Rapid Hydration Preparation of Calcium-Based Sorbent Made from Lime and Fly Ash

Abstract

A low-cost preparation process of rapidly hydrated sorbent was developed in a pilot-scale preparation system. The process hydrates the lime and the fly ash at ambient temperature for 2 h with drying at 150 °C for 1 h, a greatly reduced hydration temperature and preparation time. The rapidly hydrated sorbent was tested at a medium temperature of 350 °C in a thermogravimetric analyzer (TGA) and a pilot-scale circulating fluidized bed (CFB). The TGA results show that the calcium conversion ratio (ηCa) of the rapidly hydrated sorbent was ten times higher than that of the original lime and of a dry mixture of lime and fly ash. The ηCa in the CFB reactor was close to the TGA result, verifying the applicability of the rapidly hydrated sorbent in a real desulfurization process. The physical and chemical properties of the sorbent were analyzed to investigate the rapid hydration mechanism. The improved ηCa for the sorbent was mainly due to the greatly improved particle characteristics, including the particle specific surface area and the pore size. Highly active hydration products are not significantly produced at the ambient hydration temperature.