Simultaneous magnesia regeneration and sulfur dioxide generation in magnesium-based flue gas desulfurization process

Abstract

A method was proposed for simultaneously regenerating magnesia from the Mg-based flue gas desulfurization byproducts in the power plant and generating the high concentration of sulfur dioxide. Elemental sulfur particles were evaporated to sulfur vapor and the latter one was used as the reductive agent to regenerate magnesia from the magnesium gypsum. The experiments were carried out in a successive fixed-bed system to study the concentration of sulfur dioxide in the exhaust gas and the activity of the regenerated magnesia under different reaction conditions. Sulfur vapor effectively reduced the magnesia regeneration temperature from above 950 °C to merely 650 °C. The concentration of sulfur dioxide in the exhaust gas could achieve 20% by volume when the sulfur vapor partial pressure was 1674 Pa, the regeneration temperature was 750 °C, the gas hourly space velocity was 1200 h−1 and the loading of the reaction materials in the regeneration reactor was 16 g, respectively. The activity of the regenerated magnesia after the decomposition of the magnesium gypsum at 750 °C was satisfactory. Both the magnesium gypsum and the regenerated magnesia were characterized using X-ray fluorescence spectroscopy, thermogravimetric analyzer, X-ray diffraction spectroscopy, BET surface area analyzer, scanning electron microscopy, high resolution transmission electron microscopy, and X-ray photoelectron spectroscopy. The kinetics of the magnesia regeneration from the magnesium gypsum in the presence of the sulfur vapor was analyzed and the nucleation model was determined to be the most appropriate kinetic model. The activation energy and the pre-exponential factor were determined to be 76.51 kJ/mol and 228.66 min−1, respectively. All the results demonstrate that there is considerable potential for the application of this proposed method in flue gas desulfurization process.