Agglomeration Processes...1 Introduction In 1957, under the leadership of Professor Dr.-Ing.Hans Rumpf at the Technical University (TH) of Karlsruhe, Germany, Mechanical Process Technology

Wolfgang Pietsch

Agglomeration Processes

P he no men a, Tech no I og ies, Eq u i p m e n t

This Page Intentionally Left Blank

Wolfgang Pietsch


Phenomena, Technologies,

Equipment

This Page Intentionally Left Blank

Wolfgang Pietsch


P he no men a, Tech no I og ies, Eq u i p m e n t

Dr.-/ng. Wolkang Pietsch, EUR INC

COMPACTCONSULT, INC. 2614 N. Tamiami Trail, #520 Naples, Florida 34103-4409 USA

In Europe: Holzweg 127 67098 Bad Durkheim, Germany

Cover illustration

Like an agglomerate, the picture on the cover is composed of many disparate components, all of which relate to the topics discussed in this book. The panels on the left and right are microphoto- graphs of naturally agglomerated nano-particles The top and the bottom panels depict different products from spray drying and fluid bed agglomeration. The four sectors (between the panels and the circle) represent Scanning Electron Micro- graphs (SEMs) of agglomerate structures as well as photographs of coated agglomerates and of gran- ules. The top half of the circle shows products from tumble/growth agglomeration and the lower half are briquettes from roller presses as well as product from compaction/granulation. The center square includes tablets from punch and in die presses. The originals of the individual pictures from which sections are reproduced were supplied by (in alphabetical order): Albemarle Corp., Baton Rouge, LA, USA: Cabot Corp., Tuscola, IL, USA: Eirich, Hardheim, Germany: Euragglo, Qievrkhain, France; Niro A/S, Soeborg. Denmark; Norchem Concrete Products, Inc., Fort Pierce, FL, USA: Koppern GmbH & Co, KG, Hattingen, Germany. Their support is appreciated and acknowledged

This book was carefully produced. Nevertheless, author and publisher do not warrant the information contained therein to be free of errors. Readers are advised to keep in mind that statements, data, illustrations, procedural details or other items may inadvertently be inaccurate.

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I"

Con tents

1

2

3

4

5 5.1 5.1.1 5.1.2 5.2 5.2.1 5.2.2 5.3 5.3.1 5.3.2 5.4 5.5

6

7 7.1 7.2 7.3 7.4 7.4.1 7.4.2

Dedication, Acknowledgements and References VII

Introduction 1

A Short History of Agglomeration 3

Agglomeration as a Generic, Independent, and Interdisciplinary Field of Science 5

Glossary of Agglomeration Terms 1 1

Agglomeration Theories 29 The Development of Strength of Agglomerates Binding Mechanisms 35

Binders, Lubricants, and Other Additives Estimation of Agglomerate Strength 55 Theoretical Considerations 55 Laboratory and Industrial Evaluations 61

Structure of Agglomerates 76

General Considerations 78

Porosity and Techniques That Influence Porosity Other Characteristics of Agglomerates 100

Undesired and Desired Agglomeration 109

32

42

89

Agglomeration Technologies 133

Tumble/Growth Agglomeration 139

Mechanisms of Tumble/Growth Agglomeration 140

Kinetics of Tumble/Growth Agglomeration 144

Post-treatment Methods 150 TumblelGrowth Agglomeration Technologies 151

Disc and Drum Agglomerators 153 Mixer Agglomerators 164

VI Contents

7.4.3 7.4.4 7.4.5 7.4.6

8 8.1 8.2 8.3 8.4 8.4.1 8.4.2 8.4.3 8.4.4

9 9.1 9.2 9.2.1 9.2.2

10 10.1 10.2 10.2.1 10.2.2 10.3

11 11.1

11.2 11.3

12

13 13.1 13.2 13.3 13.4

14

14.1 14.2 14.3

I Spray Dryers 187

Fluidized Bed Agglomerators 196 Other Low Density Tumble/Growth Agglomerators Agglomeration in Liquid Suspensions 221

212

Pressure Agglomeration 229

Mechanisms of Pressure Agglomeration 231 Structure of Pressure Agglomerates 236

Post-treatment Methods 241

Pressure Agglomeration Technologies 252

Low-Pressure Agglomeration 253 Medium-Pressure Agglomeration/Pelleting 266

High-pressure Agglomeration 300

Isostatic Pressing 373

Agglomeration by Heat/Sintering 385 Mechanisms of Sintering 385 Sintering Technologies 389

Batch Sintering 390

Continuous Sintering 397

Special Technologies Using the Binding Mechanisms of Agglomeration Coating 415 Separation Technologies 440

Gas/Solid Separation 440

Liquid/Solid Separation 442

Fiber Technologies 447

409

Engineering Criteria, Development, and Plant Design Preselection of the Most Suitable Agglomeration Process for a Specific Task 462 Laboratory Equipment, Testing, and Scale-Up Peripheral Equipment 492

453

468

Outlook 507

Bibliography 525 List of Books or Major Chapters on Agglomeration and Related Subject References 530 Author’s Biography, Patents, and Publications 531

Tables of Contents of Related Books by the Author

526

541

Indexes 543 List of Vendors 543 Wordfinder Index 580 Subject Index 591

I “I’

Dedication, Acknowledgements and References

When this book was first planned, the idea was to combine in one volume concise descriptions of the agglomeration phenomena, technologies, equipment, and systems as well as a compilation of the applications of agglomeration techniques in industry. The latter was intended to demonstrate the widespread natural, mostly undesired occurrences of the phenomena, including possibilities to avoid them, and discuss the varied old, conventional, and new beneficial uses of the technologies.

However, it soon became obvious that, in its entirety, this project became too vo- luminous and required much more time than anticipated. Therefore, it was decided to split the subject’s presentation into two volumes whereby both books will be “stand alone” publications that are also complementary.

The first volume, available here, covers the fundamental phenomena that define agglomeration as well as the industrial technologies and equipment for the size enlargement by agglomeration. Applications are mentioned in a general way throughout the text of this presentation but without going into details. These applications will be presented in a separate book entitled “Agglomeration Technologies - Industrial Ap- plications” that is scheduled for publication in 2003. A preliminary table of contents is given in Section 13.4.

Many persons, institutions, and companies have contributed to the two volumes of this book.

First and foremost, I wish to thank my wife Hannelore for her support and under- standing while, thorughout my professional career, I was compiling various papers and books (see Section 13.3). All are dedicated to her. Without my wife’s active parti- cipation in preparing almost all publications, in elaborating the textbook entitled “Size Enlargement by Agglomeration” [B.42], which is a major reference for this publication (see also below), and her, if sometimes reluctant, acceptance that I was not available for long hours on many days during almost four decades, the books, in particular, could not have been completed.

It is impossible to acknowledge all the help, extensive and small, that was provided by a large number of individuals and companies. In Section 14.1, a list ofvendors and other organizations is compiled which mentions those who have, in one way or another, contributed as well as some others who may be of interest as potential contacts for the readers of this book. While I have decided not to clutter the text with references, sources have been acknowledged if figures or tables were provided by or are based

Vlll Dedication, Acknowledgements and References

on information from particular companies. The Discialmer at the beginning of this book (see page IV) should be referred to when using such cross-references.

Regarding references to literature, Chapter 13 should be consulted. The earlier textbook “Size Enlargement by Agglomeration” [B.42] contains treatments as well as many references relation to the developing science of the unit operation and covers in some detail the sizing of and scale-up methods for agglomeration equipment. Since the emphasis of the new book is on practical considerations and industrial applications, not theory, the earlier book “Size Enlargements by Agglomeration” (Wiley, 1991) should always also be referred to. Information on the availability of reprints is available at the beginning of Section 13.1 and as a footnote later in the same Section.

Since Size Enlargement by Agglomeration is one of the unit operations of Mechan- ical Process Technology (see Chapter 1) and, for the design and construction of agglomeration systems of any kind, many or all of the other unit operations are required, together with the associated transport and storage technologies, often even in multi- plicity, and the analytical methods are applied for process evaluation and control, the reader who is interested in the topic of this book should also learn about or have access to information on the other fields of Mechanical Process Technology. This is also emphasized in Chapter 13. At this point I wish to acknowledge two books of general importance to which I have contributed chapters on agglomeration and ofwhich major portions were included in this book. They are: “Handbook of Powder Science and Technology” M. E. Fayed, L. Otten (eds,), 1st ed., Van Nostrand Reinhold Co., New York, NY (1983) and 2nd ed., Chapman & Hall, New York, NY (1997). Source references can be found in [B.21] and [B.56], Section 13.1.

Finally, I like to mention with gratitude the following individuals who, as profes- sionals and experts in their own fields, are or have been colleagues and/or partners in several continuing education courses over many years in the USA as well as in Europe. They have agreed that statements during their presentations and the elabora- tions for their course notes can be used directly, adopted, or modified for this book. They are, in alphabetical order: T. van Doorslaer, W. E. Engelleitner, M. E. Fayed, M. Gursch, D. C. Hicks, S. Jagnow, R. H. Leaver, R. Lobe, K. Masters, S. Mortensen, H. B. Ries, F. V. Shaw, J. Storm, R. Wicke, and R. Zisselmar.

For additional references and acknowledgements please refer to Sections 13.1 and 13.2.

I

Naples, November 2001 Wolfgang Pietsch

1

Introduction

In 1957, under the leadership of Professor Dr.-Ing. Hans Rumpf at the Technical University (TH) of Karlsruhe, Germany, Mechanical Process Technology or Particle Technology [B.11] was first introduced as a field of science in its own right. It com- prises the interdisciplinary treatment of all activities for the investigation, processing, and handling of solid particles as well as the interactions of such particulate solids. Four unit operations and associated techniques were defined (Fig. 1.1). Other common English names for this field of science, which was quickly adopted around the world, are Mechanical Process Engineering, Powder Technology, or Powder & Bulk Solids Technology.

Size enlargement by agglomeration is the generic term for that unit operation of mechanical process engineering which is characterized by “combination with change in particle size” (Fig. 1.1). The author of this book had the privilege to become one of the first assistants of Professor Rumpf. For several years he was responsible for the research and development of size enlargement by agglomeration at the Institute of

Fig. 1.1 of Mechanical Process Technology

Unit operations and associated techniques

Agglomeration Processes Wolfgang Pietsch

Cowriqht 0 Wilev-VCH Verlaq GmbH, Weinheim. 2002

2 7 Introduction

Mechanical Process Engineering and earned his PhD with a doctoral thesis on specific aspects of a binding mechanism [1.1] of agglomeration.

Webster’s Unabridged Third New International Dictionary [1.2] defines the verb agglomerate as: “to gather into a mass or cluster; to collect or come together in a mass; to collect into a ball, heap, or mass, specifically: clustered or growing together but not coherent”, and the noun agglomerate as: “a cluster of disparate elements; an indiscri- minately (= randomly) formed mass”. A technical dictionary [ 1.31 defines agglomeration as: “sticking or balling of (often very fine) powder particles due to short range physical forces. Therefore these forces become active only if the individual particles (forming the agglomerate) are brought closely together by external effects”.

These definitions distinguish the term size enlargement by agglomeration from the more general size enlargement such that particle growth occurring, for example, during crystallization or the production of particulate solids by melt solidification are not part of this unit operation of Mechanical Process Technology.

I

2

A Short History of Agglomeration

As a basic physical efect, agglomeration has existed since particulate solids were first formed on Earth. Binding mechanisms between solid particles cause the stability of wet and dry soil and (often under the influence of heat and pressure) participate in the development of rock formations. Sandstone is the most easily recognized “agglomerate”. Agglomeration as a phenomenon, e.g. the natural caking and build-up of particulate solids, must have been observed and has been used by higher developed organ- isms and later by humans since prehistoric times. Sea creatures covered themselves with protective coats, birds as well as other animals built nests, and humanoids formed artificial stones, all from various solids, sand, clay and different binders that were often secreted by the creature itself. As a “tool” to improve powder characteristics, agglomeration was used by ancient “doctors” in producing pills from medicinal powders and a binder (e.g. honey) or by food preparers during the making of bread from flour whereby the inherent starchy components act as binder.

In spite of this long “history”, agglomeration as a technology is only about 150 years old today (excluding small scale pharmaceutical and some little-known ancient, mostly Chinese applications as well as brick and bread making). Agglomeration as a unit operation, defined within solids processing, started around the middle of the nine- teenth century as a method to recover and use coal fines.

Agglomeration as a science is very young. It began in the 1950s with the formal definition of the binding mechanisms of agglomeration, interdisciplinary collection of knowledge relating to all aspects of agglomeration, and fundamental research which was no longer application oriented [B.42]. At approximately that time, the first recurring series of professional meetings were organized which were exclusively de- voted to the science and technology of agglomeration (International Briquetting As- sociation (IBA), - today Institute for Briquetting and Agglomeration (IBA) -, beginning in 1949 with biennial meetings and proceedings; International Symposia on Ag- glomeration, initiated in 1962 with proceedings, (see also Section 13.1)). Since that time, agglomeration science, technology, and use have experienced rapid growth but still without finding a corresponding awareness at institutions of higher learning and in the technical or process engineering communities.

This book is the second by the author on the general subject of size enlargement by agglomeration. While frequently referring to fundamentals and specifics which are



4 2 A Short History ofAgglomeration

covered in more detail in the first book [B.42], this new text tries to provide an updated, comprehensive summary of the state-of-the-art of agglomeration, its basics, technologies, and applications, at the beginning of the 21st century.

I

Agglomeration as a Generic, Independent, and Interdisciplinary Field of Science

As mentioned in the previous chapter, size enlargement of particulate solids by agglomeration is as old as the existence of solids themselves. Originally, agglomeration happened naturally during the development of soil, stone, and rock formations. Later, unwanted agglomeration occurred during handling and storage of particulate matter particularly when hygroscopic and/or soluble materials (such as salt) “set-up” into lumps or large, more or less solidified masses. In the animal world agglomeration was used to develop protective coatings (e.g. many marine worms, Fig. 3.1), to build nests (e.g. swallows, termites, Fig. 3.2), and to provide a nourishing and protective environment for the offsprings (e.g. dung beetles, Fig. 3.3).

Humans most probably first used agglomeration during the making of bread by taking flour (= particulate solids including an inherent binder, starch) and liquid additives (= additional binder for plasticity and “green” bonding), mixing and forming the mass, and, finally, “curing” the product, the removal of much of the moisture that was added during the mixing and agglomeration steps, to obtain structure and permanent bonding during baking. The technology of bread making combines all com-

Fig. 3.1 Protective agglomerated coating of a Rhizopod, a creping marine Protozoan (Difflugia urceolata)



6 3 Agglomeration as a Generic, Independent, and Interdisciplinary Field of Science I

Fig. 3.2a the bird’s saliva as a binder, and organic fibers for strengthening

Nest of swallows made by agglomeration from mud,

Fig. 3.2b animal’s excrements and/or secretions as binder

Nest of termites made from earth as well as the

1 7 3 Agglomeration as a Generic, Independent, and Interdisciplinary Field of Science

Fig. 3.3 “pelletizing” dung

Dung beetle, Scarabaeus Sacer,

ponents of a complex agglomeration process including preparation of solid feed particles by milling (= adjustment of particle size and activation of the inherent binder, starch), mixing of particulate solids with additional binder(s), forming the mass into a “green” agglomerate, and a “post-treatment” (curing = baking =heating and cooling) to provide strength and texture, Very early it was also found that the porosity of the final product could be modified (= increased) by making use of gases that are produced during fermentation (initiated by sour dough or yeast) and result in bubbles in the green mass. These voids are stabilized by “strengthening” the bread during post-treatment (baking).

For the construction of permanent shelter, humans may have observed the activities of animals that formed nests and protective “walls” from wet clay which hardened during drying (Fig. 3.2). By copying this behavior, wet clay, which was soon reinforced and made more water resistant by mixing-in straw or other fibrous material, was filled into a framework of wood branches and let harden during natural drying. To make building activities independent of the location of clay “mines”, during prehistoric times bricks were already produced from clay and sand and, after hardening, transported to building sites. Since fire was known for providing heat, the accidental “firing” of a piece of clay most probably resulted in the adaptation of an improved post- treatment that yielded waterproof bricks for areas where rock was not easily available, thus allowing the development of villages and, during the 4th millenium B.C. in Me- sopotamia, cities with large brick structures.

By experience, humans learned that certain natural materials helped cure specific illnesses. Minerals as well as dried animal and plant matter were ground to powder and “formulated” to yield medicines. Since powders cannot be easily consumed orally, natural binders, such as honey which, incidentally, also masked the unpleasant taste of

8 3 Agglomeration as a Generic, Independent, and Interdisciplinary Field of Science

some of the medicinal components, were mixed with the powder and the resulting plastic mass was rolled by hand into little balls (= pills). The sticky binder(s) caused pills to adhere to each other; therefore, it was soon found that coating the pills by rolling them in flour or pollen solved this problem (see also Section 10.1).

These three, well known ancient agglomeration techniques were used with little change through the ages of human history. Many other, lesser known and somewhat more recent processes could be added. However, it is not the objective here to produce a history book. Rather, these examples relating to three major modern “industries”, food, building materials, and health products, were selected to show that humans always lived with and used agglomeration. As a result, agglomeration technologies as all the other unit operations and associated techniques of Mechanical Process Tech- nology (see Fig. 1.1) were considered to be “normal activities” which, with the beginning of industrialization in the 18th and 19th centuries A.D., were merely mechanized by simulating what was done manually before. During these early modernization efforts it was not considered necessary to question the fundamentals of the processes and “improvements” were based on empirical developments.

Until very recently, agglomeration technologies had been developed independently in the particular industries in which they were applied. Because the process requirements are fundamentally different in such unlike industries handling, for example, coal and ores on one hand or food and pharmaceuticals on the other, no interdisciplinary contact and exchange of information took place. In fact, although agglomeration techniques developed along similar lines, application related “theories” were defined which were derived from investigations of specific requirements and their solutions together with a terminology that was often incomprehensible and, therefore, not useable by the “agglomeration expert” of another industry (see Chapter 4).

Agglomeration as a science began when an effort was made to interdisciplinarily combine the extensive knowledge that had been accumulated during sometimes hun- dreds of years in specific fields of human activities. This approach showed that (in alphabetical order, not indicating importance):

Baking: A thermal post-treatment process, does not only induce the development of final bonding, structure, and consistency in bread but produces similar characteristics during the heat curing of any “green” agglomerate.

Briquetting: Is not predominantly a technique for the enlargement of coal fines for beneficial use but equipment which was specifically developed for that application is also suitable for such diverse uses as, for example, the briquetting of salt for the re- generation of water softeners, the briquetting of flaked DMT to decrease the bulk volume and improve handling and shipping, the briquetting of frozen vegetable pulps to be used as rations for field kitchens, the hot briquetting of sponge iron to reduce this commodity’s reactivity and allow open handling and storage, or the production of fertilizer spikes and the manufacturing of artificial fireplace logs.

Coating: Is not only suitable for the modification of surface characteristics or the control of dispersion and dissolution of medicinal specialties but also to achieve similar properties in agrochemicals as well as human and animal foods, among others.

I

1 9 3 Agglomeration as a Generic, Independent, and Interdisciplinary Field of Science

Compacting: Is not only applicable for the production of “green” bricks or other ceramic bodies prior to firing but finds many uses in powder metallurgy or for the production of battery cathodes, etc.

Granulating: Is not primarily a method to improve flowability of powders and formulations in the pharmaceutical industry but also in the fertilizer and bulk chemical industries as well as for carbon black, silica fume, and many other materials.

Instantizing: As an example of a relatively new agglomertion process, is not limited to applications in the food industry for easily dissolvable drink and soup mixtures but is equally important for pigments, insectizides, fungizides, and many more.

Pelleting: Originally developed for the shaping of animal feed formulations by extrusion, is also applicable for the production of catalyst carriers and other materials requiring uniform size and shape together with relatively high porosity.

Sinteuing: When going back to the fundamentals of this process, was found to be not only a high temperamre process for the agglomeration of ores but, at much lower tem- peratures, also for plastics and other man made powders with low melting points or softening ranges, and, quite obviously, for powder metallurgy, mechanical alloying, or the like at many different temperature levels including extremely high ones for refrac- tory metals.

The above is only a small selection of the many diverse applications of particular agglomeration methods which, in all the different environments, follow the same fundamentals, apply the same rules, and use essentially the same equipment and systems if looked at from an interdisciplinary point of view. Although these facts become more and more known, there is still the understandable preconceived notion of, for example, somebody working in an ultraclean environment, such as the pharmaceutical, food, or electronic industries, that developments, expertise, and know-how gained in the “dirty” plants of, for example, minerals or metals production and processing, can not be considered as valid information that may be applied for the solution of a “clean” problem - and vice versa. In the case of “dirty” industries, a typical concern is that the often more deeply and completely investigated technologies originating in “clean” industries can not be applied because the production capacities are too small, the process may be batch, the equipment too complex, the execution and the materials of construction too expensive, etc., etc.

However, as will be shown among other topics in this book, methods for the selection of the most suitable agglomeration process for a specific application (see Section 11.1) are the same for all projects. While some requirements, for example in regard to equipment or system capacity, or on the shape, size, and special properties of the products, may result in the definition of “cleaner” or “more heavy-duty, rugged” processes already in the preselection phase, the normal approach is to determine the preferred method and/or technique by considering the fundamentals as well as an interdisciplinary pool of expertise and know-how first. Conditions of the particular application such as, for example, “hot and dusty large volume processing”, or the op- posite, “clean, small capacity operation with cGMP (= current Good Manufacturing Practice) and CIP (= Cleaning In Place) capabilities” are special design criteria that can be added to most of the systems later during the engineering phase.

10 3 Agglomeration as a Generic, Independent, and Interdiscip/inary Field of Science

Nevertheless, for manufacturing reasons and sometimes also because of special requirements on the company’s test facilities (see Section 11.2), some vendors spe- cialize in equipment for one or the other industry. This is a decision of convenience by the individual supplier and does not indicate the existence of a fundamentally different technology. In fact, techniques or apparatus that were developed for a specific industry can be adopted for use in areas with different environment and requirements while still maintaining the fundamental underlying principle as well as the general machinery and process. Examples are flaking (see Section 8.4.3), instantizing (see Section 5.4), spheronizing (see Section 8.3), and spray dryer agglomerators (see Sec- tions 7.4.3 and 7.4.4).

I

I ”

4

Glossary of Agglomeration Terms

Newly developing fields of science are organized according to universally recognized classifications using well-defined terms to describe the fundamentals, correlations, equipment, procedures, and processes. This is not the case for those technologies that were known for centuries and have been developed empirically and independently for different applications (see also Chapters 2 and 3). In such cases the same process, procedure, activity or piece of equipment may have different names in different industries or the same term may have different meanings in different fields of application.

The earlier book “Size Enlargement by Agglomeration” [ B.421 contained already a glossary of agglomeration terms. In the following this glossary is repeated and updated. Although the author and many others that are active in the promotion of “agglomeration” are trying to use scientific and technical terms consistently in an interdisciplinary manner (terms shown bold), it is still helpful to also explain some of the more common names and expressions including a few historical ones. In the following, crossreferences are indicated by italic letters. The same and many more “agglomeration terms”, the latter mostly descriptive and/or trade names, are mentioned and used in the text of the book. Sections 14.2 and 14.3 help locate these words and expressions.

Abrasion [n.] Removal of solid matter from the surface or edges of an agglomerate. The matter removed is much smaller than the agglomerate itself. (See also attrition, erosion.) Measure for the ability of a body, for example an agglomerate, to withstand abrasion. The process of growth or enlargement by a gradual build- up, such as: increase by external addition or accumulation, for example by adhesion of external parts or particles. (See also agglomeration, aggregation, build-up.) To heap up into a mass; pile up. The action or process of accumulating; an accumulated mass, quantity, or number. A sticking together of solids. The molecular attraction exerted between the surfaces of solids. Distinguished from cohesion.

Abrasion resistance

Accretion [n.]

Accumulate [vb.] Accumulation [n.]

Adhesion [ n.]

2

A Short History of Agglomeration

As a basic physical efect, agglomeration has existed since particulate solids were first formed on Earth. Binding mechanisms between solid particles cause the stability of wet and dry soil and (often under the influence of heat and pressure) participate in the development of rock formations. Sandstone is the most easily recognized “agglomerate”. Agglomeration as a phenomenon, e.g. the natural caking and build-up of particulate solids, must have been observed and has been used by higher developed organ- isms and later by humans since prehistoric times. Sea creatures covered themselves with protective coats, birds as well as other animals built nests, and humanoids formed artificial stones, all from various solids, sand, clay and different binders that were often secreted by the creature itself. As a “tool” to improve powder characteristics, agglomeration was used by ancient “doctors” in producing pills from medicinal powders and a binder (e.g. honey) or by food preparers during the making of bread from flour whereby the inherent starchy components act as binder.

In spite of this long “history”, agglomeration as a technology is only about 150 years old today (excluding small scale pharmaceutical and some little-known ancient, mostly Chinese applications as well as brick and bread making). Agglomeration as a unit operation, defined within solids processing, started around the middle of the nine- teenth century as a method to recover and use coal fines.

Agglomeration as a science is very young. It began in the 1950s with the formal definition of the binding mechanisms of agglomeration, interdisciplinary collection of knowledge relating to all aspects of agglomeration, and fundamental research which was no longer application oriented [B.42]. At approximately that time, the first recurring series of professional meetings were organized which were exclusively de- voted to the science and technology of agglomeration (International Briquetting As- sociation (IBA), - today Institute for Briquetting and Agglomeration (IBA) -, beginning in 1949 with biennial meetings and proceedings; International Symposia on Ag- glomeration, initiated in 1962 with proceedings, (see also Section 13.1)). Since that time, agglomeration science, technology, and use have experienced rapid growth but still without finding a corresponding awareness at institutions of higher learning and in the technical or process engineering communities.

This book is the second by the author on the general subject of size enlargement by agglomeration. While frequently referring to fundamentals and specifics which are



12 4 Glossary of Agglomeration Terms

Agglomerate [vb.]

Agglomerate [n.]

I

Agglomeration [n.]

Agglomerator [n.]

Aggregate b.1

Aggregate [vb.] Aggregation [n.]

Agtation [n.]

Agitator [n.] Ammoniation [n.]

Angle of repose

Angle of compaction Anticaking agent

Apparent density

Atomizer [n.] Atomizing [vb.] Attrition [n.]

Auger [n.] Axial extruder

To gather (particulate solids) into a ball, mass, or cluster. (See also aggregate.) An assemblage of particles which is either loosely or ri- gidly joint together. Particles adhering to each other. (See also conglomerate.) The action or process of gathering particulate solids into a conglomerate. Specific equipment in which agglomeration is accom- plished. Any of several hard, inert materials (as sand, gravel, rock, slag) used for mixing with a binding material to form concrete, mortar, plaster or, for example, road sur- facing products. Also: A mass or body of units or parts somewhat associated with one another. To collect or gather into a mass. (See also agglomerate.) A group, body, or mass composed of many distinct parts or individuals; the collection of units or parts into a mass or whole; the condition of so collected. (See also agglomerate, aggregate, cluster, agglomeration, accretion, build-up.) Changes in characteristics ofparticulate solids or agglorn- erates that occur naturally with time. (See also post-treatment.) A state of movement of particulate solids and/or fluids induced by external effects or forces. See mixing tool, intensijer bar. The formation of fertilizer granulates using ammonia to obtain chemical modification and bonding. The basal angle of a pile of powder that has been freely poured onto a horizontal surface. See nip angle. Liquid or solid matter applied to the surface of, for example, agglomerates that prohibits sticking or growing together. (See also caking.) The weight of the unit volume of a porous mass, for example, an agglomerate. See nozzle. Finely dispersing liquids. The unwanted break-down of agglomerates. (See also abrasion, erosion.) See screw. Low, medium, or high pressure extruder with a flat die plate at the end of a barrel; the material is extruded in the same direction as it is transported by the screw(s).

4 Clossaty of Agglomeration Terms

During the flow of particulate solids, reverse movement of some particles due to their stochastic motion caused by turbulence or special equipment design. Typical in the fertilizer industry; unwanted agglomeration of particulate solids in a closed bag during storage. Mostly caused by recrystallization of dissolved materials. Synonymous with spherical agglomerate. (See also pellet.) Typical in the iron ore industry; the capability of particulate solids to form more or less spherical agglomerates during growth agglomeration. Originally in the iron ore industry; any method producing spherical agglomerates by tumble or growth agglomeration. (See also pelletizing.) Cylindrical (or sometimes tapered) housing for screws, e.g. offeeders or extruders. Low pressure extruder in which the die plate resembles a basket, using rotating or oszillating extrusion blades. Formation of bead-like particles; typical in solidification of melt droplets. (See also prilling, pastillation, melt solidijcation.) A container, box, frame, crib, or enclosed volume used for storage. (See also hopper, silo.) An inherent component of or an additive to particulate matter providing bonding between the disparate particles. Physical and chemical effects that cause adhesion and bonding between solid surfaces. See Section 5.1, Tab. 5.1 and Fig. 5.8. Organic plant and animal residuals. Often organic waste material that is especially used as a source for fuel. See extrusion blade. Typical in the ceramic and fertilizer industries; double shafted pug mill. SeeJluid bed. The process of binding particles together by the action of binding mechanisms. A vertical or inclined, cylindrical, conical or convex vessel enclosing and defining the operating volume of some coaters, mixers, spheronizers, etc. Unwanted arching of solid matter in a converging discharge chute or cone. Prohibits discharge of particulate solids from containers or chutes. Also briquet; agglomerate produced and shaped by high- pressure agglomeration. (See also compact, tablette.) Also briquetting machine; equipment that produces briquettes.

Backmixing [n.]

Bag set

Ball [n.] Ballability [n.]

Balling [n.]

Barrel [n.]

Basket extruder

Beading [n.]

Bin [n.]

Binder [n.]

Binding mechanism

Biomass [n.]

Blade [n.] Blunger [n.]

Boiling Bed Bonding [n.]

Bowl [n.]

Bridging [n.]

Briquette [n.]

Briquetter [n.]


Briquetting [n.] Brittleness [n.]

I

Build-up [n.]

Bulk density

Capillary [adj .] Capping [n.]

Cake [n.] Caking [n.]

Cement [n.]

Cement [vb.] Cementitious [adj.] Channel [n.]

Chelate [adj.]

Chelate [n.] Chopper [n.] Clam shelling

Closed pore

Cluster [n.]

Clustering [n.]

Coalesce [vb.]

The process of forming briquettes or compacts. The tendency of particles or agglomerates to break down in size easily. (See also friability.) The unwanted coating of surfaces with particles which adhere naturally due to their fineness and/or inherent binding mechanisms. The weight of the unit volume of a particulate mass under non-specific condition, e.g. in storage or in a shipping container. (See also density.) Describing full liquid saturation. Separation of a thin layer from the face(s) of compacts during decompression. Defect in tablettes caused by the recovery of elastic deformation and/or expansion of compressed air. See sheet; typical in fertilizer applications. Unwanted agglomeration during storage mostly by recrystallization of dissolved materials. (See also bag set.) A powder of alumina, silica, lime, iron oxide, and mag- nesium oxide burned together in a kiln, finely pulver- ized, and used as an ingredient of mortar and concrete. Also any mixture used for a similar purpose. (See also pozzolan.) To unite or make firm by or as if by cement. Having the properties of cement. Open ended compacting tool set for high pressure extrusion in a ram press; also any elongated opening through which material is extruded. (See also pressway.) Relating to, producing, or characterized by a cyclic structure usually containing five or six atoms in a ring in which a central metallic ion is held in a coordination complex by one or more groups each of which can at- tach itself to the central ion by at least two bonds. To combine with a metal to form a chelate ring or rings. See h i v e head. Opening of the leading or trailing edge of briquettes discharging from roller presses; one-sided splitting along the web. Also duck billing, oyster mouthing. A pore not communicating with or connected to the surface of a porous body. A number of similar individual entities that occur together. (See also accretion, agglomerate, aggregation.) The growing together of primary agglomerates to form larger entities. (See also satellites formation.) To unite by growth.

4 Glossary of Agglomeration Terms

A growing together or union in one body, form, or group. (See also growth agglomeration.) Molecular attraction by which the particles of a body (e.g. agglomerate) are united throughout the mass whether like or unlike. Distinguished from adhesion. Applying a layer of material, a film, or a finish to a sub- strate; in agglomeration, application of a layer of solids to a particulate unit. Specially shaped p a n in which a material layer is applied on agglomerates (such as tablettes) usually in the pre- sence of liquid, heat, or both. Typical in the pharmaceutical and food industries. A binding process that occurs at ambient or low tem- peratures and uses the cementitous or pozzolanic reac- tions of many hydroxides; often assisted by pressure. An object of specific size and shape produced by the compression of particulate matter. Synonymous with briquette. A state of particulate solids in which individual particles are closely packed. Distinguished from discrete dispers. See compressibility. Also compaction. The method of producing sheet. The part or parts making up the confining form in which a powder is pressed. Synonymous with die. The normally dry methods of obtaining granular products by crushing and screening compacts and/or sheet into granulate. Consisting of two or more separate materials whereby each retains its own identity. The capacity of a particulate matter to be compacted. Compressibility may be expressed as the pressure or force to reach a required density or, alternately, the density at a given pressure or force. Synonymous with compactibility. The ratio of the volume of loose particulate matter in a die to the volume of the compact made from it. Synon- ymous withjll ratio. In low and medium pressure extruders, the total thickness of material that is under compression in a die (including any inlet chamfer) divided by the nominal hole diameter. Development of special characteristics of particulate solids by, for example, treatment with steam, kneading, heating, etc., or surface treatment by, for example, anticaking agents. Pan with relatively high conical rim.

Coalescence [n.]

Cohesion [n.]

Coating [n.]

Coating pan

Cold bonding

Compact [n.]

Compact disperse

Compactibility [n.] Compacting [n] Compacting tool set

Compactionlgranulation

Composite [adj.]

Compressibility [n.]

Compression ratio

Conditioning [n.]

Cone agglomerator


Conglomerate [n.] I

Contact point Coordination number

Core rod

Coufinhal press

CUP b.1 Curing [n.]

Cut size

Decrepitation [n.]

Densification [n.] Density [n.]

Deposit [n.] Die In.]

Die plate

Disc [n.] Discrete dispers

Dispers [adj.] Dispersibility [n.]

Distribution plate

Doctor blades Dome extruder

Double action pressing

An adhering mass of particles made up of parts from different sources or of various kinds. (See also agglomerate.) Area at which two particles touch each other. Sum of all near and contact points of a particle with surrounding particles in a structure made up of particulate solids, for example an agglomerate. Member of the compacting tool set that forms a through hole in the compact. (See also mandrel.) Punch-and-die press with multiple die sets on an indexed table for making large (e.g. coal) briquettes. (No longer used.) See pocket. Induration ofgreen agglomerates by any method. (See also post-treatment.) The actual value at which separation of a particle size distribution into “coarse” and “fines” has taken place. Breakdown in the size of particles or agglomerates due to internal forces, generally induced by heat. The act or process of making dense. Mass per unit volume of matter at specific conditions. For example: apparent, bulk, or true densities. A (natural) accumulation of particles. Member of the compacting tool set that forms the peri- phery of the part being produced. Also open ended channels for extrusion. Plates, rings, or other machine parts with perforations for extrusion. (See also die.) See pan. A state ofparticulate solids in which individual elements can be clearly distinguished. Distinguished from compact dispers. See particulate. Measure for the ease with which, under specific conditions (e.g. in liquids), an agglomerate breaks down into primary particles. Perforated plate at the bottom of aJuid bed through which fluidizing gas enters from the plenum. (See also gil plate.) See scraper. Axial, low pressure extruder, most often with two screws, in which the die plates resemble domes. A method by which particulate solids are pressed between opposing punches which are both moving relative to the die.

1 1 7 4 Glossary of Agglomeration Terms

Downward flow of gas, for example through a particle bed. Slowly rotating, slightly inclined drum for growth agglomeration. See compaction/granulation. See clam shelling, oyster mouthing. In compacting, time during which certain process conditions, for example pressure, persist or are held constant. Typically used as microencapsulation. The gradual wearing away of an agglomerate by the pro- gressive removal of small pieces of material. (See also abrasion.) Diameter of immaginary monosized spherical particles which feature the same property as the particulate mass to be characterized. For example: surface equivalent diameter. Increase in volume of, for example, an agglomerate after production or during post-treatment. Converse of shrink- age. See ram extruder. Product of extrusion. (See also pellet.) Machinery for the production of extrudates. (See also screw and ram extruder.) The formation of (often cylindrical) agglomerates by for- cing a “plastic” mass through open ended channels or holes in (perforated) dies. In low pressure extruders, the flat, curved, or engineered blade that pushes material through the openings of a die plate; it is the part closest to the die plate. Device to deliver feed material to a processing unit. (see also force feeder.) Element@) providing forces onto particulate solids in a

feeder. (See also screw.) Typically used in tabletting or other confined volume compression equipment. Synonymous with compression ratio. See sheet. Also: 1. Grains or other malleable particles flattened between smooth rollers. 2. Material solidified from a melt on a rotating, cooled drum (flaker) and removed by scrapers. A primary crusher (often two rollers with teeth) used to reduce the size of sheet. See web. A continuous or semi-continuous spiral flat plate that is attached to the shaft of a screw.

Downdraft [n.]

Drum agglomerator

Dry granulation Duck billing Dwell time

Encapsulation [n.] Erosion [n.]

Equivalent diameter

Expansion [n.]

Exter press Extrudate [n.] Extruder [n.]

Extrusion [n.]

Extrusion blade

Feeder [n.]

Feed screw

Fill ratio

Flake [n.]

Flake breaker

Flashing [n.] Flight [n.]

18 4 Glossary of Agglomeration Terms I Floc [n.]

Flocculant [n.] Flocculate [vb.]

Flocculation [n.] Flocculent [adj.]

Fluid bed

Fluid bed agglomeration Force feeder

Fraction [n.]

Fragmentation [n.]

Friability [n.]

Friction plate

Funicular [adj.]

Gap b.1

Gear pelleter

Gil plate

Globulation [n.] Granular [adj.]

Granulate [n.]

Aflocculent mass formed by the aggregation of a number of fine suspended particles. A flocculating agent. To aggregate or coalesce into small lumps or loose clusters or into aflocculent mass or deposit. The act or process offlocculating. Containing, consisting of, or occurring in the form of loosely aggregated particles or soft flocs. Also fluidized bed. A bed of particles in which the particulate solids are kept in suspension by forces caused by an upward flowing fluid. Growth agglomeration in afluid bed. A feeder that provides forces onto particulate matter by, for example, the action offeed screws. That portion of a sample of particulate solids which is between two particle sizes (see cut) or in a stated range (e.g. fine, coarse, etc.). The process whereby a particle (or agglomerate) splits into usually a large number of smaller parts with a range of sizes. The tendency of particles to break down in size during storage and handling. (See also brittleness.) In spheronizers, a circular flat disc with a rough surface or uniformly spaced grooves which rotates inside a cylindrical bowl. Describing the transitional liquid saturation. In pressure agglomeration, the distance between the surfaces of compacting tool sets; specifically: in extrusion, the distance between the pressure generating device and the die plate, in roller presses, the closest distance between the rollers. Double-roll pellet mill in which the rollers are in the shape of coarse, intermeshing gears with bores at the root sections between the gear teeth. (Also gear pelletizer.) Distribution plate in which the perforations are manufac- tured such that they produce a directional flow of gas. See melt solidijication. Present as particles in “grain” shape and size. Coarsely particulate. Also Granule. From Latin granula = grain, particle. Any kind of relatively coarse particulate matter. In size enlargement, synonymous with agglomeration to a size range of between approx. 0.1 and 10 mm. In size reduction, synonymous with crushing into approx. the same size range. Granulate is normally considered dustfree, free flowing, and non-segregating.

4 Glossary of Agglomeration Terms

Producing a granular solid matter; possible by size enlargement (agglomeration, melt solidijcation [pastillation, prilling], and crystallization) or by size reduction (crushing). (See also compaction/granulation.) A general term for the production of solids in granular form by either size reduction or size enlargement. As in “green agglomerate”, “green pellet”, etc., means fresh, moist, uncured, etc. In spheronizers, the design (size and shape) of the grooves on the fnction plate surface. An increase in dimension by for example agglomeration or crystallization. (See also coalescence.) See coalescence, tumble agglomeration. See sintering. In batch processing, for example agglomeration, a per- centage of the previous batch retained in or returned to the processing vessel. The funnel or chute that stores material and/or directs it into equipment. (See also bin, silo.) Granulation of a hot melt of e.g. urea or ammonium nitrate in a pan. The simultaneous heating and molding of a compact or briguetting of hot material. Selective agglomeration of particles suspended in a liquid by adding an immiscible binder during agitation. (See also oil agglomeration.) Strengthening of green agglomerates, mostly by heat. Non-cylindrical pore with varying diameter; particularly a pore with narrow entrance followed by a large, internal volume. Quickly soluble. Characteristic as, for example, in “instant coffee”. Producing agglomerated products with instant characteristics, i.e. material exhibiting, as compared with the untreated powder, particularly high solubility, even in cold liquids. In high shear mixers and agglomerators, an independently driven bar, rotating with high speed, usually car- rying mixing tools and, sometimes means for atomizing liquid binder, that extends into the particulate mass to be mixed and causes an additional turbulent motion of the particles. (See also knive heads.) A network of contiguous pores in and extending to the surface of a porous body, e.g. agglomerate.

Granulate [vb.]

Granulation [n.]

Green [adj.]

Grid [n.]

Growth [n.]

Growth agglomeration Heat bonding Heel [n.]

Hopper [n.]

Hot melt agglomeration

Hot pressing

Immiscible binder agglomeration

Induration [n.] Inkbottle pore

Instant [adj.]

Instantizing [n.]

Intensifier bar

Interconnected porosity

20 4 Glossary of Agglomeration Terms I

than 3 mm, by growth agglomeration. (See also pelletizing.)

Interface [n.]

Isostatic pressing

Knive head

Land area

Leading edge

Lower punch

Low pressure extruder

Lubricant [n.]

Lump [n.] Mandrel [n.]

Marum [n.]

Marumerizer [n.] Mechanical alloying

Medium pressure extruder Melt solidification

Microencapsulation [n.]

Micropelletizing [n.]

A plane or other surface forming a common boundary of two bodies or spaces. The densijication of a particulate mass by subjecting it to nominally equal pressure from every direction. In high shear mixers and agglomerators, independently driven high speed rotating tools which extend into the particulate mass and cause additional turbulent motion of the particles as well as desagglomeration in mixing and controlled destruction of agglomerates in agglomeration. (See also intensijier bar.) The area surrounding briquette pockets on the roller surface of briquetters. (See also fiashing, web.) During briquetting in roller presses the forward edge of a discharging briquette. A member of the compacting tool set that determines the powder fill level and forms the bottom of the part in a punch-and-die press. Extruder in which the die plates consist of screens or thin, perforated sheets and exert small frictional resistance during extrusion. An agent mixed with or incorporated into particulate matter or applied to the tooling to facilitate pressing and ejection of a compact, tablette, or extrudate. See second meaning of aggregate. Also mandril. A metal bar that serves as a core around which material may be bent, cast, forged, molded, or otherwise shaped. (See also core rod.) Sometimes used to describe a particle which has been spheronized. See spheronizer. Original (Japanese) name. A technology of powder metallurgy by which powders of metals, that cannot be combined in molten stage, are mixed and compacted to form the alloy. See pellet mill. A method by which molten substances are converted into particulate solids by cooling droplets of the melt. (See also beading, pastillation, prilling.) A method by which small portions of liquids, particulate solids, or gases are enclosed by a shell (membrane, capsule) to form a dry, free flowing product often with spherical particle shape. The capsule shell may provide specific product characteristics (e.g. dispersibility, solubility). The formation of small agglomerates, usually not larger

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Agglomeration Processes...1 Introduction In 1957, under the leadership of Professor Dr.-Ing.Hans Rumpf at the Technical University (TH) of Karlsruhe, Germany, Mechanical Process Technology