Numerical Modeling for Wet Granulation Processes
Granulation, defined as a size enlargement in which small particles stick together by having a liquid bind onto their surface, plays an extremely important role in the powder-handling process. It is widely applied in particle manufacturing processes of the pharmaceuticals, food, fertilizer, forage, agricultural chemicals, ceramics, iron ore, and other chemical industries.
It is conducted mainly to produce particulate materials of desired size, shape, density, and so on. Depending on the application, requirements for the granulated product and the feed to be granulated can be quite diverse. For example, the average particle size of the product could be as small as 100 μm or as large as 10 mm, and the feed could consist of a solution, slurry, or dry fine powder. One common requirement for all applications is that the granulated products are easy to process, handle, store, transport, and use. Another purpose is to prepare uniform mixes to prevent the segregation that can occur among blends containing two or more solids of different densities or sizes. In the pharmaceutical and food industries, granulation is especially useful in controlling dissolution and disintegration speed of granulated products including API (active pharmaceutical ingredient). Adding many functions to the original particle by layering granulation and improving product appearance and properties are also important aspects of granulation.
Despite its wide application in industry, however, many industrial plants still operate the granulation process based on their experts’ knowledge and experience because of the lack of science and engineering expertise pertaining to granulation. Recently, numerous research projects have been devised to control and optimize the granulation process by using on-line measurement of important process parameters and granule properties (e.g., size, moisture content), and using numerical models which accurately predict granule growth behavior.
Modeling and numerical simulation, in particular, have gathered much attention because, through a rapid advancement in computer science and technology, it has become possible to treat actual granulation phenomena precisely, taking into account the powder’s properties, size distribution, irregular shape, and large number of particles.
This chapter discusses the numerical models which can be used to understand the granule growth mechanism and its behavior in the granulation process.
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Article Information: Satoru Watano, Hideya Nakamura; Sciencedirect