Effects of the Limestone Particle Size on the Sulfation Reactivity at Low SO(2) Concentrations Using a LC-TGA

Limestone particle size has a crucial influence on SO(2) capture efficiency, however there are few studies on the sulfation reactivity, which covers a broad range of particle sizes at low SO(2) concentrations. In this paper, a large-capacity thermogravimetric analyzer (LC-TGA) was developed to obtain the sulfur removal reaction rate under a wide range of particle sizes (3 μm–600 μm) and SO(2) concentrations (250 ppm–2000 ppm), and then compared with the results of a traditional fixed bed reactor and a commercial TGA. The experimental results showed that the LC-TGA can well eliminate the external mass transfer and obtain a better measurement performance. Both the final conversion and the reaction rate reduced with the decreasing of SO(2) concentration, but ultrafine limestone particles still showed the good sulfation reactivity even at 250 ppm SO(2). An empirical sulfation model was established based on the experimental results, which can well predict the sulfation process of different limestone particle sizes at low SO(2) concentrations. The model parameters have a strong negative correlation against the particle size, and the fit of the reaction order of SO(2) was found to be about 0.6. The model form is very simple to incorporate it into available fluidized bed combustion models to predict SO(2) emission.