Structural Properties and Reactivities of Ca(OH)₂/Fly Ash Sorbents for Flue Gas Desulfurization

Abstract

Ca(OH) 2 /fly ash sorbents were characterized and tested for reactivity toward SO 2 at conditions similar to those in the bag filters in the dry and semidry flue gas desulfurization processes. The sorbents were mesoporous, and their specific surface areas linearly correlated with their specific total pore (1.7-300 nm) or mesopore (2-50 nm) volumes. The 1 h utilization of Ca in a sorbent increased, in general, with increasing fly ash content. Sorbents with Ca(OH) 2 contents larger than 33 wt % had higher weights of SO 2 captured per unit weight of sorbent than Ca(OH) 2 had alone, and the sorbent with 70 wt % Ca(OH) 2 had the maximum capture. The 1 h utilizations of Ca for the sorbents and Ca(OH) 2 increased almost linearly with increasing specific surface area or pore volumes of the sorbent. The SO 2 captured per unit surface area or pore volume of the sorbent decreased almost linearly with smaller Ca(OH) 2 content. The reactivities of the sorbents were enhanced mainly by their large specific surface areas and to a lesser degree by the reactive constituents in fly ash.

Oil Palm Ash/Ca(OH)2/CaSO4 Absorbent for Flue Gas Desulfurization

“…The structural properties of the absorbent, particularly the specific surface area, are believed to play an important role in SO 2 capture. Some studies have shown that higher desulfurization activity correlates with higher absorbent specific surface area [6,8].…”

Preparation of a new sorbent with hydrated lime and blast furnace slag for phosphorus removal from aqueous solution

“…Table 2 summarizes the specific surface areas of sorbents. It was found that nearly all of the BFS-HL sorbents have larger surface areas than their raw materials of HL and BFS, probably due to pozzolanic reactions [23]. In general, pozzolanic reactions start with the chemical adsorption of calcium hydroxide on the surface of silanol groups [24].…”

Fabrication of Multifunctional Hybrid Composites Using Fly Ash to Control Environmental Pollutants: A Review

“…From the above results, it can be concluded that the ability of FA to capture SO2 is mainly related to its surface area, pore structures and calcium ion content. Specific surface area is increased after the FA is hydrated, leading to more calcium ions that can react with SO2 to produce CaSO4 [149,150].…”