Limestone-based dual-loop wet flue gas desulfurization under oxygen-enriched combustion

Abstract

Oxygen-enriched combustion is the most promising CO2 emission reduction technology for coal burning. However, the sharp increase in CO2 and SO2 concentrations in flue gas after oxygen-enriched combustion poses a new challenge to the subsequent wet flue gas desulfurization (WFGD) system. In this study, limestone-based dual-loop WFGD technology was used to solve this problem. Using a small dual-loop falling-film WFGD experimental system, the effect of CO2 concentration on limestone dissolution, SO2 absorption, SIV oxidation, and CaSO4 crystallization during limestone-based dual-loop WFGD was investigated in detail and compared with single-loop WFGD. The results show that, although an increase in CO2 concentration is beneficial to SO2 absorption in the single-loop WFGD system, it is not conducive to limestone dissolution, SIV oxidation, and CaSO4 crystallization. Compared with single-loop WFGD, in the low pH region of dual-loop WFGD, increasing the CO2 concentration can also improve the SO2 absorption efficiency. However, it had no obvious effect on limestone dissolution, SIV oxidation, and CaSO4 crystallization. In the high pH region of the dual-loop WFGD, although an increase in CO2 concentration is not conducive to SO2 absorption, the SO2 absorption efficiency is still higher than that of single-loop WFGD. The negative effect of increasing the CO2 concentration on limestone dissolution, SIV oxidation, and CaSO4 crystallization can be effectively solved by introducing slurry from the high pH region into the low pH region. Therefore, compared with single-loop WFGD technology, dual-loop WFGD is more suitable for flue gas desulfurization after oxygen-enriched combustion.