Understanding sulfation effect on the kinetics of carbonation reaction in calcium looping for CO2 capture

Calcium looping is an acknowledged technology in capturing CO2 from the flue gas of fossil fuel power plants with potentially low costs and high efficiency. However, SO2 in the flue gas will cause an inevitable side reaction of sulfation during the carbonation process, which not only reduces the sorption performance but could significantly change the carbonation kinetics. In the work, sorbents with/without the presence of sulfation in the carbonation process were prepared and characterized, and the effect of sulfation on kinetic characteristics of cyclic carbonation in calcium looping was studied. Furthermore, the apparent kinetic model and 3-D diffusion model were adopted to analyze the kinetics of fast and slow carbonation reaction stages in the multiple calcination/carbonation cycles. Results show that carbonation rate constant becomes smaller as increasing the number of cycles, which however leads to a rising trend of the activation energy in the chemical reactioncontrolled stage and a slight reduction of the value in the diffusion-controlled carbonation. Moreover, the presence of CaSO4 in sorbents as a result of partial sulfation leads to smaller reaction rate constants and higher activation energies.