Mercury capture by nano-structured titanium dioxide sorbent during coal combustion: Lab-scale to pilot-scale studies

Abstract

The performance of non-carbon based sorbent, titanium dioxide (TiO 2) used with UV irradiation, was evaluated in a laboratory-scale coal combustor and in a slip-stream drawn from a pilot-scale coal combustor. For the laboratory-scale system, mercury capture efficiency peaked at 94% at a sorbent feed rate of 71 mg/m3, with sorbent to coal ratio of 0.0074. For the slip-stream system, mercury capture efficiency achieved 92% at a sorbent feed rate of 622 mg/m3, with sorbent to coal ratio of 0.015. The required sorbent feed rates for both systems were higher than those kinetically estimated from earlier established lab-scale study, indicating the interference of other species in coal combustion flue gas. The sorbent generation technique and injection location significantly affected the physical and chemical properties of the sorbent, and subsequently its performance. Pure anatase generated via a pre-synthesized technique was found to be more effective than a mixture of anatase and rutile crystalline structure generated via in-situ generation and found in commercial TiO2 (Degussa, P25). This study further revealed that the injection of nano-structured sorbent can be designed to obtain optimal efficiency of capture. © Taiwan Association for Aerosol Research.