Thermogravimetric determination of thermal conductivity of lumpy limestones

Abstract

It is known that limestone from different origins decomposed at same kiln conditions produce either hard burnt or soft burnt lime. The reason was unknown. In the previous research, thermal conductivity is found to be one of the important thermal properties which determines the calcination behavior. In this research, lumpy limestone particles of various origins have been decomposed in the laboratory furnace. Cylindrical particles have been chosen in the size range between 14 mm to 33 mm. A hole is drilled at the center of each of the particle to insert the thermocouple. The particles are decomposed in the temperature range between 900 °C and 1200°C in a tube furnace. During the decomposition weight loss as well as the core temperature of the particles are measured and recorded simultaneously. The measured core temperature and the slope of the weight loss curves have been used as input to the model that is developed in addition to the kiln conditions. This shrinking core mathematical model developed can predict the thermal conductivity of lime obtained from various limestone. The experimental and modeling methods are described in this paper. To verify the results, thermal conductivity of few of these samples are measured using laser flash apparatus. The results obtained with these two different methods were very well matched. The thermal conductivity of lime measured using thermogravimetric decomposition method with lumpy limestone decomposition is representative of the limestones those are decomposed in the industrial kilns. The thermal conductivity of lime from various limestone were found to be in the range from 0.3 to 0.85 W/(mK).