(382ah) Modeling of Wet Flue Gas Desulfurization Process for Merchantable Gypsum Production Using Low Grade Limestone

This study focuses on the simulation of wet flue gas desulfurization facilities for improving the production of gypsum by using low-grade limestone. At present, high-grade limestone with CaCO₃ content of 94% is used for producing merchantable gypsum with a purity 93%. Because of depletion of its resources, low grade limestone need to be used. Low grade limestone contains many other materials which reduce the purity of gypsum, such as MgCO₃, Al₂O₃, SiO₂. Because of these impurities, the quality of gypsum is not satisfied. Low grade lime stone has to be blended in high grade lime stone to produce merchantable gypsum. In process modeling, a lot of reactions are considered to develop model. These reactions are divided into three steps. First, the limestone dissolution is simulated by the RSTOIC model. Second, SO_x absorption and crystallization is used by the RCSTR model. Finally the gypsum is separated by using the SEPERATORS model. Modeling steps makes it easy to reflect further side reactions and physical disturbances. In optimization condition, constraints are set to 93% purity of gypsum, 94% desulfurization efficiency, and total use of limestone at 3710 kg/hr. Under these constraints, the mass flow of low grade lime stone was maximized as an objective function. As a result, the maximum blending quantity of low-grade limestone for 2,216 kg of high-grade limestone that satisfies the constraints is about 1,495 kg. Since the price of low-grade limestone is half that of high-grade limestone, the total cost of feed can be reduced by $110,671 per year compared to the initial cost.