Development of Sorbents for SO2 Capture Prepared by Hydration of Fly Ash and Hydrated Lime in Seawater

Abstract

The influence of seawater salts on the physicochemical properties and desulfurization behavior of mixtures of fly ash and Ca(OH)2 hydrated in seawater at different initial ratios and hydration times was investigated. The Ca(OH)2 conversion as a measure of the pozzolanic reaction extent was determined. The properties characterized in the sorbents include BET surface area and porosity distribution, X-ray diffraction pattern, and SEM image. The composition of the silicates synthesized in the reaction between fly ash and hydrated lime was obtained by atomic absorption spectrometry. The sorbents were tested in a flue gas desulfurization reaction at 57 °C. The seawater salts do not increase the formation of calcium silicates, but the sorbents obtained in the presence of these salts exhibit higher specific surface areas and better desulfurization behavior than sorbents hydrated in distillate water. The ability of the sea salts, present in the sorbent, to capture moisture from the flue gas, promoted by the higher specific surface area of the sorbents prepared in seawater, can explain the increase in SO2 retention. The use of seawater as a hydration medium to prepare desulfurant sorbents is an inexpensive means of supplying these types of additives for coastal power stations.