Gas generation during Cypris clay expansion

Abstract

Our research focuses on clay expansion gases measurements that can be used for optimisation of expanded clay materials production. In the paper we present analysis of gases generated by clay thermolysis which play critical role in quality of the industrial materials produced by bloating clay in the heat. As different expansion gases are released at different volumes and under different temperatures, detailed knowledge of this process is needed for proper set-up of the production facility—the rotary kiln. The aim of our work was to measure selected expansion gases at temperatures below 1200 °C focusing on factors that are critical for proper clay expansion process. Using clays from the overburden of the two open-pit mines in West Bohemia we show that the major gaseous components that determine clay expansion (carbon oxides, water and benzene) are released in the temperature range of 400–1000 °C, while the other important components (C1 and C2 hydrocarbons and hydrogen sulphide) are generated mainly under temperatures between 400 and 550 °C. Our results also show that only in some cases significant amount of hydrogen is generated.