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

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, S-IV 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 ab-sorption in the single-loop WFGD system, it is not conducive to limestone dissolution, S-IV 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, S-IV 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, S-IV 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.