Revisiting the dissolution kinetics of limestone – experimental analysis and modeling

BACKGROUNDStricter SO2 emission regulations for power plants and maritime transport encourage a better understanding of the phenomena involved in wet flue gas desulfurization (WFGD) where limestone dissolution is regarded as one of the rate determining steps.RESULTSThe dissolution kinetics of two limestone samples was studied in the industrially most relevant pH range 2.4–6. Dissolution experiments were performed under a regime where mechanical stirring did not affect the dissolution rate significantly. Furthermore, a mathematical model was developed by coupling mass transfer and chemical reaction at the surface over the whole range of pH; an analogy of the well-known Langmuir isotherm was applied. The results show that it is possible to accurately model the whole pH range, with a 99.1–99.5% degree of explanation and low relative standard errors ≤2%.CONCLUSIONLimestone dissolution was successfully modeled by implementing surface areas measured by physisorption which were also compared with particle size distribution (PSD) measurements. Selected liquid-phase concentrations were measured by means of inductively coupled plasma optical emission spectrometry (ICP-OES) in order to support the proposed mechanism. The samples were characterized by X-ray fluorescence (XRF), X-ray spectroscopy (EDX) and scanning electron microscopy (SEM). A wide range of studies presented in the literature are also described.