Flash- and CFB calciners, history and difficulties of development of two calcination technologies

Abstract

In the last 40 years, stationary calciners have permanently replaced rotary kilns in existing alumina refineries and are being installed in all new Greenfield alumina refineries producing smelter grade alumina. In the 1960‘s two separate and different approaches to stationary alumina calciners were going through research and development. Alcoa developed a fluid flash system and VAW, together with Lurgi (today Outotec) the Circulating Fluid Bed (CFB) calciner. Both developments had the same targets, but took different approaches to create more efficient calcination systems. Without any joint effort, the industrial stages of both developments were introduced to the industry at the same time. This paper describes the significant steps of the development that both calcination systems went through to reach an industrial stage and the risks and failures that both took. Furthermore the differences and common goals of both approaches are analyzed and described.