Characterization and behaviour of modified calcium-hydroxide-based sorbents in a dry desulfurization process

Abstract

Several calcium-hydroxide-based sorbents were prepared by mixing commercial Ca(OH)2 and a magnesic smectite using two lignosulfonates (LGSs) as additives, and their structural and desulfurant properties were studied. The sorbents were characterized using scanning electron microscopy (SEM) with an X-ray detector and N2 adsorption techniques. The dry desulfurization activity at a low temperature was investigated in laboratory-scale equipment. When LGSs are used in low amounts, their dispersant or deagglomerating properties observed by SEM produce an increase in the porosity and specific surface area (SSA) with respect to the sorbent prepared without LGSs. Their desulfurization activity increases up to 71% with respect to the solid prepared without additive, with the increase in the porosity and SSA values being the main factor to explain the higher SO2 retention values but also their hygroscopic properties. The composition of the spent sorbents allows to use them as soil amendment. The use of these LGSs in the preparation of calcium-based sorbents is an excellent and easy way to improve their desulfurant behavior, with an easy preparation at ambient temperature, and it is also another promising option to valorize this lignocellulosic waste.