Technological behavior of spray dried bodies for porcelain stoneware slabs.

The firing behavior of porcelain stoneware slabs depends not only on kiln conditions (time, temperature) but also on the rheological characteristics and the response to compaction of spray-dried powders. Although in the literature there are information on the characteristics of spray-dried powders for ceramic tiles, no data are available on bodies for manufacturing large slabs (>4 m2) with new technologies. A systematic approach to the properties and behavior of nine industrial spray-dried powders for porcelain stoneware slabs was set out by the IPERCER project. In addition to the rheological properties of powders and their compaction behavior, it has been carefully observed the firing behavior (effect of the porosity and density of the green on the firing shrinkage, bulk density, open and closed porosity, phase composition), trying to correlate among them all the data collected. Main goal is to obtain a data-based model of the sintering behavior and to optimize the characteristics of fired slabs in terms of homogeneity (shrinkage), bulk density, water absorption, porosity and mechanical strength. Concluding, with an overall analysis of the entire ceramic production process, we infer the chance of improving the performance of spray dried bodies by finding a compromise between powder flowabity, compaction and densification during firing. Final challenge is to transfer this progress to the management of industrial spray driers.