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Silica-enhanced lime sorbents for flue gas desulfurization have been prepared by pozzolanic hydration of Ca(OH) 2 with excess SiO 2 . As the hydration proceeded, new particles grew in clearcut features with regular micropores, consisting of chainlike aggregates. The increase in the specific surface area of the product particles with hydration was closely related to the conversion to calcium silicate. Even after the completion of the pozzolanic reaction, self-hydration of excess SiO 2 continued to make the particles with more clear-cut features but prevent the Brunauer-Emmett-Teller (BET) surface area from further increasing. The mole ratio of Ca/Si in the calcium silicate prepared was independent of its initial mole ratio and converged to 0.9-1.5, depending on the hydration temperature. Pressure hydration at temperatures above 100 °C dramatically accelerated the reaction, resulting in a less compact structure composed of smaller primary particles with the ultimate BET surface area unchanged.

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