(36d) Drying in a Fluidized Bed of Inert Glass Spheres

Drying of bulk materials takes a large place in a lot of industrial processes. Unfortunately spray drying processes cannot always be used because of the high viscosity of suspensions. In order to decrease their viscosity and in order to improve their stability it is necessary to avoid the agglomeration of particles and to enhance their deflocculation. Recent works carried out in the chemical engineering department of the Compiègne University of Technology have put across the development of a new process of filtration of mineral suspensions using dispersant agents in order to obtain concentrated and easily fluidifiable final cake (= concentrated suspensions). Using this process the mechanical dehydration can lead to pulverizable concentrated suspensions which can be dried by thermal dehydration (atomization). This paper deals with the development of a drying process for this type of highly concentrated suspensions, leading to a lower cost production of the dried powder and a better control of its manufacturing process and its final characteristics. The process relies on the suspension atomization in a fluidized bed of inert particles (glass spheres). The sprayed suspension gets stuck with the heated particle surface. This suspension coating dehydrates and peels off from the glass spheres because of the interparticle friction. Then the dried powder is conveyed by the fluidization air to a filter (reverse jet bag house) to be collected. Characterization of initial concentrated suspensions and final powders will be studied as well as the interest of the process by an energetic point of view.