Thickening in the 20th century: a historical perspective

This paper reviews the development of thickening theory and practice during the 20th century. It starts with the early design of the Dorr thickener and describes the progress made in understanding the process in the laboratory and in the plant. The major contributions of Coe and Clevenger, Comings and Kynch are given in detail and the recent developments by several authors, leading to the phenomenological theory of sedimentation, are presented from the authors’ perspective. The known methods of thickener design are mentioned, and the contribution of the authors in this matter is expressed in detail. Finally, some new research and developments, such as high-capacity high-density thickeners and new tools to study and design thickeners, are indicated.