Characterization and Behavior 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 N 2 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 SO 2 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.

Semidry Desulfurization Process with In Situ Supported Sorbent Preparation

“…Numerous studies have attempted to improve sorbent utilization for semidry FGD processes. − Most of these studies focus on enhancing sorbent activity using a hydration mixture of lime and Si-containing waste, such as fly ash, rice husk ash, and clay. − The Si-containing waste reacts with lime in the presence of water, which is known as a pozzolanic reaction. High sorbent reactivity mainly results from the large specific surface area of these pozzolanic reaction products .…”

Experimental Study on In Situ Preparation of Supported Sorbent for Moderate Temperature CFB-FGD

“…Dry FGD processes have the advantages of less capital costs and significantly less water consumption. − The reaction between the absorbent and SO 2 is conducted on the particle surface and particle pores, with no water participating in the process. The overall reaction rate is significantly lower than the wet FGD, which leads to low absorbent utilization.…”