Thermal decomposition of the CaO in traditional lime kilns. Applications in cultural heritage conservation

Abstract

It has been the aim of this paper to know the factors that most affect to the process of obtaining the quicklime in traditional lime kilns. To this end, a comparative study has been carried out between two quicklime types, one obtained in traditional lime kiln and another obtained in an industrial lime kiln. On the other hand, two limestone types, commonly used in the production of lime in these kilns, have been calcination in the laboratory. They correspond to an oosparite and oomicritic limestones, traditionally used in the elaboration of limes in the Morón de la Frontera region, Seville (Spain). The samples have been analyzed from the chemical, physical and mineralogical points of view. The calcination process of the limestones and the optimum heating temperature depends of the porosity and crystalline structure original of the limestones. The calcination temperatures, longer residence time and CO2 and steam pressure in the kilns affects the size and porosity of the CaO crystals. The quicklimes with greater volume of pores allow faster access of water to the interior of the material and consequently the lime slaking reaction is less exothermic. The size of the particles CaO affects the rate of the lime slaking reaction, accelerating the reaction when the particles are smaller. The quicklimes calcined in traditional kilns are characterized by greater particle and pore size and greater volume of mesopores.