow in a transparent cell will be conducted, then mixtures with various particle size distributions will be employed in the transparent cell under different particle-wall friction to examine how different particle size distribution and wall roughness affects segregation. In general, data obtained from the particle flow test revealed that the lower the particle-wall friction coefficient is, the higher the amount of particles flowed. This indicates that at high particle-wall friction, particles will move more slowly, while at low particle-wall friction, particles will move a lot faster. Differences in particle-wall friction cause variations in speed during flow and in turn encourage segregation. The larger the difference in friction coefficient is, the more severe the segregation problem is.
It is also discovered that the larger the particle size distribution is, the worse the segregation condition is going to be. This is because larger particle size distribution means that the gaps between larger particles are bigger, thereby allowing smaller particles to percolate through them easily. Another reason is because the bigger the particles are, the more space they create when they shift up during vibrations, resulting in more spaces available for those smaller particles to settle into, preventing the larger particles from moving back down.