Granulation Systems: Collision and Growth of Wet Particles

The development of new medicines is a major factor in improving patients` health. The tablet is one of the most popular medicines used and is therefore the subject of the research project. Tablets consist of compressed granules containing small powders. To make such particles easy to handle, they are transformed into large agglomerates (as collections of particles) in a process called granulation. In this process, several steps are taken: i) sticky solutions (as binders) are sprayed over the particles to make them wet; ii) the wet powders are brought into contact by the air flow or mechanical agitation; iii) collision with neighbouring particles causes the wet particles to form binary granules through the liquid bridges; iv) on collision with other granules/particles, these granules grow in size. However, these collisions can lead to the breakage of the bridge and thus the granules. At this step, the granules are ready for further processing for tablet production. The design and optimisation of the granulation process is a major challenge, which requires fundamental research to be carried out in order to understand the mechanism of granulation. Therefore, in this project we focus on the collision of wet particles, as the most fundamental phenomenon in the granulation process. Our main objective is to understand which parameters influence the strength of the granules against fracture. This can be done by evaluating the forces acting on the primary particles through the fluid bridges. Using numerical approaches, we discretise our particles and the fluid bridges (known as the computational domain) into very small cells with uniform properties in terms of velocity, pressure, fluid fraction, etc. Then we solve the equations describing the force balance for all cells in the computational domain. This calculation has the potential to provide us with an understanding of how the fluid is distributed across the particles as they collide, adhere to each other and rebound. Furthermore, this approach can give us a deep insight into how the fluid is redistributed when another particle collides with this binary system to form larger granules. Following this, we will evaluate the contribution of the forces to the granule thickness. We will perform this analysis for a very small to very large amount of fluid bridging the particles. In this study, we will be able to quantify the conditions under which agglomeration or fracture of the particles can occur. This study can help us quantify the rate of particle agglomeration. This can be a basis to improve the design and optimisation of granulation processes in the pharmaceutical industry.