| Summary: | 碩士 === 國立臺灣大學 === 化學工程學研究所 === 90 === Abstract
A differential fixed-bed reactor was employed to study the effects of additives on the reaction between limestone and SO2 under the conditions similar to those in the bag filters of the spray-drying flue gas desulfurization system. Limestone was from Her-Ping, Hualien. Samples of different specific surface areas were prepared by wet grinding. Additives used were deliquescent salts, NaOH, Na2CO3, K2CO3, LiCl, NaCl, KCl, CaCl2, NaNO2, NaNO3, Na2SO3, and Na2SO4. A salt (1 to 10mol%) as added to limestone by slurrying and drying processes.
All the salts enhanced the reaction of limestone with SO2 because the salts adsorbed more water. The initial reaction rate and one hour conversion of limestone with a salt added increased as relative humidity or the amount of the salt increased. At 60℃, 70%RH, 1000ppmSO2, and 1h, the ranking of the effect of salt on the conversion of limestone with 5mol% salt added was CaCl2＞KCl＞NaCl＞NaNO3＞LiCl＞Na2CO3＞NaOH＞K2CO3＞Na2SO4＞NaNO2＞Na2SO3；at the reaction conditions, the conversion of limestone with a salt added was higher than that of CaCO3 or Ca(OH)2 without the salt added.
For limestone with CaCl2 added, the reaction rate increased with SO2 concentration at high relative humidity, but the effects of temperature and the initial BET surface area of limestone were absent. The reaction products of limestone with CaCl2 added were found to be CaSO3．1/2H2O and CaSO4．2H2O under the presence of NOx and O2 in the gas mixture, and CaSO3．1/2H2O without the presence of NOx and O2.
Limestone added with proper deliquescent salts can replace Ca(OH)2 as a sorbent for the dry or semidry flue gas desulfurization processes.
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