Limestone dissolution study for wet flue gas desulfurization under turbulent regimes above critical suspension speed

Anthropogenic sulfur dioxide (SO2) is principally the product of energy conversion through combustion of fossil fuel sources. This pollutant causes acidic rain and can also be harmful for human health. Many means for controlling sulfur dioxide emission are available in the market and have been extensively applied. Among these techniques, wet flue gas desulfurization is one of the most widely used methods because of its reliability and high efficiency. Nonetheless, high energy and water consumption are among its principal drawbacks. Limestone dissolution has been accounted as one of the main controlling steps of the process (Pepe, 2001). Even though limestone is dissolved in acidic media in many industrial processes worldwide, no commonly accepted mathematical models exist for the dissolution kinetics at the moment. The reasons for the contradictory results in literature dwell, at least to considerable extent, from the varying influence of mass transfer limitations and the influence of CO2 on the pH. Experimental equipment and a methodology for evaluating the kinetic regime of a high grade limestone commercially used for desulfurization was developed in the current study. The results show that the kinetic regime, necessary to properly characterize the dissolution rate, can be reached even with small particle size and high temperatures with the help of severe agitation to overcome solid-liquid mass transfer and powerful purging to minimize the influence of carbonic acid on the pH. The method can be directly applied for investigating and comparing the reactivities of various limestone samples for industrial purposes.