Desulfurization kinetics of coal combustion gases

Abstract

Desulfurization of the gases from coal combustion was studied, using limestone (marble) as the sorbent in a fluidized-bed reactor. The kinetic parameter, k, was measured by analyzing the reduction in SO2 emissions in relation to time when a batch of limestone was introduced directly into the combustor chamber. The influence of sorbent composition and particle size was also studied. The CaO content in the limestone was more important than the MgO content. Sorbent particle size showed a strong influence on the reaction time and efficiency of desulfurization. The results of this work prove that marble type is very important in the choice of sorbent for a desulfurization process. A magnesian limestone showed a better performance than a dolomite. Therefore, the magnesian limestone is more efficient for a shorter particle residence time, which is characteristic of the bubbling fluidized bed

FBC desulfurization process using coal with low sulfur content, high oxidizing conditions and metamorphic limestones

“…The higher surface area for reaction of the 0.32 mm dolomite, as a consequence of the finer particle size, was the most important factor that determined the better performance of this dolomite at this particle size. This behavior is in accordance with the results reported by Bragança et al (2003). In this study, a higher exposed surface area for reaction was considered to be the main parameter for the dolomite.…”

“…The lower retention for the finer dolomite is accounted for by the excessive elutriation occurring at this particle size, which is a potential limitation for the investigation of finer sorbents. This was also according to previous investigation (Bragança et al, 2003).…”

“…By using scanning electron microscope, the two limestones showed similar porosity after calcination (Moraes, 1998). The importance of CaO concentration in the bed, independent of the MgO concentration, was shown in a study of the kinetics of the desulfurization process (Bragança et al, 2003).…”

Evaluation of Limestone Impurities in the Desulfurization Process of Coal Combustion Gas

“…Both limestones reached ~70% of desulfurization efficiency. Other results of the limestones from southern Brazil used in desulfurization on bench and pilot scale can be found in the works of one of the authors (Bragança, 2003(Bragança, , 2009Sebag, 2001). The main disadvantage of the use of limestone Do is the smallest amount of calcium oxide (Table 2).…”

Dolomite Desulfurization Behavior in a Bubbling Fluidized Bed Pilot Plant for High Ash Coal

“…For temperatures of 850 °C and below, the reaction occurred with two mechanisms due to pore plugging and changes in the chemical composition of the solid. Bragança et al (2003) studied the influence of limestone characteristics to determine the kinetic parameters of desulphurization using a batch fluidized bed reactor. Anthony and Granadstein (2001) investigated the fragmentation of sorbent particles.…”