Desulfurization of Flue Gases Using Materials Based on Ca(OH)2 Supported on Clays

Abstract

Aim: The aim of the present work is to develop alternative materials for the flue gas desulfurization process starting from local low-cost raw material in order to reduce the operating cost in a power plant. For this reason, bentonite and tonsil were used as a support, and Ca(OH)2 as active phase since they are abundant in Mexico. Study Design:  Materials were prepared by two different methods and with three different mass ratio Ca: clay. After preparation, materials were tested at three different temperatures in a thermogravimetric balance. Place and Duration of Study: Samples were prepared at the Universidad Autónoma del Estado de Morelos, and thermogravimetric analysis was made at the Instituto Nacional de Electricidad y Energías Limpias. Methodology: Materials were prepared with slurries of different Ca: clay mass ratio (1:2, 1:1, and 2:1) using mechanical stirring or applying ultrasonic energy during mixing. To quantify the real calcium content, samples were dissolved and analysed by Atomic Absorption Spectroscopy. Materials were tested at 350, 400, and 450°C in a thermogravimetric balance to determine their sorption capacity. The process was modelled using a modified shrinking core approach, and kinetic parameters were estimated. Results: It was found that activity increased proportionally to the Ca load and temperature. Clays did not play a significant role; at low heat, an action was slightly better in materials supported on tonsil, but at higher temperatures, elements supported on bentonite had better activity. Ultrasonic energy did not improve the performance of sorbent materials. The modified shrinking core model adequately fit the experimental data. Conclusions: Sorbent materials prepared in this study were able to retain SO2 at the studied temperatures, and are an economical alternative for the flue gas desulfurization process. Ca load was the most relevant parameter for the physical activity.