Simultaneous hydration/carbonation of FBC ash by low-frequency sonication

Abstract

Simultaneous hydration and carbonation of ash from fluidized bed combustion was studied using a new sonication technology. Enhanced carbonation of the ash by CO 2 was achieved at ambient temperature by use of a sonic generator with low frequency (100–500 Hz). At lower sonic intensity, the product was mainly Ca(OH) 2 whereas at higher intensity the product was primarily CaCO 3. Results of a simulation, assuming that the CaCO 3 is formed from Ca(OH) 2, described the observed time dependence for Ca(OH) 2 and CaCO 3 conversion well. The hydrated/carbonated ash was tested as sulphur sorbent and the sulphation activity of the ash increased with increasing CaCO 3 content. This result can be attributed to the larger molar volume of CaCO 3 compared to that of Ca(OH) 2, which resulted in larger porosity and specific surface area of the particles upon thermal decomposition.