Preliminary studies to recycling gypsum with solar thermal energy

Twenty-Eighth International Conference on Solid Waste Technology and Management. Filadelfia, PA, USANatural gypsum is a rock composed principally of CaSO4•2H2O, along with clays, sand, and salts. It is one of the most widely materials in the world, in building, ceramics, agriculture, etc. Spain is the third largest world producer, and the leader in production and consumption in Europe. For building, gypsum is obtained by calcination of natural rocks at different temperatures according to uses. Power consumption is the major cost of this process, and if the energy comes from fossil fuels the environmental cost is high. Thus, the objective of this work is to study the technological viability of the use a clean, non-contaminating and free power source as solar thermal energy for the calcination of gypsum. A Fresnel lens (Ø=889mm, thickness=3.17mm, focal distance=757 mm) was used as a light beams concentrator. To study the influence of the grain size in the transformation of dyhidrated phase into bassanite and anhydrite, rock was crushed at different particle sizes. Tests were performed at different times (1-10min). XRD results showed the complete dehydration of gypsum into anhydrite (~92%) and bassanite (~12%) for medium and fine fractions for only 5 min exposition.N