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2004 | Buch

The Science and Engineering of Granulation Processes

verfasst von: Jim Litster, Bryan Ennis

Verlag: Springer Netherlands

Buchreihe : Particle Technology Series

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SUCHEN

Über dieses Buch

This book had its origins in a meeting between two (relatively) young particle technology researchers on Rehobeth Beach in Delaware in 1992 near the holiday house of Reg Davies (then Director of the Particle Science and Technology Research Center in Dupont). As we played in the sand, we shared an excitement for developments in particle technology, especially particle characterization, that would lead operations such as granulation to be placed on a sound scientific and engineering footing. The immediate outcome from this interaction was the development of new industry short courses in granulation and related topics which we taught together both in Australia and North America. This book follows closely the structure and approaches developed in these courses, particularly the emphasis on particle design in granulation, where the impact of both formulation properties and process variables on product attributes needs to be understood and quantified. The book has been a long time in the making. We have been actively preparing the book for at least five years. Although the chapters have relatively good bibliographies, this book is not a review of the field. Rather it is an attempt by the authors to present a comprehensive engineering approach to granulator design, scale up and operation. It is exciting for us to see the explosion of research interest around the world in this area in the last five to seven years. Some of the most recent work will have to find its way into the second edition.

Inhaltsverzeichnis

Frontmatter
Chapter 1. Introduction
Abstract
Fine powders are a pain. They are difficult to handle and to process. Granulation converts fine powders to granular materials with controlled physical properties. Granulation and related processes cover a wide range of techniques used to form agglomerates that range in size from ~ 100μm to 20mm and varying in structure from loose aggregates to dense compacts. Sometimes even the fine powder feeds are avoided with granules formed from liquid (solution, slurry, melt) feed. Particle size enlargement techniques are used in every processing industry which handles particulate feeds, intermediates or products. This in itself is testimony to the value of the operation. Table 1-1 summarises the many reasons for granulating fine powders.
Jim Litster, Bryan Ennis
Chapter 2. Particle and Granule Morphology
Abstract
Good particle design means understanding particle-particle and particle-fluid interactions and using this knowledge to properly design processes and products. It is the properties of the particle that dictate these interactions so particle characterisation is at the heart of particle design. Good characterisation of both the feed powders and the product granules is essential.
Jim Litster, Bryan Ennis
Chapter 3. Wetting, Nucleation and Binder Distribution
Abstract
In Chapter 1, we divided granulation rate processes into three classes: wetting and nucleation, consolidation and coalescence, and breakage and attrition. Chapters 3 to 5 address each of these classes in turn beginning with wetting and nucleation.
Jim Litster, Bryan Ennis
Chapter 4. Consolidation, Coalescence and Growth
Abstract
If wetting and nucleation are effectively controlled, particles leaving the spray zone will be in one of two forms:
1.
Individual particles coated with a layer of liquid binder (when the drop size is small compared to the particle size); or
 
2.
Loose, partially saturated nuclei granules (where the drop size is large compared to the particle size).
 
Jim Litster, Bryan Ennis
Chapter 5. Breakage and Attrition
Abstract
This chapter considers the last of the three classes of granulation processes that control granule attributes — breakage and attrition. There are really two separate phenomena to consider here:
1.
Breakage of wet granules in the granulator; and
 
2.
Attrition or fracture of dried granules in the granulator, drier or in subsequent handling.
 
Jim Litster, Bryan Ennis
Chapter 6. Mathematical Modelling of Agglomeration Processes
Abstract
Figure 1.5 showed that a granulator can be analysed in several scales. So far, we have analysed important granulation rate processes at the particle and volume-of-powder scale (chapters 3 to 5). In this chapter, we describe the balance equations that describe the evolution of granule property distributions in the granulator ie. granulator scale analysis. A key tool in this analysis is the population balance.
Jim Litster, Bryan Ennis
Chapter 7. Classification and Choice of Size Enlargement Equipment
Abstract
There is an enormous variety of size enlargement equipment available in the market place. In many industries, the choice of equipment and the expertise related to it has resided with the equipment vendor. This is not ideal from the practitioners point of view and unnecessary, given the current understanding of granulation science as described in chapters 2 to 6.
Jim Litster, Bryan Ennis
Chapter 8. Tumbling Granulation
Abstract
Tumbling granulators and coaters include discs, drums, pans and a range of similar equipment. In tumbling granulators, particles are set in motion by the tumbling action caused by the balance between gravity and centrifugal forces. These granulators have the following characteristics:
  • Product granule size is in the range 2 to 20 mm. Tumbling granulators are not suitable for producing very small granules.
  • Tumbling granulators are good for producing high density “balls” or pellets. It is more difficult to produce high porosity agglomerates.
  • Tumbling equipment can also be used for coating relatively large (group D) particles.
  • Discs and drums generally operate continuously and can be up to 4 m in diameter. They are capable of very large throughputs (up to 100 tonne/hr) and are therefore extensively used in mineral processing and fertiliser granulation.
Jim Litster, Bryan Ennis
Chapter 9. Fluidised Granulators
Abstract
In fluidised granulators (fluidised beds and spouted beds), the particles are set in motion by air, rather than by mechanical agitation. Areas of application include fertilisers, industrial chemicals, agricultural chemicals, pharmaceutical granulation and a range of coating processes. Fluidised granulators produce either high porosity agglomerates (from powder feeds) or high strength layered granules (from liquid feeds).
Jim Litster, Bryan Ennis
Chapter 10. Mixer Granulators
Abstract
Mixer granulators use a mechanical impeller to cause powder motion, while the granulator as a whole is usually fixed in space. Liquid binder is sprayed (or sometimes poured) onto the moving powder bed. Figure 10.1 shows a schematic of the elements of a typical batch high shear mixer granulator. In fact, there are an enormous range of geometries and designs over mixer granulators covering batch and continuous configurations and with a very wide range of agitation intensities (shear rates). In many cases, the designs are modifications of those for mixer/blenders in which granulation was noted as a desirable side effect.
Jim Litster, Bryan Ennis
Backmatter
Metadaten
Titel
The Science and Engineering of Granulation Processes
verfasst von
Jim Litster
Bryan Ennis
Copyright-Jahr
2004
Verlag
Springer Netherlands
Electronic ISBN
978-94-017-0546-2
Print ISBN
978-90-481-6533-9
DOI
https://doi.org/10.1007/978-94-017-0546-2