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Limestone dissolution is a very important factor in flue gas desulfurization systems because it determines its reactivity toward SO 2 . Fly ash, a siliceous material, has been reported to improve sorbent reactivity. This study investigates the effect of adding fly ash to limestone on its dissolution rate constant. The experiments were carried out using a pH stat apparatus where the effects of the reaction variables, fly ash/limestone ratio, slurry pH, reaction temperature, and concentration of acid, used were investigated. The central composite design (CCD) of the experiment was used to develop a model that correlates the dissolution rate constant and the reaction variables. It was found that fly ash had a positive effect on the dissolution rate constant of limestone, with the pH having the most significant effect. The dissolution rate constant was found to increase with an increase in the temperature and acid concentration. X-ray diffraction (XRD) analysis showed products of hydration formed, which are mainly calcium silicate hydrates, on the samples. This led to an increase in the specific surface area, as observed in the Brunauer− Emmett−Teller (BET) analysis.

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Pectin was extracted from dried lemon peels using acid hydrolysis. Five process variables/factors were chosen for investigation; the extraction temperature, extraction time, pH, size of the peels and the peel to water mass ratio. Three response variables were monitored; the Yield (% Yield), Degree of Esterification (% DE) and Galacturonic Acid content (% GA). A duplicated 25 factorial design was conducted on dried peels. The extraction temperature, time, pH and size of the peel were found to be the most significant variables affecting the pectin yield. The most significant variable affecting the % GA was found to be the extraction time and the % DE was most significantly affected by the pH as well as the extraction temperature. A duplicated 24 design (peel size excluded as a process variable) on fresh wet peels was conducted in order to compare the results attained to those of dried peel extraction. Drying the peel therefore increased the greatest pectin yield attained, it had no drastic effect on the % GA, but it reduced the % DE of the pectin extract. A 24 design was also performed on wet peels that had been stored at atmospheric conditions for two days. The results were compared to those found from fresh wet peel extraction, in order to depict the need for drying the peel.