The author, Dr. Eugene Barsky, has been engaged in this subject for 18 years, since 1993. His M.Sc. thesis completed in 1998 was devoted to the development of models of cascade separation of solid materials in flows. His PhD thesis completed in 2001 was devoted to the development of entropy criterion of separation processes optimization. Among dozens of criteria applied, the entropy criterion has proved to be the most unbiased one. Since that time, the author has been developing these topics in depth. He created a number of industrial cascade apparatuses for powders separation and dust collection, wrote about 20 articles, published two books, participated in many scientific congresses and conferences. The material accumulated during 6 recent years is presented in the proposed book.