TABLE OF CONTENTS It was assumed in the last chapter that colliding spherical particles coalesce instantaneously to form larger spherical particles. There is, however, an important class of problems involving the formation of agglomerates composed of much smaller solid particles, known as primary particles, that usually range from a few nanometers to about 0.1 ?m in diameter. The factors that control the size of the primary particles during their synthesis are discussed in Chapter 12. The primary particles generated by industrial or natural processes are almost always polydisperse; in theoretical analyses of agglomerates composed of such particles they are assumed to be monodisperse. The agglomerates may range in size from about 100 nm to several microns.
Agglomerates appear in emissions from sources such as diesel engines, smelters, and pulverized coal combustion and in the commercial production of fine particles (for example, the synthesis of silica and titania). Particulate emissions from pulverized coal combustion and incineration often have two modes in the mass distribution function. The coarse mode larger than a few microns in diameter consists of fragments of the original inorganic ash. The fine mode is often composed of agglomerates of ultrafine particles resulting from selective volatilization of certain components of the original ash. As shown in this chapter, the agglomerate size distribution is a very sensitive function of agglomerate structure and process conditions.
This chapter starts with a review of methods of characterizing agglomerate structures. Next we discuss the dynamics of agglomerate size distributions driven by collisions resulting from the...
