Determinação do calor necessário para a queima da porcelana

Abstract

In the present work, part of the results obtained in the study of the Ribáuè-feldspar kaolin system of Carapira-sands of Marracuene is used to test a procedure for calculating the heat required for porcelain firing. A review of the existing literature shows that this thermodynamic quantity has already deserved special attention in the case of the production of glass and cement, while in the case of porcelain, little or nothing has been described; this may apparently be due to the greater difficulty in experimentally determining this magnitude in the case of porcelain. The experimental determination of this quantity for glass and cement has been carried out by means of calorimetry. The use of an identical procedure for porcelain would not have good results, due to the long firing periods practiced in porcelain production and the fact that the composition of the final product varies a lot with the chosen firing cycle. In order to calculate this quantity it is necessary to correctly define the initial state and the final state and link the two states by means of thermochemical equations (real or hypothetical). To define the initial and final states, X-ray fluorescence methods were used to determine the chemical composition and X-ray diffraction and rational analysis to determine the mineralogy of the raw materials and the final product. The connection of the initial and final states was made considering the transformation - quartz (a) into quartz (P), the conversion of kaolinite into mullite and the fusion of feldspar. The dissolution of quartz(p) and the dissolution of mullite were also considered. The mixing heats of sodium and potassium feldspars were not considered.(TRADUÇÃO NOSSA)