Rotary reactors or rotary kilns are the reactors facilitating the chemical reaction between the gas and solid phases usually at high temperatures. This book, which is written by an expert in the field, describes the principles of the rotary reactor and the mode of its operation. These reactors are widely used in various chemical process industries (food, pharmaceuticals) and metallurgical industries. The book defines the physiochemical aspects of the rotart reactors and provides theoretical equations of their operation.The first part of this book presents the fundamentals; solid movement, conversion of solids, and heat transfer. The middle part of the book applies these equations to a variety of processes which have been developed so far, and shows how they are used. In its last part, conceptual designs of novel rotary reactors are proposed, which performance characteristics are predicted on the basis of above equations, especially, in gasification of solid wastes. This book defines the rotary reactors and their mode of operation. It defines all operating parameters and gives equations to predict the operation of rotary reactors under various conditions. It includes a number of practical examples from various industrial applications (metallurgical waste treatment etc).