Raw clays processing for ceramic pastes

F. Durão, T. Carvalho*, L. Cortez, C. Pires, R. Lourenço, A. Felício,
I. Rodrigues and C. Tareco

C.V.R.M. – Centro de Geo-sistemas, Instituto Superior Técnico, Av. Rovisco Pais,
1049-001 Lisboa, Portugal


Received 11 October 2002; accepted 27 July 2004



ABSTRACT

Ceramic products are mainly produced with clays supplied by mineral industry, that have in general very heterogeneous compositions. In order to cope with industrial requirements, producers must apply a controlled blending policy of the different geological formations, which can lead to the rejection of a large percentage of reserves. An alternative solution is the use of processing plants. However, clays are hard to process materials, mainly due to their ultra fine grain sizes. So, the development of a suitable processing flow sheet is always a challenging task.

This paper presents the results of an experimental research study of beneficiation of two raw clays from a large deposit in Spain. The objective of the study was to improve the physical and technological properties of the ceramic pastes by reducing the colouring elements (mainly iron and titanium minerals) in the raw clays. This target was achieved by screening, hydrocycloning and froth flotation. A column flotation was used with very good results in the beneficiation of one of the raw clay types. The research study was divided in two parts: laboratory scale tests leading to the establishment of a suitable flotation chemical environment, followed by pilot scale tests. A final flow sheet was developed and the data for scaling up to an industrial plant was acquired. The complex column flotation process was controlled by means of a sophisticated controller based on fuzzy logic inference.



Keywords: Fine particle processing; Froth flotation; Flotation column; Process control; Fuzzy logic inference



* Corresponding author
   E-mail : teresa.carvalho@ist.utl.pt