Calcium carbonate decomposition in white-body tiles during firing in the presence of carbon dioxide

This study examines the thermal decomposition process of the calcium carbonate (calcite powder) contained in test pieces of porous ceramics, of the same composition as that used in manufacturing ceramic wall tile bodies, in the presence of carbon dioxide, in the temperature range 1123-1223 K. The experiments were carried out in a tubular reactor, under isothermal conditions, in a gas stream comprising different concentrations of air and carbon dioxide. Assuming that the relationship between the molar concentrations of CO2 on both sides of the gas-solid interface in the test pieces was conditioned by an equilibrium law of the form c(QS)(S) = b.c(QS)(G), the equation proposed in a previous paper was modified to correlate the results obtained when the experiments were conducted in the presence of carbon dioxide. The modified equation fitted well to the experimental data obtained in the temperature and carbon dioxide concentration ranges studied. The knowledge derived from this research has enabled the firing cycle used in the single-fire manufacture of this type of wall tile to be optimised. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved.