THE USE OF A CIRCULATING FLUIDIZED-BED ABSORBER FOR THE CONTROL OF SULFUR-DIOXIDE EMISSIONS BY CALCIUM-OXIDE SORBENT VIA IN-SITU HYDRATION

A circulating fluidized bed absorber (CFBA) was developed and evaluated for sulfur dioxide removal from flue gas by use of CaO sorbent at humid conditions. SO2 removal in this process strongly depends on the system approach to saturation temperature, which increases with an increase of the approach to saturation temperature (smaller Delta T). The operability of the CFBA by use of very large CaO particles (initial size > 1800 mu m) indicates substantial cost savings for application to full scale systems. A CFBA reactor model based on the assumption of a turbulent fluidization region, was developed for system analysis and SO2 removal data analysis. The model coupled a particle population model for calculation of the bed particle size distribution, and the shrinking core model for the chemical reaction. The particle size distribution calculated by the particle population model showed a reasonable trend for the size reduction. The reaction rate constant, k(s), was found to be a function of the system approach to saturation temperature; the value of k(s) increases exponentially with an increase of the approach to saturation temperature. This model, with some modifications could be successfully used in the prediction of SO2 removal efficiency with knowledge of operating variables in the CFBA process, such as the sorbent feed rate, particle elutriation rate, solids recycle rate, and the bed weight at steady-state operation.