Some Basic Principles of Industrial Practice

All practical emulsion applications or problems tend to have in common the same basic principles of colloid science that govern the nature, stabihty, and properties of emulsions. The widespread importance of emulsions in general, and scientific interest in their formation, stability and properties, have precipitated a wealth of published literature on the subject. This chapter provides an introduction and overview. A number of books provide very useful introductions to the properties, importance, and treatment of emulsions [1-5] in industry. Most good colloid chemistry texts contain introductory chapters on emulsions [6-9], while for much more detailed treatment of advances in specific emulsion areas the reader is referred to some of the chapters available in specialist monographs and encyclopedias [10-12]. 

Elucidation of how the general principles underlying the concept of validation should be expressed in practice is an evolving process, as exemplified by the ongoing evolution of validation requirements for bioanalytical assays in the pharmaceutical industry (Shah 1992, 2000 FDA 2001 Viswanathan 2007). The complementary principle of fitness for purpose (Section 9.2) applies not only to the assay method but also to the validation process itself. Procedures that are considered to be fit for purpose in validation of an analytical method to be used in drug development, for example, need not necessarily apply to, e.g., methods used to screen pesticide residues in foodstuffs. As noted in Section 9.2, this point of view appears to be consistent with the definition of validation applied to all measurements (ISO 1994) Validation Confirmation by examination and provision of objective evidence that the particular requirements for a specified intended use are fulfilled. Of course, some basic principles are common to all validation schemes. 

This chapter contains a discussion of two intermediate level problems in chemical reactor design that indicate how the principles developed in previous chapters are applied in making preliminary design calculations for industrial scale units. The problems considered are the thermal cracking of propane in a tubular reactor and the production of phthalic anhydride in a fixed bed catalytic reactor. Space limitations preclude detailed case studies of these problems. In such studies one would systematically vary all relevant process parameters to arrive at an optimum reactor design. However, sufficient detail is provided within the illustrative problems to indicate the basic principles involved and to make it easy to extend the analysis to studies of other process variables. The conditions employed in these problems are not necessarily those used in current industrial practice, since the data are based on literature values that date back some years. 

To be sure, the economic pressures on the perfumery industry are becoming such that we can no longer afford not to use all approaches that can make our work more efficient, even those that are, like the systematic prediction of performance, far from perfect at present. We will therefore briefly present this approach here, outlining its principles and giving some practical examples in this chapter, and providing basic theoretical background in Chapters 16 through 18. 

---